Application of solid-phase antibodies to radioimmunoassay Evaluation of two polymeric microparticles, Dynospheres and nylon, activated by carbonyldiimidazole or tresyl chloride

Two types of polymeric microparticle, Dynospheres and reprecipitated acid-hydrolysed nylon 66, and two methods of activating these particles with either tresyl chloride or carbonyldiimidazole (CDI) prior to covalent linkage of antibodies were investigated with a view towards their respective adoption for the preparation of general solid-phase reagents for immunoassay applications. Activation of each particle and coupling of antibodies was rapid irrespective of the activator. CDI proved to be the activator of choice since it was cheap, less hazardous, more efficient and less pH dependent than tresyl chloride. Both types of microparticle remain buoyant during the RIA incubation periods and form stable pellets after centrifugation. In second antibody applications immobilisation of the first antibody occurs with a short incubation period of 30 min. Nylon microparticles have a higher antibody-coupling capacity and are the particles of choice in both first and second antibody applications. However, the nylon microparticles possess marginally higher non-specific binding characteristics.