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  細菌感染是傷口愈合和皮膚再生過程中最常遇到的問題，因感染引起的嚴重炎癥反應不僅顯著增加感染相關的并發癥，而且明顯降低傷口愈合的質量。此外，細菌感染性慢性傷口治療難度大、療程長、費用高，給患者和社會造成巨大的經濟負擔。目前，臨床上主要使用抗生素治療感染性傷口。但是，因耐藥性和缺乏合適的皮膚修復微環境，抗感染和傷口愈合的治療效果并不理想。因此，如何有效抵御多藥耐藥性細菌感染并同時促進感染性傷口愈合和皮膚再生仍是目前亟需解決的一大難題。針對上述問題，西北工業大學張秋禹教授團隊將具有優異電導率、良好生物相容性和較強抗菌能力的二維（2D）Ti₃C₂T_x MXene引入多功能水凝膠支架（HPEM）用于耐甲氧西林金黃色葡萄球菌（MRSA）感染的傷口愈合研究。

Scheme 1. Scheme showing the fabrication and application of HPEM scaffolds in multidrug-resistant bacteria infected wound healing.

  通過合理的結構設計制備得到的HPEM支架具有多功能特性，包括自愈合、較高的導電性、組織粘附性、快速止血能力和較強的抗菌性，尤其是對耐多種常用抗生素的MRSA，其抗菌活性高達99.03%。（Fig. 2和3）。

Figure 2. Multifunctional properties evaluations of scaffolds. (A) Rheological analysis of the HPEM scaffolds at 4℃, 25℃ and 37℃; (B-C) rheological data and rheological recovery rate of HPEM scaffolds under alternating high (1000%) and low shear strain (1%); (D) viscosity of HPEM scaffolds at different shear rate; (E) electronic conductivity of HPEM scaffolds and controls; (F) the normal stress to the adhesive ability of HPEM scaffolds determined by the TA rheometer (*p<0.05, **p<0.01, n=3); (G) the images of the HPEM scaffolds forming; (H) pictures of the self-healing of HPEM scaffolds.

Figure 3. Antibacterial activity and hemostatic ability assay. (A) Bacteria clones and bacterial viability (B) against E. coli, S. aureus, and MRSA treated with different samples; (C) total blood loss and photographs from the damaged livers after 60 s treated with HPEM scaffolds and control (*p < 0.05, **p < 0.01, n=3).

  為了進一步驗證該HPEM支架的體內外生物效應，分別進行了體外細胞實驗和動物實驗。細胞實驗表明：HPEM支架可有效促進小鼠成纖維細胞（L929）增殖，細胞毒性較低；而且，可促進皮膚修復相關基因（α-actin、collagen type III和VEGF）的表達，顯示出了顯著的促進皮膚缺損再生的生物學性能（Fig. 4和S7）。

Figure 4. Cytotoxicity and cell proliferation evaluations of scaffolds. (A) Cell viability of HPEM scaffolds and each composite in L929 cells at different concentrations for 24 h; (B) LIVE/DEAD staining images of L929 cells at 1 d, 3 d and 5 d after treated with HPEM scaffolds and controls (10 μg/mL) (live cells: green, dead cells: red, scale bar: 100 μm, n=3); (C) fluorescence intensity of L929 cells treatment with HPEM scaffolds and controls at 1 d, 3 d and 5 d (*p<0.05, **p<0.01, n=5). Cells without any treatment was used as negative control (NC).

  在動物試驗中建立MRSA感染的皮膚全層切除模型，并將該多功能支架填充于缺損部位。研究發現該支架通過有效的抗炎作用、促進細胞增殖和血管生成過程、刺激肉芽組織形成、膠原蛋白沉積、血管內皮分化和血管生成，可顯著促進MRSA感染的傷口愈合（愈合率為96.31％）（Fig. 5和6）。

Figure 5. In vivo anti-infection and MRSA-infected wound healing. (A) Representative skin wound images at 0 d, 3 d, 7 d and 14 d, and (B) wound area size of the HPEM scaffolds and controls (*p < 0.05, **P < 0.01); (C) images of MRSA colonies growing on the agar plates derived from the homogenized infected tissues after various treatments at 3 d, 7 d and 14 d; (D) quantitative bacterial colonies densities based on (C); (E) IL-6 (red) immunofluorescence images at 3 d, H&E and Masson’s trichrome staining of wound tissues at 14 d, the black arrows showed the granulation layers in wound beds; Corresponding quantification of (F) fluorescence intensity of IL-6, (G) granulation tissue thickness and (H) collagen content in wound tissues based on (E) (Scale bar =100 μm, n = 6;*p < 0.05 and **p < 0.01).

Figure 6. Immunohistochemistry and immunofluorescence staining of wound healing assay. (A) Immunohistochemistry of Ki67, α-SMA stained (red: α-SMA, blue: nuclei) and CD31 stained (green: CD31, blue: nuclei) images; (B-C) quantitative analysis of α-SMA and CD31 of wound tissues at 7 d, respectively (scale bar = 100 μm; n = 6; *p < 0.05 and **p < 0.01).

  本研究表明多功能Ti₃C₂T_x MXene@聚多巴胺納米片在感染性傷口愈合中的重要作用。此外，具有多功能特性的HPEM支架為MRSA感染的傷口愈合/皮膚再生提供了一種潛在的治療策略。

  以上相關成果分別發表在ACS Nano (2021, DOI: 10.1021/acsnano.0c06287)上。論文的第一作者為西北工業大學化學與化工學院博士后周麗，通訊作者為張秋禹教授。

  論文鏈接：https://doi.org/10.1021/acsnano.0c06287