XTT (sodium salt)

XTT (sodium salt) (CAS No.: 111072-31-2) is a widely utilized tetrazolium-based colorimetric reagent for the quantitative assessment of cell viability, proliferation, and metabolic activity in biological research. Functioning as a redox-sensitive indicator, XTT is reduced by mitochondrial dehydrogenases and other intracellular oxidoreductases in metabolically active cells to yield a water-soluble, orange-colored formazan product, enabling direct spectrophotometric measurement without the need for additional solubilization steps. This biochemical conversion reflects cellular redox potential and mitochondrial function, making XTT particularly valuable for monitoring cell health and metabolic competence in vitro. As a member of the tetrazolium salt family, it is broadly applied in assays evaluating cytotoxicity, cell proliferation, and drug sensitivity, especially in high-throughput screening workflows for compound libraries. The assay readout is typically proportional to the number of viable cells over a dynamic range that can extend from low micromolar to higher concentrations depending on experimental conditions and cell type. XTT-based assays are commonly implemented in cultured mammalian cells and other cellular systems, where reagent concentrations and incubation times are optimized according to specific experimental designs, supporting applications in pharmacological profiling, toxicity evaluation, and mechanistic studies of cellular metabolism.