Synergistic Antibacterial Strategy Of Carbon Nanomaterials And Piptides Based On Cell Membrane Disturbance Mechanism

Bacterial infection has long been a global public health problem.With the extensive use of antibiotics,the problem of bacterial resistance is becoming more and more prominent.The emergence of superbugs has taken the world by storm,and the slow development of antibiotics has forced a shift in research toward developing new strategies to fight them.Nanomaterials have proven to have great potential for antibacterial activity.Among the antibacterial nanomaterials,carbon-based nanomaterials have attracted much attention due to their unique physical and chemical properties,and good biocompatibility.However,the antibacterial ability of pure carbon-based,nanomaterials is limited,so it is necessary to combine them with other materials to exert antibacterial effect.Since the carbon materials can disturb the bacterial membrane,similar to the disturbance caused by some natural amphiphilic antimicrobial peptides(AMPs)when they form pores in the membrane,we suspect that the combination of carbon materials and AMPs can achieve enhanced antibacterial efficiency.In this work,two typical types of carbon materials including the graphene oxide(GO)and fullerene(C60),and two typical AMPs including the natural peptide,Melittin(Mel),and the clinical available peptide,polymyxin B(PMB),are combined through pretreatment or chemical bonding,for the development of a novel synergistic antibacterial strategy based on physical attacking.Moreover,the antibacterial mechanism of the synergistic disturbance of bacterial cell membranes by carbon materials and AMPs is revealed by using a variety of live bacterial and model membrane experiments.a variety of antibacterial experiments were used to confirm the synergistic antibacterial properties between carbon nanomaterials and peptides,and the antibacterial mechanism was studied by combining model membrane and biocompatibility experiments.Subsequently,we used this collaborative strategy to design a carbon-peptide system more suitable for clinical use,and combined with a variety of methods to study its antibacterial effect and mechanism.The main contents of each part of this paper are as follows:In Chapter 1,we introduced the background,research progress and membrane disturbance mechanism similarity between carbon nanomaterials and antimicrobial peptides.The second Chapter introduced the main experimental instruments and methods used in this paper.In Chapter 3,we discussed the main role of carbon nanomaterials(fullerenes(C60)and GO)in synergistic interaction with membrane active molecules.We proved that C60 and GO can change the phospholipid arrangement of the model membrane and bacterial membrane to damage its integrity,and this effect was similar to the effect of Mel before perforation on the membrane.GO showed excellent synergistic performance in both models,but C60 only enhanced the permeation effect of Mel on model cell membrane,while the effect on living bacteria and mammalian cells was just the opposite.In Chapter 4,we extended this synergistic effect ell membranes verify the good biocompatibility of the GO-PMB complex.The synergistic effect of GO and PMB in disturbing the lipid membranes is proved by the experiment.In Chapter 5,we summarized includes summary and forecast of the whole thesis.In a word,the work of this thesis develops a kind of synergistic antibacterial strategy of carbon nanomaterials and peptides based on the physical attacking mode.Since the disturbance of the membrane is very microscopic,the sensitivity of Mel to the membrane is first used to quantify the disturbance degree of the membrane.The synergistic effect of carbon nanomaterials and Mel was evaluated by changing the minimum concentration of Melittin(Mel),a representative membrane pore-forming peptide.In addition,by comparing the different effects of GO and C60 at the same concentrations on the membrane activity of Mel,this work shows that the effect of carbon nanomaterials cooperating with membraneactive molecules to destroy bacterial membrane depends on the physical and chemical properties of the materials.At the same time,using the amplification effect of membraneactive peptide Mel on the structural defects of lipid membranes,this work obviously demonstrates the structural disturbance of carbon nanomaterials at low concentrations(generally considered with no biological toxicity)on cell membranes,and emphasizes the importance of carefully examining the biological toxicity of nano materials.This paper was emphasized that the effect of carbon-based nanomaterials on the destruction of bacterial membrane depends on its physicochemical properties.Using the difference between bacterial membrane and cell membrane,synergistic antibacterial nanomaterials with high antibacterial activity and low biotoxicity can be prepared.This paper provided an effective strategy for dealing with bacterial infection and the development of bacterial resistance,and was of great significance for understanding the mechanism of interaction between antibacterial nanomaterials and cell membranes.