Modified electrodes for NADH oxidation and dehydrogenase-based biosensors

The direct electrochemical oxidation of β-nicotinamide adenine dinucleotide (NADH) at clean electrodes proceeds through a radical cation intermediate at high overpotentials and is subject to rapid fouling. Consequently, there has been a considerable body of work over the last 20 years looking at ways in which to catalyse the reaction using a wide variety of different types of modified electrode. These studies have resulted in a good knowledge of the essential features required for efficient catalysis. In designing modified electrodes for NADH oxidation, it is not only important to identify suitable redox groups, which can catalyse NADH oxidation and can be attached to the electrode surface; it is also important to ensure facile charge transport between the immobilised redox sites in order to ensure that, in multilayer systems, the whole of the redox film contributes to the catalytic oxidation. One way to achieve this is by the use of electronically conducting polymers such as poly(aniline).