High-efficiency loading, transfection, and fusion of cells by electroporation in two-phase polymer systems

A method to concentrate drugs, DNA, or other materials with target cells in two-phase polymer systems for high-efficiency electroloading is described. The two-phase polymer system is utilized for cell and loading material selection, as well as for cell aggregation before electrofusion. The phase mixing of several water-soluble polymers is characterized, and the polyethylene glycol-Dextran (PEG m.w. 8,000 + Dextran m.w. 71,000) mixture is selected to illustrate the advantage of the two-phase systems. Fluorescently labeled Dextran or DNA is loaded into Chinese hamster ovary (CHO) and JTL cells, using electroporation in either the two-phase polymer system or the conventional single-phase suspension. The loading efficiency is 4 to 30 times higher for the two-phase system, with the best advantage at lower applied field range. Transfections of CHO, COS, Melan C, and JTL lymphoid cells using pSV-beta-galactosidase (for CHO and COS), pBK-RSV-tyrosinase, and pCP4-fucosidase plasmids, respectively, by electroporation in the two-phase polymer system and the conventional single-phase electroporation method, are compared. The former method is far superior to the latter in terms of efficiency. The threshold and optimal field strengths for the former are significantly lower than those for the latter method, so the former method is more favorable in terms of equipment requirement and safety. Electrofusion efficiency in the two-phase system is comparable to that in polyethylene glycol suspension alone and is a significant improvement from the conventional electrofusion method with dielectrophoresis. The two-phase polymer method is, therefore, a valuable technique for gene delivery to a limited cell source, as in ex vivo gene therapy.