title: Fractionating nanosilver: importance for determining toxicity to aquatic test organisms.
abstract: This investigation applied novel techniques for characterizing and fractionating nanosilver particles and aggregates and relating these measurements to toxicological endpoints. The acute toxicity of eight nanosilver suspensions of varying primary particle sizes (10-80 nm) and coatings (citrate, polyvinylpyrrolidone, EDTA, proprietary) was assessed using three aquatic test organisms (Daphnia magna, Pimephales promelas, Pseudokirchneriella subcapitata). When 48-h lethal median concentrations (LC50) were expressed as total silver, both D. magna and P. promelas were significantly more sensitive to ionic silver (Ag(+)) as AgNO(3) (mean LC50 = 1.2 and 6.3 μg/L, respectively) relative to a wide range in LC50 values determined for the nanosilver suspensions (2 -126 μg/L). However, when LC50 values for nanosilver suspensions were expressed as fractionated nanosilver (Ag(+) and/or <4 nm particles), determined by ultracentrifugation of particles and confirmed field-flow-fractograms, the LC50 values (0.3-5.6 μg/L) were comparable to the values obtained for ionic Ag(+) as AgNO(3). These results suggest that dissolved Ag(+) plays a critical role in acute toxicity and underscores the importance of characterizing dissolved fractions in nanometal suspensions.
authors.affiliation: US Army Engineer Research and Development Center, Vicksburg, Mississippi 39180, United States. Alan.J.Kennedy@usace.army.mil
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Kennedy
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Hull
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Bednar
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Goss
authors.forename: Jonas C
authors.initials: JC
authors.lastname: Gunter
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Bouldin
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Vikesland
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Steevens
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000187:drug effects*; D005591:Chemical Fractionation / Q000379:methods*; D000460:Chlorophyta / Q000187:drug effects; D003530:Cyprinidae; D003621:Daphnia / Q000187:drug effects; D053768:Metal Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D010316:Particle Size; D012834:Silver / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver