School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
J Biomed Mater Res A. 2009 Dec;91(3):708-18. doi: 10.1002/jbm.a.32255.
Amphiphilic polyelectrolytes comprising cationic and uncharged hydrophilic segments condensed negatively charged DNA to form a core-shell structure stabilized by a layer of hydrophilic corona chains. At physiological pH, four-arm star-shaped poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate) (four-arm PEO-b-PDEAEMA) block copolymer possessed positively charged amine groups that interacted with negatively charged plasmid DNA to form polymer/DNA complexes. The mechanism and physicochemical properties of the complex formation were investigated at varying molar ratio of amine groups on polymer chains and phosphate group on plasmid DNA segments (N/P ratio). The capability of the star block copolymer to condense DNA was demonstrated through gel electrophoresis and ethidium bromide exclusion assay. In the absence of salt, the hydrodynamic radius of polyplexes was about 94 nm at low polymer/DNA ratio, and it decreased to about 34 nm at large N/P ratios, forming a compact spherical structure with a weighted average molecular weight of 4.39 +/- 0.22 x 10(6) g/mol. Approximately 15 polymeric chains were required to condense a plasmid DNA. The addition of monovalent salt to the polyplexes significantly altered the size of the complexes, which would have an impact on cell transfection. Because of the electrostatic interaction induced by the diffusion of small ions, the polyplex increased in size to about 53 nm with a less compact structure. In vitro cytotoxicty of polymer and polymer/pDNA complexes were evaluated, and the polyplexes exhibited low toxicity at low N/P ratios. At N/P ratio of 4.5, the four-arm PEO-b-PDEAEMA showed the highest level of transfection in Neuro-2A cells. These observations showed that the star-shaped multi-arm polymers offers interesting properties in self-association and condensation ability for plasmid DNA and can serve as a nonviral DNA delivery system.
包含阳离子和亲水非离子段的两亲性聚电解质将带负电荷的 DNA 凝聚形成核壳结构，该结构由一层亲水性冠链稳定。在生理 pH 下，四臂星形聚（环氧乙烷）-b-聚（2-（二乙基氨基）乙基甲基丙烯酸酯）（四臂 PEO-b-PDEAEMA）嵌段共聚物具有带正电荷的伯胺基团，可与带负电荷的质粒 DNA 相互作用形成聚合物/DNA 复合物。通过改变聚合物链上伯胺基团与质粒 DNA 片段上磷酸基团的摩尔比（N/P 比），研究了复合物形成的机制和物理化学性质。通过凝胶电泳和溴化乙锭排除实验证明了星型嵌段共聚物的 DNA 凝聚能力。在不存在盐的情况下，低聚合物/DNA 比时，聚合物的水动力半径约为 94nm，当 N/P 比较大时，水动力半径降低至约 34nm，形成具有加权平均分子量为 4.39 +/- 0.22 x 10(6)g/mol 的紧凑球形结构。大约 15 个聚合物链可以凝聚一个质粒 DNA。向聚合物中加入单价盐会显著改变复合物的大小，从而对细胞转染产生影响。由于小离子扩散引起的静电相互作用，复合物的尺寸增加到约 53nm，结构不太紧凑。评估了聚合物和聚合物/pDNA 复合物的体外细胞毒性，并且在低 N/P 比时，聚合物表现出低毒性。在 N/P 比为 4.5 时，四臂 PEO-b-PDEAEMA 在 Neuro-2A 细胞中表现出最高的转染水平。这些观察结果表明，星形多臂聚合物在自组装和对质粒 DNA 的凝聚能力方面具有有趣的性质，并且可以作为非病毒 DNA 传递系统。
