Electrochemical Glucose Sensing Using an Electrochemically Reduced Graphene Oxide/Poly-L-Lysine Composite Electrode Modified with Glucose Oxidase

Facilitating efficient electrical communication between glucose oxidase (GOx) and electrode surfaces is important for the development of low-potential reagent-free glucose biosensors, yet unequivocal direct electron transfer (DET) for native GOx remains controversial because the FAD redox center is deeply buried within the protein structure. In this work, a one-step electrochemical co-deposition strategy was used to fabricate an electrochemically reduced graphene oxide/L-lysine (ERGO–Lys) nanocomposite on glassy carbon. The resulting interface exhibited a pair of well-defined redox peaks centered at −0.460 V (vs Ag/AgCl) and glucose-responsive behavior under rigorously deoxygenated conditions. Given the continuing debate surrounding native GOx DET at carbon nanomaterials, these results are interpreted conservatively as DET-like (pseudo-DET) bioelectrochemistry rather than definitive proof of true DET. Under anaerobic conditions, the biosensor showed a linear range of 5 μM to 9.0 mM, a sensitivity of 35.8 μA·mM⁻¹·cm⁻², and a limit of detection of 1.8 μM. The sensor also retained 90% of its initial response after two weeks and showed low interference at −0.40 V.