由於幾丁聚醣 (Chitosan, CS)水膠對細胞外基質 (Extracellular matrix, ECM)表現出良好的仿生性 (Biomimetics)、細胞親和力 (Cell affinity)、抗菌特性 (Antibacterial properties)和可控的生物吸收能力 (Bioresorbability)，現今已於生物醫學應用領域備受關注。當水膠材料與3D列印技術結合時，可大規模製造精確且高度客製化的多孔結構，使CS水膠於生物醫學領域的應用更為廣泛。然而，傳統CS水膠離子交聯使列印效率不足以應用於商業的3D列印程序，機械強度差、穩定性差和重現性差等缺點限制CS水膠於3D列印領域的發展。因此，本研究應用交聯劑和加速反應以改善3D列印CS水膠。
在第一部分中，本研究將使用交聯劑處理CS水膠以提高CS的黏度與分子間作用力，藉此提升於3D列印中的列印分辨率 (Resolution)與成膠 (Gelation)速度。首先將交聯劑與加速劑混和均勻後，接著將水膠裝於5 mL針筒以進行3D列印程序，並加熱收集槽以加速固化反應。結果顯示提高溫度與材料濃度後，成膠時間縮短99.23%，列印結構的形變量減少63.23%，適印性提升至1.0，顯示此材料為理想的可列印材料。骨母細胞 (7F2)的細胞活性測試結果證實CS與CS/交聯劑水膠皆具有良好的生物相容性 (Biocompatibility)。
在第二部分中，將目標藥物Doxycycline (Dox)直接混入CS水膠支架進行3D列印，設計多種多孔支架結構並對藥物釋放支架變因做探討，以控制藥物釋放速率。結果顯示透過增加阻擋層 (Barrier Layers)厚度、緻密度、曲折度以及無載藥水膠緻密度，可有效延長藥物釋放時間。抗菌測試的結果同樣證實增加阻擋層孔隙率能有效延緩釋放時間並達到抑菌效果。此外，長期藥物釋放的結果顯示牛血清蛋白 (BSA)於第5天時出現最高釋放量79.19%，之後至14天時釋放少量的BSA，證實CS水膠多孔支架能夠作為長效型給藥的載體。

The chitosan (CS) hydrogel has gained significant attention due to its ability to exhibit biomimetic properties to extracellular matrix (ECM), excellent cell affinity, antibacterial properties, and controllable bioresorbability. When combined with 3D printing (3DP) techniques, hydrogel materials enable the fabrication of accurate and highly customized porous structures on a large scale, opening up numerous possibilities for biomedical applications. However, the conventional ionic-crosslinking solidification of CS hydrogel has proven to be inefficient for commercial 3DP processes. The limitations of poor mechanical strength, inadequate stability, and inferior reproducibility hindered the advancement of CS hydrogel in 3DP. To address these challenges, this study focuses on the application of the crosslinker and an accelerated reaction to enhance the 3DP of CS hydrogel.
In the first part of the study, the crosslinker was added to the CS solution. The addition of the crosslinker had a significant impact, increasing the viscosity and intermolecular forces of CS. This, in turn, enhanced the printing resolution and gelation speed in the 3DP process. Two solutions, one containing the crosslinker solution with accelerated agents and the other containing pre-crosslinked CS solution, were blended and then loaded into a 5 mL syringe for the 3DP process. To expedite the solidification reaction, the collector was heated. The results demonstrated a 99.23% reduction in gelation time, a 63.23% decrease in the deformation of printed structures, and an improved printability rating of 1.0 under optimized temperature and concentration conditions. These findings indicate that the optimized formulation serves as an ideal printable ink. Furthermore, the cell culture experiments using osteoblast cells (7F2) confirmed the excellent biocompatibility of both CS hydrogel and GP crosslinked CS hydrogel.
In the second part of the study, the CS hydrogel scaffolds were loaded with Doxycycline (Dox) for the 3DP process. Various porous structures were designed, and the factors influencing drug release rates were investigated to achieve controlled release. The results of the release experiments indicated that the duration of drug release could be effectively prolonged by increasing the thickness, density, and tortuosity of the barrier layers, as well as the density of the drug-free hydrogel. Antibacterial tests also confirmed that increasing the density of the barrier layers could delay the release duration and achieve an antibacterial effect. Moreover, the long-term release results revealed that 79.19% of BSA (bovine serum albumin) was released within 5 days, gradually releasing small amount of BSA until 14 days. These findings demonstrate the capability of CS hydrogel porous scaffolds to function as long-term drug delivery carriers.

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