摘要
Silver-loaded MnO_2 nanomaterials（Ag/MnO_2）,including Ag/α-MnO_2,Ag/β-MnO_2,Ag/γ-MnO_2and Ag/δ-MnO_2 nanorods,were prepared with hydrothermal and impregnation methods.The bactericidal activities of four types of Ag/MnO_2 nanomaterials against Escherichia coli were investigated and an inactivation mechanism involving Ag~＋ and reactive oxygen species（ROS）was also proposed.The bactericidal activities of Ag/MnO_2 depended on the MnO_2 crystal phase.Among these nanomaterials,Ag/β^-MnO_2 showed the highest bactericidal activity.There was a 6-log decrease in E.coli survival number after treatment with Ag/β^-MnO_2 for120 min.The results of 5,5-dimethyl-l-pyrroline-N-oxide spin-trapping measurements by electron spin resonance indicate OH and O_2^- formation with addition of Ag/β-MnO_2,Ag/γ-MnO_2 or Ag/δ-MnO_2.The strongest peak of OH appeared for Ag/β-MnO_2,while no OH or ·O_2^-signal was found over Ag/α-MnO_2.Through analysis of electron spin resonance（ESR） and Ag＋elution results,it could be deduced that the toxicity of Ag~＋ eluted from Ag/MnO_2 nanomaterials and ROS played the main roles during the bactericidal process.Silver showed the highest dispersion on the surface of β-MnO_2,which promoted ROS formation and the increase of bactericidal activity.Experimental results also indicated that Ag/MnO_2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane.
Silver-loaded MnO_2 nanomaterials（Ag/MnO_2）,including Ag/α-MnO_2,Ag/β-MnO_2,Ag/γ-MnO_2and Ag/δ-MnO_2 nanorods,were prepared with hydrothermal and impregnation methods.The bactericidal activities of four types of Ag/MnO_2 nanomaterials against Escherichia coli were investigated and an inactivation mechanism involving Ag~＋ and reactive oxygen species（ROS）was also proposed.The bactericidal activities of Ag/MnO_2 depended on the MnO_2 crystal phase.Among these nanomaterials,Ag/β^-MnO_2 showed the highest bactericidal activity.There was a 6-log decrease in E.coli survival number after treatment with Ag/β^-MnO_2 for120 min.The results of 5,5-dimethyl-l-pyrroline-N-oxide spin-trapping measurements by electron spin resonance indicate OH and O_2^- formation with addition of Ag/β-MnO_2,Ag/γ-MnO_2 or Ag/δ-MnO_2.The strongest peak of OH appeared for Ag/β-MnO_2,while no OH or ·O_2^-signal was found over Ag/α-MnO_2.Through analysis of electron spin resonance（ESR） and Ag＋elution results,it could be deduced that the toxicity of Ag~＋ eluted from Ag/MnO_2 nanomaterials and ROS played the main roles during the bactericidal process.Silver showed the highest dispersion on the surface of β-MnO_2,which promoted ROS formation and the increase of bactericidal activity.Experimental results also indicated that Ag/MnO_2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane.
基金
financially supported by the National Natural Science Foundation of China(No.51208497)
the National High Technology Research and Development Program of China(No.2012AA062702)
International S&T Cooperation Program of China(2013DFM90110)
