Fast Fourier transformation electrochemical impedance spectroscopy for the investigation of inactivation of glucose biosensor based on graphite electrode modified by Prussian blue, polypyrrole and glucose oxidase

Abstract

In this study we report the application of fast Fourier transformation electrochemical impedance spectroscopy (FFT-EIS) for the evaluation of bioselective layer of amperometric glucose biosensor created by the entrapment of the enzyme glucose oxidase (GOx) within composite polypyrrole (Ppy) and Prussian blue (PB) based layer. Additionally, chronoamperometry and atomic force microscopy (AFM) were applied for the characterization of graphite electrodes (GE) modified with bioselective layer of PB/Ppy/GOx. AFM investigations reveal that the variation of pyrrole concentration in the range of 10–30mM did not show significant differences in the surface roughness because calculated root mean square (RMS) was in the range of 15–19nm. In another set of experiments, which were based on FFT-EIS, only a small variation in charge transfer resistance was observed before and after application of GE/PB/Ppy/GOx electrodes for amperometric determination of glucose concentration. These findings preliminary suggest that those electrochemical properties of GE/PB/Ppy/GOx electrode, which could be detected by FFT-EIS method, do not vary significantly during the use of this electrode in the detection of glucose. However, the amperometric signals of the GE/PB/Ppy/GOx electrodes decrease during the measurements due to the mixed-type of GOx inhibition, as it was determined by the evaluation of cathodic currents vs glucose concentrations. These evaluations of amperometric response kinetics let us suggest that the decrease of biosensor signal is based on mixed-type (uncompetitive and non-competitive) inhibition of GOx.