Mechanism Of Selective Antibacterial Action And Antibacterial Activity Of Cysteine Functionalized Nanomaterials

Gold nanoparticles had low toxicity and broad spectrum antibacterial properties,,but the application of pure gold nanoparticles in antibacterial applications was greatly limited because their low antibacterial effect.In order to improve its antibacterial effect and utilize low toxicity and wide spectrum properties,the chiral cysteine functionalized gold nanoparticles(D/L-AuNPs)and chiral cysteine(D/L-Cys)were used as the model nanomaterials in this study.The chiral nanomaterials provided theoretical basis for the development and research of new antibacterial agents.1.The antibacterial properties of chiral Cys studyThe different concentration of D/L-Cys against E.coli,S.aureus,L.monocytogenes,S.enteritidis antibacterial performance and growth curve results showed that:D-Cys exhibited broad-spectrum and strong antimicrobial activity against E.coli,L.monocytogenes,S.aureus and S.enteritis,while L-Cys exhibited preferred antimicrobial activity against S.aureus.The percentage of dead bacteria treated with D-Cys and L-Cys were 92%and 60%,respectively.The inhibition rate of D/L-Cys against S.aureus was 90%and 92%,respectively.Potassium ion leakage test,PI staining and TEM images results showed that D-Cys damages E.coli cell membrane more seriously.2.Study on the antibacterial performance and mechanism of chiral cysteine functionalized gold nanoparticles against E.coliThe antibacterial rate of 3 mg/mL D-Cys functionalized gold nanoparticles against E.coli can up to 96.6%and 65.4%respectively;indicating that D-Cys functionalized AuNPs can significantly improve the antibacterial performance of D-Cys.The effects of D/L-Cys functionalized AuNPs on the cell membrane structure;microstructure and content leakage of E.coli were studied.The results showed that the damage of D-Cys to the cell membrane was greater than that of L-Cys,resulting in severe intracellular material leakage.The results of scanning electron microscope showed that the D-Cys functionalized gold nanoparticles treatment group had a large number of nanoparticles adsorbed on the cell membrane and holes appeared on the bacteria,resulting leading to bacteria died seriously.The results of projection electron microscopy showed that a large amount of the D-Cys functionalized gold nanoparticle absorbed into cell,resulting that most of the cell membrane was broken,except the contour of cell wall remained,the organelles in the cytoplasm were scattered and broken,the cell contents disappeared and exhausted,and the bacteria died seriously.3.Antimicrobial properties of chiral cysteine in vivo and its effect on intestinal microorganismsD-Cys functionalized AuNPs can reduce 90%of E.coli in intestinal tissues of mice infected with intestinal tract infection by oral gavage,showing efficient in vivo antimicrobial activity and alleviating effectively in enteritis symptoms.At the same time,it can repair the damaged intestinal villi.D-Cys functionalized gold nanoparticles had little effect on the diversity,composition and species abundance of intestinal colony of mice compared with kanamycin.