Abstract: A nucleic acid hybridization detection assay is carried out at a solid electrode. A solid electrode, such as an indium tin oxide electrode, is modified by single-stranded capture oligonucleotides that are immobilized to the surface of the electrode. Using sandwich assay methodology, complementary target nucleic acid sequences hybridize to the capture oligonucleotides, which are in turn hybridized to a detection probe comprising a nanoparticle. When the assay is carried out in the presence of a redox mediator in solution, the nanoparticle catalyzes the transfer of electrons to the electrode, thus generating a detectable electrical current.