Polymers Based on Sulfonated Polyanillines for Direct Electron Transfer with (PQQ)GDH and Application in Carbon Nanostructure-Based Biofuel Cells
6 polymers have been prepared from different mixtures of sulfoxy-, methoxy- and carboxy-substituted aniline by chemical synthesis and characterized by UV/VIS, IR and NMR spectroscopy. The substitution pattern influences the reactivity of the different polymers with the enzyme in solution, however when fixed on electrode surfaces the potential can be effectively used to enforce the reaction .
One of the polymers (poly(3-aminobenzoic acid-co-2-methoxyaniline-5-sulfonic acid) has been applied in modifying carbon nanotube based electrode structures and coupling (PQQ)GDH for construction of a bioanode. The first fuel cell uses MWCNT-based bucky paper as electrode material. The PQQ-GDH has been covalently coupled to the polymer. The glucose oxidation of this electrode achieves a current density of 700μA/cm2. As cathode PQQ modified bucky paper with covalently bound BOD (bilirubin oxidase) is applied. For this electrode a start potential of about 0.5V vs. Ag/AgCl and a maximum current density of 1mA/cm2 can be observed. The biofuel cell resulting from the bucky paper electrodes shows current densities up to about 100μW/cm2 in a 10mM glucose solution.
In a second approach vertically aligned carbon nanotubes (vaCNT) have been used for the electrode construction. Both enzymes have been immobilized in a similar way as compared to bucky paper. The vaCNT-based fuel cell achieves a maximum power density of 125µW/cm2. Even after three days and several runs of load a power density of more than 110µW/cm2 is retained (quiescent solution, 10mM glucose, room temperature). Furthermore it can be shown that this biofuel cell operates in human serum samples.
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