Electroreduction of NAD(+) to enzymatically active NADH at poly(neutral red) modified electrodes

The electropolymerisation of neutral red (NR) led to formation of a redox active film on the electrode surface. At negative potentials a current of NAD(+) reduction was observed at poly(NR) modified electrodes. To identify the product of NAD(+) reduction the alcoholdehydrogenase (ADH) containing Nafion(R) membrane was put onto the poly(NR) modified electrode surface. In the presence of a small portion of NAD(+) (0.1-0.2 mM) the resulting enzyme electrode exhibited a response to addition of acetaldehyde. The cathodic current density was dependent on NAD(+) concentration and was more than IO times higher than that of the acetaldehyde background reduction on a bare poly(NR) modified electrode. Thus, the main product of NAD(+) electroreduction at the poly(NR) modified electrode was the enzymatically active NADH.