Orange Peel Pectin-Functionalized Schiff Base Hydrogel Ameliorates Wound Healing via Regulating M2 Macrophage-Polarization: Insights from In Vitro and Zebrafish Model Studies

Impaired macrophage polarization is one of the primary factors that hinders the healing of chronic wounds. A bioinspired hydrogel comprising amidated pectin (AmPT) and dialdehyde carboxymethylcellulose (DCMC) reinforced with honey was reported for wound healing. Pectin was obtained from orange peels via microwave-assisted extraction and further subjected to amidation. The hydrogels were constructed by the Schiff base reaction between the amino groups of AmPT and the aldehyde groups of DCMC. The hydrogels incorporated with the highest honey content, i.e., HH3 hydrogel, exhibited higher thermal stability, tensile strength, and anti-inflammatory and antioxidant properties. A controlled release drug profile for curcumin was evidenced in the colorectum from the HH3@Cur hydrogel, and the release kinetics indicated the anomalous nature of release. An enhanced migration and proliferation of 3T3 fibroblasts was marked for HH3@Cur. The wound closure was noted at almost 92% for the HH3@Cur hydrogel after 24 h. The q-PCR analysis revealed that the expressions of IL-4, IL-13, and PPAR-γ were upregulated in the HH3@Cur-treated group, indicating that it efficiently promoted macrophage transition from pro-inflammatory M1 to anti-inflammatory M2 phenotypes associated with improved wound repair. Furthermore, the HH3@Cur hydrogel was explored for microtissue formation and wound healing application using a zebrafish model, which aligned with in vitro data. Herein, by 16 dpw, the wound closure rate marked to 92.8% for HH3@Cur hydrogel in comparison to the control group (71.5%), and the mean mRNA expressions of IL-4, IL-13, and PPAR-γ were upregulated accordingly. Overall, the results indicated that HH3@Cur hydrogel ameliorates wound healing by influencing the expression of biomarkers related to inflammation, macrophage polarization, and angiogenesis.