| 摘要: | 天然高分子，例如膠原蛋白(collagen)、甲殼素(chitosan)等皆有良好的親水性質(hydrophilic)，可提 供蛋白質、細胞極佳的生長環境，然而作為生醫材料，應用於手術檯軟骨修補方面，其脆弱機械性質 無法負荷手術植入時的擠壓固定行為，合成生物可分解的高分子，例如乳酸-羥基乙酸共聚物 (PLGA)、聚己内酯(PLCL)等有良好的機械性質及可設計材料成所需求的物性，但其疏水性質 (hydrophobic)不利於細胞、組織生長。因此複合材料，例如PLGA/collagen，成為近年來許多學者研究 改良的方向，傳統方法為將兩種奈米級的固體高分子PLGA 及collagen 混合壓成複合材料 PLGA/collagen 錠或將collagen 的有機溶解液混織於PLGA 網狀支架上，再將材料放置於超臨界二氧 化碳(SCCO2)槽中，使材料中的PLGA 部分發泡產生孔洞或是將混合材料放置於鹽溶解液中再把鹽清 洗過後留下孔洞，有利於組織穿梭生長於孔洞間， 然而兩種材料PLGA 及collagen 之間的結合力不 足成為傳統方法的缺點，利用化學電漿或UV 光照方法促進結合能量(binding energy)卻會破壞部份天 然高分子 collagen 的結構，專家們努力尋求解決方法。有鑑於此，本計畫將針對生醫高分子合成核殻 複合材料(core-shell composite)的製備方法做深入的研究，此材料被廣泛應用於軟骨、支架等組織修補 移植等工程。 為了避免溶劑的殘留及綠色環境的策略，將實驗室已建立的反應設備，以超臨界二氧化碳 (SCCO2)為溶媒，進行合成製備PLGA/collagen 的複合材料，實驗策略主要是，以兩種單體乳酸(LA) 和羥基乙酸(GA)以及三甲矽烷基醯胺化鉍 (Bis)為起始劑為起始劑下反應聚合成生物可分解的高分 子聚乳酸-羥基乙酸共聚物(PLGA)為基礎材料，其中加入適量親水性高分子膠原蛋白(collagen) 及檸 檬酸(CA)作為交聯劑下進行交聯反應，經由調整組成材料的比例以達到具有目標性的核殼型結構複 合物PLGA/ collagen。第一年的研究，將已建立的超臨界流體反應設備，使用超臨界流體作為溶劑進 行一步聚合PLGA 反應，外殼部分為PLGA，其疏水及親二氧化碳性質(CO2-philic)延展在SCCO2 溶 劑中，以交聯劑Bis 的連接，核心部分為親水性collagen 高分子，傾向遠離SCCO2，生成具有核殼結 構的PLGA/ collagen 高分子複合物，且PLGA 於SCCO2 中會發泡產生小孔洞。當複合物應用於組織 修補工程時，蛋白質、組織可經由穿梭PLGA 孔洞到達collagen 表面而便利生長，並將以傅立葉轉 換紅外線光譜儀(FTIR)確認產物結構分析、掃描式電子顯微鏡(SEM)觀察複合物表面形貌及複合物 core-shell 型態、熱重分析(TGA)測量產物熱裂解溫度(Td)，產率百分比(yield percentage)計算等。本研 究第二年，進一步尋求實驗參數操作條件以及反應物用量對複合物性質影響，求取最適操作條件， 改變SCCO2 的操作參數反應溫度、壓力、時間等，對材料平均分子量(average molecular weight)，吸 水率(water uptake)，孔洞間穿透性(Pore interconnectivity)，壓縮模數(compression modulus) 測量等進 行探討。將實驗數據進行歸納分析，整理出超臨界聚合反應的研究參數關聯性與最適化關鍵因素， 並委託進行細胞毒性試驗 (cell culture cytotoxicity)實驗，測試生物組織相容性，評估實際應用的可能 性並作為相關研究的參考。
Naturally derived polymers such as collagen and chitosan have hydrophilic surfaces and specific cell interaction peptides, which are excellent for cell growth, but their weak mechanical properties make them very difficult to withstand compression when implanted into the cartilage defection. On the other hand, synthetic polymers such as copolymer poly-lactide-co-glycotide (PLGA) can easily be formed into designed shapes with relatively high mechanical strength, but their hydrophobic surface is not favorable for cell seeding. Hybrid, such as PLGA/collagen are formed for the ideal of scaffolds for tissue engineering, and the final composite scaffolds are always immersed in supercritical carbon dioxide (SCCO2) to become porous hybrid or the composites were fabricated in salt NaCl solution, such particulate leaching induced the massive formation of open pore structure for bone tissue engineering applications. Binding energy between two polymers, PLGA and collagen, are enhanced by Plasma or UV light of the final products, however, parts of the natural polymer collagen, are destroyed under such treatments. In view of these, synthesis of biodegradable PLGA/collagen core-shell composite by using the mild and advanced supercritical fluid technology is studied in this project. In the first year of study, with bismuth tris-silylamide (Bis) as initiator and citric acid (CA) as crosslinker, monomers lactide (LA) glycolide (GA), dispersed in SCCO2, as based materials are copolymerized as CO2-philic shell, PLGA . Natural polymer, collagen, is crosslinked as the contributor of the hydrophilic core, to the final product, PLGA/ collagen, biodegradable core-shell composite, and the shell PLGA will be foamed in SCCO2. Therefore, the properties of PLGA and collagen can be tuned individually. The structure of the result product can be confirmed by Fourier transform infrared spectroscopy (FTIR), SEM images will show the size and morphology of products and will observe the composite core-shell appearance, the degrading temperature of polymer is studied by TGA and the yield percentage will be calculated. In the second year, we will also investigate the effects of reaction factors. The influence of the impregnation of monomers, initiator concentration, temperature, reaction time, and conducting pressure are investigated. Furthermore, measurements of average molecular weight, water uptake, pore interconnectivity, compression modulus and cell culture cytotoxicity test will be examined in this year. The results for optimal operation conditions are expected that are valuable to future industrial applications and bone tissue engineering applications |
