Polymer modified electrodes for the reversible oxidation-reduction of NAD+/NADH for use within amperometric...

Electrochemical enzyme based biosensors continue to attract much attention due to the simplified analyses they promise, in comparison to many more complicated analytical procedures. The largest group of enzymes, are those that rely NAD(P)+/NAD(P)H as cofactors. One of the problems associated with the use NAD(P)+/NAD(P)H redox couples, however, within electrochemical biosensors is their ability to passivate noble metal electrodes. There have been many attempts to overcome this problem, such as the use of carbon paste electrodes [1], although approaches such as these are both cumbersome and typically irreproducible. In recent years conducting polymers such as poly(3-methylthiophene) [2] have also been used to modify noble metal electrode surfaces to lower the overpotentials required, while poly(phenol red) has been incorporated into films to offer selectivity against interferents [3,4]. In this study platinum electrodes have been electrochemically coated with mixed polymer films of poly(phenol red) together with poly(3-methylthiophene), poly(aniline) or poly(o-phenylenediamine) to offer enhanced performance. Cyclic voltammetry has been used to compare the electrochemical behaviour of the NAD+/NADH redox couple over repeated potential cycles, with the most favourable results being seen with the poly(aniline)/poly(phenol red) and poly(o-phenylenediamine)/poly(phenol red) coated electrodes.