Cellulose I Nanolayers Designed by Self‐Assembly of its Thiosemicarbazone on a Gold Substrate
Cellulose I Nanolayers Designed by Self‐Assembly of its Thiosemicarbazone on a Gold Substrate
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DOI：
10.1002/adma.200602761
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发表时间：
2007-10
影响因子：
29.4
通讯作者：
S. Yokota;T. Kitaoka;J. Sugiyama;H. Wariishi
中科院分区：
文献类型：
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作者：
S. Yokota;T. Kitaoka;J. Sugiyama;H. Wariishi
天然多糖的超分子结构作为智能材料在生物工程和纳米工程领域引起了广泛的关注。纤维素（B-1，4-D-葡聚糖）是高等植物细胞壁的主要成分，是最丰富的可再生生物资源。这种多糖显示出通过自组装进行分级组织的特定独特特征。天然纤维素是一种精心设计的结构，通过规则的分子内和链间氢键结合在一起。聚合物的晶体结构已被证明在帮助阐明其材料功能方面是非常宝贵的。纤维素的多晶型物也正在积极研究中。特别地，在生物合成期间，纤维素链自组装以在纵向方向上形成紧密堆积的规则排列，导致形成称为纤维素I的特征性晶体结构。目前正在研究纤维素材料顶面上形成的晶体结构的生物相容性。因此，结晶表面形态对纤维素材料的功能具有很大影响，因此非常需要具有受控表面形态的纤维素层。然而，纤维素I结构保持在亚稳态，使得一旦溶解然后沉积，纤维素链经历从平行到反平行排列的不可逆重排，受到热力学限制。许多研究人员报道了纤维素模型膜的制备，然而，所有这些膜都采用纤维素II结构，具有反平行排列或非结晶形态。因此，迄今为止，层状纤维素I结构的成功重建暗示了科学界。在本通讯中，我们描述了我们试图通过考虑纤维素分子的各向异性结构和规则的自组装特征来复制纤维素I结构。带状纤维素链的两端都有还原性和非还原性基团，分子的极性沿着其纵轴（图1）。还原端的醛基在化学上不同于纤维素分子中存在的羟基。因此，在本发明中，
Supramolecular architectures of natural polysaccharides have recently attracted much attention as smart materials from bioand nanoengineering perspectives. Cellulose (b-1,4-D-glucan), which forms the main constituent of the cell wall in higher plants, is the most abundant and renewable bioresource. This polysaccharide shows specific unique features for hierarchical organization by self-assembly. Native cellulose is an elaborately designed architecture bound together via regular intramolecular and interstrand hydrogen bonds. Crystallographic structures of polymers have proven invaluable in helping to elucidate their material functions. The crystalline polymorphs of cellulose are also being actively investigated. In particular, during biosynthesis, the cellulose chains self-assemble to form close-packed, regular arrangements in the longitudinal direction, resulting in the formation of the characteristic crystalline structure, referred to as cellulose I. The crystalline structures that form on the top surface of cellulosic materials are currently being investigated with regard to biocompatibility. Hence, the crystalline surface morphology has great impact on the function of cellulosic materials, as a result of which cellulose layers with controlled surface morphology are in great demand. However, the cellulose I structure is maintained in a metastable state such that once dissolved and then deposited, the cellulose chains undergo an irreversible rearrangement from parallel to antiparallel alignment, subject to thermodynamic restrictions. Many researchers have reported on the preparation of cellulose model films; however, all of these films adopt the cellulose II structure with an antiparallel arrangement or noncrystalline morphology. Thus, the successful reconstruction of the stratiform cellulose I structure has so far alluded the scientific community. In this Communication, we describe our attempts to replicate the cellulose I architecture by considering the anisotropic structure and regular self-assembling features of the cellulose molecule. The ribbonlike cellulose chain has reducing and nonreducing groups at either end, where the polarity of the molecule is directed along its longitudinal axis (Fig. 1). The aldehyde group at the reducing end is chemically different from the hydroxyl groups present in the cellulose molecule. Thus,