CNRS Université Bordeaux

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Toxicity of supracolloidal aggregates with living cells

Malak SAFI, Laboratoire Matière et Systèmes Complexes, Université Paris 7 Diderot
Vendredi 28 Octobre 2011 à 11h00 - Salle des Séminaires du CENBG

Engineered inorganic nanoparticles are ultrafine colloids of nanometer dimensions with highly ordered crystallographic structures. During the last years, these nano-objects have attracted much interest for applications in material science and biomedicine. In biomedicine for instance, magnetic particles are used for imaging, diagnosis, prevention of infectious diseases and therapy. While the majority of biomedical studies, including cancer therapies by hyperthermia are based on spherical superparamagnetic nanoparticles, relatively few applications are using the favorable features of magnetic nanowires. One of these features is the possibility to rotate the nanowires by an external field at a given frequency and to destroy the intercellular matrix of tumor cells. Many questions have been raised concerning the risks on human health following exposure to such nano-objects in comparison to asbestos. Thus, we have investigated the cytotoxicity and internalization of superparamagnetic nanowires, with diameter of 200 nm and lengths between 1 and 30 microns. The wires were made from controlled aggregation of sub-10 nm iron oxide nanoparticles. In a first report, we shown that the nanowires inherited the superparamagnetic properties of the nanoparticles as they can be rotated by the application of an external magnetic field. Toxicity assays were performed on NIH/3T3 mouse fibroblasts. Electron and optical microscopy allow to visualize the wires internalized by the cells and to determine the number of wires per cell. Roughly 1/3 of the total incubated wires were uptaken by the fibroblasts. Inside the cells, the majority of the nanowires are found to be dispersed in the cytosol and not in endosomes, suggesting an entering mechanism based on the perforation of the outer membrane. The mechanism of internalization will be discussed. We have also evaluated the in vitro toxicity of the magnetic nanowires by using MTT, neutral red and proliferation assays. The toxicity assays reveal that the supracolloidal aggregates are biocompatible, as exposed cells remain 100% viable relative to controls over a period of a week.