A Guide To ELISA

The enzyme-linked immunosorbent assay (ELISA) is one of the most commonly used labeled immunoassay techniques. It is based on an enzyme-labeled antibody capable of detecting an antigen immobilized to a solid surface, 96-well or 384-well polystyrene plates.

The substrate is added to produce a color change or light signal corresponding to the amount of antigen present in the original sample. This is an easy and fast way to detect antibodies or antigens adhering to hard surfaces. You can easily order elisa kit from various online sources.

ELISA format

Depending on the differences in antigen immobilization strategies, antibody labeling strategies, and the type of antibody-antigen reaction (direct recognition or competition), ELISAs can be presented in different formats. Everyone has their own advantages and disadvantages. The optimal ELISA format can be chosen flexibly depending on the requirements.

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1. Live ELISA

This is the simplest form of ELISA. The antigen passively adheres to the plastic solid phase during the incubation period. After a simple washing step, the antigen is detected by adding an antibody that is covalently bound to the enzyme.

After incubation and washing, the test was carried out by adding a chromogen/substrate, where the enzyme activity caused a color change.

2. Indirect ELISA

The indirect detection method adds a labeled secondary antibody for detection based on direct ELISA and is the most popular ELISA format. The antigen is passively bound to the well by incubation. After washing, the antigen-specific antibodies are incubated with the antigen.

The wells were washed and bound antibodies were detected by the addition of an anti-species antibody covalently bound to the enzyme. The antibody is specific for the species in which the first additional antibody was produced.

3. ELISA sandwich

Sandwich ELISA is one of the most useful formats for immunoassays and is designed to detect soluble antigens. There are two forms of this ELISA, depending on the amount of antibody used. The principle is the same for both, instead of adding the antigen directly to the solid phase, the capture antibody is immobilized in the solid phase to capture the antigen.