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首页> 外文学位 >Development of rheological characterization and twin-screw extrusion/spiral winding processing methods for functionally-graded tissue engineering scaffolds and characterization of cell/biomaterial interactions.
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Development of rheological characterization and twin-screw extrusion/spiral winding processing methods for functionally-graded tissue engineering scaffolds and characterization of cell/biomaterial interactions.

机译：流变学表征和功能梯度组织工程支架的双螺杆挤出/螺旋缠绕加工方法的发展以及细胞/生物材料相互作用的表征。

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Tissue engineering involves the fabrication of biodegradable scaffolds, on which various types of cells are grown, to provide tissue constructs for tissue repair/regeneration. Native tissues have complex structures, with functions and properties changing spatially and temporally, and require special tailoring of tissue engineering scaffolds to allow mimicking of their complex elegance. The understanding of the rheological behavior of the biodegradable polymer and the thermo-mechanical history that the polymer experiences during processing is critical in fabricating scaffolds with appropriate microstructural distributions. This study has first focused on the rheological material functions of various gel-like fluids including biofluids and hydrogels, which can emulate the viscoelastic behavior of biofluids. Viscoplasticity and wall slip were recognized as key attributes of such systems. Furthermore, a new technology base involving twin-screw extrusion/spiral winding (TSESW) process was developed for the shaping of functionally-graded scaffolds. This novel scaffold fabrication technology was applied to the development of polycaprolactone (PCL) scaffolds, incorporated with tricalcium phosphate nanoparticles and various porogens in graded fashion. The protein encapsulation and controlled release capabilities of the TSESW process was also demonstrated by dispersing bovine serum albumin (BSA) protein into the PCL matrix. Effects of processing conditions and porosity distributions on compressive properties, surface topography, encapsulation efficiency, release profiles and the secondary structure of BSA were investigated. The PCL scaffolds were determined to be biocompatible, with the proliferation rates of human fetal osteoblast cells (hFOB) increasing with increasing porosity and decreasing concentration of TCP. BSA proteins were determined to be denatured to a greater extent with melt extrusion in the 80-100°C range (in comparison to wet extrusion using organic solvents). Finally, the surface topographies of melt processed poly(L-lactic acid) (ranging from nanoindentations to spherulitic protrusions) were determined to affect the orientation directions of fibroblast and osteoblast-like cells and the spherulitic surfaces giving rise to reduced proliferation rates of fibroblasts.
机译：组织工程涉及制造可生物降解的支架，在其上生长各种类型的细胞，以提供用于组织修复/再生的组织构建体。天然组织具有复杂的结构，其功能和特性会在空间和时间上发生变化，并且需要对组织工程支架进行特殊剪裁以模仿其复杂的优雅风格。对于可生物降解的聚合物的流变行为和聚合物在加工过程中经历的热机械历史的理解对于制造具有适当的微结构分布的支架至关重要。这项研究首先关注各种凝胶状流体的流变材料功能，包括生物流体和水凝胶，它们可以模拟生物流体的粘弹性行为。粘塑性和壁滑被认为是此类系统的关键属性。此外，还开发了涉及双螺杆挤出/螺旋缠绕（TSESW）工艺的新技术基础，以成型功能梯度支架。这项新颖的脚手架制造技术被应用于聚己内酯（PCL）脚手架的开发，该脚手架与磷酸三钙纳米颗粒和各种成孔剂以分级的方式结合在一起。通过将牛血清白蛋白（BSA）蛋白质分散到PCL基质中，也证明了TSESW过程的蛋白质包封和控制释放能力。研究了工艺条件和孔隙率分布对BSA压缩性能，表面形貌，包封效率，释放曲线和二级结构的影响。确定PCL支架具有生物相容性，其中人胎儿成骨细胞（hFOB）的增殖率随孔隙率的增加和TCP浓度的降低而增加。经测定，在80-100°C的范围内，与熔融挤出相比，BSA蛋白具有更大程度的变性（与使用有机溶剂的湿挤出相比）。最后，确定熔融加工的聚（L-乳酸）的表面形貌（从纳米压痕到球状突起），以影响成纤维细胞和成骨细胞样细胞的取向方向，并且球状表面导致成纤维细胞的增殖速率降低。

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