A PEG piezoelectric immunoassay for the determination of transferrin in human serum

A new liquid piezoelectric immunoassay, termed as PEG piezoelectric immunoassay, has been proposed for the direct determination of transferrin in human serum. The method is based on the agglutination of antigen and antibody by immunoreaction with PEG as a promotor. The response mechanism of the method was investigated in detail. It was found that some immune agglutinates were adsorbed onto the crystal surface and played an important role in the frequency response of the piezoelectric crystal. The effects of the concentration and molecular weight of PEG, the TA dilution and the reaction temperature on the response frequency were studied in detail. Under the optimized conditions, the linear detection ranges for transferrin concentration obtained by the end-point method and by the initial rate method were 0.24–8.36 and 0.16–8.27 μg ml−1, respectively. The detectable concentration matches the demands of clinical assays. Seven clinical samples were analyzed by the method, and the analytical results were in satisfactory agreement with those given by the rate diffusion turbidimetry. With a simple regeneration, piezoelectric crystal can be used for more than a hundred times with no decrease in sensitivity.