Low-overpotential and highly sensitive detection of NADH with electrochemically pretreated cup-stacked carbon nanofiber electrodes

Cup-stacked carbon nanofibers (CSCNFs), the surface of which provides highly ordered graphene edges and electroactive oxygen-containing functional groups, were investigated as electrode materials for oxidation of β-Nicotinamide adenine dinucleotide (NADH) at low overpotential. The NADH oxidation was facilitated at the CSCNF-modified glassy carbon (CSCNF/GC) electrode, the surface of which was electrochemically activated at -0.40 V (vs. Ag|AgCl) to generate electrochemically reduced electroactive oxygen-containing functional groups. The anodic peak current of NADH oxidation was observed at about + 0.065 V by cyclic voltammetry measurements. The obtained value was negatively shifted by ~ 0.33 and ~ 0.63 V compared with the CSCNF/GC electrode without the electrochemical reductive pretreatment and the GC electrode, respectively. In addition, NADH-dependent glucose dehydrogenase (GDH) molecule-modified CSCNF/GC electrodes enabled the detection of glucose at the low overpotential effectively in the presence of NAD⁺, which accepts electrons from GDH and then reduces to NADH, after the electrochemical reductive pretreatment. Thus, the electrochemical reductive pretreatment of CSCNF electrodes would be useful for the development of highly sensitive NADH-dependent enzymatic biosensors.