Research On The Effect And Mechanism Of Nano-iron Sulfide Antibacterial And Biofilm Removal

A large quantity of bacteria accumulates on the surface or in various channels of human body,and a considerable part of them do no harm to health,on the contrary,even perform a positive effect on normal physiological activities of human organism.However,when facing with the stimulation such as reduced immunity,damages occurred on defense barriers like skin and mucosa.or intensified antibiotics abuse in recent years,things would easily evolve to infections and diseases.It will cause quite serious symptoms and complications with delayed or inappropriate treatment,or restricted therapy.In particular,the antibiotics abuse has led to the emergence of a plenty of drug-resistant bacteria,making bacterial infectious diseases,especially in-hospital acquired infections,increasingly troublesome.The speed at which humans develop and improve new drugs is far less than which drug-resistant strains are produced.Recent reports on "superbugs"have emerged in an endless stream,and the action ot strong and effective fungicides exploitation is urgently needed.As early as 2600-2100 BC.there had been earliest documentary records on the use ot garlic as a condiment and medicin by Sumerians.As the old saying goes,garlic is considered as a homologous plant of medicine and food.It is not only an essential seasoning in people's daily diet.but also a health care product that is passed down by the people,with its superior sterilization,blood fat reduction,anti-oxidation and immunity properties.A series of effects such as the irritating odor,instability of the active ingredients,as well as its insufficiency and easy degradation effects,have lonu been one of the obstacles to convert into a potent drug.It is always the subject for some researchers on how to amplify its excellent bactericidal effect with the prolonged period without causing discomfort.Fe3O4 nanozymes(IONzyme)are known as one kind of representative nanozymes.Researchers highly affirmed its promising application prospects ini mtunologic diagnosis.bacterial infection,industrial catalysis and other aspects with high stability,excellent biocompatibility,and simple and inexpensive synthesis.This study aimed to convert several organic-derived sulphides into inorganic nano-iron sultides(nFeS)in order to evaluate the therapeutic potential of bacterial infection-related diseases based on the previous research on iron-based nanozmes.Firstly,we compared the morphology,particle size,element ratio,and peroxidase-like activity of several kinds of nFeS whose sulfur came from vary allicin derivatives through the synthesis.Secondly,we explored the potential of nFeS to inhibit microorganism growth containing Gram-negative and Gram-positive bacteria(including resistant strains)and fungi,tentatively speculated its antibacterial mechanism.Finally,the biocompatibility of nFeS were evaluated and applied in oral biotilms and the treatment of infectious wounds according to its strengths.The research content is mainly divided into the following three parts:1.Preparation and characterization of nFeSIn this portion,nFeS was synthesisd from different sulfur sources was prepared by solvothermal method.The structure and particle size of nFeS were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).It was found that nFeS,whose sulfur came from organic sulfur source,presented a mixture structure of hexagonal sheet-like nano-iron sulfides and spherical ferroferric oxide nanoparticles while IONzymes were just spherical uniform particles.The proportion of the flakes and particles would change correspondingly with the input of sulfur-containing organic matter.In the case of controlling the sulfur input,diallyl disulfide(DADS),produced as one of the sulfur source,presented the most hexagonal nanosheets of all.while other organic sulfide sources such as allyl sulfide(DAS)and diallyl sulfide(Allyl methyl sulfide,AMS),diallyl trisulfide(DATS)the product showed more IONzymes in the products.According to the elemental analysis results obtained by the Energy Dispersive Spectrometer.DADS-nFeS showed the highest sulfur content among these compositions and was further confirmed to be polysulfide by X-ray diffraction pattern.2.Evaluation of the killing effect of DADS-nFeS on Gram-negative bacteria,Gram-positive bacteria(including resistant strains)and fungiIn this portion,it was found that the peroxidase activity of DADS-nFeS was much better than that of IONzymes as well as the activity of nFeS synthesized by AMS,DAS.DATS.It was observed that the peroxidase activity of nFeS was positively correlated with the input of DADS.Next,Gram-positive bacteria including Staphylococcus aureus(S,aureus)and Gram-negative bacteria represented by Escherichia coli(E.coli)were tested,which proved the superior antibacterial effects of DADS-nFeS over nFeS synthesized by other sulfur sources.When it moved to Streptococcus mutans(S.mitans).Sulmonela enteritidis(S.enteritidis).Pseudomonas aeruginosa(P.aeruginosa),Acinetobacter baumannii(A.baumannii).DADS-nFeS performed a significant and highly effective antibacterial effects compared to pure DADS with the same sulfur content.and more prominently,it has killing effect of up to 3 logs for the methicillin-resistant Staphylococcus aureus strain(MRSA).For fungi,however,Candida albicans(C.albicans),chosen for this study,were insensitive to the nFeS treatment.3.The biological application of DADS-nFeS in the prevention of oral biofilm and the treatment of infectious woundsIn view of its good dispersibility and inhibition of S.mutans.this study established an oral S.mutans biofilm model to assess the potential of DADS-nFeS in the prevention and treatment of dental caries.The excellent therapeutic results like dry weight.bacterial survival rate,SEM images and confocal fluorescence microscopy images all showed the effect of nFeS.Secondly,based on its inhibitory effect on Acinetobacter baumannii(A.baumannii),a biofilm model was established to simulate the adhesion of A.baumannii to medical implants,and its ability to inhibit biofilm formation was detected by crystal violet staining.According to the inhibition of P.aeruginosa,a wound model with P.aeruginosa infection was established.According to the recovery of wounds.DADS-nFeS showed the ability to promote the healing of infectious wounds.According to the MTT evaluation results.DADS-nFeS showed good biocompatibility for fibroblasts cells.