title: Solubility-driven toxicity of CuO nanoparticles to Caco2 cells and Escherichia coli: Effect of sonication energy and test environment.
abstract: Due to small size and high surface energy nanoparticles (NPs) tend to agglomerate and precipitate. To avoid/diminish that, sonication of NPs stock suspensions prior toxicity testing is often applied. Currently, there is no standardized particle sonication protocol available leading to inconsistent toxicity data, especially if toxicity is driven by NPs' dissolution that may be enhanced by sonication. In this study we addressed the effect of sonication on hydrodynamic size (Dh), dissolution and toxicity of copper oxide (CuO) NPs to mammalian cell line Caco-2 in vitro and bacteria Escherichia coli in the respective test environments (cell culture MEM medium, bacterial LB medium and deionised (DI) water). NPs were suspended using no sonication, water bath and probe sonication with different energy intensities. Increased sonication energy (i) decreased the Dh of CuO NPs in all three test environments; (ii) increased dissolution of NPs in MEM medium and their toxicity to Caco-2; (iii) increased dissolution of NPs in LB medium and their bioavailability to E. coli; and (iv) had no effect on dissolution and antibacterial effects of NPs in DI water. Thus, to reduce variations in dissolution and toxicity, we recommend sonication of NPs in DI water following the dilution into suitable test media.
authors: Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia. Electronic address: aleksandr.kakinen@kbfi.ee.
authors: Aleksandr
authors: A
authors: Käkinen
authors: Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
authors: Anne
authors: A
authors: Kahru
authors: Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
authors: Helen
authors: H
authors: Nurmsoo
authors: Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
authors: Anna-Liisa
authors: AL
authors: Kubo
authors: Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia. Electronic address: olesja.bondarenko@kbfi.ee.
authors: Olesja M
authors: OM
authors: Bondarenko
mesh_terms: D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D003300:Copper / Q000737:chemistry / Q000633:toxicity*; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D012995:Solubility; D013010:Sonication
chemical_list: D003470:Culture Media; D003300:Copper; C030973:cupric oxide
keywords: Bioavailability; Cu ions; Harmonization; Speciation; Standardized operational procedures; Ultrasonication