Enzyme Immunoassay and Related Bioanalytical Methods

Authored by: John W.A. Findlay

Encyclopedia of Pharmaceutical Science and Technology

Print publication date:  July  2013
Online publication date:  July  2013

Print ISBN: 9781841848198
eBook ISBN: 9781351124874
Adobe ISBN:


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Enzyme immunoassay, a bioanalytical method incorporating an antigenantibody reaction to capture the analyte of interest and an enzyme reporter system to detect the captured analyte, is one of the most widely used immunoassay formats. The method is sometimes applied only qualitatively to indicate the presence of an antigen in a matrix. However, in the more common quantitative implementation, a calibration (standard) curve is incorporated, from which the concentration of the analyte in unknown samples is interpolated. In the decades since the development of a radioimmunoassay for insulin by Yalow and Berson (1), immunoassays have been widely applied in support of medical practice and drug development. However, there has been a decline in the application of immunoassays to the quantitation of low-molecular-weight xenobiotics, primarily due to the advent of liquid chromatographymass spectrometry (LC-MS) methods, which have high sensitivity and specificity. This is particularly so for support of early drug discovery, where assay development times of as little as a day and analytical run times of only a few minutes per sample make LC-MS ideally suited to fast delivery of results to discovery scientists. Nonetheless, the remarkable specificity of antibodies allows their application in wellcharacterized immunoassays to the support of Phase III and Phase IV clinical trials as a costeffective alternative to LC-MS methods. In addition, these methods are still widely used for therapeutic drug monitoring and analysis of low-molecular-weight hormones, such as steroids, in support of medical diagnostics. Immunoassays remain the method of choice for the quantitation of protein macromolecules and antibodies in complex matrices. Another major application of immunoassays is in the detection and quantitation of biomarkers, which are evolving to be of pivotal importance in the evaluation of pharmacological, toxicological, and clinical activities of candidate drugs (2).

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