Reticulated Vitreous Carbon-Based Composite Enzyme Electrodes as Suitable Biosensors in Both Aqueous and Predominantly Nonaqueous Media

Abstract

The construction and performance of reticulated vitreous carbon (RVC)-based composite enzyme electrodes in different aqueous and predominantly nonaqueous working media is reported. Both the mediator (ferrocene or ferrocyanide) and the enzyme peroxidase were immobilized by direct adsorption on chemically pretreated RVC cylinders. Pores of RVC were filled up with epoxy resin. The working media considered were: an aqueous phosphate solution of pH 7.4, a predominantly nonaqueous medium constituted by acetonitrile:Tris buffer (pH 7.4) mixtures, and organized media such as micellar solutions and oil-in-water emulsions. Hydrogen peroxide and 2-butanone peroxide were used as the substrates. The composite biosensors showed a good stability in all these media. Polishing of the electrode surface everyday before working was necessary, the useful lifetime of each single electrode being of approximately 20 days. Furthermore, reproducible responses were obtained with different electrodes constructed in the same manner. Kinetic parameters Vm, Km,app and k′cat were calculated in all cases, as well as the analytical characteristics from the corresponding calibration plots. The detection limits obtained with the RVC-epoxy resin composite enzyme electrodes are, in general, considerably better than those found in the literature for bioelectrodes constructed with epoxy resin as the binder. Finally, this composite electrode also performed well in the flow injection mode.