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    Enzymatic polymerization of polythiophene by immobilized glucose oxidase
    (ELSEVIER SCI LTD, 2014) Krikstolaityte, Vida; Kuliesius, Jurgis; Ramanaviciene, Almira; Mikoliunaite, Lina; Kausaite-Minkstimiene, Asta; Oztekin, Yasemin; Ramanavicius, Arunas
    In this study 'green', environmentally friendly enzymatic reaction-based synthesis of conducting polymer polythiophene (PTP) is proposed. Glucose oxidase (GO(x)) was shown as an effective catalyst, which, in the presence of glucose, produces hydrogen peroxide suitable for the oxidative polymerization of PTP under ambient conditions at neutral pH. Enzymatically induced formation of the PTP layer over GO(x)-modified graphite rod electrode (GRE) was demonstrated and evaluated amperometrically and by attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy. Surface morphology of GO(x)- and PTP-modified GR electrodes was characterized by atomic force microscopy. It was clearly shown that the apparent kinetic Michaelis constant (K-M(app.)) of GO(x)/PTP-modified GRE increased by increasing the duration of polymerization reaction. Therefore, enzymatic polymerization could be applied in adjustment and/or tuning of K-M(app.) and other kinetic parameters of GO(x)-based electrodes used in biosensor design. (C) 2014 Elsevier Ltd. All rights reserved.
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    Evaluation of Some Redox Mediators in the Design of Reagentless Amperometric Glucose Biosensor
    (WILEY-V C H VERLAG GMBH, 2014) Kausaite-Minkstimiene, Asta; Mazeiko, Viktor; Ramanaviciene, Almira; Oztekin, Yasemin; Solak, Ali Osman; Ramanavicius, Arunas
    The influence of redox mediators (tetrathiafulvalene (TTF), tetrathiafulvalene-tetracyanoquinodimethane complex (TTF-TCNQ), phenazine methosulfate (PMS), 5,6-diamino-1,10-phenonthroline (5,6-DAP), potassium ferrocyanide (K4[Fe(CN)6]), methylene blue (MB) and toluidine blue (TB)) on the response of amperometric glucose biosensor was investigated in this research. Graphite rod electrode (GRE) modified by adsorbed mediator and glucose oxidase (GOx) cross-linked with glutaraldehyde was served as working electrode. The highest amperometric signals were observed by using TTF and TTF-TCNQ as mediators. The impact of amount of immobilized GOx, an optimal pH region for operation, stability and reproducibility of the analytic signal of designed biosensor using these mediators were investigated and discussed.
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    Visualization of red-ox proteins on the gold surface using enzymatic polypyrrole formation
    (SPRINGER WIEN, 2011) Ramanaviciene, Almira; Kausaite-Minkstimiene, Asta; Oztekin, Yasemin; Carac, Geta; Voronovic, Jaroslav; German, Natalija; Ramanavicius, Arunas
    We describe a new method for the visualization of the activity of red-ox proteins on a gold interface. Glucose oxidase was selected as a model system. Surfaces were modified by adhesion of glucose oxidase on (a) electrochemically cleaned gold; (b) gold films modified with gold nanoparticles, (c) a gold surface modified with self-assembled monolayer, and (d) covalent immobilization of protein on the gold surface modified with a self-assembled monolayer. The simple optical method for the visualization of enzyme on the surfaces is based on the enzymatic formation of polypyrrole. The activity of the enzyme was quantified via enzymatic formation of polypyrrole, which was detected and investigated by quartz microbalance and amperometric techniques. The experimental data suggest that the enzymatic formation of the polymer may serve as a method to indicate the adhesion of active redox enzyme on such surfaces.