以靜電紡絲技術製作聚氨酯/乙基纖維素混紡之組織框架應用於心肌組織修復

Abstract

心肌梗塞與充血性心臟衰竭為死亡率極高的心血管疾病，然而，隨著生醫材料的開發與應用，心臟組織工程支架逐漸成為重要的治療策略。心臟組織工程支架需有以下要求，包含多孔性，彈性，生物相容性和與心肌組織相似的生物機械性等。靜電紡絲是一種具發展潛力的技術，其所製造的奈米纖維在結構上與自然的細胞外基質結構相似，並且具有極高的表面積與體積比和相互連通的孔洞。在這篇論文中，我們將呈現我們成功利用靜電紡絲技術開發出以聚氨酯/乙基纖維素混合物為材料的組織工程支架。藉由調控與優化靜電紡絲的操作參數，我們可以控制並得到直徑100奈米至1微米的纖維。與純聚氨酯相比，適當的聚氨酯/乙基纖維素比例可提高組織工程支架的機械性能，包括拉伸強度和楊氏係數，且同時保有良好的伸長率和彈性。此外，在體外培養試驗中，H9C2細胞（大鼠心肌細胞株）在所有比例的組織工程支架上皆有隨時間增長之趨勢，顯示此材料具生物相容性。我們也系統性地探討纖維寬度對於細胞生長的影響，藉由培養H9C2細胞株在不同直徑纖維的組織工程支架上，我們發現纖維狀的結構比起平面的培養皿可促進較多的細胞貼附，且較寬的纖維可更明顯的發現細胞擴展的速度較快，顯示其在心臟組織工程支架的應用上更具適用性。 除了隨機排列的組織工程支架外，我們藉由滾動式的收集器引導纖維，並成功開發出具有特定方向性排列的組織工程支架。此具有方向性排列的組織工程支架較隨機排列的組織工程支架展現出更佳的機械性能，包括較高的楊氏係數和拉伸強度。此外，方向性排列的組織工程支架亦加強了H9C2細胞的增生能力，並且引導細胞往纖維的方向生成長條狀形態，此形態與隨機排列的組織工程支架上所觀察到的平面細胞形態有相當大的差異。本論文所呈現的研究成果，對目前的生物支架技術有顯著的提升與貢獻，期待於本論文所開發出的生物支架可於未來被實際運用於心臟組織工程上。

Myocardial infarction (MI) and congestive heart failure (CHF) are major cardiovascular diseases with high mortality rates. Via the discovery and application of biomaterials, cardiac patch tissue engineering has become an advanced strategy for surgical intervention of MI and CHF therapy. The criteria of scaffold for cardiac patch tissue engineering include porous, elastic, biocompatible and mimic biomechanical properties of the cardiac muscle. Electrospin is a promising technique to fabricate nanofibrous scaffold which is structurally similar to the native extracellular matrix (ECM) and provides high surface‐to‐volume ratios with interconnected pores. In this thesis, we demonstrate a successfully developed scaffold utilizing electrospin technique based on polyurethane / ethyl cellulose (PU/EC) blends. The fiber diameters can be well controlled in the range of 100 nm to 1 μm by rationally tuning the processing parameters of electrospin. The developed scaffold features significant mechanical properties and biocompatibility. Namely, as compared to the pristine PU scaffold, adjusting the blending ratio of PU/EC could enhance the mechanical properties including tensile strength and Young’s modulus but still remain high elongation and flexibility. Additionally, the in vitro test of culturing the H9C2 cells (rat cardiomyocyte cell lines) on scaffolds showed the increasing cell amount over time in all types of scaffolds, indicating their good biocompatibility. Furthermore, the relation between fiber width and cell growth was also systematically studied by culturing H9C2 cells on scaffolds with different diameters. The fibrous structure was found to facilitate the cell adhesion and spread in the beginning 4 hours as compared to the flat tissue-culture polystyrene (TCPS). More pronounced spread rate was discovered in the scaffold with wider fibers, which suggests the more potential applicability in cardiac patch tissue engineering. In additional to the scaffold with randomly oriented fibers, we also successfully developed scaffold with aligned fibers by employing a rolling collector which guided the fiber deposition. Such scaffold showed considerably improved mechanical properties including higher Young’s modulus and tensile strength as compared to the isotropic one. The proliferation of H9C2 cell was also enhanced on aligned fibers with elongated morphology along fiber direction which is distinctive to the flat morphology observed in scaffolds with isotropic fibers. The present thesis extends the current technology in the scaffold development which possesses promising potential in realistic application of cardiac patch tissue engineering.