Electrochemical method to measure dna attachment to an electrode surface in the presence of molecular oxygen

The present disclosure provides methods and compositions for conducting an assay to detect nucleic acid hybridization in the presence of oxygen. In particular, ruthenium complexes having a reduction potential that does not coincide with the reduction potential of molecular oxygen are disclosed and amperometric techniques for their use are described. In preferred embodiment s, the ruthenium complex is ruthenium (III) pentaamine pyridine and the nucleic acid hybridization event that is detected is DNA hybridization. Further, techniques for enhancing detectable contrast between hybridized and unhybridized nucleic acids are disclosed. In particular, the use of elongate d target strands as well as the use of uncharged probe strands are discussed.< /SDOAB>