2016 Macromolecules
ABSTRACTMetal complexation–based gelation imparts load-bearing hydrogels with striking properties like reversibility, self-healing, and mechanical tunability. Using bio-inspired metal-catechol complex, the former properties have been introduced to a variety of polymer hydrogel, except hyaluronic acid which was widely used in biological applications. In this research, we developed two different kinds of hyaluronic acid (HA) hydrogel with 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 coupling reaction were selectively applied for different gelation. Phase-changeable HA-CA gel was attributed to dominant Fe3+–catechol coordination with immediate pH control. On the other hand, allowing curing time to form catechol coupling bonds resulted in color-changeable HA-CA gels with pH control, in which the gel structure is preserved by means of dual crosslinking by 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 from marine mussel cuticle. The present gelation strategy is expected to broaden the utility of HA hydrogels in biological applications, offering easy control over phase, gel network, and viscoelastic properties