Fig. 5.

(A) Synthesis of oxidized hyaluronic acid (HA); Schiff base reaction between oxidized HA and polypeptide (ε-poly-l-lysine, EPL); thermal-responsive sol-gel process of double network hydrogel composed of F127-EPL and oxidized HA. (i) pH-dependent release profile of loaded exosomes in the FHE hydrogel. (ii) Representative images of the healing process in wounds treated with FHE, exosomes, FHE@exosome and control (Reproduced with permission of Ref. [94]). (B) Schematic diagram of the preparation and application of the PC/GO/Met hydrogel. Preparation of dihydrocaffeic acid and l-arginine cografting chitosan (CS-DA-LAG) and phenylboronic acid and benzaldehyde difunctionalized polyethylene glycol-co-poly (glycerol sebacic acid) (PEGS-PBA-BA) and polydopamine coated rGO (rGO@PDA). (iii) Schematic of self-healing, responsive drug release, and removability given by dual dynamic bonds: self-healing mechanism and representative pictures of PC hydrogel and release mechanism of metformin in response to pH and glucose and representative display pictures of removability. (iv) Representative HE staining results of wound tissue on days 3, 7, 14, and 21 (Reproduced with permission of Ref. [95]). (C)The sketch map of “Double-H bonds” in the hydrogel. (v) Live/dead staining of NIH-3T3 cells (scale bar ​= ​200 ​mm, green – live cells, and red – dead cells) and the cytoskeleton staining of NIH-3T3 cells 3D cultured in hydrogels. (vi) Drug release curves of Met from HA–COL-GMs. (vii) Migrated fibroblast staining and collagen secretion staining (Reproduced with permission of Ref. [98]).