A fluorescence sandwich immunoassay for the real-time continuous detection of glucose and insulin in live animals.
Poudineh Mahla,Maikawa Caitlin L,Ma Eric Yue,Pan Jing,Mamerow Dan,Hang Yan,Baker Sam W,Beirami Ahmad,Yoshikawa Alex,Eisenstein Michael,Kim Seung,Vučković Jelena,Appel Eric A,Soh H Tom
Nature biomedical engineering
Biosensors that continuously measure circulating biomolecules in real time could provide insights into the health status of patients and their response to therapeutics. But biosensors for the continuous real-time monitoring of analytes in vivo have only reached nanomolar sensitivity and can measure only a handful of molecules, such as glucose and blood oxygen. Here we show that multiple analytes can be continuously and simultaneously measured with picomolar sensitivity and sub-second resolution via the integration of aptamers and antibodies into a bead-based fluorescence sandwich immunoassay implemented in a custom microfluidic chip. After an incubation time of 30 s, bead fluorescence is measured using a high-speed camera under spatially multiplexed two-colour laser illumination. We used the assay for continuous quantification of glucose and insulin concentrations in the blood of live diabetic rats to resolve inter-animal differences in the pharmacokinetic response to insulin as well as discriminate pharmacokinetic profiles from different insulin formulations. The assay can be readily modified to continuously and simultaneously measure other blood analytes in vivo.
Gold Nanozymes: From Concept to Biomedical Applications.
Lou-Franco Javier,Das Bhaskar,Elliott Christopher,Cao Cuong
In recent years, gold nanoparticles have demonstrated excellent enzyme-mimicking activities which resemble those of peroxidase, oxidase, catalase, superoxide dismutase or reductase. This, merged with their ease of synthesis, tunability, biocompatibility and low cost, makes them excellent candidates when compared with biological enzymes for applications in biomedicine or biochemical analyses. Herein, over 200 research papers have been systematically reviewed to present the recent progress on the fundamentals of gold nanozymes and their potential applications. The review reveals that the morphology and surface chemistry of the nanoparticles play an important role in their catalytic properties, as well as external parameters such as pH or temperature. Yet, real applications often require specific biorecognition elements to be immobilized onto the nanozymes, leading to unexpected positive or negative effects on their activity. Thus, rational design of efficient nanozymes remains a challenge of paramount importance. Different implementation paths have already been explored, including the application of peroxidase-like nanozymes for the development of clinical diagnostics or the regulation of oxidative stress within cells via their catalase and superoxide dismutase activities. The review also indicates that it is essential to understand how external parameters may boost or inhibit each of these activities, as more than one of them could coexist. Likewise, further toxicity studies are required to ensure the applicability of gold nanozymes in vivo. Current challenges and future prospects of gold nanozymes are discussed in this review, whose significance can be anticipated in a diverse range of fields beyond biomedicine, such as food safety, environmental analyses or the chemical industry.
Nanophotonic-Carbohydrate Lab-on-a-Microneedle for Rapid Detection of Human Cystatin C in Finger-Prick Blood.
Puttaswamy Srinivasu Valagerahally,Lubarsky Gennady V,Kelsey Colin,Zhang Xushuo,Finlay Dewar,McLaughlin James A,Bhalla Nikhil
Miniaturized total analysis systems, for the rapid detection of disease biomarkers, with features including high biomarker sensitivity, selectivity, biocompatibility, and disposability, all at low cost are of profound importance in the healthcare sector. Within this frame of reference, we developed a lab-on-a-carbohydrate-microneedle biodevice by integrating localized surface plasmon resonance (LSPR) paper-based substrates with biocompatible microneedles of high aspect ratio (>60:1 length:width). These microneedles are completely fabricated with carbohydrate (maltose) and further coated with poly lactic--glycolic acid (PLGA), which together serves the purpose of fluid channels. The porous nature of PLGA, in addition to drawing blood by capillary action, filters out the whole blood, allowing only the blood plasma to reach the biorecognition layer of the developed biodevice. While the use of maltose provides biocompatibility to the microneedle, the axial compression and transverse load analysis revealed desired mechanical strength of the microneedle, with mechanical failure occurring at 11N and 9 N respectively for the compressive and transverse load. For a proof-of-principle demonstration, the developed biodevice is validated for its operational features by direct detection of cystatin C in finger-prick blood and up to a concentration of 0.01 μg/mL in buffered conditions using the LSPR technique. Furthermore, by changing the biorecognition layer, the use of the developed needle can be extended to other disease biomarkers, and therefore the innovation presented in this work represents a hallmark in the state of the art of lab-on-a-chip biodevices.
Soft and flexible material-based affinity sensors.
Meng Lingyin,Turner Anthony P F,Mak Wing Cheung
Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field.
Microscale Interfacial Polymerization on a Chip.
Rocca Marco,Dufresne Maxime,Salva Marie,Niemeyer Christof M,Delamarche Emmanuel
Angewandte Chemie (International ed. in English)
Forming hydrogels with precise geometries is challenging and mostly done using photopolymerization, which involves toxic chemicals, rinsing steps, solvents, and bulky optical equipment. Here, we introduce a new method for in situ formation of hydrogels with a well-defined geometry in a sealed microfluidic chip by interfacial polymerization. The geometry of the hydrogel is programmed by microfluidic design using capillary pinning structures and bringing into contact solutions containing hydrogel precursors from vicinal channels. The characteristics of the hydrogel (mesh size, molecular weight cut-off) can be readily adjusted. This method is compatible with capillary-driven microfluidics, fast, uses small volumes of reagents and samples, and does not require specific laboratory equipment. Our approach creates opportunities for filtration, hydrogel functionalization, and hydrogel-based assays, as exemplified by a rapid, compact competitive immunoassay that does not require a rinsing step.
Digital immunoassay for biomarker concentration quantification using solid-state nanopores.
