Ferrocene Entrapped In Polypyrrole Film and PAMAM Dendrimers as Matrix for Mediated Glucose/O2 Biofuel Cell

We fabricated bioanodes based on PAMAM (polyamidoamine) dendrimers to immobilize glucose oxidase (GOx), using ferrocenium hexafluorophosphate (Fc) entrapped in electropolymerized polypyrrole films (Fc-polypyrrole) as mediator. We conducted a comparative study of the GOx kinetic parameters as a function of the enzyme environment; i.e., in solution and immobilized onto carbon platforms. Kinetic studies revealed that the Michaelis-Menten constants (K-M) of the anchored and soluble GOx were quite similar, K-M = 21.2 (+/- 0.6) mmol L-1 in solution, and 21.5 (+/- 0.8) mmol L-1 when immobilized, demonstrating that enzyme immobilization did not affect the enzyme-substrate affinity. However, the maximum reaction rate (V-max) obtained for the immobilized GOx (V-max = 0.72 (+/- 0.03) mu mol min(-1) mg(-1)) was lower than the reaction rate achieved for the free enzyme in solution (V-max= 64 (+/- 2) mu mol min(-1) mg(-1)), due to diffusional effects. Cyclic voltammetry assays confirmed the incorporation of entrapped Fc species into the polypyrrole net films. The performance of the prepared bioelectrodes in a glucose/O-2 semi-cell revealed a maximum power density around 130 (+/- 15) mu W cm(-2) at pH 5.0, in 100 mmol L-1 glucose. Considering all the electrochemical data and biofuel cell tests, we can infer that the bioanode based on Fc and polypyrrole presented here, is easy to prepare, and the electrocatalyst film efficiently transfers electrons between GOx and the electrode surface. Therefore, it has potential application in glucose/O-2 biofuel cells. (C) 2014 Elsevier Ltd. All rights reserved.