Solid-phase radioimmunoassays

Solid-phase coupled antibodies were introduced to facilitate the separation of bound and free labelled ligand in the competitive inhibition radioimmunoassay. Originally, the solid matrix used was in the form of small particles and since then a number of different matrices have been used such as very fine powder particles, gels, paper and plastic discs, magnetic particles and the inside surface of plastic tubes. The coupling of antibodies may be that of a covalent chemical binding, a strong physical adsorption, or an immunological binding to a solid-phase-coupled antigen. New principles of radioimmunoassay, such as the solid-phase sandwich techniques and the immunoradiometric assay, were developed from the use of solid-phase-coupled antigens and antibodies. The solid-phase sandwich techniques are reagent-excess methods with a very wide applicability. Several of the different variants of solid-phase techniques are suitable for automation. Advantages and disadvantages of solid-phase radioimmunoassays when compared with assays using soluble reagents are discussed. (author)