One way of tailoring the properties of hydrogels is using functional cross-linkers. In this study, four highly water-soluble and degradable carboxylated diacrylate and diacrylamide macromeric cross-linkers were designed as precursors to prepare pH-sensitive and degradable hydrogels. The macromers were synthesized from thiol-Michael addition reaction of meso-2,3-dimercaptosuccinic acid (DMSA) with poly(ethylene glycol) diacrylate (PEGDA, M_n = 575 g/mol) or N,N′-methylene bis(acrylamide) (MBA) in the presence of triethyl amine or sodium hydroxide. They were used as cross-linkers in fabrication of 2-hydroxyethyl methacrylate (HEMA)-based hydrogels, whose swelling strongly depended on pH, macromer structure, and hydrogel composition. The degradabilities of the hydrogels were greatly enhanced by increasing the concentration of the cross-linkers. The mechanical properties of the hydrogels can be tuned by tailoring the cross-linking macromer. The hydrogels were proven to have metal chelating ability in the context of Fe³⁺ ions, and upon this chelation, Young’s modulus was also observed to increase significantly. In vitro cytotoxicity evaluations against U-2 OS human bone osteosarcoma epithelial cells and C2C12 mouse myoblast cells showed that the PEGDA functional macromers are not toxic.

中文翻译：

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用于 pH 敏感可降解水凝胶的内消旋 2,3-二巯基丁二酸大分子单体

调节水凝胶性能的一种方法是使用功能性交联剂。在这项研究中，设计了四种高水溶性和可降解的羧化二丙烯酸酯和二丙烯酰胺大分子交联剂作为前体来制备pH敏感和可降解的水凝胶。大分子单体是通过内消旋2,3-二巯基丁二酸（DMSA）与聚乙二醇二丙烯酸酯（PEGDA，M _n = 575 g/mol）或N , N'-亚甲基双（丙烯酰胺）的硫醇-迈克尔加成反应合成的。 ）（MBA）在三乙胺或氢氧化钠存在下。它们被用作制造基于甲基丙烯酸 2-羟乙酯 (HEMA) 的水凝胶的交联剂，其溶胀很大程度上取决于 pH 值、大分子单体结构和水凝胶组成。通过增加交联剂的浓度大大增强了水凝胶的降解性。水凝胶的机械性能可以通过定制交联大分子单体来调节。^{水凝胶被证明在Fe 3+}离子的情况下具有金属螯合能力，并且在这种螯合后，还观察到杨氏模量显着增加。针对 U-2 OS 人骨骨肉瘤上皮细胞和 C2C12 小鼠成肌细胞的体外细胞毒性评估表明，PEGDA 功能性大分子单体无毒。