Receptor-mediated gene delivery by folate-poly(ethylene glycol)-grafted-trimethyl chitosan in vitro

Folate-poly(ethylene glycol)-grafted-trimethyl chitosan (F-PEG-g-TMC) and methoxypolyethylene glycol-grafted-trimethyl chitosan (mPEG-g-TMC)/pDNA complexes were prepared and characterized concerning physicochemical properties including cytotoxicity, condensation efficiency, particle size, and zeta potential. Furthermore, cellular uptake and transfection efficiency of the complexes were evaluated in vitro and compared with that of folate-trimethyl chitosan (folate-TMC) synthesized by our group to elucidate the effect of PEGylation. The cellular uptake of the F-PEG-g-TMC/pDNA with a copolymer nitrogen-to-DNA phosphate ratio (N/P ratio) of 20 in KB cells was specifically increased up to 1.68-fold compared with that of the mPEG-g-TMC/pDNA (N/P ratio 20) resulting in 1.5-fold and 1.4-fold increased transfection efficiency in KB cells and SKOV3 cells (folate receptor-overexpressing cell lines), respectively. The intracellular uptake and transfection efficiency of the F-PEG-g-TMC/pDNA were significantly enhanced relative to the folate-TMC/pDNA in folate receptor-overexpressing cells due to stabilizing effect of PEGylation. Subcellular localization of the complexes in the process of intracellular transportation was observed by confocal laser scanning microscopy suggesting quicker association of the F-PEG-g-TMC/pDNA. In conclusion, the F-PEG-g-TMC/pDNA complexes are potential vehicles for improving the transfection efficiency and specificity of gene.