A direct immunoassay for schistosoma japonium antibody (SjAb) in serum by piezoelectric body acoustic wave sensor

A piezoelectric immunosensor was proposed for the determination of schistosoma japonium antibody (SjAb) in rabbit serum. On the surfaces of quartz crystals with a resonant frequency of 9 MHz, a 32 kDa molecular antigen of schistosoma japonicum (SjAg) was immobilized via a copolymer coating of hydroxyethyl methacrylate and methyl methacrylate. By exposing the crystals to an SjAb solution, the antibody was determined in the range of 7.2-90 mu g ml(-1). Several rabbit serum samples with different infecting degrees were analyzed and the results demonstrated that the concentration detectable in this system already meets the demands of clinical analysis. Moreover, the valent value of the binding antigen and the affinity constant were estimated to be 0.676 and 2.20 x 10(6) mol l(-1), respectively. (C) 1999 Elsevier Science B.V. All rights reserved.