Voltammetric biosensors for the determination of formate and glucose-6-phosphate based on the measurement of dehydrogenase-generated NADH and NADPH.

This paper describes the development of a modified electrode for the electrocatalytic oxidation of beta-nicotinamide adenine dinucleotide (beta-NADH) and beta-nicotinamide adenine dinucleotide phosphate (beta-NADPH) using electropolymerised 3,4-dihydroxybenzaldehyde (3,4-DHB). Two voltammetric biosensors using enzyme-immobilised membranes were constructed for the determination of formic acid and glucose-6-phosphate (G6P), respectively. The formic acid biosensor based on the combination of formate dehydrogenase (FDH)-modified membrane with 3,4-DHB-coated glassy carbon electrode is one to two orders more sensitive (LOD, 5.0x10(-5) M) than previously reported electrochemical biosensors. Similarly, lower detection limit (4.0x10(-5) M) for the measurement of G6P was achieved using glucose-6-phosphate dehydrogenase (G6PDH) in the presence of beta-NADP(+). The interference of uric acid and ascorbate was minimised by incorporating an additional membrane modified with uricase and ascorbate oxidase, respectively. The biosensing scheme developed in this study can be adopted universally with a number of dehydrogenases for the detection of different substrates.