The Disinfection Performance And Mechanisms Of Ag/Lysozyme Nanoparticles Supported With Montmorillonite Clay

The fabrication of montmorillonite?Mt?decorated with lysozyme-modified silver nanoparticles?Ag/lyz-Mt?was reported.The lysozyme?lyz?was served as both reducing and capping reagent.Lyz can deactivate a broad range of pathogens especially Gram positive bacteria without affecting the human and animal cells.Although AgNPs had been studied to be efficient in inactivating both Gram positive and Gram negative bacteria,there were more pronounced results showing that it tended to inhibit the growth of Gram negative bacteria.Coupling the bactericidal activity of the lyz with AgNPs,along with the high porous structure and large specific surface area of the Mt,prevented aggregation of AgNPs and promoted nanomaterial-bacteria interactions,resulting in a greatly enhanced bactericidal capability against both Gram positive and Gram negative bacteria.The synthesized Ag/lyz-Mt and silver/lysozyme?Ag/lyz?composites were characterized by TEM.The results demonstrated that Ag nanoparticles were uniformly dispersed on both montmorillonite surface and pores.By analyzing the transmission electron microscopy of Ag/lyz-Mt and Ag/lyz,we can see that the montmorillonite as a carrier does reduce the agglomeration of nanosilver.The infrared spectroscopy of Ag/lyz-Mt nanocomposites was analyzed by infrared spectroscopy.The results showed that the lysozyme in the composites still had certain biological activity.The silver and montmorillonite did not completely destroy the protein conformation of lysozyme.In this paper,Escherichia coli and Staphylococcus aureus were used as experimental strains,and the antimicrobial properties of Ag/lyz-Mt composite were studied by dilution plate counting method.Results showed that the prepared nanoparticles exhibited significant bactericidal ability for both Gram negative E.coli and Gram positive S.aureus,and the agent Ag/lyzl.6-Mt-1.0 exhibited maximum bactericidal activity.The bactericidal activity of Ag/lyzl.6-Mt-1.0 on E.coli and S.aureus was both time and concentration dependent.This paper systematically elucidated the bactericidal mechanisms of Ag/lyz-Mt.Direct contact between the Ag/lyz-Mt surface and the bacterial cell was essential to the disinfection.When the antibacterial material Ag/lyz-Mt and bacteria contact,due to the negative surface of the bacteria,the Coulomb force produced by silver ions and bacteria will make silver ions firmly adsorbed on the cells,so that silver ions can play a role in sterilization.Results also revealed that Ag⁺ was involved in the bactericidal activity of Ag/lyz-Mt via tests conducted using Ag⁺ scavengers.A positive ROS?reactive oxygen species?scavenging test indirectly confirmed the involvement of ROS(O₂^·-,H₂O₂,and ·OH)in the bactericidal mechanism.Furthermore,the concentrations of individual ROS were quantified.Through the continuous improvement of performance,it is believed that Ag/lyz-Mt nanocomposites can play an important role in water sterilization.