New scheme for electrochemical detection of DNA based on electrocatalytic oxidation of NADH

A new electrocatalytic scheme for the detection of DNA is described. This scheme relies on the different interactions of single- and double-stranded oligonucleotides with the organic dyes methylene blue, thionin, azure A, azure B, toluidine blue O, brilliant cresyl blue and neutral red, which in addition can act as NADH catalysts. This catalytic activity can be used for amplifying differentiation between duplex and single-stranded DNA. Pyrolytic graphite electrodes modified with adsorbed dsDNA–organic dye complexes gave higher electrocatalytic NADH oxidation currents than those measured with electrodes modified with adsorbed ssDNA–organic dye. This difference is maximum for brilliant cresyl blue. These results suggest that the proposed scheme may be useful for the detection of DNA hybridisation and damage. Keywords: DNA hybridisation, Catalytic NADH oxidation, Phenoxazines, Phenothiazines, Phenazines