Hi Marwan, Both assays will provide you with a good result. The XTT assay is very similar to the MTT assay therefore if you're familiar with the MTT assay that may be a good option to choose however according to the literature the major advantage of the resazurin reduction assay is that it is more sensitive than the tetrazolium assays. Therefore in terms of sensitivity, I would choose the resazurin assay. Attached is an article which contains the protocols and compares the use of the Resazurin and Tetrazolium Reduction Assays (XTT) https://www.ncbi.nlm.nih.gov/books/NBK144065/

Hope this helps

Hi Mary,

That is so brilliant. Many thanks for your comment. You are totally right, "the major advantage of the resazurin reduction assay is that it is more sensitive than the tetrazolium". That what I'm looking for. Based on that, I'm going to use resazurin.

Many thanks again for your help.

Marwan

Hi Marwan,

I totally agree with Mary! In my case, what made me decide for one or the other was not just the sensitivity, but also the wavelength where I measured the absorbance (since some of the molecules I was testing absorbed at the same wavelength than the one used for XTT).

Hi Maria,

Thanks very much for your comment. Do you mean the wavelength to measure of MTT different than that used for XTT?

Thanks

Hi again Marwan,

I meant for the case of XTT and resazurin. If I remember well, in XTT assays, viability was monitorized by following the absorbance change at 475 nm, while in resazurin assays, at 570-600 nm (at least with the assays we performed at that point!).

Hope it helped!

That is clear now.

Thanks Maria for your help.

Marwan

Hi Marwan,

One more good reason to use Resazurin instead of XTT is sensitivity of XTT to superoxide. In some cases if production of reactive oxygen spices increased (f.e. macrophages or other cells under stress) XTT without electron cariers mostly represent extracellular superoxide production.

During estimation of metabolic activity you could increase reproducibility and sensitivity of method by addition of small molecule electron carriers (menadion, phenazine methosulfate) as it done in commercial Resazurin based kits (f.e. Presto Blue).

Hope it could be helpfull

Thank you Daniil for this informative answer.

Also I would like to thank all others who rich my info.

Thanks again,

Marwan

Living cells maintain a reducing environment within their cytoplasm and mitochondria, in which resazurin (blue and non-fluorescent) is reduced by dehydrogenase enzymes to form the red fluorescent dye resorufin. The amount of resorufin can be monitored by measuring fluorescence or absorbance, which is proportional to the number of living cells in the sample. Depending on the cell types, the resazurin assay can be used to detect as few as 40 cells with reproducible and sensitive signal.

https://www.creative-bioarray.com/support/resazurin-cell-viability-assay.htm