He Liqun,Tessier Daniel R,Briggs Kyle,Tsangaris Matthaios,Charron Martin,McConnell Erin M,Lomovtsev Dmytro,Tabard-Cossa Vincent
Single-molecule counting is the most accurate and precise method for determining the concentration of a biomarker in solution and is leading to the emergence of digital diagnostic platforms enabling precision medicine. In principle, solid-state nanopores-fully electronic sensors with single-molecule sensitivity-are well suited to the task. Here we present a digital immunoassay scheme capable of reliably quantifying the concentration of a target protein in complex biofluids that overcomes specificity, sensitivity, and consistency challenges associated with the use of solid-state nanopores for protein sensing. This is achieved by employing easily-identifiable DNA nanostructures as proxies for the presence ("1") or absence ("0") of the target protein captured via a magnetic bead-based sandwich immunoassay. As a proof-of-concept, we demonstrate quantification of the concentration of thyroid-stimulating hormone from human serum samples down to the high femtomolar range. Further optimization to the method will push sensitivity and dynamic range, allowing for development of precision diagnostic tools compatible with point-of-care format.
Magnetic assisted fluorescence immunoassay for sensitive chloramphenicol detection using carbon dots@CaCO nanocomposites.
Dong Baolei,Li Hongfang,Sun Jiefang,Li Yuan,Mari Ghulam Mujtaba,Yu Xuezhi,Yu Wenbo,Wen Kai,Shen Jianzhong,Wang Zhanhui
Journal of hazardous materials
Analytical methods with high sensitivities and short assay times are urgently required for the screening of "zero tolerance" hazardous substances in food. Herein, we propose a fluorescent immunoassay for the highly sensitive and rapid analysis of chloramphenicol (CAP) based on carbon dots (CDs)-encapsulated CaCO nanospheres and magnetic nanoparticles (MNPs). The fluorescent immunoprobes were prepared by coupling the anti-CAP antibodies to carboxymethyl cellulose-functional CDs@CaCO nanospheres. Chitosan-modified MNPs with "core-shell" structures were prepared and then conjugated to the CAP hapten, acting as the nano-carrier and interface for the immunoreaction. With the assistance of MNPs, the established fluorescent immunoassay achieved the sensitive detection of CAP in chicken with a limit of detection of 0.03 μg kg and recoveries ranging from 83.7%-105.0%. The analysis results of the fluorescent immunoassay were evaluated by the enzyme-linked immunosorbent assay, having a correlation coefficient of 0.981. Our work provides a rapid, facile, and reliable strategy for the highly sensitive analysis of food contaminants based on "green" fluorescent nanoprobes.
Homogeneous Quenching Immunoassay for Fumonisin B Based on Gold Nanoparticles and an Epitope-Mimicking Yellow Fluorescent Protein.
Peltomaa Riikka,Amaro-Torres Francisco,Carrasco Sergio,Orellana Guillermo,Benito-Peña Elena,Moreno-Bondi María C
Homogeneous immunoassays represent an attractive alternative to traditional heterogeneous assays due to their simplicity, sensitivity, and speed. On the basis of a previously identified epitope-mimicking peptide, or mimotope, we developed a homogeneous fluorescence quenching immunoassay based on gold nanoparticles (AuNPs) and a recombinant epitope-mimicking fusion protein for the detection of mycotoxin fumonisin B (FB). The fumonisin mimotope was cloned as a fusion protein with a yellow fluorescent protein that could be used directly as the tracer for FB detection without the need of labeling or a secondary antibody. Furthermore, owing to the fluorescence quenching ability of AuNPs, a homogeneous immunoassay could be performed in a single step without washing steps to separate the unbound tracer. The homogeneous quenching assay showed negligible matrix effects in 5% wheat extract and high sensitivity for FB detection, with a dynamic range from 7.3 to 22.6 ng mL, a detection limit of 1.1 ng mL, and IC value of 12.9 ng mL, which was significantly lower than the IC value of the previously reported assay using the synthetic counterpart of the same mimotope in a microarray format. The homogeneous assay was demonstrated to be specific for fumonisins B and B, as no significant cross-reactivity with other mycotoxins was observed, and acceptable recoveries (86% for FB 2000 μg kg and 103% for FB 4000 μg kg), with relative standard deviation less than 6.5%, were reported from spiked wheat samples, proving that the method could provide a valuable tool for simple analysis of mycotoxin-contaminated food samples.
Label-free approach for electrochemical ferritin sensing using biosurfactant stabilized tungsten disulfide quantum dots.
Garg Mayank,Chatterjee Mary,Sharma Amit L,Singh Suman
Biosensors & bioelectronics
A novel approach for the synthesis of biosurfactant stabilized/functionalized tungsten disulfide (WS-B) quantum dots (QDs) and its application for ferritin immunosensor is reported. These 2-D layered material derived quantum dots are synthesized via one-step liquid exfoliation method and biosurfactant was used as a functionalization and stability providing moiety. The biosurfactant provided a clean and green method for both the synthesis and in-situ functionalization of the QDs. Exhaustive characterization using analytical techniques was done to study various aspects of the synthesized quantum dots. The functionalized quantum dots (WS-B QDs) were further explored for their possible application as an electroactive platform. For this, the working area of commercially available screen-printed electrodes (SPE) was functionalized with these WS-B QDs to construct a sensor platform. This sensor platform was then used for fabrication of ferritin immunosensor, using ferritin specific antibodies. Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) techniques were used for electrochemical immunosensing of ferritin. Though, the achieved linear range for ferritin detection (10-1500 ng mL) is same with both the techniques but regression coefficient and limit of detection are better in differential pulse voltammetry. The limit of detection was found to be 3.800 ng mL in DPV and 6.048 ng mL in CV. The immunosensor is highly selective, reproducible and is stable for about 60 days.
High peroxidase-like activity realized by facile synthesis of FeS nanoparticles for sensitive colorimetric detection of HO and glutathione.
