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    Directly probing the mechanical properties of the spindle and its matrix. Gatlin Jesse C,Matov Alexandre,Danuser Gaudenz,Mitchison Timothy J,Salmon Edward D The Journal of cell biology Several recent models for spindle length regulation propose an elastic pole to pole spindle matrix that is sufficiently strong to bear or antagonize forces generated by microtubules and microtubule motors. We tested this hypothesis using microneedles to skewer metaphase spindles in Xenopus laevis egg extracts. Microneedle tips inserted into a spindle just outside the metaphase plate resulted in spindle movement along the interpolar axis at a velocity slightly slower than microtubule poleward flux, bringing the nearest pole toward the needle. Spindle velocity decreased near the pole, which often split apart slowly, eventually letting the spindle move completely off the needle. When two needles were inserted on either side of the metaphase plate and rapidly moved apart, there was minimal spindle deformation until they reached the poles. In contrast, needle separation in the equatorial direction rapidly increased spindle width as constant length spindle fibers pulled the poles together. These observations indicate that an isotropic spindle matrix does not make a significant mechanical contribution to metaphase spindle length determination. 10.1083/jcb.200907110
    Nanopatch-targeted skin vaccination against West Nile Virus and Chikungunya virus in mice. Prow Tarl W,Chen Xianfeng,Prow Natalie A,Fernando Germain J P,Tan Cindy S E,Raphael Anthony P,Chang David,Ruutu Merja P,Jenkins Derek W K,Pyke Alyssa,Crichton Michael L,Raphaelli Kristin,Goh Lucas Y H,Frazer Ian H,Roberts Michael S,Gardner Joy,Khromykh Alexander A,Suhrbier Andreas,Hall Roy A,Kendall Mark A F Small (Weinheim an der Bergstrasse, Germany) The 'Nanopatch' (NP) comprises arrays of densely packed projections with a defined geometry and distribution designed to physically target vaccines directly to thousands of epidermal and dermal antigen presenting cells (APCs). These miniaturized arrays are two orders of magnitude smaller than standard needles-which deliver most vaccines-and are also much smaller than current microneedle arrays. The NP is dry-coated with antigen, adjuvant, and/or DNA payloads. After the NP was pressed onto mouse skin, a protein payload co-localized with 91.4 + or - 4.1 APC mm(-2) (or 2925 in total) representing 52% of the delivery sites within the NP contact area, agreeing well with a probability-based model used to guide the device design; it then substantially increases as the antigen diffuses in the skin to many more cells. APC co-localizing with protein payloads rapidly disappears from the application area, suggesting APC migration. The NP also delivers DNA payloads leading to cutaneous expression of encoded proteins within 24 h. The efficiency of NP immunization is demonstrated using an inactivated whole chikungunya virus vaccine and a DNA-delivered attenuated West Nile virus vaccine. The NP thus offers a needle-free, versatile, highly effective vaccine delivery system that is potentially inexpensive and simple to use. 10.1002/smll.201000331
    Silencing of reporter gene expression in skin using siRNAs and expression of plasmid DNA delivered by a soluble protrusion array device (PAD). Gonzalez-Gonzalez Emilio,Speaker Tycho J,Hickerson Robyn P,Spitler Ryan,Flores Manuel A,Leake Devin,Contag Christopher H,Kaspar Roger L Molecular therapy : the journal of the American Society of Gene Therapy Despite rapid progress in the development of potent and selective small interfering RNA (siRNA) agents for skin disorders, translation to the clinic has been hampered by the lack of effective, patient-friendly delivery technologies. The stratum corneum poses a formidable barrier to efficient delivery of large and/or charged macromolecules including siRNAs. Intradermal siRNA injection results in effective knockdown of targeted gene expression but is painful and the effects are localized to the injection site. The use of microneedle arrays represents a less painful delivery method and may have utility for the delivery of nucleic acids, including siRNAs. For this purpose, we developed a loadable, dissolvable protrusion array device (PAD) that allows skin barrier penetration. The PAD tips dissolve upon insertion, forming a gel-like plug that releases functional cargo. PAD-mediated delivery of siRNA (modified for enhanced stability and cellular uptake) resulted in effective silencing of reporter gene expression in a transgenic reporter mouse model. PAD delivery of luciferase reporter plasmids resulted in expression in cells of the ear, back, and footpad skin as assayed by intravital bioluminescence imaging. These results support the use of PADs for delivery of functional nucleic acids to cells in the skin with an efficiency that may support clinical translation. 10.1038/mt.2010.126
    Dose sparing enabled by skin immunization with influenza virus-like particle vaccine using microneedles. Quan Fu-Shi,Kim Yeu-Chun,Compans Richard W,Prausnitz Mark R,Kang Sang-Moo Journal of controlled release : official journal of the Controlled Release Society To address the limitations of conventional influenza vaccine manufacturing and delivery, this study investigated administration of virus-like particle (VLP) influenza vaccine using a microneedle patch. The goal was to determine if skin immunization with influenza VLP vaccine using microneedles enables dose sparing. We found that low-dose influenza (A/PR/8/34 H1N1) VLP vaccination using microneedles was more immunogenic than low-dose intramuscular (IM) vaccination and similarly immunogenic as high-dose IM vaccination in a mouse model. With a 1μg dose of vaccine, both routes showed similar immune responses and protective efficacy, with microneedle vaccination being more effective in inducing recall antibody responses in lungs and antibody secreting cells in bone marrow. With a low dose of vaccine (0.3μg), microneedle vaccination induced significantly superior protective immunity, which included binding and functional antibodies as well as complete protection against a high dose lethal infection with A/PR/8/34 virus, whereas IM immunization provided only partial (40%) protection. Therefore, this study demonstrates that microneedle vaccination in the skin confers more effective protective immunity at a lower dose, thus providing vaccine dose-sparing effects. 10.1016/j.jconrel.2010.07.125
    Formulation and coating of microneedles with inactivated influenza virus to improve vaccine stability and immunogenicity. Kim Yeu-Chun,Quan Fu-Shi,Compans Richard W,Kang Sang-Moo,Prausnitz Mark R Journal of controlled release : official journal of the Controlled Release Society Microneedle patches coated with solid-state influenza vaccine have been developed to improve vaccine efficacy and patient coverage. However, dip coating microneedles with influenza vaccine can reduce antigen activity. In this study, we sought to determine the experimental factors and mechanistic pathways by which inactivated influenza vaccine can lose activity, as well as develop and assess improved microneedle coating formulations that protect the antigen from activity loss. After coating microneedles using a standard vaccine formulation, the stability of influenza vaccine was reduced to just 2%, as measured by hemagglutination activity. The presence of carboxymethylcellulose, which was added to increase viscosity of the coating formulation, was shown to contribute to vaccine activity loss. After screening a panel of candidate stabilizers, the addition of trehalose to the coating formulation was found to protect the antigen and retain 48-82% antigen activity for all three major strains of seasonal influenza: H1N1, H3N2 and B. Influenza vaccine coated in this way also exhibited thermal stability, such that activity loss was independent of temperature over the range of 4-37 degrees C for 24h. Dynamic light scattering measurements showed that antigen activity loss was associated with virus particle aggregation, and that stabilization using trehalose largely blocked this aggregation. Finally, microneedles using an optimized vaccine coating formulation were applied to the skin to vaccinate mice. Microneedle vaccination induced robust systemic and functional antibodies and provided complete protection against lethal challenge infection similar to conventional intramuscular injection. Overall, these results show that antigen activity loss during microneedle coating can be largely prevented through optimized formulation and that stabilized microneedle patches can be used for effective vaccination. 10.1016/j.jconrel.2009.10.013
    Drawing lithography: three-dimensional fabrication of an ultrahigh-aspect-ratio microneedle. Lee Kwang,Lee Hyun Chul,Lee Dae-Sik,Jung Hyungil Advanced materials (Deerfield Beach, Fla.) 10.1002/adma.200902418
    Microneedle-based drug delivery systems: microfabrication, drug delivery, and safety. Donnelly Ryan F,Raj Singh Thakur Raghu,Woolfson A David Drug delivery Many promising therapeutic agents are limited by their inability to reach the systemic circulation, due to the excellent barrier properties of biological membranes, such as the stratum corneum (SC) of the skin or the sclera/cornea of the eye and others. The outermost layer of the skin, the SC, is the principal barrier to topically-applied medications. The intact SC thus provides the main barrier to exogenous substances, including drugs. Only drugs with very specific physicochemical properties (molecular weight < 500 Da, adequate lipophilicity, and low melting point) can be successfully administered transdermally. Transdermal delivery of hydrophilic drugs and macromolecular agents of interest, including peptides, DNA, and small interfering RNA is problematic. Therefore, facilitation of drug penetration through the SC may involve by-pass or reversible disruption of SC molecular architecture. Microneedles (MNs), when used to puncture skin, will by-pass the SC and create transient aqueous transport pathways of micron dimensions and enhance the transdermal permeability. These micropores are orders of magnitude larger than molecular dimensions, and, therefore, should readily permit the transport of hydrophilic macromolecules. Various strategies have been employed by many research groups and pharmaceutical companies worldwide, for the fabrication of MNs. This review details various types of MNs, fabrication methods and, importantly, investigations of clinical safety of MN. 10.3109/10717541003667798
    Transdermal delivery of naltrexol and skin permeability lifetime after microneedle treatment in hairless guinea pigs. Banks Stan L,Pinninti Raghotham R,Gill Harvinder S,Paudel Kalpana S,Crooks Peter A,Brogden Nicole K,Prausnitz Mark R,Stinchcomb Audra L Journal of pharmaceutical sciences Controlled-release delivery of 6-beta-naltrexol (NTXOL), the major active metabolite of naltrexone, via a transdermal patch is desirable for treatment of alcoholism. Unfortunately, NTXOL does not diffuse across skin at a therapeutic rate. Therefore, the focus of this study was to evaluate microneedle (MN) skin permeation enhancement of NTXOL's hydrochloride salt in hairless guinea pigs. Specifically, these studies were designed to determine the lifetime of MN-created aqueous pore pathways. MN pore lifetime was estimated by pharmacokinetic evaluation, transepidermal water loss (TEWL) and visualization of MN-treated skin pore diameters using light microscopy. A 3.6-fold enhancement in steady-state plasma concentration was observed in vivo with MN treated skin with NTXOL.HCl, as compared to NTXOL base. TEWL measurements and microscopic evaluation of stained MN-treated guinea pig skin indicated the presence of pores, suggesting a feasible nonlipid bilayer pathway for enhanced transdermal delivery. Overall, MN-assisted transdermal delivery appears viable for at least 48 h after MN-application. 10.1002/jps.22083
    In vitro permeation of a pegylated naltrexone prodrug across microneedle-treated skin. Milewski Mikolaj,Yerramreddy Thirupathi Reddy,Ghosh Priyanka,Crooks Peter A,Stinchcomb Audra L Journal of controlled release : official journal of the Controlled Release Society Microneedles (MN) are a useful tool for increasing skin permeability to xenobiotics. Previous research showed marked improvement in the percutaneous flux of naltrexone (NTX) hydrochloride by the use of MN skin pretreatment alone; however, for better therapeutic effect, further enhancement is desired. The goal of this in vitro study was to combine microneedle skin pretreatment with the use of a highly water-soluble PEGylated naltrexone prodrug (polyethyleneglycol-NTX, PEG-NTX) to investigate its transdermal transport at varying concentrations. Solubility and stability of the prodrug were investigated. In vitro diffusion experiments employing MN-treated minipig skin were used to evaluate the performance of the PEGylated prodrug. The results revealed substantial deviation from ideal behavior, with the flux through MN-treated skin having a nonlinear relationship to the prodrug concentration in the donor solution. While in the lower concentration range tested the prodrug flux increase was proportional to the concentration increase, at high concentrations it showed no such dependence. Accounting for the decrease in the effective prodrug diffusivity accompanying the increase in viscosity, as predicted by the Stokes-Einstein equation, provided a rationale for the observed flux values. Increasing the viscosity of the donor solution is hypothesized to afford a curvilinear permeation profile for the PEGylated NTX prodrug. 10.1016/j.jconrel.2010.05.034
    In vitro characterization of the invasiveness of polymer microneedle against skin. Noh Young-Wook,Kim Tae-Hun,Baek Jong-Suep,Park Hyoun-Hyang,Lee Seung S,Han Manhee,Shin Sang-Chul,Cho Cheong-Weon International journal of pharmaceutics The micro-sized needles could pierce the skin to deliver drugs effectively in a minimally invasive and painless manner. However, there are only a few reports that identify the invasiveness and painlessness of microneedle (MN), and in vitro characterization studies were conducted to examine the invasiveness of MN in experimental animals and healthy volunteers. First, a fluorescent molecule was applied to show the skin holes according to the application time of MN and then the whitening effect in UV-exposed hairless rats was observed using reflectance spectroscopy according to the application time of MN. The extent of skin irritation by the application time of MN in healthy volunteers was determined from the value of skin redness. Regardless of MN application time, skin redness occurred and then disappeared 30 min after removal of MN; this phenomenon was insignificant with the application time of MN. Thus, if the MN was applied, a skin hole appeared, skin redness was observed and then the skin redness disappeared 30 min after removal of MN. Taken together, polymer MN might be a suitable tool for safe transdermal drug delivery of small molecules. 10.1016/j.ijpharm.2010.06.050
    Transdermal drug delivery by in-skin electroporation using a microneedle array. Yan Keshu,Todo Hiroaki,Sugibayashi Kenji International journal of pharmaceutics The aim of the present work was to develop a minimally invasive system for the delivery of macromolecular drugs to the deep skin tissues, so-called in-skin electroporation (IN-SKIN EP), using a microneedle (MN) electrode array. Fluorescein isothiocyanate (FITC)-dextran (FD-4: average molecular weight, 4.3 kDa) was used as the model macromolecular drug. MNs were arranged to puncture the skin barrier, the stratum corneum, and electrodes were used for EP so that a high electric field could be applied to skin tissues to promote viable skin delivery. In vitro skin permeation experiments showed that IN-SKIN EP had a much higher skin penetration-enhancing effect for FD-4 than MN alone or ON-SKIN EP (conventional EP treatment), and that higher permeation was achieved by applying a higher voltage and longer pulse width of EP. In addition, no marked skin irritation was observed by IN-SKIN EP, which was determined by the LDH leaching test. These results suggest that IN-SKIN EP can be more effectively utilized as a potential skin delivery system of macromolecular drugs than MN alone and conventional ON-SKIN EP. 10.1016/j.ijpharm.2010.06.052
    Optical coherence tomography is a valuable tool in the study of the effects of microneedle geometry on skin penetration characteristics and in-skin dissolution. Donnelly Ryan F,Garland Martin J,Morrow Desmond I J,Migalska Katarzyna,Singh Thakur Raghu Raj,Majithiya Rita,Woolfson A David Journal of controlled release : official journal of the Controlled Release Society In this study, we used optical coherence tomography (OCT) to extensively investigate, for the first time, the effect that microneedle (MN) geometry (MN height, and MN interspacing) and force of application have upon penetration characteristics of soluble poly(methylvinylether-co-maleic anhydride, PMVE/MA) MN arrays into neonatal porcine skin in vitro. The results from OCT investigations were then used to design optimal and suboptimal MN-based drug delivery systems and evaluate their drug delivery profiles cross full thickness and dermatomed neonatal porcine skin in vitro. It was found that increasing the force used for MN application resulted in a significant increase in the depth of penetration achieved within neonatal porcine skin. For example, MN of 600μm height penetrated to a depth of 330μm when inserted at a force of 4.4N/array, while the penetration increased significantly to a depth of 520μm, when the force of application was increased to 16.4N/array. At an application force of 11.0N/array it was found that, in each case, increasing MN height from 350 to 600μm to 900μm led to a significant increase in the depth of MN penetration achieved. Moreover, alteration of MN interspacing had no effect upon depth of penetration achieved, at a constant MN height and force of application. With respect to MN dissolution, an approximate 34% reduction in MN height occurred in the first 15min, with only 17% of the MN height remaining after a 3-hour period. Across both skin models, there was a significantly greater cumulative amount of theophylline delivered after 24h from an MN array of 900μm height (292.23±16.77μg), in comparison to an MN array of 350μm height (242.62±14.81μg) (p<0.001). Employing full thickness skin significantly reduced drug permeation in both cases. Importantly, this study has highlighted the effect that MN geometry and application force have upon the depth of penetration into skin. While it has been shown that MN height has an important role in the extent of drug delivered across neonatal porcine skin from a soluble MN array, further studies to evaluate the full significance of MN geometry on MN mediated drug delivery are now underway. The successful use of OCT in this study could prove to be a key development for polymeric MN research, accelerating their commercial exploitation. 10.1016/j.jconrel.2010.08.008
    A microneedle roller for transdermal drug delivery. Park Jung-Hwan,Choi Seong-O,Seo Soonmin,Choy Young Bin,Prausnitz Mark R European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V Microneedle rollers have been used to treat large areas of skin for cosmetic purposes and to increase skin permeability for drug delivery. In this study, we introduce a polymer microneedle roller fabricated by inclined rotational UV lithography, replicated by micromolding hydrophobic polylactic acid and hydrophilic carboxy-methyl-cellulose. These microneedles created micron-scale holes in human and porcine cadaver skin that permitted entry of acetylsalicylic acid, Trypan blue and nanoparticles measuring 50nm and 200nm in diameter. The amount of acetylsalicylic acid delivered increased with the number of holes made in the skin and was 1-2 orders of magnitude greater than in untreated skin. Lateral diffusion in the skin between holes made by microneedles followed expected diffusional kinetics, with effective diffusivity values that were 23-160 times smaller than in water. Compared to inserting microneedles on a flat patch, the sequential insertion of microneedles row by row on a roller required less insertion force in full-thickness porcine skin. Overall, polymer microneedle rollers, prepared from replicated polymer films, offer a simple way to increase skin permeability for drug delivery. 10.1016/j.ejpb.2010.07.001
    Transdermal delivery of insulin using microneedle rollers in vivo. Zhou Cui-Ping,Liu Yu-Ling,Wang Hong-Liang,Zhang Peng-Xiao,Zhang Jin-Lan International journal of pharmaceutics This study characterizes skin perforation by commercially available microneedle rollers and evaluates the efficacy of transdermal delivery of insulin to diabetic rats. Three different needle lengths, 250, 500 and 1000 microm, were used in this work. Creation and resealing of the skin holes that were produced by the needles were observed by Evan's blue (EB) staining and transepidermal water loss (TEWL) measurements. EB clearly showed that microchannels were formed in the skin and that the pores created by the longest microneedle (1000 microm) persisted no longer than 8h, while the hypodermic injury was still observed 24h later. TEWL significantly increased after the application of the needles and then decreased with time, which explains the recovery of skin barrier function and agrees well with EB results. The extent of permeation was demonstrated by insulin delivery in vivo. The rapid reduction of blood glucose levels in 1h was caused by the increased permeability of the skin to insulin after applying microneedle rollers. The reduced decrease after 1h is closely associated with hole recovery. In conclusion, microneedle rollers with 500-microm or shorter lengths are safe and useful in transdermal delivery of insulin in vivo. 10.1016/j.ijpharm.2010.03.041
    Dissolving polymer microneedle patches for influenza vaccination. Sullivan Sean P,Koutsonanos Dimitrios G,Del Pilar Martin Maria,Lee Jeong Woo,Zarnitsyn Vladimir,Choi Seong-O,Murthy Niren,Compans Richard W,Skountzou Ioanna,Prausnitz Mark R Nature medicine Influenza prophylaxis would benefit from a vaccination method enabling simplified logistics and improved immunogenicity without the dangers posed by hypodermic needles. Here we introduce dissolving microneedle patches for influenza vaccination using a simple patch-based system that targets delivery to skin's antigen-presenting cells. Microneedles were fabricated using a biocompatible polymer encapsulating inactivated influenza virus vaccine for insertion and dissolution in the skin within minutes. Microneedle vaccination generated robust antibody and cellular immune responses in mice that provided complete protection against lethal challenge. Compared to conventional intramuscular injection, microneedle vaccination resulted in more efficient lung virus clearance and enhanced cellular recall responses after challenge. These results suggest that dissolving microneedle patches can provide a new technology for simpler and safer vaccination with improved immunogenicity that could facilitate increased vaccination coverage. 10.1038/nm.2182
    Macromolecular delivery into skin using a hollow microneedle. Wonglertnirant Nanthida,Todo Hiroaki,Opanasopit Praneet,Ngawhirunpat Tanasait,Sugibayashi Kenji Biological & pharmaceutical bulletin The objective of the present study was to obtain information to develop an effective delivery device regarding a sophisticated hollow microneedle array-patch system. Thus, the potential of hollow microneedles was investigated for enhancing the transdermal delivery of hydrophilic large molecular compounds, and the effect of variable parameters on drug release behavior was determined from skin. Fluorescein isothiocyanate (FITC)-dextrans (4.3 kDa), FD-4, was used as the main model compound, and it was successfully loaded into the lower epidermis as well as the superficial dermis of the skin in hairless rats by a hollow microneedle. The higher the volume of FD-4 solution injected, the faster the FD-4 release rate from skin. In addition, release rate tended to increase when FD-4 was administered dividedly by multiple injections. These release profiles of FD-4 were expressed by Fick's law of diffusion. Furthermore, a combination of the formulation strategy and hollow microneedle-assisted delivery was useful for controlling the drug release rate from skin. Release profiles from drug-loaded skin were also compared by changing the molecular weights of model compounds. The larger molecular size of compounds caused a lower release rate from skin. These results suggest the utilization of hollow microneedle to enhance transdermal delivery of large molecular compounds and provide useful information for designing an effective hollow microneedle system. 10.1248/bpb.33.1988
    Microneedle delivery of H5N1 influenza virus-like particles to the skin induces long-lasting B- and T-cell responses in mice. Song Jae-Min,Kim Yeu-Chun,Lipatov Aleksandr S,Pearton Marc,Davis C Todd,Yoo Dae-Goon,Park Kyoung-Mi,Chen Li-Mei,Quan Fu-Shi,Birchall James C,Donis Ruben O,Prausnitz Mark R,Compans Richard W,Kang Sang-Moo Clinical and vaccine immunology : CVI A simple method suitable for self-administration of vaccine would improve mass immunization, particularly during a pandemic outbreak. Influenza virus-like particles (VLPs) have been suggested as promising vaccine candidates against potentially pandemic influenza viruses, as they confer long-lasting immunity but are not infectious. We investigated the immunogenicity and protective efficacy of influenza H5 VLPs containing the hemagglutinin (HA) of A/Vietnam/1203/04 (H5N1) virus delivered into the skin of mice using metal microneedle patches and also studied the response of Langerhans cells in a human skin model. Prime-boost microneedle vaccinations with H5 VLPs elicited higher levels of virus-specific IgG1 and IgG2a antibodies, virus-specific antibody-secreting cells, and cytokine-producing cells up to 8 months after vaccination compared to the same antigen delivered intramuscularly. Both prime-boost microneedle and intramuscular vaccinations with H5 VLPs induced similar hemagglutination inhibition titers and conferred 100% protection against lethal challenge with the wild-type A/Vietnam/1203/04 virus 16 weeks after vaccination. Microneedle delivery of influenza VLPs to viable human skin using microneedles induced the movement of CD207(+) Langerhans cells toward the basement membrane. Microneedle vaccination in the skin with H5 VLPs represents a promising approach for a self-administered vaccine against viruses with pandemic potential. 10.1128/CVI.00100-10
    Microneedle-based transcutaneous immunisation in mice with N-trimethyl chitosan adjuvanted diphtheria toxoid formulations. Bal Suzanne M,Ding Zhi,Kersten Gideon F A,Jiskoot Wim,Bouwstra Joke A Pharmaceutical research PURPOSE:The purpose of this study was to gain insight into the delivery and immunogenicity of N-trimethyl chitosan (TMC) adjuvanted diphtheria toxoid (DT) formulations applied transcutaneously with microneedles. METHODS:Mice were vaccinated with DT-loaded TMC nanoparticles, a solution of TMC and DT (TMC/DT) or DT alone. The formulations were applied onto the skin before or after microneedle treatment with two different 300-microm-long microneedle arrays and also injected intradermally (ID). As a positive control, alum-adjuvanted DT (DT-alum) was injected subcutaneously (SC). Ex vivo confocal microscopy studies were performed with rhodamine-labelled TMC. RESULTS:Independent of the microneedle array used and the sequence of microneedle treatment and vaccine application, transcutaneous immunisation with the TMC/DT mixture elicited 8-fold higher IgG titres compared to the TMC nanoparticles or DT solution. The toxin-neutralising antibody titres from this group were similar to those elicited by SC DT-alum. After ID immunisation, both TMC-containing formulations induced enhanced titres compared to a DT solution. Confocal microscopy studies revealed that transport of the TMC nanoparticles across the microneedle conduits was limited compared to a TMC solution. CONCLUSIONS:In conclusion, TMC has an adjuvant function in transcutaneous immunisation with microneedles, but only if applied in a solution. 10.1007/s11095-010-0182-y
    Influence of microneedle shape on the transport of a fluorescent dye into human skin in vivo. Bal Suzanne M,Kruithof Annelieke C,Zwier Raphaël,Dietz Ekkehart,Bouwstra Joke A,Lademann Jürgen,Meinke Martina C Journal of controlled release : official journal of the Controlled Release Society Microneedles can enhance the penetration of vaccines into the skin for transcutaneous vaccination. In this study for the first time the influence of microneedle geometry on the transport through the formed conduits was visualised in human volunteers by confocal laser scanning microscopy. Three differently shaped 300 μm long microneedle arrays were selected and fluorescein was applied either before or after piercing. Based on the intensity a distinction was made between regions with high and low intensity fluorescence (HIF and LIF). The areas of both intensities were quantified over time. In most cases HIF areas were only present in the stratum corneum, while LIF areas were also present in the viable epidermis. The areas were larger if fluorescein was applied after piercing compared to before piercing. After 15 min almost no HIF was present anymore at the skin surface. The microneedle geometry, but not the manner of application affected the shape and depth of the conduits. In conclusion we showed that the different microneedle arrays are able to form conduits in the skin, but the geometry of the microneedles influences the penetration of the fluorescent dye. This is the first step towards a more rational design of microneedle arrays for transcutaneous vaccination. 10.1016/j.jconrel.2010.07.104
    Current aspects of formulation efforts and pore lifetime related to microneedle treatment of skin. Milewski Mikolaj,Brogden Nicole K,Stinchcomb Audra L Expert opinion on drug delivery IMPORTANCE OF THE FIELD:The efficacy of microneedles in the area of transdermal drug delivery is well documented. Multiple studies have shown that enhancement of skin permeation by means of the creation of microscopic pores in the stratum corneum can greatly improve the delivery rates of drugs. However, skin pretreatment with microneedles is not the only factor affecting drug transport rates. Other factors, including drug formulation and rate of micropore closure, are also important for optimizing delivery by this route. AREAS COVERED IN THIS REVIEW:This review aims to highlight work that has been done in these areas, with an emphasis on drug formulation parameters that affect transdermal flux. WHAT THE READER WILL GAIN:This review creates an appreciation for the many factors affecting microneedle-enhanced delivery. Most results clearly indicate that microneedle skin pretreatment by itself may have different effects on drug transport depending on the formulation used, and formulation characteristics have different effects on the transport through untreated skin and microneedle-treated skin. Several formulation approaches are reported to optimize microneedle-enhanced drug delivery, including co-solvent use, vesicular, nanoparticulate and gel systems. TAKE HOME MESSAGE:In addition to well-established factors that affect microneedle-assisted delivery (geometry, type of microneedle, etc.), formulation and pore viability are also critical factors that must be considered. 10.1517/17425241003663228
    In-vivo dynamic characterization of microneedle skin penetration using optical coherence tomography. Enfield Joey,O'Connell Marie-Louise,Lawlor Kate,Jonathan Enock,O'Mahony Conor,Leahy Martin Journal of biomedical optics The use of microneedles as a method of circumventing the barrier properties of the stratum corneum is receiving much attention. Although skin disruption technologies and subsequent transdermal diffusion rates are being extensively studied, no accurate data on depth and closure kinetics of microneedle-induced skin pores are available, primarily due to the cumbersome techniques currently required for skin analysis. We report on the first use of optical coherence tomography technology to image microneedle penetration in real time and in vivo. We show that optical coherence tomography (OCT) can be used to painlessly measure stratum corneum and epidermis thickness, as well as microneedle penetration depth after microneedle insertion. Since OCT is a real-time, in-vivo, nondestructive technique, we also analyze skin healing characteristics and present quantitative data on micropore closure rate. Two locations (the volar forearm and dorsal aspect of the fingertip) have been assessed as suitable candidates for microneedle administration. The results illustrate the applicability of OCT analysis as a tool for microneedle-related skin characterization. 10.1117/1.3463002
    Evaluation needle length and density of microneedle arrays in the pretreatment of skin for transdermal drug delivery. Yan Guang,Warner Kevin S,Zhang Jie,Sharma Sanjay,Gale Bruce K International journal of pharmaceutics Solid silicon microneedle arrays with different needle lengths (ranging from 100 to 1100 microm) and needle densities (ranging from 400 to 11,900 needles/cm(2)) were used to penetrate epidermal membrane of human cadaver skin. After this pretreatment, the electrical resistance of the skin and the flux of acyclovir across the skin were monitored. A linear correlation between the acyclovir flux and the inverse of the skin electric resistance was observed. Microneedle arrays with longer needles (>600 microm) were more effective in creating pathways across skin and enhancing drug flux, and microneedle arrays with lower needle densities (<2000 needles/cm(2)) were more effective in enhancing drug flux if the microneedles with long enough needle length (>600 microm). In addition, the microneedle arrays were used to penetrate hairless rat skin in vivo, and the trans-epidermal water loss (TEWL) of the rat skin was measured before and after the pretreatment. Treating rat skin with microneedle arrays of lower needle density and longer needle length was more effective in increasing TEWL. Integrity of the stratum corneum barrier of the penetrated rat skin as measured by TEWL recovered back to its base line level within 24h after the microneedle pretreatment. 10.1016/j.ijpharm.2010.02.007
    Photodynamic therapy with methyl 5-aminolevulinate acid might be ineffective in recalcitrant alopecia totalis regardless of using a microneedle roller to increase skin penetration. Yoo Kwang Ho,Lee Jin Woong,Li Kapsok,Kim Beom Joon,Kim Myeung Nam Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.] BACKGROUND:Photodynamic therapy (PDT) with aminolevulinic acid or methyl 5-aminolevulinic acid (MAL) has been tried for the treatment of alopecia areata (AA). Unfortunately, the efficacy of PDT in treating AA is still being debated, and most clinical trials have produced disappointing results, which may have been because of the lack of treatment rationale or because of drug penetration. In several clinical trials of PDT in AA, the dermatologists suspected that skin preparations, including mechanical or chemical peeling, might be incomplete for drug penetration. OBJECTIVE:In this pilot study, the efficacy of PDT in treating AA was investigated, and the treatment effect of the use of a microneedle roller for the enhancement of the transepidermal drug delivery system was evaluated. MATERIALS AND METHODS:Eight Korean patients with alopecia totalis were enrolled in this study. Before the PDT, the right sides of the patients' scalps were prepared using 70% alcohol dressing and microneedle rolling, and the left sides (the control sides, without microneedle rolling) were only cleansed with 70% alcohol dressing. Immediately after the microneedle roller preparation, MAL was applied on the right scalp area under occlusion for 3 hours. Both sides were then illuminated with a red light (average wavelength, 630 nm; light dose, 37 J/cm(2)) for 7.5 minutes. Each patient received three treatments at 4-week intervals. A photograph of each patient was taken before and after the treatment. Biopsy was performed on the samples that were taken from both sides of the alopecia totalis lesions after 16 weeks (4 weeks after the final treatment). RESULTS:After the three treatments, none of the patients achieved hair growth in the microneedle-rolled lesion or in the unrolled lesion. Furthermore, there was no increment in the density of the anagen hair follicles and no difference in the histologic findings of the groups. CONCLUSION:PDT with MAL may not be effective for the treatment of alopecia totalis, regardless of the use of a microneedle roller to increase skin penetration. 10.1111/j.1524-4725.2010.01515.x
    Effect of applying modes of the polymer microneedle-roller on the permeation of L-ascorbic acid in rats. You Sung-Kyun,Noh Young-Wook,Park Hyoun-Hyang,Han Manhee,Lee Seung S,Shin Sang-Chul,Cho Cheong-Weon Journal of drug targeting Despite the advantages of drug delivery through skin, transdermal drug delivery is only used with a small subset of drugs because most compounds cannot cross the skin at therapeutically useful rates. Recently, a new concept known as microneedle was introduced and could be used to pierce effectively to deliver drugs using micron-sized needles in a minimally invasive and painless manner. In this study, the polymer microneedle-roller was fabricated so that it can be applied into the permeation of L-ascorbic acid. Moreover, a recent publication suggested the possibility of ascorbic acid 2-phosphate as a hair restorer; hence, this study was carried out to check the effect of L-ascorbic acid itself on the hair growing rate in rats according to the presence of various application frequencies of the polymer microneedle-roller. When the polymer microneedle-roller was applied nine times with four directions into rat's shaved skin, the permeation of L-ascorbic acid increased by 10.54-fold compared to that of the absence of the polymer microneedle-roller. The histological examination revealed that the skin pretreated with various application frequencies of the polymer microneedle-roller had more transport pathways. The faster hair growing phenomenon was observed in the presence of polymer microneedle-roller compared to the absence of the polymer microneedle-roller. 10.3109/10611860903115274
    Fabrication of dissolving polymer microneedles for controlled drug encapsulation and delivery: Bubble and pedestal microneedle designs. Chu Leonard Y,Choi Seong-O,Prausnitz Mark R Journal of pharmaceutical sciences Dissolving microneedle patches offer promise as a simple, minimally invasive method of drug and vaccine delivery to the skin that avoids the need for hypodermic needles. However, it can be difficult to control the amount and localization of drug within microneedles. In this study, we developed novel microneedle designs to improve control of drug encapsulation and delivery using dissolving microneedles by (i) localizing drug in the microneedle tip, (ii) increasing the amount of drug loaded in microneedles while minimizing wastage, and (iii) inserting microneedles more fully into the skin. Localization of our model drug, sulforhodamine B in the microneedle tip by either casting a highly concentrated polymer solution as the needle matrix or incorporating an air bubble at the base of the microneedle achieved approximately 80% delivery within 10 min compared to 20% delivery achieved by the microneedles encapsulating nonlocalized drug. As another approach, a pedestal was introduced to elevate each microneedle for more complete insertion into the skin and to increase its drug loading capacity by threefold from 0.018 to 0.053 microL per needle. Altogether, these novel microneedle designs provide a new set of tools to fabricate dissolving polymer microneedles with improved control over drug encapsulation, loading, and delivery. 10.1002/jps.22140
    [New options of influenza vaccination]. Chlíbek R Casopis lekaru ceskych One of the ways to increase a low rate of vaccination against the flu in the Czech population is using new vaccination methods, e.g. the intradermal flu vaccine application method. This method uses a high skin immune potential, where a great amount of dendritic cells, macrophages, lymphocytes as well as abundant capillary and lymphatic supply can be found. A progressive microneedle application system allows the accurate application right into the dermis and a dosage consistency without any necessity of much experience and training in intradermal administration. Comparable results of immunogenity with lower antigen content and less vaccine amount are reached with intramuscular application in adults up to 59. Using the same antigen amount as in intramuscular application in people older than 60, significantly better results are reached. A new intradermal vaccine IDflu is registered in Europe for people from the age of 18 and it is considered to be a new alternative way to raise popularity of flu vaccination in lay and professional public. The microneedle intradermal application system brings an easier way of vaccination for doctors with application of less amount of vaccine and there is no need to remove air from the syringe and no need of aspiration. The vaccine will be introduced in the Czech market before the flu season 2010/2011.
