Magnetorelaxometry -: a new binding specific detection method based on magnetic nanoparticles

The measurement of the relaxing magnetisation of magnetic nanoparticles after switching off a magnetising field (magnetorelaxometry) was investigated towards its applicability for the determination of the binding of antibodies to their antigens. For this purpose a direct solid phase immunoassay using magnetic nanoparticles conjugated with an antibody against human IgG and a sandwich solid phase immunoassay using the identical biotinylated antibody against human IgG and magnetic nanoparticles conjugated with streptavidin were performed. Both assays yielded binding specific magnetic nanoparticle relaxation signals that were dependent on the amount of antigen. The comparison of the magnetic relaxation immunoassay (MARIA) with an established immunoassy technique (enzyme-linked immunosorbent assay, ELISA) showed, that both techniques yielded well comparable results. (C) 2002 Elsevier Science B.V. All rights reserved.