Magnetic immunoassay system utilizing magnetic marker and SQUID sensor

点击翻译按钮获取中文摘要

Immunoassays are widely used to detect disease-related proteins for medical diagnostics. These proteins are generically called antigens, and the so-called binding reaction between antigen and its antibody is used for the immunoassay. In order to improve the performance of the immunoassay, we have developed a new detection system utilizing a magnetic marker and a SQUID sensor. The main results obtained in this study are as follows.(1)We clarified the dependence of the magnetic properties on the size of the magnetic nanoparticle. We showed that the particle with nominal diameter of 25 nm can keep remanence, and can generate large magnetic signal. This particle is, therefore, suitable for magnetic immunoassay.(2)We developed a coating process to cover the magnetic particle with polymer. With this process, we fabricated a polymer-coated magnetic nanoparticle that shows good dispersion in liquid.(3)We developed the high Tc SQUID system for detecting magnetic signal from the marker. Since the signal decays rapidly in space, we realized a close distance between the cooled SQUID and the room temperature sample.(4)We developed a magnetic-contamination free reaction chamber and a method to cancel environmental noise in order to detect very weak signal. Our system can detect 12 samples in a short measurement time of a few minutes with a field resolution of about 10 pT.(5)We conducted a detection of protein called IgE. We demonstrated the detection of IgE down to 0.3 pg, which shows the high sensitivity of the present magnetic method. We also demonstrated the detection of IgE in human serum, which shows the possibility to practical diagnosis.