Novel conducting polymers for DNA sensing

Novel functionalized pyrroles, 3-pyrrolylacrylic acid (PAA), 5-(3-pyrrolyl) 2,4-pentadienoic acid (PPDA), and 3-pyrrolylpentanoic acid (PPA) were synthesized and used to construct label-free gene sensors based on pyrrole copolymer films. Electrochemical impedance spectroscopy (EIS) was used to obtain electrical readout from these gene sensors. Comparison of the performance of PPDA-containing sensors to that containing 3-pyrrolylpentanoic acid (PPA), a similar functionalized pyrrole but with a saturated side chain, showed that functionalized polymers with unsaturated side chains have superior properties for use in biosensor applications. Sensors based on copolymers of both PAA and PPDA were evaluated across a wide range of oligonucleotide concentrations. The highest sensitivity was exhibited by a poly(Py-co-PPDA) sensor whose EIS spectra were well resolved, and the changes in charge-transfer resistance, taken as the index of sensor response, were largest among the materials studied. This sensor had a detection limit of 0.5 nM and a good selectivity.