Radioimmunoassay (RIA) is an immunoassay technology created by Yalow and Berson in 1959 that can quantify specific antigens in samples. RIA is an immunological detection technique that uses radionuclide labeled antigen. It combines the sensitivity of radionuclide and the specificity of immune response, and is an ultra-micro determination method. The commonly used radioisotopes in RIA are I125 and I131. Because I125 has the advantages of moderate half-life, high nuclide abundance, active chemical properties, easy labeling, and small impact on the immune activity of the labeled substance, etc., it is widely used in RIA. RIA has the advantages of high sensitivity, strong specificity, simple operation, and wide application range. It can be used to determine hormones, peptides, proteins, vitamins, drugs, etc.
The radioactive labeled antigen (Ag*) and the unlabeled test antigen (Ag) in the sample competitively bind with the quantitative specific complementary antibody (Ab). Then add second antibodies specific to the complementary antibodies to bind to the complementary antibodies and form a complex that participates at the bottom of the well, thereby separating the complementary antibodies from the solution. Subsequently, centrifugation forms a precipitate containing radioactive antigens, sample antigens, complementary antibodies and secondary antibodies. Then the concentration of the target antigen in the sample can be determined by measuring the amount of conjugate (Ag*-Ab) and according to the standard curve. The target antigen content in the sample is inversely proportional to the radiation obtained.
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