The use of impedance spectroscopy for the characterization of protein-modified ISFET devices: Application of the method for the analysis of biorecognition processes

Impedance spectroscopy is used to characterize the structure of biomaterial layers on the gate surface of ISFET devices, and to elucidate antigen-anti body binding interactions on the gate interface. The method is based on the recording of the transfer function of the system as a function of frequenc y and on the extraction of the respective iota (1) and iota (2) values of t he systems. From the experimental values, the film thicknesses of the respe ctive protein layers are estimated. The method is applied to elucidate the structures of a glucose oxidase, GOx, multilayer assembly, and of a di-biot in-cross-linked avidin multilayer system. The method is also used to sense the dinitrophenyl antibody by following the formation of the antigen-antibo dy complex on the gate surface.