CFSE Dyes

CFSE (Carboxyfluorescein succinimidyl ester) is a membrane-permeable fluorescent dye. As the dye diffuses into the cell, its succinimidyl group covalently binds to intracellular lysine residues and other free primary amines, producing green fluorescence. This stable linkage ensures retention of the dye within the cell once incorporated, without leaching onto surrounding cells. This feat of CFSE has led to widespread use in fluorescence microscopy or flow cytometry to study cell division, proliferation and migration. The dye has an excitation wavelength around 492 nm and an emission wavelength around 517 nm.