Fig. 6.

Rescue of iron (III) citrate inhibition of PEI-mediated transient transfection. A series of 100 μL solutions were prepared containing iron (III) citrate at 1.5 mM and increasing concentrations of Na₄EDTA as indicated, and the solutions were incubated at room temperature overnight. CHO DXB11 cells were plated onto six well plates in DMEM with 10% FBS. The following day, the media were replaced with Medium A supplemented with 6 mM l-glutamine and Trace Elements A & B, and the iron (III) citrate/EDTA solutions were added, bringing the final iron (III) citrate concentration to 50 μM. In addition one well of cells with no iron (III) citrate was included as a control. The cells were transfected with pEGFP-N1 as detailed in “Materials and methods”. After 48 h, cells were trypsinized and analyzed by flow cytometry to determine the percentage of cells expressing GFP. In the well containing no iron (III) citrate, 64.6 ± 8.2% of the cells expressed GFP (data not shown). The experiment was performed three times