Study On The Activity Of Three Functional Groups Modified Polypyridine Ruthenium Complexes Against S.aureus Biofilm

S.aureus is a Gram-positive pathogenic bacteria that can cause various inflammation and infection.Antibiotic treatment is the first choice for S.aureus infection.However,the abuse of antibiotics and the evolution of S.aureus have led to the rapid development of resistance to multiple antibiotics,which poses a serious threat to public health.Biofilm is one of the mechanisms of resistance of S.aureus.The bacterial cells in the biofilm can tolerate more than the floating cells.The normal dose of antibiotics is not enough to eradicate the biofilm.Due to the increasingly serious crisis of antibiotic resistance,the use of metals as potential antibiotics has been given renewed attention,especially ruthenium complexes.Because the rigid octahedral geometry of ruthenium complex is easy to be modified and has rich photophysical and electrochemical properties,it may be easier to optimize the binding affinity of cell targets than organic drugs.In addition,compared with organic molecules,ruthenium complexes are more likely to obtain new antibacterial activity mechanisms.Polypyridine structure is a typical nitrogen-containing heterocyclic compound.Its advantage lies in the electron transfer,which makes it possible to have more targets.Different functional groups have different modification effects,which may produce different targets.For example,anthraquinone functional group is a functional small molecule with multiple physiological functions,which has the effects of anti-biofilm,anti-oxidation and anti-mutation.In this paper,a variety of ruthenium complex antifungal agents against S.aureus were designed and synthesized by introducing different functional groups with ruthenium as auxiliary ligand.1.After the ligand L1 of Triphenylamine derivative functional group was synthesized.Three kinds of ruthenium complexes[Ru（dmob）₂L1]（PF₆）₂（Ru-1）,[Ru（bpy）₂L1]（PF₆）₂（Ru-2）,[Ru（dmb）₂L1]（PF₆）₂（Ru-3）,were synthesized with Ru（dtb）₂Cl₂,Ru（dmob）₂Cl₂,Ru（bpy）₂Cl₂ as auxiliary ligands.（dmob=4,4’dimethoxy-2,2’-bipyridine,bpy=2,2’-bipyridine,dmb=4,4’-dimethyl-2,2’-bipyridine）,The structure of Ru-1-Ru-3 was characterized by hydrogen spectrum,carbon spectrum and high resolution mass spectrometry.The detailed molecular structure of compound Ru-3 was determined by single crystal X-ray diffraction.They have obvious antibacterial activity against S.aureus complex Ru-3 shows the best antibacterial effect,and the MIC is 4μg/m L.Therefore,further study on its biological activity showed that complex Ru-3 could effectively inhibit the formation of biofilm and destroy the cell membrane.In addition,in vitro hemolysis experiments have shown that the cell hemolysis rate of the complex Ru-3 on mammalian red blood cells is negligible.In the toxicity experiment of the wax borer model,the complex Ru-3 showed low toxicity in vivo.Combined with histopathology studies,it further showed that the complex Ru-3had good biocompatibility.In addition,the synergistic effect of compound Ru-3with ampicillin,chloramphenicol,tetracycline,kanamycin and gentamicin on S.aureus was detected by chessboard method.Finally,in vivo results showed that compound Ru-3 could significantly promote the wound healing of mice infected with S.aureus.2.After the ligand L2 of anthraquinone functional group was synthesized.Three ruthenium complexes[Ru（dtb）₂L2]（PF₆）₂（Ru-4）,[Ru（dmob）₂L2]（PF₆）₂（Ru-5）,[Ru（bpy）₂L2]（PF₆）₂（Ru-6）were synthesized with Ru（dtb）₂Cl₂,Ru（dmob）₂Cl₂,Ru（bpy）₂Cl₂ as auxiliary ligands,（dtb=4,4’-di-tert-butyl-2,2’-bipyridine,dmob=4,4’-dimethyl-2,2’-bipyridine,bpy=2,2’-bipyridine）,and its structure was characterized.Among them,complex Ru-4 showed excellent antibacterial activity against gram-positive bacteria S.aureus MIC=1μg/m L,at sub inhibitory concentrations,it can inhibit the activity of bacterial biofilms and kill bacteria in bacterial biofilms,with low hemolytic and cytotoxic activity.In addition,complex Ru-4 showed obvious rapid bactericidal activity,low drug resistance,destruction of bacterial biofilm activity and high biological safety in vivo.In addition,the skin infection model and sepsis mouse model showed that the anti-infection effect of the compound was equivalent to that of vancomycin.3.After the ligand L3 of 1,8-naphthylpyridine nuclear functional group was synthesized.Three ruthenium complexes[Ru（dtb）₂L3]（PF₆）₂（Ru-7）,[Ru（dmob）₂L3]（PF₆）₂（Ru-8）,[Ru（bpy）₂L3]（PF₆）₂（Ru-9）were synthesized with Ru（dtb）₂Cl₂,Ru（dmob）₂Cl₂,Ru（bpy）₂Cl₂,（bpy=2,2’-bipyridine,dmob=4,4’-dimethyl-2,2’-Bipyridine,dtb=4,4’-di-tert-butyl-2,2’-bipyridine）,and its structure was characterized.The three complexes have different antibacterial activities against S.aureus,and the antibacterial activity of Ru-9 is the best MIC=1μg/m L),with low drug resistance and low cytotoxicity,can destroy the bacterial cell membrane and act on DNA.In addition,in the mouse skin infection model and the wax worm infection model,Ru-9 shows antibacterial activity.