I am transiently transfecting mesenchymal stem cells with a mammalian plasmid-based expression vector that does not contain any mammalian selection marker and also the gene of interest will be cloned into the plasmid without co-expression of any reporter fusion gene.
I would like to know if selection or expression testing is good practice and mainstream in plasmid-based transient transfection of mammalian cells.
As you know, in bacterial transformation selection against non-transformed bacterial cells is mandatory so that transformed bacterial cells could be enriched for. I wonder whether this is also mandatory in plasmid-based transient transfection of mammalian cells. If not, then would not non-transfected cells outgrow transfected ones and affect downstream cell-based functional assays? Also, do I have to measure transfection efficiency beforehand? Also, how long can a mammalian cell retain a plasmid without a mammalian selection marker? Thank you.