The mechanism of silver nanoparticle toxicity is dependent on size and surface coating in Caenorhabditis elegans

Monday, December 13, 2010

12:00 pm to 1:00 pm
1441 CIEMAS/Fitzpatrick Center


Xinyu Yang

Xinyu Yang is a Ph.D. student in the Nicholas School of the Environment

Abstract: The rapidly increased application of silver nanoparticles (AgNPs) in consumer products and medical industry has raised concerns for both ecological and human health. A key question is whether AgNP toxicity is specific to nanoparticulate silver, or results from dissolution of silver ions. Furthermore, since AgNPs are produced in many sizes and with many coatings, and since their behavior changes in different media, it is important to understand how these variables modulate toxicity. We found that a lower ionic strength medium resulted in greater toxicity (measured as growth inhibition) to Caenorhabditis elegans, and that both particle size and coating influence AgNP toxicity. The size-toxicity relationship is not linear, although there was a strong general trend towards increased toxicity at smaller sizes. We then used biomarkers (indicators of oxidative stress), pharmacological rescue (trolox and N-acetylcysteine), genetic approaches (analysis of metal-sensitive and oxidative stress-sensitive mutants), and physicochemical characterization (analysis of uptakes and dissolution of AgNPs) to investigate the mechanism of toxicity of differentially coated and sized AgNPs. All of these approaches indicated that the more toxic AgNPs acted largely via release of silver ion, while the less toxic (typically larger and/or more likely to aggregate) AgNPs acted both via ion release and via a non-ionic effect, likely generation of reactive oxygen species.