Construction Of Antibacterial Gauze By In-situ Reduction Of Silver Nanoparticles By Quercetin

Objective The new antimicrobial gauze is loaded with antimicrobial agents onto the matrix gauze material,thus ensuring the continuous release of antimicrobial agents at the wound to control wound infection and promote wound healing.Silver nanoparticles（Ag NPs）have been widely studied and applied because of their strong antimicrobial properties,and their long-lasting and broad-spectrum antimicrobial properties are also suitable for research related to antimicrobial coatings on the surfaces of various biological materials.Quercetin,one of the polyhydroxyflavonoids,has the strongest biological activity among flavonoids.It is widely found in flowers,roots,stems,leaves and fruits of plants in nature.It readily forms complexes with a variety of metals and can be used as a reducing and stabilizing agent in the biosynthesis of silver nanoparticles.Therefore,the synthesis and stabilization of silver nanoparticles need to be piggybacked onto the surface of medical gauze with the help of quercetin as a cross-linked coating.The aim of this study is to propose a process for the rapid and green preparation of silver nanoparticles（Ag NPs）coating on the surface of gauze,and to evaluate its antibacterial efficiency and biocompatibility,so as to lay the foundation for further improvement and application of the process.Methods We used the property that quercetin is soluble in alkaline solution but insoluble in acid solution to form a uniform amorphous inclusions layer on the surface of gauze by alkali-acid redeposition,immersed it in silver nitrate solution,and used the reducing properties of hydroxyl groups in quercetin to reduce silver ions in situ on its surface to form nano-silver particles,and prepared nano-silver coated gauze with antibacterial efficacy（quercetin-nano-silver composite antibacterial gauze CG-Q/Ag_x,x is the concentration of silver nitrate solution,unit is mg/ml）.The standard curve of the purchased quercetin was plotted by UV spectrophotometer and the amount of quercetin carried was calculated;the surface morphology and silver nanoparticle distribution of the samples were observed by scanning electron microscopy（SEM）and X-ray energy spectroscopy（EDS）,and the elemental composition of the gauze surface coating was analyzed by X-ray photoelectron spectroscopy（XPS）.The antibacterial properties of CG-Q/Ag were evaluated by inhibition ring test and turbidity method.The cytotoxicity of CG-Q/Ag was evaluated by CCK-8 method.The number and morphology of L-929 cells were observed under an inverted microscope using crystalline violet staining.We established a rat dorsal total cortical wound model and took photographs of the rat dorsal wounds at 7,10 and 14d postoperatively to calculate their wound healing rate and evaluate the pro-healing effect of CG-Q/Ag.Subsequently,the whole cortical tissue of the rat dorsal wounds was taken and the histopathological changes at the wounds were observed by HE staining.Results SEM observation results showed that a smooth quercetin coating was formed on the surface of the coated group gauze,and Ag NPs were successfully piggybacked on the surface of the quercetin coating by in situ reduction reaction;SEM and EDS results showed that the Ag NPs of CG-Q/Ag group were successfully mounted on the surface of gauze fibers and uniformly distributed,and the silver particles were of nanometer size.The antibacterial results showed translucent inhibition rings around CG-Q/Ag_0.5and CG-Q/Ag₁groups in the inhibition ring test;the inhibition rate of CG-Q/Ag_0.5and CG-Q/Ag₁was>63%in the turbidity test.We found good biocompatibility of CG-Q/Ag_0.5in the CCK-8 method.In the experiment on the effect of promoting wound healing,the healing rate of the CG-Q/Ag group was83.57±3.74%on postoperative day 7,which was significantly higher than that of the blank gauze group at 43.60±6.08%（P<0.0001）.The HE staining results showed that CG-Q/Ag was able to promote fibroblast growth and vascular system neogenesis during the wound healing process and promote tissue repair.Conclusion In this study,we successfully formed a uniform quercetin coating on the gauze surface rapidly by using the alkali-acid redeposition method,and obtained CG-Q/Ag by in situ reduction of Ag⁺to Ag NPs on the gauze surface by soaking in silver nitrate solution,which is a simple,rapid,environmentally friendly and efficient process.This surface modification method not only inhibits bacterial adhesion on the gauze surface,but also inhibits the proliferation of bacteria around the gauze,avoiding the infection caused by the migration of surrounding bacteria during the wound healing process and promoting the wound healing,which has good biocompatibility while achieving effective antibacterial ability.This strategy of constructing quercetin coatings by alkali-acid redeposition and in situ reduction of silver nanoparticles provides a new technical idea for surface modification of gauze.