Synthesis And Antibacterial Mechanism Of Novel Ruthenium（Ⅱ） Complexes Based On Triphenylphosphine（PPh₃） Groups

Staphylococcus aureus（S.aureus）is one of the most notorious pathogens,which can cause a series of infections ranging from moderately severe skin infections to fatal pneumonia and septicemia.More seriously,the abuse of antibiotics has led to the widespread existence of many multidrug-resistant bacteria（MDR）around the world.Among them,the infection of methicillin-resistant Staphylococcus aureus（MRSA）or vancomycin-resistant Staphylococcus aureus（VRSA）leads to a high global mortality rate.MDR has posed a huge threat to global public health,especially during COVID-19.Therefore,it is particularly important to develop new multi-target antibacterial agents for drug-resistant bacteria.In recent years,Antivirulence strategies with efforts targeting S.aureus virulence factors（VFs）have gained interest.Usually,VFs are essential for the bacterial ability to spread through tissues and survive under extreme conditions.Thus,antivirulence agents（Av As）can attenuates bacterial virulence,then promoting bacteria clearance in hosts.However,most VFs play unnecessary roles in the growth of bacteria in vitro,so inhibiting the secretion of toxins does not inhibit the growth of bacteria.In addition,antimicrobial peptides（AMPs）have been shown a strong efficacy in the fight against drug-resistant pathogens.AMPs achieve bactericidal effect by destroying bacterial membrane that is not prone to differential mutation.This mechanism of physical destruction of bacterial membrane can inhibit or reverse the drug resistance of bacteria.Therefore,antimicrobial peptides have more obvious advantages than traditional antibiotics in the fight against multidrug resistant bacteria.However,AMPs have inherent defects such as poor stability in vivo,which seriously limits its clinical application.Therefore,AMPs analog based on membrane active organic molecules is an alternative to overcome the defects.The ruthenium polypyridine complex has the characteristics of AMPs analog,can target bacterial cell membrane,and shows strong activity in vitro and in vivo.In order to further enter clinical trials,it is essential to optimize their selectivity and toxicity to mammalian cells.In this paper,a novel antibacterial ruthenium complex Ru（dtb）₂TITPP]（PF₆）₃（Ru1）with dual antibacterial mechanisms was obtained by integrating a ruthenium complex with membrane destroying properties with small molecules that inhibit bacterial toxin secretion.The minimal inhibit concentration（MIC）of Ru1 was as low as 460 n M.At the molecular,cellular,and animal levels,it was demonstrated that triphenylphosphonium（PPh₃）moiety is responsible for CcpA-targeting properties of Ru1,thereby Ru1 could inhibit bacterial toxin secretion and significantly reduce the pathogenicity of S.aureus.On the contrary,[Ru（dtb）₂BTPIP]（PF₆）₂（Ru2）without triphenylphosphine（PPh₃）failed to reduce the pathogenicity of S.aureus.By nucleic acid leakages assay,electron microscopy imaging and DAPI-PI staining assays,it was confirmed that the ruthenium polypyridine could effectively destroy the integrity of bacterial membrane.In addition,Ru1 can overcome bacterial resistance,enhance drug-resistant bacterial susceptibility to antibiotics,and avoid cross-resistance with antibiotics.Biological safety evaluation data displayed that Ru1 had low toxicity to the body and had good biocompatibility.At last,in mouse infection model,it was founded that Ru1 could efficiently remove S.aureus and Vancomycin-resistant strains in vivo and increase the survival rate of infected mice.