Pluronic-grafted poly-(L)-lysine as a new synthetic gene carrier

Genes are attractive candidates as therapeutic agents, and the development of safe and effective gene carriers is essential for the success of human gene therapy. To develop a gene delivery vector that shows low cytotoxicity and high efficiency, we synthesized poly-L-lysine-g-pluronic by conjugating poly-L-lysine (PLL) to pluronic, which is partially functionalized with para-nitrophenyl carbonate groups, and evaluated for its efficiency as a possible nonviral gene carrier candidate. Structural analysis of synthesized polymer was performed by using 1H-NMR. Gel retardation assay, zeta potential and size measurement confirmed that the new gene carrier made a compact complex with plasmid DNA. pCMV-beta-gal was used as a reporter gene, and the in vitro transfection efficiency was measured in HeLa cells by using the o-nitrophenyl-beta-D-galactopyranoside assay. The highest transfection efficiency among those tested was achieved at the 1:1 weight ratio of polymer:DNA, and a 3-fold increase in transfection efficiency was achieved by treatment of a lysosomotropic agent, chloroquine. Compared with unmodified PLL, PLL-g-pluronic showed about 2-fold increase in transfection efficiency with similar cytotoxicity specifically at the 1:1 weight ratio of polymer:DNA.