Abstract
Engineered nanoparticles (NPs) undergo physical, chemical, and biological transformation after environmental release, resulting in different properties of the "aged" versus "pristine" forms. While many studies have investigated the ecotoxicological effects of silver (Ag) NPs, the majority focus on "pristine" Ag NPs in simple exposure media, rather than investigating realistic environmental exposure scenarios with transformed NPs. Here, the effects of "pristine" and "aged" Ag NPs are systematically evaluated with different surface coatings on Daphnia magna over four generations, comparing continuous exposure versus parental only exposure to assess recovery potential for three generations. Biological endpoints including survival, growth and reproduction and genetic effects associated with Ag NP exposure are investigated. Parental exposure to "pristine" Ag NPs has an inhibitory effect on reproduction, inducing expression of antioxidant stress related genes and reducing survival. Pristine Ag NPs also induce morphological changes including tail losses and lipid accumulation associated with aging phenotypes in the heart, abdomen, and abdominal claw. These effects are epigenetic remaining two generations post-maternal exposure (F2 and F3). Exposure to identical Ag NPs (same concentrations) aged for 6 months in environmentally realistic water containing natural organic matter shows considerably reduced toxicological effects in continuously exposed generations and to the recovery generations.
Highlights
Multigenerational Exposures of Daphnia Magna to Pristine and Aged Silver Nanoparticles: Epigenetic Changes and Phenotypical Ageing Related Effects
Both pristine and aged Ag NPs used in this study were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS) in the standard Daphnia culture media (HH Combo) and in synthetic Class V water
Multi-generational exposure of Daphnia to acute EC30 concentrations of Ag NPs with various capping agents/surface chemistries induced impacts on all life history traits (growth, reproduction) in the directly exposed generations, inducing epigenetic changes that persisted in the subsequent three recovery generations when exposed in a standard high-hardness medium (HH combo) to both the pristine NPs and those aged for 6 months in the medium
Summary
Both pristine and aged Ag NPs used in this study were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS) in the standard Daphnia culture media (HH Combo) and in synthetic Class V water. Ageing in the HH combo medium and Class V water had differential effects on the Ag NPs, showing increased sizes for all aged Ag NMs in comparison to their pristine forms
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