Coating of Cerium oxide nanoparticles with natural molecules modifies the toxic effects towards Mytilus galloprovincialis

In the framework of a need to properly predict environmental implications of nanoparticles (NPs), an emerging challenge is to address the complex dynamic of physicochemical and biological processes that drive NP’s toxicity once they are released into natural matrices. In particular this study focused on the effects of surface coating, acquired through the interaction with natural biomolecules, on the behaviour and ecotoxicity of NPs. To this aim CeO2NPs were ad hoc synthesized with different coating agents such as Alginate and Chitosan, two abundant polysaccharides in the aquatic environment. The mussel Mytilus galloprovincialis was used as a biological model to test whether these surface modifications could influence NP’s fate, uptake and toxicity. Mussels were exposed to 100 ug/L of CeO2NPs Naked and coated with the two polysaccharides for 7 days and to 1 ug/L for 28 days. A suite of biomarkers related to oxidative stress/damage and energy metabolism was applied. Results showed that the different coating determined different hydrodynamic behavior and stability in water. The coatings affected also CeO2NPs toxicological outcomes as exposure to CeO2NPs coated with Alginate triggered oxidative damage, while mussels exposed to CeO2NPs coated with Chitosan showed increase of antioxidant enzyme activities. Our results highlight that interactions with biomolecules largely present in the aquatic environment could be a driver of NPs’ toxicity.