The best way is to do a stain for live/dead and sort the live cells using FACS. You could also do a limiting dilution series and plate out ~1 cell per well in a series of 96 well plates and wait and see which wells end up with proliferating cells.

Thank you for the reply !

Hi,

for plasmid transfection of my suspension cells I use a zero charged transfection reagent called Viromer RED/YELLOW (from Lipocalyx).

In general all commercial transfection reagents are positive in charge which will lead to aggregation of cells when used in suspension cultures. This will decrease transfection efficiency because not every single cell will be reached.

By using Viromers I get a higher transection efficiency compared to standard reagents.