New micro/nanocomposite with peroxidase-like activity in construction of oxidases-based amperometric biosensors for ethanol and glucose analysis.

Development of artificial enzymes, including nanozymes as an alternative for non-stable and expensive natural enzymes, is a booming field of modern Biosensorics and Biofuel Technology. In this study, we describe fabrication and characterization of sensitive biosensors for the detection of ethanol and glucose based on new micro/nanocomposite electrodes with peroxidase-like activity (nanozyme) coupled with microbial oxidases: alcohol oxidase (AOX) and glucose oxidase (GOX). The nanozyme was synthesized by modification of carbon microfibers (CF) by hemin (H) and gold (Au) nanoparticles. The formation of gold nanoparticles on the surface of hemin-modified carbon microfibers has been confirmed by the UV-Vis and X-ray spectroscopy as well by the SEM analysis. Compared to hemin-only modified electrodes, the resulting micro/nanocomposite CF-H-Au electrodes exhibit a higher specific catalytic activity and a better affinity for HO in solution. The HO-sensitive CF-H-Au-modified electrodes showed a higher sensitivity (1.3-2.6-fold) compared with the nearest carbon-derived analogs and were used for the construction of highly sensitive ethanol and glucose biosensors. To eliminate diffusion limitation for substrates, AOX or GOX were fixed on the CF-H-Au-modified electrodes using a highly porous Nafion membrane. The main biosensors' characteristics have been investigated. The developed biosensors were tested for ethanol and glucose analysis in the real samples of both grape must and wine. The results are in good agreement with the results obtained using enzymatic kits as reference approaches.