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 electr ocatalytic 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 b iosensors using enzyme-immobilised membranes were constructed for the deter mination of formic acid and glucose-6-phosphate (G6P), respectively. The fo rmic acid biosensor based on the combination of formate dehydrogenase (FDH) -modified membrane with 3,4-DHB-coated glassy carbon electrode is one to tw o orders more sensitive (LOD, 5.0 x 10(-5) M) than previously reported elec trochemical biosensors. Similarly, lower detection limit (4.0 x 10(-5) M) f or the measurement of G6P was achieved using glucose-6-phosphate dehydrogen ase (G6PDH) in the presence of beta -NADP(+). The interference of uric acid and ascorbate was minimised by incorporating an additional membrane modifi ed with uricase and ascorbate oxidase, respectively. The biosensing scheme developed in this study can be adopted universally with a number of dehydro genases for the detection of different substrates. (C) 2001 Elsevier Scienc e S.A. All rights reserved.