Preparation,Characterization And Antibacterial Mechanism Of Ferrous-polysulfide Decoction

Microbial infection is one of the biggest threats to global public health today due to the rapid evolution of antibiotic resistant strains.Increasingly,multidrug resistant pathogenic strains of bacteria are now routinely isolated from all parts of the world.Pathogenic microorganisms,such as Enterococcus,Staphylococcus and Pseudomonas,are closely related species that are responsible for a wide variety of common bacterial infections.However,the widespread non-discretionary usage of antibiotics over the last 70 years has driven the emergence and prevalence of bacteria that exhibit drug resistant characteristics.This makes infectious diseases,which were once easily treatable,fatal again.In the United States alone,antibiotic resistance has led to more than two million infections and about 23 000 deaths each year.In fact,it was recently projected that antibiotic resistant pathogens would cause more than 10 million deaths worldwide per year by 2050.Eradication of certain bacterial infections is still a challenge which not only due to its complex pathogenic mechanism that subverts the host's immune system,but also to the formation of cell barriers and biofilms that prevent antibiotics from reaching the infection foci.Without doubt,addressing drug resistant and tolerant microbes is now a major global health challenge,and this calls for an urgent need to revisit approaches that can effectively control bacterial infections,either through novel formulations,delivery systems or through the discovery of more effective next generation antibiotics.Nanomaterials can overcome the antibiotic-resistance mechanisms owing to their unique physio-chemical properties,enabling nanomaterials to execute multiple novel bactericidal pathways to achieve antimicrobial activity.Nanomaterials can bind and disrupt bacterial membranes,causing leakage of cytoplasmic components.Upon membrane permeation,nanomaterials can also bind to intracellular components such as DNA,ribosomes and enzymes to disrupt the normal cellular machinery.Disruption in the cellular machinery can lead to oxidative stress,electrolyte imbalance and enzyme inhibition,resulting in cell death.The bactericidal pathways followed by nanomaterials are inherently dependent upon their core material,shape,size and surface functionalization.In this paper,nFeS NPs are synthesized by hydrothermal synthesis,and we decocted an aqueous solution containing nanoscale iron sulfide(nFeS)to obtain ferrous-polysulfide decoction(FerropSD).We analyzed the ingredients of the decoction,the bacteriostatic effect,and the existing bacteriostatic mechanism.Finally,a mouse in vivo infection model was constructed to evaluate the efficacy of the decoction.The research content is mainly divided into the following three parts:1.Preparation and analysis of ferrous-polysulfide decoctionIn this experiment,nFeS NPs were synthesized by hydrothermal synthesis,and FerropSD was prepared by high pressure.It was found that the FerropSD contained a large amount of iron and sulfur after testing.The contents of iron and sulfur in the FerropSD were detected using different detection methods.The existence forms of iron and sulfur in the FerropSD were detected by the kit.The sulfur in the decoction mostly exists in the form of polysulfur,while the iron element exists in the form of more divalent iron.2.Antibacterial effect and mechanism analysis of ferrous-polysulfide decoction(FerropSD)In this experiment,FerropSD prepared with different concentrations of nFeS NPs were used to treat S.aureus and E.coli.It was found that FerropSD had a good inhibitory effect on S.aureus and E.coli.However,it has no inhibitory effect on the fungus Candida albicans.In addition,the antibacterial effect of the decoction was simulated by arranging different components in FerropSD.By this method,it was successfully found that the activity of the main antibacterial ingredient in the decoction was divalent iron ion.The changes of ROS,MDA,GSH/GSSG in bacteria treated with FerropSD were detected in the study of antibacterial mechanism.After treatment,the internal ROS and MDA levels of the bacteria were significantly increased which indicating that FerropSD caused lipid peroxidation by increasing the internal ROS level of the bacteria,and the dynamic balance of GSH/GSSG inside the bacteria was broke,causing bacteria death3.Curative effect of ferrous-polysulfide decoction(FerropSD)in vivo infectionIn this experiment,a mouse bacterial infection model was constructed,which further confirmed that FerropSD has good curative effect on in vivo infection and good biological safety.It may be an alternative therapeutic strategy for the treatment of infectious disease.