I have been using BT2 (benzothiophene carboxylate) and even though literature suggests that it is highly soluble in dmso, it precipitates out once added in culture media at higher concentrations. What are the ways to get rid of this problem?
Sadly, you only really have three options: use more DMSO, use other excipients, or change the molecule. It IS soluble in DMSO, but once you put that into culture media (water), there's not much DMSO left, and aqueous solubility is a better predictor of how much will go into solution.
That' right, solubility in DMSO is irrelevant once you add the inhibitor to the aqueous solution. DMSO molecules will start interacting with water rendering them useless for inhibitor dissolution. As William says you need to add more DMSO (if possible).
Thank you for your suggestions, William and Omar. I have tried going upto 1000 fold concentrated stock so as to use a smaller amount for the working concentration that I am adding to the culture media. I have also tried to sterile filter it, in case there are certain impurities, and it did reduce the particles that I was seeing before but did not help much. It has a methyl group and is a benzothiophene carboxylate. Is there any suggestions as to what could be a better solvent for it apart from dmso? Should adding acid or base to the dmso solution work?
You're going in the wrong direction. Increasing the concentration of compound in DMSO means using less volume in your cell culture - this DECREASES the amount of DMSO around, and thus minimizes the solubility of the molecule. Similarly, filtering is simply removing compound from your solution, thus reducing the concentration beyond what you calculate.
What you need to do is figure out the LARGEST amount of DMSO your cells will tolerate, and then use the most DILUTE stock solution you can to supplement your cell culture media.
As for adjusting the pH: it might make it more soluble in DMSO, but you're adding it to culture media, which should be well buffered, and the little bit of acid or base in your DMSO should effectively cease to matter. And that is, again, your problem: your compound isn't soluble in culture media. Optimizing solubility in the DMSO stock isn't what you need to worry about.
As a further note: these compounds have been used in the literature a fair bit, on cell cultures. You might just look at what other researchers have done. And if that fails, why not just make the sodium salt of your compound? Then you might not even need DMSO, as the salt should be relatively water soluble all on its own.
We actually tried doing both. Using a higher stock and a lower stock such that the amount of the drug in dmso is relatively large. But it just turned the whole culture media cloudy. And the literature is not much help regarding this particular inhibitor. But thank you for your suggestions.
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