Reduce Graphene Oxide-loaded Silver And Antibiotic Nanocomposites Combined In Anti-bacteria And Promoting Wound Healing In Mice

Bacterial infection has become one of the most serious risks in public health,especially resistant bacterial infection have reduced the antibacterial efficiency of conventional antibiotics.Therefore,developing a new generation of antibacterial agents or the introduction of new antibacterial models has become an urgent need in this field.In recent decades,antibacterial nanomaterials have shown great potential for anti-bacterial infection,and are considered to be the most promising antibacterial materials to overcome the problem of the resistance of bacteria,which has practical application prospects.At the same time,nanocomposite antimicrobials with multiple antibacterial properties help multi-targets against more stubborn drug-resistant bacteria and become an important development direction in the field of antibacterial.In this thesis,the antibiotic of daptomycin and nano-antibacteria of silver nanoparticles were used as antibacterial agents,and the high specific surface area of??reducing graphene oxide was used as carrier to construct an active antibacterial nanocomposite,which was used for antibacteria and wound infection treatment.The main research contents are as follows:(1)Preparation of daptomycin-silver nanoparticle co-loaded nanocomposites.First,silver nanoparticles(AgNPs)were synthesized in situ on the surface of reduced graphene oxide(rGO),followed by covalent bond of daptomycin to form a daptomycin-silver nanoparticle co-loaded nanocomposite(rGO@Ag@Dap).The synthesis process and results of nanocomposites were characterized by a series of methods of characterization(such as UV-Vis,AFM,TEM,SEM,Zeta,FT-IR,XPS,XRD,Raman).The SEM results show that the particle size of rGO@Ag@Dap is about70 nm,and the silver nanoparticles are uniformly distributed on the surface of reduced graphene oxide(rGO).FT-IR results indicate that daptomycin is conjugated to reduced graphene oxide(rGO)by a strong covalent bond(amide bond).The results show that the nanocomposites of reduced graphene oxide with silver and antibiotics were successfully prepared.(2)Analysis of in vitro antibacterial activity of nanocomposites.By using experiments of filter paper inhibition zone,minimum inhibitory concentration(MIC),and bacterial growth curve,rGO@Ag@Dap was studied for antibacterial properties against Gram-negative bacteria(Escherichia coli and Pseudomonas aeruginosa)and Gram-positive bacteria(Staphylococcus aureus and Bacillus subtilis).The results show that rGO@Ag@Dap has stronger antibacterial ability against Gram-negative bacteria and Gram-positive bacteria than other nanomaterials,and the minimum inhibitory concentration was 10.8?g/mL and 9.8?g/mL,respectively.(3)Research on antibacterial mechanism of nanocomposites.By using experiments of high reactive oxygen species(ROS)level,ATP level and bacterial apoptosis,the antibacterial mechanism of nanocomposites may be due to the release of Ag~+to destroy cell membranes,lead to the leakage of cell contents;further induce the production of ROS and ATP,which can cause confusion of cellular metabolic activity,thereby killing bacteria.(4)Nanocomposites are used to treating mouse infection.After investigating the cytotoxicity and hemolysis experiments of mouse fibroblasts(NIH-3T3)to verify the biocompatibility of nanocomposites,the nanocomposites were used for the treatment of bacterial infections of mouse skin wounds.The results show that rGO@Ag@Dap can be the most effectively kill bacteria on the wound and further promote skin regeneration and dense collagen deposition,thereby improving wound bacterial infection and accelerating wound healing,which indicates that nanocomposites have better antibacterial and anti-infective properties.