By using ionic liquid 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) as reaction solvent and catalyst

and 1

1-carbonyldiimidazole as a coupling reagent

chitosan grafted with low molecular weight polyethylenimine (CS-g-PEI) was synthesized in a non-aqueous homogeneous solution.1H-NMR and FTIR experiments characterized the composition of copolymer CS-g-PEI and confirmed that the chitosan chains were successfully grated with polyethylenimine at a ratio of 42%.By using a coagulation method

CS-g-PEI/DNA complex nanoparticles were obtained

and their physicochemical properties were characterized with transmission electron microscopy (TEM)

dynamic light scattering (DLS) and Agarose gel electrophoresis assay.The transfection efficiency of CS-g-PEI was evaluated in Hep-2 cell lines with pGL3 as reporting genes.The gene expressing mediated by CS-g-PEI was 160 times higher than that by CS.MTT assays results showed that CS-g-PEI had low cytotoxicity in the range of the experimental dose.The results indicate that CS-g-PEI synthesized in ion liquid [BMIM]Cl has a very good potential as efficient and safe non-viral gene vectors.