以分子動力模擬探討甲基丙烯酸酯改質結冷膠在不同濃度與取代度下之分子結構、交互作用與機械性質

Abstract

結冷膠具有優異的生物相容性、生物可降解性與可調控之機械性質，為組織工程應用中常用之材料。為進一步提升其機械與生物性質，透過甲基丙烯酸酐與結冷膠結合進行改質，可獲得具有光交聯能力之甲基丙烯酸酯改質結冷膠。經紫外線照射與交聯作用後，其機械性質與生物相關特性可進一步增強。本研究以分子動力學模擬方式，探討不同分子濃度與甲基丙烯酸酯取代度對結冷膠與其改質系統之分子結構、分子間作用與機械性質的影響。模擬結果顯示，濃度增加有助於強化分子間作用力，促進分子鏈之聚集與纏繞，並提升機械強度；而取代度提升則使甲基丙烯酸酯基團加強分子內作用力，抑制分子間以及與水的交互作用，導致材料疏水性提升。交聯模擬結果顯示，交聯主要發生於不同分子鏈間之甲基丙烯酸酯基團，交聯鍵數隨濃度與取代度上升而增加。交聯後，分子結構與交互作用與交聯前趨勢相似，且各系統之分子內氫鍵以及與水形成之氫鍵均顯著下降，在低取代度系統中更為明顯，並伴隨聚合物鏈更加蜷曲及分子間氫鍵數量減少。在機械性質方面，高濃度與中等取代度之交聯甲基丙烯酸酯改質結冷膠系統則展現出最佳之抗壓縮性能，剪切強度亦隨濃度提升而上升，且隨著取代度的提升於中、高取代度條件下有明顯上升，而低取代度則略有下降。黏度亦隨濃度上升而增加，且大致隨著取代度的提升而增加。綜合而言，本研究由微觀尺度出發，深入探討結冷膠與其甲基丙烯酸酯改質系統在不同濃度與取代度條件下之分子結構、交互作用以及機械性質間的關係，為未來結冷膠水凝膠於生醫領域之應用提供重要理論依據。

Gellan gum exhibits excellent biocompatibility, biodegradability, and tunable mechanical properties, and serves as a fundamental material for tissue engineering applications. By modifying gellan gum with methacrylic anhydride, methacrylated gellan gum can be obtained. Upon UV exposure and cross-linking, along with increases in concentration and methacrylate degree of substitution, its mechanical performance and biological characteristics can be further enhanced. In this study, we employed molecular dynamics simulation to analyze the molecular structure, intermolecular interactions, mechanical properties, and the effects of molecular concentration and methacrylate degree of substitution on gellan gum. Our results show that increasing concentration strengthens intermolecular interactions, promotes chain aggregation and coiling, and improves tensile strength. As the methacrylate degree of substitution increases, intramolecular interactions are enhanced, while both intermolecular interactions and interactions with water are reduced, due to the presence of methacrylate groups. Furthermore, we investigated the structural and interaction changes following crosslinking. Crosslinking primarily occurred between methacrylate groups on different chains, and the number of crosslinks increased with both concentration and degree of substitution. After crosslinking, molecular structures and interactions remained similar to those observed before crosslinking. Intramolecular hydrogen bonding and hydrogen bonding with water decreased across all systems. These effects were more prominent in low-substitution systems, which showed more coiled chains and fewer intermolecular hydrogen bonds. In terms of mechanical properties, crosslinked methacrylated gellan gum exhibited improved compressive resistance at higher concentrations and moderate substitution. In addition, shear strength increased with concentration and improved with substitution, except at low substitution. Viscosity increased with concentration and generally with substitution. This study provides a microscopic perspective to elucidate the structure-interaction-mechanical property relationships of gellan gum and methacrylated gellan gum, offering valuable insights into the rational design of gellan-based hydrogels for biomedical applications.