title: Intracellular uptake: a possible mechanism for silver engineered nanoparticle toxicity to a freshwater alga Ochromonas danica.
abstract: The behavior and toxicity of silver engineered nanoparticles (Ag-ENs) to the mixotrophic freshwater alga Ochromonas danica were examined in the present study to determine whether any other mechanisms are involved in their algal toxicity besides Ag(+) liberation outside the cells. Despite their good dispersability, the Ag-ENs were found to continuously aggregate and dissolve rapidly. When the initial nanoparticle concentration was lower than 10 µM, the total dissolved Ag(+) concentration ([Ag(+)](T)) in the suspending media reached its maximum after 1 d and then decreased suggesting that Ag(+) release might be limited by the nanoparticle surface area under these conditions. Furthermore, Ag-EN dissolution extent remarkably increased in the presence of glutathione. In the Ag-EN toxicity experiment, glutathione was also used to eliminate the indirect effects of Ag(+) that was released. However, remarkable toxicity was still observed although the free Ag(+) concentration in the media was orders of magnitude lower than the non-observed effect concentration of Ag(+) itself. Such inhibitive effects were mitigated when more glutathione was added, but could never be completely eliminated. Most importantly, we demonstrate, for the first time, that Ag-ENs can be taken in and accumulated inside the algal cells, where they exerted their toxic effects. Therefore, nanoparticle internalization may be an alternative pathway through which algal growth can be influenced.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing, Jiangsu Province, People's Republic of China. miaoaj@nju.edu.cn
authors.forename: Ai-Jun
authors.initials: AJ
authors.lastname: Miao
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Luo
authors.forename: Chi-Shuo
authors.initials: CS
authors.lastname: Chen
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Chin
authors.forename: Peter H
authors.initials: PH
authors.lastname: Santschi
authors.forename: Antonietta
authors.initials: A
authors.lastname: Quigg
mesh_terms: D044523:Chrysophyta / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000235:genetics / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission / Q000379:methods; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D010839:Phytoplankton / Q000378:metabolism; D012834:Silver / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D012834:Silver; D005978:Glutathione