SQUID BASED REMANENCE MEASUREMENTS FOR IMMUNOASSAYS

The use of fine magnetic particles as labels antibodies and the measur ement of their remanent magnetization for the preparation of immunoass ays is presented. Antibodies were coupled with magnetic nanoparticles and samples were prepared by reaction of the magnetically labeled anti bodies with their solid phase adsorbed antigen. after exposing the sam ples tar a field of some mT a dc-SQUID system measures the remanent sa mple magnetization in the absence of an external field. The combinatio n of high moment labels and SQUIDs yields ultrasensitive immunoassays with a wide range of detectable analyte concentrations. In contrast to most standard techniques tar our method the detected magnetic signal is specific only for bound reaction partners, thus eliminating the nee d for separation of unbound components.