Multigenerational exposures of Daphnia magna to pristine and aged silver nanoparticles: epigenetic changes and phenotypical ageing related effects

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, we systematically evaluate the effects of ‘pristine’ and ‘aged’ Ag NPs 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 were investigated. Parental exposure to ‘pristine’ Ag NPs had an inhibitory effect on reproduction, induced expression of antioxidant stress related genes and reduced survival. Pristine Ag NPs also induced morphological changes including tail losses and lipid accumulation associated with aging phenotypes in the heart, abdomen and abdominal claw. These effects were 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 showed considerably reduced toxicological effects in continuously exposed generations and to the recovery generations.