Song Chan,Ding Wei,Zhao Weiwen,Liu Haibo,Wang Jie,Yao Yuewei,Yao Cheng
Biosensors & bioelectronics
In the last decades, enzyme mimics have been regarded as strong substitutes to natural enzymes. The construction of biosensors based on these enzyme mimics with competitive catalytic activity and substrate specificity has attracted a lot of research interest. Herein, for the first time, we investigated the capability of nanoscale FeS to serve as enzyme mimics. Then, a facile and effective biosensor is fabricated based on its intrinsic peroxidase-like catalytic activity. In the presence of HO, FeS nanoparticles (NPs) possess high peroxidase-like activity to 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, which can be ascribed to the generation of hydroxyl radicals (·OH) from the HO decomposition catalyzed by FeS NPs. As for TMB, the resulting Michaelis-Menten constant (K) value of FeS NPs is found to be about 12 times lower than that of natural horseradish peroxidase (HRP), highlighting the superiority of FeS NPs. Based on these intriguing observations, a reliable colorimetric method is then developed for detection of HO and glutathione (GSH) by a simple mix-and-detect strategy. The detection limits of HO and GSH are as low as 0.91 μM and 0.15 μM (3σ/slope), respectively. Moreover, FeS NPs can also catalyse the photoluminescence (PL) substrate terephthalic acid (TA) under the assistance of HO. This work remarkably extends the utilization of FeS NPs in the construction of colorimetric and PL biosensors in the fields of biosensing, environmental monitoring, and medical diagnosis.
Early stage detection of Staphylococcus epidermidis biofilm formation using MgZnO dual-gate TFT biosensor.
Li Guangyuan,Wu Yifan,Li Yuxuan,Hong Yuzhi,Zhao Xilin,Reyes Pavel Ivanoff,Lu Yicheng
Biosensors & bioelectronics
Early stage detection of biofilm formation is an important aspect of microbial research because once formed, biofilms show serious tolerance to antibiotics in contrast to the free-floating bacteria, which significantly increases the difficulty for clinical treatment of bacterial infections. The early stage detection technology is desired to improve the efficiency of medical treatments. In this work, we present a biosensor consisting of a magnesium zinc oxide (MZO) dual gate thin-film transistor (DGTFT) as the actuator and an MZO nanostructure (MZO) array coated conducting pad as the extended sensing gate for the early stage detection of Staphylococcus epidermidis (S. epidermidis) biofilm formation. S. epidermidis bacteria were cultured in vitro on the nanostructure modified sensing pad. Charge transfer occurs between microbial cells and the MZO during the initial bacterial adhesion stage. Such electrical signals, which represent the onset of biofilm formation, were dynamically detected by the DGTFT where the top gate electrode was connected to the extended MZO sensing pad and the bottom gate was used for biasing the device into the optimum characteristic region for high sensitivity and stable operation. The testing results show that a current change of ~80% is achieved after ~200 min of bacterial culturing. A crystal violet staining-based assay shows that tiny bacterial microcolonies just start to form at 200 min, and that it would take approximately 24 h to form matured biofilms. This technology enables medical professionals to act promptly on bacterial infection before biofilms get fully established.
Bioluminescent Antibodies for Point-of-Care Diagnostics.
Xue Lin,Yu Qiuliyang,Griss Rudolf,Schena Alberto,Johnsson Kai
Angewandte Chemie (International ed. in English)
We introduce a general method to transform antibodies into ratiometric, bioluminescent sensor proteins for the no-wash quantification of analytes. Our approach is based on the genetic fusion of antibody fragments to NanoLuc luciferase and SNAP-tag, the latter being labeled with a synthetic fluorescent competitor of the antigen. Binding of the antigen, here synthetic drugs, by the sensor displaces the tethered fluorescent competitor from the antibody and disrupts bioluminescent resonance energy transfer (BRET) between the luciferase and fluorophore. The semisynthetic sensors display a tunable response range (submicromolar to submillimolar) and large dynamic range (ΔR >500 %), and they permit the quantification of analytes through spotting of the samples onto paper followed by analysis with a digital camera.
Metal Nanozyme with Ester Hydrolysis Activity in the Presence of Ammonia-Borane and Its Use in a Sensitive Immunosensor.
Nandhakumar Ponnusamy,Kim Gyeongho,Park Seonhwa,Kim Seonghye,Kim Suhkmann,Park Jin Kyoon,Lee Nam-Sihk,Yoon Young Ho,Yang Haesik
Angewandte Chemie (International ed. in English)
Metal nanoparticle surfaces are used for peroxidase- and oxidase-like nanozymes but not for esterase-like nanozymes. It is challenging to obtain rapid catalytic hydrolysis on a metal surface and even more so without a catalytically labile substrate. Here, we report that metal nanoparticle surfaces rapidly catalyze non-redox ester hydrolysis in the presence of redox H N-BH (AB). Metal hydrides are readily generated on a Pt nanoparticle (PtNP) from AB, and as a result the PtNP becomes electron-rich, which might assist nucleophilic attack of H O on the carbonyl group of an ester. The nanozyme system based on PtNP, AB, and 4-aminonaphthalene-1-yl acetate provides an electrochemical signal-to-background ratio much higher than natural enzymes, due to the rapid ester hydrolysis and redox cycling involving the hydrolysis product. The nanozyme system is applied in a sensitive electrochemical immunosensor for thyroid-stimulating hormone detection. The calculated detection limit is approximately 0.3 pg mL , which indicates the high sensitivity of the immunosensor using the PtNP nanozyme.
Competitive Immunoassays for the Detection of Small Molecules Using Single Molecule Arrays.
Wang Xu,Cohen Limor,Wang Jun,Walt David R
Journal of the American Chemical Society
Small-molecule detection is important for many applications including clinical diagnostics, drug discovery, and measurements of environmental samples and agricultural products. Current techniques for small-molecule detection suffer from various limitations including low analytical sensitivity and complex sample processing. Furthermore, as a result of their small size, small molecules are difficult to detect using an antibody pair in a traditional sandwich assay format. To overcome these limitations, we developed an ultrasensitive competitive immunoassay for small-molecule detection using Single Molecule Arrays (Simoa). We show that the competitive Simoa assay is approximately 50-fold more sensitive than the conventional ELISA. We performed theoretical calculations to determine the factors that influence the sensitivity of competitive Simoa assays and used them to achieve maximal sensitivity. We also demonstrate detection of small molecules in complex biological samples. We show that the competitive Simoa assay is a simple, fast, and highly sensitive approach for ultrasensitive detection of small molecules.
Nanozymes: From New Concepts, Mechanisms, and Standards to Applications.
