Immobilization of glucose oxidase on gold nanoparticles modified Au electrode for the construction of biosensor

Abstract

A novel method to fabricate glucose biosensor was developed by immobilizing glucose oxidase (GOx) on gold nanoparticles, which had self-assembled on Au electrode modified with thiol-containing three-dimensional network of silica gel. The assembly process was followed and confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which indicated that the gold nanoparticles in the biosensing interface efficiently improved the electron transfer between analyte and electrode surface. The immobilized enzyme on the electrode surface exhibits excellent catalytic activities for the oxidation of glucose when soluble redox mediator ferrocenemethanol was present. The coverage of electrically wired active GOx (${\Gamma }_{\text{E}}^0$) at the enzyme electrode surface was evaluated high to be 4.5 × 10⁻¹² mol cm⁻² on the basis of kinetic models reported in literature. Moreover, this sensor exhibited fast amperometric response (3 s) to the mediated electrocatalyzed oxidation of glucose, and the catalytic current is proportional to the concentration of glucose up to 6 mM with a high sensitivity of 8.3 μA mM⁻¹ cm⁻². The detection limit of the sensor was estimated to be 23 μM. In addition, the sensor has good reproducibility, and can remain stable over 60 days.