title: Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.
abstract: Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results.
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China. Electronic address: ianleung@hku.hk.
authors.forename: Yu Hang
authors.initials: YH
authors.lastname: Leung
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Mana M N
authors.initials: MM
authors.lastname: Yung
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China; Department of Physics, South University of Science and Technology of China, 1088 Xueyuan Ave, Nanshan, Shenzhen, China.
authors.forename: Alan M C
authors.initials: AM
authors.lastname: Ng
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Angel P Y
authors.initials: AP
authors.lastname: Ma
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Stella W Y
authors.initials: SW
authors.lastname: Wong
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Charis M N
authors.initials: CM
authors.lastname: Chan
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Yip Hang
authors.initials: YH
authors.lastname: Ng
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Aleksandra B
authors.initials: AB
authors.lastname: Djurišić
authors.affiliation: Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China; Department of Physics, South University of Science and Technology of China, 1088 Xueyuan Ave, Nanshan, Shenzhen, China.
authors.forename: Muyao
authors.initials: M
authors.lastname: Guo
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Mabel Ting
authors.initials: MT
authors.lastname: Wong
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Frederick C C
authors.initials: FC
authors.lastname: Leung
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Wai Kin
authors.initials: WK
authors.lastname: Chan
authors.affiliation: School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Kenneth M Y
authors.initials: KM
authors.lastname: Leung
authors.affiliation: Department of Chemistry, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Hung Kay
authors.initials: HK
authors.lastname: Lee
mesh_terms: D002563:Cerium / Q000737:chemistry*; D017377:Diatoms / Q000187:drug effects / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000187:drug effects / Q000528:radiation effects; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D014466:Ultraviolet Rays
chemical_list: D002563:Cerium; C030583:ceric oxide