A reproducible piezoelectric immunosensor has been developed for the antibody of Schistosoma-Japonicum (SjAb). The surface of quartz crystal microbalance (QCM) is prepared first with plasma polymerized film of butyl amine by glow-charge and then covered with polyelectrolyte by self-assembling. Through strong electrostatic attraction, opposite-charged SjAg is incubated on it by controlling the pH value. Subsequently, the nonspecific sites on the immunosensor are sealed by BSA and NRS in order to detect SjAb in the infected rabbit serum (IRS). The effects of experimental conditions including the self-assembling of polyelectrolyte, the incubation of SjAb, the test of immunoreaction and the properties of immunosensor are all investigated, respectively. Furthermore, the detemination and reproducibility of this self-assembling approach by polyelectrolyte are illustrated with obvious advantages over those of the binding approach by glutaraldehyde. It is demonstrated that this immunosensor is perfect in sensitivity, selectivity, and reproducibility. In the optimal experimental conditions, the QCM technique has been used to determine a series of IRS with different infected extent, implying that it is a practical tool for qualitative and quantitative detection of Schistosoma-Japonicum in clinical laboratory.

Key words: PLASMAS, POLYMER FILMS, POLYELECTROLYTE, FIXATION, SENSORS, SCHISTOSOMA JAPONICA