A STUDY OF ENZYME-CATALYZED PRODUCT DEPOSITION ON PLANAR GOLD ELECTRODES USING ELECTRICAL-IMPEDANCE MEASUREMENT

An electrical impedance based specific binding assay which utilizes th e avidin-biotin interaction is described. The specific binding of a bi otinylated enzyme label, alkaline phosphatase, is determined by monito ring the change in capacitance of an avidin-coated planar gold electro de. The enzyme label alkaline phosphatase converts the substrate 5-bro mo-4-chloro-3-indolyl phosphate to an insoluble dimeric product which adheres specifically to the surface of the gold electrode and causes a maximum decrease in electrode capacitance of 55%. This capacitance ch ange is directly related to the amount of biotinylated enzyme bound to the surface of the electrode. Electrical impedance analysis has been used to characterize the surface effects on the electrode.