Les particules fines émises par l'activité humaine sont la cause de diverses pathologies pulmonaires et cardiaques. Les particules de taille inférieure à 100 nm, appelées nanoparticules, sont particulièrement nocives car une fois inhalées, elles peuvent atteindre les alvéoles pulmonaires, lieux des échanges gazeux. Dans les alvéoles, les nanoparticules entrent d'abord en contact avec le surfactant pulmonaire. Ce fluide biologique tapisse les cellules épithéliales des alvéoles sur une épaisseur de quelques centaines de nanomètres et est composé de phospholipides et de protéines, les phospholipides étant assemblés sous forme de vésicules et corps multi-lamellaires. Dans ce travail, nous avons sélectionné des nanoparticules modèles de nature différente connues pour leur toxicité cellulaire (latex, oxydes métalliques, silice). Leur interaction avec un fluide pulmonaire mimétique administré aux prématurés (Curosurf®) a été étudiée en détail par microscopie optique et électronique, et par diffusion de la lumière. Nous avons mis en évidence que cette interaction est non spécifique et d'origine électrostatique. La diversité des structures hybrides obtenues entre particules et vésicules témoigne cependant de la complexité de cette interaction. En contrôlant cette interaction, nous avons formulé des particules couvertes d’une bicouche supportée de Curosurf® qui possèdent des propriétés remarquables de stabilité et de furtivité en milieu biologique.Dans une seconde partie, nous avons étudié le rôle du surfactant pulmonaire sur l’interaction entre particules et cellules épithéliales alvéolaires (A459). A l'aide d'expériences de biologie cellulaire réalisées in vitro, nous avons observé que la présence de surfactant diminue de manière significative le nombre de particules internalisées par les cellules. Dans le même temps, nous avons constaté une augmentation importante de la viabilité cellulaire. Une conclusion majeure de notre travail concerne la mise en évidence du rôle protecteur joué par le surfactant pulmonaire dans les mécanismes d'interaction des nanoparticules avec l'épithélium alvéolaire / Particulate matter emitted by human activity are the cause of various pulmonary and cardiac diseases. After inhalation, nanoparticles (ie particles smaller than 100 nm) can reach the pulmonary alveoli, where the gas exchanges take place. In the alveoli, the nanoparticles first encounter the pulmonary surfactant which is the fluid that lines the epithelial cells. Of a few hundreds of nanometers in thickness, the pulmonary fluid is composed of phospholipids and proteins, the phospholipids being assembled in multilamellar vesicles. In this work, we considered model nanoparticles of different nature (latex, metal oxides, silica). Their interaction with a mimetic pulmonary fluid administered to premature infants (Curosurf®) was studied by light scattering and by optical and electron microscopy. We have shown that the interaction is non-specific and mainly of electrostatic origin. The wide variety of hybrid structures found in this work attests however of the complexity of the phospholipid/particle interaction. In addition, we succeeded in formulating particles covered with a Curosurf® supported bilayer. These particles exhibit remarkable stability and stealthiness in biological environment. In a second part, we studied the role of the pulmonary surfactant on the interactions between nanoparticles and alveolar epithelial cells (A459). With cellular biology assays, we observed that the number of internalized particles decreases dramatically in presence of surfactant. At the same time, we found a significant increase in the A459 cell viability. Our study shows the importance of the pulmonary surfactant in protecting the alveolar epithelium in case of nanoparticle exposure

No / The use of nanoparticles have provided numerous of advantages in medicine due to their unique physiochemical characteristics such as size, charge, shape and surface reactivity [1-4]. Understanding the interaction between engineered nanomaterials and living matter has attracted increasing attention in recent years. Toxicity of nanoparticles was studied in different cell types and cell lines. Nano-SiO2 has good stability, easy dispensability, and melting degeneration, and is widely used in rubber, paints, biomedical and biotechnology fields [5]. In this study, the LDH assay and the MTT assay were applied to evaluate the cytotoxicity of in vitro Silicon dioxide nanoparticles (SiO2-NP, 20nm) on cultured cell lines. Human lung adenocarcinoma epithelial cell line (A549) were used as a lung related cell line and human keratinocyte cell line (HaCaT) as a skin related cell line representing different uptake routes. The percentage cytotoxicity of the silicon dioxide nanoparticles was measured once cultured in a 24 hour incubation period. The concentration of the SiO2 nanoparticles chosen was 10, 50, 100 and 200µg/ml. To measure the cytotoxicity of nanoparticle on cultured cell lines, we used 104*cells/100 µl of cell culture media being placed in a 96 well rounded bottom plate with the LDH assay. The extracellular lactate dehydrogenase release was measured by using a colorimetric CytoTox 96 non-radioactive assay kit and the absorbance was recorded at 492nm. The MTT assay was used to evaluate mitochondrial activity which includes cell growth and cell death. This has been performed by inserting a premixed optimized dye solution in the culture wells. The Absorbance was recorded at 570 nm, from the recorded absorbance is directly proportional to the number of live cells. In order to maintain the cell lines, they were placed in a plastic T-75cm² tissue culture flasks grown in Dulbecco's Modified Eagle's Medium. Studies were performed in the absence of serum. Cytotoxicity was found in both cells the A549 and HaCaT cells and cytotoxicity increased as concentration of the silicon dioxide increased. The percentage cytotoxicity calculated was higher in HaCaT cells compared to the A549 cells. A cell count assay was plated in order to display the cell number of both the HaCaT and A549 cells. The cell count reaffirmed that cytotoxicity did occur as the cell count decreased as the concentration of the silicon dioxide increased compared to the control. These results show that silicon dioxide nanoparticles acted differently in two different cell types and that the metabolic rate of a cell can be used to determine the nanoparticles affect. Further understanding of the mechanism involving the ROS generation could provide more information on how silicon dioxide nanoparticles increase cytotoxicity. / Physiology 2015 conference abstract