Polymer vesicles containing small vesicles within interior aqueous compartments and pH-Responsive transmembrane channels
Polymer vesicles containing small vesicles within interior aqueous compartments and pH-Responsive transmembrane channels
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DOI：
10.1002/anie.200704078
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Chern, Chorng-Shyan
中科院分区：
文献类型：
--
作者：
Chiu, Hsin-Cheng;Lin, Yue-Wen;Chern, Chorng-Shyan
两亲性嵌段共聚物到囊泡的分子间包装是特别感兴趣的，由于这样的系统作为一类具有良好控制的结构和潜在的生物医学应用的新的聚合物组件的基本重要性。[1-4]与传统的脂质体类似，聚合物囊泡通常形成主要由共聚物的疏水嵌段组成的连续双层结构，但它们表现出显着增强的稳定性和响应于外部刺激而引入官能团的可行性。[5]然而，聚合物囊泡作为生物功能容器的主要限制是由于需要保持结构完整性而缺乏亲水性货物的渗透途径。[6，7]从嵌段共多肽获得的囊泡在多肽嵌段的pH诱导的构象变化时被赋予响应通道。[7]报道了氧化还原对含聚二茂铁基硅烷多层微胶囊渗透性的控制。[8]将通道形成蛋白质插入囊泡膜中，同时完全保留蛋白质功能，代表了为聚合物囊泡配备跨膜通道的重要范例。[9，10]因此，可以通过所选择的孔蛋白来定制尺寸选择性或底物特异性的运输机制。还期望具有通用的囊泡组件，其以类似于真核细胞内的离散细胞器的方式在内部水性隔室内含有小囊泡，其执行不同的功能并且是与原核对应物的特征差异之一。不幸的是，这种组件结构控制尚未实现。在本文中，我们显示了类似于真核细胞的结构布置的聚合物多囊泡组件的第一个实例，其中两个囊泡膜都配备有亲水性溶质可渗透的pH响应性通道（方案1）。聚（N-丙烯酰氧基琥珀酰亚胺）（poly（NAS））与双硬脂酸甘油酯部分酯交换反应，再水解生成丙烯酸（AAc）和1，2-双硬脂酰甘油丙烯酸酯（DSA）。在水/油/水（w1/o/w2）体系中通过双乳液技术制备聚合物囊泡，其中在乳化之前将共聚物溶解在有机相中。实验方法详见支持信息。根据目标囊泡的大小，采用不同比例的THF/CH 3Cl溶液作为有机相。水或pH范围为4.0-5.5的缓冲液用作内水相（w1）和外水相（w2）。在w 1/o/w 2乳液中，有机溶剂蒸发后形成囊泡。然而，共聚物组装成胶束pH高于5。5和低于pH 4的大沉淀。0.除非另有说明，否则囊泡主要由平均分子量为2.97 × 105 g mol/1且组成为9.1 mol% DSA的共聚物获得。图1a证实了所得组装体是单层囊泡。利用尼罗红的荧光特性，研究了聚合物囊泡在水溶液中的激光扫描共聚焦显微镜（LSCM）成像。可通过扫描电子显微镜观察冻干囊泡（见支持性信息）。这种聚合物胶体在经历从含水状态到干燥状态的转变时保持其结构完整性的事实反映了其稳健的稳定性。透射电子显微镜（TEM）检查...
Intermolecular packing of amphiphilic block copolymers into vesicles is of particular interest, owing to the fundamental importance of such systems as a new class of polymer assemblies with well-controlled structures and potential biomedical applications.[1–4] Similar to conventional liposomes, polymer vesicles usually form a continuous bilayer structure primarily consisting of the hydrophobic blocks of copolymers, but they exhibit markedly enhanced stability and feasibility of incorporating functional groups in response to external stimuli.[5] However, the major limitation of polymer vesicles as biofunctional containers arises from the lack of permeation pathway for hydrophilic cargoes owing to the requirement to maintain the architectural integrity.[6, 7] The vesicles obtained from block co-polypeptides are imparted responsive channels upon the pH-induced conformational change of a polypeptide block.[7] Redox control of the permeability of multilayer microcapsules containing poly-(ferrocenylsiliane) was reported.[8] Incorporating channelforming proteins into the vesicle membranes while fully retaining the protein functions represents an important paradigm of equipping polymer vesicles with transmembrane channels.[9, 10] Thus, the transport mechanism, being either size-selective or substrate-specific, can be tailored by the pore proteins selected. It is also desirable to have versatile vesicular assemblies that contain small vesicles within the interior aqueous compartments in a manner similar to discrete organelles within eukaryotic cells, which perform diverse functions and are one of the feature differences from prokaryotic counterparts. Unfortunately, such assembly structural control has not yet been achieved. Herein, we show the first example of polymeric multivesicle assemblies similar to the architectural arrangement of eukaryotic cells, in which both the vesicle membranes are equipped with pH-responsive channels permeable for hydrophilic solutes (Scheme 1). Copolymers comprising acrylic acid (AAc) and acrylate of 1, 2-distearoyl-rac-glycerol (distearin acrylate, DSA) were obtained from partial transesterification of poly (N-acryloxysuccinimide)(poly (NAS)) with distearin and then thorough hydrolysis of the unreacted NAS to AAc units. Polymer vesicles were prepared by a double emulsion technique in a water/oil/water (w1/o/w2) system, in which the copolymer was dissolved in the organic phase prior to emulsification. The experimental methods are described in detail in the Supporting Information. THF/CH3Cl solutions of varying ratios, depending on the target vesicle size, were employed as the organic phase. Either water or buffers in the pH range of 4.0–5.5 were used as both the inner (w1) and outer (w2) aqueous phases. The vesicles formed upon the evaporation of organic solvents in w1/o/w2 emulsions. However, the copolymers assembled into micelles above pH5. 5 and large precipitates below pH4. 0. The vesicles were obtained mainly from copolymer with an average molecular weight of 2.97 105 g molÀ1 and a composition of 9.1 mol% DSA, unless stated otherwise. Figure 1a confirms that the resultant assemblies are unilamellar vesicles. The laser scanning confocal microscopy (LSCM) image of polymer vesicles in aqueous suspensions was revealed by the fluorescence of Nile red associated with the vesicle membranes. The lyophilized vesicles can be observed by scanning electron microscopy (see the Supporting Information). The fact that such polymer colloids maintain their structural integrity when subjected to transition from the aqueous to dried state reflects their robust stability. Transmission electron microscopy (TEM) examination of …