Liang Minmin,Yan Xiyun
Accounts of chemical research
Nanozymes are nanomaterials with intrinsic enzyme-like characteristics that have been booming over the past decade because of their capability to address the limitations of natural enzymes such as low stability, high cost, and difficult storage. Along with the rapid development and ever-deepening understanding of nanoscience and nanotechnology, nanozymes hold promise to serve as direct surrogates of traditional enzymes by mimicking and further engineering the active centers of natural enzymes. In 2007, we reported the first evidence that FeO nanoparticles (NPs) have intrinsic peroxidase-mimicking activity, and since that time, hundreds of nanomaterials have been found to mimic the catalytic activity of peroxidase, oxidase, catalase, haloperoxidase, glutathione peroxidase, uricase, methane monooxygenase, hydrolase, and superoxide dismutase. Uniquely, a broad variety of nanomaterials have been reported to simultaneously exhibit dual- or multienzyme mimetic activity. For example, FeO NPs show pH-dependent peroxidase-like and catalase-like activities; Prussian blue NPs simultaneously possess peroxidase-, catalase-, and superoxide dismutase-like activity; and MnO NPs mimic all three cellular antioxidant enzymes including superoxide dismutase, catalase, and glutathione peroxidase. Taking advantage of the physiochemical properties of nanomaterials, nanozymes have shown a broad range of applications from in vitro detection to replacing specific enzymes in living systems. With the emergence of the new concept of "nanozymology", nanozymes have now become an emerging new field connecting nanotechnology and biology. Since the landmark paper on nanozymes was published in 2007, we have extensively explored their catalytic mechanism, established the corresponding standards to quantitatively determine their catalytic activities, and opened up a broad range of applications from biological detection and environmental monitoring to disease diagnosis and biomedicine development. Here we mainly focus on our progress in the systematic design and construction of functionally specific nanozymes, the standardization of nanozyme research, and the exploration of their applications for replacing natural enzymes in living systems. We also show that, by combining the unique physicochemical properties and enzyme-like catalytic activities, nanozymes can offer a variety of multifunctional platforms with a broad of applications from in vitro detection to in vivo monitoring and therapy. For instance, targeting antibody-conjugated ferromagnetic nanozymes simultaneously provide three functions: target capture, magnetic separation, and nanozyme color development for target detection. We finally will address the prospect of nanozyme research to become "nanozymology". We expect that nanozymes with unique physicochemical properties and intrinsic enzyme-mimicking catalytic properties will attract broad interest in both fundamental research and practical applications and offer new opportunities for traditional enzymology.
Platinum Nanocatalyst Amplification: Redefining the Gold Standard for Lateral Flow Immunoassays with Ultrabroad Dynamic Range.
Loynachan Colleen N,Thomas Michael R,Gray Eleanor R,Richards Daniel A,Kim Jeongyun,Miller Benjamin S,Brookes Jennifer C,Agarwal Shweta,Chudasama Vijay,McKendry Rachel A,Stevens Molly M
Paper-based lateral flow immunoassays (LFIAs) are one of the most widely used point-of-care (PoC) devices; however, their application in early disease diagnostics is often limited due to insufficient sensitivity for the requisite sample sizes and the short time frames of PoC testing. To address this, we developed a serum-stable, nanoparticle catalyst-labeled LFIA with a sensitivity surpassing that of both current commercial and published sensitivities for paper-based detection of p24, one of the earliest and most conserved biomarkers of HIV. We report the synthesis and characterization of porous platinum core-shell nanocatalysts (PtNCs), which show high catalytic activity when exposed to complex human blood serum samples. We explored the application of antibody-functionalized PtNCs with strategically and orthogonally modified nanobodies with high affinity and specificity toward p24 and established the key larger nanoparticle size regimes needed for efficient amplification and performance in LFIA. Harnessing the catalytic amplification of PtNCs enabled naked-eye detection of p24 spiked into sera in the low femtomolar range (ca. 0.8 pg·mL) and the detection of acute-phase HIV in clinical human plasma samples in under 20 min. This provides a versatile absorbance-based and rapid LFIA with sensitivity capable of significantly reducing the HIV acute phase detection window. This diagnostic may be readily adapted for detection of other biomolecules as an ultrasensitive screening tool for infectious and noncommunicable diseases and can be capitalized upon in PoC settings for early disease detection.
Molecularly Imprinted Nanoparticles for Biomedical Applications.
Advanced materials (Deerfield Beach, Fla.)
Molecularly imprinted polymers (MIPs) are synthetic receptors with tailor-made recognition sites for target molecules. Their high affinity and selectivity, excellent stability, easy preparation, and low cost make them promising substitutes to biological receptors in many applications where molecular recognition is important. In particular, spherical MIP nanoparticles (or nanoMIPs) with diameters typically below 200 nm have drawn great attention because of their high surface-area-to-volume ratio, easy removal of templates, rapid binding kinetics, good dispersion and handling ability, undemanding functionalization and surface modification, and their high compatibility with various nanodevices and in vivo biomedical applications. Recent years have witnessed significant progress made in the preparation of advanced functional nanoMIPs, which has eventually led to the rapid expansion of the MIP applications from the traditional separation and catalysis fields to the burgeoning biomedical areas. Here, a comprehensive overview of key recent advances made in the preparation of nanoMIPs and their important biomedical applications (including immunoassays, drug delivery, bioimaging, and biomimetic nanomedicine) is presented. The pros and cons of each synthetic strategy for nanoMIPs and their biomedical applications are discussed and the present challenges and future perspectives of the biomedical applications of nanoMIPs are also highlighted.
A homogeneous split-luciferase assay for rapid and sensitive detection of anti-SARS CoV-2 antibodies.