    Effects of chemical and physical enhancement techniques on transdermal delivery of cyanocobalamin (vitamin B12) in vitro. Yang Ye,Kalluri Haripriya,Banga Ajay K Pharmaceutics Vitamin B12 deficiency, which may result in anemia and nerve damage if left untreated, is currently treated by administration of cyanocobalamin via oral or intramuscular routes. However, these routes are associated with absorption and compliance issues which have prompted us to investigate skin as an alternative site of administration. Delivery through skin, however, is restricted to small and moderately lipophilic molecules due to the outermost barrier, the stratum corneum (SC). In this study, we have investigated the effect of different enhancement techniques, chemical enhancers (ethanol, oleic acid, propylene glycol), iontophoresis (anodal iontophoresis) and microneedles (soluble maltose microneedles), which may overcome this barrier and improve cyanocobalamin delivery. Studies with different chemical enhancer formulations indicated that ethanol and oleic acid decreased the lag time while propylene glycol based formulations increased the lag time. The formulation with ethanol (50%), oleic acid (10%) and propylene glycol (40%) showed the maximum improvement in delivery. Iontophoresis and microneedle treatments resulted in enhanced permeation levels compared to passive controls. These enhancement approaches can be explored further to develop alternative treatment regimens. 10.3390/pharmaceutics3030474
    Formation of oligovesicular vesicles by micromanipulation. Okumura Yukihisa,Ohmiya Tohru,Yamazaki Toshiki Membranes Cell-sized lipid bilayer membrane vesicles (giant vesicles, GVs) or semi-vesicles were formed from egg yolk phosphatidylcholine on a platinum electrode under applied electric voltage by electroformation. Micromanipulation of the semi-vesicle by first pressing its membrane with a glass microneedle and then withdrawing the needle left a GV in the interior of the vesicle. During the process, an aqueous solution of Ficoll that filled the needle was introduced into the newly formed inner vesicle and remained encapsulated. Approximately 50% of attempted micromanipulation resulted in the formation of an inner daughter vesicle, "microvesiculation". By repeating the microvesiculation process, multiple inner GVs could be formed in a single parent semi-vesicle. A semi-vesicle with inner GVs could be detached from the electrode by scraping with a microneedle, yielding an oligovesicular vesicle (OVV) with desired inner aqueous contents. Microvesiculation of a GV held on the tip of a glass micropipette was also possible, and this also produced an OVV. Breaking the membrane of the parent semi-vesicle by micromanipulation with a glass needle after microvesiculation, released the inner GVs. This protocol may be used for controlled formation of GVs with desired contents. 10.3390/membranes1040265
    Rapid intradermal delivery of liquid formulations using a hollow microstructured array. Burton Scott A,Ng Chin-Yee,Simmers Ryan,Moeckly Craig,Brandwein David,Gilbert Tom,Johnson Nathan,Brown Ken,Alston Tesha,Prochnow Gayatri,Siebenaler Kris,Hansen Kris Pharmaceutical research PURPOSE:The purpose of this work is to demonstrate rapid intradermal delivery of up to 1.5 mL of formulation using a hollow microneedle delivery device designed for self-application. METHODS:3M's hollow Microstructured Transdermal System (hMTS) was applied to domestic swine to demonstrate delivery of a variety of formulations including small molecule salts and proteins. Blood samples were collected after delivery and analyzed via HPLC or ELISA to provide a PK profile for the delivered drug. Site evaluations were conducted post delivery to determine skin tolerability. RESULTS:Up to 1.5 mL of formulation was infused into swine at a max rate of approximately 0.25 mL/min. A red blotch, the size of the hMTS array, was observed immediately after patch removal, but had faded so as to be almost indistinguishable 10 min post-patch removal. One-mL deliveries of commercial formulations of naloxone hydrochloride and human growth hormone and a formulation of equine anti-tetanus toxin were completed in swine. With few notable differences, the resulting PK profiles were similar to those achieved following subcutaneous injection of these formulations. CONCLUSIONS:3M's hMTS can provide rapid, intradermal delivery of 300-1,500 µL of liquid formulations of small molecules salts and proteins, compounds not typically compatible with passive transdermal delivery. 10.1007/s11095-010-0177-8
    A novel microparticulate vaccine for melanoma cancer using transdermal delivery. Bhowmik Tuhin,D'Souza Bernadette,Shashidharamurthy Rangaiah,Oettinger Carl,Selvaraj Periasamy,D'Souza Martin J Journal of microencapsulation In this study, we formulated a microparticulate melanoma cancer vaccine via the transdermal route. The vaccine was delivered using microneedle-based Dermaroller® which is available for cosmetic purposes. Unlike subcutaneous injections, administration using microneedles is painless and in general can increase the permeability of many compounds ranging in size from small molecules to proteins and microparticles that do not normally penetrate the skin. The vaccine microparticles were taken up by the antigen presenting cells which demonstrated a strong IgG titre level of 930 ug/mL in serum samples. The formulation increased the immunogenicity of the vaccine by incorporating the antigen into an albumin matrix having a size range of around 0.63-1.4 µm which acted as a synthetic adjuvant. The animals were vaccinated with 1 prime and 4 booster doses administered every 14 days over 8 weeks duration, followed by challenge with live tumour cells which showed protection after transdermal vaccination. 10.3109/02652048.2011.559287
    Single-molecule measurements using microneedles. Yanagida Toshio,Ishii Yoshiharu,Ishijima Akihiko Methods in molecular biology (Clifton, N.J.) Myosin is both an enzyme and a molecular motor that hydrolyzes ATP and interacts with actin filaments for force generation. Manipulation techniques with microneedles and laser traps have recently been developed to capture and manipulate the actomyosin interaction for the purpose of revealing the mechanics of this system. Combined with single-molecule imaging techniques, the coupling between chemical processes (ATP hydrolysis) and mechanical processes (myosin force generation) has been directly determined. In this chapter, we describe these two manipulation techniques, especially microneedle method, in detail. 10.1007/978-1-61779-261-8_10
    Novel antigen delivery technologies: a review. Jain Deepika,Jain Vikas,Singh Ranjit Drug delivery and translational research Over the past few years, new insights into immunobiology and delivery systems have allowed the development of better vaccines and for a wider range of diseases. Currently available vaccines represent outstanding success story in modern medicine and have had a dramatic effect on morbidity and mortality worldwide. Conventional vaccines have been based on live attenuated, or killed, viruses or bacteria, or recombinant proteins from these organisms. The design of live attenuated vaccines depended to some extent on serendipity and resulted in low success rates. Both live attenuated and killed vaccines require handling of live pathogens and are associated with safety problems. Despite the success of vaccines, there is a clear need for novel antigen delivery technologies to improve vaccine efficacy and safety. Antigen stability, safety, and immunogenicity are the key hurdles in development of novel antigen delivery technologies. Nowadays, various novel drug delivery systems are becoming one of the fastest growing sectors in the pharmaceutical and biotechnological industries. Delivery of vaccines via oral, intranasal, transcutaneous, and intradermal routes will decrease the risk of needle-borne diseases and may eliminate the need for trained personnel and sterile equipment. Currently, various techniques involving DNA vaccines, adjuvants, nanoparticles, liposome, microneedle, and NanoMAP technology are being developed and evaluated. This review focuses on the current development of some novel vaccine delivery systems and will explore the non-parenteral routes of vaccine administrations. 10.1007/s13346-011-0014-6
    Nanosecond vortex laser pulses with millijoule pulse energies from a Yb-doped double-clad fiber power amplifier. Koyama Mio,Hirose Tetsuya,Okida Masahito,Miyamoto Katsuhiko,Omatsu Takashige Optics express Nanosecond vortex pulses were generated using a stressed, large-mode-area, Yb-doped, fiber amplifier with an off-axis coupling technique for the first time. A pulse energy of 0.83 mJ (corresponding to a peak power of 59 kW) was achieved at a pump power of 25.7 W. The optical-optical efficiency was measured to be 31%. The millijoule nanosecond vortex pulses will be potentially applied to novel material processing, such as metal microneedle fabrication. 10.1364/OE.19.014420
    Visualization of plasmid delivery to keratinocytes in mouse and human epidermis. González-González Emilio,Kim Yeu-Chun,Speaker Tycho J,Hickerson Robyn P,Spitler Ryan,Birchall James C,Lara Maria Fernanda,Hu Rong-Hua,Liang Yanhua,Kirkiles-Smith Nancy,Prausnitz Mark R,Milstone Leonard M,Contag Christopher H,Kaspar Roger L Scientific reports The accessibility of skin makes it an ideal target organ for nucleic acid-based therapeutics; however, effective patient-friendly delivery remains a major obstacle to clinical utility. A variety of limited and inefficient methods of delivering nucleic acids to keratinocytes have been demonstrated; further advances will require well-characterized reagents, rapid noninvasive assays of delivery, and well-developed skin model systems. Using intravital fluorescence and bioluminescence imaging and a standard set of reporter plasmids we demonstrate transfection of cells in mouse and human xenograft skin using intradermal injection and two microneedle array delivery systems. Reporter gene expression could be detected in individual keratinocytes, in real-time, in both mouse skin as well as human skin xenografts. These studies revealed that non-invasive intravital imaging can be used as a guide for developing gene delivery tools, establishing a benchmark for comparative testing of nucleic acid skin delivery technologies. 10.1038/srep00158
    [Development of transcutaneous vaccine formulations for the infectious disease countermeasure]. Matsuo Kazuhiko,Okada Naoki,Nakagawa Shinsaku Nihon rinsho. Japanese journal of clinical medicine The recent vigorous transnational migration of people and materials reflecting the development of transportation facilities have increased the global spread of infections. On the basis of this social background, the development of vaccination, which is the only fundamental prophylaxis, is in attention. Even if, however, rapid manufacture of vaccine antigen is actualized, there are several problems that vaccine is not easily spread across the developing country, because conventional vaccination is performed mainly by injection. Our group developed two transcutaneous vaccine devices which delivered antigens to antigen-presenting cells: a hydrogel patch and a dissolving microneedle patch. Our transcutaneous immunization system using these devices receives a high evaluation as novel, easy-to-use, and low-invasive vaccination method against infections from home and abroad.
    Incidence of low bioavailability of leuprolide acetate after percutaneous administration to rats by dissolving microneedles. Ito Yukako,Murano Hiroshi,Hamasaki Noriyuki,Fukushima Keizo,Takada Kanji International journal of pharmaceutics Two-layered dissolving microneedles of which acral portion contained leuprolide acetate (LA) as solid dispersion were prepared with sodium chondroitin sulfate as the base and the systemic absorption efficiency of LA was studied in rats after administration to their abdominal skin. A patch contained 100 dissolving microneedles of which length and basement diameter were 469.8±4.7 μm and 284.5±9.8 μm, where LA content was 14.3±1.6 μg. In vitro dissolution experiment showed that LA was released from dissolving microneedle patch within 3 min. LA was stable in the patch, % recoveries for 3 months were 102.2±1.9-95.3±1.9%. One and half-patch of LA dissolving microneedles were administered to the rat skin and plasma LA concentrations were measured by LC-MS/MS. Plasma LA concentrations increased immediately after administration, and reached to the maximum level at 15 min, where C(max) were 6.0±0.7 and 16.4±0.9 μg/ml, respectively. The AUC were 5.8±0.8 and 14.5±0.4 μg h/ml and BA were 33.8±4.3% and 31.7±0.8%. When LA solution was subcutaneously (s.c.) injected to rats, 50 μg/kg, the BA was 32.0±2.1%. Relative BA of LA from dissolving microneedles against s.c. solution was 105.6±13.5%. The degradation rate of LA in the rat skin tissue homogenate was very fast where the half-life was 16.3±5.7 min. The degradation of LA in the skin tissue was the cause of the low BA of LA after percutaneous administration to rats. 10.1016/j.ijpharm.2011.01.039
    Investigation of cell-substrate interactions by focused ion beam preparation and scanning electron microscopy. Friedmann Andrea,Hoess Andreas,Cismak Andreas,Heilmann Andreas Acta biomaterialia Cell-substrate interactions, which are an important issue in tissue engineering, have been studied using focused ion beam (FIB) milling and scanning electron microscopy (SEM). Sample cross-sections were generated at predefined positions (target preparation) to investigate the interdependency of growing cells and the substrate material. The experiments focus on two cell culturing systems, hepatocytes (HepG2) on nanoporous aluminum oxide (alumina) membranes and mouse fibroblasts (L929) and primary nerve cells on silicon chips comprised of microneedles. Cross-sections of these soft/hard hybrid systems cannot be prepared by conventional techniques like microtomy. Morphological investigations of hepatocytes growing on nanoporous alumina membranes demonstrate that there is in-growth of microvilli from the cell surface into porous membranes having pore diameters larger than 200 nm. Furthermore, for various cell cultures on microneedle arrays contact between the cells and the microneedles can be observed at high resolution. Based on FIB milled cross-sections and SEM micrographs cells which are only in contact with microneedles and cells which are penetrated by microneedles can be clearly distinguished. Target preparation of biological samples by the FIB technique especially offers the possibility of preparing not only soft materials but also hybrid samples (soft/hard materials). Followed by high resolution imaging by SEM, new insights into cell surface interactions can be obtained. 10.1016/j.actbio.2011.02.024
    Integrated carbon fiber electrodes within hollow polymer microneedles for transdermal electrochemical sensing. Miller Philip R,Gittard Shaun D,Edwards Thayne L,Lopez Deanna M,Xiao Xiaoyin,Wheeler David R,Monteiro-Riviere Nancy A,Brozik Susan M,Polsky Ronen,Narayan Roger J Biomicrofluidics In this study, carbon fiber electrodes were incorporated within a hollow microneedle array, which was fabricated using a digital micromirror device-based stereolithography instrument. Cell proliferation on the acrylate-based polymer used in microneedle fabrication was examined with human dermal fibroblasts and neonatal human epidermal keratinocytes. Studies involving full-thickness cadaveric porcine skin and trypan blue dye demonstrated that the hollow microneedles remained intact after puncturing the outermost layer of cadaveric porcine skin. The carbon fibers underwent chemical modification in order to enable detection of hydrogen peroxide and ascorbic acid; electrochemical measurements were demonstrated using integrated electrode-hollow microneedle devices. 10.1063/1.3569945
    Increasing mechanical stimulus induces migration of Langerhans cells and impairs the immune response to intracutaneously delivered antigen. Ruutu Merja P,Chen Xianfeng,Joshi Ojas,Kendall Mark A,Frazer Ian H Experimental dermatology Skin is subjected regularly to mechanical stimulus. Surprisingly, when studying the use of microneedle arrays to introduce antigen into skin, we observed that mechanical stimulus to skin achieved by application of the arrays or a flat metal plate resulted in temporary depletion of Langerhans cells, with the degree of depletion related to the applied stress, whereas no depletion was seen in the interspersed dendritic epidermal T cell population. Further, a significantly impaired immune response to intracutaneous antigen administration was observed in skin recently subjected to mechanical stimulus. This observation may have implications for selection of sites of skin immunisation and for immunogenicity of infections at skin sites routinely subjected to mechanical stimuli. 10.1111/j.1600-0625.2010.01234.x
    Generation of phospholipid vesicle-nanotube networks and transport of molecules therein. Jesorka Aldo,Stepanyants Natalia,Zhang Haijiang,Ortmen Bahanur,Hakonen Bodil,Orwar Owe Nature protocols We describe micromanipulation and microinjection procedures for the fabrication of soft-matter networks consisting of lipid bilayer nanotubes and surface-immobilized vesicles. These biomimetic membrane systems feature unique structural flexibility and expandability and, unlike solid-state microfluidic and nanofluidic devices prepared by top-down fabrication, they allow network designs with dynamic control over individual containers and interconnecting conduits. The fabrication is founded on self-assembly of phospholipid molecules, followed by micromanipulation operations, such as membrane electroporation and microinjection, to effect shape transformations of the membrane and create a series of interconnected compartments. Size and geometry of the network can be chosen according to its desired function. Membrane composition is controlled mainly during the self-assembly step, whereas the interior contents of individual containers is defined through a sequence of microneedle injections. Networks cannot be fabricated with other currently available methods of giant unilamellar vesicle preparation (large unilamellar vesicle fusion or electroformation). Described in detail are also three transport modes, which are suitable for moving water-soluble or membrane-bound small molecules, polymers, DNA, proteins and nanoparticles within the networks. The fabrication protocol requires ∼90 min, provided all necessary preparations are made in advance. The transport studies require an additional 60-120 min, depending on the transport regime. 10.1038/nprot.2011.321
    Adjuvant effect of cationic liposomes and CpG depends on administration route. Slütter Bram,Bal Suzanne M,Ding Zhi,Jiskoot Wim,Bouwstra Joke A Journal of controlled release : official journal of the Controlled Release Society In this study we explored the immunization route-dependent adjuvanticity of cationic liposomes loaded with an antigen (ovalbumin; OVA) and an immune potentiator (CpG). Mice were immunized intranodally, intradermally, transcutaneously (with microneedle pre-treatment) and nasally with liposomal OVA/CpG or OVA/CpG solution. In vitro, OVA/CpG liposomes showed enhanced uptake by DCs of both OVA and CpG compared to OVA+CpG solution. A similar enhanced uptake by DCs was observed in vivo when fluorescent OVA/CpG liposomes were administered intranodally. However, after transcutaneous and nasal application a lower uptake of OVA/CpG liposomes compared to an OVA+CpG solution was observed. Moreover, the IgG titers after nasal and transcutaneous administration of OVA/CpG liposomes were reduced compared to administration of an OVA+CpG solution. Although serum IgG titers may suggest limited added value of liposomes to the immunogenicity, for all routes, OVA/CpG liposomes resulted in elevated IgG2a levels, whereas administration of OVA+CpG solutions did not. These data show that encapsulation of antigen and adjuvant into a cationic liposome has a beneficial effect on the quality of the antibody response in mice after intranodal or intradermal immunization, but impairs proper delivery of antigen and adjuvant to the lymph nodes when the formulations are administered transcutaneously or nasally. 10.1016/j.jconrel.2011.02.007
    Characterization of microchannels created by metal microneedles: formation and closure. Kalluri Haripriya,Kolli Chandra Sekhar,Banga Ajay K The AAPS journal Transdermal delivery of therapeutic agents for cosmetic therapy is limited to small and lipophilic molecules by the stratum corneum barrier. Microneedle technology overcomes this barrier and offers a minimally invasive and painless route of administration. DermaRoller(®), a commercially available handheld device, has metal microneedles embedded on its surface which offers a means of microporation. We have characterized the microneedles and the microchannels created by these microneedles in a hairless rat model, using models with 370 and 770 μm long microneedles. Scanning electron microscopy was employed to study the geometry and dimensions of the metal microneedles. Dye binding studies, histological sectioning, and confocal microscopy were performed to characterize the created microchannels. Recovery of skin barrier function after poration was studied via transepidermal water loss (TEWL) measurements, and direct observation of the pore closure process was investigated via calcein imaging. Characterization studies indicate that 770 μm long metal microneedles with an average base width of 140 μm and a sharp tip with a radius of 4 μm effectively created microchannels in the skin with an average depth of 152.5 ± 9.6 μm and a surface diameter of 70.7 ± 9.9 μm. TEWL measurements indicated that skin regains it barrier function around 4 to 5 h after poration, for both 370 and 770 μm microneedles. However, direct observation of pore closure, by calcein imaging, indicated that pores closed by 12 h for 370 μm microneedles and by 18 h for 770 μm microneedles. Pore closure can be further delayed significantly under occluded conditions. 10.1208/s12248-011-9288-3
    An experimental study of retinal endovascular surgery with a microfabricated needle. Kadonosono Kazuaki,Arakawa Akira,Yamane Shin,Uchio Eiichi,Yanagi Yasuo Investigative ophthalmology & visual science PURPOSE:To study the feasibility of performing retinal endovascular surgery with a microfabricated needle-based cannulation system at the level of the retinal microvasculature. METHODS:A total of 40 retinal vein vessels, and 40 porcine eyes were used, and the eyecups were prepared under an operating microscope. Twenty retinal veins each were pierced with a microfabricated needle having an outer diameter of 50 μm and with a micropipette having an outer diameter of 50 μm, respectively, and each vessel that was successfully pierced was injected with a solution. The piercing success rates and injection success rates were calculated, and a histologic examination of the site was performed in each eye. RESULTS:Piercing and injection with the microneedle were successful in all 20 eyes (100%). Histologic examination showed that the retinal vasculature was well preserved in all eyes in which piercing had been performed with the microneedle. Piercing with the micropipette, on the other hand, was successful in only 8 eyes (40%), and injection with the micropipette was successful in only 5 eyes (25%). The tip of the micropipette broke in 12 vessels during piercing and in 3 vessels during injection. CONCLUSIONS; The feasibility of performing microvascular piercing and intravascular injection of retinal veins with a microneedle was demonstrated in porcine eyes. It may be possible to administer solutions into retinal vessels more effectively with a microfabricated needle, and that may contribute to improving retinal endovascular surgery in human eyes. 10.1167/iovs.11-7327
    Suprachoroidal drug delivery to the back of the eye using hollow microneedles. Patel Samirkumar R,Lin Angela S P,Edelhauser Henry F,Prausnitz Mark R Pharmaceutical research PURPOSE:In this work, we tested the hypothesis that microneedles provide a minimally invasive method to inject particles into the suprachoroidal space for drug delivery to the back of the eye. METHODS:A single, hollow microneedle was inserted into the sclera, and infused nanoparticle and microparticle suspensions into the suprachoroidal space. Experiments were performed on whole rabbit, pig, and human eyes ex vivo. Particle delivery was imaged using brightfield and fluorescence microscopy as well as microcomputed tomography. RESULTS:Microneedles were shown to deliver sulforhodamine B as well as nanoparticle and microparticle suspensions into the suprachoroidal space of rabbit, pig, and human eyes. Volumes up to 35 μL were administered consistently. Optimization of the delivery device parameters showed that microneedle length, pressure, and particle size played an important role in determining successful delivery into the suprachoroidal space. Needle lengths of 800-1,000 μm and applied pressures of 250-300 kPa provided most reliable delivery. CONCLUSIONS:Microneedles were shown for the first time to deliver nanoparticle and microparticle suspensions into the suprachoroidal space of rabbit, pig and human eyes. This shows that microneedles may provide a minimally invasive method for controlled drug delivery to the back of the eye. 10.1007/s11095-010-0271-y
    Stability kinetics of influenza vaccine coated onto microneedles during drying and storage. Kim Yeu-Chun,Quan Fu-Shi,Compans Richard W,Kang Sang-Moo,Prausnitz Mark R Pharmaceutical research PURPOSE:This study sought to determine the effects of microneedle coating formulation, drying time and storage time on antigen stability and in vivo immunogenicity of influenza microneedle vaccines. METHODS:The stability of inactivated influenza virus vaccine was monitored by hemagglutination (HA) activity and virus particle aggregation as a function of storage time and temperature with or without trehalose. In vivo immunogenicity of inactivated influenza vaccines coated onto microneedles was determined in mice by virus-specific antibody titers and survival rates. RESULTS:In the absence of trehalose, HA activity decreased below 10% and to almost zero after 1 h and 1 month of drying, respectively. Addition of trehalose maintained HA activity above 60% after drying and above 20% after 1 month storage at 25°C. Loss of HA activity generally correlated with increased virus particle aggregation. Administration of microneedles coated with trehalose-stabilized influenza vaccine yielded high serum IgG antibody titers even after 1 month storage, and all animals survived with minimal weight loss after lethal challenge infection. CONCLUSIONS:Inactivated influenza virus vaccine coated on microneedles with trehalose significantly improved the HA activity as well as in vivo immunogenicity of the vaccine after an extended time of storage. 10.1007/s11095-010-0134-6
    Multiphoton microscopy of transdermal quantum dot delivery using two photon polymerization-fabricated polymer microneedles. Gittard Shaun D,Miller Philip R,Boehm Ryan D,Ovsianikov Aleksandr,Chichkov Boris N,Heiser Jeremy,Gordon John,Monteiro-Riviere Nancy A,Narayan Roger J Faraday discussions Due to their ability to serve as fluorophores and drug delivery vehicles, quantum dots are a powerful tool for theranostics-based clinical applications. In this study, microneedle devices for transdermal drug delivery were fabricated by means of two-photon polymerization of an acrylate-based polymer. We examined proliferation of cells on this polymer using neonatal human epidermal keratinocytes and human dermal fibroblasts. The microneedle device was used to inject quantum dots into porcine skin; imaging of the quantum dots was performed using multiphoton microscopy. 10.1039/c005374k
    Enabling skin vaccination using new delivery technologies. Kim Yeu-Chun,Prausnitz Mark R Drug delivery and translational research The skin is known to be a highly immunogenic site for vaccination, but few vaccines in clinical use target skin largely because conventional intradermal injection is difficult and unreliable to perform. Now, a number of new or newly adapted delivery technologies have been shown to administer vaccine to the skin either by non-invasive or minimally invasive methods. Non-invasive methods include high-velocity powder and liquid jet injection, as well as diffusion-based patches in combination with skin abrasion, thermal ablation, ultrasound, electroporation, and chemical enhancers. Minimally invasive methods are generally based on small needles, including solid microneedle patches, hollow microneedle injections, and tattoo guns. The introduction of these advanced delivery technologies can make the skin a site for simple, reliable vaccination that increases vaccine immunogenicity and offers logistical advantages to improve the speed and coverage of vaccination. 10.1007/s13346-010-0005-z
    Microneedles and their applications. Sachdeva Vishal,Banga Ajay K Recent patents on drug delivery & formulation Microneedle mediated microporation has proved its potential to enhance the delivery of therapeutic drug molecules through skin over the last one decade. Several patents have been granted and cutting edge research is going on particularly for the delivery of biopharmaceuticals (macromolecules like protein or peptides). The technology involves use of micron sized needles made of diverse materials to form microchannels into the stratum corneum (or deeper), outermost barrier layer of the skin. These microchannels are deep enough to facilitate efficient drug delivery through disrupted stratum corneum but short enough to avoid bleeding or pain. So far, the microneedle technology has been explored for drug and vaccine delivery through transcutaneous route. However, the miniaturized nature of these microneedles and anticipated minimal invasiveness has led the scientists to explore and patent its possible use for several other applications.The use of this technology in combination with other enhancement techniques has also gained recent attention. This review article focuses on the latest developments in the field of microneedles as described in patent and research literature. Comprehensive review of several topics including device design/fabrication, formulation development, safety/regulatory issues, therapeutic applications and major challenges in the commercialization of microneedles as medical devices has been presented here. 10.2174/187221111795471445
