Electrochemical characterization of directly immobilized glucose oxidase on gold mercaptosuccinic anhydride self-assembled monolayer

A new method is developed, for direct coupling of enzymes on gold thiol self-assembled monolayers, based on glucose oxidase as a model enzyme and gold mercaptosuccinic anhydride self-assembled monolayer as a platform. The immobilization method is simple and fast, and enzyme is immobilized very close to the gold electrode surface. Preparation steps and the biosensor response to glucose are monitored by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and chronoamperometry. The relative differences between the slopes and intercepts of the current and conventional methods, using EDC/NHS activators for immobilization, are 10 and 8% for five-time measurements of each calibration curve obtained by chronoamperometry. The EIS data are approximated based on appropriate electronic equivalent circuit models and charge transfer resistances (Rct) are extracted from which a wide range linear calibration curve is obtained using 1/Rct versus glucose concentration. In addition, the analytical method is improved based on the EIS abilities allowing decreasing data acquisition time by a factor of 15.