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Enzyme immunoassays , Enzyme-linked immunosorbent assay, antibody-labelled systems

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  384

2026-11-04

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Enzyme immunoassays

Enzyme-linked immunosorbent assay, antibody-labelled systems

Competitive ELISA procedures are similar to the antibody-coated microplate EIA described above. The difference is that the anti-drug antibody is enzyme labelled rather than the drug. A drug derivative is coated onto the plastic well, which serves as a way to separate bound and free fractions. The drug is conjugated to a protein using a process similar to that used to prepare an immunogen. This must be a different protein from the one used as the carrier protein to make the antibody in order to prevent binding of anti-protein antibodies made during the immunisation process. The protein–drug conjugate can be coated to the microplate well in the same manner used for coating antibodies in EIA (see above). During the assay, using similar procedures to those described for EIA, competition occurs between the drug in the sample and the immobilised drug for binding to an enzyme labelled anti-drug antibody. Following incubation, a wash step is used to separate bound and free fractions, and leave labelled antibody immobilised to the solid-phase drug derivative on the microplate well wall. The amount of labelled antibody that is bound, and responsible for the signal generation, is inversely proportional to concentration of drug in the sample.