Yao Zhong,Drecun Luka,Aboualizadeh Farzaneh,Kim Sun Jin,Li Zhijie,Wood Heidi,Valcourt Emelissa J,Manguiat Kathy,Plenderleith Simon,Yip Lily,Li Xinliu,Zhong Zoe,Yue Feng Yun,Closas Tatiana,Snider Jamie,Tomic Jelena,Drews Steven J,Drebot Michael A,McGeer Allison,Ostrowski Mario,Mubareka Samira,Rini James M,Owen Shawn,Stagljar Igor
Better diagnostic tools are needed to combat the ongoing COVID-19 pandemic. Here, to meet this urgent demand, we report a homogeneous immunoassay to detect IgG antibodies against SARS-CoV-2. This serological assay, called SATiN, is based on a tri-part Nanoluciferase (tNLuc) approach, in which the spike protein of SARS-CoV-2 and protein G, fused respectively to two different tNLuc tags, are used as antibody probes. Target engagement of the probes allows reconstitution of a functional luciferase in the presence of the third tNLuc component. The assay is performed directly in the liquid phase of patient sera and enables rapid, quantitative and low-cost detection. We show that SATiN has a similar sensitivity to ELISA, and its readouts are consistent with various neutralizing antibody assays. This proof-of-principle study suggests potential applications in diagnostics, as well as disease and vaccination management.
Surveilling and Tracking COVID-19 Patients Using a Portable Quantum Dot Smartphone Device.
Zhang Yuwei,Malekjahani Ayden,Udugama Buddhisha N,Kadhiresan Pranav,Chen Hongmin,Osborne Matthew,Franz Max,Kucera Mike,Plenderleith Simon,Yip Lily,Bader Gary D,Tran Vanessa,Gubbay Jonathan B,McGeer Allison,Mubareka Samira,Chan Warren C W
The ability to rapidly diagnose, track, and disseminate information for SARS-CoV-2 is critical to minimize its spread. Here, we engineered a portable smartphone-based quantum barcode serological assay device for real-time surveillance of patients infected with SARS-CoV-2. Our device achieved a clinical sensitivity of 90% and specificity of 100% for SARS-CoV-2, as compared to 34% and 100%, respectively, for lateral flow assays in a head-to-head comparison. The lateral flow assay misdiagnosed ∼2 out of 3 SARS-CoV-2 positive patients. Our quantum dot barcode device has ∼3 times greater clinical sensitivity because it is ∼140 times more analytically sensitive than lateral flow assays. Our device can diagnose SARS-CoV-2 at different sampling dates and infectious severity. We developed a databasing app to provide instantaneous results to inform patients, physicians, and public health agencies. This assay and device enable real-time surveillance of SARS-CoV-2 seroprevalence and potential immunity.
A one-step homogeneous immunoassay for cancer biomarker detection using gold nanoparticle probes coupled with dynamic light scattering.
Liu Xiong,Dai Qiu,Austin Lauren,Coutts Janelle,Knowles Genevieve,Zou Jianhua,Chen Hui,Huo Qun
Journal of the American Chemical Society
A one-step homogeneous immunoassay for the detection of a prostate cancer biomarker, free-PSA (prostate specific antigen), was developed using gold nanoparticle probes coupled with dynamic light scattering (DLS) measurements. A spherical gold nanoparticle with a core diameter around 37 nm and a gold nanorod with a dimension of 40 by 10 nm were first conjugated with two different primary anti-PSA antibodies and then used as optical probes for the immunoassay. In the presence of antigen f-PSA in solution, the nanoparticles and nanorods aggregate together into pairs and oligomers through the formation of a sandwich type antibody-antigen-antibody linkage. The relative ratio of nanoparticle-nanorod pairs and oligomers versus individual nanoparticles was quantitatively monitored by DLS measurement. A correlation can be established between this relative ratio and the amount of antigen in solution. The light scattering intensity of nanoparticles and nanoparticle oligomers is several orders of magnitude higher than proteins and other typical molecules, making it possible to detect nanoparticle probes in the low picomolar concentration range. f-PSA in the concentration range from 0.1 to 10 ng/mL was detected by this one-step and washing-free homogeneous immunoassay.
Ultrabright fluorescent nanoscale labels for the femtomolar detection of analytes with standard bioassays.
Luan Jingyi,Seth Anushree,Gupta Rohit,Wang Zheyu,Rathi Priya,Cao Sisi,Gholami Derami Hamed,Tang Rui,Xu Baogang,Achilefu Samuel,Morrissey Jeremiah J,Singamaneni Srikanth
Nature biomedical engineering
The detection and quantification of low-abundance molecular biomarkers in biological samples is challenging. Here, we show that a plasmonic nanoscale construct serving as an 'add-on' label for a broad range of bioassays improves their signal-to-noise ratio and dynamic range without altering their workflow and readout devices. The plasmonic construct consists of a bovine serum albumin scaffold with approximately 210 IRDye 800CW fluorophores (with a fluorescence intensity approximately 6,700-fold that of a single 800CW fluorophore), a polymer-coated gold nanorod acting as a plasmonic antenna and biotin as a high-affinity biorecognition element. Its emission wavelength can be tuned over the visible and near-infrared spectral regions by modifying its size, shape and composition. It improves the limit of detection in fluorescence-linked immunosorbent assays by up to 4,750-fold and is compatible with multiplexed bead-based immunoassays, immunomicroarrays, flow cytometry and immunocytochemistry methods, and it shortens overall assay times (to 20 min) and lowers sample volumes, as shown for the detection of a pro-inflammatory cytokine in mouse interstitial fluid and of urinary biomarkers in patient samples.
Long-range fluorescence quenching by gold nanoparticles in a sandwich immunoassay for cardiac troponin T.
Mayilo Sergiy,Kloster Meike A,Wunderlich Michael,Lutich Andrey,Klar Thomas A,Nichtl Alfons,Kürzinger Konrad,Stefani Fernando D,Feldmann Jochen
We report the first homogeneous sandwich immunoassay with gold nanoparticles (AuNPs) as fluorescence quenchers. The sandwich assay is designed for the detection of the protein cardiac troponin T (cTnT) by its simultaneous interaction with two different antibodies, one attached to AuNPs and the other labeled with fluorescent dyes. We demonstrate the working principle of the assay and using time-resolved fluorescence spectroscopy, we determine the quenching efficiency of the gold nanoparticles. In spite of the relatively large separation distance between dye molecules and AuNPs, ranging from 3 to 22 nm, the AuNPs quench the fluorescence with efficiencies as high as 95%. A limit of detection of 0.02 nM (0.7 ng/mL) was obtained for cTnT, which is the lowest value reported for a homogeneous sandwich assay for cTnT. These results illustrate the use of metallic nanoparticles as fluorescence quenchers in immunoassays where the large biomolecules involved impose distances for which energy transfer between fluorophores would be inefficient.
