可調控降解速率之鏈段型聚己內酯－核磁共振光譜結構鑑定與生物相容性研究

Controllable degradation behavior of segmented polycaprolactone–Structure determination by NMR and biocompatibility evaluation

楊政典(JEAN-DEAN YANG)

指導教授 ： 賈緒威

中原大學/理學院/化學研究所/博士(2019年)

https://doi.org/10.6840/cycu201900735

摘要

生物可吸收聚合物具有多種臨床應用，它們合成所需的反應方法通常需要嚴苛的反應條件和長的反應時間。本研究採用一種新的分子控制方法，將不同莫爾質量比的聚-ε-己內酯二醇(poly-ɛ-caprolactone diol, PCL diol)與4,4-二環己基甲烷二異氰酸酯[4,4'-Methylenebis(cyclohexyl isocyanate), H12MDI]-脂肪族二異氰酸酯作為偶合劑進行聚合，開發出一種新型的鏈段型聚己內酯(segmented poly-ɛ-caprolactone, SM-PCL)材料。相對於傳統的高分子量聚酯材料的聚合，本研究聚合採用DABCO/Sn(II)Oct混合觸媒系統進行聚合反應，當SM-PCL分子量Mw到達80K Da且平均反應時間約6~24hr，且僅需在常壓及低溫下即可聚合足夠高分子量的產物。
SM-A、 SM-B及SM-C三組配方進行不同純化方法評估，結果顯示單以液-液提取法(liquid-liquid extraction)，反應系統中錫觸媒的濃度由未純化時708.5ppm降至118.9 ppm。而採用索氏萃取法(soxhlet extraction)，反應系統中錫觸媒的濃度可降至49.6 ppm，且發現當錫觸媒殘留濃度低至50ppm時將難以除去。
進入動物模式講解試驗前，先行使用50±1℃加速條件下進行體外降解評估。結果顯示，降解最快之SM-A組於第10週測得分子量下降已達79.29±4.3(SM-A結晶度為40.8%)，SM-C組於第10週測得分子量下降亦達66.08±7.9(SM-C為無定形高分子)。
SM-PCL生物相容性評估部份，本研究針對固體型態SM-PCL材料以及多孔型態SM-PCL材料分別以體外細胞毒性評估以及大鼠模式長期植入分析的結果顯示， SM-PCL材料未顯示細胞毒性反應，而動物模式植入試驗顯示SM-PCL材料未導致顯著的不良病理反應並表現出良好的組織相容性。
此外，在大鼠模式長期植入降解分析結果顯示，多孔性SM-A組材料在植入大鼠組織後6個月即完全降解(P <0.01)，而一般未改性之多孔PCL均聚物直到植入12個月後分析，僅降低至初始分子量53.25%。並由植入12個月後各測試組的樣品橫截面形態觀察到，SM-A和SM-B降解與SM-C中的SM-PCL降解顯著不同。SM-A和SM-B的橫截面顯示出明顯的表面侵蝕(surface erosion)，而SM-C表現出類似大塊侵蝕(bulk erosion)的降解現像。整體研究結果亦證實，多孔和固體薄膜SM-PCL的降解率快於一般未改性PCL均聚物，並且其降解行為可予以控制。
因此，未來對於臨床上之應用，SM-PCL材料非常適合作為需要控制藥物釋放的載體或作為軟組織修復的替代材料。

關鍵字

生物可吸收聚合物 ； 偶合劑 ； 鏈段型聚己內酯 ； 降解控制

並列摘要

Bioresorbable polymers have multiple clinical applications; however, the reaction methods required for their synthesis generally require harsh reaction conditions and long reaction times. This study uses a new conceptual molecular control method that links poly–ε–caprolactone diols (PCL diol) of differing molar mass with an aliphatic diisocyanate[(4,4'-Methylenebis(cyclohexyl Isocyanate), H12MDI] as a coupling agent for polymerization to develop a new type of segmented polycaprolactone (SM-PCL) material. Relative to the polymerization of typical high molecular weight polyester materials, this research uses mixed catalyst system to polymerize. When molecular weight of SM-PCL reaches 80K Da and the average of reaction time is about 6~24 hours, this polymerization process only requires ordinary pressure and low temperature to yield product with sufficiently high molecular weight.
Evaluating SM-A, SM-B and SM-C three formulas for different purification, the result shows that liquid-liquid extraction alone reduced the concentration of tin catalyst from 780.5 ppm to 118.9 ppm when not purification. While using soxhlet extraction, the concentration of tin catalyst can be under 49.6 ppm, also finds out that when the residual concentration of tin catalyst under 50ppm, it is hard to remove.
Before animal mode trial, in vitro degradation assessment using 50±1°C acceleration in first. The result shows molecular weight of the fast degradation SM-A at the tenth week is under 79.29±4.3 (crystallinity of SM-A is 40.8%). SM-C at the tenth week is also under 66.08±7.9 (SM-C is amorphous polymer)
About biocompatibility assessment, the research focuses on solid SM-PCL and porous SM-PCL were shown by in vitro cytotoxicity evaluation and long-term implantation analysis of rat models, SM-PCL did not show a cytotoxic response, and the implantation of rat models test showed SM-PCL did not result in significant adverse pathological reactions and has good tissue compatibility.
The results of in vitro cytotoxicity and in vivo implantation assays show that the newly synthesized SM-PCL exhibits excellent biocompatibility.
In addition, in vivo degradation analyses demonstrate that the porous SM-A material was nearly completely degraded at 6 months after implantation in rat tissue (P <0.01), whereas porous PCL homopolymer was only degraded to 53.25% of the initial molecular weight even after 12 months. Observed from the cross-section of the samples of each test group after 12 months of implantation., the SM-PCL degradation of SM-C is much different than SM-A and SM-B. The cross-section of SM-A and SM-B shows obvious surface erosion. And SM-C shows a degradation like bulk erosion.
The study indicated that the degradation rates of porous and solid thin film SM-PCL were higher than those of PCL homopolymer and that its degradation behavior could be controlled.
Therefore, for clinical application, this material may be suitable as a carrier for controlled drug release or as an artificial material for soft tissue repair.

並列關鍵字

Bioresorbable polymer ； Coupling agent ； Segmented polycaprolactone ； Biocompatibility ； Controlled degradation

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