ELISA is the abbreviation for Enzyme-Linked Immunosorbnent Assay. In the past two decades, immunological analysis methods have developed rapidly, especially after using labeled antigen and antibody analysis techniques, so that many of the original classic analysis methods can not be compared in terms of sensitivity and specificity. Following the immunofluorescence (IFA) in the 1950s and the radioimmunoassay (RIA) in the 1960s, Engvall and Perlmann published an article on enzyme linked immunosorbent assay (ELISA) for quantitative determination of IgG in 1971. This led to the development of enzyme-labeled antibody technology for antigen localization in 1966 to the determination of trace substances in liquid specimens, and the establishment of an analytical technique for labeling antigens or antibodies with enzymes. It is an immunoenzyme technology developed after immunofluorescence and radioimmunoassay, and it is a method of labeling antigens or antibodies with enzymes. Due to the high-efficiency biocatalysis of enzymes, an enzyme molecule can catalyze the reaction of dozens or hundreds of substrate molecules in a few minutes, resulting in an amplification effect, so that the original minimal antigen or antibody can be recognized in a few minutes .
ELISA test is an experimental diagnostic method with high sensitivity, strong specificity and good repeatability. Organically combining the specificity of antigen and antibody immune reaction with the principle of efficient catalytic action of enzymes can sensitively detect traces of specific antibodies or antigens in body fluids. This technology has developed very rapidly since its introduction in the early 1970s. Due to its stable reagents, easy storage, easy operation, and objective judgment of results, it has been widely used in many fields of biology and medical sciences.
Basic principle of ELISA) f1 l6 A & _ (B! I6 Z2 E
ELISA is based on immunological reaction, a highly sensitive test technique that combines the specific reactions of antigen and antibody with the efficient catalytic effect of enzyme on substrate.
The basis of ELISA is the solid phase of antigen or antibody and the enzyme labeling of antigen or antibody. There are three basic principles:
(1) The antigen or antibody can be physically adsorbed on the surface of the solid phase carrier. It may be that the hydrophobic part between the surface of the protein and polystyrene adsorbs to each other and maintains its immunological activity;
(2) The antigen or antibody can be linked to the enzyme through a covalent bond to form an enzyme conjugate, and this enzyme conjugate can still maintain its immunological and enzymatic activities;
(3) After the enzyme conjugate is combined with the corresponding antigen or antibody, it can be determined whether there is an immune reaction according to the color reaction of the added substrate, and the color reaction is proportional to the amount of the corresponding antigen or antibody in the specimen Therefore, the test results can be displayed according to the degree of coloration of the substrate.
Since the reaction of antigen and antibody is carried out in the well of a solid phase carrier-polystyrene microtiter plate, after each reagent is added to the incubation, excess free reactants can be removed by washing to ensure the specificity of the test results With stability.
During the measurement, the test specimen (the antibody or antigen in it) and the enzyme-labeled antigen or antibody are reacted with the antigen or antibody on the surface of the solid phase carrier in different steps. The antigen-antibody complex formed on the solid phase carrier is separated from other substances by washing, and finally the amount of enzyme bound on the solid phase carrier is in a certain proportion to the amount of the tested substance in the specimen. After adding the substrate for the enzyme reaction, the substrate is catalyzed by the enzyme to become a colored product. The amount of the product is directly related to the amount of the test substance in the specimen, so it can be qualitatively or quantitatively analyzed according to the depth of the color reaction. Since the catalytic frequency of the enzyme is very high, the reaction effect can be greatly amplified, so that the measurement method reaches a high sensitivity.
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