添加咖啡酸與β-環糊精包合物之幾丁聚醣複合電紡纖維膜之製備、特性分析及生醫應用

Abstract

咖啡酸為肉桂酸的衍生物，具有良好的抗菌性質，然而其物化性質有待改善，包括溶解度、溶解速率、穩定性等等。為了提升咖啡酸的物化性質及抗菌效果，本研究使用3種方法製備咖啡酸與β-環糊精之包合物(inclusion complex, IC)，並藉由XRD、DSC、FT-IR方法證實藉由溶劑蒸發法能夠成功製備包合物。同時，包合物的形成能夠有效提升咖啡酸在pH=7.4磷酸鹽緩衝溶液中的溶解度與溶解速率：溶解度增加至1.5倍且溶解速率提升至3倍。 為了將抗菌藥物咖啡酸應用在傷口敷材，本研究使用含有生物相容性佳的天然高分子幾丁聚醣、機械性質佳的人工合成高分子聚氧化乙烯之電紡纖維膜作為咖啡酸的載體，測試在相同製程參數與環境條件下，不同咖啡酸在電紡纖維膜中的濃度對電紡製程與纖維膜的性質影響。實驗結果發現，隨著纖維膜中咖啡酸濃度的增加，電紡液的黏度會大幅下降，使得電紡製程變得愈來愈困難，電紡液液滴明顯且產率由將近9成大幅下降至不到3成。與此同時，纖維的直徑變小，機械強度變差，且纖維更加的疏水。雖說高濃度的咖啡酸有助於纖維膜的抗菌效果，使細菌存活率降至幾乎為0%。然而其過低產率使之不符經濟效益。因此後續決定選用幾丁聚醣與咖啡酸重量比1:0.001作為含有咖啡酸-β-環糊精包合物的纖維組成比例。 在最後的部分，本研究將咖啡酸-β-環糊精包合物、幾丁聚醣、聚氧化乙烯共同製備成電紡纖維膜，以期提升咖啡酸的物化性質。然而，酸性的電紡液會使得β-環糊精在電紡液配製過程中發生水解反應，產生單醣、雙醣、寡醣等醣類，連帶影響電紡液中的溶劑揮發速率下降，造成纖維中顆粒狀缺陷結構增加。同時，纖維的產率減少、機械強度也不佳。在抗菌方面，由於β-環糊精會水解成細菌所需的糖類，反倒促進了細菌的增生。 綜上所述，雖然β-環糊精的包合能夠有效提升咖啡酸的溶解度及溶解速率，理應能有效提升咖啡酸的抗菌效果。然而當咖啡酸-β-環糊精包合物應用在幾丁聚醣電紡纖維製程時，酸性電紡液卻會使得β-環糊精水解成醣類，反而促進了細菌的繁殖。因此未來如果要製備含有咖啡酸-β-環糊精包合物的電紡纖維膜，可以考慮選用中性的溶劑進行電紡液的配製。如此一來，應能將完整的包合物連同高分子一同電紡成纖維膜，並有效提升藥物的抗菌效果，以期能發展成為具有臨床應用價值的傷口敷材。

Caffeic acid is a derivative of cinnamic acid, which has good antibacterial properties, but its physicochemical properties need to be improved, including solubility, dissolution rate, stability, and so on. To improve the physicochemical properties and antibacterial activity of caffeic acid, three methods were used in this study to prepare the inclusion complex (IC) of caffeic acid with β-cyclodextrin. Later, some techniques like XRD, DSC, and FT-IR were applied to confirm that the IC could be successfully prepared by solvent evaporation method. Besides, the formation of inclusion complex could effectively improve the solubility and dissolution rate of caffeic acid in pH=7.4 phosphate buffered saline: the solubility increased to 1.5 times and the dissolution rate up to 3 times. In order to apply the antibacterial drug caffeic acid to wound dressings, this study used an electrospun fiber membrane containing natural polymer chitosan with good biocompatibility and synthetic polymer poly(ethylene oxide) with good mechanical properties as the carrier of caffeic acid. Under the same process parameters and environmental conditions, the effects of different concentrations of caffeic acid in the electrospun fiber membrane on the electrospinning process and the properties of the membrane were tested. The experimental results showed that as the concentration of caffeic acid in the fiber membrane increased, the viscosity of the electrospinning solution would drop significantly, making the electrospinning process more difficult. The droplet of the electrospinning solution was obvious and the percentage yield decreased from nearly 90% to less than 30%. Meanwhile, the diameter of the fiber became smaller, the mechanical strength became worse, and the membrane possessed more hydrophobic. Although the high concentration of caffeic acid contributed to the better antibacterial activity of the fiber membrane, where the bacterial survival rate was reduced to almost 0%. However, its low percentage yield made it uneconomical. Therefore, it was later decided to choose chitosan and caffeic acid at a weight ratio of 1:0.001 as the composition ratio of fibers containing caffeic acid-β-cyclodextrin inclusion complex. In the final part of this study, caffeic acid-β-cyclodextrin inclusion complex, chitosan, and poly(ethylene oxide) were co-prepared into an electrospun membrane for the purpose of enhancing the physicochemical properties of caffeic acid. Nonetheless, the acidic electrospinning solution would lead to the hydrolysis of β-cyclodextrin into sugars like oligosaccharides during the preparation process of the electrospinning solution, which would decrease the solvent evaporation rate of the electrospinning solution, resulting in an increase of some defects like beaded structures in the fibers. At the same time, the yield of the fiber was reduced and the mechanical strength turned out to be poor. As for the antibacterial activity, since β-cyclodextrin underwent hydrolysis into sugars required by bacteria, it would actually foster the proliferation of bacteria. In summary, although the inclusion of β-cyclodextrin can effectively improve the solubility and dissolution rate of caffeic acid, it should be able to enhance the antibacterial activity of caffeic acid. However, when the inclusion complex was used in the electrospinning process, the acidic solution would hydrolyze the β-cyclodextrin into sugars, which in turn promoted the reproduction of bacteria. Therefore, if electrospun membranes containing caffeic acid-β-cyclodextrin inclusion complex are to be prepared in the future, neutral solvents can be considered for the preparation of electrospinning solutions. In this way, it may be possible to electrospin the inclusion complex together with the polymer into membrane, and effectively improve the antibacterial effect of the drug, so as to be developed into a wound dressing material with clinical application value.