Distinct transcriptomic responses of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles

Abstract

Manufactured nanoparticles (MNP) rapidly undergo aging processes once released from products. Silver sulfide (Ag2S) is the major transformation product formed during the wastewater treatment process for Ag-MNP. We examined toxicogenomic responses of pristine Ag-MNP, sulfidized Ag-MNP (sAg-MNP), and AgNO3 to a model soil organism, Caenorhabditis elegans. Transcriptomic profiling of nematodes which were exposed at the EC30 for reproduction for AgNO3, Ag-MNP, and sAg-MNP resulted in 571 differentially expressed genes. We independently verified expression of 4 genes (numr-1, rol-8, col-158, and grl-20) using qRT-PCR. Only 11% of differentially expressed genes were common among the three treatments. Gene ontology enrichment analysis also revealed that Ag-MNP and sAg-MNP had distinct toxicity mechanisms and did not share any of the biological processes. The processes most affected by Ag-MNP relate to metabolism, while those processes most affected by sAg-MNP relate to molting and the cuticle, and the most impacted processes for AgNO3 exposed nematodes was stress related. Additionally, as observed from qRT-PCR and mutant experiments, the responses to sAg-MNP were distinct from AgNO3 while some of the effects of pristine MNP were similar to AgNO3, suggesting that effects from Ag-MNP is partially due to dissolved silver ions.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects—An updated review

“…Considering that non‐labile transformation end products such as AgCl and Ag 2 S are expected to be stable in the environment and to have relatively low bioavailability (Lombi et al ; Donner et al ; Doolette et al , ), the risk to terrestrial ecosystems posed by Ag NMs would appear to be low, although uncertainties related to longer‐term transformations, dosimetry, are also relevant. This conclusion has been further supported by soil‐based studies demonstrating that Ag 2 S NMs presented minimal hazard to plant–microorganism symbioses (Judy et al , ), crop plants (Doolette et al ; Wang et al ), soil microorganisms (Judy et al ; Doolette et al ; Moore et al ), and soil invertebrates (Starnes et al , ).…”

Materials and toxicological approaches to study metal and metal-oxide nanoparticles in the model organism Caenorhabditis elegans

“…Starnes et al investigated the effect of Ag-NP sulfidation, a major transformation occurring in the wastewater treatment process, and reported reduced bioavailability, lower toxicity and distinct toxicity mechanisms of sulfidized Ag-NPs compared to bare particles. [39, 40] Surface engineering can also result in enhanced bioavailability; e.g., Kim et al conjugated nano-Pt with HIV-1 TAT fusion protein, a cell-penetrating peptide, which resulted in an antioxidant activity 100 times higher than unconjugated Pt-NPs. [42]…”

“…In the case of metals, silver NPs (Ag-NPs) have been the most investigated. [32, 33, 35–40] Fewer efforts have been devoted to other metals such as gold (Au-NPs),[32, 41] platinum (Pt-NPs)[31, 42] and copper (Cu-NPs). [25] Published evaluations of metal oxide NPs include titania (TiO 2 -NPs), ceria (CeO 2 -NPs), iron oxide (Fe 2 O 3 -NPs), aluminum oxide (Al 2 O 3 -NPs), and zinc oxide (ZnO-NPs) nanoparticles, among other compositions.…”

Toxicogenomics of iron oxide nanoparticles in the nematodeC. elegans

“…, Gonzalez-Moragas et al, 2015a Several toxicogenomic studies have provided evidence that titanium oxide, gold and silver nanoparticles induce nanotoxic mechanisms in C. elegans. (Tsyusko et al, 2012, Rocheleau et al, 2015, Starnes et al, 2016 However, further research on different NP composition, sizes and surface properties is required to correlate the physicochemical properties of the materials with the molecular effects. Starnes et al examined the toxicogenomic responses of pristine Ag-NP, sulfidized Ag-NPs, and AgNO 3 in C. elegans.…”

“…However, these mechanistic cues should be confirmed by post-hoc A c c e p t e d M a n u s c r i p t histological analysis or specific genetic experiments to test the importance and significance of the pathways identified. (Poma and Di Giorgio, 2008, Elingarami et al, 2013, Tino et al, 2014 Nanotoxicogenomic studies can be performed in nanoparticle-treated cells, simple invertebrates (Poynton et al, 2012, Starnes et al, 2016 or more complex vertebrates (Truong et al, 2013, Teeguarden et al, 2014. Invertebrate models share many biological traits with…”