Ecotoxicité des nanoparticules et des sous produits d'altération de dioxyde de titane sur le ver de terre, Eisenia fetida

Abstract : The amount of nanomaterials produced annually is constantly increasing and this trend may result in a strong input of manufactured nanoparticles in air, water, soils, and therefore in contact with organisms. Among the manufactured nanoparticles, titanium dioxide (TiO2) nanoparticles have been produced massively for their photocatalytic properties and UV absorption ability. Surprisingly, ecotoxicological risks associated with TiO2 nanoparticles and TiO2 byproducts resulting from the alteration and aging of nanomaterials are poorly documented on terrestrial organisms. The potential toxicity of TiO2 nanoparticles and TiO2 byproducts on the earthworm Eisenia fetida has been evaluated, using different approaches: the first with in vitro assay to determine toxicity of TiO2 nanoparticles (1 to 25 µg/ml), the second with in vivo exposure of earthworm to liquid medium contaminated by TiO2 byproducts (0.1 to 10 mg/l) and the third with in vivo exposure to artificial soil contaminated by TiO2 nanoparticles (2 to 200 mg/kg) or TiO2 byproducts (2-20 mg/kg). Ecotoxicity of TiO2 nanomaterials was determined using a battery of biomarkers at different biological levels: survival and reproduction at individual level, cell viability (MTT and LDH assay), phagocytosis and apoptosis at cellular level, mRNA expression of detoxification (metallothioneins, GST), antioxidant (SOD, CAT) and immunes genes (CCF and fetidins) by RT-qPCR at molecular level. Our results showed that TiO2 nanoparticles were internalized by immune cells (in vitro assay) and titanium was bioaccumulated by worms exposed to TiO2 byproducts in artificial exposure assay (liquid medium). Molecular biomarkers (metallothioneins, CCF and fetidins) were sensitive to TiO2 nanoparticles after in vitro exposures, while both molecular (metallothioneins and SOD) and cellular (phagocytosis, apoptosis) biomarkers were sensitive to TiO2 byproducts in liquid medium after only 24 hours of exposure. In contrast, in more realistic conditions of exposure, no effect on life-history traits or molecular biomarker were noticed on earthworms exposed to soils contaminated by TiO2 nanoparticles or byproducts. A low bioavailability of TiO2 nanomaterials in soil matrixes could explain the lack of effect at the concentrations tested. These results underline the necessity to evaluate mobility, behaviour and bioavailability of nanomaterials in soil matrixes before their ecotoxicity assessment.
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Emilie Bigorgne. Ecotoxicité des nanoparticules et des sous produits d'altération de dioxyde de titane sur le ver de terre, Eisenia fetida. Sciences agricoles. Université Paul Verlaine - Metz, 2011. Français. ⟨NNT : 2011METZ034S⟩. ⟨tel-01749081⟩

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