A popular assay in biological laboratories is the radioactive chromium IV release assay that measures cell cytotoxicity in a mixed population of cells. One of the most popular uses of this assay is to measure cell-death that is mediated by other cells such as Macrophages, Cytotoxic T Cells (CTLs), or Natural Killer (NK) cells. But one of the major drawbacks of the chromium release assay is that it uses radioactive 51Cr material, which is dangerous and requires costly clean up.
An alternative to this radioactive chromium assay is a safer, time-resolved fluorescence assay that uses the lanthanide europium (Eu3+). Briefly cells are preloaded with a fluorescence enhancing ligand, BATDA, which penetrates the cell membrane. BATDA is quickly hydrolyzed within the cell to form the hydrophobic ligand TDA. When the cell membrane is lysed upon cell-mediated cytotoxicity, the released TDA binds to free Eu3+. This forms a Eu-TDA chelate that can then be measured using time-resolved fluorescence.
For more information on how to perform this assay using the PHERAstar microplate reader, please see Application Note 192: A DELFIA® time-resolved fluorescence cell-mediated cytotoxicity assay performed on the PHERAstar.
Delfia is a registered trafemark of Perkin Elmer Inc.