Is this contamination or cell clumping? its a flask of hek 293 cells 24hrs after passaging. no clour change or turbidity of media.
Have you checked your cells under the 40X objective?
If there is no visible contamination then
1. try changing the stock. (HEK doesn't look like this)
2. Could be cell clumping (In that case, this batch will not provide reliable results).
3. Try changing FBS stock (GIBCO is preferred).
Sourav Ghosh I looked at the cells under 40X and didnt see anything unexpected. the cells all look normal excpet for these rare lumps.
However im somewhat new to cell culture, so what exactly should i be looking for?
Can i ask how FBS could be the issue? Do you think it could be introducing a contaminant?
Sometimes i do notice after trypsinising cells that there are some small clumps that do not break apart fully with pipette mixing before adding to new flasks, could these lumps be part of the monolayer of the previous passage?
Damien Collins Do you resuspend the cells very gently at the time of passage? that may cause those clumps to form, although I would suggest changing your stocks, take out some old stocks.
Hello,
When do you passage your cells? Subculture the cells when they are 80% confluent. Subculturing over confluent cells causes clumping because the dead cells present in culture release DNA which being sticky causes cells to aggregate into clumps. Cell clumping can cause cell death.
Also, do not over trypsinize the cells. This could damage cell membrane and eventually kill the cells. Again it could cause clumping for reason mentioned above.
Trypsin exposure should be for a maximum of 5 minutes. If you still observe clumping after trypsinizing 80% confluent cells then you would need to use a fresh lot of trypsin.
Best.
Sourav Ghosh no i pipette mix fast over 10 times to try and get a homogenous mix but occasionally i see a small clump that will not break no matter how much i pipette mix.
Just to check, it doesn't look like fungal or bacterial contamination anyway??
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