The synthesis of a new functionalized terthiophene monomer with an unsaturated side chain, 3-((2':2 '',5 '':2'''-terthiophene)-3 ''-yl) acrylic acid, is described. A conducting polymer was obtained by electropolymerization of the functionalized monomer. The properties of the polymer were investigated using FT-IR, Raman and UV-vis spectroscopy. The application of the polymer as an active substrate for a genosensor is demonstrated by the covalent attachment of amino-end modified oligonucleotide probes to the carboxylic acid group of the polymer. The hybridization of the complementary ODNs can be clearly detected by an increase in the admittance without the need for an indicator or any sample modifications. (C) 2007 Elsevier Ltd. All rights reserved.