Direct electrochemistry of glucose oxidase based on one step electrodeposition of reduced graphene oxide incorporating polymerized L-lysine and its application in glucose sensing

The direct electron transfer and enzyme catalytic activity were investigated in electrochemical biosensor based on glucose oxidase (GOx) and electrochemical reduced graphene oxide-poly-(L-lysine) (ERGO-PLL) hybrid composite film embedded in a biocompatible matrix of Nafion. The ERGO-PLL was fabricated onto glassy carbon electrode (GCE) through one step electrodeposition of RGO incorporating PLL from graphene oxide-L-lysine aqueous dispersion. The fabrication process of Nafion/GOx/ERGO-PLL/GCE has been characterized by cyclic voltammetry and electrochemical impedance spectroscopy, and the surface morphology of modified electrodes were characterized by scanning electron microscopy. A pair of well-defined redox peaks with formal potential and peak separation of −0.461 V and 30 mV were observed at scan rate of 50 mV s⁻¹, the electron transfer rate constant was calculated to be 18.7 s⁻¹, demonstrated that direct electron transfer between immobilized GOx with ERGO-PLL and GCE was achieved. Moreover, the fabricated enzyme biosensor exhibited excellent electrocatalytic activity for determination of glucose in O₂-free PBS (7.40) with linear voltammetric response from 0.005 to 9.0 mmol L⁻¹, and detection limits (S/N = 3) of 2.0 μmol L⁻¹. This work indicates that ERGO-PLL based modified electrode is superior to that of graphene based, and could be applied in biosensors, bioelectronics and electrocatalysis, etc.