Statistical experimental designs to optimize the transient transfection of HEK 293T cells and determine a transfer criterion from adherent cells to larger-scale cell suspension cultures

The transient transfection of mammalian cells is a rapid and versatile platform for the manufacture of recombinant proteins, but industrial processes depend on reliable scalability and efficient conversion from adherent to suspension cell cultures. Here we describe the optimized transfection of HEK 293T cells in both culture formats. DMEM was the best transfection medium for adherent HEK 293T cells, so we determined the kinetics of linear polyethyleneimine (LPEI) polyplex formation with plasmid DNA (pDNA) and subsequent cellular uptake. Statistical experimental designs revealed optimal transfection efficiency using 0.7 pg pDNA and 4.5 pg LPEI per cell. We used the amount of pDNA and LPEI per cell as the transfer criterion for HEK 293T/17 SF cell suspension cultures in FreeStyle 293 medium and confirmed optimal transfection at 1.1 pg pDNA and 6.6 pg LPEI per cell. We observed a strong correlation between polyplex size, transfection efficiency and post-transfection cell viability. Suspension cell transfection could be scaled to a 100-mL working volume without loss of efficiency. We conclude that pg pDNA and pg LPEI per cell is a suitable transfer criterion allowing the optimization of transient transfection using statistical experimental designs, thus minimizing the amount of pDNA and LPEI used without sacrificing transfection efficiency.