A Mediator‐Free Tyrosinase Biosensor Based on ZnO Sol‐Gel Matrix

Abstract

Abstract A tyrosinase biosensor was developed based on the immobilization of tyrosinase in a positively charged ZnO sol‐gel matrix on a glass carbon electrode. It has been found that the ZnO sol‐gel matrix provided an advantageous microenvironment in terms of its favorable isoelectric point for tyrosinase loading and the immobilized tyrosinase retained its activity to a large extent. Phenolic compounds were determined by the direct reduction of biocatalytically generated quinone species at −200 mV (vs. SCE) without any mediator. The parameters of the fabrication process and the various experimental variables for the enzyme electrode were optimized. The resulting biosensor can reach 95% of steady‐state current within15 s and sensitivity as high as 168 μA mmol L −1 . The linear range for phenol determination was from 1.5×10 −7 to 4.0×10 −5 mol L −1 with a detection limit of 8.0×10 −8 mol L −1 . The biosensor response retained 75% of the initial response after two weeks. The performance of the developed biosensor was compared with that of biosensors based on other sol‐gel matrices.