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Engineering and Modeling Carbon Nanofiller-Based Scaffolds for Tissue Regeneration

机译：工程和建模基于碳纳米填料的组织再生支架。

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摘要

Conductive biopolymers are starting to emerge as potential scaffolds of the future. These scaffolds exhibit some unique properties such as inherent conductivity, mechanical and surface properties. Traditionally, a conjugated polymer is used to constitute a conductive network. An alternative method currently being used is nanofillers as additives in the polymer. In this dissertation, we fabricated an intelligent scaffold for use in tissue engineering applications. The main idea was to enhance the mechanical, electrical properties and cell growth of scaffolds by using distinct types of nanofillers such as graphene, carbon nanofiber and carbon black. We identified the optimal concentrations of nano-additive in both fibrous and film scaffolds to obtain the highest mechanical and electrical properties without neglecting any of them. Lastly, we investigated the performance of these scaffold with cell biology.;To accomplish these tasks, we first studied the mechanical properties of the scaffold as a function of morphology, concentration and variety of carbon nanofillers. Results showed that there was a gradual increase of the modulus and the fracture strength while using carbon black, carbon nanofiber and graphene, due to the small and strong carbon-to-carbon bonds and the length of the interlayer spacing. Moreover, regardless of the fabrication method, there was an increase in mechanical properties as the concentration of nanofillers increased until a threshold of 7 wt% was reached for the nanofiller film scaffold and 1%wt for the fibrous scaffold. Experimental results of carbon black exhibited a good agreement when compared with data obtained using numerical approaches and analytical models, especially in the case of lower carbon black fractions.;Second, we examined the influence of electrical properties of nanofillers based on the concentration and the geometry of carbon nanofillers in the polymer matrix using experimental and numerical simulation approaches. The experimental results showed an increase in conductivity as the amount of nanofiller concentration increased. And regardless of nanofiller type, the trend remained the same. The percolation threshold was around 4-5wt% of nano-additive with PCL and PAN matrices, respectively. However, at the same concentrations, conductivity was higher in graphene-based nanocomposites than for CNF and carbon black-based nanocomposites. The numerical modeling highlighted the effect of nanofillers as constructing a conductive network due to the aggregation phenomenon. The conductivity trend for carbon black and carbon nanofiber-based composites by the numerical simulation approach was similar to the experimental approach.;Lastly, we studied the effect of these carbon nanocomposite-based scaffolds on the behavior of cell growth. The results showed that regardless of the scaffold shape (film or fiber) and the additive's type, when the concentration of nano-additives was increased, electrical conductivity and cell density increased also. For a given nano-additive concentration and type, cell density increased in the scaffolds with fiber shape vs. the film. Importantly, as the conductivity of the scaffolds increased, so did the cell density. Consequently, this study has highlighted the close relationship between electrical conductivity, cell density and scaffold orientation. An increase in conductivity can be achieved in two ways: by molecular orientation of the nanofillers or by the appropriate selection of nano-additives such as graphene and carbon nanofiber.
机译：导电生物聚合物已开始成为未来的潜在支架。这些支架表现出一些独特的性质，例如固有的导电性，机械和表面性质。传统上，使用共轭聚合物来构成导电网络。当前使用的替代方法是纳米填料作为聚合物中的添加剂。在本文中，我们制造了一种用于组织工程应用的智能支架。主要思想是通过使用不同类型的纳米填料（例如石墨烯，碳纳米纤维和炭黑）来增强支架的机械，电性能和细胞生长。我们确定了纤维和薄膜支架中纳米添加剂的最佳浓度，以获得最高的机械和电气性能而又不忽略任何它们。最后，我们通过细胞生物学研究了这些支架的性能。为了完成这些任务，我们首先研究了支架的力学性能，作为形态，浓度和碳纳米填料种类的函数。结果表明，由于碳-碳键小而牢固，并且层间间距的长度变大，使用炭黑，碳纳米纤维和石墨烯时模量和断裂强度逐渐增加。而且，不管制造方法如何，随着纳米填料的浓度增加直到纳米填料薄膜支架达到7wt％的阈值和纤维状支架达到1wt％的阈值，机械性能都有增加。与使用数值方法和分析模型获得的数据相比，炭黑的实验结果显示出良好的一致性，特别是在炭黑分数较低的情况下。其次，我们根据浓度和几何形状检查了纳米填料的电性能的影响。实验和数值模拟方法研究聚合物基体中的碳纳米填料。实验结果表明，随着纳米填料浓度的增加，电导率增加。而且，无论纳米填料类型如何，趋势都保持不变。用PCL和PAN基质的渗透阈值分别约为纳米添加剂的4-5wt％。但是，在相同浓度下，石墨烯基纳米复合材料的电导率要高于CNF和炭黑基纳米复合材料的电导率。数值模型强调了由于聚集现象，纳米填料在构造导电网络方面的作用。通过数值模拟方法对炭黑和碳纳米纤维基复合材料的电导率趋势与实验方法相似。最后，我们研究了这些碳纳米复合物基支架对细胞生长行为的影响。结果表明，不管支架的形状（膜或纤维）和添加剂的类型如何，当纳米添加剂的浓度增加时，电导率和细胞密度也会增加。对于给定的纳米添加剂浓度和类型，与纤维膜相比，具有纤维形状的支架中的细胞密度增加。重要的是，随着支架电导率的增加，细胞密度也随之增加。因此，这项研究强调了电导率，细胞密度和支架取向之间的密切关系。可以通过两种方式实现电导率的提高：通过纳米填料的分子取向或通过适当选择纳米添加剂（例如石墨烯和碳纳米纤维）。

著录项

  • 作者

    Al Habis, Nuha Hamad.;

  • 作者单位

    University of Dayton.;

  • 授予单位 University of Dayton.;
  • 学科 Biomedical engineering.;Materials science.;Engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 202 p.
  • 总页数 202
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 人类学;
  • 关键词

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