Environmental biomolecules affect the fate and toxicity of Cerium oxide nanoparticles for aquatic biota

The ongoing development of nanotechnology have raised several concerns regarding the potential risk of nanoparticles (NPs) for the environment, in particular the aquatic ecosystems. In the framework of a need to properly predict environmental implications of NPs, an emerging challenge is to address the complex dynamic of physicochemical and biological processes that drive NPs toxicity once they are released into natural matrices. Therefore, the objective of this study was to perform an ecotoxicological evaluation of CeO2NPs with different surface modifications, representative of NPs bio-interaction with molecules naturally occurring in water environment, to identify the role of biomolecule coating on nanoceria toxicity for aquatic organisms. Ad hoc synthesis of CeO2NPs with different coating agents such as Alginate and Chitosan was performed, and the NPs were fully characterized. The marine bacteria Aliivibrio fischeri, the freshwater crustacean Daphnia magna and the freshwater bivalve Dreissena polymorpha were used as biological models to test the different ecotoxicity of the CeO2NPs. Several endpoints were evaluated at different level of biological organization, from the molecular to the entire organism. Overall results show that the different coating affects the hydrodynamic behavior of CeO2NPs in exposure media. The different coating influenced also significantly the toxic effects of CeO2NPs in species-specific way. Specifically, in D. magna none of the CeO2NPs triggered a significant oxidative stress, but behavioral assay showed that CeO2NPs coated with Chitosan determined hyperactivity. In zebra mussel the CeO2NPs coated with Alginate affected significantly the antioxidative stress machinery. Our findings emphasize the role of environmental modification in determining the NP effects on aquatic organisms.