Calcein-AM, the acetoxymethyl ester of calcein, is highly lipophilic and cell membrane permeable. Though Calcein-AM itself is not a fluorescent molecule, the calcein generated from Calcein- AM by esterase in a viable cell emits strong green fluorescence (excitation: 490 nm, emission: 515 nm). Therefore, Calcein-AM only stains viable cells.

Propidium Iodide (PI) is a red fluorescent dye that cannot penetrate intact cell membranes. Upon cell death, PI can enter the cell and specifically bind to double-stranded DNA in the nucleus, emitting red fluorescence (Ex/Em = 535 nm/617 nm).

MCE Viability/Cytotoxicity Assay Kit for Live & Dead Cells (Calcein/PI) enables dual fluorescent staining of both live and dead cells, making it suitable for assessing cell viability and cytotoxicity. When excited at 490 nm, both live and dead cells can be observed simultaneously under a fluorescence microscope. However, when excited at 545 nm, only dead cells can be observed.

This kit is suitable for various fluorescence detection systems, including fluorescence microscopes, flow cytometers, and fluorescent microplate readers. It is compatible with the detection of most mammalian cells. However, due to the cell walls of fungi and bacteria, which hinder the entry of Calcein-AM into cells, this kit is not suitable for use with bacteria and fungi.