Fig. 2: Characterization of ROS-responsive hydrogel as a vehicle for loading PTβR2I peptide.

a Chemical structure of polymer (NIPAAm-co-HEMA-co-AHPPE) and its accelerated degradation with ROS. The final degraded product is soluble in body fluid. b The hydrogel solution is flowable and injectable at both 4 °C and 12 °C, and quickly forms a solid gel at 30 °C and 37 °C. c Retention of PTβR2I encapsulated in the developed hydrogel in the wound area after 24 h, observed using IVIS, with comparative collagen gel retention results. d Quantification of drug retention by relative ROI intensity derived from IVIS images (n = 3). e Degradation of the hydrogel in PBS with or without 1 mM H₂O₂ for 14 days. A non ROS-responsive hydrogel was used as a control. f In vitro total antioxidant capacity of the hydrogel. g Cytotoxicity of different concentrations of the degraded product to dermal fibroblasts, was evaluated by MTT assay (n = 4). h In vivo biocompatibility of the ROS-sensitive hydrogels, examined by F4/80 staining (green) on tissue samples with subcutaneously injected hydrogel after 7 days. Nuclei were stained with DAPI (blue). i Quantification of F4/80⁺ cell ratio based on the images (n = 5). j In vitro release profiles of 3 different concentrations of PTβR2I in ROS-responsive gel for 21 days (n = 4). k Bioactivity of PTβR2I released from ROS-responsive gel at days 3, 8, and 14 (n = 5). All data are shown as mean ± standard deviation. Data were analyzed by one-way ANOVA with the Bonferroni post-test (n.s. p > 0.05, *p < 0.05).