SQUID Microscope System for Biological Immunoassay

点击翻译按钮获取中文摘要

In this project, we have developed a SQUID microscope system for the application to biological immunoassay. In this system, an antibody is labeled with the so-called magnetic marker, and the binding reaction between antigen and its antibody is detected by measuring the magnetic signal from the marker. Utilizing a highly sensitive SQUID sensor that can measure very weak magnetic signal, we can detect very small binding reaction. Since the SQUID has to be cooled to T=77 K, we developed the SQUID microscope where the distance between the SQUID and the room temperature sample can be made less than 1 mm. We also developed a new marker using the Fe_3O_4 magnetic nanopartice with diameter of 25 nm. This marker can generate magnetic signal 10 times larger than the conventional marker with diameter of 10 nm. This marker can also keep the remanent magnetic field after the marker is magnetized with a large field. Using the SQUID microscope and the new marker, we can detect the marker as small as 1 pg. We also made an immunoassay experiment. For the antigen, we used the protein called IL8. At present, we can detect the IL8 as small as 1 pg. However, we can expect to detect the IL8 less than 0.1 pg from the noise performance of the system. Since the magnetic contamination of the substrate limits the detection level at present, we have to solve this problem in order to detect the IL8 of 0.1 pg.