title: Comparative toxicity study of Ag, Au, and Ag-Au bimetallic nanoparticles on Daphnia magna.
abstract: A comparative assessment of the 48-h acute toxicity of aqueous nanoparticles synthesized using the same methodology, including Au, Ag, and Ag-Au bimetallic nanoparticles, was conducted to determine their ecological effect in freshwater environments through the use of Daphnia magna, using their mortality as a toxicological endpoint. D. magna are one of the standard organisms used for ecotoxicity studies due to their sensitivity to chemical toxicants. Particle suspensions used in toxicity testing were well-characterized through a combination of absorbance measurements, atomic force or electron microscopy, flame atomic absorption spectrometry, and dynamic light scattering to determine composition, aggregation state, and particle size. The toxicity of all nanoparticles tested was found to be dose and composition dependent. The concentration of Au nanoparticles that killed 50% of the test organisms (LC(50)) ranged from 65-75 mg/L. In addition, three different sized Ag nanoparticles (diameters = 36, 52, and 66 nm) were studied to analyze the toxicological effects of particle size on D. magna; however, it was found that toxicity was not a function of size and ranged from 3-4 μg/L for all three sets of Ag nanoparticles tested. This was possibly due to the large degree of aggregation when these nanoparticles were suspended in standard synthetic freshwater. Moreover, the LC(50) values for Ag-Au bimetallic nanoparticles were found to be between that of Ag and Au but much closer to that of Ag. The bimetallic particles containing 80% Ag and 20% Au were found to have a significantly lower toxicity to Daphnia (LC(50) of 15 μg/L) compared to Ag nanoparticles, while the toxicity of the nanoparticles containing 20% Ag and 80% Au was greater than expected at 12 μg/L. The comparison results confirm that Ag nanoparticles were much more toxic than Au nanoparticles, and that the introduction of gold into silver nanoparticles may lower their environmental impact by lowering the amount of Ag which is bioavailable.
authors.affiliation: BCPS Department, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616, USA.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.forename: Brian
authors.initials: B
authors.lastname: Albee
authors.forename: Matti
authors.initials: M
authors.lastname: Alemayehu
authors.forename: Rocio
authors.initials: R
authors.lastname: Diaz
authors.forename: Leigha
authors.initials: L
authors.lastname: Ingham
authors.forename: Shawn
authors.initials: S
authors.lastname: Kamal
authors.forename: Maritza
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Sandra Whaley
authors.initials: SW
authors.lastname: Bishnoi
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects*; D006046:Gold / Q000737:chemistry / Q000633:toxicity*; D007928:Lethal Dose 50; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D012834:Silver / Q000737:chemistry / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver; D006046:Gold