Magnetic transfer devices for use in solid-phase radioimmunoassays and enzyme-linked immunosorbent assays

A method was developed for the simultaneous transfer of large numbers of solid-phase adsorbents in radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). Specially coated ferromagnetic spheres (beads) were used as the solid phase. These beads were transferred from a reaction mixture through a rinse bath to another reaction mixture by magnetic probes. The quality of results obtained with this new methodology compared favorably with that obtained when solid-phase adsorbents were handled individually. The magnetic transfer system provided a high degree of mechanization, thus permitting many more tests to be performed at one time, under almost identical conditions. Certain mechanical features of the test and the micro scale of the reactions provided substantial economy in time and consumption of valuable reagents. The sensitivities of the RIA and ELISA for detection of viral antibody were about the same. An important advantage in using magnetic devices for transfer of beads is that the immune and enzyme-substrate reactions can be started and stopped instantly in either system.