Hello. I am trying to test my designed peptide binding towards MDA-MB-231 and MCF-7 cell lines. However, I first need to dissolved my peptides as they are in lyophilized form.
The suggestion from my peptide synthesis service provider is to use 1 part ACN: 3 part water, which definitely is toxic to the cell lines. Alternatively, I can use DMSO as my solvent.
From my reading, concentration of >1% DMSO in my media would be cytotoxic to MDA-MB-231. I am now trying to run MTT assay to test the concentration that would be minimally cytotoxic to my cells. I am testing 1%, 0.5%, 0.25 %, 0.1% (v/v) DMSO in media.
However, I am curious does the concentration of this DMSO affect my peptide solubility in the solution? If let say I want to prepare 10uM concentration of my peptide, then if I am to prepare it by dissolving it in 100% DMSO, when i dilute the DMSO to 1%, wouldn't that also dilute my peptide? Or do I need to prepare higher than usual?
My concern is that my peptide sample is limited (10mg) per peptide so I don't want to use up whole sample as I have another assay to run.
Any advise on this? Thanks for the help!
Hello Alif Ismail
In order to avoid toxic effects of DMSO on cells, DMSO concentration should be ≤ 0.1% when it is finally added to the culture.
Suppose your working concentration that is finally added to the culture is 10uM, then you will have to prepare a stock of 10mM of your peptide dissolved in 100% DMSO. When you dilute your stock (10mM) 1000 times with culture media, you will obtain 10uM of working solution. At the same time, 100% DMSO will also get diluted 1000 times giving a concentration of 0.1% DMSO. So, you will have 10uM of peptide working solution in 0.1% DMSO, which you will finally add to the cells.
If you have limited peptide sample, then you will have to run a small experiment to determine the level at which DMSO toxicity begins. Some cell lines can tolerate up to 1% DMSO without severe cytotoxicity. If MDA-MB-231 and MCF-7 cell lines can tolerate up to 1% DMSO, you may be able to save peptide sample for another assay because you will now be able to make a stock peptide solution of less than 10mM.
Best.
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