Biochemical Techniques and Instrumentation

3.2.2. Technique

An antigen is immobilized on a solid support usually a polystyrene microtiter plate. Immobilization is done either non-specifically, through adsorption to the surface or specifically, through capture by another antibody specific to the same antigen. The detection antibody is then added to form a complex with the antigen. The detection antibody can covalently link to an enzyme, or can itself be detected by a secondary antibody which is linked to an enzyme through bioconjugation. The plate is typically washed with a mild detergent solution between each step to remove any antigen or antibodies that are not specifically bound. The plate is then developed by adding an enzymatic substrate to produce a visible signal, which indicates the quantity of antigen in the sample.