mtt

MTT is an acronym that can refer to multiple terms across different disciplines. The most widely used meaning in biology and biochemistry is the MTT assay, where MTT stands for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, a yellow tetrazolium salt used to assess cellular metabolic activity.

In living cells, viable cells with active metabolism reduce MTT to insoluble purple formazan crystals. The crystals are dissolved in a solvent such as DMSO or isopropanol, and the resulting solution is quantified by measuring absorbance with a spectrophotometer. The readout provides a proxy for cell viability, proliferation, or cytotoxicity, enabling comparisons across treatments or time points.

The assay is valued for its simplicity, speed, and cost-effectiveness, but it has limitations. It reflects metabolic activity rather than direct cell number, and certain compounds can interfere with reduction or formazan solubility. Additionally, for very low viability, extended incubation may introduce variability. Variants such as MTS, XTT, and WST use related tetrazolium salts to produce soluble formazans, improving ease of measurement in some contexts. Typical measurements are taken around 570 nm, often with a reference wavelength near 630 nm to account for background.

History and usage: the MTT assay was described in the 1980s and has become a standard tool in cell biology, pharmacology, and drug screening for evaluating cell viability and cytotoxic effects. While primarily associated with its role in laboratory assays, MTT can appear in other contexts as an acronym depending on the field.