Why do you add fresh MEM supplemented with 2% FBS to the cells...

Thank you for your question. Yes, you are right: We reduce the FBS content to slow down the cell growth. If the RK13 cells that we use for transfection reach a confluency level which is too high, the cells would start being syncytial on its own. By reducing the FBS content we exclude that syncytia formation is induced by the confluency level. In addition, we control this by using a negative control (cells which are only transfected with the empty vector).