Abstract: BACKGROUND: MXene nanoparticles, due to their unique hydrophilicity, biocompatibility, and antibacterial properties, are widely used in wound, tumor, nerve repair, and cardiovascular treatments. However, it is still unclear what effect MXene nanoparticles have on diabetic wound healing.
OBJECTIVE: To investigate the in vitro antioxidant, anti-inflammatory and photothermal antibacterial properties of MXene nanoparticles Ti3C2Tx as well as their effect on wound repair in diabetic mice.
METHODS: (1) In vitro experiments: The cytotoxicity of Ti3C2Tx nanoparticles on mouse fibroblasts (NIH-3T3) at various concentrations was evaluated using the methyl thiazolyl tetrazolium (MTT) assay. NIH-3T3 cells were exposed to H2O2, and the MTT assay was used to detect the protective effects of different mass concentrations of Ti3C2Tx on NIH-3T3 cells. NIH-3T3 cells were exposed to H2O2, and the effect of Ti3C2Tx (20 μg/mL) on the generation of reactive oxygen species in NIH-3T3 cells was analyzed under illumination (or no illumination) treatment. RAW264.7 macrophages were divided into three groups: control group, lipopolysaccharide group, and lipopolysaccharide+Ti3C2Tx group. Real-time quantitative PCR was used to detect the expression of specific genes (CD86, interleukin 6, CD206, arginase 1) in the cells. Escherichia coli (or Staphylococcus aureus) were divided into three groups: control group, Ti3C2Tx group, and Ti3C2Tx illumination group. The bacterial survival rate was calculated by plate colony counting method. (2) In vivo experiments: Streptozotocin was administered intraperitoneally to ICR mice to induce a diabetic condition. After successful modeling, a full-thickness skin defect wound was created on the back of the mice using a circular punch. The experiment was divided into three groups: control group (n=6), Ti3C2Tx group (n=6), and Ti3C2Tx illumination group (n=6). The wound healing was observed, and CD31 and CD206 immunohistochemical staining of wound tissue was performed on day 7 after intervention. Hematoxylin-eosin staining and Masson staining of wound tissue were performed on days 7 and 14 after intervention. Ti3C2Tx solution was injected subcutaneously into ICR mice. After illumination (or non-illumination) exposure, the toxic effects of Ti3C2Tx on mice were analyzed by blood biochemical detection. 
RESULTS AND CONCLUSION: (1) In vitro experiments: Ti3C2Tx showed no cytotoxicity on NIH-3T3 cells at mass concentrations ranging from 5-160 μg/mL. It increased the survival rate of NIH-3T3 cells at a mass concentration of 20 μg/mL. Ti3C2Tx at 10-80 μg/mL significantly improved the survival rate of NIH-3T3 cells under H2O2 intervention. Ti3C2Tx significantly inhibited the generation of reactive oxygen species in NIH-3T3 cells under the intervention of H2O2, and illumination treatment further enhanced the effect of Ti3C2Tx on inhibiting the generation of reactive oxygen species. Ti3C2Tx effectively inhibited macrophage inflammation induced by lipopolysaccharide and promoted the transformation of cells into M2 macrophages with anti-inflammatory properties. Both Ti3C2Tx and Ti3C2Tx illumination significantly inhibited the growth of Escherichia coli and Staphylococcus aureus, and the inhibitory effect of Ti3C2Tx illumination was more significant. (2) In vivo experiments: Gross and histological analyses of the wound surface showed that both Ti3C2Tx and Ti3C2Tx illumination promoted wound healing in diabetic mice, and the promotion effect of Ti3C2Tx irradiation was more significant. Immunohistochemical staining results showed that both Ti3C2Tx and Ti3C2Tx illumination inhibited the inflammatory response in diabetic wounds and promoted angiogenesis, and the effect of Ti3C2Tx illumination was more significant. Blood biochemical test results showed that Ti3C2Tx and illumination had no obvious toxic effects on mice. (3) These results indicate that Ti3C2Tx nanoparticles efficiently promote the healing of skin wounds in a diabetic mouse model through antioxidation, anti-inflammation, and antibacterial actions via photothermal effects.

Key words: Ti3C2Tx, MXene nanoparticle, diabetic wound, antioxidation, anti-inflammation, antibacterial, engineered wound material