Electronic polymers in aqueous media may offer bioelectronic detection of biospecific interactions. Here we report a fluorometric DNA hybridization detection method based on non-covalent coupling of DNA to a water-soluble zwitterionic polythiophene derivative. Introduction of a single-stranded oligonucleotide will induce a planar polymer and aggregation of the polymer chains, detected as a decrease of the intensity and a red-shift of the fluorescence. On addition of a complementary oligonucleotide, the intensity of the emitted light is increased and blue-shifted. The detection limit of this method is at present approximately 10(-11) moles. The method is highly sequence specific, and a single-nucleotide mismatch can be detected within five minutes without using any denaturation steps. The interaction with DNA and the optical phenomena persists when the polymer is deposited and patterned on a surface. This offers a novel way to create DNA chips without using covalent attachment of the receptor or labelling of the analyte.