    Dissolving microneedles for transdermal drug administration prepared by stepwise controlled drawing of maltose. Lee Kwang,Lee Chang Yoel,Jung Hyungil Biomaterials Dissolving microneedles, three-dimensional polymer structures with microscale cross-sectional dimensions, have been introduced as a means of safe transdermal drug delivery. Most dissolving microneedles have been fabricated using a traditional micro-casting method that cures biopolymers within three-dimensional mold, nevertheless, repeated molding process may cause damage to encapsulated drugs, a critical hurdle for clinical application. Here, we describe the stepwise controlled drawing technique that can directly fabricate dissolving microneedle from maltose by precise controlling the drawing time and the viscosity of the maltose. Controlled drawing shaped the particular sharp-conical microneedles of 1200 μm length with tip diameter of 60 μm, and dissolved within 20 min in-vivo after inserting to the skin. This technique surpasses the limitations of micro-casting for dissolving microneedle. Furthermore, transdermal delivery of impermeable hydrophilic molecules such as ascorbic acid-2-glucoside and niacinamide was confirmed as inhibition of cutaneous hypermelanosis. We anticipate that controlled drawing technique will be suitable to design dissolving microneedles for use in minimally invasive transcutaneous drug delivery to patients. 10.1016/j.biomaterials.2011.01.014
    Rapid pharmacokinetics of intradermal insulin administered using microneedles in type 1 diabetes subjects. Gupta Jyoti,Felner Eric I,Prausnitz Mark R Diabetes technology & therapeutics BACKGROUND:This study compared the pharmacokinetics, postprandial glycemic response, and pain associated with intradermal lispro insulin delivery using a microneedle with that of a conventional catheter. SUBJECTS AND METHODS:Five subjects with type 1 diabetes were administered a bolus infusion of lispro insulin using a 9-mm-long subcutaneous catheter (control treatment) and a 0.9-mm-long microneedle (study treatment), followed by consumption of a standardized meal. Blood samples were periodically assayed for plasma glucose and free insulin levels. RESULTS:Intradermal insulin infusion using microneedles reached peak insulin concentrations in approximately half the time and led to greater reduction in plasma glucose levels than subcutaneous catheters. Microneedles were also significantly less painful than the catheters. CONCLUSION:The rapid pharmacokinetics and minimally invasive nature of intradermal insulin infusion using microneedles provide significant potential for improved diabetes management. 10.1089/dia.2010.0204
    Willingness to vaccinate or get vaccinated with an intradermal seasonal influenza vaccine: a survey of general practitioners and the general public in France and Germany. Arnou Robert,Frank Matthias,Hagel Thomas,Prébet Alice Advances in therapy INTRODUCTION:The elderly are at high risk of severe seasonal influenza and influenza-related death. Annual vaccination can effectively prevent influenza and its complications, and is recommended in the elderly. In the present study, surveys were undertaken in France and Germany to determine whether INTANZA (sanofi pasteur, Val-de-Reuil, France), the first intradermal influenza vaccine, administered using an innovative microneedle injection system, might influence physicians' likelihood of recommending influenza vaccination or the likelihood that the general public would seek influenza vaccination. METHODS:Physicians (France: n=260; Germany: n=223) and members of the general public aged ≥ 50 years (France: n=1706; Germany: n=1072) completed online surveys. Details of the INTANZA delivery system, and a "product profile" based on the properties of INTANZA, were presented. RESULTS:Most physicians and the general public found INTANZA and its microneedle injection system appealing. The main benefit of INTANZA, as perceived by physicians and the public, was the small needle size. Physicians also found the high immunogenicity compared with conventional intramuscular (IM) vaccines attractive. The majority of physicians believed that INTANZA would strongly help them to recommend vaccination to their unvaccinated patients (66% to 91%, depending upon patient characteristics); most (61% to 78%) would prefer to prescribe INTANZA rather than an IM vaccine. More than two-thirds of the unvaccinated general public would prefer INTANZA over IM vaccines, and the option of vaccination with INTANZA would encourage a large proportion of them to get vaccinated (60% to 74%), if it was recommended and they were given the choice. Physicians (≥ 82%) agreed that INTANZA may help increase vaccination coverage rates. CONCLUSION:The results of these surveys indicate that the availability of INTANZA may encourage physicians to recommend influenza vaccination, and members of the general public to get vaccinated. INTANZA may help to improve seasonal influenza vaccination coverage rates. 10.1007/s12325-011-0035-z
    Pharmaceutical development of biologics: fundamentals, challenges and recent advances. Su Jing,Mazzeo Jeffrey,Subbarao Nanda,Jin Tuo Therapeutic delivery The 46th Arden Conference, held in West Point, NY, USA, March 2011, focused on development of protein therapeutics, comprising preformulation, formulation, manufacturing, advanced delivery systems, protein characterization/analysis, and regulatory landscape. The sessions of preformulation and formulation development consisted of nine lectures discussing protein stability implications and characterization during purification, freeze-drying and manufacturing. The session on advanced drug delivery encompassed two new sustained-release microsphere formulations (protein microencapsulation by annealing of premade porous PLGA microspheres and aqueous-aqueous emulsion for preformulating proteins to solvent-resistant particles), two transdermal insulins (patching after thermal ablation of skin and phase-transition hydrogel microneedle patch), and a responsible hydrogel system for intra-ear delivery. The sessions on analytical technologies and regulatory landscape both focused on challenges for biosimilars. 10.4155/tde.11.58
    Numerical simulation of microneedles' insertion into skin. Kong X Q,Zhou P,Wu C W Computer methods in biomechanics and biomedical engineering Microneedles have recently received much attention as a novel way for transdermal drug delivery. In this paper, a numerical simulation of the insertion process of the microneedle into human skin is reported using the finite element method. A multilayer skin model consisting of the stratum corneum, dermis and underlying hypodermis has been developed. The effective stress failure criterion has been coupled with the element deletion technique to predict the complete insertion process. The numerical results show a good agreement with the reported experimental data for the deformation and failure of the skin and the insertion force. The influences of the mechanical properties of the skin and the microneedle geometry (e.g. tip area, wall angle and wall thickness) on the insertion force are discussed. The numerical results are helpful for the optimum design of the microneedles for the transdermal drug delivery system. 10.1080/10255842.2010.497144
    Permeation of antigen protein-conjugated nanoparticles and live bacteria through microneedle-treated mouse skin. Kumar Amit,Li Xinran,Sandoval Michael A,Rodriguez B Leticia,Sloat Brian R,Cui Zhengrong International journal of nanomedicine BACKGROUND:The present study was designed to evaluate the extent to which pretreatment with microneedles can enhance skin permeation of nanoparticles in vitro and in vivo. Permeation of live bacteria, which are physically nanoparticles or microparticles, through mouse skin pretreated with microneedles was also studied to evaluate the potential risk of microbial infection. METHODS AND RESULTS:It was found that pretreatment of mouse skin with microneedles allowed permeation of solid lipid nanoparticles, size 230 nm, with ovalbumin conjugated on their surface. Transcutaneous immunization in a mouse skin area pretreated with microneedles with ovalbumin nanoparticles induced a stronger antiovalbumin antibody response than using ovalbumin alone. The dose of ovalbumin antigen determined whether microneedle-mediated transcutaneous immunization with ovalbumin nanoparticles induced a stronger immune response than subcutaneous injection of the same ovalbumin nanoparticles. Microneedle treatment permitted skin permeation of live Escherichia coli, but the extent of the permeation was not greater than that enabled by hypodermic injection. CONCLUSION:Transcutaneous immunization on a microneedle-treated skin area with antigens carried by nanoparticles can potentially induce a strong immune response, and the risk of bacterial infection associated with microneedle treatment is no greater than that with a hypodermic injection. 10.2147/IJN.S20413
    A model for the easy assessment of pressure-dependent damage to retinal ganglion cells using cyan fluorescent protein-expressing transgenic mice. Tsuruga Hidekazu,Murata Hiroshi,Araie Makoto,Aihara Makoto Molecular vision PURPOSE:To establish an animal model for the easy assessment of pressure-dependent damage to retinal ganglion cells (RGCs) using the B6.Cg-TgN(Thy1-CFP)23Jrs/J transgenic mouse strain (CFP mouse), which expresses cyan fluorescent protein (CFP) in RGCs, and to evaluate pressure-dependent RGC death. METHODS:In 20 CFP mice, right eyes were selected to receive laser-induced ocular hypertension eye and the contralateral eyes remained untouched to serve as controls. Intraocular pressure (IOP) was measured each week in both eyes using the microneedle method up to 8 weeks. Based on the line plot of time (x) and IOP (y) in laser-treated and control eyes, the area surrounded by both lines (∫ΔIOP(y) dx) was calculated as a surrogate value of the pressure insult. At 9 weeks, eyes were enucleated and RGCs expressing CFP were evaluated histologically in retinal whole mounts. The correlation between pressure insult and RGC density was evaluated in the whole eye, three concentric regions, and four quadrants. RESULTS:Laser-treated eyes showed a significantly higher IOP than control eyes from 1 to 7 weeks (p<0.01). The pressure insult and the RGC density showed a significant negative correlation (y=-0.070x+97.2, r=0.75, p=0.0008). Moreover, the central, middle, and peripheral areas measured from the optic disc and each of four retinal quadrant areas also showed significant negative correlations. Our data demonstrate that each retinal area was almost evenly damaged by IOP elevation. CONCLUSIONS:Laser photocoagulation causes a chronic elevation of IOP in CFP mice. The use of CFP mice enabled us to easily evaluate pressure-dependent RGC damage. This glaucomatous CFP mouse model may contribute to the molecular analysis of neurodegeneration and the development of neuroprotective drugs for glaucoma with a great increase in experimental efficiency.
    Transdermal insulin application system with dissolving microneedles. Ito Yukako,Nakahigashi Takuya,Yoshimoto Naoko,Ueda Yuriko,Hamasaki Noriyuki,Takada Kanji Diabetes technology & therapeutics BACKGROUND:The aim of this report was to develop a dissolving microneedle (DM) application system, where 225-300 insulin-loaded DMs were formed on a chip. After the heat-sealed sheet is removed, the system covered with the press-through package layer is put on the skin. By pressing with the hand, insulin DMs were inserted into the skin. MATERIALS AND METHODS:Factors affecting the penetration depth of DM were studied using applicator in vitro and in vivo experiments. The penetration depth was determined for rat and human skin. Two-layered DM array chips were prepared to obtain complete absorption of insulin and administered to the rat abdominal skin. Plasma glucose levels were measured for 6 h. By comparing the hypoglycemic effect with that obtained after subcutaneous injection, relative pharmacological availability (RPA) was determined. RESULTS:The penetration depth increased from 21 ± 3 μm to 63 ± 2 μm in proportion to application speed to isolated rat skin, at 0.8-2.2 m/s. Human skin showed similar results in the penetration depth. The in vivo penetration depth was dependent on the force (0.5-2.5 N) and duration (1-10 min), as the secondary application force. The penetration depth was 211 ± 3 μm with a duration of 3 min in the in vivo rat experiment. DM array chips having an insulin-loaded space of 181.2 ± 4.2 and 209 ± 3.9 μm were evaluated in the rat. RPA values of insulin from DMs were 98.1 ± 0.8% and 98.1 ± 3.1%, respectively. CONCLUSIONS:These results suggest the usefulness of the two-layered DM application system for the transdermal delivery of insulin. 10.1089/dia.2012.0096
    Mechanical strengthening of fiberoptic microneedles using an elastomeric support. Kosoglu Mehmet A,Hood R Lyle,Rylander Christopher G Lasers in surgery and medicine BACKGROUND AND OBJECTIVES:Microneedles made from silica fiberoptics permit transmission and collection of light, which is an important functional advantage over metal or silicon microneedles. This added functionality may enhance or even enable new percutaneous light-based clinical diagnostic and therapeutic procedures. Micron-diameter fiberoptic microneedles, created from solid fibers capable of light emission and detection, are designed to penetrate several millimeters into tissue while minimizing tissue invasion and disruption. The mechanical strength (critical buckling force) of high aspect ratio (length to diameter) microneedles is a potential problem, which has motivated our invention of an elastomeric support device. In this study, we have tested our hypothesis that embedding the microneedles in an elastomeric support medium may increase microneedle critical buckling force. MATERIALS AND METHODS:The critical buckling force of silica microneedles with 55, 70, and 110 µm diameters and 3 mm lengths were measured with and without a surrounding elastomeric support (PDMS, polydimethylsiloxane). These experimental results were compared to theoretical calculations generated by the Rayleigh-Ritz buckling model. The insertion force required to penetrate ex vivo porcine skin was measured for microneedles with 55 and 70 µm diameters. RESULTS:Use of the PDMS support increased critical buckling force for microneedles of 55, 70, and 110 µm diameters by an average of 610%, 290%, and 33%, respectively. Theoretical calculations by the Rayleigh-Ritz model consistently overestimated the experimentally determined strengthening, but correlated highly with the greater enhancement offered to thinner microneedles. Aided by mechanical strengthening, microneedles 55 µm in diameter were able to repeatedly penetrate. CONCLUSIONS:The critical buckling force of microneedles can be increased substantially to allow extremely high-aspect ratio microneedles, 55-110 µm in diameter and 3 mm in length, to penetrate ex vivo porcine skin. By this strengthening method, the safety and reliability of microneedles in potential clinical applications can be considerably enhanced. 10.1002/lsm.22026
    In vivo iontophoretic delivery of salmon calcitonin across microporated skin. Vemulapalli Viswatej,Bai Yun,Kalluri Haripriya,Herwadkar Anushree,Kim Hyun,Davis Shawn P,Friden Phil M,Banga Ajay K Journal of pharmaceutical sciences The purpose of this study was to determine the effect of microneedle (MN) technology and its combination with iontophoresis (ITP) on the in vivo transdermal delivery of salmon calcitonin (sCT). Maltose MNs (500 µm) were used to porate skin prior to application of the drug, with or without ITP. Micropores created by maltose MNs were characterized by histological sectioning and calcein imaging studies, which indicated uniformity of the created micropores. In vivo studies were performed in hairless rats to assess the degree of enhancement achieved by ITP (0.2 mA/cm² for 1 h), MNs (81 MNs), and their combination. In vivo studies indicate a serum maximal concentration of 0.61 ± 0.42 ng/mL, 1.79 ± 0.72 ng/mL, and 5.51 ± 0.32 ng/mL for ITP, MNs, and combination treatment, respectively. MN treatment alone increased serum concentration 2.5-fold and the combination treatment increased the concentration ninefold as compared with iontophoretic treatment alone. Combination treatment of ITP and MNs resulted in the highest delivery of sCT and therapeutic levels were achieved within 5 min of administration. 10.1002/jps.23222
    Laser-engineered dissolving microneedles for active transdermal delivery of nadroparin calcium. Gomaa Yasmine A,Garland Martin J,McInnes Fiona,El-Khordagui Labiba K,Wilson Clive,Donnelly Ryan F European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V There is an urgent need to replace the injection currently used for low molecular weight heparin (LMWH) multidose therapy with a non- or minimally invasive delivery approach. In this study, laser-engineered dissolving microneedle (DMN) arrays fabricated from aqueous blends of 15% w/w poly(methylvinylether-co-maleic anhydride) were used for the first time in active transdermal delivery of the LMWH nadroparin calcium (NC). Importantly, an array loading of 630IU of NC was achieved without compromising the array mechanical strength or drug bioactivity. Application of NC-DMNs to dermatomed human skin (DHS) using the single-step 'poke and release' approach allowed permeation of approximately 10.6% of the total NC load over a 48-h study period. The cumulative amount of NC that permeated DHS at 24h and 48h attained 12.28±4.23IU/cm(2) and 164.84±8.47IU/cm(2), respectively. Skin permeation of NC could be modulated by controlling the DMN array variables, such as MN length and array density as well as application force to meet various clinical requirements including adjustment for body mass and renal function. NC-loaded DMN offers great potential as a relatively low-cost functional delivery system for enhanced transdermal delivery of LMWH and other macromolecules. 10.1016/j.ejpb.2012.07.008
    Rapid local anesthesia in humans using minimally invasive microneedles. Gupta Jyoti,Denson Donald D,Felner Eric I,Prausnitz Mark R The Clinical journal of pain OBJECTIVE:This study tested the hypothesis that minimally invasive microneedles cause less pain during injection of lidocaine, but induce local anesthesia in humans with the same rapid onset and efficacy as intradermal lidocaine injection using hypodermic needles. METHODS:This study was a randomized, single-blinded, within participants, controlled design. Hollow, 500-μm long microneedles were used to inject lidocaine to the forearm of 15 human participants. The associated pain was recorded using a visual analog (VAS) scale. The area and depth of numbness were determined at 0, 7.5, and 15 minutes after injection. Lidocaine was also injected to the dorsum of the hand near a vein, followed by placement of an intravenous catheter and measurement of associated pain. A 26-gauge intradermal bevel hypodermic needle similarly administered lidocaine on the opposite forearm/hand to serve as the positive control. RESULTS:VAS pain scores revealed that injection using microneedles was significantly less painful than hypodermic needles for both the forearm and dorsum of the hand injections. However, there was no significant difference in the area or depth of the resulting numbness between the 2 treatment methods at any time point (0, 7.5, and 15 min) indicating that microneedles had immediate onset and were as effective as hypodermic needles in inducing dermal anesthesia. Moreover, insertion of an intravenous catheter immediately after lidocaine injection on the dorsum of the hand led to comparable pain scores for the microneedle and hypodermic needle treated sites, further confirming efficacy of microneedles in inducing rapid local anesthesia. Lastly, 77% of the participants preferred microneedles and 80% indicated that they did not consider microneedles to be painful. DISCUSSION:This study demonstrates for the first time that microneedle-based lidocaine injection is as rapid and as effective as hypodermic injection in inducing local anesthesia while resulting in significantly less pain during injection. 10.1097/AJP.0b013e318225dbe9
    A minimally invasive jet injector for intravitreal and subconjunctival injection. Peyman Gholam A,Hosseini Kamran,Cormier Michel Ophthalmic surgery, lasers & imaging : the official journal of the International Society for Imaging in the Eye BACKGROUND AND OBJECTIVE:To evaluate a minimally invasive injector for intravitreal and subconjunctival administration of medications. MATERIALS AND METHODS:The device has a microneedle that communicates with an internal formulation chamber. A piercing depth-limiting flange restricts microneedle penetration to a depth of less than 1 mm and defines the location of the pars plana from the limbus. The jet injector creates a force of up to 1,000 psi, forcing the medication through the remaining sclera/choroid thickness. The device was tested in 28 enucleated rabbit eyes and 9 experimental and 4 control rabbit eyes to define jet pressure for subconjunctival and intravitreal injection. RESULTS:Injection pressures of 76 to 156 psi were needed for subconjunctival injection and 974 psi for intravitreal injection. Clinical and histologic examinations did not reveal damage to intraocular structures. CONCLUSION:The semi-automated jet injector facilitated intravitreal/subconjunctival injection. The microneedle-assisted jet injector minimized the risk of wet injection by anchoring the microneedle in the sclera. 10.3928/15428877-20111129-05
    Releasable layer-by-layer assembly of stabilized lipid nanocapsules on microneedles for enhanced transcutaneous vaccine delivery. DeMuth Peter C,Moon James J,Suh Heikyung,Hammond Paula T,Irvine Darrell J ACS nano Here we introduce a new approach for transcutaneous drug delivery, using microneedles coated with stabilized lipid nanocapsules, for delivery of a model vaccine formulation. Poly(lactide-co-glycolide) microneedle arrays were coated with multilayer films via layer-by-layer assembly of a biodegradable cationic poly(β-amino ester) (PBAE) and negatively charged interbilayer-cross-linked multilamellar lipid vesicles (ICMVs). To test the potential of these nanocapsule-coated microneedles for vaccine delivery, we loaded ICMVs with a protein antigen and the molecular adjuvant monophosphoryl lipid A. Following application of microneedle arrays to the skin of mice for 5 min, (PBAE/ICMV) films were rapidly transferred from microneedle surfaces into the cutaneous tissue and remained in the skin following removal of the microneedle arrays. Multilayer films implanted in the skin dispersed ICMV cargos in the treated tissue over the course of 24 h in vivo, allowing for uptake of the lipid nanocapsules by antigen presenting cells in the local tissue and triggering their activation in situ. Microneedle-mediated transcutaneous vaccination with ICMV-carrying multilayers promoted robust antigen-specific humoral immune responses with a balanced generation of multiple IgG isotypes, whereas bolus delivery of soluble or vesicle-loaded antigen via intradermal injection or transcutaneous vaccination with microneedles encapsulating soluble protein elicited weak, IgG(1)-biased humoral immune responses. These results highlight the potential of lipid nanocapsules delivered by microneedles as a promising platform for noninvasive vaccine delivery applications. 10.1021/nn302639r
    Microneedles 2012. Broderick Kate E Therapeutic delivery The second international conference on Microneedles was held on 13-15 May 2012 in Cork, Republic of Ireland, following on from a successful first meeting at the Georgia Institute of Technology (GA, USA) in May 2010. The meeting showcased the latest international developments in microneedle technology and applications. The gathering provided a platform to facilitate interdisciplinary communications and new collaborations for delegates from academic, industrial and clinical backgrounds. The meeting opened with a half-day short course on microneedle technology and applications, followed by invited lectures and poster presentations over 2 days, divided into sessions such as 'Design and technology--solid and hollow microneedles', 'Vaccine delivery' and 'Drug delivery'. This conference report summarizes the keynote and invited speaker lectures from leaders in the field such as Mark Prausnitz (Georgia Institute of Technology) and Mark Kendall (University of Queensland, Australia). 10.4155/tde.12.72
    Naltrexone salt selection for enhanced transdermal permeation through microneedle-treated skin. Milewski Mikolaj,Pinninti Raghotham R,Stinchcomb Audra L Journal of pharmaceutical sciences The passive delivery rate of naltrexone (NTX) through intact skin is too slow to achieve therapeutic plasma levels in humans from a reasonably sized transdermal patch. A physical enhancement method--microneedles (MNs)--has been shown to afford a substantial increase in the percutaneous flux of NTX hydrochloride in vitro. However, for better therapeutic effect and decrease in the transdermal patch area, further enhancement is desired. The purpose of this study was to identify a NTX salt that would (1) provide elevated in vitro percutaneous drug transport across MN-treated skin as compared with that of the NTX hydrochloride and (2) prove nonirritating to the skin in vivo. The pH-solubility profiles of NTX salts were investigated with three drug salts showing improved solubility at physiologically relevant skin surface pH of 5.0. The skin-irritation potential of NTX glycolate and lactate gels was not greater than that of placebo gel in the guinea pig model. Additionally, in vitro diffusion studies indicated that NTX glycolate provides around 50% enhancement in the flux through MN-treated skin at the cost of doubling the drug concentration in the donor solution. Overall, a new NTX glycolate salt appears to be a promising candidate for MN-assisted transdermal drug delivery system. 10.1002/jps.23189
    Hollow microneedle-based sensor for multiplexed transdermal electrochemical sensing. Miller Philip R,Skoog Shelby A,Edwards Thayne L,Wheeler David R,Xiao Xiaoyin,Brozik Susan M,Polsky Ronen,Narayan Roger J Journal of visualized experiments : JoVE The development of a minimally invasive multiplexed monitoring system for rapid analysis of biologically-relevant molecules could offer individuals suffering from chronic medical conditions facile assessment of their immediate physiological state. Furthermore, it could serve as a research tool for analysis of complex, multifactorial medical conditions. In order for such a multianalyte sensor to be realized, it must be minimally invasive, sampling of interstitial fluid must occur without pain or harm to the user, and analysis must be rapid as well as selective. Initially developed for pain-free drug delivery, microneedles have been used to deliver vaccines and pharmacologic agents (e.g., insulin) through the skin. Since these devices access the interstitial space, microneedles that are integrated with microelectrodes can be used as transdermal electrochemical sensors. Selective detection of glucose, glutamate, lactate, hydrogen peroxide, and ascorbic acid has been demonstrated using integrated microneedle-electrode devices with carbon fibers, modified carbon pastes, and platinum-coated polymer microneedles serving as transducing elements. This microneedle sensor technology has enabled a novel and sophisticated analytical approach for in situ and simultaneous detection of multiple analytes. Multiplexing offers the possibility of monitoring complex microenvironments, which are otherwise difficult to characterize in a rapid and minimally invasive manner. For example, this technology could be utilized for simultaneous monitoring of extracellular levels of, glucose, lactate and pH, which are important metabolic indicators of disease states (e.g., cancer proliferation) and exercise-induced acidosis. 10.3791/4067
    The microneedle roller is an effective device for enhancing transdermal drug delivery. Li Kapsok,Yoo Kwang Ho,Byun Hee Jin,Lim Yun Young,Kim Myeung Nam,Hong Hyuck Ki,Choi Yeon Shik,Jo Young Chang,Kim Beom Joon International journal of dermatology 10.1111/j.1365-4632.2010.04703.x
