Surface Modification with Protein A for Uniform Binding of Monoclonal Antibodies

We describe optimal conditions for immobilization of two monoclonal antibodies to progesterone for solid-phase as-says. Polystyrene surfaces are refined with Protein A to achieve uniform, reproducible, stable, and sterically accessi-ble immobilization of immunoglobulins (I9G). To this end, we optimized the amount of immobilized Protein A, the pH of the medium for immobilization, the concentration of antibody, and the polystyrene surface. We also investigated three carriers for solid-phase assays: 12 x 75 mm polystyrene test tubes, Macrowells’TM(Skatron, Inc.; suitable for processing with multiple pipettors), and microwell strips (Immulon hIM, Dynatech Inc.). Immunoglobulin does not appreciably disso-ciate from any of these solid matrices, even if the assay procedure takes several hours. Therefore, we postulate that more than one molecule of immobilized Protein A binds t