Electrophoresis-Assisted Active Immunoassay

An active assay can be defined as that in which diffusion-controlled reactions are replaced by active delivery of analytes to probe molecules. The present paper describes an electrophoresis-assisted version of an active ELISA performed in tubes or wells with a dialysis membrane attached to their bottoms. The permeability of such a membrane to small ions allows us to apply electric field perpendicular to the membrane surface and to rapidly transport and concentrate charged macromolecular analytes in its vicinity. Probe molecules were either adsorbed or covalently linked to a modified surface of a membrane from regenerated cellulose. An active assay was performed both in separate cells and in 96-well microplates. It was demonstrated that the active assay format allows one (i) to reduce assay time to minutes instead of hours, (ii) to increase sensitivity by a factor of 10-300, and (iii) to capture within 10 min up to 70% of all the analyte molecules present in 0.36 mL of solution.