Enzyme-linked immunosorbent assay (ELISA) is a test that uses antibodies and color change to identify a substance. ELISA is a popular format of a "wet-lab" type analytic biochemistry assay that uses a solid-phase enzyme immunoassay (EIA) to detect the presence of a substance, usually an antigen, in a liquid sample or wet sample.

ELISA is used as a diagnostic tool in plant medicine and pathology, as well as for quality control in various industries. Bdnf ELISA kit is used for detecting and quantifying proteins and antigens from various samples.

Indirect ELISA

The "indirect" ELISA steps follow the following mechanism:

A primary antibody is added which specifically binds to the test antigen covering the well. These primary antibodies can also be found in donor serum, which will be tested for antigen reactivity.

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A secondary antibody is added which binds to the primary antibody. Enzymes often bind to these secondary antibodies, which have little effect on the binding properties of the antibody.

The higher the concentration of the primary antibody in the serum, the stronger the color change. Spectrometers are often used to measure color strength.

ELISA sandwich

ELISA sandwiches. (1) Plates are coated with capture antibody; (2) sample is added and any available antigen is bound to capture antibody; (3) detecting antibody is added and bound to the antigen; (4) an enzymatically linked secondary antibody is added and bound to the detection antibody; (5) the substrate is added and converted into a form that can be detected by the enzyme.

Competitive ELISA

The third use of ELISA is for competitive binding. Some competing ELISA kits contain enzyme-linked antigens rather than enzyme-linked antibodies.

The labeled antigen competes with the sample antigen (unlabeled) for the binding site of the primary antibody. The more antigens in the sample, the more labeled antigens are deposited in the well and the stronger the signal.