A cell-permeable dye that is cleaved by intracellular esterases, leaving membrane-impermeant calcein, a fluorescent indicator with absorption and emission maxima of 494 and 517 nm, respectively.

Calcein AM or Calcein acetoxymethyl ester is a hydrophobic compound which passes easily through cell membrane into live cells and is used for cell viability assays. The non-fluorescent calcein AM dye is hydrolyzed by cellular esterases to give calcein which is fluorescent and is retained in the…