I did a PEI transfection in 6-well plate (non-binding), 2mL of CHO suspension cells at 1M/mL. The transfection was stopped after 3 hours. I checked the cells the next day with FACS and microscope and the they looked good and around 50% of them were transfected. A day later, I checked again but they were dying and the media turned bright pink. The control/non-transfected wells were fine. Can anyone suggest some possibilities of why the cells died so drastically and the media turned pink?
There are several possibilities. Did you look to see if your transfected cells were contaminated? Did your non-transfected cells receive the PEI reagent? Is your transfected protein toxic when over expressed?
if your non-transfected cells are okay, I agree with Michael, only 2 possibilities:
1) the PEI is too toxic for these cells (which cells do you have? did you try changing the medium after transfection?)
2) the overexpressed protein induces something affecting the cells.
I agree with Michael as well. Pink and cloudy is usually an indicator of bacterial contamination. A quick microscope check may confirm this. Good luck!
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