Resazurin

Resazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide) is a blue dye, itself weakly fluorescent until it is irreversibly reduced to the pink colored and highly red fluorescent resorufin. It is used as an oxidation-reduction indicator in cell viability assays for both aerobic and anaerobic respiration. Usually it is available commercially as the sodium salt.Resazurin as a colorimetric assay for cell viabilityResazurin used as a fluorescent assay for cell viability - Resazurin does not fluoresce when exposed to green lightResazurin as a fluorescent assay for cell viability - Resorufin fluoresces when exposed to green light Resazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide) is a blue dye, itself weakly fluorescent until it is irreversibly reduced to the pink colored and highly red fluorescent resorufin. It is used as an oxidation-reduction indicator in cell viability assays for both aerobic and anaerobic respiration. Usually it is available commercially as the sodium salt. Resazurin solution has one of the highest values known of Kreft's dichromaticity index. This means that it has a large change in perceived color hue when the thickness or concentration of observed sample increases or decreases. Resazurin was first used to quantify bacterial content in milk by Pesch and Simmert in 1929.It can be used to detect the presence of viable cells in mammalian cell cultures.It was introduced commercially initially under Alamar Blue trademark (Trek Diagnostic Systems, Inc), and now also available under other names such as AB assay, Vybrant (Molecular Probes) and UptiBlue (Interchim). Resazurin based assays show excellent correlation to reference viability assays such as formazan-based assays (MTT/XTT) and tritiated thymidine based techniques. The low toxicity makes it suitable for longer studies, and it has been applied for animal cells, bacteria, and fungi for cell culture assays such as cell counting, cell survival, and cell proliferation.. To take the place of a standard live/dead assay, resazurin also be multiplexed with chemiluminescent assays, such as cytokine assays, caspase assays to measure apoptosis, or reporter assays to measure a gene or a protein expression. The irreversible reaction of resazurin to resorufin is proportional to aerobic respiration. Resazurin is effectively reduced in mitochondria, making it useful also to assess mitochondrial metabolic activity. Usually, in the presence of NADPH dehydrogenase or NADH dehydrogenase as the enzyme, NADPH or NADH is the reductant that converts resazurin to resorufin. Hence the resazurin/diaphorase/NADPH system can be used to detect NADH, NADPH, or diaphorase level, and any biochemical or enzyme activity that is involved in a biochemical reaction generating NADH or NADPH. Resazurin can be used to assay L-Glutamate, achieving a sensitivity of 2.0 pmol per well in a 96 well plate.