Effect of natural organic matter on dissolution and toxicity of sulfidized silver nanoparticles to Caenorhabditis elegans

Abstract

International audienceThe objectives of this study were to evaluate the effect of natural organic matter (NOM) on the dissolution and the toxicity of sulfidized AgNPs (sAgNPs) to a model soil organism, Caenorhabditis elegans in two distinct exposure media. This study demonstrated that the aggregation and dissolution of sAgNPs (75% Ag2S) was influenced by media composition, including inorganic composition and natural organic matter (NOM) concentration. Dissolution of sAgNPs was low (similar to 0.5%) but increased over time in all tested media (2 weeks). The presence of NOM either inhibited or enhanced Ag dissolution. Pony lake fulvic acid increased while Suwanee river and Pahokee peat fulvic acid (PLFA) decreased release of dissolved Ag from sAgNPs. Mortality of C. elegans exposed to sAgNPs was influenced by the inorganic composition of the media: with LC50 values of 8.15 mg Ag L-1 and > 15 mg Ag L-1 in moderately hard reconstituted water and soil solution pore water. Toxicity was totally rescued by the presence of all tested NOM types and concentrations, despite the increase of dissolved Ag in the media with PLFA. Overall, these results showed that the toxicity induced by a partly sulfidized AgNPs in C. elegans is low and negligible in the presence of NOM regardless of NOM influence on dissolution

Influence of soil porewater properties on the fate and toxicity of silver nanoparticles to Caenorhabditis elegans

“…However, in the present study the increased organic matter content in highOM porewaters did not have a protective effect on Ag 3–8Unf toxicity to C. elegans compared with lowOM porewaters, but rather promoted the inhibition of reproduction. This is consistent with findings that the type of organic matter and its elemental composition, rather than simply the total content, is a key factor in NP fate and dissolution . For example, the complexation of Ag with organic matter is linked to its sulfur content because Ag has a strong affinity to thiol ligands .…”

“…The mechanism of protection is largely attributed to the complexation of free metal with the dissolved organic matter, thereby reducing free ion concentrations able to interact with organism surfaces [33,34]. Conversely, dissolution of sulfidized Ag ENPs in C. elegans test media was found to be increased in the presence of Pony Lake fulvic acid, yet induced mortality of C. elegans was still entirely rescued [35]. This finding suggests additional protective mechanisms such as particle surface passivation or the reduction of oxidative stress by acting as a scavenger for free radicals [34].…”

Nanomaterial Transformations in the Environment: Effects of Changing Exposure Forms on Bioaccumulation and Toxicity

“…[ 67,68 ] For example, Pony Lake fulvic acid promoted dissolution of Ag 2 S NMs in C. elegans test media, however, toxicity was still entirely prevented by the presence of the organic ligands. [ 69 ] The impact of organic matter on NM toxicity may also be related to the scavenging of free radicals, as well as the passivation of charge at the surface through the attachment of organic matter ligands to form ae ecocorona. [ 67 ] For instance, the reduction of bactericidal activity has been attributed to organic matter providing a barrier for the interaction of NMs with bacterial cell surfaces.…”

Governing factors affecting the impacts of silver nanoparticles on wastewater treatment

“…Caenorhabditis elegans is limited (Collin et al 2016). However, another study has shown that the toxicity of silver nanoparticles to zebrafish embryos increased significantly after a sewage treatment process (Muth-Köhne et al 2013).…”