Latex-based thin-layer immunoaffinity chromatography for quantitation of protein analytes

A rapid immunochromatographic method for qualitativeand quantitative analysis of protein antigens is described. The method is based on the ‘sandwich” assay format using monoclonal antibodies (Mabs) of two distinct specificities. Mabs of one specificity are covalently immobilized to a defined detection zone on a porous membrane while Mabs of the other specificity are covalently coupled to blue latex particles which serve as a label. The sample is mixed with the Mab-coated particles and allowed to react. The mixture is then passed along a porous membrane by capillary action past the Mabs in the detection zone, which will bind the particles which have antigen bound to their surface, giving a blue color within this detection zone with an intensity logarithmetrically proportional to the antigen concentration in the sample. Analysis is complete in less than 10 min, requires a minimum amount of sample (4 μl), and has a detection limit below the nanomolar range for the antigen we studied, human chorionic gonadotropin.