Yazar "Mikoliunaite, Lina" seçeneğine göre listele

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    1,10-Phenanthroline-5,6-dione and 9,10-phenanthrenequinone as redox mediators for amperometric glucose biosensors
    (SPRINGER, 2014) Zor, Erhan; Oztekin, Yasemin; Mikoliunaite, Lina; Voronovic, Jaroslav; Ramanaviciene, Almira; Anusevicius, Zilvinas; Bingol, Haluk
    In this study, two ortho-quinoidal compounds, 1,10-phenanthroline-5,6-dione (PD) and 9,10-phenanthrenequinone (PQ), were examined as electron transfer mediators suitable for amperometric glucose biosensors. The dependences of the electrochemical responses of PD- and PQ-based amperometric glucose biosensors on varied concentrations of glucose were investigated under aerobic and anaerobic conditions. The PD-modified graphite rod (GR) electrode revealed a current response seven times higher than that of the PQ-modified GR electrode. The reactivity indices of ortho-quinoidals assessed by means of B3LYP functional method applying 6-311G(D) basis set showed that the electron-accepting potency for PD was markedly higher as compared with that of PQ. Compared to PQ, considerably higher reactivity of PD has been defined in the reactions with NADP(+)-ferredoxin reductase (FNR, EC 1.18.1.2) as a model single-electron transfer FAD-dependent enzyme, which provided an additional evidence for PD as a more efficient mediator compared to PQ. This study illustrates that PD can be applied as a redox mediator for glucose oxidase and it could be more suitable for a reagent-less biosensor design than PQ.
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    Copper nanoparticle modified carbon electrode for determination of dopamine
    (PERGAMON-ELSEVIER SCIENCE LTD, 2012) Oztekin, Yasemin; Tok, Mutahire; Bilici, Esra; Mikoliunaite, Lina; Yazicigil, Zafer; Ramanaviciene, Almira; Ramanavicius, Arunas
    This paper reports the synthesis and characterization of copper nanoparticles (CuNPs) and application of copper nanoparticle-modified glassy carbon electrode for the electrochemical determination of dopamine. Electrochemical measurements were performed using differently modified glassy carbon (GC) electrodes. Bare, oxidized before modification and copper nanoparticle-modified glassy carbon electrodes (bare-GC, ox-GC and CuNP/GC electrodes, respectively) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of redox probes. Atomic force microscopy was used for the visualization of electrode surfaces. The CuNP/GC electrode was found to be suitable for the selective determination of dopamine even in the presence of ascorbic acid, uric acid, and p-acetamidophenol. The observed linear range of CuNP/GC for dopamine was from 0.1 nM to 1.0 mu M while the detection limit was estimated to be 50 pM. It was demonstrated that here reported glassy carbon electrode modified by copper nanoparticles is suitable for the determination of dopamine in real samples such as human blood serum. (C) 2012 Elsevier Ltd. All rights reserved.
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    Electrochemical stability and repulsion of polypyrrole film
    (ELSEVIER SCIENCE BV, 2013) Ratautaite, Vilma; Ramanaviciene, Almira; Oztekin, Yasemin; Voronovic, Jaroslav; Balevicius, Zigmas; Mikoliunaite, Lina; Ramanavicius, Arunas
    This study reports the electrochemical synthesis of polypyrrole (Ppy) film on the gold surface and the evaluation of this film repulsion conditions from the electrode surface. It is known that overall stability of the conducting polymer layer on the electrode is critical for many applications including biosensors. It can be affected by many factors however electrochemical treatment of electrode is mostly well-known among them. This work was mainly based on the preparation of the polymeric layer and the investigation of its stability. Overoxidised polypyrrole film was synthesized on the gold electrode. Later this layer was treated by potential cycling in wide potential intervals. The stability of Ppy layers deposited on electrode was evaluated. It was determined that Ppy layer was stable within 0-0.9 V potential range, scan rate was 20 mV/s, vs. Ag/AgCl/KClsat. while it was repulsed from the gold electrode by 10 potential cycles within 0.0-1.0 V potential range at the same scan rate. Some possible future applications of repulsed Ppy films are predicted. (C) 2012 Elsevier B.V. All rights reserved.
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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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    Molecularly Imprinted Polypyrrole for DNA Determination
    (WILEY-V C H VERLAG GMBH, 2013) Ratautaite, Vilma; Topkaya, Seda Nur; Mikoliunaite, Lina; Ozsoz, Mehmet; Oztekin, Yasemin; Ramanaviciene, Almira; Ramanavicius, Arunas
    In this study graphite electrodes modified by a thin DNA-imprinted polypyrrole layer, which was able to bind specific target-DNA, are reported. For this aim, electrochemical synthesis of polypyrrole was performed on a pencil graphite electrode by cyclic voltammetry (CV) or by potential pulse sequences (PPS). The modified electrode surface was used for electrochemical determination of target-DNA by differential pulse voltammetry. According to our best knowledge this is a first report on the application of DNA-imprinted polymer for the determination of target-DNA. The results showed that the molecularly imprinted polypyrrole (MIPPy) layer that formed on the carbon electrode surface was sensitive for target-DNA, while the nonimprinted polypyrrole layer was not sensitive to the same target-DNA. Comparison of electrodes modified using PPS and CV techniques is presented.