Highly stable giant supramolecular vesicles composed of 2D hydrogen-bonded sheet structures of guanosine derivatives.
Highly stable giant supramolecular vesicles composed of 2D hydrogen-bonded sheet structures of guanosine derivatives.
复制标题
DOI：
10.1002/anie.200704535
复制
发表时间：
2008-01
影响因子：
--
通讯作者：
Isao Yoshikawa;Jun Sawayama;K. Araki
中科院分区：
文献类型：
--
作者：
Isao Yoshikawa;Jun Sawayama;K. Araki
随着纳米技术的飞速发展，具有高度有序结构的纳米至微米尺度材料的设计和制备备受关注。[1]尽管共价键合的聚合物已主要用作宏观尺度材料，但由于共价键的稳健性，控制其链排列和/或对齐的尝试遇到了相当大的困难。相比之下，通过相对较软的分子间相互作用组装的超分子材料适合于此目的。在水介质中，脂质和两亲物主要通过疏水相互作用自组装成纳米至介观尺度的膜和囊泡。[2]虽然这些结构具有动态特性，但由于分子间相互作用的可逆性质，这些结构的稳定性相对较差，特别是巨大的微米尺寸囊泡，是实际应用的主要缺点。[3]聚合囊泡，[4]二嵌段共聚物系统，[5]和其他类型的囊泡[3a，6]已被广泛研究，以规避这个问题。由特殊设计的非亲核分子制备的超分子囊泡越来越多地被报道。[7]尽管使用相对较强且定向的氢键似乎是实现这一目标的一种有希望的方法，但氢键相互作用仅在非极性环境中有效[8]，而在高极性水介质中则不然。[9]在此，我们表明，合理的分子设计将二维（2D）氢键网络夹在非极性保护层之间，并适当控制所得片材结构的极性表面，可以制造具有高稳定性的纳米和微胶囊，我们以前已经证明，烷基硅烷化脱氧鸟苷衍生物1a可以通过简单的方法制备成柔性的大尺度超分子膜。溶剂浇铸法（图1）。[10]在这种宏观尺度的薄膜中，具有N1 → H··· N7和2-NH 2··· O= C6氢键的鸟嘌呤分子的一维带进一步通过两个2-NH 2··· N3氢键连接，形成二维氢键层。该氢键结合的鸟嘌呤层夹在非极性和柔性烷基甲硅烷基侧链层之间，从而形成2D片状结构。位于片层结构表面的氧杂环基团增强了片层间的相互作用，并导致形成层状膜结构。然而，1a根本不溶解或分散在水中。为了增加亲水性，制备了具有扩展的氧化单元的1b和1c。用它们的四氢呋喃（THF）溶液制备溶剂流延薄膜的尝试
The rapid progress in nanoscale technology has resulted in the design and fabrication of nano-to micrometer-scale materials composed of highly organized structures attracting much attention.[1] Although covalently bonded polymers have been used predominantly as macroscale materials, attempts to control their chain arrangement and/or alignment has encountered considerable difficulty because of the robustness of the covalent bonds. In contrast, supramolecular materials which are assembled by relatively soft intermolecular interactions are suitable for this purpose. In aqueous media, lipids and amphiphiles self-assemble into nano-to mesoscopic-scale membranes and vesicles mainly through hydrophobic interactions.[2] Although these structures have dynamic properties, as a result of the reversible nature of the intermolecular interactions, the relatively poor stability of the structures, especially giant micrometer-sized vesicles, is a major drawback for practical applications.[3] Polymerized vesicles,[4] diblock copolymer systems,[5] and other types of vesicles [3a, 6] have been studied extensively to circumvent this problem. Supramolecular vesicles prepared from specially designed nonlipidic molecules are being increasingly reported.[7] Although the use of relatively strong and directional hydrogen bonds seems to be a promising approach to this end, hydrogen-bonding interactions only operate effectively in nonpolar environments [8] and not in highly polar aqueous media.[9] Herein, we show that a rational molecular design to sandwich two-dimensional (2D) hydrogen-bonding networks between nonpolar protective layers and proper control of the polar surfaces of the resultant sheet structure allow for the fabrication of nano-and microcapsules with high stability, even in aqueous media.We previously showed that alkylsilylated deoxyguanosine derivative 1a can be fabricated into a flexible macroscale supramolecular film by a simple solvent-cast method (Figure 1).[10] In this macroscale film, 1D tapes of guanine molecules with N1ÀH··· N7 and 2-NH2··· O= C6 hydrogen bonds are further connected by two 2-NH2··· N3 hydrogen bonds to form a 2D hydrogen-bonded layer. This hydrogen-bonded guanine layer is sandwiched between nonpolar and flexible alkylsilyl side-chain layers, thereby forming a 2D sheetlike structure. The oxyethylene groups located at the surface of the sheet structures enhance the intersheet interactions and results in the formation of the lamellar-like film structure. However, 1a did not dissolve or disperse in water at all. To increase the hydrophilicity, 1b and 1c, which have extended oxyethylene units, were prepared. An attempt to prepare a solvent-cast film from their tetrahydrofuran (THF) solutions