Poly(DMAEMA-NVP)-b-PEG-galactose as gene delivery vector for hepatocytes

A block;copolymer composed of cationic polymer and poly(ethylene glycol) (P EG) was used as a DNA carrier. Poly(2-(dimethylamino)ethyl methacrylate (DM AEMA)-co-N-vinyl-2-pyrrolidone (NVP)) having a terminal carboxylic group wa s synthesized by free radical polymerization using an initiator, 4,4'-azobi s(4-cyanovaleric acid). The terminal carboxylic acid was activated by N-hyd roxysuccinimide (NHS) with dicyclohexylcarbodiimide (DCC) and then conjugat ed with PEG-bis(amine). For specific gene targeting to asialoglycoprotein r eceptor of hepatocytes, a galactose moiety was incorporated into the PEG te rminal end of poly(DMAEMA-NVP)-b-PEG by reductive coupling using lactose an d sodium cyanoborohydride. RSV luciferase plasmid was used as a reporter ge ne, and in vitro gene transfection efficiency was measured in HepG2 human h epato carcinoma cells. Poly(DMAEMA-NVP)-b-PEG-galactose/DNA complexes forme d at 0.5-2 polymer/plasmid weight ratio had compacted structures around 200 nm particle size and exhibited slightly negative surface charge. These com plexes were coated with a cationic, pH sensitive, endosomolytic peptide, KA LA, to generate positively charged poly(DMAEMA-NVP)-b-PEG-galactose/DNA/KAL A complex particles. In the presence of serum proteins, both the PEG block and the galactose moiety of poly(DMAEMA-NVP)-b-PEG-galactose greatly enhanc ed the gene transfection efficiency, which was very close to that of Lipofe ctamine plus. Irrespective of the presence of serum proteins, as the KALA/D NA weight ratio increased, the transfection efficiency of poly(DMAEMA-NVP)- b-PEG-galactose was enhanced due to the pH dependent endosomal disruptive p roperty of KALA. This study demonstrates that sufficient transfection effic iency as high as that of commercial agent could be attained by judicious fo rmulation of molecular engineered poly(DMAEMA-NVP)-b-PEG-galactose in combi nation with an endosomolytic peptide, KALA.