A simple water-soluble pyrene-functionalized cationic polyelectrolyte poly(4- vinylpyridine) quaternary ammonium (P4VP-Py-Bu) was designed and synthesized from poly(4-vinylpyridine) by two-step quaternization with 1-(bromomethyl)pyrene and 1-bromobutane. The polymer could be bound with a single-stranded DNA (ssDNA) by electrostatic interactions and hydrophobic interactions to form a fluorescent complex probe for the detection of DNA hybridization. When the complementary ssDNA was added into the complex probe solution to form DNA duplex, the fluorescence emission intensity decreased more greatly compared with that by the addition of non-complementary ssDNA. It is inferred that the pyrene moieties of P4VP-Py-Bu could be intercalated into DNA duplex base-pairs, thus the fluorescence quenching by nucleotide bases was strengthened. Both the circular dichroism spectra and the fluorescence quenching induced by iodide confirmed this supposed intercalation. (c) 2013 Elsevier Ltd. All rights reserved.