Folic Acid Linked Chondroitin Sulfate-Polyethyleneimine Copolymer Based Gene Delivery System

In our previous study, chondroitin sulfate-polyethylenimine copolymers (CP) have been synthesized and confirmed as potential gene delivery vectors. Efficient gene transfection is realized by chondroitin sulfate (ChS) that promotes CD44- mediated endocytosis and enhances the cellular uptake of CP/pDNA polyplexes besides clathrin-mediated endocytosis. In this study, the CP was functionalized with a folic acid (FA) molecule. This ancillary ligand allows polyplexes to bind with folate receptors (FR) in addition to the CD44 receptor. We conjugated FA-linked polyethylene glycol (FA-PEG) onto CP (FPCP) for tumor targeting and also synthesized mPEG-CP (MPCP) for comparison. The in vitro cell tests of polymer/pDNA polyplexes were done in FR-expressed U87 and FR-deficient A549 cells. The polymers exhibited less cytotoxicity than PEI-10K as well as PEI-25K against U87 and A549 cells. The transfection efficiency of FPCP/pDNA was higher than those of MPCP/pDNA and CP/pDNA. The cellular uptake pathways of FPCP/pDNA were tested in the cells in the presence of different endocytic chemical inhibitors. The CD44-, folate-, and caveolae-mediated pathways are involved in internalization of FPCP/pDNA. Recognition of FPCP to those receptors on the tumor surface is beneficial for enhanced cellular uptake of FPCP/pDNA, resulting in higher transgene expression than CP/pDNA and MPCP/pDNA.