Ratiometric Fluorescent Lateral Flow Immunoassay for Point-of-Care Testing of Acute Myocardial Infarction.
Wang Jing,Jiang Chenxing,Jin Jiening,Huang Liang,Yu Wenbo,Su Bin,Hu Jun
Angewandte Chemie (International ed. in English)
We report the development of a highly sensitive ratiometric fluorescent lateral flow immunoassay (RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker, namely heart-type fatty acid binding protein (H-FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles. In conjunction with using custom smartphone-based analytical device and tonality analysis, quantitative detection of H-FABP was achieved with a low limit of detection at 0.21 ng mL . The RFLFIA strip can generate a visually distinguishable green-to-red color change around the threshold concentration of H-FABP (6.2 ng mL ), thus allowing the semi-quantitative diagnosis by the naked eye.
One-step homogeneous magnetic nanoparticle immunoassay for biomarker detection directly in blood plasma.
Ranzoni Andrea,Sabatte Gwenola,van Ijzendoorn Leo J,Prins Menno W J
Assay technologies capable of detecting low biomarker concentrations in complex biological samples are fundamental for biological research and for applications in medical diagnostics. In this paper we address the challenge to perform protein biomarker detection homogeneously in one single step, applying a minute amount of reagent directly into whole human blood plasma, avoiding any sample dilution, separation, amplification, or fluid manipulation steps. We describe a one-step homogeneous assay technology based on antibody-coated magnetic nanoparticles that are spiked in very small amount directly into blood plasma. Pulsed magnetic fields and a double-linker molecular architecture are used to generate high biomarker-induced binding and low nonspecific binding between the nanoparticles. We demonstrate dose-response curves for prostate specific antigen (PSA) measured in undiluted human blood plasma with a detection limit of 400-500 femtomol/L, in a total assay time of 14 min and an optically probed volume of only 1 nL. We explain the dose-response curves with a model based on discrete binding of biomarker molecules onto the nanoparticles, which allows us to extract reaction parameters for the binding of biomarker molecules onto the nanoparticles and for the biomarker-induced binding between nanoparticles. The demonstrated analytical performance and understanding of the nanoparticle assay technology render it of interest for a wide range of applications in quantitative biology and medical diagnostics.
A homogeneous chemiluminescent immunoassay method.
Akhavan-Tafti Hashem,Binger Dean G,Blackwood John J,Chen Ying,Creager Richard S,de Silva Renuka,Eickholt Robert A,Gaibor Jose E,Handley Richard S,Kapsner Kenneth P,Lopac Senja K,Mazelis Michael E,McLernon Terri L,Mendoza James D,Odegaard Bruce H,Reddy Sarada G,Salvati Michael,Schoenfelner Barry A,Shapir Nir,Shelly Katherine R,Todtleben Jeff C,Wang Guoping,Xie Wenhua
Journal of the American Chemical Society
A new homogeneous chemiluminescent immunoassay method featuring the use of specific binding members separately labeled with an acridan-based chemiluminescent compound and a peroxidase is reported. Formation of an immunocomplex brings the chemiluminescent compound and the peroxidase into close proximity. Without any separation steps, a chemiluminescent signal is generated upon addition of a trigger solution, and the intensity is directly correlated to the quantity of the analyte.
Single-step label-free nanowell immunoassay accurately quantifies serum stress hormones within minutes.
Mahmoodi S Reza,Xie Pengfei,Zachs Daniel P,Peterson Erik J,Graham Rachel S,Kaiser Claire R W,Lim Hubert H,Allen Mark G,Javanmard Mehdi
A non-faradaic label-free cortisol sensing platform is presented using a nanowell array design, in which the two probe electrodes are integrated within the nanowell structure. Rapid and low volume (≤5 μl) sensing was realized through functionalizing nanoscale volume wells with antibodies and monitoring the real-time binding events. A 28-well plate biochip was built on a glass substrate by sequential deposition, patterning, and etching steps to create a stack nanowell array sensor with an electrode gap of 40 nm. Sensor response for cortisol concentrations between 1 and 15 μg/dl in buffer solution was recorded, and a limit of detection of 0.5 μg/dl was achieved. Last, 65 human serum samples were collected to compare the response from human serum samples with results from the standard enzyme-linked immunosorbent assay (ELISA). These results confirm that nanowell array sensors could be a promising platform for point-of-care testing, where real-time, laboratory-quality diagnostic results are essential.
Quantitative Detection of Digoxin in Plasma Using Small-Molecule Immunoassay in a Recyclable Gravity-Driven Microfluidic Chip.
Li Hailong,Sørensen Jesper Vinther,Gothelf Kurt Vesterager
Advanced science (Weinheim, Baden-Wurttemberg, Germany)
Immunoassays are critical for clinical diagnostics and biomedical research. However, two major challenges remaining in conventional immunoassays are precise quantification and development of immunoassays for small-molecule detection. Here, a two signal-mode small-molecule immunoassay containing an internal reference that provides high stability and reproducibility compared to conventional small-molecule immunoassays is presented. A system is developed for quantitative monitoring of the digoxin concentration in plasma in the clinically relevant range (0.6-2.6 nm). Furthermore, the model system is integrated into a simple gravity-driven microfluidic chip (G-Chip) requiring only 10 µL plasma. The G-Chip allows fast detection without any complex operation and can be recycled for at least 50 times. The assay, and the G-Chip in particular, has the potential for further development of point-of-care (POC) diagnostics.
Quantum-dot-basedFörster resonance energy transfer immunoassay for sensitive clinical diagnostics of low-volume serum samples.
