本研究為在最適化條件下，以電紡製備幾丁聚醣奈米纖維，其平均直徑為178nm。我們使用兩種不同的方法來增進幾丁聚醣奈米纖維之機械特性，一是直接以紫外光照射；另一為添加了起始劑，(2,2-二甲氧基-2-苯基苯乙酮二羥甲基丙酸, DMPA）及光交聯劑(四乙二醇二丙烯酸酯, TTEGDA）於幾丁聚醣溶劑中，之後電紡絲再進行光交聯反應。
我們利用SEM、FTIR、TGA、接觸角測量及BET量測電紡絲之物理性質。添加0至50wt%之TTEGDA可成功製造光交聯幾丁聚醣奈米纖維。幾丁聚醣經光交聯反應後，以紫外光照射三小時以上，可增加幾丁聚醣奈米纖維之抗吸水性及熱穩定性，尤其在添加了光交聯劑後其性質的提升更加顯著。
體外實驗顯示，將大鼠骨瘤細胞(UMR)培養於紫外光照射與經光交聯後幾丁聚醣奈米纖維上，可提升細胞活性。這是因為經膨潤後，添加光交聯劑之幾丁聚醣奈米纖維結構可維持不變，因而使細胞活性增加。 另外由鹼性磷酸酶 （ALP）、骨鈣素（OCL）、骨涎蛋白（BSP）及第一型膠原（COL1）表現等結果顯示，添加光交聯劑之幾丁聚醣奈米纖維有促進骨分化效果。
綜合以上所述，幾丁聚醣奈米纖維經由紫外光照射及光交聯反應後，可改善其機械穩定性及抗吸水性。此外，光交聯反應可增加電紡奈米之生物相容性及骨傳導性。經實驗證實，光交聯幾丁聚醣奈米纖維為良好的生醫材料。

In this research, chitosan nanofibers were fabricated through electrospinning process under optimized conditions. The chitosan nanofibers had average diameter of 178 nm. To enhance the physical properties of chitosan nanofibers, two post-treatments were applied on chitosan nanofibers. One was the UV irradiation. The other one was photo-crosslinking with UV after photo-crosslinking agents, tetra-ethyleneglycol diacrylate (TTEGDA) and 2,2-Dimethoxy-2-phenylacetophenone (DMPA), were added into chitosan solutions used for electrospining.
Electrospun fibers were characterized with scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), water contact angle and brunauer emmett teller (BET). Photocrosslinked chitosan nanofibers were successfully fabricated with the addition of TTEGDA ranging from 0 to 50-wt %. The completion of photocrosslinking reaction on chitosan nanofibers was confirmed by FTIR and TGA after the exposure to the UV light for at least 3 hours. The exposure to UV light increased the water resistance and thermal stability of chitosan nanofibers, and the enhancement was more significant when photocrosslinking agents were added.
The culture of rat osteosarcoma cells (UMR) indicated that on UV-irradiated and photocrosslinked chitosan nanofibers, cell viability was increased. According to results of swelling tests, the structures of chitosan nanofibers would be maintained with the addition of photo-crosslinking agent, leading to the increase in cell viability. Thus, the osteogenic differentiation was also improved, including the expressions of alkaline phosphatase (ALP), osteocalcin (OCL), bone sialoprotein (BSP) and collagen type I (COL1).
In conclusion, the present research supported that the water resistance and mechanical stability of chitosan nanofibers were improved by the exposure of UV irradiation and photocrosslinking. Moreover, photocrosslinking was able to promote the biocompatibility and osteoconductivity of electrospun nanofibers. The results in this study proved that photocrosslinked chitosan nanofibers are promising materials in the biomedical applications.

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