Novel antibody coating of a magnetizable solid phase for use in enzyme immunoassays

Novel kinds of magnetizable particles have been prepared using the interaction between the complexing groups of phosphonic acid and polyvalent metal ions on the surface of Fe3O4 particles. After modification of monoclonal and polyclonal antibodies by the bifunctional chelating agent 2-(4-di-azophenyl)-1-hydroxyethane-1,1-bisphosphonic acid, antibodies were immobilized at a ratio of 5–10 mg antibody molecules per ml Fe3O4 particles without loss of immunological reactivity. Very sensitive and fast immunoenzymometric assays for the quantitative determination of human interferon-α1 and mouse immunoglobulins were developed using such particles. The advantages of the method include immobilization of proteins on magnetizable carriers without chemical modification of the carrier and the short assay time compared to conventional immunoenzymometric assays.