Objective:To enhance the transfection efficiency and to reduce the toxicity of the polyethyleneimine(PEI)

we synthesized PEI derivatives and tested their toxicity and transfection efficiency in different cell lines. Methods:We first developed PEGylated PEI to decrease the toxicity of PEI

and then we conjugated folate on the distal end of the novel PEG-PEI to introduce specificity for special tumor cells.Following we checked the characterization of polymers and tested their toxicity and transfection efficiency in three cell lines with MTT assay

EGFP/fluorescent image

reporter assay and flow cytometry. Results:These copolymers effectively condensed plasmid DNA(pDNA) into nanoparticles with positive surface charge under a sui table N/P ratio.These derivatives reduced the cytotoxicity of PEI 25ku in different cell lines(i.e.

HEK 293T

glioma C6 and hepatoma HepG2 cells).More importantly

compared with PEI 25ku

the transfection efficiency was increased. Reporter assay and flow cytometry showed that FA-PEG-PEI/pDNA complexes exhibited higher transgene activity than that of PEG-PEI/pDNA or PEI/pDNA in folate-receptor(FR) positive(HEK 293T and C6) cells but not FR-negative(HepG2) cells. Conclusion:These results indicated that FA-PEG-PEI might be a promising candidate for gene delivery with the characteristic of good biocompatibility and relatively high gene transfection efficiency.