    Diclofenac delays micropore closure following microneedle treatment in human subjects. Brogden Nicole K,Milewski Mikolaj,Ghosh Priyanka,Hardi Lucia,Crofford Leslie J,Stinchcomb Audra L Journal of controlled release : official journal of the Controlled Release Society Drugs absorbed poorly through the skin are commonly delivered via injection with a hypodermic needle, which is painful and increases the risk of transmitting infectious diseases. Microneedles (MNs) selectively and painlessly permeabilize the outermost skin layer, allowing otherwise skin-impermeable drugs to cross the skin through micron-sized pores and reach therapeutic concentrations. However, rapid healing of the micropores prevents further drug delivery, blunting the clinical utility of this unique transdermal technique. We present the first human study demonstrating that micropore lifetime can be extended following MN treatment. Subjects received one-time MN treatment and daily topical application of diclofenac sodium. Micropore closure was measured with impedance spectroscopy, and area under the admittance-time curve (AUC) was calculated. AUC was significantly higher at MN+diclofenac sodium sites vs. placebo, suggesting slower rates of micropore healing. Colorimetry measurements confirmed the absence of local erythema and irritation. This mechanistic human proof-of-concept study demonstrates that micropore lifetime can be prolonged with simple topical administration of a non-specific cyclooxygenase inhibitor, suggesting the involvement of subclinical inflammation in micropore healing. These results will allow for longer patch wear time with MN-enhanced delivery, thus increasing patient compliance and expanding the transdermal field to a wider variety of clinical conditions. 10.1016/j.jconrel.2012.08.015
    Adjuvants to prolong the local anesthetic effects of coated microneedle products. Zhang Ying,Siebenaler Kris,Brown Ken,Dohmeier Daniel,Hansen Kris International journal of pharmaceutics The objective of this study was to identify an adjuvant for anesthetics coated on microneedles to provide rapid onset and prolonged analgesic action with minimal skin tissue reaction. Aqueous lidocaine or prilocaine formulations with or without clonidine or the related analogs, guanfacine and apraclonidine, were dip-coated onto polymeric microneedles. The amount of lidocaine or prilocaine coated onto the microneedles was assessed by high performance liquid chromatography (HPLC). Delivery efficiency and dermal pharmacokinetics associated with lidocaine or prilocaine delivered via the microneedles were characterized in vivo using domestic swine. Skin punch biopsies were collected and analyzed to determine the anesthetic concentrations in the skin using HPLC-mass spectrometry (LC-MS). Addition of clonidine to the formulations decreased the systemic absorption rate of the anesthetics from the patch application site without impacting the coating performance or the rapid onset of anesthesia. Formulations with 0.3 wt.% clonidine, identified as the optimal dose for lidocaine-delivery via microneedles, maintained the lidocaine skin concentration above the estimated therapeutic level (100 ng/mg) for 1 h without causing any skin irritation or color change. The other two clonidine analogs, guanfacine and apraclonidine, also led to delayed systemic absorption of lidocaine from the skin, indicating utility in providing prolonged analgesia. 10.1016/j.ijpharm.2012.09.041
    Multiplexed microneedle-based biosensor array for characterization of metabolic acidosis. Miller Philip R,Skoog Shelby A,Edwards Thayne L,Lopez Deanna M,Wheeler David R,Arango Dulce C,Xiao Xiaoyin,Brozik Susan M,Wang Joseph,Polsky Ronen,Narayan Roger J Talanta The development of a microneedle-based biosensor array for multiplexed in situ detection of exercise-induced metabolic acidosis, tumor microenvironment, and other variations in tissue chemistry is described. Simultaneous and selective amperometric detection of pH, glucose, and lactate over a range of physiologically relevant concentrations in complex media is demonstrated. Furthermore, materials modified with a cell-resistant (Lipidure(®)) coating were shown to inhibit macrophage adhesion; no signs of coating delamination were noted over a 48-h period. 10.1016/j.talanta.2011.11.046
    Antigen-loaded dissolving microneedle array as a novel tool for percutaneous vaccination. Naito Seishiro,Ito Yukako,Kiyohara Tomoko,Kataoka Michiyo,Ochiai Masaki,Takada Kanji Vaccine Antigen-loaded dissolving microneedle array (dMNA) patches were investigated as novel systems for vaccine delivery into the skin, where immuno-competent dendritic cells are densely distributed. We fabricated micron-scale needles arrayed on patches, using chondroitin sulfate mixed with a model antigen, ovalbumin. Insertion of dMNA effectively delivered substantial amounts of ovalbumin into the skin within 3 min and induced robust antigen-specific antibody responses in the sera of mice. The antibody dose-response relationship showed that the efficiency of dMNA patch immunization was comparable to that of conventional intradermal injections. Thus, Antigen-loaded dMNA patches are a promising antigen-delivery system for percutaneous vaccination. 10.1016/j.vaccine.2011.11.111
    FIB preparation and SEM investigations for three-dimensional analysis of cell cultures on microneedle arrays. Friedmann A,Cismak A,Tautorat C,Koester P J,Baumann W,Held J,Gaspar J,Ruther P,Paul O,Heilmann A Scanning We report the investigation of the interfaces between microneedle arrays and cell cultures in patch-on-chip systems by using Focused Ion Beam (FIB) preparation and Scanning Electron Microscopy (SEM). First, FIB preparations of micro chips are made to determine the size and shape of the designed microneedles. In this essay, we investigate the cell-substrate interaction, especially the cell adhesion, and the microneedle's potential cell penetration. For this purpose, cross-sectional preparation of these hard/soft hybrid structures is performed by the FIB technology. By applying the FIB technology followed by high-resolution imaging with SEM, new insights into the cell-substrate interface can be received. One can clearly distinguish between cells that are only in contact with microneedles and cells that are penetrated by microneedles. A stack of slice images is collected by the application of the slice-and-view setup during FIB preparation and is used for three-dimensional reconstruction of cells and micro-needles. 10.1002/sca.20297
    A split-face comparison of a fractional microneedle radiofrequency device and fractional carbon dioxide laser therapy in acne patients. Shin Jung U,Lee Soo Hyun,Jung Jin Young,Lee Ju Hee Journal of cosmetic and laser therapy : official publication of the European Society for Laser Dermatology BACKGROUND:A number of lasers and light-based devices have been reported as promising treatment options for acne vulgaris. OBJECTIVE:To evaluate the efficacy and safety of fractional microneedle radiofrequency (MRF) device treatment compared to CO(2) fractional laser system (FS) for the treatment of acne vulgaris. METHODS:Twenty healthy subjects underwent full-face treatment for acne vulgaris with CO(2) FS and MRF device. For each subject, two passes of CO(2) FS with a pulse energy setting of 80 mJ and a density of 100 spots/cm(2) were used on one side, and two passes of MRF device with a intensity of 8, density of 25 MTZ/cm(2), and a depth of 1.5-2.5 mm were used on the other. Patients were evaluated 3 months postoperatively and were also photographed. RESULTS:Most of the patients improved based on clinical and photographic assessments 3 months after the treatment. No significant differences in physician-measured parameters, patient ratings, or intraoperative pain ratings were found, although downtime was significantly longer for the CO(2) FS treated side. CONCLUSIONS:MRF device and CO(2) FS can be used for acne vulgaris patients and MRF device is more convenient than CO(2) FS because of its short downtime. 10.3109/14764172.2012.720023
    Effect of microneedle treatment on the skin permeation of a nanoencapsulated dye. Gomaa Yasmine A,El-Khordagui Labiba K,Garland Martin J,Donnelly Ryan F,McInnes Fiona,Meidan Victor M The Journal of pharmacy and pharmacology OBJECTIVES:The aim of the study was to investigate the effect of microneedle (MN) pretreatment on the transdermal delivery of a model drug (Rhodamine B, Rh B) encapsulated in polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) focusing on the MN characteristics and application variables. METHODS:Gantrez MNs were fabricated using laser-engineered silicone micro-mould templates. PLGA NPs were prepared using a modified emulsion-diffusion-evaporation method and characterised in vitro. Permeation of encapsulated Rh B through MN-treated full thickness porcine skin was performed using Franz diffusion cells with appropriate controls. KEY FINDINGS:In-vitro skin permeation of the nanoencapsulated Rh B (6.19 ± 0.77 µg/cm²/h) was significantly higher (P < 0.05) compared with the free solution (1.66 ± 0.53 µg/cm²/h). Mechanistic insights were supportive of preferential and rapid deposition of NPs in the MN-created microconduits, resulting in accelerated dye permeation. Variables such as MN array configuration and application mode were shown to affect transdermal delivery of the nanoencapsulated dye. CONCLUSIONS:This dual MN/NP-mediated approach offers potential for both the dermal and transdermal delivery of therapeutic agents with poor passive diffusion characteristics. 10.1111/j.2042-7158.2012.01557.x
    Microneedle assisted iontophoretic transdermal delivery of prochlorperazine edisylate. Kolli Chandra Sekhar,Xiao Jin,Parsons Daniel L,Babu R Jayachandra Drug development and industrial pharmacy This paper investigates the microneedle (MN) mediated in vitro transdermal iontophoretic delivery of prochlorperazine edisylate (PE) across dermatomed human skin. The Dermaroller™ induced microchannels were visualized using methylene blue staining and scanning electron microscopy. In vitro skin permeation studies were performed using vertical static Franz diffusion cells. Iontophoretic protocols involved application of direct current at a density of 0.4 mA/cm(2) using Ag as an anode and Ag/AgCl as a cathode. The effect of PE concentration (20, 50 and 100 mg/mL), number of passes of microneedles (0, 5, 10 and 20) on both iontophoretic and passive delivery of PE was studied. The Dermarollertm was found to successfully breach the skin barrier and a linear relationship (r(2) = 0.99) was observed between the number of passes of the Dermaroller™ and the number of microchannels created. Passive transdermal flux of PE (0.060 ± 0.003 µg/cm(2)/h) at 50 mg/mL donor PE concentration) was low and increased (4.15 ± 0.57 µg/cm(2)/h) with the application of direct current. Application of iontophoresis in conjunction with microneedle pre-treatment resulted in enhanced flux (4.90 ± 0.39 µg/cm(2)/h at 50 mg/mL donor PE concentration) of PE. The projected transdermal PE flux indicates that a 9 cm(2) patch could deliver PE in a sufficient amount to maintain therapeutic levels of the drug. In conclusion, microneedles when used in conjunction with iontophoresis significantly enhanced the transdermal delivery of PE and it may be feasible to develop an iontophoretic transdermal patch that could be integrated with MN. 10.3109/03639045.2011.617753
    Increased immunogenicity of avian influenza DNA vaccine delivered to the skin using a microneedle patch. Kim Yeu-Chun,Song Jae-Min,Lipatov Aleksandr S,Choi Seong-O,Lee Jeong Woo,Donis Ruben O,Compans Richard W,Kang Sang-Moo,Prausnitz Mark R European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V Effective public health responses to an influenza pandemic require an effective vaccine that can be manufactured and administered to large populations in the shortest possible time. In this study, we evaluated a method for vaccination against avian influenza virus that uses a DNA vaccine for rapid manufacturing and delivered by a microneedle skin patch for simplified administration and increased immunogenicity. We prepared patches containing 700-μm long microneedles coated with an avian H5 influenza hemagglutinin DNA vaccine from A/Viet Nam/1203/04 influenza virus. The coating DNA dose increased with DNA concentration in the coating solution and the number of dip-coating cycles. Coated DNA was released into the skin tissue by dissolution within minutes. Vaccination of mice using microneedles induced higher levels of antibody responses and hemagglutination inhibition titers, and improved protection against lethal infection with avian influenza as compared to conventional intramuscular delivery of the same dose of the DNA vaccine. Additional analysis showed that the microneedle coating solution containing carboxymethylcellulose and a surfactant may have negatively affected the immunogenicity of the DNA vaccine. Overall, this study shows that DNA vaccine delivery by microneedles can be a promising approach for improved vaccination to mitigate an influenza pandemic. 10.1016/j.ejpb.2012.03.010
    Microneedle-mediated transcutaneous immunization with plasmid DNA coated on cationic PLGA nanoparticles. Kumar Amit,Wonganan Piyanuch,Sandoval Michael A,Li Xinran,Zhu Saijie,Cui Zhengrong Journal of controlled release : official journal of the Controlled Release Society Previously, it was shown that microneedle-mediated transcutaneous immunization with plasmid DNA can potentially induce a stronger immune response than intramuscular injection of the same plasmid DNA. In the present study, we showed that the immune responses induced by transcutaneous immunization by applying plasmid DNA onto a skin area pretreated with solid microneedles were significantly enhanced by coating the plasmid DNA on the surface of cationic nanoparticles. In addition, the net surface charge of the DNA-coated nanoparticles significantly affected their in vitro skin permeation and their ability to induce immune responses in vivo. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles elicited a stronger immune response than with plasmid DNA-coated net negatively charged nanoparticles or by intramuscular immunization with plasmid DNA alone. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles induced comparable immune responses as intramuscular injection of them, but transcutaneous immunization was able to induce specific mucosal immunity and a more balanced T helper type 1 and type 2 response. The ability of the net positively charged DNA-coated nanoparticles to induce a strong immune response through microneedle-mediated transcutaneous immunization may be attributed to their ability to increase the expression of the antigen gene encoded by the plasmid and to more effectively stimulate the maturation of antigen-presenting cells. 10.1016/j.jconrel.2012.08.011
    Chitosan microneedle patches for sustained transdermal delivery of macromolecules. Chen Mei-Chin,Ling Ming-Hung,Lai Kuan-Ying,Pramudityo Esar Biomacromolecules This paper introduces a chitosan microneedle patch for efficient and sustained transdermal delivery of hydrophilic macromolecules. Chitosan microneedles have sufficient mechanical strength to be inserted in vitro into porcine skin at approximately 250 μm in depth and in vivo into rat skin at approximately 200 μm in depth. Bovine serum albumin (BSA, MW=66.5 kDa) was used as a model protein to explore the potential use of chitosan microneedles as a transdermal delivery device for protein drugs. In vitro drug release showed that chitosan microneedles can provide a sustained release of BSA for at least 8 days (approximately 95% of drugs released in 8 days). When the Alexa Fluor 488-labeled BSA (Alexa 488-BSA)-loaded microneedles were applied to the rat skin in vivo, confocal microscopic images showed that BSA can gradually diffuse from the puncture sites to the dermal layer and the fluorescence of Alexa 488-BSA can be observed at the depth of 300 μm. In addition, encapsulation of BSA within the microneedle matrix did not alter the secondary structure of BSA, indicating that the gentle nature of the fabrication process allowed for encapsulation of fragile biomolecules. These results suggested that the developed chitosan microneedles may serve as a promising device for transdermal delivery of macromolecules in a sustained manner. 10.1021/bm301293d
    Microneedle pretreatment enhances the percutaneous permeation of hydrophilic compounds with high melting points. Stahl Jessica,Wohlert Mareike,Kietzmann Manfred BMC pharmacology & toxicology BACKGROUND:Two commercially available microneedle rollers with a needle length of 200 μm and 300 μm were selected to examine the influence of microneedle pretreatment on the percutaneous permeation of four non-steroidal anti-inflammatory drugs (diclofenac, ibuprofen, ketoprofen, paracetamol) with different physicochemical drug characteristics in Franz-type diffusion cells. Samples of the receptor fluids were taken at predefined times over 6 hours and were analysed by UV-VIS high-performance liquid-chromatography. Histological examinations after methylene blue application were additionally performed to gather information about barrier disruption. RESULTS:Despite no visible pores in the stratum corneum, the microneedle pretreatment resulted in a twofold (200 μm) and threefold higher (300 μm) flux through the pretreated skin samples compared to untreated skin samples for ibuprofen and ketoprofen (LogK(ow) > 3, melting point < 100°C). The flux of the hydrophilic compounds diclofenac and paracetamol (logK(ow) < 1, melting point > 100°C) increased their amount by four (200 μm) to eight (300 μm), respectively. CONCLUSION:Commercially available microneedle rollers with 200-300 μm long needles enhance the drug delivery of topically applied non-steroidal anti-inflammatory drugs and represent a valuable tool for percutaneous permeation enhancement particularly for substances with poor permeability due to a hydrophilic nature and high melting points. 10.1186/2050-6511-13-5
    Use of fractionated microneedle radiofrequency for the treatment of inflammatory acne vulgaris in 18 Korean patients. Lee Sang Ju,Goo Ja Woong,Shin Jaeyong,Chung Won Soon,Kang Jin Moon,Kim Young Koo,Cho Sung Bin Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.] BACKGROUND:Nonablative radiofrequency (RF) devices have been shown to be clinically effective for the treatment of moderate to severe acne lesions. OBJECTIVE:To evaluate the efficacy and safety of a fractionated microneedle RF device in the treatment of inflammatory acne vulgaris. METHODS:Eighteen patients (15 male, 3 female; mean age 27, range: 19-33; Fitzpatrick skin type IV) with moderate to severe acne vulgaris who were treated with two sessions of fractionated microneedle RF at 1-month intervals were enrolled in this study. RESULTS:Evaluation of improvement, which took into account number of inflammatory acne lesions, showed that two of the 18 patients had grade 4 clinical improvement, eight had grade 3 improvement, and six had grade 2 improvement. Improvement scores in terms of lesion severity were also evaluated. One of the 18 patients had grade 4 clinical improvement, eight grade 3, and seven grade 2. No patient had worsening of inflammatory acne lesions. CONCLUSION:Fractionated microneedle RF can have a positive therapeutic effect on inflammatory acne vulgaris and related scars. In addition, this technique does not worsen active acne lesions. 10.1111/j.1524-4725.2011.02267.x
    Local response to microneedle-based influenza immunization in the skin. del Pilar Martin Maria,Weldon William C,Zarnitsyn Vladimir G,Koutsonanos Dimitrios G,Akbari Hamed,Skountzou Ioanna,Jacob Joshy,Prausnitz Mark R,Compans Richard W mBio UNLABELLED:Microneedle patches (MN) provide a novel method of vaccine delivery to the skin with the objective of targeting the large network of resident antigen-presenting cells to induce an efficient immune response. Our previous reports demonstrated that cutaneous delivery of inactivated influenza virus-coated MN to mice protects against lethal infection. Protection is correlated with sustained levels of anti-influenza virus serum antibodies, hemagglutination inhibition titers, and robust cellular responses that are often stronger than those generated by intramuscular vaccination. Here we dissect the early events occurring in murine skin after microneedle delivery of inactivated influenza virus. We demonstrate correlation of immunization against influenza virus with a local increase of cytokines important for recruitment of neutrophils, monocytes and dendritic cells at the site of immunization. We also observed prolonged antigen deposition, and migration of matured dendritic cells bearing influenza virus antigen from the skin. IMPORTANCE:The immunological mechanisms by which MN vaccination confers protective immunity are not well understood. The present study provides a first analysis of the early immune events after microneedle-based vaccination. 10.1128/mBio.00012-12
    Transcutaneous immunization using a dissolving microneedle array protects against tetanus, diphtheria, malaria, and influenza. Matsuo Kazuhiko,Hirobe Sachiko,Yokota Yayoi,Ayabe Yurika,Seto Masashi,Quan Ying-Shu,Kamiyama Fumio,Tougan Takahiro,Horii Toshihiro,Mukai Yohei,Okada Naoki,Nakagawa Shinsaku Journal of controlled release : official journal of the Controlled Release Society Transcutaneous immunization (TCI) is an attractive alternative vaccination route compared to the commonly used injection systems. We previously developed a dissolving microneedle array for use as a TCI device, and reported that TCI with the dissolving microneedle array induced an immune response against model antigens. In the present study, we investigated the vaccination efficacy against tetanus and diphtheria, malaria, and influenza using this vaccination system. Our TCI system induced substantial increases in toxoid-specific IgG levels and toxin-neutralizing antibody titer and induced the production of anti-SE36 IgG, which could bind to malaria parasite. On influenza HA vaccination, robust antibody production was elicited in mice that provided complete protection against a subsequent influenza virus challenge. These findings demonstrate that TCI using a dissolving microneedle array can elicit large immune responses against infectious diseases. Based on these results, we are now preparing translational research for human clinical trials. 10.1016/j.jconrel.2012.04.001
    Novel lyophilized hydrogel patches for convenient and effective administration of microneedle-mediated insulin delivery. Qiu Yuqin,Qin Guangjiong,Zhang Suohui,Wu Yan,Xu Bai,Gao Yunhua International journal of pharmaceutics A lyophilized hydrogel patch system was developed for microneedle-mediated insulin delivery. The matrix of Cross-linked poly(acrylamide-co-acrylic acid) were synthesized by precipitation polymerization. Recombinant human Insulin was loaded into the lyophilized polymer matrix, which can be rehydrated by water. After the hydrated patch was applied to the abdominal skin of diabetic rats after microneedle pretreatment, pharmacodynamics and pharmacokinetics evaluation was performed. The blood samples were collected to monitor blood glucose and serum insulin levels for 12 h. Blood glucose was lowered in proportion to the concentration of insulin loaded in lyophilized hydrogel patches (R(2)=0.99), with a longer duration of action compared to subcutaneous injection. Stability study confirmed more than 90% of insulin activity was retained in lyophilized hydrogel after 6 months of storage at 4 °C. In conclusion, hydrogel patches were demonstrated to be appropriate drug reservoir for sustained release of insulin with microneedle mediated transdermal delivery. 10.1016/j.ijpharm.2012.07.035
    Coated microneedle arrays for transcutaneous delivery of live virus vaccines. Vrdoljak Anto,McGrath Marie G,Carey John B,Draper Simon J,Hill Adrian V S,O'Mahony Conor,Crean Abina M,Moore Anne C Journal of controlled release : official journal of the Controlled Release Society Vaccines are sensitive biologics that require continuous refrigerated storage to maintain their viability. The vast majority of vaccines are also administered using needles and syringes. The need for cold chain storage and the significant logistics surrounding needle-and-syringe vaccination is constraining the success of immunization programs. Recombinant live viral vectors are a promising platform for the development of vaccines against a number of infectious diseases, however these viruses must retain infectivity to be effective. Microneedles offer an effective and painless method for delivery of vaccines directly into skin that in the future could provide solutions to current vaccination issues. Here we investigated methods of coating live recombinant adenovirus and modified vaccinia virus Ankara (MVA) vectors onto solid microneedle arrays. An effective spray-coating method, using conventional pharmaceutical processes, was developed, in tandem with suitable sugar-based formulations, which produces arrays with a unique coating of viable virus in a dry form around the shaft of each microneedle on the array. Administration of live virus-coated microneedle arrays successfully resulted in virus delivery, transcutaneous infection and induced an antibody or CD8(+) T cell response in mice that was comparable to that obtained by needle-and-syringe intradermal immunization. To our knowledge, this is the first report of successful vaccination with recombinant live viral vectored vaccines coated on microneedle delivery devices. 10.1016/j.jconrel.2011.12.026
    Microneedle-mediated vaccine delivery: harnessing cutaneous immunobiology to improve efficacy. Al-Zahrani Sharifa,Zaric Marija,McCrudden Cian,Scott Chris,Kissenpfennig Adrien,Donnelly Ryan F Expert opinion on drug delivery INTRODUCTION:Breaching the skin's stratum corneum barrier raises the possibility of the administration of vaccines, gene vectors, antibodies and even nanoparticles, all of which have at least their initial effect on populations of skin cells. AREAS COVERED:Intradermal vaccine delivery holds enormous potential for improved therapeutic outcomes for patients, particularly those in the developing world. Various vaccine-delivery strategies have been employed, which are discussed in this review. The importance of cutaneous immunobiology on the effect produced by microneedle-mediated intradermal vaccination is also discussed. EXPERT OPINION:Microneedle-mediated vaccines hold enormous potential for patient benefit. However, in order for microneedle vaccine strategies to fulfill their potential, the proportion of an immune response that is due to the local action of delivered vaccines on skin antigen-presenting cells, and what is due to a systemic effect from vaccines reaching the systemic circulation, must be determined. Moreover, industry will need to invest significantly in new equipment and instrumentation in order to mass-produce microneedle vaccines consistently. Finally, microneedles will need to demonstrate consistent dose delivery across patient groups and match this to reliable immune responses before they will replace tried-and-tested needle-and-syringe-based approaches. 10.1517/17425247.2012.676038
    Microneedle delivery of plasmid DNA to living human skin: Formulation coating, skin insertion and gene expression. Pearton Marc,Saller Verena,Coulman Sion A,Gateley Chris,Anstey Alexander V,Zarnitsyn Vladimir,Birchall James C Journal of controlled release : official journal of the Controlled Release Society Microneedle delivery of nucleic acids, in particular plasmid DNA (pDNA), to the skin represents a potential new approach for the clinical management of genetic skin diseases and cutaneous cancers, and for intracutaneous genetic immunisation. In this study excised human skin explants were used to investigate and optimise key parameters that will determine stable and effective microneedle-facilitated pDNA delivery. These include (i) high dose-loading of pDNA onto microneedle surfaces, (ii) stability and functionality of the coated pDNA, (iii) skin penetration capability of pDNA-coated microneedles, and (iv) efficient gene expression in human skin. Optimisation of a dip-coating method enabled significant increases in the loading capacity, up to 100μg of pDNA per 5-microneedle array. Coated microneedles were able to reproducibly perforate human skin at low (<1N) insertion forces. The physical stability of the coated pDNA was partially compromised on storage, although this was improved through the addition of saccharide excipients without detriment to the biological functionality of pDNA. The pDNA-coated microneedles facilitated reporter gene expression in viable human skin. The efficiency of gene expression from coated microneedles will depend upon suitable DNA loading, efficient and reproducible skin puncture and rapid in situ dissolution of the plasmid at the site of delivery. 10.1016/j.jconrel.2012.04.005
    Microneedle technologies for (trans)dermal drug and vaccine delivery. van der Maaden Koen,Jiskoot Wim,Bouwstra Joke Journal of controlled release : official journal of the Controlled Release Society Microneedles have been used for the dermal and transdermal delivery of a broad range of drugs, such as small molecular weight drugs, oligonucleotides, DNA, peptides, proteins and inactivated viruses. However, until now there are no microneedle-based (trans)dermal drug delivery systems on the market. In the past decade various types of microneedles have been developed by a number of production processes. Numerous geometries of microneedles have been designed from various materials. These microneedles have been used for different approaches of microneedle-based (trans)dermal drug delivery. Following a brief introduction about dermal and transdermal drug delivery, this review describes different production methods for solid and hollow microneedles as well as conditions that influence skin penetration. Besides, the four microneedle-based (trans)dermal drug delivery approaches are discussed: "poke and flow", "poke and patch", "poke and release", and "coat and poke". A separate section of this review is devoted to the use of microneedles for the delivery of therapeutic proteins and vaccines. Finally, we give our view on research and development that is needed to render microneedle-based (trans)dermal drug delivery technologies clinically useful in the near future. 10.1016/j.jconrel.2012.01.042
