Enhanced Electron Transfer in Enzymatic Bioelectrodes by a Poly(vinyl alcohol) N-Methyl-4(4′-formylstyryl) Pyridinium Methosulfate Acetal Cationic Polymer

A novel method for enzyme immobilization has been developed for use in enzymatic biofuel cell cathodes and anodes. Enzyme immobilization was achieved on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWNTs) using the freestanding cationic polymer poly(vinyl alcohol) N-methyl-4(4-formylstyryl) pyridiniummethosulfateacetal (PVA-SbQ). The enzymes entrapped within the polymer chains possess the ability to exchange electrons with the electrode through their respective substrates. The enzyme catalysts studied for biofuel cell cathodes were tyrosinase and laccase, and for biofuel cell anodes alcohol dehydrogenase (ADH) and glucose oxidase (GOx). The advantage of using PVA-SbQ for enzyme immobilization was demonstrated by using cyclic voltammetry. The experimental results showed that the freestanding PVA-SbQ polymer chains retained a higher enzyme activity on the MWNT-modified electrodes compared to cross-linked PVA-SbQ chains. Electrochemical impedance spectroscopy was applied to understand the electron-transfer resistance of cross-linked PVA-SbQ. The experimental results also show that enzyme/PVA-SbQ/MWNT electrodes generate a higher current compared to control electrodes without MWNTs or the polymer. We conclude that the PVA-SbQ polymer enhances both enzyme immobilization and electrochemical charge transfer in enzyme bioelectrodes, showing promise for the development of high-performance biofuel cells.