Piezoelectric immunosensor for SARS-associated coronavirus in sputum.

A piezoelectric immunosensor was developed for the detection of SARS-associated coronavirus (SARS-CoV) in sputum in the gas phase. Horse polyclonal antibody against SARS-CoV was bound onto the PZ crystal surface in an ordered orientation through protein A. The antigen sample was atomized into aerosol by an ultrasonator, by which the antibody on the crystal could specifically adsorb SARS antigen and the changed mass of crystal would lead a frequency shift. A frequency counter was employed to record the admittance frequency, and the plot of changed frequency was displayed on the computer. Under the optimized conditions, the frequency shifts were linearly dependent on antigen concentration in the range of 0.6-4 microg/mL. The device has good reproducibility (could be reused 100 times without detectable loss of activity), stability (the immunosensor was stable for more than two months when stored over silica gel blue at 4-6 degrees C), short analyzing time (less than 2 min), and specificity.