Time-resolved fluorescence in biospecific assays.

Fluorescent lanthanide chelates and their detection using time-resolved fluorometry for in vitro as well as for microscopic bio-specific assays are reviewed, with reference to other fluorescent dyes and labelling materials. The minimum detectable dose of labelled components and the theoretical ultimate sensitivities of immunoassays and DNA-assays are discussed and compared with experimental results. It is concluded that the time-resolved fluorometry provides a high sensitivity labelling method in immunoassays, and a sensitivity comparable to phosphorus-32 in DNA hybridization assays. It is also concluded that lanthanide chelates are a potential alternative for organic fluorescent dyes in microscopy and that they are most useful in multiparameter assays. The combination of organic fluorescent dyes and lanthanide chelates provides the highest separation efficiency between two assay parameters.