Near-infrared and naked-eye fluorescence probe for direct and highly selective detection of cysteine and its application in living cells. Zhang Jianjian,Wang Jianxi,Liu Jiting,Ning Lulu,Zhu Xinyue,Yu Bianfei,Liu Xiaoyan,Yao Xiaojun,Zhang Haixia Analytical chemistry The near-infrared (NIR) fluorescence sensor for rapid, selective, and sensitive detection of cystenine (Cys) is of great importance in both biological and environmental sciences. Herein, we report a specific probe with turn-on fluorescence property, visible color change with naked-eye, and large wavelength shift on UV spectra for highly selective detection of Cys over homocysteine (Hcy) and glutathione (GSH) in both HEPES buffer (10 mM, pH 7.4) and diluted human serum. The probe based on the conjugate addition-cyclization reaction has a low limit of detection to Cys (0.16 μM as NIR fluorescence sensor and 0.13 μM as UV sensor). Kinetic study indicated that the probe has a very rapid response to Cys, owing to the much higher pseudo-first-order reaction constant with Cys (299 M(-1) s(-1)) than with Hcy (1.29 M(-1) s(-1)) or GSH (0.53 M(-1) s(-1)). Upon addition of Cys to a solution of the probe, the color changed from purple to cyan, with the maximum wavelength shifting from 582 to 674 nm in the UV spectrum and a fluorescence emission at 697 nm appearing. It has been successfully applied for determination of Cys in diluted serum and bioimaging of Cys in living cells with low cell toxicity. 10.1021/acs.analchem.5b00377

Microfluidic paper-based fluorescence sensor for L-homocysteine using a molecularly imprinted polymer and in situ-formed fluorescent quantum dots. Talanta Microfluidic paper-based analytical devices modified with molecularly imprinted polymers (μPADs@MIPs) were developed for fluorescent detection of targeted thiols via in situ UV-induced formation of quantum dots (μPADs@MIPs@QDs). The selectivity enhancement by the MIP layer formed on the filter paper surface was demonstrated for the isolation of L-homocysteine from wine. Followed by the addition of metal precursors solution (Zn/Cd/Cu) and UV irradiation, fluorescent quantum dots were formed thus enabling quantitative detection of the thiol (serving as a QD capping agent). The effect of different semiconductors was investigated to achieve a lower band gap and higher fluorescence intensity. Increasing fluorescence intensity in the presence of thiol groups was obtained for the following precursors mixture composition: ZnCdCu/S > ZnCd/S > ZnCu/S > ZnS. The proposed method has a good relationship between the fluorescence intensity of ZnCdCu/S QDs and L-homocysteine in a linear range from 0.74 to 7.40 μM with a limit of detection (LOD) and quantification (LOQ) of 0.51 and 1.71 μM respectively. This method was applied for the determination of L-homocysteine in white wine with RSD under 6.37%. 10.1016/j.talanta.2022.124185

A coumarin-based dual optical probe for homocysteine with rapid response time, high sensitivity and selectivity. Wang Kun-Peng,Xu Shengnan,Lei Yang,Zheng Wen-Jun,Zhang Qi,Chen Shaojin,Hu Hai-Yu,Hu Zhi-Qiang Talanta In this study, a new coumarin-based fluorescent and chromogenic dual channel probe (DC) was used for the selective detection of homocysteine (Hcy) over other amino acids, especially for cysteine (Cys) and glutathione (GSH). When Hcy is present in the solution, the remarkable fluorescence enhancement and obvious blue shift in UV-vis spectra can be observed. In addition, the color change from purple to yellow can be observed clearly by unaided eyes. This probe DC has fast response time, excellent sensitivity and selectivity to Hcy. A linear relationship exists between the ratio of emissions at 486 and 625 nm, and Hcy can be detected in a wide concentration range (0-200 μM). The signal-to-background ratio of fluorescence at 486 nm can reach 8.4, and the detection limit is calculated to be 3.5 µM. The response mechanism is proved to be the Michael addition reaction by Hcy. Preliminary results on cell imaging enable the practical application of Hcy tracing in living cells. 10.1016/j.talanta.2018.12.060

Synthesis and Characterization of 1-Imidazole-4,5-dicarboxylic Acid-Functionalized Silver Nanoparticles: Dual Colorimetric Sensors of Zn and Homocysteine. ACS omega A colorimetric assay has been developed for Zn and homocysteine (Hcy) detection using functionalized silver nanoparticles (AgNPs). AgNPs have been synthesized using silver nitrate, where sodium citrate is used as a stabilizing agent and NaBH as a reducing agent. Then, the nanoparticles (citrate@AgNPs) were functionalized with 1-imidazole-4,5-dicarboxylic acid (IDCA). UV-visible and FTIR spectra suggested that IDCA was functionalized on the surface of citrate@AgNPs through the N atom of the imidazole ring. The IDCA-functionalized silver nanoparticles (IDCA@AgNPs) simultaneously detected Zn and Hcy from aqueous solution and showed different responses to the two analytes (Zn and Hcy) based on the aggregation-induced color change of IDCA@AgNPs. They showed the color change from yellow to red, which was easily discriminated by visual inspection as well as UV-visible spectroscopy. The surface plasmon resonance absorbance values of Zn and Hcy are 485 and 512 nm, respectively, when Zn and Hcy react with IDCA@AgNPs. IDCA@AgNPs showed linearity with Zn and Hcy concentrations, with the detection limit of 2.38 μM and 0.54 nM, respectively (S/N = 3). The IDCA@AgNPs showed excellent selectivity toward Zn and Hcy compared to the different metal ions and amino acids, respectively. Optimal detection was achieved toward Zn and Hcy in the pH range 3-10. In addition, IDCA@AgNPs were used to detect Zn and Hcy from lake water, showing low interference. 10.1021/acsomega.2c04165