These dots are extremely small and do not move, however upon DAPI staining, I observe a lot of DAPI spots surrounding the nucleus and cells. Can it be mycoplasma contamination? I do not observe any such dots in the control well (only OptiMEM added, no transfection reagent).
hi Harsh Oza
This is quite normal during lipofectamine-mediated plasmid transfection.
Can you post the phase contrast image? It will be helpful for the others in the forum to give a specific comment.
it is normal for the CaCl2 transfection. I have not noticed this lipofectamine transfection.
I have noticed these dots post-lipofectamine transfection as well, but do not have an answer on their origin.
There are several easy tests for mycoplasma (that should be performed regularly, in addition to regular STR testing). Check out these resources for tests amenable to your resources:
https://journals.sagepub.com/eprint/2KZ6S8B9YEIPRJZNKJRT/full#articleShareContainer
https://www.nature.com/articles/nprot.2010.43
This is totally natural. The transfection reagent interacts with the DNA to produce a complex/precipitate usually through cationic interaction with negatively charged DNA but the mechanism can vary. This can be observed as small dots on the outer cell membrane. Over time these dots/complexes disappear (4hrs+) as they are taken up by the cells.
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