ABSTRACT
The majority of immunoassays that use enzymes as signal generators are designed for the colorimetric, i.e., spectrophotometric detection of products generated by the enzymatic biocatalyst in response to varying analyte concentrations in the sample. Spectrophotometric detection has a long tradition in analytical chemistry and it is therefore not surprising that enzyme immunoassays from their early inception were adapted to the measurement of colored reaction products. Furthermore, the immobilization of antibodies to solid matrices, the utilization of this technology in microplates for which multiple pipettors were already available, and the subsequent development of the microplate reader, a spectrophotometer that can measure the color intensity of 96 wells in about 1.5 minutes, established the colorimetric immunoassay as a standard technique in the analytical laboratory. Other techniques for signal generation using microplates followed suit: luminescent, fluorescent, and y-radiation detection. In principle, an enzyme immunoassay can be as easily quantified by amperometric detection of products generated by enzymatic reactions. Although research groups began to explore this technology in the early seventies, there was no strong commercial incentive for the development of other detection methods such as electrochemical detection in immunoassays.
