1．What is Thiazole Blue (MTT)

Thiazole Blue, CAS number 298-93-1, molecular formula C₁₈H₁₆BrN₅S, is a yellow or orange-yellow powder, melting point: 195°C (decomposition). Slightly soluble in methanol, but hardly soluble in water or ethanol. It can't be completely dissolved with ether, acetone or ethyl acetate. Dissolved in DMSO. It is often formulated as a 5mg/ml stock solution.

2．Detection principle of thiazole blue (MTT) colorimetric method

Thiazole Blue (MTT) colorimetry is a method for detecting cell survival and growth. The principle of the MTT experiment is that the succinate dehydrogenase in the mitochondria of living cells can reduce the exogenous MTT to water-insoluble blue-purple crystal formazan (Formazan) and deposit it in the cells, while dead cells have no such function. Dimethyl sulfoxide (DMSO) can dissolve formazan in cells, and its light absorption value is measured at 490nm wavelength with an enzyme-linked immunoassay, which can indirectly reflect the number of living cells. The amount of MTT crystal formation in a certain cell number range is proportional to the cell number. According to the measured absorbance value (OD value), the number of living cells is judged. The larger the OD value, the stronger the cell activity (if the drug toxicity is measured, the lower the drug toxicity is). This method has been widely used in the activity detection of some biologically active factors, large-scale anti-tumor drug screening, cytotoxicity test and tumor radiosensitivity determination. It is characterized by high sensitivity and economy.

3．Application of Thiazole Blue (MTT)

MTT is usually used for cell proliferation, cell viability determination, and drug (including other treatments such as radiation exposure) to determine the toxicity of cultured cells in vitro.

4. The advantages and disadvantages of thiazole blue (MTT) colorimetry

 (1)Advantages: It is simple, fast, economical, and does not use isotopes.

 (2)Disadvantages: The formazan product produced by the reduction of MTT is insoluble in water and needs to be dissolved before detection. Increasing the workload will also affect the accuracy of the experimental results, and the organic solvent that dissolves formazan is also harmful to the health of the experimenters.

5.Precautions for thiazole blue (MTT)

(1) In the process of preparation and storage, the container is best wrapped with aluminum foil.

(2) The prepared MTT needs to be sterile, and MTT is very sensitive to bacteria.

(3) MTT is generally best to be prepared immediately. It is effective within two weeks after filtration at 4°C and protected from light, or it is formulated as 5mg/ml and stored at -20°C for long-term storage. Avoid repeated freezing and thawing. It is best to pack in small doses. Wrap it in a light-proof bag or black paper or tin foil to avoid light decomposition. When MTT becomes gray-green, it can never be used again.

(4) MTT is carcinogenic, use it carefully, and if possible, it is best to wear transparent film gloves. Generally, the MTT concentration in this method is 5 mg/ml. Therefore, you can weigh MTT 0.5g, dissolve it in 100 mL phosphate buffer (PBS) or phenol red-free medium, filter it with a 0.22μm microporous membrane to remove bacteria in the solution, store it at 4℃ and avoid light can. In the process of preparation and storage, the container is best wrapped with aluminum foil.