Elisa

Enzyme-linked immunosorbent assay (ELISA), is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay (EIA) to detectthe presence of a substance, usually an antigen, in a liquid sample or wet sample.
The ELISA has been used as a diagnostic tool in medicine and plant pathology, as well as a quality-control check invarious industries. Attempting to detect (and quantify) the presence of the antigen in the sample proceeds as follows: Antigens from the sample are attached to a surface. Then, a further specificantibody is applied over the surface so it can bind to the antigen. This antibody is linked to an enzyme, and, in the final step, a substance containing the enzyme's substrate is added. The subsequentreaction produces a detectable signal, most commonly a color change in the substrate.
Performing an ELISA involves at least one antibody with specificity for a particular antigen. The sample with anunknown amount of antigen is immobilized on a solid support (usually a polystyrene microtiter plate) either non-specifically (via adsorption to the surface) or specifically (via capture by anotherantibody specific to the same antigen, in a "sandwich" ELISA). After the antigen is immobilized, the detection antibody is added, forming a complex with the antigen. The detection antibody can be covalentlylinked to an enzyme, or can itself be detected by a secondary antibody that is linked to an enzyme through bioconjugation. Between each step, the plate is typically washed with a mild detergentsolution to remove any proteins or antibodies that are not specifically bound. After the final wash step, the plate is developed by adding an enzymatic substrate to produce a visible signal, whichindicates the quantity of antigen in the sample.
Of note, ELISA can perform other forms of ligand binding assays instead of strictly "immuno" assays, though the name carried the original "immuno" because...