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What are the functions of ELISA kit?

2022-12-23

ELISA kit is based on solid phase of antigen or antibody and enzyme labeling of antigen or antibody. The antigen or antibody bound to the surface of the solid carrier still retains its immunological activity, and the enzyme labeled antigen or antibody retains both its immunological activity and the enzyme activity. At the time of determination, the specimen under test (in which the antibody or antigen is measured) reacts with the antigen or antibody on the surface of the solid carrier. The antigen-antibody complex formed on the solid carrier is separated from other substances in the liquid by washing.

Enzyme-labeled antigens or antibodies are added, which also bind to the solid carrier by reaction. At this time, the amount of enzyme in the solid phase is in proportion to the amount of substance in the specimen. After adding the substrate of the enzyme reaction, the substrate is catalyzed by the enzyme to become colored products. The amount of the product is directly related to the amount of the tested substance in the specimen, so qualitative or quantitative analysis can be carried out according to the depth of the color.

The high catalytic efficiency of enzymes indirectly amplifies the results of the immune response, making the assay highly sensitive. ELISA can be used to determine antigens, but also can be used to determine antibodies.

Basic principles of ELISA kit
It uses specific reaction of antigen and antibody to connect the object to enzyme, and then produces color reaction between enzyme and substrate for quantitative determination. The object of measurement can be antibody or antigen.

There are three reagents necessary in this method of determination:
① Solid phase antigen or antibody (immune adsorbent)
② Enzyme labeled antigen or antibody (marker)
③ substrate for enzyme action (color development agent)

In the measurement, the antigen (antibody) is first bound to the solid carrier, but still retains its immune activity, and then a conjugate (marker) of antibody (antigen) and enzyme is added, which still retains its original immune activity and enzyme activity. When the conjugate reacts with the antigen (antibody) on the solid carrier, the corresponding substrate of the enzyme is added. That is, catalytic hydrolysis or REDOX reaction and color.

The shade of color it produces is proportional to the amount of antigen (antibody) to be measured. This colored product can be observed by the naked eye, optical microscope, electron microscope, can also be measured by spectrophotometer (enzyme label instrument). The method is simple, convenient, fast and specific.

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