Design And Fabrication Of Novel Antibacterial Nanomaterials For Staphylococcus Aureus Infections

In recent years,the emergence of drug-resistant bacteria caused by the abuse of antibiotics has increased the difficulty of clinical treatment of bacteria infections and has seriously threatened human life and health.Therefore,the development of new treatment methods for bacteria infections is urgently needed.With the emergence and rapid development of nanotechnology,a few nanomaterials have shown good antibacterial effects and have been used in the field of antibacterial.In this thesis,we designed and constructed two types of antibacterial nanomaterials against the clinically common pathogenic Staphylococcus aureus(S.aureus),and studied their antibacterial properties.This work can be divided into the following two parts:1.It has been reported that graphene and silver nanoparticles have good antibacterial effects,but the antibacterial effect and mechanism of their nanocomposites need further study.GO-Ag nanocomposites were obtained by growing silver nanoparticles on graphene oxide(GO).Antibacterial experiments have shown that,GO-Ag nanocomposites exhibited good antibacterial ability,and could effectively inhibit bacterial activity at the concentrion of 10?g/mL.We further studied the antibacterial mechanism.It was found that after treatment with GO-Ag nanocomposites,the division of S.aureus was effectively inhibited,but a large number of bacterial death were not observed and its cell wall and genomic DNA remained intact.After removing the GO-Ag nanocomposite,S.aureus can resume their division and growth.After treatment with chemical mutagens,no detectable resistance of S.aureus against GO-Ag nanocomposites could be induced.2.It has been reported that photodynamic therapy(PDT)can be used to treat local infections caused by bacteria,such as abscesses,but the hypoxic microenvironment of the abscess site limits the efficacy of PDT.Thus,we designed and synthesized manganese dioxide nanoparticles loaded with Ce6(Ce6@MnO2-PEG),which can catalyze the release of oxygen from hydrogen peroxide in the abscess microenvironment to improve the hypoxic microenvironment and enhance the photodynamic efficacy.In vitro antibacterial studies have shown that in 50 ?M hydrogen peroxide,Ce6@MnO2-PEG can effectively improve the hypoxic environment and enhance the photodynamic sterilization effect.The in vivo antibacterial activity of Ce6@MnO2-PEG-based PDT was tested in mice using a S.aureus-induced skin abscess infection model.The results showed that Ce6@MnO2-PEG could indeed lead to relieve of the hypoxic state of the abscess,subsequently resulting in greatly enhanced in vivo PDT-induced bacteria killing and obviously improved abscess recovery.In summary,this thesis presents two novel high-efficiency antibacterial nanocomposites,characterized and tested their antibacterial properties:a new bacteriostatic agent GO-Ag nanocomposites to inhibit the growth of S.aureus and a novel antibacterial strategy of photosensitizer-modified MnO2 nanocomposites to enhance photodynamic therapy of abscess.Our work could be useful for the research and development of new antibacterial agents.