Label-free detection of DNA hybridization with EIS measurements

We report a new approach for detecting DNA hybridisation using nonFaradaic electrochemical impedance spectroscopy. The technique was applied to a system of DNA probes bearing amine groups that are immobilized by covalent grafting on a supporting polypyrrole matrix functionalised with activated ester groups. Results show a significant modification in the Nyquist plot upon addition of the complementary target whereas, in the presence of the noncomplementary target, the Nyquist plot is not modified. The spectra, in the form of Nyquist plot, were analysed with the Randles circuit. The transfer charge resistance R/sub 2/ shows linear variation with the complementary target concentration.