Acid-Sensitive Polymeric Micelles Based on Thermoresponsive Block Copolymers with Pendent Cyclic Orthoester Groups
Acid-Sensitive Polymeric Micelles Based on Thermoresponsive Block Copolymers with Pendent Cyclic Orthoester Groups
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基于具有悬垂环状原酸酯基团的热响应性嵌段共聚物的酸敏聚合物胶束
DOI：
10.1021/ma802138r
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发表时间：
2009-02-10
期刊：
影响因子：
5.5
通讯作者：
Li, Zichen
中科院分区：
文献类型：
--
作者：
Huang, Xiaonan;Du, Fusheng;Li, Zichen
合成了含原酸酯的单体反式-N-(2-乙氧基-1,3-二恶烷-5-基)丙烯酰胺(tNEA)。使用聚乙二醇（PEG）大分子引发剂对 tNEA 进行原子转移自由基聚合，得到三种酸不稳定的热响应性嵌段共聚物：PEG-b-PtNEA（27）、PEG-b-PtNEA（56）和 PEG-b-PtNEA（73）。这些嵌段共聚物在低温（< 13℃）下是水溶性的。通过光散射和 H-1 NMR 研究了这些聚合物的热诱导相变行为，包括临界聚集温度 (CAT)。结果表明，PtNEA 链长越长，CAT 越低。在 CAT 上方加热时，所有三种聚合物都经历相变并形成以 PEG 为壳、PtNEA 块为核的聚合物胶束或胶束状纳米颗粒。发现胶束的尺寸和形态均受到加热速率和缓冲液中盐浓度的影响。通过快速加热过程在盐浓度相对较高的缓冲液中形成的胶束具有更小的尺寸和更致密的结构。通过光散射和尼罗红荧光研究了由 PEG-b-PtNEA(73) 制备的聚合物胶束的 pH 依赖性去稳定性。结果表明，疏水性尼罗红可以负载在 pH 7.4 下稳定的胶束中，但在弱酸性介质中不稳定。酸引发的原酸酯基团水解诱导了胶束的解离和随后尼罗红的释放，这一点由 H-1 NMR 谱证明。
An orthoester-containing monomer, trans-N-(2-ethoxy-1,3-dioxan-5-yl)acrylamide (tNEA), was synthesized. Atom transfer radical polymerization of tNEA using a poly(ethylene glycol) (PEG) macroinitiator afforded three acid-labile thermoresponsive block copolymers: PEG-b-PtNEA(27), PEG-b-PtNEA(56), and PEG-b-PtNEA(73), These block copolymers are water-soluble at low temperatures (< 13 degrees C). Thermally induced phase transition behaviors, including the critical aggregation temperatures (CATs), of these polymers were investigated by light scattering and H-1 NMR. The results indicated that the longer the PtNEA chain length, the lower the CAT. Upon heating above the CATs, all the three polymers underwent a phase transition and formed polymeric micelles or micelle-like nanoparticles with PEG as the shell and PtNEA block as the core. Both the sizes and morphologies of the micelles were found to be affected by the heating rate and the salt concentration in the buffers. The micelles, formed through a fast heating procedure ill the buffer with a relatively high salt concentration, have a smaller size and a more compacted structure. pH-dependent destabilization of the polymeric micelles prepared from PEG-b-PtNEA(73) was studied by using light scattering and Nile Red fluorescence. The results demonstrated that hydrophobic Nile Red could be loaded in the micelles that were stable at pH 7.4, but destabilized in mildly acidic media. The dissociation of the micelles and the subsequent release of Nile Red were induced by the acid-triggered hydrolysis of the orthoester groups, which was proved by the H-1 NMR spectra.