Potentiometric biosensors based on polyaniline semiconductor films

Application of polyaniline (PAn) semiconductor films for potentiometric biosensor development provides certain advantages compared with the known systems. For enzyme immobilisation a pH sensitive matrix was used, which could improve sensor sensitivity. Indeed the limiting response value of the PAn based trypsin electrode in 1 mM buffer was 270 mV. The maximal slope of the calibration curve in semilogarithmic coordinates was 180 mV per substrate decade. Using self-doped polyaniline instead of common polymer as pH transducer a stable potentiometric response of 70 mV/pH was obtained, which is higher than for known systems. Taking as an example a glucose biosensor, we showed that the response of the polyaniline based electrode was 3-4 fold increased compared with the glucose-sensitive field-effect transistor. A biosensor for environmental control was made by immobilisation of organophosphate hydrolase (OPH) into self-doped polyaniline film.