Abstract: BACKGROUND: Inflammation, oxidative stress and bacterial infection are the main causes of delayed wound healing in diabetes. In recent years, various inorganic nanomaterials have been widely used in the treatment of skin wound healing due to their antibacterial activities, but their effects on anti-oxidation and anti-inflammation are limited.
OBJECTIVE: To investigate the effect of Prussian blue nanoparticles on the wound repair of diabetes in terms of antioxidant, anti-inflammatory and photothermal antibacterial activities.
METHODS: Prussian blue nanoparticles were prepared and characterized. (1) In vitro: The biocompatibility of Prussian blue nanoparticles with different concentrations was detected by MTT assay. The cytoprotective effect of Prussian blue nanoparticles and the intracellular reactive oxidative species level were examined under the condition of hydrogen peroxide. The ability of Prussian blue nanoparticles to decompose hydrogen peroxide and superoxide anion radicals was tested; the effect of Prussian blue nanoparticles on lipopolysaccharide-induced macrophage inflammation was investigated. The photothermal antibacterial activity of Prussian blue nanoparticles was detected by the plate colony counting method. (2) In vivo: ICR mice were intraperitoneally injected with streptozotocin to establish a diabetes mouse model. After the model was successfully established, a 6 mm wound was created on the back with a hole punch. There were the control group (no treatment), the Prussian blue group and the Prussian blue with light group. The wound healing and histomorphological changes were observed.
RESULTS AND CONCLUSION: (1) In vitro: Prussian blue nanoparticles in 25-200 μg/mL were non-toxic to cells. Prussian blue nanoparticles had the extremely strong antioxidant capacity and mitigated the intracellular reactive oxidative species at a high oxidative stress environment, resulting in a pronounced cytoprotective effect. The Prussian blue nanoparticles not only exhibited hydrogen peroxide degradation activity but also showed strong superoxide scavenging ability. Prussian blue nanoparticles also displayed significant anti-inflammatory activity and extremely strong antibacterial ability after light irradiation. (2) In vivo: After 14 days, the wound sizes of the Prussian blue group and Prussian blue with light group were significantly reduced, and the healing speed of Prussian blue with light group was the fastest. Hematoxylin-eosin and Masson staining showed a lot of granulation tissue formation and collagen deposition in the Prussian blue group and the Prussian blue with light group, of which the Prussian blue with light group was the most. Immunofluorescence staining displayed that, compared with the control group, the expressions of α-SMA and CD31 were increased significantly in Prussian blue group and Prussian blue with light group (P < 0.05), but F4/80 expression was decreased significantly in Prussian blue group and Prussian blue with light group (P < 0.05), indicating more obvious improvement in the Prussian blue with light group. (3) These results showed that Prussian blue nanoparticles could promote the skin wound healing of the diabetes mouse model by exerting anti-inflammatory, antioxidant and antibacterial effects.

Key words: Prussian blue nanoparticle, photothermal treatment, diabetic mouse model, reactive oxygen species clearance, macrophage polarization, wound healing