The position is open under the PASSIV-ITER funded project (Passivation Strategies for tritiated and non tritiated submicronic tungsten particles based on their characterization and cyto-genotoxicity). The release of radioactive submicron particles in the environment in case of ITER Lost of Vacuum Accident=LOVA is a critical health issues namely in front of a deficit of knowledge on 1) their physicochemical characteristics, 2) their behavior in biological media and 3) their potential toxicity. The PASSIV-ITER project focuses on the characterization and toxicity evaluation of tungsten metal particles that can be produced in thermonuclear fusion reactors in order to propose passivation strategies. The considered particles (100-200 nm) can be released in low amounts in the environment even after the protective high efficiency filtration. The main objective will be to determine the particles behavior in biological media (colloidal stability, uptake, subcellular localization of particles…)

Description

The PASSIV-ITER project is offering a fixed-term post-doctoral position of 21 months appointment. The position is open under the task 2 (Particles behavior in biological media: colloidal stability, uptake, subcellular localization and transformation of particles) coordinated by the CEREGE. The work will consist in the production of stable stock suspensions prior to toxicological studies. The second objective will be to determine the behavior of the particles in biological media. Upon in contact with biological media, W particles physico-chemistry will evolve as a function of the fluctuations of the properties of bio-media (e.g. pH, dissolved oxygen, ) i.e. external nutritive media, cytoplasm, endocytosis vesicles, …. These fluctuations will affect key parameters involved in the W particle toxicity: 1) their dispersion/aggregation/settling state, 2) their solubility and 3) their redox evolution. For instance it has been shown that W (metallic form) can be oxidized in vivo leading to the formation of corroded surface layer. Size, shape and structure of the individual or aggregated W particles in the aqueous and biological (abiotic) systems will be achieved using dynamic and static light scattering. Transmission Electron Microscopy (TEM) will be used to determine at the individual size and shape, and the elemental distribution from core to the surface using Energy-dispersive X-ray spectroscopy (EDX). The surface charge of the W particles will be studied by measuring the electrophoretic mobility of particles as a function of pH and salinity. W particles partial dissolution will be followed using ICP (Inductively Coupled Plasma)-MS. Crystal structure of the particles will be obtained by X-Ray Diffraction (XRD) and micro-XRD (50 µm spot size). Imaging and quantification at the tissue level: X-ray imaging techniques will be used at the laboratory scale. Micro-X ray fluorescence, micro-XANES and micro-XRD will enable to locate the W particles and determine the evolution of the redox state and atomic structure with living cells. CEREGE possess both laboratory µ-XRF and µ-XRD, which allow analyzing a significant amount of samples and to be less dependent on synchrotron time allocation. Imaging and quantification at the cellular level: One of the most valuable aspect of PASSIV-ITER to detect & locate the W particles at the cellular level, will take advantage of our new Nano-ID 3D X-ray imaging platform. Indeed the two X-ray CT tomographs coupled to 2D- X-ray micro-spectroscopes installed at the CEREGE represent one of the best Imaging platform in Europe (except synchrotron facilities). The High-resolution 3D X-Ray Microscopes enable a sensitive detection and location of particles in heterogeneous samples. The spatial resolution down to 50 nm makes it possible to locate and visualize W particles at the cellular level. 

Applicants must contact the CEREGE to discuss research opportunities. Dr. Jerome Rose rose@cerege.fr.