EIA

EIA also known as Enzyme -Linked ImmunoSorbent Assay function based on the detection and measurement of primary antibody-antigen binding reaction.

Relevant antibody bound to a solid phrase (polystyrene microtiter plates), heat-treated broth culture (from food) is then added to the well. Unbound antigen washed away; antibody has a specific shape, it will only bind to one particular kind of antigen due to its key-and-lock principle. And only when antigens are bounded to the antibody on the polystyrene microtiter plates, will there be positive results. After the antigen is immobilized the enzyme labelled antibody (conjugate), sometimes known as detection antibody is then added, forming a complex with the antigen. The detection antibody can be covalently linked to an enzyme, or can itself be detected by a secondary antibody which is linked to an enzyme through bioconjugation. And incubated, after incubation, unbound conjugate washed away. Specific substrate which is converted by the enzyme to elicit a chromogenic or fluorogenic signal is subsequently added to show the reaction via enzymatic reactions. Followed by incubation at room temperature; to allow enzymatic reactions to take place. Reaction ceased by addition of sulfuric acid. Results read through photometer or other optical devices at specific wavelength.
ELISA tests can be categorized into indirect, sandwich or capture. Indirect ELISA is used primarily to determine the strength and/or amount of antibody response in a sample, whether it is from the serum of an immunized animal or the cell supernatant from growing hybridoma clones. Sandwich ELISA is used to determine the antigen concentration in unknown samples. Competitive ELISA is used when two “matched pair” antibodies are not available for experiment target. Different ELISA tests have different procedures however, the principles behind these tests are similar.