Covalent attachment of glucose oxidase to an Au electrode modified with gold nanoparticles for use as glucose biosensor

A feasible method to fabricate glucose biosensor was developed by covalent attachment of glucose oxidase (GOx) to a gold nanoparticle monolayer modified Au electrode. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of ferrocyanide followed and confirmed the assemble process of biosensor, and indicated that the gold nanoparticles in the biosensing interface efficiently improved the electron transfer between analyte and electrode surface. CV performed in the presence of excess glucose and artificial redox mediator, ferrocenemethanol, allowed to quantify the surface concentration of electrically wired enzyme (ΓE0) on the basis of kinetic models reported in literature. The ΓE0 on proposed electrode was high to 4.1×10−12 mol·cm−2, which was more than four times of that on electrode direct immobilization of enzyme by cystamine without intermediate layer of gold nanoparticles and 2.4 times of a saturated monolayer of GOx on electrode surface. The analytical performance of this biosensor was investigated by amperometry. The sensor provided a linear response to glucose over the concentration range of 2.0×10−5-5.7×10−3 M with a sensitivity of 8.8 μA·mM−1·cm−2 and a detection limit of 8.2 μM. The apparent Michaelis-Menten constant (Kmapp) for the sensor was found to be 4.3 mM. In addition, the sensor has good reproducibility, and can remain stable over 30 days.