Electrochemical oxidation of NADH at highly boron-doped diamond electrodes

Conductive boron-doped chemical vapor-deposited diamond thin films, already known to have superior properties for general electroanalysis, including l ow background current and a wide potential window, are here shown to have a dditional advantages with respect to electrochemical oxidation of nicotinam ide adenine dinucleotide (NADH), including high resistance to deactivation and insensitivity to dissolved oxygen, Cyclic voltammetry, amperometry, and the rotating disk electrode technique were used to study the reaction in n eutral pH solution. Highly reproducible cyclic voltammograms for NADH oxida tion were obtained at as-deposited diamond electrodes. The response was sta ble over several months of storage in ambient air, in contrast to glassy ca rbon electrodes, which deactivated within 1 h, The diamond electrode exhibi ted very high sensitivity for NADH, with an amperometric detection limit of 10 nM (S/N = 7), The response remained stable, even in the very low concen tration range, for several months. In addition, interference effects due to ascorbic acid were minimal when the concentrations of NADH and ascorbic ac id were comparable. An NADH-mediated dehydrogenese-based ethanol biosensor incorporating an unmodified diamond electrode is demonstrated. The present results indicate that diamond is a useful electrode material for the analyt ical detection of NADH, making it attractive for use in sensors based on en zyme-catalyzed reactions involving NADH as a cofactor.