A quartz crystal microbalance assay for detection of antibodies against the recombinant African swine fever virus attachment protein p12 in swine serum

A novel, piezoelectric, quartz crystal microbalance (QCM) biosensor has been developed for the detection of antibodies against the recombinant African swine fever virus attachment protein p12. The protein p12 was immobilized on the gold surface of the crystal by adsorption. The resonance frequency of the piezoelectric crystal is associated with a mass change at the surface. The measurement of the frequency shift due to the reaction between the antigen immobilized on the piezoelectric crystal and the antibody enables the detection of the antibody. It was possible to monitor the antigen-antibody binding without the use of a label. The use of an amplified mass immunosorbent assay leads to significant enhancement of the signal. In this case, the anti-p12 antibody detection is accomplished by binding the anti-p12 antibody to the p12 protein immobilized on the QCM, followed by addition of an anti-porcine antibody conjugated to horseradish peroxidase. Subsequent exposure of 4-chloro-1-naphtol and H2O2 to the bound sandwich complex results in enzymatically amplified deposition of the oxidized 4-chloro-1-naphthol on the QCM surface, resulting in a frequency change that corresponds to the level of anti-p12 analyte. The method has a low detection limit (serum samples could be detected as positive in a dilution of 1/1500) and results can be obtained in less than 30 min. Since the immobilization of protein is simple it is possible to prepare several crystals and use this method as a screening method. (C) 1998 Elsevier Science B.V. AU rights reserved.