Immunosensors capacitance measurement system

B. Prasad and R. Lai, A capacitative immunosensor measurement system with a lock-in amplifier and potentiostatic control by software. Meas. Sci. Technol. 10,1097—1104 (1999). 

Impedimetric measurements are inherently nonselective, but the modification of electrode surfaces with selective recognition agents has resulted in selective sensing devices based on impedimetric transducers. Reviews of immunosensors and cell-based biosensors include sections on impedance transduction [177, 250, and references therein]. A review of bioelec-tronic noses, devices intended to mimic the human olfactory system in detecting and identifying odors, includes interdigital structures for complex impedance measurements and arrays of capacitive sensor elements [251]. 

Impedance immunosensors measure changes in electrical field due to biorecognition phenomena. These changes could be overall electrical conductivity of the solution and capacitance alteration due to the Ab/Ag interaction on the electrode surface, which also can be reflected in impedimetric response. Electric impedance spectroscopy (EIS) is a sensitive technique that detects the electrical response of the system studied after application of a periodic small ampHtude AC signal. In recent years, the electrochemical impedance immunosensors have attracted extensive interest in the sensing formation of Ab/Ag (Darain et al., 2004 Chen et al., 2006 Gonzalez et al., 2007 Varki et al., 1999). 

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