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ELISA Assay

The specific reaction between antigen and antibody is used to connect the substance to be tested with the enzyme, and then a color reaction is generated between the enzyme and the substrate for quantitative determination. The object of determination can be an antibody or an antigen. There are three necessary reagents in this method: 1. antigen or antibody in solid phase (immunosorbent); 2. antigen or antibody labeled with enzyme (marker); 3. substrate for enzyme action (chromogenic agent). During the determination, the antigen (antibody) is first bound to the solid-phase carrier but still retains its immune activity, and then an antibody (antigen) is added to combine with the enzyme to form a conjugate (marker). The conjugate still retains its original immune activity and enzyme activity. When the conjugate reacts with the antigen (antibody) on the solid-phase carrier, it is added to the corresponding substrate of the enzyme to catalyze hydrolysis or redox reaction and show color. The color depth generated by it is related to the amount of antigen (antibody) to be tested. This colored product can be observed by the naked eye, optical microscope, and electron microscope, and can also be measured by a spectrophotometer (enzyme labeling instrument). The method is simple, convenient, rapid, and specific.

High Sensitivity

The sensitivity of ELISA comes from the enzyme as the reporter group. An enzyme is an organic catalyst. A small amount of enzyme can induce a large number of catalytic reactions and produce a co-observable color reaction phenomenon. Therefore, the ELISA system is also called an enzyme amplification system. ELISA can trace the location of antigen or antibody at the cellular or subcellular level or quantify it at the microgram or even nanogram level.

Strong Specificity

The specificity of ELISA comes from the selectivity of antibodies or antigens. In essence, the binding of antigen and antibody only occurs between the antigen determinant of the antigen and the antigen binding site of the antibody. Because of their complementary relationship in chemical structure and spatial configuration, antigen antibody reactions have high specificity.

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