用於心臟修復之生物可降解聚氨酯脲奈米纖維支架的製備與特性

Abstract

心臟衰竭為一種高死亡率的心血管疾病，透過心臟組織工程的應用，受損的心肌組織可經由心臟支架來進行取代及修復，心臟支架不僅提昇心肌組織的功能，也能改善心臟重塑。在心臟組織工程上，支架必須是具有多孔性、彈性、生物降解性、生物相容性以及相似的機械性質，以匹配原有的心肌組織。靜電紡絲為一種常用於製備成奈米纖維支架的技術，其奈米纖維支架的結構相似於細胞外基質，且具備極高的表面積與相互連通的孔洞。而聚氨酯脲為一種兼具彈性與韌性特性的合成高分子，於心臟組織工程上常被選為適合的生醫材料；乙基纖維素則為一種經由化學改質的纖維素，其展現良好的可塑性、有機溶劑溶解性、良好的生物相容性與優良的機械性質。因此，由聚氨酯脲與乙基纖維素所結合的複合生醫材料，擁有應用於心臟組織工程的前景與潛力。 在本篇論文中，我們利用聚己內酯(polycaprolactone diols, PCL diols)、異佛爾酮二異氰酸酯(isophorone diisocyanate, IPDI)與1,4-二氨基丁烷(1,4-diaminobutane, DAB)合成出生物可降解聚氨酯脲。同時透過以二甲基乙醯胺為溶劑之靜電紡絲技術，將聚氨酯脲加工為多孔纖維支架，進而探討不同纖維寬度、不同乙基纖維素混參比例、與纖維方向性的有無，對H9C2細胞(大鼠心肌細胞株)生長情形的影響。聚氨酯脲的化學結構與分子量可分別藉由傅立葉轉換紅外線光譜確認與凝膠滲透層析來進行檢測。聚氨酯脲與乙基纖維素的分子量分別為68kDa與61kDa。聚氨酯脲的熱性質、機械性質與黏彈性質顯示出其具有良好的彈性與機械強度。 本研究結果發現，較粗的纖維支架擁有較高的機械性質與降解速率，且細胞貼附生長的速率較快。我們同時混摻乙基纖維素來提高纖維支架的機械性質與生物相容性。在5:5、7:3與9:1三種聚氨酯脲與乙基纖維素的混摻比例中，是以9:1擁有較佳的細胞生長速率與形貌，此外，我們利用滾筒式收集器來製備有方向性排列結構的纖維支架，有方向性排列的纖維支架較無方向性排列的纖維支架，擁有較高的楊氏模數與拉伸強度；而相比於無方向性排列的纖維支架，在有方向性排列纖維支架上所生長的H9C2細胞，展現出更明顯的伸展形貌與排列方式。因此，有方向性排列的可降解聚氨酯脲/乙基纖維素纖維支架，可作為協助受損心肌組織修補的高潛在性生醫材料。

Heart failure is a major cardiovascular disease with high mortality. Via the application of cardiac tissue engineering, damaged myocardium can be replaced by cardiac scaffold. The cardiac scaffold can not only enhance cardiac function but also improve cardiac remodeling. In cardiac tissue engineering, scaffolds must be porous, resilient, biodegradable, biocompatible and similar mechanical properties matching with native tissue. Electrospin is a promising technique to fabricate nanofibrous scaffold which is mimic the structure of extracellular matrix (ECM) and provides high surface area with interconnecting pores. Polyurethane urea have been considered good candidates with its elasticity and toughness for utilizing in cardiac tissue engineering. Ethyl cellulose(EC) as a kind of chemically modified cellulose exhibits excellent plasticity, good solubility in organic solvents, biocompatibility and high mechanical intensity. Therefore, combination of polyurethane urea and ethyl cellulose as a composite biomaterial possesses promising potential in realistic application of cardiac tissue engineering. In this study, we have synthesized biodegradable polyurethane urea from polycaprolactone diols (PCL), isophorone diisocyanate (IPDI) and 1,4-diaminobutane (DAB) by reacting PCL diols with IPDI first then with DAB. Polyurethane urea were further fabricated into fibrous scaffolds by electrospinning using dimethylacetamide (DMAc) as a solvent. We investigated the effect on H9C2 cells growth by changing fiber width, the blending ratio of ethyl cellulose and alignment of fibrous scaffold. The chemical structure of synthesized polyurethane urea was confirmed by IR and its molecular weight was determined by GPC. The molecular weight of polyurethane urea and ethyl cellulose were 68kDa and 61kDa respectively. Their thermal, mechanical, and viscoelastic properties were also investigated to exhibit high elasticity and strength. The scaffold with wider fibers have higher tensile strength and degradation rate. More increasing cell amount rate was discovered on the scaffold with width fibers. We also blended polyurethane urea with ethyl cellulose which enhance its mechanical properties and biocompatibility. In three different blending ratio(5:5, 7:3 and 9:1), H9C2 cells exhibit better morphology and growing rate on the scaffold with 9:1 blending. In addition, we fabricated scaffold with aligned fibers by employing a rolling collector. Aligned scaffold show higher Young’s modulus and tensile strength as compared to isotropic one. The H9C2 cells cultured on aligned fibers showed more pronounced elongation and better alignment compared to those cultured on random fibers. In summary, aligned electrospun biodegradable polyurethane urea/EC scaffold has potential for the repair of damaged heart tissue.