    Skin rejuvenation by microneedle fractional radiofrequency treatment in Asian skin; clinical and histological analysis. Seo Kyu Young,Yoon Moon Soo,Kim Dong Hyun,Lee Hee Jung Lasers in surgery and medicine BACKGROUND:For skin rejuvenation, microneedle fractional radiofrequency (RF) is a recently developed minimally invasive method for delivering RF energy directly into the skin using microneedle. OBJECTIVE:We evaluated efficacy and safety of microneedle fractional RF for skin rejuvenation in Asian skin and also conducted immunohistochemical analysis before and after treatment. PATIENTS AND METHODS:Twenty-five females (mean age 54.2, Fitzpatrick skin phototypes III-IV) received three consecutive fractional RF treatment at 4-week intervals. Outcome assessments included standardized photography, physician's global assessment, patient's satisfaction scores, objective biophysical measurements, and histologic analysis including immunohistochemical staining. RESULTS:All patients showed clinical improvement on physician's global assessment and patient's satisfaction scores. Among objective biophysical measurements, improvement in hydration and skin roughness was noticed. Histologic examination revealed marked increase in dermal thickness, dermal collagen content and dermal fibrillin content. Side effects were minimal. LIMITATIONS:The limitations are the small number of patients and lack of long-term follow-up. CONCLUSION:Microneedle fractional RF is a safe and effective skin rejuvenation method in Asians. 10.1002/lsm.22071
    Facial skin barrier function recovery after microneedle transdermal delivery treatment. Han Tae Y,Park Kui Y,Ahn Ji Y,Kim Seo W,Jung Hye J,Kim Beom J Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.] BACKGROUND:Microneedle treatment is currently used in the cosmetic industry for several skin conditions. Despite their extensive use, there is lack of sufficient data on the safety of microneedles. OBJECTIVE:To investigate the degree of acute skin damage and the time required for facial skin barrier function to recover using different microneedle lengths and numbers of applications. MATERIALS AND METHODS:Each side of a volunteer's face was randomly treated with one of the following treatments: five applications of 0.15-mm microneedles, five applications of 0.25-mm microneedles, 10 applications of 0.15-mm microneedles, or 10 applications of 0.25-mm microneedles. Transepidermal water loss, stratum corneum hydration, and skin erythema were measured at baseline, immediately after treatment, 4 hours after treatment, and 8 hours after treatment and at 24-hour intervals for 3 days. RESULTS:Prompt recovery of barrier function (within 72 hours) was observed after microneedle treatment. CONCLUSION:Microneedle treatment is simple and inexpensive, and the skin barrier disruption it causes resolves quickly. Therefore, it can serve as an effective physical method of enhancing transdermal delivery of medications for the treatment of many cosmetic and dermatological conditions. 10.1111/j.1524-4725.2012.02550.x
    Quantifying the mechanical properties of human skin to optimise future microneedle device design. Groves R B,Coulman S A,Birchall J C,Evans S L Computer methods in biomechanics and biomedical engineering Microneedle devices are a promising minimally invasive means of delivering drugs/vaccines across or into the skin. However, there is currently a diversity of microneedle designs and application methods that have, primarily, been intuitively developed by the research community. To enable the rational design of optimised microneedle devices, a greater understanding of human skin biomechanics under small deformations is required. This study aims to develop a representative stratified model of human skin, informed by in vivo data. A multilayer finite element model incorporating the epidermis, dermis and hypodermis was established. This was correlated with a series of in-vivo indentation measurements, and the Ogden material coefficients were optimised using a material parameter extraction algorithm. The finite element simulation was subsequently used to model microneedle application to human skin before penetration and was validated by comparing these predictions with the in-vivo measurements. Our model has provided an excellent tool to predict micron-scale human skin deformation in vivo and is currently being used to inform optimised microneedle designs. 10.1080/10255842.2011.596481
    Intracellular protein delivery and gene transfection by electroporation using a microneedle electrode array. Choi Seong-O,Kim Yeu-Chun,Lee Jeong Woo,Park Jung-Hwan,Prausnitz Mark R,Allen Mark G Small (Weinheim an der Bergstrasse, Germany) The impact of many biopharmaceuticals, including protein- and gene-based therapies, has been limited by the need for better methods of delivery into cells within tissues. Here, intracellular delivery of molecules and transfection with plasmid DNA by electroporation is presented using a novel microneedle electrode array designed for the targeted treatment of skin and other tissue surfaces. The microneedle array is molded out of polylactic acid. Electrodes and circuitry required for electroporation are applied to the microneedle array surface by a new metal-transfer micromolding method. The microneedle array maintains mechanical integrity after insertion into pig cadaver skin and is able to electroporate human prostate cancer cells in vitro. Quantitative measurements show that increasing electroporation pulse voltage increases uptake efficiency of calcein and bovine serum albumin, whereas increasing pulse length has lesser effects over the range studied. Uptake of molecules by up to 50% of cells and transfection of 12% of cells with a gene for green fluorescent protein is demonstrated at high cell viability. It is concluded that the microneedle electrode array is able to electroporate cells, resulting in intracellular uptake of molecules, and has potential applications to improve intracellular delivery of proteins, DNA, and other biopharmaceuticals. 10.1002/smll.201101747
    Erythropoietin-coated ZP-microneedle transdermal system: preclinical formulation, stability, and delivery. Peters Elaine E,Ameri Mahmoud,Wang Xiaomei,Maa Yuh-Fun,Daddona Peter E Pharmaceutical research PURPOSE:To evaluate the feasibility of coating formulated recombinant human erythropoietin alfa (EPO) on a titanium microneedle transdermal delivery system, ZP-EPO, and assess preclinical patch delivery performance. METHODS:Formulation rheology and surface activity were assessed by viscometry and contact angle measurement. EPO liquid formulation was coated onto titanium microneedles by dip-coating and drying. Stability of coated EPO was assessed by SEC-HPLC, CZE and potency assay. Preclinical in vivo delivery and pharmacokinetic studies were conducted in rats with EPO-coated microneedle patches and compared to subcutaneous EPO injection. RESULTS:Studies demonstrated successful EPO formulation development and coating on microneedle arrays. ZP-EPO patch was stable at 25°C for at least 3 months with no significant change in % aggregates, isoforms, or potency. Preclinical studies in rats showed the ZP-EPO microneedle patches, coated with 750 IU to 22,000 IU, delivered with high efficiency (75-90%) with a linear dose response. PK profile was similar to subcutaneous injection of commercial EPO. CONCLUSIONS:Results suggest transdermal microneedle patch delivery of EPO is feasible and may offer an efficient, dose-adjustable, patient-friendly alternative to current intravenous or subcutaneous routes of administration. 10.1007/s11095-012-0674-z
    A low-invasive and effective transcutaneous immunization system using a novel dissolving microneedle array for soluble and particulate antigens. Matsuo Kazuhiko,Yokota Yayoi,Zhai You,Quan Ying-Shu,Kamiyama Fumio,Mukai Yohei,Okada Naoki,Nakagawa Shinsaku Journal of controlled release : official journal of the Controlled Release Society Transcutaneous immunization (TCI) is a promising needle-free, easy-to-use, and low-invasive vaccination method. The hydrogel patch-based TCI system induced immune responses against soluble antigens (Ags) like toxoids, but could not induce immune responses against particulate Ags. Here, as an effective TCI system against every form of Ag, we developed a dissolving microneedle array of three lengths (200, 300, or 800 μm) made of hyaluronate as a novel TCI device. Unlike conventional microneedles, the microneedles of our dissolving microneedle arrays dissolved in the skin after insertion. Each dissolving microneedle array effectively delivered both soluble and particulate Ags under the stratum corneum. TCI using these dissolving microneedle arrays induced effective immune responses in rats regardless of the Ag form that were comparable to conventional vaccination using subcutaneous immunization. In addition, application of these dissolving microneedle arrays caused only slight skin irritation. These findings suggest that our TCI system can simply, safely, and effectively improve protective immune responses for every vaccine Ag. 10.1016/j.jconrel.2012.01.033
    Development of a novel self-dissolving microneedle array of alendronate, a nitrogen-containing bisphosphonate: evaluation of transdermal absorption, safety, and pharmacological effects after application in rats. Katsumi Hidemasa,Liu Shu,Tanaka Yutaro,Hitomi Kaori,Hayashi Rie,Hirai Yuka,Kusamori Kosuke,Quan Ying-shu,Kamiyama Fumio,Sakane Toshiyasu,Yamamoto Akira Journal of pharmaceutical sciences Alendronate is a nitrogen-containing bisphosphonate that is widely used for the treatment of osteoporosis. In this study, we developed a novel self-dissolving micron-size needle array (microneedle array) containing alendronate, which was fabricated by micromodeling technologies using hyaluronic acid as a basic material. Micron-scale pores in the skin were seen after the application of the alendronate-loaded microneedle array, verifying establishment of transdermal pathways for alendronate. The absorption of alendronate after the application of alendronate-loaded microneedle array was almost equivalent to that after subcutaneous administration, and the bioavailability of alendronate was approximately 90% in rats. Furthermore, delivery of alendronate via this strategy effectively suppressed the decrease in the width of the growth plate in a rat model of osteoporosis. Although mild cutaneous irritation was observed after the application of the alendronate-loaded microneedle array, it resolved by day 15. These findings indicate that this alendronate-loaded microneedle array is a promising transdermal formulation for the treatment of osteoporosis. 10.1002/jps.23136
    Microneedle mediated intradermal delivery of adjuvanted recombinant HIV-1 CN54gp140 effectively primes mucosal boost inoculations. Pattani Aditya,McKay Paul F,Garland Martin J,Curran Rhonda M,Migalska Katarzyna,Cassidy Corona M,Malcolm R Karl,Shattock Robin J,McCarthy Helen O,Donnelly Ryan F Journal of controlled release : official journal of the Controlled Release Society Dissolving polymeric microneedle arrays formulated to contain recombinant CN54 HIVgp140 and the TLR4 agonist adjuvant MPLA were assessed for their ability to elicit antigen-specific immunity. Using this novel microneedle system we successfully primed antigen-specific responses that were further boosted by an intranasal mucosal inoculation to elicit significant antigen-specific immunity. This prime-boost modality generated similar serum and mucosal gp140-specific IgG levels to the adjuvanted and systemic subcutaneous inoculations. While the microneedle primed groups demonstrated a balanced Th1/Th2 profile, strong Th2 polarization was observed in the subcutaneous inoculation group, likely due to the high level of IL-5 secretion from cells in this group. Significantly, the animals that received a microneedle prime and intranasal boost regimen elicited a high level IgA response in both the serum and mucosa, which was greatly enhanced over the subcutaneous group. The splenocytes from this inoculation group secreted moderate levels of IL-5 and IL-10 as well as high amounts of IL-2, cytokines known to act in synergy to induce IgA. This work opens up the possibility for microneedle-based HIV vaccination strategies that, once fully developed, will greatly reduce risk for vaccinators and patients, with those in the developing world set to benefit most. 10.1016/j.jconrel.2012.07.039
    The combination of microneedles with electroporation and sonophoresis to enhance hydrophilic macromolecule skin penetration. Petchsangsai Maleenart,Rojanarata Theerasak,Opanasopit Praneet,Ngawhirunpat Tanasait Biological & pharmaceutical bulletin The objective of the present work was to investigate the effects of 3 combinatorial techniques (microneedle (MN), electroporation (EP), and sonophoresis (SN)) on the in vitro skin permeation of the hydrophilic macromolecular compound fluorescein isothiocyanate-dextran (FD-4; molecular weight (MW) 4.4 kDa). Assessment of the in vitro skin permeation of FD-4 was performed in porcine skin. MN, EP, and SN were used as physical enhancement methods, given the potential of their various mechanisms. The total cumulative amount of FD-4 that permeated through treated skin using 2 or 3 combined methods, i.e., MN+EP, MN+SN, EP+SN, and MN+EP+SN, was investigated. Microconduits created by MN alone and in combination with the other techniques were observed under confocal laser scanning microscopy (CLSM). The histology of the treated skin was examined. In vitro skin permeation experiments revealed that the total cumulative amount of FD-4 that permeated porcine skin using 3 combined techniques (MN+EP+SN) was greater than the amount observed using a single method or 2 combinations (MN+EP, MN+SN, SN+EP). The histological images indicate no noticeable damage in the skin treated with all of the enhancement methods. These results suggest that MN+EP+SN may serve as a potentially effective combination strategy to transdermally deliver various hydrophilic macromolecules without causing structural alterations or skin damage. 10.1248/bpb.b14-00321
    A special issue on reviews in nanomedicine, drug delivery and vaccine development. Nalwa Hari Singh Journal of biomedical nanotechnology This thematic special issue of the Journal of Biomedical Nanotechnology focused on the "Reviews in Nanomedicine, Drug Delivery and Vaccine Development" contains 30 state-of-the-art review articles covering recent advances, trends and future directions emphasized on nanoparticle-based new strategies for diagnosis and cancer phototherapies, nanomedicine, nucleic acid-based nanocarriers, gene and drug delivery systems, tuberculosis mucosal and H5N1 influenza vaccines, drug-loaded electrospun polymer nanofibers, microneedle technology for insulin delivery for the treatment of insulin-dependent diabetes mellitus, RNA-based therapies, nanotoxicity and biosafety of nanomaterials to environment and human health.
    Fabrication of carbon nanotube-polyimide composite hollow microneedles for transdermal drug delivery. Lyon Bradley J,Aria Adrianus I,Gharib Morteza Biomedical microdevices We introduce a novel method for fabricating hollow microneedles for transdermal drug delivery using a composite of vertically-aligned carbon nanotubes and polyimide. Patterned bundles of carbon nanotubes are used as a porous scaffold for defining the microneedle geometry. Polyimide resin is wicked through the carbon nanotube scaffold to reinforce the structure and provide the prerequisite strength for achieving skin penetration. The high aspect ratio and bottom-up assembly of carbon nanotubes allow the structure of the microneedles to be created in a single step of nanotube fabrication, providing a simple, scalable method for producing hollow microneedles. To demonstrate the utility of these microneedles, liquid delivery experiments are performed. Successful delivery of aqueous methylene blue dye into both hydrogel and swine skin in vitro is demonstrated. Electron microscopy images of the microneedles taken after delivery confirm that the microneedles do not sustain any structural damage during the delivery process. 10.1007/s10544-014-9892-y
    Safety and feasibility of adjunctive dexamethasone infusion into the adventitia of the femoropopliteal artery following endovascular revascularization. Owens Christopher D,Gasper Warren J,Walker Joy P,Alley Hugh F,Conte Michael S,Grenon S Marlene Journal of vascular surgery OBJECTIVE:Restenosis following endovascular treatment of the femoropopliteal segment is associated with the inflammatory response produced in the artery wall at the time of the procedure. Although local drug delivery to the superficial femoral and popliteal arteries promises improved patency, data are currently limited. We hypothesized that improved percutaneous delivery of an anti-inflammatory compound into the adventitia of the femoropopliteal at the time of endovascular treatment would be safe, feasible, and decrease the inflammatory response. METHODS:This was a prospective, investigator-initiated, phase I, first-in-man study testing the safety and feasibility of percutaneous adventitial delivery of dexamethasone. Following successful intervention, an adventitial microinfusion catheter was advanced over a 0.014-inch wire to the treated segment. Its microneedle (0.9 mm long × 140-μm diameter) was deployed into the adventitia to deliver dexamethasone (4 mg/mL) mixed with contrast agent (80:20 ratio), providing fluoroscopic visualization. The primary safety outcome measure was freedom from vessel dissection, thrombosis, or extravasation while the primary efficacy outcome was duplex-determined binary restenosis defined as a peak systolic velocity ratio >2.5. RESULTS:Twenty patients with Rutherford clinical category 2-5 enrolled in this study. The mean age was 66, and 55% had diabetes mellitus. Treated lesion length was 8.9 ± 5.3 cm, and 50% were chronic total occlusions. Eighty percent of treated lesions were in the distal superficial femoral or popliteal arteries. All lesions were treated by balloon angioplasty with provisional stenting (n = 6) for suboptimal result. Three patients were treated with atherectomy as well. A mean of 1.6 ± 1.1 mg (0.5 ± 0.3 mL) of dexamethasone sodium phosphate was injected per centimeter of lesion length. In total, a mean of 12.1 ± 6.1 mg of dexamethasone was injected per patient. The mean number of injections required per lesion was 3.0 ± 1.3 cm, minimum one and maximum six injections. There was 100% technical success of drug delivery and no procedural or drug-related adverse events. The mean Rutherford score decreased from 3.1 ± .7 (median, 3.0) preoperatively to .5 ± .7 at 6 months (median, 0.0; P < .00001). Over this same time interval, the index leg ankle-brachial index increased from .68 ± .15 to .89 ± .19 (P = .0003). The preoperative C-reactive protein in this study was 6.9 ± 8.5 indicating severe baseline inflammation, which increased to 14.0 ± 23.1 mg/L (103% increase) at 24 hours following the procedure. However, this increase did not reach statistical significance of P = .14. Two patients met the primary efficacy end point of loss of primary patency by reoccluding their treated segment of the index lesion during the follow-up period. CONCLUSIONS:Adventitial drug delivery via a microinfusion catheter is a safe and feasible alternative to intimal-based methods for adjunctive treatment in the femoropopliteal segment. The 6-month preliminary results suggest perivascular dexamethasone treatment may improve outcomes following angioplasty to the femoral and popliteal arteries, and support further clinical investigation of this approach. 10.1016/j.jvs.2013.10.051
    Particle-stabilized emulsion droplets for gravity-mediated targeting in the posterior segment of the eye. Kim Yoo C,Edelhauser Henry F,Prausnitz Mark R Advanced healthcare materials This study tests the hypothesis that high-density particle-stabilized emulsion droplets (PEDs) can be designed to use gravity to target specific locations in the eye via suprachoroidal space injection. PEDs contain a core of high-density perfluorodecalin measuring ≤35 μm in diameter surrounded and stabilized by fluorescein-tagged, polystyrene nanoparticles that simulate polymeric drug carriers. A hollow microneedle infuses PEDs into the suprachoroidal space of rabbit eyes in vivo, which are later dissected and imaged to quantify distribution of fluorescent nanoparticles within the suprachoroidal space. With cornea oriented upward, such that gravity should move PEDs toward the back of the eye, up to 50% of nanoparticles are in the most posterior quadrant near the macula immediately after injection and 5 d later. With cornea oriented downward, to promote PED movement toward the front of the eye, approximately 60% of injected nanoparticles are targeted to the most anterior quadrant of the posterior segment near ciliary body. Injection of approximately neutral-density particles of the same size shows approximately equal distribution throughout the posterior segment. This study demonstrates for the first time that high-density PEDs can be used to deliver nanoparticles to specific locations in the back of the eye, including targeted delivery to the macula. 10.1002/adhm.201300696
    Intradermal and virosomal influenza vaccines for preventing influenza hospitalization in the elderly during the 2011-2012 influenza season: a comparative effectiveness study using the Valencia health care information system. Puig-Barberà J,Natividad-Sancho A,Calabuig-Pérez J,Lluch-Rodrigo J A,Pastor-Villalba E,Martínez-Úbeda S,Díez-Domingo J Vaccine BACKGROUND:The use of intradermal vaccination or virosomal vaccines could increase protection against influenza among the vulnerable population of older adults. Studies assessing the comparative effectiveness of these two influenza vaccine types in this age group are lacking. METHODS:We conducted a retrospective cohort study to estimate the comparative effectiveness of intradermal seasonal trivalent-influenza vaccine (TIV) delivered by a microneedle injection system and a virosomal-TIV intramuscularly delivered for prevention of influenza hospitalization in non-institutionalized adults aged ≥65 years. We obtained administrative data on immunization status and influenza hospitalization for the 2011-2012 influenza season, and used Cox regression models to assess comparative effectiveness. We estimated crude and adjusted (age, sex, comorbidity, pharmaceutical claims, recent pneumococcal vaccination and number of hospitalizations for all causes other than influenza between the previous and current influenza seasons) hazard ratios (HR). RESULTS:Overall, 164,021 vaccinated subjects were evaluated. There were 127 hospitalizations for influenza among 62,058 subjects, contributing 914,740 person-weeks at risk in the virosomal-TIV group, and 133 hospitalizations for influenza among 101,963 subjects, contributing 1,504,570 person-weeks at risk in the intradermal-TIV group. The crude HR of intradermal-TIV relative to virosomal-TIV was 0.64 (95% confidence interval (CI): 0.50-0.81), and the adjusted Cox estimated HR was 0.67 (95% CI: 0.52-0.85). CONCLUSIONS:During the 2011-2012 influenza season the risk of hospitalization for influenza was reduced by 33% in non-institutionalized elderly adults who were vaccinated with intradermal-TIV compared with virosomal-TIV. 10.1016/j.vaccine.2014.07.095
    Wound healing potential of antibacterial microneedles loaded with green tea extracts. Park So Young,Lee Hyun Uk,Lee Young-Chul,Kim Gun Hwa,Park Edmond Changkyun,Han Seung Hyun,Lee Jeong Gyu,Choi Saehae,Heo Nam Su,Kim Dong Lak,Huh Yun Suk,Lee Jouhahn Materials science & engineering. C, Materials for biological applications This study evaluates the utility of an antibacterial microneedle composed of green tea (GT) extract and hyaluronic acid (HA), for the efficient delivery of GT. These microneedles have the potential to be a patient-friendly method for the conventional sustained release of drugs. In this study, a fabrication method using a mold-based technique to produce GT/HA microneedles with a maximum area of ~50mm(2) with antibacterial properties was used to manufacture transdermal drug delivery systems. Fourier transform infrared (FTIR) spectrometry was carried out to observe the potential modifications in the microneedles, when incorporated with GT. The degradation rate of GT in GT/HA microneedles was controlled simply by adjusting the HA composition. The effects of different ratios of GT in the HA microneedles were determined by measuring the release properties. In HA microneedles loaded with 70% GT (GT70), a continuous higher release rate was sustained for 72h. The in vitro cytotoxicity assays demonstrated that GT/HA microneedles were not generally cytotoxic to Chinese hamster ovary cells (CHO-K1), human embryonic kidney cells (293T), and mouse muscle cells (C2C12), which were treated for 12 and 24h. Antimicrobial activity of the GT/HA microneedles was demonstrated by ~95% growth reduction of gram negative [Escherichia coli (E. coli), Pseudomonas putida (P. putida), and Salmonella typhimurium (S. typhimurium)] and gram positive bacteria [Staphylococcus aureus (S. Aureus) and Bacillus subtilis (B. subtilis)], with GT70. Furthermore, GT/HA microneedles reduced bacterial growth of infected wound sites in the skin and improved wound healing process of skin in rat model. 10.1016/j.msec.2014.06.021
    Self-setting bioceramic microscopic protrusions for transdermal drug delivery. Cai Bing,Xia Wei,Bredenberg Susanne,Engqvist Håkan Journal of materials chemistry. B Microneedle (MN) technology offers both an efficient and a minimally invasive transdermal drug delivery strategy. The current MNs, made of silicon and metal, have poor biocompatibility and low drug loading, while the polymer MNs have some constraints related to mechanical strength and storage conditions. In this study, self-setting bioceramics were explored as substitutes for the current MN materials for the first time. Self-setting bioceramic microneedles were fabricated using a master mold by a procedure under mild conditions, which could minimize the drug degradation during fabrication and also facilitates a higher drug loading capability than the other current ceramic microneedles. The drug release and mechanical strength were correlated with the microstructure and porosity of the needles. As observed by SEM and microCT, the ceramic paste could fully fill the geometry of the mould and was cured into an array of micro-sized needles. The drug release study showed that the release rate from this type of MN array could be controlled by the bulk surface area, porosity and resorption rate of the ceramic needles. Applying the MNs to porcine skin indicated that the needles were able to pierce the stratum corneum of the skin. We successfully prepared the bioceramic needles that have high mechanical strength and are resorbable, which can promote safe, efficient and successful transdermal drug delivery. 10.1039/c4tb00764f
    Damage of zona pellucida reduces the developmental potential and quality of porcine circovirus type 2-infected oocytes after parthenogenetic activation. Zhao Haijing,Ji Qianqian,Zhao Guangyin,Song Zhenwei,Du Baozhu,Nie Yu,Chen Yaosheng,Cong Peiqing Theriogenology The present aimed to study if porcine circovirus type 2 (PCV2), which adhered to zona pellucida (ZP), was able to enter mature porcine oocytes with intact and damaged ZP. Four groups, including uninfected ZP-intact oocytes (UOZI), uninfected ZP-damaged oocytes (UOZD), PCV2-infected ZP-intact oocytes (POZI), and PCV2-infected ZP-damaged oocytes (POZD) were studied. The oocytes were incubated with 1 mL minimum essential medium, containing 3.1 × 10(8) copies of PCV2 DNA for 1 hour. Mechanical procedure of the insertion by microneedle induced injuries to the ZP of porcine oocytes. At the blastocyst stage, the percentage of PCV2-infected embryos and the ratio of viral antigen-positive cells per embryo were determined by indirect immunofluorescence. To assess the effect of ZP injury on the developmental competence and quality of porcine PCV2-infected oocytes after parthenogenetic activation, blastocyst formation rates and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining were analyzed. Moreover, real-time polymerase chain reaction was used to evaluate the expression of genes related to apoptosis and pluripotency at different developmental stages. The results of indirect immunofluorescence showed that only POZD group presented PCV2-infected embryos and viral-positive cells. The blastocyst rate of POZD group dropped down to approximately half of POZI group's (7.1 ± 1.5 vs. 14.5 ± 3.3). At the blastocyst stage, ZP injury increased apoptotic index of PCV2-infected embryos. The relative expression levels of Caspase 3 were higher in POZD group than the ones in POZI group at the two- and four-cell stages (not statistically significant). Compared with the one in POZI group, the ratio of antiapoptotic Bcl-xl gene to proapoptotic Bax gene, an indicator of the ability to resist apoptosis, was lower in POZD group at the one-cell stage, but higher at the two- and four-cell stages. Expression levels of Oct4 and Nanog associated with pluripotency were lower in POZD group than the ones in POZI group at the morula stage (not statistically significant). Noteworthily, the expression of Nanog was significantly lower in POZD group versus POZI group (P < 0.05), whereas relative expression of Oct4 was significantly higher in the former at the blastocyst stage (P < 0.01). In conclusion, PCV2, which attached to ZP, was able to enter mature porcine oocytes with damaged ZP and subsequently reduced the developmental competence and quality of the oocytes after parthenogenetic activation. 10.1016/j.theriogenology.2014.06.003
