The Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
J Mech Behav Biomed Mater. 2012 Mar;7:50-9. doi: 10.1016/j.jmbbm.2011.09.009. Epub 2011 Sep 22.
Scaffolds constitute an essential structural component in tissue engineering of a vascular substitute for small grafts by playing a significant role in integrating the overall tissue constructs. The microstructure and mechanical properties of such scaffolds are important parameters to promote further cellular activities and neo-tissue development. Cellulose nanowhiskers (CNWs), an abundant, biocompatible material, could potentially constitute an acceptable candidate in scaffolding of a tissue-engineered vessel. Inspired by the advantages of cellulose and its derivatives, we have designed a biomaterial comprising CNWs embedded in a matrix of cellulose acetate propionate to fabricate a fully bio-based scaffold. To ensure uniform distribution, CNWs were delicately extracted from a multi-stage process and dispersed in an acetone suspension prior to the composite fabrication. Comparable to carbon nanotubes or kevlar, CNWs impart significant strength and directional rigidity even at 0.2 wt% and almost double that at only 3.0 wt%. To ensure the accuracy of our experimental data and to predict the unusual reinforcing effect of CNWs in a cellulose-based composite, homogenization schemes such as the mean field approach and the percolation technique were also investigated. Based on these comparisons, the tendency of CNWs to interconnect with one another through strong hydrogen bonding confirmed the formation of a three-dimensional rigid percolating network, fact which imparted an excellent mechanical stability to the entire structure at such low filler contents. Hence, our fibrous porous microstructure with improved mechanical properties could introduce a potential scaffold to withstand the physiological pressure and to mimic the profile features of native extracellular matrix in a human vessel. We believe that our nanohybrid design not only could expand the biomedical applications of renewable cellulose-based materials but also could provide a potential scaffold candidate in tissue engineering of small diameter grafts.
支架是小口径移植物组织工程中血管替代物的重要结构组成部分，在整合整个组织构建中起着重要作用。支架的微观结构和机械性能是促进细胞进一步活动和新组织发展的重要参数。纤维素纳米纤维（CNWs）是一种丰富的、生物相容性的材料，有可能成为组织工程血管支架的可接受候选材料。受纤维素及其衍生物优点的启发，我们设计了一种生物材料，该材料由嵌入醋酸丙酸纤维素基质中的 CNWs 组成，以制造完全基于生物的支架。为了确保均匀分布，CNWs 经过多步精细提取，并在复合制造前分散在丙酮悬浮液中。与碳纳米管或凯夫拉纤维类似，即使在 0.2wt%的情况下，CNWs 也能赋予显著的强度和各向刚性，而在仅 3wt%的情况下，其强度几乎是前者的两倍。为了确保我们实验数据的准确性，并预测 CNWs 在纤维素基复合材料中的异常增强效果，还研究了均匀化方案，如平均场方法和渗流技术。基于这些比较，CNWs 通过强氢键相互连接的趋势证实了三维刚性渗流网络的形成，这一事实赋予了整个结构在如此低的填充含量下优异的机械稳定性。因此，我们具有改进机械性能的纤维状多孔微观结构可以引入一种潜在的支架，以承受生理压力，并模仿人体血管中天然细胞外基质的轮廓特征。我们相信，我们的纳米杂化设计不仅可以扩展可再生纤维素基材料的生物医学应用，还可以为小直径移植物的组织工程提供潜在的支架候选材料。
