Glukoz oksidaz bazlı enzim elektrotlarda elektriksel iletkenliğin geliştirilmesi

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Thesis Type: Postgraduate

Institution Of The Thesis: Hacettepe Üniversitesi, Fen Bilimleri Enstitüsü, Biyomühendislik A.B.D., Turkey

Approval Date: 2010

Thesis Language: Turkish

Student: GONCA BİLGE

Principal Supervisor (For Co-Supervisor Theses): SELMA MUTLU

Open Archive Collection: AVESIS Open Access Collection

Abstract:

This study aims to develop electrical conductivity of glucose oxidase based (GOD) enzyme electrode for biosensors and biofuel cells applications which has become more important.For this purpose, the design of glucose oxidase based enzyme electrode which is based on development of electrical conductivity between the redox active center of enzyme and the electrode prepared by different enzyme immobilization techniques has been proposed.In the scope of thesis, the design studies of GOD enzyme electrode including covalent bounding, electrochemical immobilization and reconstitution of apo-enzyme techniques have been presented. The enzyme electrodes prepared by different immobilization techniques were compared with each other.To increase the electron transfer between the redox center of enzyme and electrode, in the covalent bounding and electrochemical immobilization techniques the mediator molecules, in the reconstitution of apo-enzyme technique direct electron transfer were used.Polipyrrole (PPy) as conductive polymer and dimethyl aminomethyl ferrocene (DMAMFc) as mediator were used in the covalent bounding and electrochemical immobilization techniques. Polyaniline as conductive polymer was used in the reconstitution of apo-enzyme technique. For increasing the efficiency of immobilization, some parameters of immobilization were studied. Immobilization parameters of reconstitution of apo-enzyme technique couldn?t be studied due to stabilization problem of this technique.The effects of environmental factors such as pH and temperature on enzyme based electrodes were investigated by chronoamperometry (CA) technique in electrochemical potantiostat-galvanostat system. Calibration curves of enzyme electrodes were plotted and the kinetic parameters (Km, Imax) were calculated. For the enzyme electrode prepared by electrochemical immobilization, Km is 7 mM and Imax is 833 µA. For the prepared enzyme electrode by covalent bounding, Km is 19.87 mM, Imax is 1250 µA. For the third one, theenzyme electrode prepared by the reconstitution of apo-enzyme, Km is 27.4 mM, Imax is 2000 µA.Prepared enzyme electrodes by covalent bounding and electrochemical immobilization techniques were tested on a biofuel cell. The performance of the biofuel cell was discussed from its current-potential characteristics. According to this result, biofuel cell consist of prepared bioanode by covalent bounding open circuit potential (OCP) is 333 mV, short circuit current density was 18.17 µA/cm2 (under 0.85 ? resistance) and maximum power density was 0.9 µW/cm2. Biofuel cell consist of prepared bioanode by electrochemical immobilization open circuit potential (OCP) is 456 mV, short circuit current density was 13.30 µA/cm2 (under 0.85 ? resistance) and maximum power density was 0.88 µW/cm2.Finally, the surfaces of prepared enzyme electrodes by different immobilization techniques were characterized as topografhical and chemical by AFM and FTIR.With this study the performances of enzyme electrodes which prepared by different immobilization techniques on biofuel cells and biosensors were presented.