添加聚山梨醇酯20之聚氧化乙烯/幾丁聚醣-明膠同軸電紡奈米纖維膜製備及其對於疏水性藥物釋放之改善

Abstract

奈米纖維膜具有高比表面積、高孔隙度等特性，利於細胞貼附、物質傳遞，而以同軸靜電紡絲法可製備具核/殼雙層結構的纖維，核層可保護藥物、殼層可增加質傳阻力而使核層所含藥物緩釋，殼層若選擇具生物相容性、親水性的生醫材料，則此同軸纖維適合作為藥物載體。 本研究以靜電紡絲(簡稱電紡)法製備同軸複合奈米纖維，選擇無毒性、電紡性佳的聚氧化乙烯(PEO, 簡稱P)作為核層材料，幾丁聚醣(chitosan, 簡稱C)、明膠(gelatin, 簡稱G)、阿拉伯膠(gum Arabic, 簡稱GumA)及聚山梨醇酯20 (Tween 20, 簡稱T)作為殼層材料，並且採用較為安全無毒、對環境友善之醋酸水溶液(acetic acid, 簡稱Ac)作為溶劑，上述材料除具有一定機械強度外，也囊括親水性、抗菌性、細胞相容性佳等優點，期待製備出良好的藥物載體。 首先將電紡參數設定於電壓25 kV，藉由調整核/殼層溶劑、殼層聚山梨醇酯20 (可促進藥物釋放)與阿拉伯膠(可降低溶液黏度)含量，在不同的核/殼層流量與收集距離下進行最佳化參數的探討。當核/殼層黏度差異太大時，核層黏滯力過大而影響殼層溶液，無法順利電紡成絲，也為了避免針尖分相的疑慮，核殼層使用相同溶劑是為穩健的選擇。而殼層溶劑若為濃度20 wt%之醋酸水溶液時，聚山梨醇酯20添加量不同並不會對殼層溶液的黏度、表面張力與導電度有太大影響，顯示此含有幾丁聚醣的複合溶液的性質容易掌握。另外，本研究亦藉由微調阿拉伯膠含量以改變殼層幾丁聚醣複合溶液之黏度，使電紡製程可穩定大量地生產同軸纖維。本研究發現若電場強度或核/殼層流量過大，容易有纖維粗細不均、堆疊雜亂的情形發生，是故需選擇適當的收集距離與核/殼層流量。 經多次試驗，本研究發現以同軸複合溶液：核層為6 wt%的聚氧化乙烯溶於20 wt%的醋酸水溶液，殼層為8 wt%的幾丁聚醣、8 wt%的明膠、1 wt%的聚山梨醇酯20及0.4 wt%的阿拉伯膠溶於20 wt%的醋酸水溶液(核/殼層溶液組成縮寫為P6Ac20/C8G8T1Ac20GumA0.4)，並設定電紡參數：施加電壓25 kV、收集距離25 cm、核/殼層溶液流量為0.3/0.3 mL/h及0.3/0.6 mL/h，可成功地製備同軸電紡纖維膜，並可長時間穩定地得到均勻的奈米纖維，其直徑各為725 ± 77 nm及804 ± 145 nm。將同軸奈米纖維膜材以紅外線吸收光譜進行官能基分析，結果顯示同軸纖維膜確實同時含有核層及殼層的材料成分，保有其原本之特性；將纖維膜以戊二醛進行不同時間的交聯反應，測定膜材的機械性質，隨著交聯時間增加，將可提升前述兩種不同核/殼流量膜材的抗拉強度至190.59 ± 18.67 N/mg及252.62 ± 11.38 N/mg；另將膜材浸於PBS中進行崩解性測試，未經交聯的膜材殘存重量僅剩45%，而隨著交聯時間提升，殘存重量也能逐步地提升至65-70%，綜合上述機械性質與崩解性的實驗結果，選擇前述兩組不同核/殼流量同軸奈米纖維(0.3/0.3 mL/h及0.3/0.6 mL/h組別)的交聯時間分別為1.5小時及1小時。經交聯的膜材因保有表面纖維狀孔洞結構，使得原本親水的材料將變得更為親水，因此水下氣泡接觸角由128.8° ± 4.0°提升至134.3° ± 2.9°。 最後將同軸纖維核層裝載疏水性藥物薑黃素進行藥物釋放測試，結果顯示本研究製備之同軸纖維因含有聚山梨醇酯20 (一種界面活性劑)，不僅提升薑黃素於PBS中溶解度數倍達到15 ppm以上，也能因殼層的存在造成質傳阻力而減緩薑黃素釋放速率，約4天後達平衡。 總結來說，本研究成功製備出帶有界面活性劑(聚山梨醇酯20)的同軸奈米纖維，此纖維膜材不但具有較高的抗拉強度、水相穩定性及細胞相容性，更具有提升疏水性藥物(薑黃素)於水相的溶解度以及延緩藥物釋放的功能，是非常具有潛力的生醫材料及藥物載體。

Nanofiber membrane is known for its high specific surface area and porosity, so it is used in various applications, such as wound dressing, cell scaffold and drug carrier. In this research, coaxial nanofiber membranes were prepared by electrospinning. Poly ethylene oxide (PEO, P) is chosen as core material, whereas chitosan (C), gelatin (G), gum Arabic (GumA) and Polysorbate 20 (Tween 20, T) compose shell solution. PEO is an artificial polymer that has good mechanical properties and electrospinnability. Chitosan and gelatin have good antibacterial property, hydrophilicity and biocompatibility. Furthermore, a small amount of gum Arabic can significantly decrease the solution viscosity, so it is used to manipulate viscosity of shell solution. Tween 20 is a non-toxic surfactant that can improve the solubility of hydrophobic drug. Initially, applied voltage was fixed at 25 kV, various core/shell solutions were prepared and electrospun into coaxial nanofibers under different working distances and flow rates. When core solution was composed of 6 wt% PEO, shell solution containing 8 wt% chitosan, 8 wt% gelatin, 1 wt% Tween 20 and 0.4 wt% gum Arabic in 20 wt% acetic acid aqueous solution, coaxial nanofibers with good fiber structure were successfully and continuously fabricated under 25 kV, working distance of 25 cm and core/shell solution flow rates 0.3/0.3 mL/h and 0.3/0.6 mL/h. The diameters of fibers were 725 ± 77 nm and 804 ± 145 nm, respectively. With adequate crosslinking by glutaraldehyde (GA), tensile strengths of nanofiber membranes mentioned above increased to 190.59 ± 18.67 N/mg and 252.62 ± 11.38 N/mg. In the same time, crosslinked nanofiber membranes could remain their weights up to 65-70% in PBS buffer, whereas uncrosslinked ones would lose half of their weights. Also, the hydrophilicities of nanofiber membranes could be improved due to their rough surfaces. Curcumin was then loaded into the core layer as a model hydrophobic drug. Release profiles showed that with addition of Tween 20 could increase the solubility of curcumin substantially, i.e., from 5 ppm to 15 ppm or more. In addition, the shell layer created mass transfer resistance and thus burst release was not observed. The release profile reached equilibrium after 4 days. In summary, this research successfully fabricated coaxial nanofibers containing surfactant for drug release enhancement. The nanofiber membranes had proper tensile strength and aqueous stability. They can be used to improve the solubility and controlled release of hydrophobic drug, so they have the potential to become biomaterials and drug carriers.