Abstract: The present disclosure provides methods and compositions for conducting an assay to detect a polynucleotide. In particular, ruthenium complexes having reduction potentials that do not coincide with the reduction potential of molecular oxygen are disclosed and amperometric techniques for their use are described. In preferred embodiments, the ruthenium complex is ruthenium (III) pentaamine pyridine and the polynucleotide that is detected is DNA. Further, techniques for enhancing detectable contrast between hybridized and unhybridized nucleic acids are disclosed. In particular, the use of elongated target strands as well as the use of uncharged probe strands are discussed.

Abstract: Methods for conducting an assay to detect nucleic acid hybridization are disclosed. In particular, the fabrication of a carbon electrode suited to nucleic acid hybridization detection is described. In some preferred embodiments, a micro array of carbon electrodes is constructed using photolithography. The final step in the photolithography process involves developing a solder mask with an alkaline solution. The alkaline solution oxidizes the carbon surface producing surface carboxylic acid groups. The surface carboxylic acid groups are reacted with EDC or DCC and NHS to produce NHS esters. Immobilization of NeutrAvidin™ onto the electrode surface is effected by reaction with the surface NHS ester groups. A biotinylated probe DNA molecule is then attached to the electrode via binding between the biotin group and the immobilized NeutrAvidin™. The resulting electrode can be used to detect hybridization between the probe DNA and complementary target DNA.

Abstract: The present disclosure relates to methods of detecting nucleic acid hybridization by monitoring an output signal. Some advantageous embodiments include techniques which can augment the signal. One such technique involves catalytic detection, such as with a peroxidase or other enzyme. Another technique involves “on-chip” amplification to enlarge the nucleic acid after hybridization has occurred.