Intracellular uptake and associated toxicity of silver nanoparticles in Caenorhabditis elegans.
Silver nanoparticles (AgNPs) are frequently used as antimicrobials. While the mechanism(s) by which AgNPs are toxic are unclear, their increasing use raises the concern that release into the environment could lead to environmental toxicity. We characterized the physicochemical behavior, uptake, toxicity (growth inhibition), and mechanism of toxicity of three AgNPs with different sizes and polyvinylpyrrolidone (PVP) or citrate coatings to the nematode Caenorhabditis elegans. We used wild-type (N2) C. elegans and strains expected to be sensitive to oxidative stress (nth-1, sod-2 and mev-1), genotoxins (xpa-1 and nth-1), and metals (mtl-2). Using traditional and novel analytical methods, we observed significant aggregation and extra-organismal dissolution of silver, organismal uptake and, in one case, transgenerational transfer of AgNPs. We also observed growth inhibition by all tested AgNPs at concentrations in the low mg/L levels. A metallothionein-deficient (mtl-2) strain was the only mutant tested that exhibited consistently greater AgNP sensitivity than wild-type. Although all tested AgNPs were internalized (passed cell membranes) in C. elegans, at least part of the toxicity observed was mediated by ionic silver. Finally, we describe a modified growth assay that permits differentiation between direct growth-inhibitory effects and indirect inhibition mediated by toxicity to the food source.
Meyer
Joel N
JN
Nicholas School of the Environment and Center for the Environmental Implications of NanoTechnology, Duke University, Durham, NC 27708-0328, United States. joel.meyer@duke.edu
Lord
Christopher A
CA
Yang
Xinyu Y
XY
Turner
Elena A
EA
Badireddy
Appala R
AR
Marinakos
Stella M
SM
Chilkoti
Ashutosh
A
Wiesner
Mark R
MR
Auffan
Melanie
M
D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism / Q000633:toxicity*; D017173:Caenorhabditis elegans / Q000187:drug effects* / Q000378:metabolism; D004785:Environmental Pollutants / Q000378:metabolism / Q000633:toxicity*; D053768:Metal Nanoparticles / Q000633:toxicity*; D018384:Oxidative Stress; D011188:Potassium / Q000737:chemistry; D011205:Povidone / Q000737:chemistry; D012834:Silver / Q000378:metabolism / Q000633:toxicity*
D000890:Anti-Infective Agents; D004785:Environmental Pollutants; D012834:Silver; D011205:Povidone; D011188:Potassium