alamarBlue

AlamarBlue is a cell viability and proliferation indicator based on resazurin, a blue nonfluorescent dye that is reduced to resorufin, a pink fluorescent compound, by metabolically active cells. The solution is sold as a ready-to-use reagent and is widely used as a non-radioactive alternative to MTT, XTT and similar assays.

Mechanism: In living cells, metabolic activity provides reducing equivalents (NADH, NADPH) that reduce resazurin to resorufin via cellular reductases, sometimes further to non-fluorescent hydroresorufin; the rate of reduction correlates with cell number and viability.

Readouts: The reaction produces a color change from blue to pink; fluorescence can be measured with excitation around 560-570 nm and emission around 590 nm; absorbance readings can be done at 570 nm and 600 nm. Plate readers or microplate readers can be used.

Applications: Used in mammalian cell culture, bacteria, yeast, and other organisms to assess viability, cytotoxicity, or proliferation. Suitable for endpoint assays and, in some protocols, for non-destructive, longitudinal monitoring of cells in culture.

Advantages and considerations: AlamarBlue is non-toxic and allows continuous monitoring of cultures; simple to use and compatible with many cell types. However, readings can be affected by compounds that alter redox state, high background color, or strong reducing media; optimization of dye concentration and incubation time is recommended for each system.