A Doppler assay for the antigen--antibody reaction.
The specific combination of antigen with antibody was detected rapidly and with high sensitivity by an assay based on particle electrophoresis and laser light scattering. Antibody attachment to dilute suspensions of submicroscopic polystyrene spheres coated with antigen was detected as changes in the Doppler shift of scattered laser light when the suspended particles were subjected to an electric field. Antibody or antigen concentrations in the range of 5--10 nanograms per ml can be detected in 30 min. The principal experimental features of the technique are described and include: a) choice of particles; b) coating procedures; c) treatment for non-specificity; d) choice of measurement medium.
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