Fabrication Of Medical Polymeric Tissue Engineering Scaffolds And Their Structure And Properties Research

Tissue engineering scaffold is one of the most important part in Tissue Engineering. In Tissue Engineering, the scaffolds could temporarily replace the damaged native tissue, support cell growth and tissue regeneration, and ensure the normal activity of human body by specific physical properties. How to prepare scaffolds suitable for various tissue has been an important and difficult points of Tissue Engineering. In this Ph D thesis, in-depth research on tissue engineering scaffolds fabrication were studied based on three different approaches including microcellular injection molding, electrospinning and thermally induced phase separation. By controlling and improvement of scaffolds fabrication process and optimizing the material combination, the micro structure and macro properties of the scaffolds were precisely controlled, the scaffolds have three dimensional porous structure, high porosity and pore interconnectivity, ideal physical and surface properties, and suitable for cell growth were fabricated. Moreover, triple layered vascular scaffolds that resemble native blood vessel structure were fabricated by combining different methods.Microcellular injection molding could produce porous scaffolds in large scale, in the relevant research, the relationship between foaming conditions and mechanical properties were investigated via orthogonal array test, and it was found that the processing temperature and CO2 content were the most influential factors for the microstructure of TPU scaffolds. The use of water and CO2 as co-blowing agents resulted in skinless scaffolds with uniform and board pore distribution. Scaffolds with various pore structure and mechanical properties were obtained by combining soft and hard TPU via melt compounding and microcellular injection molding. The same method was used in the TPU/PLA system as well to prepare scaffolds with various properties that suitable for several types of tissue. The porosity, pore interconnectivity and biocompatibility of TPU scaffolds were enhanced by introducing water soluble content salt and PVOH into TPU matrix and subsequent particle leaching process. The PCL/CNC nanocomposites scaffolds prepared via microcellular injection molding had high pore density, uniform pore dispersion, and enhanced tensile strength and strain-at-break of 71% and 510% respectively, because of the reinforcing and nucleating effects of CNC particles.Fibrous scaffolds obtained by electrospinning have high interaction with cells and possess structure resembles the extracellular matrix(ECM) of human body. In this research aspect, first, the fiber formation mechanism TPU solution was investigated. It was found that bead-less fibers could obtained when the solution concentration was higher than two times of critical molecular chain entanglement concentration, and different soft and hard segment ratio could result in different fiber mat properties which affected cellular response. Second, it was found in TPU/HA composites scaffolds research that nano HA had better dispersion, and the human mesenchymal stem cells were proliferated and differentiated on the scaffolds very well. Moreover, a self-made fiber collection device was used to obtain unidirectionally aligned and orthogonally aligned TPU fibers. The orientation degree was further improved by adding conducting component in the solution such as CNT and PAA. The mouse fibroblast showed better proliferation and migration distance and speed on the oriented fibers, and the cells were tend to aligned along the fiber direction, which indicated that the fibers could stimulate cell migration behavior.Thermally induced phase separation(TIPS) could produce 3D scaffolds with high porosity and pore interconnectivity. In the relevant research, various solvent system and porogen were used to investigate their effects on the scaffolds structure formation. It was found that leader-like structure was obtained using dioxane as solvent, while highly interconnected round porous structure was obtained using water and dioxane as co-solvent. The addition of salt porogen resulted in porosity as high as 93%. The addition of HA particles enhanced the toughness of the scaffolds and the scaffolds containing nano HA had excellent mineralization property which accumulated bone-like apatite in simulated body fluid. Porous TPU scaffolds could be prepared using DMSO as solvent as well. The addition of CNT and NFC improved the mechanical properties of the scaffolds significantly, the biocompatibility of the prepared scaffolds was verified via cell culture tests.Based on various scaffolds fabrication researches, approaches to prepare small diameter multiple layered vascular scaffolds were proposed using a home-made mold by combining electrospinning, silk braiding and TIPS. Multiple layered vascular scaffolds with TPU fibrous and PPC porous structures were fabricated by altering applying electrospinning and phase separation. Furthermore, novel triple layered scaffolds with fibrous inner layer, weaving silk middle layer and porous outer layer were fabricated by using braid silk as the middle layer. The novel vascular scaffolds resembled the structure of native blood vessel, possessed desirable properties for transplant and blood flow, and supported endothelial cell attachment and growth on the inner surface which could prevent the formation of thrombus and cruor.