在組織工程中，膠原蛋白廣泛被用來當作支撐細胞生長所需的支架材料。然而最近的研究顯示，膠原蛋白基質能夠促進受損的牙髓組織的修復過程。未經處理過的膠原蛋白的穩定度，是由分子間微弱的氫鍵以及非共價鍵組成的，其鍵結導致材料具脆弱的機械性質且容易被酵素降解，因此會利用交聯劑使膠原蛋白交聯的方法去增加膠原蛋白的穩定度。戊二醛為一應用普遍的化學交聯劑，可對膠原蛋白進行化學修飾，形成穩固的交聯鍵結。另一方面，孟加拉玫瑰紅 (Rose bengal)以及核黃素 (Riboflavin)，在隨著可見光或紫外光激發下的光反應交聯也逐漸被發展。因此本研究目的為，研究以經過光反應膠原蛋白作為牙髓修復材料的生物影響。
研究第一部分檢測不同光反應之材料經過光照射後交聯的程度。將不同濃度的光反應和化學膠聯劑和膠原蛋白混合，其中光反應交聯劑利用可見光和長波紫外光誘導交聯後，再利用聚丙烯胺膠體電泳及接觸角用以分析膠原蛋白交聯之效果。結果顯示無論是經過化學或光反應的刺激下，皆能成功的使膠原蛋白交聯。
第二部分為研究不同交聯劑和不同光源的照射對牙髓細胞的影響，以及交聯後的膠原蛋白對牙髓細胞生物相容性的影響。由結果可發現，雖然不同的膠聯劑在不同天數對細胞產生毒性，但是皆在第七天後對細胞不會影響細胞的生長能力；並且在可見光或光強度較低的長波紫外光照射下，對牙髓細胞皆不會造成嚴重死亡。另外，利用交聯膠原蛋白做為基底，以MTT檢驗交聯膠原蛋白對細胞貼附和毒性的影響。經過核黃素混合長波紫外光促進交聯的膠原蛋白，和控制組與其他組相比，較有好的細胞貼附能力。然而在細胞毒性方面，經過光反應的膠原蛋白皆不會因為時間的增加對細胞產生毒性，反之普遍應用的化學交聯劑戊二醛，卻會對細胞產生明顯的細胞毒性。
最後選定0.01%的孟加拉玫瑰紅以及0.1%的核黃素，混合膠原蛋白後，分別利用可見光或紫外光促進其交聯，再進一步評估此交聯材料對於牙髓細胞分化及礦化的分析。在鹼性磷酸酶活性的測試結果得到，經過光促進交聯的膠原蛋白組別，鹼性磷酸酶活性是依時間的增加而增加，且活性都高於控制組，其中以0.01%的玫瑰紅促進交聯的組別最高。然而在礦化的分析結果發現，經由核黃素與膠原蛋白交聯的組別，有較多的礦物質小結形成，並且利用可見光促進交聯，與其他實驗組跟控制組比較，礦物質小結的生成最多。另外，以可見光與紫外光配合0.1%核黃素交聯的膠原纖維在7天後無明顯降解，且表現出較孟加拉玫瑰紅交聯組更低的金屬基質蛋白酶活性。
由以上實驗可以得知，經光活化的膠原蛋白基質是有潛力之牙髓細胞修復的材料，其中以核黃素交聯處理具有低細胞毒性，高修復能力，與抗降解能力，渴望應用於牙髓修復組織工程。

Collagen gels have been applied as a scaffold material for tissue engineering. Recent approaches have provided evidence about the use of collagen matrix promoting the reparative process of damaged dental pulp tissue. The untreated collagen is stabilized by the weak intermolecular hydrogen and noncovalent bonds, which are weak to resist the mechanical loading and easily degraded by enzyme. There have been chemical agents such as glutaraldehyde (GTA) to promote the cross-linking. Alternatively, the photo activated cross-linking by rose Bengal (RB) or riboflavin (RF) accompanying with visible light (VL) or ultraviolet (UVA) has been also developed. This study purpose was to examine the biological effects of photoreactive collagen matrix as a reparative material on dental pulp cell.
The first parts were to examine the degrees of collagen crosslinking in different photoreactive materials and chemical reagent. RB and RF were mixed with collagen and subsequently irradiated by VL and UVA. The SDS-PAGE and contact angle were used to analyze the cross-linking of collagen. The all of results showed that whether the chemical or photoreactive cross-linked were able to promote the collagen cross-linking effectively.
The next were not only to investigate the effect of cross-linking agents and light irradiation, but also to examine the cytocompatibility of cross-linked collagen on human dental pulp cells. The data demonstrated that all of the cross-linking agents did not have cell cytotoxicity to HDPCs after culture for 7 days. Additionally, neither the visible light nor ultraviolet irradiation caused cell death. We also examined the adhesion and cytotoxicity of cross-linked collagen. The RF/UVA treated collagen showed comparable cell adhesion with the control. The other side, collagen cross-linked by photochemical was not significant toxicity to HDPCs when after culture for 5 days. However, the widely cross-linker of GTA that were significant produced cytotoxicity
Finally, we chosen 0.01% RB and 0.1% RF mixed collagen, and irradiated with either VL or UVA for following differentiation and mineralization tests. The cells plated on photo-crosslinked collagen matrix exhibited high ALP activity. The highest expressed ALP activity was found in 0.01% RB group. On the mineralization assay, there appeared calcium nodules when using riboflavin to promote collagen cross-linking. However, group of RF/VL exhibited more calcium nodules after culture for 21 days. 0.01% RB also presented mionor collagen degradation after 7-day cell culture, which was contributed to the inhibited MMP activity of RF.
This study explores the potential of photoreactive collagen matrix as a reparative agent on dental pulp cells. Among the crosslinkers, RF shows low cytotoxicity, high mineralization ability, and anti-degradation ability. Therefore, the application of photo reactive collagen cross linking with RF may benefit the dental pulp regeneration.

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