Improvement of in vitro methods to study nanoparticles toxicology Application to gold and cobalt nanoparticles

(eng) Nanotechnology represents a new emerging field in different applications that involves the development, manufacturing of materials in the sub micron range down to the nanometers (nm) range scale. These new materials will soon be able to improve our everyday life and the advantages can be considered enormous and, in the near future, the development of nanotechnologies is expected to have a large socio-economical impact in practically all industrial activity fields. Anyway, the potential risk of these nanomaterials for human health and environment is not clear and remains largely unknown. This work aims to propose, develop and demonstrate the possible use of in vitro methods and systems in order to better understand the toxicology of nanoparticles (NPs) that is a research field in which an integrated approach based on the use of different techniques (e.g. to assess physicochemical characterization of NPs) is required. In particular, four in vitro models were taken into consideration in this study: (i) Balb/3T3 immortalised mouse fibroblasts; (ii) Peripheral Blood Mononuclear Cells (PBMC); (iii) Madin-Darby canine kidney epithelial cells (MDCK cells) and (iv) Human hepatoma cells (HepG2 cells). Considering different in vitro toxicological end-points, the use of in vitro methods was demonstrated to possibly explain some of the effects of Cobalt NPs (Co-nano) and Gold NPs (AuNPs). In particular, standard in vitro tests as well as original newly developed methods were used to assess the cell viability as end point of basal cytotoxicity; morphological transformation for carcinogenic potential; single strand and double strand DNA breaks and chromosomal aberrations for genotoxicity and cellular internalization for biokinetics and NPs intracellular fate. Briefly, the results showed uptake of both NPs; no basal cytotoxicity induced by AuNPs, while cytotoxicity, carcinogenic potential and genotoxicity were demonstrated for Co-nano. Concerning Co-nano, basal cytotoxicity was also observed by an impedance-based assay that can be considered as a new approach for the assessment of basal cytotoxicity induced by chemicals and that was demonstrated to be comparable with standard in vitro methods during this thesis work. This approach was also successfully applied to NPs. Our study also points out that any NPs toxicological study requires a preliminary careful physicochemical characterization of the NPs used, in order to highlight and understand their mechanisms of action. Moreover the possibility to use in vitro methods could be pointed out especially due to the fact that they can be considered "easier" to use in comparison to in vivo approaches, although the latter remain unavoidable, in particular to find the potential effect liked to the exposure routes in the body and the target organs. This work shows how complicated NPs toxicology research is and confirms the need for integrated approaches and discussion/agreement among scientists.