Abstract：
Inspired by the anisotropic structure of biological tissues, anisotropic hydrogels have been developed using various nanofillers, however, it remains a big challenge to synthesize hydrogels with large swelling anisotropy. Herein a single molecule filler, α-helical polypeptide, instead of nanoscale fillers, was used to synthesize anisotropic hydrogels. First nematic liquid crystal of poly(γ-benzyl l-glutamate) (PBLG) was prepared by shearing and stabilized by embedding in a crosslinked polymer matrix. The resulting PBLG composite gels were then converted to poly(L-glutamic acid) (PLGA) composite gels by debenzylation. The rigid rod-like structure of α-helical PBLG chains makes them easy to be orientated. The pH-sensitivity of PLGA makes the resulting composite gels pH-sensitive without the need to couple with a stimuli-responsive hydrogel matrix. In response to pH change PLGA composite gels swell anisotropically with a much larger swelling degree in the radial direction than in the axial direction. The swelling anisotropy (3.43) is much higher than most anisotropic hydrogels, particularly the stimuli-responsive ones reported previously. The composite gel also exhibits anisotropic mechanical properties with a larger Young\'s modulus in the axial direction than that in the radial direction. Preliminary test demonstrated that the composite gels have potential in embolotherapy thanks to its large pH-triggered anisotropic swelling. STATEMENT OF SIGNIFICANCE: Anisotropic hydrogels have important biomedical applications. Introduction of oriented nanofillers has been demonstrated a popular and versatile method for their synthesis, however, it remains a big challenge to achieve large swelling anisotropy. Herein a single molecule filler, α-helical polypeptide, instead of nanoscale fillers, was used to synthesize anisotropic hydrogels. This filler can be easily oriented by shearing. More importantly, as single molecule filler, it can constrain the swelling of hydrogel matrix more effectively. Using this filler, a pH-sensitive hydrogel with large swelling anisotropy (3.43) was successfully synthesized. Thanks to its large pH-triggered anisotropic swelling the hydrogel was successfully used as embolic agent to occlude vessels.
摘要：
受生物组织各向异性结构的启发，各向异性水凝胶已经使用各种纳米填料开发，然而,合成具有大的溶胀各向异性的水凝胶仍然是一个巨大的挑战。这里是单分子填料，α-螺旋多肽,代替纳米级填料，用于合成各向异性水凝胶。通过剪切制备聚（γ-苄基1-谷氨酸）（PBLG）的第一向列型液晶，并通过嵌入交联的聚合物基质中进行稳定。然后通过脱苄基作用将所得PBLG复合凝胶转化为聚(L-谷氨酸)(PLGA)复合凝胶。α螺旋PBLG链的刚性杆状结构使其易于定向。PLGA的pH敏感性使得所得复合凝胶的pH敏感性不需要与刺激响应性水凝胶基质偶联。响应于pH变化，PLGA复合材料凝胶在径向方向上的膨胀程度比在轴向方向上的膨胀程度大得多。溶胀各向异性（3.43）远高于大多数各向异性水凝胶，特别是以前报道的刺激反应性。复合凝胶还表现出各向异性的机械性能，轴向杨氏模量大于径向杨氏模量。初步测试表明，由于其大的pH触发各向异性溶胀，复合凝胶在栓塞治疗中具有潜力。重要性声明:各向异性水凝胶具有重要的生物医学应用。定向纳米填料的介绍已被证明是一种流行和通用的合成方法，然而,它仍然是一个很大的挑战，以实现大的膨胀各向异性。这里是单分子填料，α-螺旋多肽,代替纳米级填料，用于合成各向异性水凝胶。该填料可以通过剪切容易地取向。更重要的是,作为单分子填料，能更有效地抑制水凝胶基质的溶胀。使用这种填料，成功合成了具有大溶胀各向异性(3.43)的pH敏感水凝胶。由于其大的pH触发的各向异性溶胀,水凝胶被成功地用作栓塞剂以闭塞血管。
