title: pH-Dependent Antimicrobial Properties of Copper Oxide Nanoparticles in Staphylococcus aureus.
abstract: The antimicrobial properties of CuO nanoparticles have been investigated, but the underlying mechanisms of toxicity remain the subject of debate. Here, we show that CuO nanoparticles exhibit significant toxicity at pH 5 against four differentStaphylococcus aureus (S. aureus)strains, including Newman, SA113, USA300, and ATCC6538. At this pH, but not at pH 6 and 7, 5 mM CuO nanoparticles effectively caused reduction of SA113 and Newman cells and caused at least 2 log reduction, whereas 20 mM killed most strains but not USA300. At 5 mM, the nanoparticles were also found to dramatically decrease reductase activity in SA113, Newman, and ATCC6538 cells, but not USA300 cells. In addition, analysis of X-ray absorption near-edge structure and extended X-ray absorption fine structure confirmed thatS. aureuscells exposed to CuO nanoparticles contain CuO, indicating that Cu2+ions released from nanoparticles penetrate bacterial cells and are subsequently oxidized intracellularly to CuO at mildly acidic pH. The CuO nanoparticles were more soluble at pH 5 than at pH 6 and 7. Taken together, the data conclusively show that the toxicity of CuO nanoparticles in mildly acidic pH is caused by Cu2+release, and that USA300 is more resistant to CuO nanoparticles (NPs) than the other three strains.
authors.affiliation: Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan 320, Taiwan. yihhsueh@saturn.yzu.edu.tw.
authors.forename: Yi-Huang
authors.initials: YH
authors.lastname: Hsueh
authors.affiliation: Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Taoyuan 320, Taiwan. n8808701@gmail.com.
authors.forename: Ping-Han
authors.initials: PH
authors.lastname: Tsai
authors.affiliation: Department of Chemical Engineering and Materials Science, Yuan Ze University, Taoyuan 320, Taiwan. kslin@saturn.yzu.edu.tw.
authors.forename: Kuen-Song
authors.initials: KS
authors.lastname: Lin
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000633:toxicity*; D003300:Copper / Q000737:chemistry / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D013045:Species Specificity; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000254:growth & development; D014961:X-Ray Diffraction
chemical_list: D000890:Anti-Infective Agents; D003300:Copper; C000520:cuprous oxide
keywords: EXAFS; Staphylococcus aureus; XANES; copper oxide nanoparticles