title: Size-dependent ROS production by palladium and nickel nanoparticles in cellular and acellular environments - An indication for the catalytic nature of their interactions.
abstract: Palladium and nickel nanoparticles with variable but narrowly defined primary particle sizes in the range of 4-27 nm were investigated toward their catalytic activity and their ability to produce reactive oxygen species (ROS). The agglomerate size in the gas phase was between 50 and 150 nm, after transfer into solution probably larger. The catalytic activity was measured on the basis of CO oxidation to CO2. The formation of ROS was determined after transferring the particles into phosphate buffered saline (PBS), via the 2',7'-dichlorofluorescein method in a cell-free environment and with THP-1 cells. Activities were normalized with regard to catalyst surface area to enable a meaningful comparison of size effects. The solubility was measured for both materials and found to be 2 µg/ml for Ni and below the detection limit of 0.8 µg/ml for Pd. In the concentration range of about 4-250 µg/ml both materials induced a significant production of ROS in both acellular and cellular environments, with palladium being more active than nickel by several orders of magnitude. On an equal surface area concentration basis, both acellular and cellular ROS production showed a pronounced dependence on the primary particle size, with a maximum in the vicinity of 12 nm. The surface-specific catalytic activity also had a maximum at that size range. The correlation of these size effects is both surprising and - in combination with the poor solubility of palladium and nickel in PBS solution - a strong argument in favor of a particulate, catalytic mechanism for ROS production.
authors: a Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT) , Karlsruhe , Germany and.
authors: Nicole
authors: N
authors: Neubauer
authors: b Unit of Systems Toxicology , Finnish Institute of Occupational Health (FIOH) , Helsinki , Finland.
authors: Jaana
authors: J
authors: Palomaeki
authors: b Unit of Systems Toxicology , Finnish Institute of Occupational Health (FIOH) , Helsinki , Finland.
authors: Piia
authors: P
authors: Karisola
authors: b Unit of Systems Toxicology , Finnish Institute of Occupational Health (FIOH) , Helsinki , Finland.
authors: Harri
authors: H
authors: Alenius
authors: a Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT) , Karlsruhe , Germany and.
authors: Gerhard
authors: G
authors: Kasper
mesh_terms: D002384:Catalysis / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity*; D009532:Nickel / Q000737:chemistry / Q000633:toxicity*; D010084:Oxidation-Reduction / Q000187:drug effects; D010165:Palladium / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012995:Solubility
chemical_list: D017382:Reactive Oxygen Species; D010165:Palladium; D009532:Nickel
keywords: Aerosol; biological activity; catalytic activity; reactive oxygen species