Detection by enzyme-linked immunosorbent assay: ELISA
ELISA is a rapid immunochemical test used to detect substances with antigenic properties (primarily proteins), bacterial antigens and antibodies, and other substances. The following text and the animation illustrate the basics of enzyme-linked immunosorbent assay, as performed by the ESP. It may be helpful to pause the animation at each step to read the associated text.
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People who work on toxins, looking for gene products have a different focus. They are looking for amino acids (proteins) and using antibodies to find molecules.
- For ELISA, the printed probe array consists of a toxin-protein conjugate (a protein combined with an antigen) that the target antibody recognizes. In this example the target antibody is in domoic acid, an algal toxin.
- The ESP collects a sample of water, makes an extract mixed with an antibody (A) that is looking for domoic acid. The extract is flowed onto the array surface which is printed with the protein (P).
- Then a competition takes place. If no toxin is present, the antibody gets bound to the protein array. If lots of toxin is present, the antibody gets bound to the toxin in the solution and is washed away.
- Then an enzyme solution is brought in to create a signal (or not) that indicates whether the toxin is present.
As in SHA the signal is light, but in this case, the light indicates absence of the target. The brighter the spots recorded by the camera, the less target present.
Below is a static view of the complete process illustration.