Metal complexation-based gelation imparts load-bearing hydrogels with striking properties like reversibility, self-healing, and mechanical tunability. Using a bio-inspired metal–catechol complex, these properties have been introduced to a variety of polymer hydrogels, except hyaluronic acid, which is widely used in biological applications. In this research, we developed two different hyaluronic acid (HA) hydrogels by regulating the gelation kinetics of Fe³⁺ and a catechol cross-linker, including Fe³⁺-induced covalent bonding and coordination bonding. Dual roles of Fe³⁺ in catechol-modified HA (HA-CA), Fe³⁺–catechol coordination, and catechol oxidation followed by a coupling reaction were selectively applied for different gelations. Phase-changeable HA-CA gel was attributed to dominant Fe³⁺–catechol coordination with immediate pH control. Alternatively, allowing a curing time to form catechol coupling bonds resulted in color-changeable HA-CA gels with pH control. The gel structure is then preserved by dual cross-linking through covalent catechol-coupling-based coordinate bonds and electrostatic interactions between Fe³⁺ and HA-CA. The hydrogels showed enhanced cohesiveness and shock-absorbing properties with increasing pH due to coordinate bonds inspired by marine mussel cuticles. The present gelation strategy is expected to expand the utility of HA hydrogels in biological applications, offering easy control over the phase, gel network, and viscoelastic properties.

中文翻译：

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铁（III）离子-邻苯二酚的相控透明质酸水凝胶利用凝胶动力学的间隙诱导双重交联

基于金属络合的凝胶化赋予承重水凝胶惊人的性能，如可逆性，自愈性和机械可调性。通过使用生物启发性的金属-邻苯二酚络合物，这些特性已被引入多种聚合物水凝胶中，透明质酸除外，而透明质酸已广泛用于生物应用中。在这项研究中，我们通过调节Fe ³⁺和邻苯二酚交联剂（包括Fe ³⁺诱导的共价键和配位键）的凝胶动力学，开发了两种不同的透明质酸（HA）水凝胶。Fe ³⁺在邻苯二酚修饰的HA（HA-CA），Fe ^3+中的双重作用-邻苯二酚配位，以及邻苯二酚氧化和偶合反应被选择性地应用于不同的胶凝作用。相变HA-CA凝胶归因于主要的Fe ^3+-邻苯二酚与pH的直接控制。或者，允许固化时间形成邻苯二酚偶联键，导致可控制pH的颜色变化的HA-CA凝胶。然后通过基于共价邻苯二酚偶联的配位键和Fe ³⁺之间的静电相互作用的双重交联来保留凝胶结构和HA-CA。由于受海洋贻贝角质层启发而形成的配位键，随着pH值的增加，水凝胶显示出增强的内聚性和减震性。预期本凝胶化策略将扩大HA水凝胶在生物应用中的用途，并提供对相，凝胶网络和粘弹性特性的轻松控制。