Wegner K David,Jin Zongwen,Lindén Stina,Jennings Travis L,Hildebrandt Niko
A myriad of quantum dot (QD) biosensor examples have emerged from the literature over the past decade, but despite their photophysical advantages, QDs have yet to find acceptance as standard fluorescent reagents in clinical diagnostics. Lack of reproducible, stable, and robust immunoassays using easily prepared QD-antibody conjugates has historically plagued this field, preventing researchers from advancing the deeper issues concerning assay sensitivity and clinically relevant detection limits on low-volume serum samples. Here we demonstrate a ratiometric multiplexable FRET immunoassay using Tb donors and QD acceptors, which overcomes all the aforementioned limitations toward application in clinical diagnostics. We demonstrate the determination of prostate specific antigen (PSA) in 50 μL serum samples with subnanomolar (1.6 ng/mL) detection limits using time-gated detection and two different QD colors. This concentration is well below the clinical cutoff value of PSA, which demonstrates the possibility of direct integration into real-life in vitro diagnostics. The application of IgG, F(ab')2, and F(ab) antibodies makes our homogeneous immunoassay highly flexible and ready-to-use for the sensitive and specific homogeneous detection of many different biomarkers.
Multiplexible Wash-Free Immunoassay Using Colloidal Assemblies of Magnetic and Photoluminescent Nanoparticles.
Kim Dokyoon,Kwon Hyek Jin,Shin Kwangsoo,Kim Jaehyup,Yoo Roh-Eul,Choi Seung Hong,Soh Min,Kang Taegyu,Han Sang Ihn,Hyeon Taeghwan
Colloidal assemblies of nanoparticles possess both the intrinsic and collective properties of their constituent nanoparticles, which are useful in applications where ordinary nanoparticles are not well suited. Here, we report an immunoassay technique based on colloidal nanoparticle assemblies made of iron oxide nanoparticles (magnetic substrate) and manganese-doped zinc sulfide (ZnS:Mn) nanoparticles (photoluminescent substrate), both of which are functionalized with antibodies to capture target proteins in a sandwich assay format. After magnetic isolation of the iron oxide nanoparticle assemblies and their bound ZnS:Mn nanoparticle assemblies (MZSNAs), photoluminescence of the remaining MZSNAs is measured for the protein quantification, eliminating the need for washing steps and signal amplification. Using human C-reactive protein as a model biomarker, we achieve a detection limit of as low as 0.7 pg/mL, which is more than 1 order of magnitude lower than that of enzyme-linked immunosorbent assay (9.1 pg/mL) performed using the same pair of antibodies, while using only one-tenth of the antibodies. We also confirm the potential for multiplex detection by using two different types of photoluminescent colloidal nanoparticle assemblies simultaneously.
Dye-Doped Silica Nanoparticles for Enhanced ECL-Based Immunoassay Analytical Performance.
Zanut Alessandra,Palomba Francesco,Rossi Scota Matilde,Rebeccani Sara,Marcaccio Massimo,Genovese Damiano,Rampazzo Enrico,Valenti Giovanni,Paolucci Francesco,Prodi Luca
Angewandte Chemie (International ed. in English)
The combination of highly sensitive techniques such as electrochemiluminescence (ECL) with nanotechnology sparked new analytical applications, in particular for immunoassay-based detection systems. In this context, nanomaterials, particularly dye-doped silica nanoparticles (DDSNPs) are of high interest, since they can offer several advantages in terms of sensitivity and performance. In this work we synthesized two sets of monodispersed and biotinylated [Ru(bpy) ] -doped silica nanoparticles, named bio-Triton@RuNP and bio-Igepal@RuNP, obtained following the reverse microemulsion method using two different types of nonionic surfactants. Controlling the synthetic procedures, we were able to obtain nanoparticles (NPs) offering highly intense signal, using tri-n-propylamine (TPrA) as coreactant, with bio-Triton@RuNps being more efficient than bio-Igepal@RuNP.
Potential-Resolved Multicolor Electrochemiluminescence for Multiplex Immunoassay in a Single Sample.
Guo Weiliang,Ding Hao,Gu Chaoyue,Liu Yanhuan,Jiang Xuecheng,Su Bin,Shao Yuanhua
Journal of the American Chemical Society
Electrochemiluminescence (ECL) is a highly successful technique used in commercial immunoassays for clinical diagnosis. Developing an ECL-based multiplex immunoassay, with the potential to enable high-throughput detection of multiple biomarkers simultaneously, remains a current research interest yet is limited by a narrow choice of ECL luminophores. Herein we report the synthesis, photophysics, electrochemistry, and ECL of several new ruthenium(II) and iridium(III) complexes, three of which are eventually used as signal reporters for multiplex immunoassay. The ECL behaviors of individual luminophores and their mixtures were investigated in multiple modes, including light intensity, spectrum, and image measurements. The spectral peak separation between Ru(bpy)(dvbpy) (bpy = 2,2'-bipyridine, dvbpy = 4,4'-bis(4-vinylphenyl)-2,2'-bipyridine), and Ir(dFCFppy)(dtbbpy) (dFCFppy = 3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl]phenyl, dtbbpy = 4,4'-bis( tert-butyl)-2,2'-bipyridine) was up to 145 nm, thus providing the spectrum-resolved possibility of identifying light signals. The potential-resolved ECL signals were achieved for the mixtures of Ir(ppy) (ppy = 2-phenylpyridine) with either Ru(bpy)(dvbpy) or Ir(dFCFppy)(dtbbpy), due to the self-annihilation ECL of Ir(ppy) at higher potentials, as confirmed by electrochemistry-coupled mass spectrometry. A multiplex immunoassay free of spatial spotting antibodies on plates or substrates was ultimately devised by combining luminophore-loaded polymer beads with the homogeneous sandwich immunoreaction. Using potential and spectrum dual-resolved ECL as the readout signal, simultaneous recognition of three antigens, namely, carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), and beta-human chorionic gonadotropin (β-HCG), was demonstrated in a single run for a sample volume of 300 μL. These results contribute to the understanding of ECL generation by multiple luminophores and devising spot-free multiplex immunoassays with less sample consumption.
Self-Luminescent Lanthanide Metal-Organic Frameworks as Signal Probes in Electrochemiluminescence Immunoassay.
