School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin, PR China.
Biomaterials. 2010 Jan;31(3):559-69. doi: 10.1016/j.biomaterials.2009.09.055. Epub 2009 Sep 30.
In this work, we synthesized a star cationic polymer(s-PDMAEMA) consisting of cleavable polyN,N-bis(acryloyl) cystamine crosslinked core and poly(N,N-dimethyl-ethylamine methacrylate) (PDMAEMA) arms by atomic transfer radical polymerization using one-pot "arm first" method. The s-PDMAEMA that was degradable in a mimic intracellular redox environment was more efficient in condensing DNA. It was shown that s-PDMAEMA achieved higher gene transfection levels relative to their linear precursors and s-PDMAEMA200 with longer and more arms exhibited superior transfection efficiencies and lower cytotoxicity compared to PEI25K. The buffer capacities were examined by acid-base titration; the pH-dependent morphological evolution and enzyme stability of PDMAEMA/DNA complexes were investigated by atomic force microscopy (AFM) and time-resolved fluorescence spectroscopy, respectively. The results indicated that the star polymers exhibited a stronger buffering ability than their linear precursors due to the increased inner osmotic pressure. By decreasing the pH from 7.4 to 5.0, the linear PDMEMA/DNA complexes became more compact; in contrast, s-PDMAEMA200/DNA complex adopted a loose morphology due to the steric barrier of inter-arms and outward extension of positively charged arms. Analysis of the fluorescence life times of free and intercalated ethidium bromide unveiled more effective protection of DNA afforded by s-PDMAEMA. The effect of medium pH on the star PDMAEMA system was smaller owing to the ability of densely tertiary amino groups along multiple arms to absorb more protons, which was favorable for endosomolytic escape of complexes.
在这项工作中，我们通过原子转移自由基聚合的一锅“臂先”法，合成了一种由可裂解的聚[N,N-双（丙烯酰）半胱氨酸]（PBAC）交联核和聚（N,N-二甲基乙基丙烯酰胺）（PDMAEMA）臂组成的星型阳离子聚合物（s-PDMAEMA）。在模拟细胞内氧化还原环境下可降解的 s-PDMAEMA 对 DNA 的凝聚更有效。结果表明，与线性前体相比，s-PDMAEMA 实现了更高的基因转染水平，并且具有更多和更长臂的 s-PDMAEMA200 与 PEI25K 相比，表现出更高的转染效率和更低的细胞毒性。通过酸碱滴定法测定了缓冲能力；通过原子力显微镜（AFM）和时间分辨荧光光谱分别研究了 PDMAEMA/DNA 复合物的 pH 依赖性形态演变和酶稳定性。结果表明，由于内渗透压的增加，星形聚合物比其线性前体具有更强的缓冲能力。通过将 pH 值从 7.4 降低至 5.0，线性 PDMEMA/DNA 复合物变得更加紧凑；相比之下，由于臂间的空间位阻和带正电荷臂的向外延伸，s-PDMAEMA200/DNA 复合物采用了松散的形态。自由和嵌入溴化乙锭的荧光寿命分析表明，s-PDMAEMA 能够更有效地保护 DNA。由于多个臂上的密集叔氨基能够吸收更多的质子，因此星形 PDMAEMA 体系受介质 pH 的影响较小，这有利于复合物的内体溶酶体逃逸。
