SELECTIVE AND REPEATABLE DETECTION OF HUMAN SERUM-ALBUMIN BY USING PIEZOELECTRIC IMMUNOSENSOR

Improvements of the sensitivity and stability of a piezoelectric immunosensor for human serum albumin (HSA) have been examined. A change in resonance frequency (Delta F: sensitivity) is observed when an HSA solution is allowed to flow onto a quartz-crystal sensor immobilized with anti-HSA monoclonal antibody. Delta F is found to increase further by about three times upon subsequent exposure to a flow of the polyclonal antibody solution owing to the formation of a complex of HSA sandwiched between the two types of antibody. The final value of Delta F varies almost linearly with the HSA concentration in the range 0-20 ppm, with a sensitivity of approximate to 20 Hz ppm(-1). The resonance frequency returns reversibly to the initial level on exposure to an acidic buffer solution (pH 3.0). Furthermore, the measurement of HSA can be repeated up to about 30 times with the same sensor without a significant change in sensitivity. These results confirm that the sensor has sufficient sensitivity as well as good repeatability to be applied to a liquid flow-type HSA assay system.