Uptake, translocation, size characterization and localization of cerium oxide nanoparticles in radish (Raphanus sativus L.)

Due to their unique physical and chemical properties, the production and use of cerium oxide nanoparticles (CeO2NPs) in different areas, especially in automotive industry, is rapidly increasing, causing their presence in the envi-ronment. Released CeO2NPs can undergo different transformations and interact with the soil and hence with plants,providing a potential pathway for human exposure and leading to serious concerns about their impact on the eco-system and human organism. This study investigates the uptake, bioaccumulation, possible translocation and local-ization of CeO2NPs in a model plant (Raphanus sativusL.), whose edible part is in direct contact with the soil wherecontamination is more likely to happen. The stability of CeO2NPs in plant growth medium as well as after applying astandard enzymatic digestion procedure was tested bysingle particle ICP-MS (SP-ICP-MS) showing that CeO2NPscan remain intact after enzymatic digestion; however, an agglomeration process was observed in the growth me-dium already after one day of cultivation. An enzymatic digestion method was next used in order to extract intactnanoparticles from the tissues of plants cultivated from the stage of seeds, followed by size characterization bySP-ICP-MS. The results obtained by SP-ICP-MS showed a narrower size distribution in the case of roots suggestingpreferential uptake of smaller nanoparticles which led to the conclusion that plants do not take up the CeO2NPs ag-glomerates present in the medium. However, nanoparticles at higher diameters were observed after analysis ofleaves plus stems. Additionally, a small degree of dissolution was observed in the case of roots. Finally, after CeO2NPs treatment of adult plants, the spatial distribution of intact CeO2NPs in the radish roots was studied by laser ab-lation ICP-MS (LA-ICP-MS) and the ability of NPs to enter and be accumulated in root tissues was confirmed.