title: Antimicrobial activity of silver loaded MnO2 nanomaterials with different crystal phases against Escherichia coli.
abstract: Silver-loaded MnO2 nanomaterials (Ag/MnO2), including Ag/α-MnO2, Ag/β-MnO2, Ag/γ-MnO2 and Ag/δ-MnO2 nanorods, were prepared with hydrothermal and impregnation methods. The bactericidal activities of four types of Ag/MnO2 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/MnO2 depended on the MnO2 crystal phase. Among these nanomaterials, Ag/β-MnO2 showed the highest bactericidal activity. There was a 6-log decrease in E. coli survival number after treatment with Ag/β-MnO2 for 120min. The results of 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping measurements by electron spin resonance indicate OH and O2‾ formation with addition of Ag/β-MnO2, Ag/γ-MnO2 or Ag/δ-MnO2. The strongest peak of OH appeared for Ag/β-MnO2, while no OH or O2‾ signal was found over Ag/α-MnO2. Through analysis of electron spin resonance (ESR) and Ag(+) elution results, it could be deduced that the toxicity of Ag(+) eluted from Ag/MnO2 nanomaterials and ROS played the main roles during the bactericidal process. Silver showed the highest dispersion on the surface of β-MnO2, which promoted ROS formation and the increase of bactericidal activity. Experimental results also indicated that Ag/MnO2 induced the production of intracellular ROS and disruption of the cell wall and cell membrane.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Lian
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: honghe@rcees.ac.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: He
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Changbin
authors.initials: C
authors.lastname: Zhang
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Sijin
authors.initials: S
authors.lastname: Liu
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Shaoxin
authors.initials: S
authors.lastname: Wang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects*; D017895:Manganese Compounds / Q000494:pharmacology*; D053768:Metal Nanoparticles / Q000032:analysis*; D010087:Oxides / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012834:Silver / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D017895:Manganese Compounds; D010087:Oxides; D017382:Reactive Oxygen Species; D012834:Silver; C016552:manganese dioxide
keywords: Bactericidal activity; Escherichia coli; MnO(2); ROS; Silver