Dear all,
I prepared my cell media (EMEM+10%FBS) and another cell media (EMEM+2%FBS+1% Pen/Strep). Incubate the aliquot of the media in 37°C for a few days and saw these. They are not moving and there was no color change in the media. Since there were no cells in the flask so if these weren't cell debris, I wonder if this is debris/aggregates from the serum? I also have done sterility check on the serum and no changes observed to indicate contamination.
Thanks.
Hello Nurul Kamal
Yes, you could be right. This could be some precipitate from the serum.
The following possibilities could be considered.
1. Serum is kept cold throughout all collection and manufacturing processes, during which fibrinogen is in a dissolved state. However, after filtration processes, serum fibrinogen tends to aggregate and precipitate.
2. Calcium phosphate is another common precipitate that can lead to turbidity. This phenomenon is particularly noticeable when the serum is incubated at 37°C and is sometimes mistakenly regarded as microbial contamination.
3. There are other components in serum, such as cholesterol, fatty acid esters and some proteins that can also form precipitates.
All these precipitates have no influence on cultured cells. But when it becomes a big concern, it can be removed by performing a filtration process after being added to the cell culture medium.
You may avoid such a situation by thawing the serum in a gradual way. The frozen serum (usually at -20°C) must be thawed mildly at 4°C. Please avoid directly thawing at room temperature. During the thawing process, shake the bottle evenly and gently at intervals. Prepare aliquots of serum and store at -20°C.
You may notice formation of precipitates during heat inactivation, incubation at 37°C, repeated freeze-thaw cycles, long-term storage at 2-8°C, and placing serum at room temperature for prolonged periods of time.
Best.
Hi Malcolm Nobre
Thank you very much for the informative answer! I was wondering if the aliquots of serum (we usually aliquot in 50ml tubes) that were kept in -20 are thawed at room temperature before adding them to media for complete media prep is the correct and only way? Thanks.
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