自組裝幾丁聚醣-硼酸水凝膠作為可3D列印葡萄糖敏感水凝膠之動態交聯劑

Abstract

幾丁聚醣水凝膠由於生物相容性，在生醫材料與組織工程等領域中受到廣泛關注。然而，其親水性差、高含水量與脆性，導致機械穩定性不足及列印精度低，限制其在3D列印應用上的發展。本研究在幾丁聚醣的胺基上修飾，合成出約25%取代率的羧基苯硼酸幾丁聚醣（簡稱 CB）高分子，藉由原位小角度 X 光散射（SAXS）與流變分析探討其水溶液中的自組裝行為。研究結果顯示，CB鏈段 (10萬Da) 會形成具連續排列特性的聚集結構，自組裝結構的回轉半徑（Rg）約為3.5 nm。然而單獨CB自組裝形成的水凝膠結構脆弱，作為3D列印墨水缺乏足夠的列印後支撐力容易導致塌陷。Polyethylene glycol diacrylate (PEGDA) 與 Dithiothreitol (DTT) 單體以逐步成長聚合生成 Poly(ethylene glycol)-Dithiothreitol (PD) 高分子，經由CB上的硼酸與PD鏈段上的二醇生成硼酸酯鍵產生動態交聯，有效的提升水凝膠的彈性，形成具更佳延展性與結構穩定性的PB水凝膠。SAXS結果進一步驗證，增加CB含量有助於強化水凝膠結構，並在PB動態網絡中生成較大的物理聚集體（Rg約為8.5 nm），改善機械特性與列印精度。流變分析則顯示PB水凝膠具剪切稀化與自癒合性質，能以內徑210 m噴嘴穩定擠出並形成連續線條。此外，PB水凝膠中物理聚集與動態共價鍵之間的協同作用在列印建構體中的可堆疊特性扮演重要因素，使列印後形成的高堆疊立方體在列印過程中不易坍塌，並且建構體在列印後30分鐘仍可維持設計高度（1.2 cm）的95%。藉由台盼藍釋放和茜素紅 S (ARS) 複合物競爭實驗定量顯示出 PB 水凝膠的葡萄糖敏感性。此葡萄糖敏感特性的PB水凝膠，結合CB賦予的3D堆疊能力，展現製備三維葡萄糖感應結構之生物墨水的潛力，未來可望應用於生醫領域。

Chitosan-based hydrogels have attracted interest in biofabrication and tissue engineering due to their biocompatibility. However, their poor water solubility, high water content, and brittleness lead to weak mechanical stability and low printing fidelity, limiting their use in 3D printing. In this study, we synthesized carboxylphenylboronic acid (CPBA)-grafted chitosan (CB) polymer with ~25% substitution degree. Through in situ small-angle X-ray scattering (SAXS) and rheological analyses, CB revealed self assembly behavior in aqueous solution where the chains formed clusters (radius of gyration Rg ~3.5 nm) in successive arrangement. CB self-assembled hydrogels, however, were structurally fragile. The incorporation of linear diol-containing poly(ethylene glycol) (PD) into the CB network enhanced elasticity by crosslinking via boronate ester linkage, yielding a PB hydrogel with enhanced pliability and structural stability. SAXS profiles verified that increasing CB content reinforced hydrogel structure, forming larger physical clusters (Rg ~8.5 nm) within PB dynamic network to improve the mechanical behavior and printing fidelity. Rheological analysis demonstrated shear-thinning and self-healing properties, enabling continuous filament deposition when printed using a 210 µm nozzle. Meanwhile, the synergistic balance between physical clusters and dynamic covalent bonding in PB hydrogel facilitates high stackability of a 3D-printed tall cuboid to maintain ~95% designed height (1.2 cm) without post-printing reinforcement. Trypan blue release and ARS complex competition experiments quantitatively displayed the glucose sensitivity of PB hydrogels. This glucose-sensitive PB hydrogel, leveraging CB-mediated 3D stackability, can serve as a promising bioink for fabricating 3D glucose-responsive architectures for biomedical applications.