ELISA (Enzyme-linked immunosorbent assay) is a simple, cost-effect technique performed on serum, plasma, cell supernatant, and other biological fluids to determine the presence of an antigen in a sample.
Sandwich ELISAs utilize multiple-well microtiter plates, coated with capture antibodies, to capture soluble proteins. The bound proteins are then detected with a subsequent detection antibody, which is typically labeled with an enzyme, or biotinylated and then followed with streptavidin-enzyme conjugate. A colorimetric substrate is then added, which results in a color change based on the amount of antigen captured. By using a plate reader and plotting resulting values on a standard curve, precise, quantitative values can be obtained.