title: Degradable polyethylenimine-alt-poly(ethylene glycol) copolymers as novel gene carriers.
abstract: An ideal gene carrier requires both safety and transfection efficiency. Polyethylenimine (PEI) is a well-known cationic polymer, which has high transfection efficiency owing to its buffering capacity. But it has been reported that PEI is cytotoxic in many cell lines and non-degradable. In this study, we synthesized degradable PEI-alt-poly(ethylene glycol) (PEG) copolymers using Michael-type addition reactions as a new gene carrier and characterized them. These copolymers were complexed with plasmid DNA and the resulting complexes were characterized by dynamic light scattering, gel retardation and atomic force microscopy to determine particle sizes, complex formation and complex shape, respectively. Cytotoxicity and transfection efficiency of the copolymers were also checked in cultured HeLa human cervix epithelial carcinoma cells, HepG2 human hepatoblastoma cell line and MG63 human osteosarcoma cells. PEG to PEI ratio in the copolymers was near 1 and the molecular weight of the copolymer ranged from around 8000 to 12,900. These copolymers degraded rapidly at 37 degrees C in 0.1 M phosphate buffered saline (PBS, pH 7.4). The complete copolymer/DNA complex was formed at an N/P ratio of 12, producing a complex resistant to DNase I. Particle sizes decreased with increasing N/P ratio and PEG molecular weight, exhibiting a minimum value of 75 nm at an N/P ratio of 45 with PEI-alt-PEG (700). Cytotoxicity study showed that copolymers exhibited no cytotoxic effects on cells even at high copolymer concentration. Also, transfection efficiency was influenced by PEG molecular weight and, in case of PEI-alt-PEG (258), the transfection efficiency was higher than that for PEI 25 K in HepG2 and MG63, whereas it was lower than that for PEI 25K in HeLa cells.
authors.affiliation: School of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Korea.
authors.forename: Mi Ran
authors.initials: MR
authors.lastname: Park
authors.forename: Ki Ok
authors.initials: KO
authors.lastname: Han
authors.forename: In Kwon
authors.initials: IK
authors.lastname: Han
authors.forename: Myung Haing
authors.initials: MH
authors.lastname: Cho
authors.forename: Jae Woon
authors.initials: JW
authors.lastname: Nah
authors.forename: Yun Jaie
authors.initials: YJ
authors.lastname: Choi
authors.forename: Chong Su
authors.initials: CS
authors.lastname: Cho
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003432:Cross-Linking Reagents; D004247:DNA / Q000008:administration & dosage* / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D005079:Excipients; D005434:Flow Cytometry; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D006801:Humans; D008156:Luciferases / Q000235:genetics; D018625:Microscopy, Atomic Force; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry*; D014162:Transfection
chemical_list: D003432:Cross-Linking Reagents; D005079:Excipients; D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D004247:DNA; D008156:Luciferases