BIOSYNTH Molecule of the Month: MTT Traditional Tetrazolium Salt

BIOSYNTH Molecule of the Month: MTT Traditional Tetrazolium Salt

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Microbiology and organic fine biochemical CDMO and specialist supplier, BIOSYNTH AG, has more than 100, 000 substances and molecular entities in its product portfolio. Each of them has its own particular applications and story to tell.

Here is an example of the molecular entities that BIOSYNTH regularly features on its website every week. This month we are focusing on the traditional tetrazolium salt MTT Thiazolyl Blue Tetrazolium Bromide which used to be the most widely used tetrazolium salt for cell-based assays but is now finding new applications.

MTT: description

The yellowish mono-tetrazolium salt: thiazolyl blue tetrazolium bromide (BIOSYNTH catalog number T-3450) is also known as Methylthiazolyldiphenyl-tetrazolium (MTT) bromide; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide; 2-(4,5-Dimethyl-2-thia-zolyl)-3,5-diphenyl-2H-tetrazolium bromide.

MTT can be used in cell viability assays because it may readily enter cells and is then reduced exclusively in metabolically active cells to form the purple MTT-formazan. The responsible cellular enzymes involved are NAD(P)H-dependent oxidoreductases and dehydrogenases as well as succinate dehydrogenase. NADH, NADPH and succinate serve as electron donors.

The insoluble MTT-formazan precipitates inside the cells, but small traces may also be detectable in the culture medium. Stockert et al. 2012 investigated the localization in more detail: they concluded that MTT formazan granules do not co-localize with mitochondria or lysosomes of living HeLa cell. However, the dye accumulated in lipid droplets that were artificially introduced in their experiments.

BIOSYNTH can provide a full range of formazan dyes, both traditional and new ones, via its web store.

MTT applications

In standard cell viability assays, organic solvents such as isopropanol or DMSO or detergents such as SDS, Triton® X-100 or combinations of detergents and solvents were used in order to solubilize the formazan to make it accessible for spectrophotometric measurements.

Since classic formazan dyes such as MTT are water-insoluble, they need to be solubilized in an additional step of the experiment procedure. Water Soluble Tetrazolium salts (WST) are a newer generation of tetrazolium salts that have been developed in order to avoid the additional solubilization steps. Today, quantification of cell proliferation, cell viability tests and cytotoxicity assays are routinely performed using WST-1 and WST-8. These materials are known to be more sensitive than the traditional tetrazolium salts NBT, XTT and MTT.

However, MTT tetrazolium salt can also be applied in different experiments, such as procedures to measure fungal cell density (Freimoser et al. 1999) and to assay protozoa (Dias et al. 1999).

An emerging use for MTT in material sciences is as a potential corrosion inhibitor for copper in seawater to replace more corrosive substance.

During 2018, studies by Fern et al. investigated the anticorrosion benefits of MTT for copper in artificial seawater (3% NaCl). This is an urgent need, considering the toxicity of conventionally used copper corrosion inhibitors.


  1. Freimoser, F.M. et al. (1999) Appl. Environ. Microbiol. 65(8), 3727-3729: The MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazo-lium Bromide] Assay Is a Fast and Reliable Method for Colorimetric Determination of Fun-gal Cell Densities.
  2. Dias, N. et al. (1999) J. Basic Microbiol. 39(2), 103-108: Miniaturization and application of the MTT assay to evaluate metabolic activity of protozoa in the presence of toxicants.
  3. Stockert, J.C. et al. (2012) Acta Histochem. 114(8), 785-96: MTT assay for cell viability: Intracellular localization of the formazan product is in lipid droplets.
  4. Li Feng et al. (2018) Materials 11(6), 1042: Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution.


Click on BIOSYNTH Molecule of the Month: MTT for more information.
Click on BIOSYNTH to contact the company directly.
Click on T-3450 Thiazolyl Blue Tetrazolium Bromide for further information.
Click on MTT as copper corrosion inhibitor for further information.

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