Electrochemical biosensor based on reduced graphene oxide modified electrode with Prussian blue and poly(toluidine blue O) coating

Prussian blue (PB) has shown strong catalytic property for the reduction of hydrogen peroxide, but the application in biosensor fabrication is limited for its instability at neutral pH. In this work, an amperometric biosensor was fabricated based on glassy carbon electrode modified with reduced graphene oxide (RGO), PB and poly(toluidine blue O) (PTBO). The modified electrodes were characterized by scanning electron microscopy and UV-Visible absorption spectroscopy. Cyclic voltammetry and amperometric measurements were employed to investigate the electrochemical property of the modified electrodes. Experimental results showed that the GC/RGO/PB/PTBO modified electrode offered the best electrocatalytic activity toward the reduction of hydrogen peroxide when compared with electrodes modified with RGO-PB, RGO/PTBO and RGO materials, indicating the possible synergistic effects of the PB-PTBO composite material. The electrode showed high sensitivity and good stability for the analysis of hydrogen peroxide in phosphate buffer solution (pH 7.4). After codeposition of glucose oxidase (GOD) and chitosan (CHIT) coating, the resulting GC/RGO/PB/PTBO/CHIT-GOD electrode exhibited excellent response to glucose with a sensitivity of 59 mA M^-1 cm^-2, a low detection limit of 8.4 μM and a linear range from 20 μM to 1.09 mM at a detection potential of +0.2 V vs. AgAgCl reference.