Thermosensitive, injectable, biocompatible epigallocatechin gallate liposomes/modified chitosan composite hydrogel for efficient skin repairing

Epigallocatechin gallate (EGCG) exhibits remarkable bioactivities, notably enhancing wound healing via keratinocyte activation and re-epithelialisation. However, its susceptibility to oxidation restricts its efficient application. To address this, this study aims to improve its stability and bioavailability by integrating EGCG liposomes (ELSm) with N-isopropylacrylamide (NIPAM)-modified chitosan (CS) hydrogel (TSCN). Specifically, the TSCN2/5 hydrogel with a mass ratio of CS/NIPAM of 2/5 is injectable and can undergo a reversible phase transition around 30.4 °C, which also exhibits a good adhesive strength of 36.73 kPa. The ELS1 liposomes (the mass ratio of lecithin/cholesterol/EGCG is 40/10/3) demonstrate good stability and encapsulation efficiency, with a particle size of about 110 nm and an encapsulation efficiency of about 85%. Cellular experiments reveal that ELS1 and TSCN2/5 are non-toxic to cells, and the ELSCN hydrogel (composite of ELS1 and TSCN2/5) can increase the expression of peroxisome proliferator-activated receptor-alpha (PPAR-α) protein in skin repair. Animal experiments demonstrate that ELSCN with a high concentration of EGCG can promote wound healing by reducing skin inflammation, boosting collagen synthesis, facilitating epidermal repair and promoting granulation tissue formation. Consequently, this composite hydrogel will be used as a coating for efficient skin wound repair.