Fabrication of Potentiometric Enzymatic Glucose Biosensor Based on Graphene and Magnetic Beads

In this paper, ruthenium dioxide (RuO2) electrodes were fabricated by radio frequency (r.f.) sputtering and screen-printed technique, and RuO2 sensing films could be as pH sensor to measure different pH solutions. The average sensitivity and linearity of pH sensor were 51.847 mV/pH and 0.987, respectively. A glucose biosensor could be prepared through casting glucose oxidase (GOx) on RuO2 electrode, so the flexible arrayed glucose biosensors modified by magnetic beads (MB) and graphene (GR) were developed in this study. In preparation processes, graphene solution was first cast on the RuO2, then we introduced carbodiimide hydrochloride (EDC) to connect glucose oxidase (GOx) and magnetic bead by covalent bond. Finally, magnetic beads-GOx-nafion composite was dropped on RuO2 to complete preparation of the RuO2/Graphene/Magnetic Bead-GOx-Nafion glucose biosensor. The electrochemical impedance spectra (EIS) was used to investigate the capability of electron transfer of the different electrodes, and it was found that the additions of magnetic beads and graphene which had excellent electric conductivity could decrease the electron transfer resistance (Rct) from the experiment results. Besides, EIS could also be used to demonstrate whether the glucose biosensors had already been completely modified by magnetic beads and graphene through the different resistances of the biosensors. Furthermore, the glucose biosensor modified by magnetic beads and graphene had superior performance, the average sensitivity and linearity of RuO2/Graphene/Magnetic Bead-GOx-Nafion glucose biosensor were 10.628 mV/mM and 0.998, respectively. After 28 days, RuO2/Graphene/Magnetic Bead-GOx-Nafion glucose biosensor still had relative sensitivity of 82.2 %.