title: Sulfidation of silver nanoparticles: natural antidote to their toxicity.
abstract: Nanomaterials are highly dynamic in biological and environmental media. A critical need for advancing environmental health and safety research for nanomaterials is to identify physical and chemical transformations that affect the nanomaterial properties and their toxicity. Silver nanoparticles, one of the most toxic and well-studied nanomaterials, readily react with sulfide to form Ag(0)/Ag2S core-shell particles. Here, we show that sulfidation decreased silver nanoparticle toxicity to four diverse types of aquatic and terrestrial eukaryotic organisms (Danio rerio (zebrafish), Fundulus heteroclitus (killifish), Caenorhabditis elegans (nematode worm), and the aquatic plant Lemna minuta (least duckweed)). Toxicity reduction, which was dramatic in killifish and duckweed even for low extents of sulfidation (about 2 mol % S), is primarily associated with a decrease in Ag(+) concentration after sulfidation due to the lower solubility of Ag2S relative to elemental Ag (Ag(0)). These results suggest that even partial sulfidation of AgNP will decrease the toxicity of AgNPs relative to their pristine counterparts. We also show that, for a given organism, the presence of chloride in the exposure media strongly affects the toxicity results by affecting Ag speciation. These results highlight the need to consider environmental transformations of NPs in assessing their toxicity to accurately portray their potential environmental risks.
authors.affiliation: Center for Environmental Implications of NanoTechnology (CEINT), Duke University , P.O. Box 90287, Durham, North Carolina 27708-0287, United States of America.
authors.forename: Clement
authors.initials: C
authors.lastname: Levard
authors.forename: Ernest M
authors.initials: EM
authors.lastname: Hotze
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Colman
authors.forename: Amy L
authors.initials: AL
authors.lastname: Dale
authors.forename: Lisa
authors.initials: L
authors.lastname: Truong
authors.forename: X Y
authors.initials: XY
authors.lastname: Yang
authors.forename: Audrey J
authors.initials: AJ
authors.lastname: Bone
authors.forename: Gordon E
authors.initials: GE
authors.lastname: Brown
authors.forename: Robert L
authors.initials: RL
authors.lastname: Tanguay
authors.forename: Richard T
authors.initials: RT
authors.lastname: Di Giulio
authors.forename: Emily S
authors.initials: ES
authors.lastname: Bernhardt
authors.forename: Joel N
authors.initials: JN
authors.lastname: Meyer
authors.forename: Mark R
authors.initials: MR
authors.lastname: Wiesner
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Lowry
mesh_terms: D000818:Animals; D000931:Antidotes / Q000737:chemistry*; D029064:Araceae / Q000187:drug effects; D017173:Caenorhabditis elegans / Q000187:drug effects; D002712:Chlorides / Q000737:chemistry; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D023781:Fundulidae / Q000378:metabolism; D007928:Lethal Dose 50; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D011205:Povidone; D012044:Regression Analysis; D012834:Silver / Q000737:chemistry*; D012995:Solubility; D013440:Sulfides / Q000737:chemistry*; D015027:Zebrafish / Q000378:metabolism
chemical_list: D000931:Antidotes; D002712:Chlorides; D013440:Sulfides; D012834:Silver; D011205:Povidone