The development of fluorescence immunoassays.

Radioactive markers have been of inestimable value in the establishment of immunoassays for compounds of analytical interest. It is anticipated, however, that the trend towards the development of alternative fluorescence immunoassays will continue. For example, where extreme assay sensitivity is not required, the development of simple nonseparation FIAs (e.g., fluorescence polarization FIA) will continue. However, the lanthanide chelates can be measured with high sensitivity and the specific activity of the labelled conjugates may exceed that of conjugates prepared with radioisotopes. Consequently, this approach has great potential for achieving higher sensitivity than can be obtained by conventional IRMA procedures. The components of an assay are harmless and easily disposed of. The labelled materials are very stable, showing no significant deterioration after storage for more than a year. The approach has been successfully exploited in the development of two-site immunofluorometric assays of proteins and direct, competitive binding assays of haptens. In the future, it is anticipated that the introduction of new fluorescent probes and appropriate instrumentation will facilitate the introduction of tests which may be performed in the ward, in the outpatient clinic, or in the home.