An electrochemical glucose biosensor based on graphene composites: use of dopamine as reducing monomer and as site for covalent immobilization of enzyme

A new graphene-based electrochemical biosensor was constructed and applied for the simple, rapid and highly selective determination of glucose. The modified glassy carbon electrode (GCE) was prepared using dopamine (DA) as a reducing agent for graphene oxide (GO) and as a capping agent to stabilize and coat the resulting reduced graphene oxide (RGO) surface as it can polymerize to form polydopamine (PDA). PDA-RGO composites were dropped onto a glassy carbon electrode surface, and glucose oxidase (GOx) was immobilized on the surface of the composites by Michael addition. Finally, Pt nanoparticles (PtNPs) were electrodeposited on the modified electrode. Such modified electrodes (denoted as GCE/PDA-RGO/GOx/PtNPs) were characterized by UV-visible spectroscopy, atomic force microscopy, X-ray power diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Electrochemical behaviors were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The fabricated biosensor exhibited a high sensitivity of 33 mu A mM(-1) cm(-2) over a wide linear range of 0.2 mM to 1 mM, good stability, excellent repeatability, and a detection limit of 0.10 mM.