Résumé
Nanotechnology is one of the most important fields of innovation in the 21st century. Engineered nanoparticles are used in a wide range of products and industries such as cosmetics, electronics, food packaging, textiles, and even medicine. However, the rapid development of these new materials comes with the challenge of accurately assessing the risks they may pose to human health and the environment. Once released into aquatic ecosystems, nanoparticles are expected to interact with other co-occurring pollutants, including other nanoparticles. However, the effects resulting from exposure to mixtures of nanomaterials on aquatic organisms are rarely known.
In this context, the present thesis aimed to assess the effects of exposure to two of the most widely used nanoparticles, zinc oxide (ZnO) and titanium dioxide (TiO2), separately and in a mixture, using a model fish species, the rainbow trout (Oncorhynchus mykiss). Different approaches were developed to achieve this goal. First, an in vitro model was used to highlight the differences in behavior and toxicity between the individual nanoparticles and their mixture. Rainbow trout were then exposed to environmentally realistic concentrations of the two nanoparticles individually and their mixture. In the first place, the gill's innate immunity and its associated microbiota were studied as they represent the first line of defense of the organism's immune systems, but also because gills represent one of the routes of entrance for nanoparticles in the organism. A stress-on-stress approach was also employed. The trout were challenged with a pathogenic bacterium following the exposure to the nanomaterials to assess their effect on the immunocompetence of the fish.
Through this multifaceted approach, this thesis helped provide new insights into the behavior of nanoparticle mixtures and their potential for toxicity. Our findings show that exposure to nanoparticles, usually regarded as having low toxicity potential such as TiO2, may induce toxicological effects when interacting with other nanoparticles.
