In Situ Synthesis And Antibacterial Activity Of Ag Nanoparticles On The Surface Of Silica Dioxide Microspheres

At present,the research of alternative antibacterial agents is in full swing with the abuse of antibiotics.Non-traditional antibacterial agents are thus of great interest to overcome resistance resulting from the use of antibiotics.Ag nanoparticles（AgNPs）is becoming excellent antibacterial material due to their broad-spectrum antibacterial effects,highly efficient and long-lasting effects.However,the reducing/capping agents used in the traditional chemical synthesis process of AgNPs are not environmentally friendly,and cytotoxic uauslly.Seeking for a green and efficient method to synthesize AgNPs material which is antibacterial and safe is the focus in its fields.In this paper,AgNPs were synthesized in situ on the surface of thiol-group-functionalized silica dioxide microspheres,the process was in the aqueous solution without other reducing agents or capping agents.The antibacterial activity and cytotoxicities of them were explored,followed by investigating the potenial impact of organic ligands on the antibacterial activity of AgNPs.（1）sol-gel process was used to synthesize two silica dioxide microspheres which had different size,TSMs（1μm）and TSSMs（130nm）,and the microspheres which has the best dispersity was obtained by adjusting the reaction time,then AgNPs@TSMs and AgNPs@TSSMs were obtained by AgNPs in situ on its surface.The antibacterial activity and cytotoxicities of two particles were explored.The results show that the minimal inhibitory concentration(16-32μg mL^-11 and 4-8μg mL^-1)of AgNPs@TSSMs against Gram-positive and Gram-negative bacteria were higher than AgNPs@TSMs”,and the two particles have better antibacterial activity and efficiency to Gram-positive bacteria.The results of cytotoxicities show that the use of AgNPs@TSMs has some potential safety problem against Gram-negative bacteria,meanwhile the other group showed good safety in the respective minimal inhibitory concentration,which means the further exploration as antibacterial materials.（2）The AgNPs@TSSMs which has better antibacterial activity was chosen to connect ligands,and four AgNPs@TSSMs with different organic functional groups were synthesized.The SEM graphs show the morphology of particles were not changed and the particles have good dispersity.The antibacterial activity and cytotoxicities of particles were explored.The results show that the connection of-COOH ligands enhance the antibacterial activity of AgNPs particles(MIC:8-16μg mL^-1),while-OH and-Ph ligands reduce it(MIC:32-64μg mL^-1).The results of cytotoxicities show the particles with-COOH ligand did not make damage to cells in the range of MIC,while the particles with-OH and-Ph have a closely range between MIC and cytotoxicities,so a further research and consideration to the application of this particle should be performed.All results confirm that-COOH ligands should be used in the process of synthesis of AgNPs,which is helpful to the antibacterial property of AgNPs.