Recent advances in hyaluronic acid hydrogels for biomedical applications.

Hyaluronic acid (HA) is widely used in the design of engineered hydrogels, due to its biofunctionality, as well as numerous sites for modification with reactive groups. There are now widespread examples of modified HA macromers that form either covalent or physical hydrogels through crosslinking reactions such as with click chemistry or supramolecular assemblies of guest-host pairs. HA hydrogels range from relatively static matrices to those that exhibit spatiotemporally dynamic properties through external triggers like light. Such hydrogels are being explored for the culture of cells in vitro, as carriers for cells in vivo, or to deliver therapeutics, including in an environmentally responsive manner. The future will bring new examples of HA hydrogels due to the synthetic diversity of HA.