Direct Electrochemistry of Glucose Oxidase at a Gold Electrode Modified with Graphene Nanosheets

Abstract

In this work, we report the direct electrochemistry of glucose oxidase (GOD) observed at a gold electrode modified with graphene nanosheets. Initially, graphene nanosheets were synthesized and conjugated to the enzyme GOD and immobilized on to a gold electrode surface. Cyclic voltammetry was then performed using Gold-Graphene-GOD modified electrodes in a pH 7.2 phosphate buffered saline (PBS). A pair of well-defined redox peaks was obtained for GOD with the reduction peak centered at +180 mV and a peak separation of 70 mV in PBS under physiological conditions. Moreover, the electron transfer rate of GOD redox reaction was greatly enhanced and the peak potential was found to be pH dependent at the graphene-GOD surface. Further, the performance of the Gold-Graphene-GOD was found to be stable and excellent under physiological conditions indicating the possibility of employing this platform for real time analysis. The observed results indicated that the 2D-graphene holds great promise for conjugation ability with a variety of enzymes. Further, our results also confirmed that graphene is capable of holding the enzyme GOD in a favorable position and retains its original structure and functionality that are essential for biosensing.