Folate-conjugated chitosan-poly(ethylenimine) copolymer as an efficient and safe vector for gene delivery in cancer cells.

Folic acid (FA) has high affinity to folate receptors (FRs), which have three isoforms: FRα, FRβ and FRγ. Among them, FRα is a tumor specific receptor, as it is frequently over-expressed in diverse malignancies but not in normal tissues. In this study, we have conjugated FA to a chitosan-poly(ethylenimine) copolymer, and have confirmed the low cytotoxicity of the product (namely "CP1.3K-FA") in cancer cells. The transfection efficiency of CP1.3K-FA has been shown by the EGFP transfection assay to be higher than that of the unmodified chitosan-poly(ethylenimine) copolymer under optimal conditions. Results of the luciferase activity assay have also indicated that the transfection efficiency of CP1.3K-FA is comparable to that of Fugene HD in B16 and U87 cells. Our results have suggested that CP1.3K-FA warrants further development as a vector for gene delivery in cancer cells.