Alamar blue contains resazurin, which is a nontoxic, cell-permeable, REDOX indicator dye. The alamar blue assay is based on the conversion of the weakly fluorescent blue dye resazurin to strongly fluorescent pink resorufin in response to cellular metabolism. The intensity of pink fluorescence is directly proportional to the number of living cells, thus acting as a direct indicator of cell health. Resazurin (alamar blue) assay offers several advantages:

• Nontoxic and does not affect cell respiration or cell function in any way
• Highly sensitive, with the ability to detect as few as 50 cells in culture
• Easy to use with a simple workflow
• Water-soluble, thus eliminating the need for washing, fixing, or extraction steps 
• Flexible and can be used across a wide range of experiments 
• Compatible with other techniques and can be multiplexed to gather more information about the cytotoxicity mechanism
• Relatively inexpensive