Impedimetric biosensors based on biorecognition agents immobilized onto conducting polymer electrodes

Conducting polymer electrodes were fabricated by chemical deposition of polypyrrole onto microporous polycarbonate membranes. The optimized polymer electrodes were characterized using a combination of cyclic voltammetry, AC impedance spectroscopy and scanning electron microscopy. Reagentless immuno-sensors (for E. coli O157 and Salmonella) were fabricated by immobilization of antibodies or antibody fragments onto the surface of polypyrrole electrodes. The impedance of the film changed in response to antigen binding although the sensitivity was low (5 log cfu/ml). Non-specific binding was also a problem at high cell densities. Bacteriophage sensors were fabricated by immobilizing host cells on the surface of the polymer electrode. Upon addition of bacteriophage the impedance of the film increased due to the lytic activity of the phages. Under optimized conditions it was possible to detect 3 log pfu/ml within 4.5 h. The study has provided a basis for fabricating low cost biosensors suitable for on-site testing in food industry using conducting polymer electrodes.