Comparative study of electron mediators used in the electrochemical oxidation of NADH

A comparison of the behavior of six different redox mediators for the electrocatalysis of the oxidation of NADH, which are widely used in the construction of dehydrogenase-based biosensors, is reported. The redox mediators were, potassium hexacyanoferrate (II), Meldola's Blue (MB), dichlorophenolindophenol (DCPIP), p-benzoquinone (p-BQ), o-phenylenediamine (o-PDA) and 3,4-dihydroxybenzaldehyde (3,4-DHB). After incorporating each of them in the sensor system following four different strategies (in solution, entrapped in epoxy-composites, adsorbed or electropolymerized on the electrode surface), several aspects regarding repeatability and reproducibility were considered and compared.