Sofia Azevedo
@inl.int
Junior Research Fellow/Water Quality Group
International Iberian Nanotechnology Laboratory
Scopus Publications
Scopus Publications
Pedro E. Vieira, Andrea Desiderato, Sofia L. Azevedo, Patricia Esquete, Filipe O. Costa, and Henrique Queiroga
Springer Science and Business Media LLC
S.L. Azevedo, T. Holz, J. Rodrigues, T. Monteiro, F.M. Costa, A.M.V.M. Soares, and S. Loureiro
Elsevier BV
Nanotechnology is a rising field and nanomaterials can now be found in a vast variety of products with different chemical compositions, sizes and shapes. New nanostructures combining different nanomaterials are being developed due to their enhancing characteristics when compared to nanomaterials alone. In the present study, the toxicity of a nanostructure composed by a ZnO nanomaterial with Ag nanomaterials on its surface (designated as ZnO/Ag nanostructure) was assessed using the model-organism Daphnia magna and its toxicity predicted based on the toxicity of the single components (Zn and Ag). For that ZnO and Ag nanomaterials as single components, along with its mixture prepared in the laboratory, were compared in terms of toxicity to ZnO/Ag nanostructures. Toxicity was assessed by immobilization and reproduction tests. A mixture toxicity approach was carried out using as starting point the conceptual model of Concentration Addition. The laboratory mixture of both nanomaterials showed that toxicity was dependent on the doses of ZnO and Ag used (immobilization) or presented a synergistic pattern (reproduction). The ZnO/Ag nanostructure toxicity prediction, based on the percentage of individual components, showed an increase in toxicity when compared to the expected (immobilization) and dependent on the concentration used (reproduction). This study demonstrates that the toxicity of the prepared mixture of ZnO and Ag and of the ZnO/Ag nanostructure cannot be predicted based on the toxicity of their components, highlighting the importance of taking into account the interaction between nanomaterials when assessing hazard and risk.
Fabianne Ribeiro, Cornelis A.M. Van Gestel, Maria D. Pavlaki, Sofia Azevedo, Amadeu M.V.M. Soares, and Susana Loureiro
Elsevier BV
Silver nanoparticles (Ag-NP) are incorporated into commercial products as antimicrobial agents, which potentiate their emission to the environment. The toxicity of Ag-NP has been associated with the release of Ag ions (Ag+), which are more toxic to aquatic organisms than Ag-NP. In this study, a toxicokinetics approach was applied to compare the potential of Daphnia magna to accumulate Ag from either Ag-NP or AgNO3 through different exposure routes: a) water, b) diet and c) water and diet. A one-compartment kinetics model was applied to describe the development of Ag body concentrations over time and derive uptake (k1w; k1d) and elimination (k2) rate constants. Under water-only exposure, AgNO3 induced higher Ag uptake rate constants and bioconcentration factors when compared to Ag-NP. For dietary exposure, no differences in Ag concentrations in D. magna, along with the kinetics parameters, were found for both Ag forms. Simultaneous water and dietary exposures to Ag-NP induced higher Ag concentrations in D. magna compared to AgNO3. In this combined exposure, uptake from water explains most for the increase in Ag body concentration in D. magna for Ag-NP exposure, whereas uptake from the diet was the major contributor for the increase in Ag concentration in D. magna under AgNO3 exposure. Biomagnification was not observed for any of the exposure routes applied in this study, neither for Ag-NP nor for AgNO3.
Sofia L. Azevedo, Fabianne Ribeiro, Kerstin Jurkschat, Amadeu M.V.M. Soares, and Susana Loureiro
Wiley
The application of nanoparticles (NPs) in consumer products has been increasing over the past few years. Their release into the environment is likely to happen at any stage of production or during the use of products containing NPs. Zinc oxide NPs (ZnO-NP) are among the most-used NPs on the market due to its intrinsic properties, such as ultraviolet (UV) absorption. The aim of the present study was to assess the combined effects of ZnO-NP and UV radiation on 2 freshwater species: Daphnia magna and Danio rerio. The initial hypothesis was that the presence of ZnO-NP in the aquatic media would decrease the damaging effects of UV radiation for both species. The endpoints assessed for D. magna were immobilization, feeding inhibition, and reproduction output. For D. rerio, egg development was studied during 96 h and mortality, hatching delay, and abnormal development were the endpoints recorded. Combined exposures were designed based on the single toxicity of both stressors and analyzed based on the independent action concept and exploring possible deviations for synergism/antagonism, dose level, and dose ratio. Combined exposures with D. magna induced synergism on reproduction, decreasing the number of neonates produced more than expected based on both stressors' individual toxicity. Single exposures of D. rerio embryos to both stressors induced negative effects. The combined exposures caused a dose-ratio deviation pattern on mortality and hatching, with a synergism observed when ZnO-NP was the dominant stressor, changing to antagonism when UV radiation dominated the combined exposure. Regarding the results attained, studying ZnO toxicity under laboratory conditions may underestimate the risks when considering the potential interaction on effects when combined with UV radiation.