    Efficacy of microneedling plus human stem cell conditioned medium for skin rejuvenation: a randomized, controlled, blinded split-face study. Lee Hee Jung,Lee Eo Gin,Kang Sangjin,Sung Jong-Hyuk,Chung Hyung-Min,Kim Dong Hyun Annals of dermatology BACKGROUND:The use of growth factors in skin rejuvenation is emerging as a novel anti-aging treatment. While the role of growth factors in wound healing is well established, their use in skin rejuvenation has only recently been to be studied and no controlled trials have been performed. OBJECTIVE:We evaluated the anti-aging effects of secretory factors of endothelial precursor cells differentiated from human embryonic stem cells (hESC-EPC) in Asian skin. METHODS:A total of 25 women were included in this randomized, controlled split-face study. The right and left sides of each participant's face were randomly allocated to hESC-EPC conditioned medium (CM) or saline. To enhance epidermal penetration, a 0.25-mm microneedle roller was used. Five treatment sessions were repeated at 2-week intervals. RESULTS:Physician's global assessment of pigmentation and wrinkles after treatment revealed statistically significant effects of microneedling plus hESC-EPC CM compared to microneedling alone (p<0.05). Skin measurements by Mexameter and Visiometer also revealed statistically significant effects of microneedling plus hESC-EPC CM on both pigmentation and wrinkles (p<0.05). The only minimal adverse event was mild desquamation in one participant. CONCLUSION:Secretory factors of hESC-EPC improve the signs of skin aging and could be a potential option for skin rejuvenation. 10.5021/ad.2014.26.5.584
    Proton flows across the plasma membrane in microperforated characean internodes: tonoplast injury and involvement of cytoplasmic streaming. Bulychev Alexander A,Komarova Anna V Protoplasma Microperforation of characean cell wall with a glass micropipette in the absence of the tonoplast impalement was found to cause rapid alkalinization of the apoplast by 2-3 pH units, which may rigidify the cell wall structure, thus protecting the cell from further injury. A similar but a deeper insertion of a microneedle, associated with piercing the tonoplast and with an action potential generation, led to a considerable delay in the apoplast alkalinization without affecting the amplitude of the eventual increase in pH. The retardation by the mechanically elicited action potential of the incision-mediated pH transients in the apoplast contrasted sharply to the enhancement of these pH transients by the action potential triggered electrically before the microperforation. Hence, the delay of the apoplast alkalinization was not related to basic ionic mechanisms of plant action potentials. Measurements of the vacuolar pH after mechanical elicitation of an action potential indicate that the tonoplast piercing was accompanied by leakage of protons from the vacuole into the cytoplasm, which may strongly acidify the cytoplasm around the wounded area, thus collapsing the driving force for H(+) influx from the medium into the cytoplasm. The lag period preceding the onset of external alkalinization was found linearly related to the duration of temporal cessation of cytoplasmic streaming. The results suggest that the delayed alkalinization of the apoplast in the region of tonoplast wounding reflects the localized recovery of the proton motive force across the plasmalemma during replacement of the acidic cytoplasm with fresh portions of unimpaired cytoplasm upon restoration of cytoplasmic streaming. 10.1007/s00709-014-0650-z
    Coating solid dispersions on microneedles via a molten dip-coating method: development and in vitro evaluation for transdermal delivery of a water-insoluble drug. Ma Yunzhe,Gill Harvinder S Journal of pharmaceutical sciences This study demonstrates for the first time the ability to coat solid dispersions on microneedles as a means to deliver water-insoluble drugs through the skin. Polyethylene glycol (PEG) was selected as the hydrophilic matrix, and lidocaine base was selected as the model hydrophobic drug to create the solid dispersion. First, thermal characterization and viscosity measurements of the PEG-lidocaine mixture at different mass fractions were performed. The results show that lidocaine can remain stable at temperatures up to ∼130°C and that viscosity of the PEG-lidocaine molten solution increases as the mass fraction of lidocaine decreases. Differential scanning calorimetry demonstrated that at lidocaine mass fraction less than or equal to 50%, lidocaine is well dispersed in the PEG-lidocaine mixture. Uniform coatings were obtained on microneedle surfaces. In vitro dissolution studies in porcine skin showed that microneedles coated with PEG-lidocaine dispersions resulted in significantly higher delivery of lidocaine in just 3 min compared with 1 h topical application of 0.15 g EMLA®, a commercial lidocaine-prilocaine cream. In conclusion, the molten coating process we introduce here offers a practical approach to coat water-insoluble drugs on microneedles for transdermal delivery. 10.1002/jps.24159
    Use of radiofrequency in cosmetic dermatology: focus on nonablative treatment of acne scars. Simmons Brian J,Griffith Robert D,Falto-Aizpurua Leyre A,Nouri Keyvan Clinical, cosmetic and investigational dermatology Acne is a common affliction among many teens and some adults that usually resolves over time. However, the severe sequela of acne scarring can lead to long-term psychological and psychiatric problems. There exists a multitude of modalities to treat acne scars such as more invasive surgical techniques, subcision, chemical peels, ablative lasers, fractional lasers, etc. A more recent technique for the treatment of acne scars is nonablative radiofrequency (RF) that works by passing a current through the dermis at a preset depth to produce small thermal wounds in the dermis which, in turn, stimulates dermal remodeling to produce new collagen and soften scar defects. This review article demonstrates that out of all RF modalities, microneedle bipolar RF and fractional bipolar RF treatments offers the best results for acne scarring. An improvement of 25%-75% can be expected after three to four treatment sessions using one to two passes per session. Treatment results are optimal approximately 3 months after final treatment. Common side effects can include transient pain, erythema, and scabbing. Further studies are needed to determine what RF treatment modalities work best for specific scar subtypes, so that further optimization of RF treatments for acne scars can be determined. 10.2147/CCID.S74411
    The role of microneedles for drug and vaccine delivery. Quinn Helen L,Kearney Mary-Carmel,Courtenay Aaron J,McCrudden Maelíosa T C,Donnelly Ryan F Expert opinion on drug delivery INTRODUCTION:Transdermal drug delivery offers a number of advantages for the patient, not only due to its non-invasive and convenient nature, but also due to factors such as avoidance of first-pass metabolism and prevention of gastrointestinal degradation. It has been demonstrated that microneedles (MNs) can increase the number of compounds amenable to transdermal delivery by penetrating the skin's protective barrier, the stratum corneum, and creating a pathway for drug permeation to the dermal tissue below. AREAS COVERED:MNs have been extensively investigated for drug and vaccine delivery. The different types of MN arrays and their delivery capabilities are discussed in terms of drugs, including biopharmaceutics and vaccines. Patient usage and effects on the skin are also considered. EXPERT OPINION:MN research and development is now at the stage where commercialisation is a viable possibility. There are a number of long-term safety questions relating to patient usage which will need to be addressed moving forward. Regulatory guidance is awaited to direct the scale-up of the manufacturing process alongside provision of clearer patient instruction for safe and effective use of MN devices. 10.1517/17425247.2014.938635
    CXCL1 gene silencing in skin using liposome-encapsulated siRNA delivered by microprojection array. Haigh Oscar,Depelsenaire Alexandra C I,Meliga Stefano C,Yukiko Sally R,McMillan Nigel A J,Frazer Ian H,Kendall Mark A F Journal of controlled release : official journal of the Controlled Release Society The barrier morphology of skin provides major obstacles for the application of siRNA for gene silencing, which current delivery technologies do not effectively overcome. Emerging technologies utilise microprojection array devices to penetrate into the skin epidermis and dermis for delivery of drug payloads. Delivery of siRNA by such devices has been proven in principle, yet requires optimisation for clinical applications. Herein, we demonstrate the use of Nanopatch™ microprojection arrays to deliver liposome-encapsulated siRNA to overcome skin barrier, and in vivo siRNA delivery hurdles. This application provided effective silencing of CXCL1 expression induced by the co-delivery of Fluvax 2012® by microprojection array. Liposomes encapsulating siRNA were dry-coated onto microprojection arrays, and remained intact after elution from arrays in vitro. Microprojection arrays facilitated the delivery of fluorescently-labelled nucleic acids through murine ear stratum corneum to the epidermis and dermis, with diffusion from microprojections into adjacent skin evident within 30s. CXCL1 mRNA, induced by delivery of Fluvax by microprojection array, was reduced by 75% up to 20 h post-treatment by co-delivery of liposome-encapsulated CXCL1-specific siRNA, but not by arrays co-delivering liposome-encapsulated control siRNA. CXCL1 protein expression in explant cultures from skin treated with arrays bearing CXCL1 specific or control siRNA was similarly reduced. These results as a test case have many implications for gene silencing in skin and inflammation, with the benefit of targeted delivery using microprojection arrays to deliver liposome-encapsulated siRNA. 10.1016/j.jconrel.2014.08.021
    Potential of microneedles in enhancing delivery of photosensitising agents for photodynamic therapy. Kearney Mary-Carmel,Brown Sarah,McCrudden Maelíosa T C,Brady Aaron J,Donnelly Ryan F Photodiagnosis and photodynamic therapy Photodynamic therapy can be used in the treatment of pre-malignant and malignant diseases. It offers advantages over other therapies currently used in the treatment of skin lesions including avoidance of damage to surrounding tissue and minimal or no scarring. Unfortunately, systemic delivery of photosensitising agents can result in adverse effects, such as prolonged cutaneous photosensitivity; while topical administration lacks efficacy in the clearance of deeper skin lesions and those with a thick overlying keratotic layer. Therefore, enhancement of conventional photosensitiser delivery is desired. However, the physicochemical properties of photosensitising agents, such as extreme hydrophilicity or lipophilicity and large molecular weights make this challenging. This paper reviews the potential of microneedles as a viable method to overcome these delivery-limiting physicochemical characteristics and discusses the current benefits and limitations of solid, dissolving and hydrogel-forming microneedles. Clinical studies in which microneedles have successfully improved photodynamic therapy are also discussed, along with benefits which microneedles offer, such as precise photosensitiser localisation, painless application and reduction in waiting times between photosensitiser administration and irradiation highlighted. 10.1016/j.pdpdt.2014.09.003
    Intradermal insulin delivery: a promising future for diabetes management. Hultström Michael,Roxhed Niclas,Nordquist Lina Journal of diabetes science and technology The incidence of insulinopenic diabetes mellitus is constantly increasing, and in addition, approximately a third of all hyperinsulinemic diabetic patients develop insulinopenia. Optimal glycemic control is essential to minimize the risk for diabetes-induced complications, but the majority of diabetic patients fail to achieve proper long-term glucose levels even in clinical trials, and even more so in clinical practice. Compliance with a treatment regimen is likely to be higher if the procedure is simple, painless, and discreet. Thus, insulin has been suggested for nasal, gastrointestinal, and inhalation therapy, but so far with considerable downsides in effect, side effects, or patient acceptance. The stratum corneum is the main barrier preventing convenient drug administration without the drawbacks of subcutaneous injections. Recently, devices with miniaturized needles have been developed that combine the simplicity and discretion of patch-based treatments, but with the potential of peptide and protein administration. As this review describes, initial comparisons with subcutaneous administration now suggest microneedle patches for active insulin delivery are efficient in maintaining glycemic control. Hollow microneedle technology could also prove to be efficient in systemic as well as local delivery of other macromolecular drugs, such as vaccines. 10.1177/1932296814530060
    Strong and conductive chitosan-reduced graphene oxide nanocomposites for transdermal drug delivery. Justin Richard,Chen Biqiong Journal of materials chemistry. B Chitosan-reduced graphene oxide (rGO) nanocomposites were synthesized through a biocompatible reduction process and were first reported for applications in transdermal drug delivery devices, such as microneedle arrays. Introducing rGO improved the mechanical properties of chitosan, with the strongest nanocomposites containing 1 wt% and 2 wt% rGO chosen to undergo drug delivery testing. The addition of rGO increased the electrical conductivity of chitosan, allowing the nanocomposites to be used for electroporation or iontophoresis drug delivery applications. The rGO content was proven to be an important factor for drug delivery due to the bonding of drug onto rGO. Increasing the rGO content allowed for a quicker and more substantial drug release, allowing for a controlled drug release rate. The nanocomposites also exhibited pH dependent release behaviour, with a reduced release rate in the presence of an acidic medium. The biodegradation rate of chitosan decreased when rGO was added but the biodegradation rates of the nanocomposites are not dependent on the rGO concentration, with nanocomposites of 1 wt% and 2 wt% rGO possessing a similar biodegradation path. The use of the nanocomposite in a microneedle array was shown through compression testing and drug release testing in a pseudo-in vivo environment. 10.1039/c4tb00390j
    Vehicle influence on permeation through intact and compromised skin. Gujjar Meera,Banga Ajay K International journal of pharmaceutics The purpose of this study was to compare the transdermal permeation of a model compound, diclofenac diethylamine, from a hydrophilic and lipophilic vehicle across in vitro models simulating compromised skin. Mineral oil served as a lipophilic vehicle while 10mM phosphate buffered saline served as a hydrophilic vehicle. Compromised skin was simulated by tape stripping, delipidization, or microneedle application and compared with intact skin as a control. Transepidermal water loss was measured to assess barrier function. Skin compromised with tape stripping and delipidization significantly (p<0.05) increased permeation of diclofenac diethylamine compared to intact and microneedle treated skin with phosphate buffered saline vehicle. A similar trend in permeation was observed with mineral oil as the vehicle. For both vehicles, permeation across skin increased in the same order and correlated with degree of barrier impairment as indicated by transepidermal water loss values: intact<microneedles<tape stripping<delipidization. A study with hairless rats comparing both vehicles found the same trend, with hydrophilic vehicle having greater delivery. In conclusion, phosphate buffered saline vehicle resulted in higher permeation into and across skin compared to mineral oil vehicle for all simulated models of compromised skin. 10.1016/j.ijpharm.2014.06.050
    Patient-controlled analgesia: therapeutic interventions using transdermal electro-activated and electro-modulated drug delivery. Indermun Sunaina,Choonara Yahya E,Kumar Pradeep,Du Toit Lisa C,Modi Girish,Luttge Regina,Pillay Viness Journal of pharmaceutical sciences Chronic pain poses a major concern to modern medicine and is frequently undertreated, causing suffering and disability. Patient-controlled analgesia, although successful, does have limitations. Transdermal delivery is the pivot to which analgesic research in drug delivery has centralized, especially with the confines of needle phobias and associated pain related to traditional injections, and the existing limitations associated with oral drug delivery. Highlighted within is the possibility of further developing transdermal drug delivery for chronic pain treatment using iontophoresis-based microneedle array patches. A concerted effort was made to review critically all available therapies designed for the treatment of chronic pain. The drug delivery systems developed for this purpose and nondrug routes are elaborated on, in a systematic manner. Recent developments and future goals in transdermal delivery as a means to overcome the individual limitations of the aforementioned delivery routes are represented as well. The approval of patch-like devices that contain both the microelectronic-processing mechanism and the active medicament in a small portable device is still awaited by the pharmaceutical industry. This anticipated platform may provide transdermal electro-activated and electro-modulated drug delivery systems a feasible attempt in chronic pain treatment. Iontophoresis has been proven an effective mode used to administer ionized drugs in physiotherapeutic, diagnostic, and dermatological applications and may be an encouraging probability for the development of devices and aids in the treatment of chronic pain. 10.1002/jps.23829
    The effects of chemical and physical penetration enhancers on the percutaneous permeation of lidocaine through equine skin. Stahl Jessica,Kietzmann Manfred BMC veterinary research BACKGROUND:The effect of physical and chemical permeation enhancers on in vitro transdermal permeation of lidocaine was investigated in the horse.Therefore, the effect of six vehicles (phosphate-buffered saline (PBS), 50% ethanol, 50% propylene glycol, 50% isopropylalcohol, 50% isopropylalcohol/isopropylmyristate and 50% dimethylsulfoxide) was examined as well as the effect of microneedle pretreatment with different needle lengths on transdermal drug delivery of lidocaine.The skin was obtained from the thorax of six Warmblood horses and was stored up to two weeks at - 20°C. Franz-type diffusion cells were used to study the transdermal permeation through split skin (600 μm thickness). The amount of lidocaine in the receptor fluid was determined by UV-VIS high-performance liquid chromatography. RESULTS:All investigated vehicle supplementations diminished the transdermal flux of lidocaine through equine skin in comparison to pure PBS except dimethylsulfoxide, which resulted in comparable permeation rates to PBS. The maximum flux (Jmax) was 1.6-1.8 fold lower for lidocaine applied in 50% ethanol, propylene glycol, isopropylalcohol and isopropylalcohol/isopropylmyristate. A significant higher Jmax of lidocaine was observed when lidocaine was applied in PBS onto microneedle pretreated skin with similar permeation rates in both needle lengths. After 6 hours, 1.7 fold higher recovery rates were observed in the microneedle pretreated skin samples than in the untreated control samples. The lagtimes were reduced to 20-50% in the microneedle pretreated skin samples. CONCLUSION:Microneedles represent a promising tool for transdermal lidocaine application in the horse with a rapid systemic bioavailability. 10.1186/1746-6148-10-138
    Polyplex-releasing microneedles for enhanced cutaneous delivery of DNA vaccine. Kim Nak Won,Lee Min Sang,Kim Kyu Ri,Lee Jung Eun,Lee Kyuri,Park Jong Sung,Matsumoto Yoh,Jo Dong-Gyu,Lee Haeshin,Lee Doo Sung,Jeong Ji Hoon Journal of controlled release : official journal of the Controlled Release Society Microneedle (MN)-based DNA vaccines have many advantages over conventional vaccines administered by hypodermic needles. However, an efficient strategy for delivering DNA vaccines to intradermal cells has not yet been established. Here, we report a new approach for delivering polyplex-based DNA vaccines using MN arrays coated with a pH-responsive polyelectrolyte multilayer assembly (PMA). This approach enabled rapid release of polyplex upon application to the skin. In addition to the polyplex-releasing MNs, we attempted to further maximize the vaccination by developing a polymeric carrier that targeted resident antigen presenting cells (APCs) rich in the intradermal area, as well as a DNA vaccine encoding a secretable fusion protein containing amyloid beta monomer (Aβ1-42), an antigenic determinant. The resulting vaccination system was able to successfully induce a robust humoral immune response compared to conventional subcutaneous injection with hypodermal needles. In addition, antigen challenge after immunization elicited an immediate and strong recall immune response due to immunogenic memory. These results suggest the potential utility of MN-based polyplex delivery systems for enhanced DNA vaccination. 10.1016/j.jconrel.2014.01.016
    Hydrogel-forming microneedles increase in volume during swelling in skin, but skin barrier function recovery is unaffected. Donnelly Ryan F,Mooney Karen,McCrudden Maelíosa T C,Vicente-Pérez Eva M,Belaid Luc,González-Vázquez Patricia,McElnay James C,Woolfson A David Journal of pharmaceutical sciences We describe, for the first time, quantification of in-skin swelling and fluid uptake by hydrogel-forming microneedle (MN) arrays and skin barrier recovery in human volunteers. Such MN arrays, prepared from aqueous blends of hydrolyzed poly(methylvinylether/maleic anhydride) (15%, w/w) and the cross-linker poly(ethyleneglycol) 10,000 Da (7.5%, w/w), were inserted into the skin of human volunteers (n = 15) to depths of approximately 300 μm by gentle hand pressure. The MN arrays swelled in skin, taking up skin interstitial fluid, such that their mass had increased by approximately 30% after 6 h in skin. Importantly, however, skin barrier function recovered within 24 h after MN removal, regardless of how long the MN had been in skin or how much their volume had increased with swelling. Further research on closure of MN-induced micropores is required because transepidermal water loss measurements suggested micropore closure, whereas optical coherence tomography indicated that MN-induced micropores had not closed over, even 24 h after MN had been removed. There were no complaints of skin reactions, adverse events, or strong views against MN use by any of the volunteers. Only some minor erythema was noted after patch removal, although this always resolved within 48 h, and no adverse events were present on follow-up. 10.1002/jps.23921
    Micro-fractional epidermal powder delivery for improved skin vaccination. Chen Xinyuan,Kositratna Garuna,Zhou Chang,Manstein Dieter,Wu Mei X Journal of controlled release : official journal of the Controlled Release Society Skin vaccination has gained increasing attention in the last two decades due to its improved potency compared to intramuscular vaccination. Yet, the technical difficulty and frequent local reactions hamper its broad application in the clinic. In the current study, micro-fractional epidermal powder delivery (EPD) is developed to facilitate skin vaccination and minimize local adverse effects. EPD is based on ablative fractional laser or microneedle treatment of the skin to generate microchannel (MC) arrays in the epidermis followed by topical application of powder drug/vaccine-coated array patches to deliver drug/vaccine into the skin. The novel EPD delivered more than 80% sulforhodamine b (SRB) and model antigen ovalbumin (OVA) into murine, swine, and human skin within 1h. EPD of OVA induced anti-OVA antibody titer at a level comparable to intradermal (ID) injection and was much more efficient than tape stripping in both delivery efficiency and immune responses. Strikingly, the micro-fractional delivery significantly reduced local side effects of LPS/CpG adjuvant and BCG vaccine, leading to complete skin recovery. In contrast, ID injection induced severe local reactions that persisted for weeks. While reducing local reactogenicity, EPD of OVA/LPS/CpG and BCG vaccine generated a comparable humoral immune response to ID injection. EPD of vaccinia virus encoding OVA induced significantly higher and long-lasting interferon γ-secreting CD8+ T cells than ID injection. In conclusion, EPD represents a promising technology for needle-free, painless skin vaccination with reduced local reactogenicity and at least sustained immunogenicity. 10.1016/j.jconrel.2014.08.006
    Monitoring the penetration process of single microneedles with varying tip diameters. Römgens A M,Bader D L,Bouwstra J A,Baaijens F P T,Oomens C W J Journal of the mechanical behavior of biomedical materials Microneedles represent promising tools for delivery of drugs to the skin. However, before these microneedles can be used in clinical practice, it is essential to understand the process of skin penetration by these microneedles. The present study was designed to monitor both penetration depth and force of single solid microneedles with various tip diameters ranging from 5 to 37µm to provide insight into the penetration process into the skin of these sharp microneedles. To determine the microneedle penetration depth, single microneedles were inserted in human ex vivo skin while monitoring the surface of the skin. Simultaneously, the force on the microneedles was measured. The average penetration depth at 1.5mm displacement was similar for all tip diameters. However, the process of penetration depth was significantly different for the various microneedles. Microneedles with a tip diameter of 5µm were smoothly inserted into the skin, while the penetration depth of microneedles with a larger tip diameter suddenly increased after initial superficial penetration. In addition, the force at insertion (defined as the force at a sudden decrease in measured force) linearly increased with tip diameter ranging from 20 to 167mN. The force drop at insertion was associated with a measured penetration depth of approximately 160μm for all tip diameters, suggesting that the drop in force was due to the penetration of a deeper skin layer. This study showed that sharp microneedles are essential to insert microneedles in a well-controlled way to a desired depth. 10.1016/j.jmbbm.2014.09.015
    Novel cosmetic patches for wrinkle improvement: retinyl retinoate- and ascorbic acid-loaded dissolving microneedles. Kim M,Yang H,Kim H,Jung H,Jung H International journal of cosmetic science OBJECTIVE:To evaluate wrinkle improvement and safety of a novel cosmetic dissolving microneedle patches loaded with two active compounds with different hydrophilicities, namely ascorbic acid and retinyl retinoate. METHODS:Clinical studies were performed on 24 Korean women for 12 weeks. Patients in group A were treated with retinyl retinoate-loaded dissolving microneedle patches on the left eye crow's feet area, and patients in group B were treated with ascorbic acidloaded patches on the right eye crow's feet area twice daily. Wrinkle improvement was evaluated by skin Visiometer SV 600. RESULTS:Both the retinyl retinoate- and ascorbic acid-loaded dissolving microneedle patches demonstrated statistically significant differences in all Visiometer R-values (P < 0.05). In particular, highly significant differences were shown at R1 (skin roughness) and R5 (arithmetic average roughness) (P < 0.001). Also, there were no side effects such as allergies or irritant contact dermatitis. CONCLUSION:Retinyl retinoate and ascorbic acid were successfully loaded into dissolving microneedles and used to produce novel cosmetic patches. These novel patches can be used efficiently in cosmetics given their patient usability, safety and effectiveness in wrinkle improvement. 10.1111/ics.12115
    Targeted delivery of antiglaucoma drugs to the supraciliary space using microneedles. Kim Yoo C,Edelhauser Henry F,Prausnitz Mark R Investigative ophthalmology & visual science PURPOSE:In this work, we tested the hypothesis that highly targeted delivery of antiglaucoma drugs to the supraciliary space by using a hollow microneedle allows dramatic dose sparing of the drug compared to topical eye drops. The supraciliary space is the most anterior portion of the suprachoroidal space, located below the sclera and above the choroid and ciliary body. METHODS:A single, hollow 33-gauge microneedle, 700 to 800 μm in length, was inserted into the sclera and used to infuse antiglaucoma drugs into the supraciliary space of New Zealand white rabbits (N = 3-6 per group). Sulprostone, a prostaglandin analog, and brimonidine, an α₂-adrenergic agonist, were delivered via supraciliary and topical administration at various doses. The drugs were delivered unilaterally, and intraocular pressure (IOP) of both eyes was measured by rebound tonometry for 9 hours after injection to assess the pharmacodynamic responses. To assess safety of the supraciliary injection, IOP change immediately after intravitreal and supraciliary injection were compared. RESULTS:Supraciliary delivery of both sulprostone and brimonidine reduced IOP by as much as 3 mm Hg bilaterally in a dose-related response; comparison with topical administration at the conventional human dose showed approximately 100-fold dose sparing by supraciliary injection for both drugs. A safety study showed that the kinetics of IOP elevation immediately after supraciliary and intravitreal injection of placebo formulations were similar. CONCLUSIONS:This study introduced the use of targeted drug delivery to the supraciliary space by using a microneedle and demonstrated dramatic dose sparing of antiglaucoma therapeutic agents compared to topical eye drops. Targeted delivery in this way can increase safety by reducing side effects and could allow a single injection to contain enough drug for long-term sustained delivery. 10.1167/iovs.14-14651
