Tailored Thermosensitive Hydrogel Delivering Niobium Carbide Boosts For Diabetic Wound Healing

ObjectiveThe treatment of diabetic wounds is difficult due to high levels of oxidative stress,susceptibility to bacterial infections,and prolonged inflammation response during the healing process.In the present study,an injectable niobium carbide-based hydrogel system（Nb₂C@Gel）was developed by implanting niobium carbide nanosheets（Nb₂C NSs）within a thermosensitive hydrogel.Our objective was to investigate the ROS scavenging capability of Nb₂C NSs and the antibacterial effect of photothermal therapy in vitro.We also aimed to explore the protective effect of Nb₂C NSs against ROS-induced oxidative damage and determine the underlying mechanisms.Lastly,we evaluated the biosafety of Nb₂C@Gel and its therapeutic potential in treating diabetic wounds.MethodsNb₂C NSs and PLGA-PEG-PLGA triblock copolymers were characterized.The in vitro photothermal transduction effect and the H₂O₂,O₂^·-and·OH elimination efficiency of Nb₂C NSs were tested.The photothermal antimicrobial activity of Nb₂C NSs against both Staphylococcus aureus（S.aureus）and Escherichia coli（E.coli）was assessed using the live/dead bacterial staining assay,plate count method,and scanning electron microscope（SEM）.The biocompatibility of Nb₂C NSs and Nb₂C@Gel was evaluated by in vitro cytotoxicity and hemocompatibility assays.Nb₂C NSs were labeled with Cy5 dye to observe the uptake of Nb₂C NSs by wound cells.The oxidative stress cell model was constructed by hydrogen peroxide（H₂O₂）.The cell activity and intracellular reactive oxygen species（ROS）levels were detected by Calcein AM/PI staining,CCK-8 assay,and ROS fluorescence probe（DCFH-DA）.The regulating effect of Nb₂C NSs on the apoptosis signaling pathway was evaluated by JC-1 mitochondrial membrane potential dye,flow cytometry and western blot.The microstructure,forming time,temperature sensitive properties,mechanical properties and photothermal properties of Nb₂C@Gel were characterized.The liver hemorrhage models were constructed to evaluate the hemostatic performance of Nb₂C@Gel.The in vivo toxicity of Nb₂C@Gel was evaluated by blood routine index,blood biochemical index and organ histological staining.The diabetic wound model and the infected wound model in mice were constructed.The effect of Nb₂C@Gel on wound healing was evaluated by HE staining,Masson staining,ROS probe（DHE）staining and immunofluorescence staining.ResultsNb₂C NSs and Nb₂C@Gel showed good biocompatibility.In vitro experiments showed that Nb₂C NSs could efficiently eliminate ROS.Meanwhile,Nb₂C NSs could protect cells from oxidative stress damage by reducing intracellular ROS levels,inhibiting mitochondrial membrane potential decline,and inhibiting cell apoptosis mediated by mitochondrial pathway.Secondly,Nb₂C NSs also exhibited good photothermal antimicrobial activity against both S.aureus and E.coli,and realized low-temperature sterilization.The injectable Nb₂C@Gel system also showed excellent hemostasis in a liver hemorrhage model.In mice with diabetic wounds,Nb₂C@Gel could promote wound healing by relieving oxidative stress,scavenging ROS,eliminating bacterial infection with synergistic photothermal action at low temperatures,attenuating the inflammatory response,and thereby accelerating angiogenesis,epithelialization,and collagen deposition.Conclusions:An injectable thermosensitive Nb₂C-based hydrogel system（Nb₂C@Gel）was successfully constructed.This system could eliminate bacterial infection at low temperatures,efficiently eliminate ROS,resist oxidative stress,inhibit cell apoptosis,and effectively promote diabetic wound healing.Collectively,the study provides a new strategy for the treatment of diabetic wound nonunion.