| 摘要: | 這一篇論文之研究目的在了解不同的乾燥方式對生醫高分子材料的影響。目前在實驗室中，有三種廣泛被使用的乾燥方式，包括烘箱乾燥、風乾乾燥、及冷凍乾燥等方式。因此，本研究使用了三種乾燥機，烘箱乾燥機（oven, 80℃）、常溫乾燥機（RTD, 25℃），及冷凍乾燥機（lyophilizer, -20℃）等來乾燥綠梔子素（genipin）交聯明膠（gelatin），經甘胺酸（glycine）溶液處理後之薄膜。乾燥後薄膜的物理行為（physical behaviors）、機械性質（mechanical properties）、化學特性（chemical characteristics），以及生物相容性（biocompatibility）等均作為評估的標準。
結果發現在掃描式電子顯微鏡（scanning electron microscopy, SEM）影像中，烘箱乾燥之薄膜，其斷面呈現熔融的外表；但常溫乾燥之薄膜，則呈現出一個平坦的型態；而冷凍乾燥之薄膜，則呈現一個有方向性多孔性的結構。示差掃描分析儀（differential scanning calorimetry, DSC）則顯示，薄膜經不同乾燥方式乾燥後其玻璃轉換點及熔點，從大到小為：烘箱乾燥、常溫乾燥、及冷凍乾燥；此外，在抗拉試驗（tensile tests）中，抗拉強度由大到小為：烘箱乾燥、常溫乾燥、及冷凍乾燥；在延伸率方面由大到小則為：常溫乾燥、烘箱乾燥、及冷凍乾燥。另外，衰減全反射式傅立葉紅外線光譜（attenuated total reflection Fourier transform infrared spectrometer, ATR-FTIR)分析官能基方面，並沒有明顯的不同。
從以上的結果得知，在烘箱乾燥方面，有一個變性（denaturation）與復性（renaturation）的過程，且在膠原蛋白樣三股螺旋（collagen-like triple helix）中，其螺旋間的結構，及其螺旋內（intrahelical）與螺旋間（interhelical）維繫之氫鍵（hydrogen bond）的穩定度，在乾燥過程中遭受破壞。此外，在冷凍乾燥的乾燥過程中，微細冰晶（ice crystallites）的形成，造成溶質濃度（concentration）及黏滯性（viscosity）的增加。微細冰晶的形成與昇華（sublimation），造成不同膠原蛋白樣三股螺旋間的交聯被顯著的破壞，然而卻增加在膠原蛋白樣三股螺旋，其螺旋內及螺旋間的交互作用，使螺旋間的聯結也更加地緊密。相對的，常溫乾燥，為模擬材料在室溫中經乾燥空氣乾燥的方式對其在乾燥過程中，較能保持結構上之良好。
另一方面，在組織評估方面，原本方形之薄膜植入物，其截面為長方形，經四週之降解後，其降解之殘存形狀有顯著的不同。烘箱乾燥之殘存形狀呈現橄欖形，常溫乾燥呈現紡錘形，而冷凍乾燥則呈現橄欖形與紡錘形互見。相較於烘箱乾燥與冷凍乾燥，常溫乾燥後的植入物，則發現有較高的降解度與生物相容性。
This study attempted to understand how different drying methods, including oven-drying (80℃), room temperature-drying (25℃) and freeze-drying (-20℃) methods affected the characteristics of biomaterials. Physical behaviors, mechanical properties, chemical characteristics and biocompatibility of genipin cross-linked gelatin film after drying using the three different methods were investigated.
As a result, scanning electron microscopy (SEM) images showed the oven-dried films had a fusion-like appearance in their cross section. By comparison, a flat surface morphology was seen in the materials dried by the room temperature-drying method. As for the materials dried by the lyophilizer, their cross sections became highly porous. Differential scanning calorimetry (DSC) measured the glass transition temperature and melting point of those post-dried films from high to low was the oven-drying, the lyophilizer and following the room temperature-drying method. As for the tensile test, the tensile strength from high to low was the oven-drying, the room temperature-drying and following the lyophilizer method. However, the tensile elongation from high to low was the room temperature-drying, oven-drying and the lyophilizer method. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrometer showed that there were no significant differences in functional groups among the materials dried by the three different methods. This result suggested that there could be a denaturation-renaturation procedure in the oven-dried material and the stability of the intrahelical and interhelical crosslinks of collagen-like triple helix in the material had been damaged. As for the lyophilizer-dried process, ice crystallites were formed while freezing which increased the concentration and the viscosity of the solute. Sublimation of the ice crystallites could destroy the crosslinks between the collagen-like triple helix. However, the stability of the intrahelices and interhelices of collagen-like triple helix were improved and the helices were tightly connected. By comparison, characteristics of materials dried by the room temperature-drying method were well retained.
To evaluate the biodegradation and biocompatibility of the dried genipin cross-linked gelatin films, they were implanted subcutaneously. After 4 weeks, the flat square films became olive-like and spinle-like after drying by the oven and the room temperature-drying method, respectively. Intermediate shapes were seen for the films dried by the lyophilizer. As for the biocompatibility, a thinner fibrous capsule was seen surrounding the film dried by the room temperature-drying method as compared to that dried by the other two methods. |
