|摘要: ||本研究利用靜電紡絲技術製備出具有多孔性及大比表面積等特點，且類似於細胞外基質 (ECM)結構之生物可分解材料，並結合具有生物相容性之Fe3O4奈米粒子，製備出兼具了生醫用途之PHB/Fe3O4及PHBV/Fe3O4功能性奈米複合纖維。|
利用掃描式電子顯微鏡 (Scanning electronic microscopy，SEM)顯示出PHB與PHBV已成功於溶劑三氟乙醇及三氯甲烷中，經由靜電紡絲法分別製備出纖維直徑分布於160 nm至660 nm及2.4μm至8.7μm之良好纖維形態。示差掃描式熱分析儀 (Different scanning calorimeter，DSC)分析PHB及PHBV結構性質差異，顯示出隨著PHV含量的增加，其吸熱熔融峰往低溫位移並伴隨焓值之降低。且X光繞射儀 (X-ray diffraction，XRD)結果亦顯示當PHV含量達12%，在電場作用下，會促使 (110)繞射峰增強。
藉由穿透式電子顯微鏡 (Transmission electron microscopy，TEM)、超導量子干涉磁量儀 (Superconducting quantum interference device，SQUID)和XRD結果顯示，成功利用高溫熱裂解法製備出具有超順磁特性之6 nm Fe3O4磁性粒子。從SEM影像顯示於靜電紡絲實驗中6 nm Fe3O4磁性粒子可良好散布於PHB及PHBV高分子中並維持良好之纖維形態。SQUID結果亦顯示複合纖維依然具有超順磁特性，而飽和磁化率皆小於3 emu/g。由DSC分析結果顯示，Fe3O4奈米粒子於溶劑三氟乙醇中，在電場作用下會促進PHB及PHBV5分子鏈之良好排列，進而使得熔點提升2℃。而從XRD結果顯示出Fe3O4奈米粒子是被包覆在纖維內部且不會影響PHB及PHBV之結晶構造。
纖維置於細菌中之體外生物降解試驗後，藉由SEM觀察結果顯示，纖維降解的發生隨著降解時間的增加，而纖維從表面開始形成微孔洞，進而纖維發生斷裂。比較不同PHV含量纖維的降解速率，在降解時間24 hr後呈現出明顯之趨勢，於溶劑三氟乙醇及三氯甲烷所得之PHB、PHBV5、PHBV12纖維殘餘量分別為94.5%、60.8%、41.3%及95.4%、34%、21.2%，顯示出PHV含量愈多降解速率越快。經由膠體滲透層析儀 (Gel permeation chromatography，GPC)結果得知，不同溶劑所製得之PHB纖維於降解實驗中分子量都有減少的情形，顯示出PHB的降解過程是由分子量開始減少，進而造成重量之損失。而PHBV5及PHBV12系統中呈現出分子量變化不大，推測是由於降解過程是從纖維表面開始分解，然而在試片的清洗過程中，表面較低分子量之纖維可能溶於水而被清洗掉，使得量測分子量所得之結果變化不大。從XRD的分析中，指出降解實驗並不會影響PHB及PHBV之結晶構造。而將纖維置於真菌中之體外降解試驗藉由SEM觀察結果顯示，纖維降解的發生隨著降解時間的增加，而纖維表面逐漸佈滿菌絲，進而導致殘於量的增加，此結果顯示真菌對於PHB及PHBV之降解速率影響並不顯著。因此，藉由本研究結果，未來可以進一步作為細胞試驗及動物試驗之參考資料。
This study is focused on the preparation of Fe3O4/poly(3-hydroxybutyrate) (PHB) and Fe3O4/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun fiber containing high porosity and surface area with interconnected pore network. The structure of prepared PHB and PHBV fibers is similar to the dimension of extracellular matrix (ECM). The electrospun Fe3O4/PHB and Fe3O4/PHBV composite fibers were achieved with biocompatibility and magnetic properties.
The micrographs of scanning electronic microscopy (SEM) illustrate that the fiber diameter was distributed in the range of 160 nm ~ 660 nm and 2.4 μm ~ 8.7 μm for PHB, PHBV5 and PHBV12 fiber in 2,2,2-trifluoroethanol (TFE) and chloroform (CHCl3) solvent, respectively. The structure and property of PHB, PHBV5 and PHBV12 fiber were investigated by different scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC results indicated that the melting endotherm slightly shifted to low temperatures as the content of PHV increased. At the same time, XRD analysis of PHBV fiber show the (110) diffraction peak became apparent with 12% PHV content under the electric field.
The monodispersed 6 nm Fe3O4 nanoparticles have been prepared through thermal decomposition process. The structure and properties of fabricated nanoparticles can be analyzed by transmission electron microscopy (TEM), superconducting quantum interference device (SQUID), and XRD. The monodispersed 6 nm Fe3O4 nanoparticles contain superparamagnetic property. The electrospun Fe3O4/PHB and Fe3O4/PHBV fiber with high porosity and surface area with interconnected pore network have been suceessfully prepared. DSC analysis of Fe3O4/PHB and Fe3O4/PHBV composite fibers fabricated in TFE solvent presence of Fe3O4 nanoparticles will promote good arrangement of the molecular chain in PHB and PHBV5 under an electric field. XRD results of the PHB, PHBV, Fe3O4/PHB and Fe3O4/PHBV composite fibers show similar tendence, which indicates the Fe3O4 does not significantly affect the crystalline structure of PHB and PHBV in the electrospinning process.
For the in vitro degradation experiments, the fibers soaked in a solution containing bacteria was observed by SEM. Experimental result showed that the structural changes of PHB and PHBV fiber occurred during the in vitro degradation, in which the fiber pore formed on the surface of PHB and PHBV. Erosion of both PHB and PHBV fibers increased with increasing incubation time. Compared to different PHV content of fiber, the SEM micrographs illustrate that the degradation rate was increased by increasing content of PHV. From the SEM results after decomposition for 2 days, the PHB fiber was significantly destroyed. Gel Permeation Chromatography (GPC) was used to investigate further the molecular weight changes of PHB. When weight percentage of molecular weight (Mw) started to decay to around 240000 ~ 230000 g/mole (after 6 hr), and the next step of degradation has been occured involving the weight loss. However, the system of PHBV showed little molecular weight changes, in which the degradation began to decompose from the surface of fibers. After the specimen was washer using water, the lower molecular weight of sample might be removed from the surface of fiber. Then the fibers soaked in a solution containing fungi in vitro degradation test showed that the fiber surface is gradually covered with mycelium as degradation time increases, which led to the residual amount. The result indicated that fungi do not significantly affect increasing the degradate rate of PHB and PHBV. These results can serve as a reference for future animal studies.