Hello, I am working on pancreatic differentiation of hiPSCs. Since this requires daily medium change with freshly supplemented media, I have to use sterile filters nearly every day - this bothers me as filters are expensive and produce waste. I try to avoid sterile filter by keeping my drug stocks sterile, where possible. However, some drugs need to be weighed, which is done in a non-sterile cabinet. Other drugs are not particularly classified as "free od micro-organisms" by the manufacturer. I would really like to minimize sterile filtration. Do you have any experience with this issue? How do you doing practice this in your lab? Is sterile filtration really without any alternative? Are drugs dissolved in DMSO sterile per se (I read that some bacteria can grow in 100% DMSO)? I would like to hear your experiences with this issue and I would very happy about any recommendations :)
My usual practice is to sterile filter the supplements at a stock concentration and store in small aliquots at the appropriate storage temperature. When preparing medium I dilute to the needed working concentration. This way sterile filters are used once each time the supplement is reconstituted.
Thank you for your reply Jodi F Evans ! :)
Good idea which is working in some cases. But...
...what do you do if you have very expensive drugs. I usually lose 1 ml of the solution when I sterile filter.
With some drugs, loss of 1 ml can become quite expensive.
...what if you have small amounts of a drug which is solubulizable only in DMSO. Small amounts arent possile to filter and the preparation of higher diluted stocks to increase the volume is unsuitable since then the final DMSO concentration in the medium would be too high.
Any suggestions to solve that probelm?
Constantin Berger in the case of small amounts you can purchase sterile DMSO. Just reconstitute in the biosafety cabinet and then aliquot the stock into small microfuge tubes and store at -20. This way you are only thawing a small portion at a time.
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