Electrochemical Oxidation of Cysteine at a Film Gold Modified Carbon Fiber Microelectrode Its Application in a Flow—Through Voltammetric Sensor

A flow-electrolytical cell containing a strand of micro Au modified carbon fiber electrodes (CFE) has been designedand characterized for use in a voltammatric detector for detecting cysteine using high-performance liquid chromatography. Cysteine is more efficiently electrochemical oxidized on a Au /CFE than a bare gold and carbon fiber electrode. The possible reaction mechanism of the oxidation process is described from the relations to scan rate, peak potentials and currents. For the pulse mode, and measurements with suitable experimental parameters, a linear concentration from 0.5 to 5.0 mg·L−1 was found. The limit of quantification for cysteine was below 60 ng·mL−1

Electrochemical cysteine determination in serum samples by Hg thin film sensor

PubMed ID: 21229462Cysteine is a nonessential aminoacid, meaning that cysteine can be made in the human body. It is one of the few amino acids that contain sulfur. This allows cysteine to bond in a special way and maintain the structures of proteins in the body. Cysteine strengthens the protective lining of the stomach and intestines, which may help prevent damage caused by aspirin and similar drugs. In addition, cysteine may play an important role in the communication between immune system cells. In this study, glassy carbon electrodes modified with mercury (Hg) were used as working electrode. Mercury thin film on glassy carbon electrode was deposited by holding the electrode potential at -0.7V; the measurement period for the coating process was 2 minutes. pH and temperature effects on the electrode response were carried out by working at different pHs and temperatures. The calibration graph for cysteine was drawn in the range of 5-120µM cysteine. Repeatability and interferences studies were investigated. GSH had an interference effect of about 13% of cysteine response. Finally, the sensor was applied to real samples for cysteine determination and the method was validated by Ellman's reagent. Copyright © Taylor & Francis Group, LLC

Glutathione (GSH) Determination by a Very Simple Electrochemical Method

WOS: 000293235700002Glutathione (GSH; gamma-glutamylcysteinylglycine) is ubiquitous in mammalian and other living cells. It contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side chain. It has several important functions, including protection against oxidative stress. It is synthesized from its constituent amino acids by the consecutive actions of gamma-glutamylcysteine synthetase and GSH synthetase. Cellular levels of GSH may be increased by supplying substrates and GSH delivery compounds. Increasing cellular GSH may be therapeutically useful. In this study, we investigated the applicability of the glassy carbon electrode coated with thin Hg film layer to the determination of reduced glutathione (GSH). For this purpose, firstly, Hg coating process parameters were studied such as concentration of mercury coating solution, coating current, coating temperature. Then, working conditions were investigated. At the end of these studies, we concluded that although some of limitations, the sensor would be applicable to the determination of reduced glutathione

A High Sensitive, Reproducible and Disposable Immunosensor for Analysis of SOX2

Tarimeri, Nur/0000-0002-7464-9107WOS: 000508461600001In this study, an ITO (indium tin oxide) based biosensor was constructed to detect SOX2. SOX2 helps the regulation of cell pluripotency and is closely related to early embryonic development, neural and sexual differentiation. SOX2 is amplified and overexpressed in some malignant tumors such as squamous cell, lung, prostate, breast, esophageal cell, colon, ovarian, glioblastoma, pancreatic cancer, gastric cancer, head and neck squamous cell carcinoma. To generate a hydroxylated clean electrode surface, ITO electrodes were treated with NH4OH/H2O2/H2O. Later, ITO-PET electrode surfaces were modified with 3-glycidoxypropyl trimethoxysilane (3-GOPS). Then, Anti-SOX2 was covalently immobilized onto the electrode surfaces. 3-GOPS concentration, Anti-SOX2 concentration and incubation time, SOX2 incubation time were optimized. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized in order to follow up the immobilization processes and the optimization steps of the biosensor. To characterize the analytical properties of constructed immunosensor; linear range, repeatability, reproducibility and regeneration studies were investigated. the linear range of the immunosensor was detected as 0.625 pg/mL-62.5 pg/mL. Square wave voltammetry technique was also applied to the biosensor. Storage life of the biosensor was determined for identifying the possible usability of the biosensor in clinical field. Finally, the designed biosensor was applied to the real human serum samples. the results obtained with the presented biosensor were also compared with ELISA results.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)Acknowledgments that help the COBILTUM for SEM and EDX experiments. This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK)

A biosensor based on catalase for determination of highly toxic chemical azide in fruit juices

WOS: 000232818500019PubMed ID: 16202884In this work, an amperometric biosensor based on catalase enzyme was developed for the determination of azide. The principle of the measurements was based on the determination of the decrease in the differentiation of oxygen level which had been caused by the inhibition of catalase in the bioactive layer of the biosensor by azide. Firstly, the optimum conditions for the inhibitor biosensor were established. In the optimization studies of the biosensor, the most suitable catalase and gelatin amounts and glutaraldehyde ratio were determined. Optimum catalase activity, optimum gelatin amount and glutaraldehyde percentage were 5000 U cm(-2), 5.94 mg cm(-2) and 2.5% respectively. Characterization studies of the biosensor such as optimum pH and optimum temperature were carried out. The repeatability experiments were done and the average value (x), standard deviation (S.D.) and variation coefficient (C.V.) were calculated as 98.6 mu M, +/- 4.16 mu M and 4.23%, respectively. A good linear relationship with a correlation coefficient of 0.9902 was obtained over the concentration range of 25 mu M to 300 mu M azide. After the optimization and characterization studies the proposed biosensor was applied to the determination of azide in certain fruit juices. (c) 2005 Elsevier B.V. All rights reserved

A biosensor based on urate oxidase-peroxidase coupled enzyme system for uric acid determination in urine

WOS: 000186127200001PubMed ID: 18969164A new amperometric biosensor based on urate oxidase-peroxidase coupled enzyme system for the specific and selective determination of uric acid in urine was developed. Commercially available urate oxidase and peroxidase were immobilized with gelatin by using glutaraldehyde and fixed on a pretreated teflon membrane. The method is based on generation of H2O2 from urine uric acid by urate oxidase and its consuming by peroxidase and then measurement of the decreasing of dissolved oxygen concentration by the biosensor. The biosensor response depends linearly on uric acid concentration between 0.1 and 0.5 muM. In the optimization studies of the biosensor, phosphate buffer (pH 7.5; 50 mM) and 35 degreesC were obtained as the optimum working conditions. In addition, the most suitable enzyme activities were found as 64.9 x 10(-3) U cm(-2) for urate oxidase and 512.7 U cm(-2) for peroxidase. And also some characteristic studies of the biosensor such as reproducibility, substrate specificity and storage stability were carried out. (C) 2003 Elsevier Science B.V. All rights reserved