title: A mixture toxicity approach to predict the toxicity of Ag decorated ZnO nanomaterials.
abstract: 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.
authors.affiliation: Department of Biology, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: S L
authors.initials: SL
authors.lastname: Azevedo
authors.affiliation: Physics Department, I3N, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Holz
authors.affiliation: Physics Department, I3N, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Rodrigues
authors.affiliation: Physics Department, I3N, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Monteiro
authors.affiliation: Physics Department, I3N, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: F M
authors.initials: FM
authors.lastname: Costa
authors.affiliation: Department of Biology, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: A M V M
authors.initials: AMVM
authors.lastname: Soares
authors.affiliation: Department of Biology, CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: sloureiro@ua.pt.
authors.forename: S
authors.initials: S
authors.lastname: Loureiro
mesh_terms: D000818:Animals; D003621:Daphnia; D049329:Nanostructures / Q000633:toxicity*; D012834:Silver / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D012834:Silver; D015034:Zinc Oxide
keywords: Daphnia magna; Mixture toxicity; Nanomaterials; Nanostructures; Silver; Zinc oxide