7-Aminoactinomycin D (7-AAD) is a DNA dye that distinguishes viable, apoptotic, and late apoptotic/dead cells in flow cytometry. 7-Aminoactinomycin D staining with 5 μg/mL, 10 μg/mL, and 20 μg/mL, but not with 1 μg/mL, is suitable for quantification of apoptosis in flow cytometry.
7-Aminoactinomycin D is frequently used to stain and exclude dead cells in flow cytometry at low concentrations (0.5-5 μg/mL). At higher concentrations (10-20 μg/mL), 7-Aminoactinomycin D has also been used to distinguish between viable cells (7-AAD _negative ) and apoptotic cells (7-AAD _dim ) or dead cells (7-AAD _bright ) using the fact that permeability of the cell membrane, and hence fluorescence intensity, is low in early apoptotic cells and high in late apoptotic and dead cells.