    Parents' attitude toward multiple vaccinations at a single visit with alternative delivery methods. Kaaijk Patricia,Kleijne Deborah E,Knol Mirjam J,Harmsen Irene A,Ophorst Olga J A E,Rots Nynke Y Human vaccines & immunotherapeutics Last decades, the number of routine childhood vaccinations has increased considerably, which consequently has led to multiple vaccine injections per consultation. Implementation of additional vaccines will probably lead to more than 2 vaccine injections per consult, which might be a barrier for parents to vaccinate their child. A decrease in vaccination coverage, however, increases the risk of disease outbreaks. Less stressful alternative methods for vaccine delivery might lead to an increased acceptance of multiple childhood vaccinations by parents. The present questionnaire study was set up to explore the maximum number of vaccine injections per visit that is acceptable for parents, as well as to gauge parents' attitude toward alternative needle-free methods for vaccine delivery. For this purpose, the parents' opinion toward a jet injector, a patch, a microneedle system, and nasal spray device as methods for vaccine delivery was assessed. The majority of the 1154 participating parents indicated that 3 vaccine injections per visit was perceived as too much. Most participants had a positive attitude with respect to the jet injector and the patch as alternative vaccine delivery method, whereas the microneedle device and an intranasal spray device were not perceived as better than the conventional syringe by the parents. Parents indicated that both the jet injector and the patch might increase their acceptance of giving their children more than 2 vaccinations at the same time. This should encourage vaccine developers and manufacturers to put efforts in developing these delivery methods for their vaccines. 10.4161/hv.29361
    Vaccine delivery to the oral cavity using coated microneedles induces systemic and mucosal immunity. Ma Yunzhe,Tao Wenqian,Krebs Shelly J,Sutton William F,Haigwood Nancy L,Gill Harvinder S Pharmaceutical research PURPOSE:The objective of this study is to evaluate the feasibility of using coated microneedles to deliver vaccines into the oral cavity to induce systemic and mucosal immune responses. METHOD:Microneedles were coated with sulforhodamine, ovalbumin and two HIV antigens. Coated microneedles were inserted into the inner lower lip and dorsal surface of the tongue of rabbits. Histology was used to confirm microneedle insertion, and systemic and mucosal immune responses were characterized by measuring antigen-specific immunoglobulin G (IgG) in serum and immunoglobulin A (IgA) in saliva, respectively. RESULTS:Histological evaluation of tissues shows that coated microneedles can penetrate the lip and tongue to deliver coatings. Using ovalbumin as a model antigen it was found that the lip and the tongue are equally immunogenic sites for vaccination. Importantly, both sites also induced a significant (p < 0.05) secretory IgA in saliva compared to pre-immune saliva. Microneedle-based oral cavity vaccination was also compared to the intramuscular route using two HIV antigens, a virus-like particle and a DNA vaccine. Microneedle-based delivery to the oral cavity and the intramuscular route exhibited similar (p > 0.05) yet significant (p < 0.05) levels of antigen-specific IgG in serum. However, only the microneedle-based oral cavity vaccination group stimulated a significantly higher (p < 0.05) antigen-specific IgA response in saliva, but not intramuscular injection. CONCLUSION:In conclusion, this study provides a novel method using microneedles to induce systemic IgG and secretory IgA in saliva, and could offer a versatile technique for oral mucosal vaccination. 10.1007/s11095-014-1335-1
    Intrastromal delivery of bevacizumab using microneedles to treat corneal neovascularization. Kim Yoo C,Grossniklaus Hans E,Edelhauser Henry F,Prausnitz Mark R Investigative ophthalmology & visual science PURPOSE:This study tested the hypothesis that highly targeted intrastromal delivery of bevacizumab using coated microneedles allows dramatic dose sparing compared with subconjunctival and topical delivery for treatment of corneal neovascularization. METHODS:Stainless steel microneedles 400 μm in length were coated with bevacizumab. A silk suture was placed in the cornea approximately 1 mm from the limbus to induce corneal neovascularization in the eyes of New Zealand white rabbits that were divided into different groups: untreated, microneedle delivery, topical eye drop, and subconjunctival injection of bevacizumab. All drug treatments were initiated 4 days after suture placement and area of neovascularization was measured daily by digital photography for 18 days. RESULTS:Eyes treated once with 4.4 μg bevacizumab using microneedles reduced neovascularization compared with untreated eyes by 44% (day 18). Eyes treated once with 2500 μg bevacizumab using subconjunctival injection gave similar results to microneedle-treated eyes. Eyes treated once with 4.4 μg subconjunctival bevacizumab showed no significant effect compared with untreated eyes. Eyes treated with 52,500 μg bevacizumab by eye drops three times per day for 14 days reduced the neovascularization area compared with untreated eyes by 6% (day 18), which was significantly less effective than the single microneedle treatment. Visual exam and histological analysis showed no observable effect of microneedle treatment on corneal transparency or microanatomical structure. CONCLUSIONS:This study shows that microneedles can target drug delivery to corneal stroma in a minimally invasive way and demonstrates effective suppression of corneal neovascularization after suture-induced injury using a much lower dose compared with conventional methods. 10.1167/iovs.14-15257
    Enhancement of the in vitro penetration of quercetin through pig skin by combined microneedles and lipid microparticles. Paleco Roberto,Vučen Sonja R,Crean Abina M,Moore Anne,Scalia Santo International journal of pharmaceutics Silicon microneedle patches were investigated, alone or in combination with lipid microparticles (LMs), as a system to improve the in vitro skin penetration of the antioxidant flavonoid, quercetin. LMs loaded with quercetin were prepared by melt emulsification and sonication. The flavonoid content of LMs was 11.7±0.3% and their mean diameter and polydispersity index were 8.1 μm and 0.66, respectively. Emulsions containing quercetin, free or microencapsulated, were applied to untreated- or microneedle-treated pig skin mounted in Franz diffusion cells. The amount of flavonoid penetrated into the stratum corneum and viable epidermis were measured by HPLC, after validated tape-stripping and bead mill homogenization procedures, respectively. Compared to intact skin, a marked increase in quercetin levels permeated into the stratum corneum (from 1.19 ± 0.12 μg/cm(2) to 2.23 ± 0.54 μg/cm(2)) and viable epidermis (from 0.10 ± 0.01 μg/cm(2) to 0.56 ± 0.27 μg/cm(2)) was achieved when skin was treated with the flavonoid-loaded LMs in combination with microneedle arrays. Conversely, perforation of the cutaneous surface by microneedles did not produce any significant improvement in the skin penetration of non-encapsulated quercetin. The enhanced (5.5-fold) intra-epidermal delivery of quercetin attained by the LM/microneedle strategy described here, is particularly relevant since the main quercetin site of action is in the epidermis. 10.1016/j.ijpharm.2014.06.010
    Current advances in the fabrication of microneedles for transdermal delivery. Indermun Sunaina,Luttge Regina,Choonara Yahya E,Kumar Pradeep,du Toit Lisa C,Modi Girish,Pillay Viness Journal of controlled release : official journal of the Controlled Release Society The transdermal route is an excellent site for drug delivery due to the avoidance of gastric degradation and hepatic metabolism, in addition to easy accessibility. Although offering numerous attractive advantages, many available transdermal systems are not able to deliver drugs and other compounds as desired. The use of hypodermic needles, associated with phobia, pain and accidental needle-sticks has been used to overcome the delivery limitation of macromolecular compounds. The means to overcome the disadvantages of hypodermic needles has led to the development of microneedles for transdermal delivery. However, since the initial stages of microneedle fabrication, recent research has been conducted integrating various fabrication techniques for generating sophisticated microneedle devices for transdermal delivery including progress on their commercialization. A concerted effort has been made within this review to highlight the current advances of microneedles, and to provide an update of pharmaceutical research in the field of microneedle-assisted transdermal drug delivery systems. 10.1016/j.jconrel.2014.04.052
    Hydrogel-forming microneedles prepared from "super swelling" polymers combined with lyophilised wafers for transdermal drug delivery. Donnelly Ryan F,McCrudden Maelíosa T C,Zaid Alkilani Ahlam,Larrañeta Eneko,McAlister Emma,Courtenay Aaron J,Kearney Mary-Carmel,Singh Thakur Raghu Raj,McCarthy Helen O,Kett Victoria L,Caffarel-Salvador Ester,Al-Zahrani Sharifa,Woolfson A David PloS one We describe, for the first time, hydrogel-forming microneedle arrays prepared from "super swelling" polymeric compositions. We produced a microneedle formulation with enhanced swelling capabilities from aqueous blends containing 20% w/w Gantrez S-97, 7.5% w/w PEG 10,000 and 3% w/w Na2CO3 and utilised a drug reservoir of a lyophilised wafer-like design. These microneedle-lyophilised wafer compositions were robust and effectively penetrated skin, swelling extensively, but being removed intact. In in vitro delivery experiments across excised neonatal porcine skin, approximately 44 mg of the model high dose small molecule drug ibuprofen sodium was delivered in 24 h, equating to 37% of the loading in the lyophilised reservoir. The super swelling microneedles delivered approximately 1.24 mg of the model protein ovalbumin over 24 h, equivalent to a delivery efficiency of approximately 49%. The integrated microneedle-lyophilised wafer delivery system produced a progressive increase in plasma concentrations of ibuprofen sodium in rats over 6 h, with a maximal concentration of approximately 179 µg/ml achieved in this time. The plasma concentration had fallen to 71±6.7 µg/ml by 24 h. Ovalbumin levels peaked in rat plasma after only 1 hour at 42.36±17.01 ng/ml. Ovalbumin plasma levels then remained almost constant up to 6 h, dropping somewhat at 24 h, when 23.61±4.84 ng/ml was detected. This work represents a significant advancement on conventional microneedle systems, which are presently only suitable for bolus delivery of very potent drugs and vaccines. Once fully developed, such technology may greatly expand the range of drugs that can be delivered transdermally, to the benefit of patients and industry. Accordingly, we are currently progressing towards clinical evaluations with a range of candidate molecules. 10.1371/journal.pone.0111547
    Lidocaine carboxymethylcellulose with gelatine co-polymer hydrogel delivery by combined microneedle and ultrasound. Nayak Atul,Babla Hiten,Han Tao,Das Diganta Bhusan Drug delivery A study that combines microneedles (MNs) and sonophoresis pre-treatment was explored to determine their combined effects on percutaneous delivery of lidocaine from a polymeric hydrogel formulation. Varying ratios of carboxymethylcellulose and gelatine (NaCMC/gel ranges 1:1.60-1:2.66) loaded with lidocaine were prepared and characterized for zeta potential and particle size. Additionally, variations in the formulation drying techniques were explored during the formulation stage. Ex vivo permeation studies using Franz diffusion cells measured lidocaine permeation through porcine skin after pre-treatment with stainless steel MNs and 20 kHz sonophoresis for 5-and 10-min durations. A stable formulation was related to a lower gelatine mass ratio because of smaller mean particle sizes and high zeta potential. Lidocaine permeability in skin revealed some increases in permeability from combined MN and ultrasound pre-treatment studies. Furthermore, up to 4.8-fold increase in the combined application was observed compared with separate pre-treatments after 30 min. Sonophoresis pre-treatment alone showed insignificant enhancement in lidocaine permeation during the initial 2 h period. MN application increased permeability at a time of 0.5 h for up to ∼17 fold with an average up to 4 fold. The time required to reach therapeutic levels of lidocaine was decreased to less than 7 min. Overall, the attempted approach promises to be a viable alternative to conventional lidocaine delivery methods involving painful injections by hypodermic needles. The mass transfer effects were fairly enhanced and the lowest amount of lidocaine in skin was 99.7% of the delivered amount at a time of 3 h for lidocaine NaCMC/GEL 1:2.66 after low-frequency sonophoresis and MN treatment. 10.3109/10717544.2014.935985
    Microneedle-iontophoresis combinations for enhanced transdermal drug delivery. Donnelly Ryan F,Garland Martin J,Alkilani Ahlam Zaid Methods in molecular biology (Clifton, N.J.) It has recently been proposed that the combination of skin barrier impairment using microneedles (MNs) coupled with iontophoresis (ITP) may broaden the range of drugs suitable for transdermal delivery as well as enabling the rate of delivery to be achieved with precise electronic control. However, few reports exist on the combination of ITP with in situ drug-loaded polymeric MN delivery systems. Our in vitro permeation studies revealed that MN enhances transdermal drug delivery. The combination of dissolving MN and ITP did not further enhance the extent of delivery of the low molecular weight drug ibuprofen sodium after short application periods. However, the extent of peptide/protein delivery was significantly enhanced when ITP was used in combination with hydrogel-forming MN arrays. As such, hydrogel-forming MN arrays show promise for the electrically controlled transdermal delivery of biomacromolecules in a simple, one-step approach, though further technical developments will be necessary before patient benefit is realized. 10.1007/978-1-4939-0363-4_7
    Microneedle-based drug delivery systems for transdermal route. Pierre Maria Bernadete Riemma,Rossetti Fabia Cristina Current drug targets Transdermal delivery offers an attractive, noninvasive administration route but it is limited by the skin's barrier to penetration. Minimally invasive techniques, such as the use of microneedles (MNs), bypass the stratum corneum (SC) barrier to permit the drug's direct access to the viable epidermis. These novel micro devices have been developed to puncture the skin for the transdermal delivery of hydrophilic drugs and macromolecules, including peptides, DNA and other molecules, that would otherwise have difficulty passing the outermost layer of the skin, the SC. Using the tools of the microelectronics industry, MNs have been fabricated with a range of sizes, shapes and materials. MNs have been shown to be robust enough to penetrate the skin and dramatically increase the skin permeability of several drugs. Moreover, MNs have reduced needle insertion pain and tissue trauma and provided controlled delivery across the skin. This review focuses on the current state of the art in the transdermal delivery of drugs using various types of MNs and developments in the field of microscale devices, as well as examples of their uses and clinical safety.
    Fluvastatin as a micropore lifetime enhancer for sustained delivery across microneedle-treated skin. Ghosh Priyanka,Brogden Nicole K,Stinchcomb Audra L Journal of pharmaceutical sciences Microneedles (MNs), a physical skin permeation enhancement technique, facilitate drug delivery across the skin, thus enhancing the number of drugs that can be delivered transdermally in therapeutically relevant concentrations. The micropores created in the skin by MNs reseal because of normal healing processes of the skin, thus limiting the duration of the drug delivery window. Pore lifetime enhancement strategies can increase the effectiveness of MNs as a drug delivery mechanism by prolonging the delivery window. Fluvastatin (FLU), a HMGCoA reductase inhibitor, was used in this study to enhance the pore lifetime by inhibiting the synthesis of cholesterol, a major component of the stratum corneum lipids. The study showed that using FLU as a pretreatment it is possible to enhance the pore lifetime of MN-treated skin and thus allow for sustained drug delivery. The skin recovered within a 30-45-min time period following the removal of occlusion, and there was no significant irritation observed due to the treatment compared to the control sites. Thus, it can be concluded that localized skin treatment with FLU can be used to extend micropore lifetime and deliver drugs for up to 7 days across MN-treated skin. 10.1002/jps.23844
    Clinical improvement of striae distensae in Korean patients using a combination of fractionated microneedle radiofrequency and fractional carbon dioxide laser. Chantes Achilleas,Antoniou Antonios,Leontaridou Ioanna Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.] 10.1111/dsu.0000000000000017
    Microneedle assisted micro-particle delivery from gene guns: experiments using skin-mimicking agarose gel. Zhang Dongwei,Das Diganta B,Rielly Chris D Journal of pharmaceutical sciences A set of laboratory experiments has been carried out to determine if micro-needles (MNs) can enhance penetration depths of high-speed micro-particles delivered by a type of gene gun. The micro-particles were fired into a model target material, agarose gel, which was prepared to mimic the viscoelastic properties of porcine skin. The agarose gel was chosen as a model target as it can be prepared as a homogeneous and transparent medium with controllable and reproducible properties allowing accurate determination of penetration depths. Insertions of various MNs into gels have been analysed to show that the length of the holes increases with an increase in the agarose concentration. The penetration depths of micro-particle were analysed in relation to a number of variables, namely the operating pressure, the particle size, the size of a mesh used for particle separation and the MN dimensions. The results suggest that the penetration depths increase with an increase of the mesh pore size, because of the passage of large agglomerates. As these particles seem to damage the target surface, then smaller mesh sizes are recommended; here, a mesh with a pore size of 178 μm was used for the majority of the experiments. The operating pressure provides a positive effect on the penetration depth, that is it increases as pressure is increased. Further, as expected, an application of MNs maximises the micro-particle penetration depth. The maximum penetration depth is found to increase as the lengths of the MNs increase, for example it is found to be 1272 ± 42, 1009 ± 49 and 656 ± 85 μm at 4.5 bar pressure for spherical micro-particles of 18 ± 7 μm diameter when we used MNs of 1500, 1200 and 750 μm length, respectively. 10.1002/jps.23835
    Calcite microneedle arrays produced by inorganic ion-assisted anisotropic dissolution of bulk calcite crystal. Long Xia,Meng Ruijie,Wu Weike,Ma Yurong,Yang Dong,Qi Limin Chemistry (Weinheim an der Bergstrasse, Germany) Besides studies on the mineralization process, research on the demineralization of minerals provides another way to understand the crystallization mechanism of biominerals and fabricate crystals with complicated morphologies. The formation of ordered arrays of c-axis-oriented calcite microneedles with a tri-symmetric structure and lengths of more than 20 μm was realized on a large scale for the first time through anisotropic dissolution of calcite substrates in undersaturated aqueous solution in the presence of ammonium salts. The lengths and the aspect ratios of the calcite microneedles can be tuned by simply changing the concentrations of the ammonium salts and the dissolution time. The shape of the transverse cross sections of the calcite microneedles obtained in the presence of NH4 Cl and NH4 Ac is almost regularly triangular. The tri-symmetric transverse cross-section geometry of the calcite microneedles could be attributed to the tri-symmetric feature of rhombohedral calcite atomic structures, the synergetic interactions between electrostatic interaction of ammonium ions and dangling surface carbonate groups, and the ion incorporation of halide ions. 10.1002/chem.201304229
    Polydimethyl siloxane wet etching for three dimensional fabrication of microneedle array and high-aspect-ratio micropillars. Deng Yu-Luen,Juang Yi-Je Biomicrofluidics Among various transdermal drug delivery (TDD) approaches, utilizing the microneedles (MNs) not only can penetrate the skin but also deliver the drug with reduced tissue damage, reduced pain, and no bleeding. However, the MNs with larger height are required to overcome the skin barrier for effective TDD. Unlike 2D patterning, etching polydimethyl siloxane (PDMS) micropillars for fabrication of 3D microstructures is presented. The PDMS micropillars were first constructed by casting PDMS on the computer numerical control-machined cylindrical microwells, which then went through etching process to obtain the MNs for subsequent fabrication of polymer MNs or high aspect ratio micropillars. 10.1063/1.4871038
    Effect of force of microneedle insertion on the permeability of insulin in skin. Cheung Karmen,Han Tao,Das Diganta Bhusan Journal of diabetes science and technology Many experiments conducted in the literature have investigated the effect of microneedles (MNs) on insulin permeation across skin. There are also a number of articles that deal with the effect of MN insertion force in skin. However, there is little known on quantifying the relationship between the effect of MN insertion force and the amount of insulin permeated for given MNs. This issue is addressed in this article. MNs of 1100 µm and 1400 µm are used to conduct in vitro permeability experiments on porcine skin, using insulin. Histological images of MN treated skin are obtained from a microtome and the viscoelastic properties of the skin sample are measured using a rheometer. An in-house insertion force device is utilized that can reproducibly apply a specified force on MNs for a set period of time using compressed air. It is deduced that when porcine skin was pretreated with an applied force of 60.5 N and 69.1 N, the resultant amount of insulin permeated was approximately 3 µg and 25 µg over a 4-hour period for the MNs used. The amount of MN force applied to porcine skin was shown to be related to the amount of insulin permeated. An increase in insertion force increase the amount of insulin permeated. It was also demonstrated that using insufficient force may have reduced or prevented the amount of insulin passing through the skin, regardless of the geometry of the MNs. 10.1177/1932296813519720
    Impact-insertion applicator improves reliability of skin penetration by solid microneedle arrays. van der Maaden Koen,Sekerdag Emine,Jiskoot Wim,Bouwstra Joke The AAPS journal 10.1208/s12248-014-9606-7
    A protective role of murine langerin⁺ cells in immune responses to cutaneous vaccination with microneedle patches. Pulit-Penaloza Joanna A,Esser E Stein,Vassilieva Elena V,Lee Jeong Woo,Taherbhai Misha T,Pollack Brian P,Prausnitz Mark R,Compans Richard W,Skountzou Ioanna Scientific reports Cutaneous vaccination with microneedle patches offers several advantages over more frequently used approaches for vaccine delivery, including improved protective immunity. However, the involvement of specific APC subsets and their contribution to the induction of immunity following cutaneous vaccine delivery is not well understood. A better understanding of the functions of individual APC subsets in the skin will allow us to target specific skin cell populations in order to further enhance vaccine efficacy. Here we use a Langerin-EGFP-DTR knock-in mouse model to determine the contribution of langerin(+) subsets of skin APCs in the induction of adaptive immune responses following cutaneous microneedle delivery of influenza vaccine. Depletion of langerin(+) cells prior to vaccination resulted in substantial impairment of both Th1 and Th2 responses, and decreased post-challenge survival rates, in mice vaccinated cutaneously but not in those vaccinated via the intramuscular route or in non-depleted control mice. Our results indicate that langerin(+) cells contribute significantly to the induction of protective immune responses following cutaneous vaccination with a subunit influenza vaccine. 10.1038/srep06094
    Microneedle-mediated immunization of an adenovirus-based malaria vaccine enhances antigen-specific antibody immunity and reduces anti-vector responses compared to the intradermal route. Carey John B,Vrdoljak Anto,O'Mahony Conor,Hill Adrian V S,Draper Simon J,Moore Anne C Scientific reports Substantial effort has been placed in developing efficacious recombinant attenuated adenovirus-based vaccines. However induction of immunity to the vector is a significant obstacle to its repeated use. Here we demonstrate that skin-based delivery of an adenovirus-based malaria vaccine, HAdV5-PyMSP1₄₂, to mice using silicon microneedles induces equivalent or enhanced antibody responses to the encoded antigen, however it results in decreased anti-vector responses, compared to intradermal delivery. Microneedle-mediated vaccine priming and resultant induction of low anti-vector antibody titres permitted repeated use of the same adenovirus vaccine vector. This resulted in significantly increased antigen-specific antibody responses in these mice compared to ID-treated mice. Boosting with a heterologous vaccine; MVA-PyMSP1₄₂ also resulted in significantly greater antibody responses in mice primed with HAdV5-PyMSP1₄₂ using MN compared to the ID route. The highest protection against blood-stage malaria challenge was observed when a heterologous route of immunization (MN/ID) was used. Therefore, microneedle-mediated immunization has potential to both overcome some of the logistic obstacles surrounding needle-and-syringe-based immunization as well as to facilitate the repeated use of the same adenovirus vaccine thereby potentially reducing manufacturing costs of multiple vaccines. This could have important benefits in the clinical ease of use of adenovirus-based immunization strategies. 10.1038/srep06154
    Rapidly dissolvable microneedle patches for transdermal delivery of exenatide. Zhu Zhuangzhi,Luo Huafei,Lu Wangding,Luan Hansen,Wu Yubo,Luo Jing,Wang Youjie,Pi Jiaxin,Lim Chee Yen,Wang Hao Pharmaceutical research PURPOSE:To assess the feasibility of transdermal delivery of exenatide (EXT) using low-molecular-weight sodium hyaluronate (HA) dissolving microneedles (MNs) patches for type 2 diabetes mellitus therapy. METHODS:Micromold casting method was used to fabricate EXT-loaded dissolving MNs. The characteristics of prepared MNs including mechanical strength, in vitro/in vivo insertion capacity, dissolution profile and storage stability were then investigated. Finally, the in vivo pharmacokinetics and hypoglycemic effects were compared with traditional subcutaneous (SC) injection. RESULTS:EXT-loaded dissolving MNs made of HA possessed sufficient mechanical strength and the strength could be weakened as the water content increases. The EXT preserved its pharmacological activity during fabrication and one-month storage. With the aid of spring-operated applicator, dissolving MNs could be readily penetrated into the skin in vitro/in vivo, and then rapidly dissolved to release encapsulated drug within 2 min. Additionally, transepidermal water loss (TEWL) determinations showed that skin's barrier properties disrupted by MNs recovered within 10-12 h. Transdermal pharmacokinetics and antidiabetic effects studies demonstrated that fabricated EXT MNs induced comparable efficacy to SC injection. CONCLUSIONS:Our rapidly dissolving MNs patch appears to an excellent, painless alternative to conventional SC injection of EXT, and this minimally invasive device might also be suitable for other biotherapeutics. 10.1007/s11095-014-1424-1
    [Development of a novel transdermal delivery system of alendronate, a nitrogen containing bisphosphonate, using a new type of hydrophilic patch and dissolving microneedle arrays]. Katsumi Hidemasa Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan Alendronate is a nitrogen-containing bisphosphonate that is widely used for the treatment of osteoporosis in postmenopausal women. However, the oral bioavailability (BA) of alendronate is approximately 0.9 to 1.8%. In addition, the oral administration of alendronate has been associated with mucosal damage including gastritis, gastric ulcer, and erosive esophagitis. To prevent these adverse effects of alendronate, patients with osteoporosis should sit up or walk for more than 30 min after oral administration, leading to poor compliance and QOL in these patients. To improve the compliance and QOL of these patients, we developed a new transdermal delivery system for alendronate using a new type of hydrophilic patch and dissolving microneedle arrays. The skin permeation of alendronate observed using our transdermal delivery system was sufficient for the treatment of osteoporosis in rat models. These findings indicate that our transdermal delivery system of alendronate is a promising approach that may result in improved therapeutic effects and better compliance and QOL in patients undergoing treatment for osteoporosis.
