LACTOSE-POLY(ETHYLENE GLYCOL)-GRAFTED POLY-L-LYSINE AS HEPATOMA CELL-TARGETED GENE CARRIER

To investigate the delivery of DNA into cells, lactose-poly(ethylene g lycol)-grafted poly-L-lysine (Lac-PEG-PLL) polymers were synthesized a s polymeric gene carriers. The new synthetic carriers, varying the sub stitution ratio of lactose-poly(ethylene glycol) (lactose-PEG), were c haracterized by NMR spectroscopy and size-exclusion chromatography. El ectrophoretic mobility assay confirmed that the new gene carrier makes a complex with plasmid DNA. The attached poly(ethylene glycol) gives better solubility properties to gene/carrier complex. Transfection exp eriments showed that Lac-PEG-PLL efficiently delivers DNA to a hepatom a cell line in vitro; the best efficiency was achieved at a 1:3 weight ratio of DNA to carrier. As the lactose-PEG substitution content incr eased up to 30%, the transfection efficiency increased, which demonstr ates that the lactose serves as a targeting moiety. No considerable cy totoxicity was observed due to Lac-PEC-PLL or its complex with DNA wit hin the concentration range for this experiment. The use of chloroquin e increased transfection efficiency that indicates the involvement of hydrolytic degradation of the system in lysosome. It is likely that pl asmid DNA/Lac-PEG-PLL complexes enter the cells through a receptor-med iated endocytosis mechanism. These results show that Lac-PEG-PLL can f orm a complex with plasmid DNA and serve as an efficient gene delivery carrier with lower cytotoxicity compared to that of poly-L-lysine. Th erefore, it is expected that our Lac-PEG-PLL carrier can be used as an in vivo gene delivery vector.