Comparison between electrochemical and optoelectrochemical impedance measurements for detection of DNA hybridization

The principles of the electrochemical and optoelectrochemical impedance mea surements on bare electrolyte/dielectric/semiconductor structures are descr ibed. The analysis of the experimental curves allows access to several indi cations concerning the electrical behavior of such structures. The applicat ion of these techniques to follow the electrical behavior of structures mod ified with two biological systems was investigated. The antibody/antigen re cognition did not change the surface charge and, therefore, did not affect the impedance curves with respect to the applied potential. By contrast, th e hybridization of two complementary DNA strands on the surface of the stru cture induced a variation of flat band potential of the semiconductor leadi ng to a shift of impedance curves along the potential axis. This means that it is possible to detect directly the DNA hybridization without the use of labeled probes. The use of light allows the surface to be probed locally. Tn the future, the application of this technique for direct detection of hy bridization on DNA chips should he possible.