I have done cell-culture test for Fe-based MG (FeCrMoCB). The results showed very high cell viability % (300%). So, I tried the samples in culture medium without cells, and the MTT gave purple color. Do anyone has explanation
It could be possible. Usually when we use MTT assay, after the treatment with MTT for 2-4 hours, we remove the medium, and dissolve formed formazan crystals in DMSO. If the medium changes its color due to some substances in it, we wash the cells once or twice with PBS before dissolving crystals in DMSO.
Thank you @Vilma Petrikaite for your answer, but is it correct to put my sample inside the 24-well plate and do the MTT test?
Another question, you wash the cells after you remove the MTT solution and before adding DMSO?
Again thanks a lot for your response
The principle of the MTT assay is reduction of the tetrazole to the purple formazan. The assumption is, of course, that it's cellular metabolic processes (and NADH in particular) that is responsible (for more info see: https://www.ncbi.nlm.nih.gov/books/NBK144065/).
However, it's entirely possible for other reducing agents to react with the tetrazole giving a false positive signal, which is why in all of these types of viability assays positive and negative controls are crucial.
I'm not familiar with FeCrMoCB, but a number of metals and metal ions are redox active, so it's not too surprising that you see such an effect.
You may consider trying a different assay, such as resazurin (aka AlamarBlue) which will have a different reduction potential.
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