The use of low-molecular-weight PEIs as gene carriers in the monkey fibroblastoma and rabbit smooth muscle cell cultures

Background Polyethylenimines (PEIs) and cationic polymers have been used successfully in gene delivery. In earlier reports, only large PEIs (MW > 10 000) have shown significant transfection efficiency. In the present study, the roles of small PEIs (MW 700 and 2000) were studied as additional compounds to see if they can improve gene delivery with cationic liposomes. Methods The TKBPVlacZ expression plasmid was transfected in the CV1-P (monkey fibroblastoma) and SMC (rabbit smooth muscle) cell lines using various combinations of PEIs (MW 700, 2000, and 25 000) and Dosper liposomes. The transfection efficiency was determined with the fluorometric ONPG (o-nitrophenol-beta-D-galactopyranoside) assay and histochemical X-gal staining. The toxicity of the transfection reagents was estimated by the MTT [3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl tetrazolium bromide] assay. Results Transfection of TKBPVlacZ plasmid by the small PEIs (MW 700 and 2000) combined with Dosper liposomes was associated with high expression of the lacZ reporter gene in the CV1-P and SMC cell lines. The transfection efficiencies of the low-molecular-weight PEI/liposome combinations were several fold higher than those of PEIs or liposomes alone. PEI/liposome combinations had no toxicity on the cell lines tested. Conclusions The low-molecular-weight PEIs could be used successfully for gene delivery when combined with the cationic liposomes, resulting in a synergistic increase of the transfection efficiency in both cell lines studied. Copyright (C) 2002 John Wiley Sons, Ltd.