I want to assess aspirin‘s effect on breast cancer cell proliferation in vitro. I dissolved aspirin in DMSO and added the solution to culture media (DMEM) which then became more acidic (pH aprox 7 when I use the maximum aspirin concentration). Could this acidification have an effect on cell proliferation? Should I make control experiments to assess pH effect on proliferation?I will be thankful for suggestions
Aiste,
First, I hope that you are not using aspirin tablets for your study. Aspirin tablets contain many compounds which are carriers and fillers. This may include cornstarch, dyes, methacrylate, cellulose, PEG, SLS, etc. All of these fillers will serve to obfuscate the results of a cell culture study, if you are actually interested in the effects of the active ingredient of aspirin, i.e., acetylsalicylic acid.
Second, I don't understand why you would need DMSO to dissolve acetylsalicylic acid. ASA is highly water-soluble and should not require a solvent like DMSO. I would avoid DMSO unless it is required.
Third, you should adjust the pH of your ASA stock solution or media supplemented with ASA to 7.3 or 7.4 rather than leaving it acidic. The ASA should not precipitate out unless you're using a very high concentration of ASA when you adjust the pH.
Finally, there is an immense published literature regarding the effects of ASA on cultured normal and tumor cells. You should review this carefully before starting your own experiments.
I agree with Bob's comments and would like to note that acetylsalicylic acid when dissolved in a buffer with robust buffering capacity and added to culture medium of most cell lines (versus the primary cells) works fine. As a control, I would include equal volume of buffer solution to culture medium of cells.
Thank you very much for the comments!
Robert Walter, I don't use tablets, I use ASA from Sigma. ASA is poorly soluble in water (10mg/ml at 37 deg C). But from published literature I know water pH must be adjusted to 7 to make a 0,5M stock solution in water. So I guess I cannot adjust the ASA stock solution in water to pH 7,3-7,4, because ASA will precipitate? Maybe I should try to adjust the media supplemented with ASA, but in this case I will have to do it for each ASA concentration.
Alternatively, other scientists use DMSO to prepare ASA stock. Maybe in this case I could adjust the stock pH ..
Labas Aiste,
You are correct about the low solubility of ASA in water, I was thinking of sodium salicylate which has a water solubility of 1000 g/L @ 20C. You could make your ASA stock in ethanol where it's solubility is 50 g/L or stay with DMSO. As you indicated, whatever solvent you choose, it is easier to adjust the pH to 7.3-7.4 in the stock solution before dilution, if possible. It is also best to store the stock solution in aliquots at -20C to prevent degradation. Aqueous solutions will degrade fairly quickly, but this is slowed in DMSO or ethanol. Also, consider that ASA converts readily to SA at pH > 7.4 . You may want to test the effects of SA in your system also to determine if any effects observed are due to ASA or SA.
Best of Luck
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