    Iontophoretic and microneedle mediated transdermal delivery of glycopyrrolate. Gujjar Meera,Banga Ajay K Pharmaceutics PURPOSE:The objective of this study was to investigate the use of iontophoresis, soluble microneedles and their combination for the transdermal delivery of glycopyrrolate. METHODS:In vitro permeation was tested using full thickness porcine ear skin mounted onto Franz diffusion cells. Iontophoresis (0.5 mA/cm2) was done for 4 h using Ag/AgCl electrodes. For microneedles, three line array (27 needles/line) of maltose microneedles were used to microporate the skin prior to mounting. Pore uniformity was determined by taking fluorescent images of distribution of calcein into pores and processing the images using an image analysis tool, which measured the fluorescent intensity in and around each pore to provide a pore permeability index (PPI). The donor chamber contained 500 µL of a 1 mg/mL solution of glycopyrrolate, and the receptor chamber contained 5 mL of 50 mM NaCl in deionized water. Samples were collected at predetermined time points over a period of 24 h and analyzed by HPLC. Skin irritation testing was performed with a 3D cell culture kit of human skin. MTT assay determined cell viability; viability less than 50% was considered irritant. RESULTS:A control experiment which investigated passive permeation of glycopyrrolate delivered an average cumulative amount of 24.92 ± 1.77 µg/cm2 at 24 h, while microneedle pretreatment increased permeability to 46.54 ± 6.9 µg/cm2. Both iontophoresis (158.53 ± 17.50 µg/cm2) and a combination of iontophoresis and microneedles (182.43 ± 20.06 µg/ cm2) significantly increased delivery compared to passive and microneedles alone. Glycopyrrolate solution was found to be nonirritant with cell viability of 70.4% ± 5.03%. CONCLUSION:Iontophoresis and a combination of iontophoresis with microneedle pretreatment can be effectively used to enhance the transdermal delivery of glycopyrrolate. Glycopyrrolate was found to be non-irritant to skin. 10.3390/pharmaceutics6040663
    Dissolvable microneedle arrays for intradermal delivery of biologics: fabrication and application. Bediz Bekir,Korkmaz Emrullah,Khilwani Rakesh,Donahue Cara,Erdos Geza,Falo Louis D,Ozdoganlar O Burak Pharmaceutical research PURPOSE:Design and evaluate a new micro-machining based approach for fabricating dissolvable microneedle arrays (MNAs) with diverse geometries and from different materials for dry delivery to skin microenvironments. The aims are to describe the new fabrication method, to evaluate geometric and material capability as well as reproducibility of the method, and to demonstrate the effectiveness of fabricated MNAs in delivering bioactive molecules. METHODS:Precise master molds were created using micromilling. Micromolding was used to create elastomer production molds from master molds. The dissolvable MNAs were then fabricated using the spin-casting method. Fabricated MNAs with different geometries were evaluated for reproducibility. MNAs from different materials were fabricated to show material capability. MNAs with embedded bioactive components were tested for functionality on human and mice skin. RESULTS:MNAs with different geometries and from carboxymethyl cellulose, polyvinyl pyrrolidone and maltodextrin were created reproducibly using our method. MNAs successfully pierce the skin, precisely deliver their bioactive cargo to skin and induce specific immunity in mice. CONCLUSIONS:We demonstrated that the new fabrication approach enables creating dissolvable MNAs with diverse geometries and from different materials reproducibly. We also demonstrated the application of MNAs for precise and specific delivery of biomolecules to skin microenvironments in vitro and in vivo. 10.1007/s11095-013-1137-x
    Microneedle/nanoencapsulation-mediated transdermal delivery: mechanistic insights. Gomaa Yasmine A,Garland Martin J,McInnes Fiona J,Donnelly Ryan F,El-Khordagui Labiba K,Wilson Clive G European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V A systematic study was undertaken to gain more insight into the mechanism of transdermal delivery of nanoencapsulated model dyes across microneedle (MN)-treated skin, a complex process not yet explored. Rhodamine B (Rh B) and fluorescein isothiocyanate (FITC) as model hydrophilic and hydrophobic small/medium-size molecules, respectively, were encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) and delivered through full thickness porcine skin pretreated with MN array. Permeation through MN-treated skin was affected by physicochemical characteristics of NPs and the encapsulated dyes. Dye flux was enhanced by smaller particle size, hydrophilicity, and negative zeta potential of NPs. Regarding encapsulated dyes, solubility at physiological pH and potential interaction with skin proteins proved to outweigh molecular weight as determinants of skin permeation. Data were verified using confocal laser scanning microscopy imaging. Findings coupled with the literature data are supportive of a mechanism involving influx of NPs, particularly of smaller size, deep into MN-created channels, generating depot dye-rich reservoirs. Molecular diffusion of the released dye across viable skin layers proceeds at a rate determined by its molecular characteristics. Data obtained provide mechanistic information of importance to the development of formulation strategies for more effective intradermal and transdermal MN-mediated delivery of nanoencapsulated therapeutic agents. 10.1016/j.ejpb.2013.01.026
    Improved polyvinylpyrrolidone microneedle arrays with non-stoichiometric cyclodextrin. Chen Wei,Wang Chong,Yan Li,Huang Longbiao,Zhu Xiaoyue,Chen Bing,Sant Himanshu J,Niu Xinrui,Zhu Guangyu,Yu K N,Roy V A L,Gale Bruce K,Chen Xianfeng Journal of materials chemistry. B Dissolving polymer microneedles have attracted much attention for their biocompatibility, fast dissolution, and high drug loading. Among them, polyvinylpyrrolidone (PVP) is widely used, but its high water absorption and poor mechanical properties constrain its broad applications. Herein we show that adding cyclodextrin (CD) to form PVP-CD inclusion complexes can alleviate these problems. The water absorption of PVP was reduced by 36-40% at different RHs as the PVP-CD inclusion complexes formed. Attractively, the water absorption at 10 and 20 days remained almost the same for the complexes while it could dramatically increase for the pure PVP samples, particularly in high humidity environments, indicating a possibly longer storage time for the complexes. It was also found that the Young's modulus and hardness of the PVP-CD could be greatly improved, especially for low molecular weight PVP. Furthermore, the glass transition temperature (T) of the PVP-CD increased by up to 39 °C. With the improved properties, the fabricated PVP-CD microneedles possessed much sharper needle tips and the patch had less cracks than those made from pure PVP. Pig skin application results suggested that the PVP-CD microneedle arrays were able to reliably pierce the stratum corneum of the skin while it was not achievable for the PVP microneedles with the same geometry. We anticipate that these PVP-CD complex microneedles are more suitable for vaccine and drug delivery because of their superior properties. 10.1039/c3tb21698e
    Patient safety and beyond: what should we expect from microneedle arrays in the transdermal delivery arena? Donnelly Ryan F,Woolfson A David Therapeutic delivery Research based upon microneedle (MN) arrays has intensified recently. While the initial focus was on biomolecules, the field has expanded to include delivery of conventional small-molecule drugs whose water solubility currently precludes transdermal administration. Much success has been achieved, with peptides, proteins, vaccines, antibodies and even particulates delivered by MN in therapeutic/prophylactic doses. Recent innovations have focused on enhanced formulation design, scalable manufacture and extension of exploitation to minimally invasive patient monitoring, ocular delivery and enhanced administration of cosmeceuticals. Only two MN-based drug/vaccine delivery products are currently marketed, partially due to limitations with older MN designs based upon silicon and metal. Even the more promising polymeric MN have raised a number of regulatory and manufacturability queries that the field must address. MN arrays have tremendous potential to yield real benefits for patients and industry and, through diligence, innovation and collaboration, this will begin to be realised over the next 3-5 years. 10.4155/tde.14.29
    Design and physicochemical characterisation of novel dissolving polymeric microneedle arrays for transdermal delivery of high dose, low molecular weight drugs. McCrudden Maelíosa T C,Alkilani Ahlam Zaid,McCrudden Cian M,McAlister Emma,McCarthy Helen O,Woolfson A David,Donnelly Ryan F Journal of controlled release : official journal of the Controlled Release Society We describe formulation and evaluation of novel dissolving polymeric microneedle (MN) arrays for the facilitated delivery of low molecular weight, high dose drugs. Ibuprofen sodium was used as the model here and was successfully formulated at approximately 50% w/w in the dry state using the copolymer poly(methylvinylether/maleic acid). These MNs were robust and effectively penetrated skin in vitro, dissolving rapidly to deliver the incorporated drug. The delivery of 1.5mg ibuprofen sodium, the theoretical mass of ibuprofen sodium contained within the dry MN alone, was vastly exceeded, indicating extensive delivery of the drug loaded into the baseplates. Indeed in in vitro transdermal delivery studies, approximately 33mg (90%) of the drug initially loaded into the arrays was delivered over 24h. Iontophoresis produced no meaningful increase in delivery. Biocompatibility studies and in vivo rat skin tolerance experiments raised no concerns. The blood plasma ibuprofen sodium concentrations achieved in rats (263μgml(-1) at the 24h time point) were approximately 20 times greater than the human therapeutic plasma level. By simplistic extrapolation of average weights from rats to humans, a MN patch design of no greater than 10cm(2) could cautiously be estimated to deliver therapeutically-relevant concentrations of ibuprofen sodium in humans. This work, therefore, represents a significant progression in exploitation of MN for successful transdermal delivery of a much wider range of drugs. 10.1016/j.jconrel.2014.02.007
    Novel hollow microneedle technology for depth-controlled microinjection-mediated dermal vaccination: a study with polio vaccine in rats. van der Maaden Koen,Trietsch Sebastiaan J,Kraan Heleen,Varypataki Eleni Maria,Romeijn Stefan,Zwier Raphäel,van der Linden Heiko J,Kersten Gideon,Hankemeier Thomas,Jiskoot Wim,Bouwstra Joke Pharmaceutical research PURPOSE:The aim of the study was to develop a cheap and fast method to produce hollow microneedles and an applicator for injecting vaccines into the skin at a pre-defined depth and test the applicability of the system for dermal polio vaccination. METHODS:Hollow microneedles were produced by hydrofluoric acid etching of fused silica capillaries. An electromagnetic applicator was developed to control the insertion speed (1-3 m/s), depth (0-1,000 μm), and angle (10°-90°). Hollow microneedles with an inner diameter of 20 μm were evaluated in ex vivo human skin and subsequently used to immunize rats with inactivated poliovirus vaccine (IPV) by an intradermal microinjection of 9 μL at a depth of 300 μm and an insertion speed of 1 m/s. Rat sera were tested for IPV-specific IgG and virus-neutralizing antibodies. RESULTS:Microneedles produced from fused silica capillaries were successfully inserted into the skin to a chosen depth, without clogging or breakage of the needles. Intradermal microinjection of IPV induced immune responses comparable to those elicited by conventional intramuscular immunization. CONCLUSIONS:We successfully developed a hollow microneedle technology for dermal vaccination that enables fundamental research on factors, such as insertion depth and volume, and insertion angle, on the immune response. 10.1007/s11095-013-1288-9
    Optical clearing agent perfusion enhancement via combination of microneedle poration, heating and pneumatic pressure. Damestani Yasaman,Melakeberhan Bissrat,Rao Masaru P,Aguilar Guillermo Lasers in surgery and medicine BACKGROUND AND OBJECTIVE:Optical clearing agents (OCAs) have shown promise for increasing the penetration depth of biomedical lasers by temporarily decreasing optical scattering within the skin. However, their translation to the clinic has been constrained by lack of practical means for effectively perfusing OCA within target tissues in vivo. The objective of this study was to address this limitation through combination of a variety of techniques to enhance OCA perfusion, including heating of OCA, microneedling and/or application of pneumatic pressure over the skin surface being treated (vacuum and/or positive pressure). While some of these techniques have been explored by others independently, the current study represents the first to explore their use together. STUDY DESIGN/MATERIALS AND METHODS:Propylene glycol (PG) OCA, either at room-temperature or heated to 45°C, was topically applied to hydrated, body temperature ex vivo porcine skin, in conjunction with various combinations of microneedling pre-treatment (0.2 mm length microneedles, performed prior to OCA application), vacuum pre-treatment (17-50 kPa, performed prior to OCA application), and positive pressure post-treatment (35-172 kPa, performed after OCA application). The effectiveness of OCA perfusion was characterized via measurements of transmittance, reduced scattering coefficient, and penetration depth at a number of medically-relevant laser wavelengths across the visible spectrum. RESULTS:Topical application of room-temperature (RT) PG led to an increase in transmittance across the visible spectrum of up to 21% relative to untreated skin. However, only modest increases were observed with addition of various combinations of microneedling pre-treatment, vacuum pre-treatment, and positive pressure post-treatment. Conversely, when heated PG was used in conjunction with these techniques, we observed significant increases in transmittance. Using an optimal PG perfusion enhancement protocol consisting of 45°C heated PG + microneedle pre-treatment + 35 kPa vacuum pre-treatment + 103 kPa positive pressure post-treatment, we observed up to 68% increase in transmittance relative to untreated skin, and up to 46% increase relative to topical RT PG application alone. Using the optimal PG perfusion enhancement protocol, we also observed up to 30% decrease in reduced scattering coefficient relative to untreated skin, and up to 20% decrease relative to topical RT PG alone. Finally, using the optimal protocol, we observed up to 25% increase in penetration depth relative to untreated skin, and up to 23% increase relative to topical RT PG alone. CONCLUSIONS:The combination of heated PG, microneedling pre-treatment, vacuum pre-treatment, and positive pressure-post treatment were observed to significantly enhance the perfusion of topically applied PG. Although further studies are required to evaluate the efficacy of combined perfusion enhancement techniques in vivo, the current results suggest promise for facilitating the translation of OCAs to the clinic. 10.1002/lsm.22258
    A proposed model membrane and test method for microneedle insertion studies. Larrañeta Eneko,Moore Jessica,Vicente-Pérez Eva M,González-Vázquez Patricia,Lutton Rebecca,Woolfson A David,Donnelly Ryan F International journal of pharmaceutics A commercial polymeric film (Parafilm M(®), a blend of a hydrocarbon wax and a polyolefin) was evaluated as a model membrane for microneedle (MN) insertion studies. Polymeric MN arrays were inserted into Parafilm M(®) (PF) and also into excised neonatal porcine skin. Parafilm M(®) was folded before the insertions to closely approximate thickness of the excised skin. Insertion depths were evaluated using optical coherence tomography (OCT) using either a force applied by a Texture Analyser or by a group of human volunteers. The obtained insertion depths were, in general, slightly lower, especially for higher forces, for PF than for skin. However, this difference was not a large, being less than the 10% of the needle length. Therefore, all these data indicate that this model membrane could be a good alternative to biological tissue for MN insertion studies. As an alternative method to OCT, light microscopy was used to evaluate the insertion depths of MN in the model membrane. This provided a rapid, simple method to compare different MN formulations. The use of Parafilm M(®), in conjunction with a standardised force/time profile applied by a Texture Analyser, could provide the basis for a rapid MN quality control test suitable for in-process use. It could also be used as a comparative test of insertion efficiency between candidate MN formulations. 10.1016/j.ijpharm.2014.05.042
    Force-Sensing Microneedle for Assisted Retinal Vein Cannulation* Gonenc Berk,Gehlbach Peter,Handa James,Taylor Russell H,Iordachita Iulian Proceedings of IEEE Sensors. IEEE International Conference on Sensors Retinal vein cannulation (RVC) is a challenging procedure proposed for drug delivery into the very small retinal veins. The available glass cannulas for this procedure are both hard to visualize and fragile thereby limiting the feasibility of both robot-assisted and manual RVC approaches. In this study, we develop and test a new force-sensing RVC instrument that can be easily integrated with the existing manual and robotic devices. The tool enables (1) the measurement of the forces required for puncturing retinal veins and (2) an assistive method to inform the operator of the needle piercing the vessel wall. The fiber Bragg grating based sensor can be inserted into the eye through a small (∅ 0.9 mm) opening and provides a quantitative assessment at the tool tip with a resolution smaller than 0.25 mN. Assessment of forces during vessel penetration in the chorioallantoic membranes of chicken embryos have revealed a consistent sharp drop in tool tip force upon vessel puncture that has been used as a signature to provide auditory feedback to the user to stop needle advancement and begin drug delivery. 10.1109/ICSENS.2014.6985095
    Smart microneedle coatings for controlled delivery and biomedical analysis. Khan H,Mehta P,Msallam H,Armitage D,Ahmad Z Journal of drug targeting The work presented demonstrates an unconventional approach in the preparation of smart microneedle (MN) coatings utilising electrohydrodynamic atomisation (EHDA) principles. Stainless steel (600-900 µm in height) MNs were coupled to a ground electrode (in the EHDA coating set-up) with the deposition distance and collecting methodology varied for an ethanol:methanol (50:50) vehicle system. The preparation of nano- and micrometre-scaled pharmaceutical coatings was achieved. Fluorescein dye (serving as potential drug, sensory materials or disease state markers) and polyvinylpyrrolidone (PVP, polymer matrix system) formed the remaining components of the coating formulation. Based on these excipients and by varying the coating process, particles (100 nm to 3 µm) and fibres (400 nm to 1 µm) were deposited directly on MNs in controlled and selectable fashion (flow rates variable ∼ 5-50 µL/min, applied voltage variable 6-19 kV). These demonstrated options for multiple targeting and analysis applications. The underlying EHDA process permits room temperature fabrication, controlled output and scale-up potential for emerging MN devices as drug systems or lab-chip testing devices. 10.3109/1061186X.2014.921926
    Synthesis and in vitro stability of amino acid prodrugs of 6-β-naltrexol for microneedle-enhanced transdermal delivery. Eldridge Joshua A,Milewski Mikolaj,Stinchcomb Audra L,Crooks Peter A Bioorganic & medicinal chemistry letters A small library of amino acid ester prodrugs of 6-β-naltrexol (NTXOL, 1) was prepared in order to investigate the candidacy of these prodrugs for microneedle-enhanced transdermal delivery. Six amino acid ester prodrugs were synthesized (6a-f). 6b, 6d, and 6 e were stable enough at skin pH (pH 5.0) to move forward to studies in 50% human plasma. The lead compound (6 e) exhibited the most rapid bioconversion to NTXOL in human plasma (t1/2 = 2.2 ± 0.1h). 10.1016/j.bmcl.2014.09.072
    Microneedle-mediated minimally invasive patient monitoring. Donnelly Ryan F,Mooney Karen,Caffarel-Salvador Ester,Torrisi Barbara M,Eltayib Eyman,McElnay James C Therapeutic drug monitoring BACKGROUND:The emerging field of microneedle-based minimally invasive patient monitoring and diagnosis is reviewed. Microneedle arrays consist of rows of micron-scale projections attached to a solid support. They have been widely investigated for transdermal drug and vaccine delivery applications since the late 1990s. However, researchers and clinicians have recently realized the great potential of microneedles for extraction of skin interstitial fluid and, less commonly, blood, for enhanced monitoring of patient health. METHODS:We reviewed the journal and patent literature, and summarized the findings and provided technical insights and critical analysis. RESULTS:We describe the basic concepts in detail and extensively review the work performed to date. CONCLUSIONS:It is our view that microneedles will have an important role to play in clinical management of patients and will ultimately improve therapeutic outcomes for people worldwide. 10.1097/FTD.0000000000000022
    Microneedle electrodes toward an amperometric glucose-sensing smart patch. Invernale Michael A,Tang Benjamin C,York Royce L,Le Long,Hou David Yupeng,Anderson Daniel G Advanced healthcare materials Here, efforts toward the development of a microneedle-based glucose sensor or "smart patch" for intradermal glucose sensing are described. Metallic microneedle array electrodes, conducting polymers, and glucose oxidase form the sensor platform. This work represents the first steps toward the development of painless, transdermal-sensing devices for continuous glucose monitoring. 10.1002/adhm.201300142
    The efficacy in treatment of facial atrophic acne scars in Asians with a fractional radiofrequency microneedle system. Vejjabhinanta V,Wanitphakdeedecha R,Limtanyakul P,Manuskiatti W Journal of the European Academy of Dermatology and Venereology : JEADV BACKGROUND:Treatment of acne scars remains a challenge to dermatologists. Multiple modalities have been employed with variable results and adverse effects. OBJECTIVE:To determine the efficacy and adverse effects of a fractional radiofrequency microneedle system (FRMS) on acne scars in Asians at 1-, 3- and 6-month follow-up visits after treatment. METHODS:Thirty subjects with atrophic acne scars for more than 6 months were enrolled in the study. All volunteers were treated with a FRMS on affected areas. The subjects were treated for a total number of three treatment sessions at 1-month intervals. Subjective assessments were obtained at baseline, 1, 3 and 6 months after the last treatment session by self-evaluation and two blinded dermatologists. Objective evaluation using an ultraviolet A-light video camera was also performed. In addition, pain scores, immediate reactions, healing times and other adverse effects were evaluated. RESULTS:Twenty-six subjects with skin phototypes III-V completed treatment protocol. The average mean scar age was 7 years (range: 0.5-15 years). At 6-month follow-up visit, the majority of the subjects (42.3%) reported a 26-50% improvement on their acne scars. Percent reduction in scar volume corresponded to clinical evaluation. Adverse reactions of the treatment included pain, immediate oedema/erythema, minimal scabbing and transient pigmentary alteration on treated areas. The average pain score was 5.6 of 10. Worsening of skin texture or new scar formation was not observed in any subjects. CONCLUSION:Fractional radiofrequency microneedle system is a safe and effective device for treating acne scars in Asians with minimal risk of downtime and adverse effects. 10.1111/jdv.12267
    Evaluation of the effect of polymeric microneedle arrays of varying geometries in combination with a high-velocity applicator on skin permeability and irritation. Watanabe Toshihiro,Hagino Kei,Sato Toshiyuki Biomedical microdevices Polymeric microneedles offer the advantages of being both mass-producible and inexpensive. However, their weakness lies in the fact that they are not adequate for sharp fabrication of a needle tip, which is an important factor for effective penetration. We hypothesized that effective penetration can be achieved using a high-velocity application system. Therefore, in the present study, we investigated the influence of various polymeric microneedle array geometries on skin permeability and irritation using such a system. Volar forearms of 16 healthy volunteers were treated using the microneedle system with four different parameters: applicator velocity (4.3, 6, and 8.5 m/s), tip radius (10, 15, and 20 μm), length (100, 200, and 300 μm), and number of needles (189 and 305 on a 50-mm(2) area). A higher velocity of piercing clearly enhanced skin permeability and damage. A larger tip radius resulted in lower skin permeability and irritation at an applicator velocity of 4.3 m/s but did not have an effect at 6 m/s. Skin permeability was positively variable, ranging from 100 to 200 μm of needle length, and needle number showed no influence in the range investigated. In conclusion, a faster application speed could significantly enhance skin permeability and damage and compensate for insufficient penetration of the larger tip radius and shorter needles, which are also important factors for effective insertion. 10.1007/s10544-014-9861-5
    Microneedle enhanced delivery of cosmeceutically relevant peptides in human skin. Mohammed Yousuf H,Yamada Miko,Lin Lynlee L,Grice Jeffrey E,Roberts Michael S,Raphael Anthony P,Benson Heather A E,Prow Tarl W PloS one Peptides and proteins play an important role in skin health and well-being. They are also found to contribute to skin aging and melanogenesis. Microneedles have been shown to substantially enhance skin penetration and may offer an effective means of peptide delivery enhancement. The aim of this investigation was to assess the influence of microneedles on the skin penetration of peptides using fluorescence imaging to determine skin distribution. In particular the effect of peptide chain length (3, 4, 5 amino acid chain length) on passive and MN facilitated skin penetration was investigated. Confocal laser scanning microscopy was used to image fluorescence intensity and the area of penetration of fluorescently tagged peptides. Penetration studies were conducted on excised full thickness human skin in Franz type diffusion cells for 1 and 24 hours. A 2 to 22 fold signal improvement in microneedle enhanced delivery of melanostatin, rigin and pal-KTTKS was observed. To our knowledge this is the first description of microneedle enhanced skin permeation studies on these peptides. 10.1371/journal.pone.0101956
    Vaccine efficacy of transcutaneous immunization with amyloid β using a dissolving microneedle array in a mouse model of Alzheimer's disease. Matsuo Kazuhiko,Okamoto Hideaki,Kawai Yasuaki,Quan Ying-Shu,Kamiyama Fumio,Hirobe Sachiko,Okada Naoki,Nakagawa Shinsaku Journal of neuroimmunology Vaccine therapy for Alzheimer's disease (AD) based on the amyloid cascade hypothesis has recently attracted attention for treating AD. Injectable immunization using amyloid β peptide (Aβ) comprising 1-42 amino-acid residues (Aβ1-42) as antigens showed therapeutic efficacy in mice; however, the clinical trial of this injected Aβ1-42 vaccine was stopped due to the incidence of meningoencephalitis caused by excess activation of Th1 cells infiltrating the brain as a serious adverse reaction. Because recent studies have suggested that transcutaneous immunization (TCI) is likely to elicit Th2-dominant immune responses, TCI is expected to be effective in treating AD without inducing adverse reactions. Previously reported TCI procedures employed complicated and impractical vaccination procedures; therefore, a simple, easy-to-use, and novel TCI approach needs to be established. In this study, we investigated the vaccine efficacy of an Aβ1-42-containing TCI using our novel dissolving microneedle array (MicroHyala; MH) against AD. MH-based TCI induced anti-Aβ1-42 immune responses by simple and low-invasive application of Aβ1-42-containing MH to the skin. Unfortunately, this TCI system resulted in little significant improvement in cognitive function and Th2-dominant immune responses, suggesting the need for further modification. 10.1016/j.jneuroim.2013.11.002
    Microneedle-mediated intrascleral delivery of in situ forming thermoresponsive implants for sustained ocular drug delivery. Thakur Raghu Raj Singh,Fallows Steven J,McMillan Hannah L,Donnelly Ryan F,Jones David S The Journal of pharmacy and pharmacology OBJECTIVES:This paper describes use of minimally invasive hollow microneedle (HMN) to deliver in situ forming thermoresponsive poloxamer-based implants into the scleral tissue to provide sustained drug delivery. METHODS:In situ forming poloxamer formulations were prepared and investigated for their rheological properties. HMN devices 400, 500 and 600 μm in height were fabricated from hypodermic needles (i.e. 27, 29 and 30 G) and tested for depth of penetration into rabbit sclera. Maximum force and work required to expel different volumes of poloxamer formulations was also investigated. Release of fluorescein sodium (FS) from intrasclerally injected implants was also investigated. Optical coherence tomography (OCT) was used to examine implant localisation and scleral pore-closure. KEY FINDINGS:Poloxamer formulations showed Newtonian behaviour at 20°C and pseudoplastic (shear-thinning) behaviour at 37°C. Maximum force and work required to expel different volumes of poloxamer formulations with different needles ranged from 0.158 to 2.021 N and 0.173 to 6.000 N, respectively. OCT showed intrascleral localisation of implants and scleral pore-closure occurred within 2-3 h. Sustain release of FS was noticed over 24 h and varied with depth of implant delivery. CONCLUSIONS:This study shows that the minimally invasive HMN device can localise in situ forming implants in the scleral tissue and provide sustained drug delivery. 10.1111/jphp.12152
    Wavelet denoising and reconstruction of a microneedle embedded in human skin ex-vivo using terahertz pulsed reflectance. Mueller-Holtz Martin,Seker Huseyin,Smith Geoff Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference Biological tissue can show promising features in the terahertz region of the electro-magnetic spectrum but face the problem that the signal to noise ratio can be poor due to the low energy output from the measurement instrument coupled with the high absorbance of water in biological tissue. Wavelet denoising and reconstruction are known to be suitable digital signal processing filters for reflected terahertz energy when appropriate thresholds, scales and mother-wavelets are chosen. In this article, we therefore describe a Wavelet transform-based method for denoising reflections of THz energy from ex-vivo human skin with an embedded microneedle. The wavelet reconstruction was then successfully used to identify the microneedle from the reflected waveform. This technique is potentially useful to enhance in-depth analysis and visualisation of underlying skin layers, lesions and penetration depth for targeted drug delivery. 10.1109/EMBC.2014.6945175
    Optimization of naltrexone diclofenac codrugs for sustained drug delivery across microneedle-treated skin. Ghosh Priyanka,Lee DoMin,Kim Kyung Bo,Stinchcomb Audra L Pharmaceutical research PURPOSE:The purpose of this work was to optimize the structure of codrugs for extended delivery across microneedle treated skin. Naltrexone, the model compound was linked with diclofenac, a nonspecific cyclooxygenase inhibitor to enhance the pore lifetime following microneedle treatment and develop a 7 day transdermal system for naltrexone. METHODS:Four different codrugs of naltrexone and diclofenac were compared in terms of stability and solubility. Transdermal flux, permeability and skin concentration of both parent drugs and codrugs were quantified to form a structure permeability relationship. RESULTS:The results indicated that all codrugs bioconverted in the skin. The degree of conversion was dependent on the structure, phenol linked codrugs were less stable compared to the secondary alcohol linked structures. The flux of naltrexone across microneedle treated skin and the skin concentration of diclofenac were higher for the phenol linked codrugs. The polyethylene glycol link enhanced solubility of the codrugs, which translated into flux enhancement. CONCLUSION:The current studies indicated that formulation stability of codrugs and the flux of naltrexone can be enhanced via structure design optimization. The polyethylene glycol linked naltrexone diclofenac codrug is better suited for a 7 day drug delivery system both in terms of stability and drug delivery. 10.1007/s11095-013-1147-8
    Microneedle patches for vaccine delivery. Suh Hyemee,Shin Juhyung,Kim Yeu-Chun Clinical and experimental vaccine research In today's medical industry, the range of vaccines that exist for administration in humans represents an eclectic variety of forms and immunologic mechanisms. Namely, these are the live attenuated viruses, inactivated viruses, subunit proteins, and virus-like particles for treating virus-caused diseases, as well as the bacterial-based polysaccharide, protein, and conjugated vaccines. Currently, a new approach to vaccination is being investigated with the concept of DNA vaccines. As an alternative delivery route to enhance the vaccination efficacy, microneedles have been devised to target the rich network of immunologic antigen-presenting cells in the dermis and epidermis layers under the skin. Numerous studies have outlined the parameters of microneedle delivery of a wide range of vaccines, revealing comparable or higher immunogenicity to conventional intramuscular routes, overall level of stability, and dose-sparing advantages. Furthermore, recent mechanism studies have begun to successfully elucidate the biological mechanisms behind microneedle vaccination. This paper describes the current status of microneedle vaccine research. 10.7774/cevr.2014.3.1.42
    Microneedle applications for DNA vaccine delivery to the skin. Seok Hae-yong,Suh Hyemee,Baek Sunghyun,Kim Yeu-Chun Methods in molecular biology (Clifton, N.J.) Microneedles were initially developed as pretreatment tools for the delivery of therapeutic drugs to intradermal locales in the human skin. Over time, variations in microneedle forms and functions burgeoned through the works of many researchers worldwide. The four major types of microneedles in use today are solid, dissolving, coating, and hollow microneedles. The emergence of different types of microneedles also paved the way for a flourishing diversification of microneedle applications, one of the most remarkable of which deals with the transcutaneous delivery of prophylactic vaccines. Here, we describe fabrication methods of microneedles and DNA vaccine loading methods on the microneedle surface. Furthermore, in the latter part of this chapter, in vivo test protocols for assessing the efficacy of gene delivery using microneedles are described. 10.1007/978-1-4939-0410-5_10