Application And Mechanism Studies Of Cell Membrane-targeting Antibacterial Molecules In The Inhibition Of Complex Bacterial Infections

The misuse and abuse of antibiotics have led to the emergence of a large number of super-resistant bacteria.Infections caused by multidrug-resistant(MDR)bacteria have been proposed by both the World Health Organization and the Chinese Center for Disease Control and Prevention as a major global health problem.The complex infection environment in vivo,represented by bacterial biofilm formation and acidification of the infection microenvironment,is an important reason for pathogenic bacteria to cause serious infections in the human body.Compound molecules with bacterial cell membrane targeting as the main antibacterial mechanism have the advantages of strong bactericidal ability and low drug resistance,and are expected to provide an effective solution to the above-mentioned complex bacterial infections in vivo.Therefore,in view of the two biological problems of bacterial biofilm formation and infection microenvironment acidification,this project uses cell membrane-targeted antibacterial molecules as the compound skeleton,and has carried out the following two aspects of work:(1)In the treatment of bacterial biofilm infection: First,this project screened the oligomeric amidine YB10-derived library with membrane targeting mechanism,and found that YB8 has good effects on inhibiting the formation of Staphylococcus aureus biofilm and destroying its mature biofilm.The minimum biofilm formation inhibitory concentration(MBIC)and the minimum mature biofilm destruction concentration(MBDC)were 16 μg/m L and 64 μg/m L,respectively.Secondly,this project uses gel retardation experiments,e DNA interference experiments,scanning electron microscope imaging and other methods to prove that the molecule can bind to e DNA in extracellular polymeric substances(EPS),thereby destroying the matrix structure and making the Biofilm dispersion.Subsequently,this project determined the bactericidal activity of YB8 against dormant and persistent bacteria in biofilms,and verified its multiple mechanisms of cell membrane targeting,genomic DNA binding,stimulating bacteria to produce reactive oxygen species,and the advantages of low drug resistance.Finally,this project verifies that YB8 also has excellent anti-biofilm effect in complex in vitro models and mouse models,and its antibacterial and anti-biological properties of surface modification of polycaprolactone materials,combined with nitric oxide donors Membrane application.(2)In the treatment of bacterial infections in an acidic microenvironment: First,this project tested 174 FDA-approved antibiotics for minimum inhibitory concentrations under acidic conditions(pH4.8)and neutral conditions(pH7.8),and obtained a single drug in Difference in antibacterial capacity at different pH(pH effect).Second,the project measured the pH effect of each drug after adding the membrane-targeting molecule polymyxin as a sensitizer.Comprehensive analysis proved that the addition of sensitizers significantly enhanced the pH-effect antibacterial ability of antibiotics,and gradually increased with the increase of sensitizer concentrations.Finally,this project uses the checkboard experiment to verify the dose relationship of the pH effect of the combined drug,the broad spectrum of the pH-effect antibacterial strain and the strain selectivity of the same concentration combination in the pH4.8 environment,and the drug is incorporated into the polyacrylonitrile material,verified its antibacterial properties under acidic conditions.