The Calcein AM Cell Viability Assay Kit is a kit that uses the fluorescent probe calcein AM to detect cell viability. Calcein AM is a cell-permeable derivative of calcein, which makes it easier to enter cells. Once inside the cells, no-fluorescent calcein AM is hydrolyzed into green-fluorescent calcein by esterases. Calcein is highly negatively charged and is remained in the cells. Since dead cells lack esterase enzymes, calcein AM can only stain live cells, and its fluorescence signal is proportional to the number of living cells.
Calcein AM has low toxicity to cells, so it is currently one of the most ideal probes for live-cell staining. In addition, calcein AM is more sensitive than common reagents (e.g., MTT, CCK-8) for detecting cell viability/proliferation, as this kit can detect as few as 50 cells per well.