Wang Yaoguang,Zhao Guanhui,Chi Hong,Yang Shenghong,Niu Qingfen,Wu Dan,Cao Wei,Li Tianduo,Ma Hongmin,Wei Qin
Journal of the American Chemical Society
The successful use of electrochemiluminescence (ECL) in immunoassay for clinical diagnosis requires development of novel ECL signal probes. Herein, we report lanthanide (Ln) metal-organic frameworks (LMOFs) as ECL signal emitters in the ECL immunoassay. The LMOFs were prepared from precursors containing Eu (III) ions and 5-boronoisophthalic acid (5-bop), which could be utilized to adjust optical properties. Investigations of ECL emission mechanisms revealed that 5-bop was excited with ultraviolet photons to generate a triplet-state, which then triggered Eu (III) ions for red emission. The electron-deficient boric acid decreased the energy-transfer efficiency from the triplet-state of 5-bop to Eu (III) ions; consequently, both were excited with high-efficiency at single excitation. In addition, by progressively tailoring the atomic ratios of Ni/Fe, NiFe composites (Ni/Fe 1:1) were synthesized with more available active sites, enhanced stability, and excellent conductivity. As a result, the self-luminescent europium LMOFs displayed excellent performance characteristics in an ECL immunoassay with a minimum detectable limit of 0.126 pg mL, using Cytokeratins21-1 (cyfra21-1) as the target detection model. The probability of false positive/false negative was reduced dramatically by using LMOFs as signal probes. This proposed strategy provides more possibilities for the application of lanthanide metals in analytical chemistry, especially in the detection of other disease markers.
Dual targeting luminescent gold nanoclusters for tumor imaging and deep tissue therapy.
Chen Dan,Li Bowen,Cai Songhua,Wang Peng,Peng Shuwen,Sheng Yuanzhi,He Yuanyuan,Gu Yueqing,Chen Haiyan
Dual targeting towards both extracellular and intracellular receptors specific to tumor is a significant approach for cancer diagnosis and therapy. In the present study, a novel nano-platform (AuNC-cRGD-Apt) with dual targeting function was initially established by conjugating gold nanocluster (AuNC) with cyclic RGD (cRGD) that is specific to αvβ3integrins over-expressed on the surface of tumor tissues and aptamer AS1411 (Apt) that is of high affinity to nucleolin over-expressed in the cytoplasm and nucleus of tumor cells. Then, AuNC-cRGD-Apt was further functionalized with near infrared (NIR) fluorescence dye (MPA), giving a NIR fluorescent dual-targeting probe AuNC-MPA-cRGD-Apt. AuNC-MPA-cRGD-Apt displays low cytotoxicity and favorable tumor-targeting capability at both in vitro and in vivo level, suggesting its clinical potential for tumor imaging. Additionally, Doxorubicin (DOX), a widely used clinical chemotherapeutic drug that kill cancer cells by intercalating DNA in cellular nucleus, was immobilized onto AuNC-cRGD-Apt forming a pro-drug, AuNC-DOX-cRGD-Apt. The enhanced tumor affinity, deep tumor penetration and improved anti-tumor activity of this pro-drug were demonstrated in different tumor cell lines, tumor spheroid and tumor-bearing mouse models. Results in this study suggest not only the prospect of non-toxic AuNC modified with two targeting ligands for tumor targeted imaging, but also confirm the promising future of dual targeting AuNC as a core for the design of prodrug in the field of cancer therapy.
Fabrication of BSA@AuNC-Based Nanostructures for Cell Fluoresce Imaging and Target Drug Delivery.
Ding Caifeng,Xu Yujuan,Zhao Yanan,Zhong Hua,Luo Xiliang
ACS applied materials & interfaces
Drug delivery which can offer efficient and localized drug transportation together with imaging capabilities is highly demanded in the development of cancer theranostic approaches. Herein, we report the construction of bovine serum albumin (BSA) gold nanoclusters (BSA@AuNCs) for cell fluoresce imaging and target drug delivery. BSA@AuNCs were modified with cyclic arginine-glycine-aspartate with the product RGD-BSA@AuNCs to enhance cell internalization of the nanoclusters. Furthermore, doxorubicin hydrochloride or doxorubicin (DOX), a widely used chemotherapy drug, was also used to modify RGD-BSA@AuNCs. The final design of the DOX/RGD-BSA@AuNC system was constructed through the disulfide bond. The physical microstructure and biological characterization of the BSA@AuNCs were realized through high-resolution transmission electron microscopy and confocal laser fluorescence microscopy. As the disulfide bonds were cleaved by glutathione in cancer cells, DOX-SH molecules were released from the nanosystem to inhibit the growth of cancer cells. The as-prepared DOX/RGD-BSA@AuNC system can be used not only to deliver drug but also to achieve the antitumor effect by in vivo imaging, demonstrating its promising applications in cancer treatment.
Core-Shell-Heterostructured Magnetic-Plasmonic Nanoassemblies with Highly Retained Magnetic-Plasmonic Activities for Ultrasensitive Bioanalysis in Complex Matrix.
Hao Liangwen,Leng Yuankui,Zeng Lifeng,Chen Xirui,Chen Jing,Duan Hong,Huang Xiaolin,Xiong Yonghua,Chen Xiaoyuan
Advanced science (Weinheim, Baden-Wurttemberg, Germany)
Herein, a facile self-assembly strategy for coassembling oleic acid-coated iron oxide nanoparticles (OC-IONPs) with oleylamine-coated gold nanoparticles (OA-AuNPs) to form colloidal magnetic-plasmonic nanoassemblies (MPNAs) is reported. The resultant MPNAs exhibit a typical core-shell heterostructure comprising aggregated OA-AuNPs as a plasmonic core surrounded by an assembled magnetic shell of OC-IONPs. Owing to the high loading of OA-AuNPs and reasonable spatial distribution of OC-IONPs, the resultant MPNAs exhibit highly retained magnetic-plasmonic activities simultaneously. Using the intrinsic dual functionality of MPNAs as a magnetic separator and a plasmonic signal transducer, it is demonstrated that the assembled MPNAs can achieve the simultaneous magnetic manipulation and optical detection on the lateral flow immunoassay platform after surface functionalization with recognition molecules. In conclusion, the core-shell-heterostructured MPNAs can serve as a nanoanalytical platform for the separation and concentration of target compounds from complex biological samples using magnetic properties and simultaneous optical sensing using plasmonic properties.