Fig. 3.

Schematic representation of the preparation of in situ cross-linked hydrogels as injectable matrices via physical and chemical cross-linking reactions. Cross-linking strategies are determined for each hydrogel system. The left side indicates physical cross-linking, and the right side indicates chemical cross-linking reactions. Horseradish peroxide (HRP), β-cyclodextrin-modified hyaluronic acid (CD-HA), ferulic acid (FA), methacrylate gelatin (Gel MA), gelatin grafted with ferulic acid (GtnFA), hyaluronic acid (HA), matrix metalloproteinase (MMP). Duplicated with permission from Ref [3]. Copyright © 2018, John Wiley and Sons