The enzyme linked immunosorbent assay (ELISA) (GLORY SCIENCE CO., LTD) can be used to determine antigens or antibodies. There are three necessary reagents in this method: The antigens or antibodies of the solid phase, the antigens of the enzyme, or the substrate of the enzyme. Different types of detection methods can be designed according to the source of reagent, the characteristics of specimen and the conditions of detection. The application of biotin- streptavidin system in ELISA has many forms.
- Used for indirect package: It can be prepackaged in the solid phase by the chain musty In advance. The original adsorption method is used to bind the antibody or antigen of the solid phase to the biotin, which can be used to make the biotin antibody or antigen indirect package by the streptavidin- biotin reaction. This method has the following advantages: ①It increases the amount of antibodies or antigens that are attached to it, and makes its binding points sufficiently exposed. ②There is low base of negative control and white space, high sensitivity. ③The microporous are coated by streptavidin instead of antibody, this avoids the inactivation of microporous are coated by antibody. ④This overcomes the deficiency of antigen antibody binding ability caused by traditional physical adsorption methods. ⑤Due to the strong affinity between the streptavidin and biotin, and it's highly specific and stable. Therefore, the detection sensitivity can be improved.
- Used for terminal reaction amplification: The enzymatic antibody in conventional ELISA can also be replaced by biotinylated antibodies, and then the streptavidin- enzyme conjugate is connected to amplify the reaction signal. Due to the low voltage, the surface band has less positive charge of streptavidin, so the electrostatic adsorption of it and polystyrene board is weak. The negative control of streptavidin was significantly lower than that of avidin. Thus applying streptavidin on ELISA can further improve the sensitivity. Streptavidin is active adsorption of biotinylated antibodies, the biotinized antibodies are attached to the surface of streptavidin, and it is arranged in order and evenly distributed, and it is easy to maintain function. However, the passive adsorption antibody is highly irregular and it can cause a large number of antibodies to lose their function. Therefore, biotin- streptavidin immune response system introduced into competitive method, which can greatly improve the sensitivity and specificity of ELISA.