4,6-Diamidino-2-Phenylindole (DAPI)

4',6-diamidino-2-phenylindole (DAPI) is a fluorescent stain that binds strongly to A-T rich regions in DNA. It is used extensively in fluorescence microscopy. DAPI can pass through an intact cell membrane therefore it can be used to stain both live and fixed cells, though it passes through the membrane less efficiently in live cells and therefore the effectiveness of the stain is lower. DAPI can be used for fixed cell staining, the concentration of DAPI needed for live cell staining is generally very high and rarely used for live cells. It is labeled non-toxic in its MSDS and though it was not shown to have mutagenicity to E. coli, it is labelled as a known mutagen in manufacturer information. As it is a DNA binding compound it is likely to have some low level mutagenic properties and care should be taken in its handling and disposal.