Homogeneous Graft of Chitosan with Polyethylenimine in Ion Liquid and Its Application in Gene Delivery

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. H-1-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.