TTC test

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The TTC or formazan test ( English : TTC assay or formazan assay ) is used in cell biology to determine the viability or metabolic activity of cells (a cell line or tissue ) ( vital staining ). The TTC test is also suitable for determining the sensitivity of bacteria to antibiotics .

The test is based on a color change of the triphenyltetrazolium chloride (TTC) due to the reaction with living cells.

method

In the test, the colorless substance triphenyltetrazolium chloride is reduced to the water-insoluble red dye 1,3,5-triphenylformazan (formazan) by living cells taking up two electrons (e - ) and one proton (H + ) .

Reduction of triphenyltetrazolium chloride via a tetrazolium radical to formazan

This reaction is a redox reaction that is induced by various dehydrogenases in the cell . These enzymes quickly become inactive after the cell dies, which means that the test is only positive for living cells. It is also suitable for distinguishing between intact and necrotic sites in tissue samples.

In cell culture, the TTC test can also be used indirectly to determine different cell numbers and cell proliferation - but only if cells from the same lineage and in the same stimulation state are observed.

Other uses

The TTC test is also suitable for stimulation and cytotoxicity studies in mammalian cell lines; However, the informative value of this method with regard to proliferation is low because differences in the metabolic activity of the cells have a very large influence on the end result. The determination of the proliferation should therefore also be carried out simultaneously using other proliferation assays (e.g. thymidine assay) in order to be able to compare the results of the various methods with one another.

A more advanced version of the TTC assay is the MTT (and XTT) assay .

literature

  • Roberts, LW: Survey of factors responsible for reduction of 2,3,5-triphenyltetrazolium chloride in plant meristems . In: Science.  1951 Jun 15; 113 (2946): 692-693.
  • Mohammadzadeh, A., Farnia, P., Ghazvini, K., Behdani, M., Rashed, T., Ghanaat, J .: Rapid and low-cost colorimetric method using 2,3,5-triphenyltetrazolium chloride for detection of multidrug- resistant Mycobacterium tuberculosis . In: J. Med. Microbiol.  2006 Dec; 55 (Pt 12): 1657-1659.