Effects of nanoparticles exposure in the mussel Mytilus galloprovinciali

Nanotechnology is rapidly developing and attracting attention due to the exploitation of the novel materials at the nanoscale for application within biomedical, cosmetic, electronic, energy production and environmental sectors. Increased production and widespread use of these nanomaterials result in their release into the environment; nevertheless, the knowledge of their behaviour in aquatic systems is scarce. Accordingly, this thesis assessed the effects of two commercially available nanoparticles, copper oxide (CuO NPs) and silver nanoparticles (Ag NPs), using mussels Mytilus galloprovincialis as bioindicators. To understand the uptake, accumulation and effects of these NPs, mussels were exposed to a realistic environmental concentration of 10 !g.L-1 of CuO (31 +/- 10 nm) and Ag NPs (<100 nm) for 15 days, comparative to their ionic counterparts. NPs were characterized and biomarkers of oxidative stress, metal exposure, genotoxicity and neurotoxicity evaluated in mussel tissues. To identify pathways of NP exposure and detect new biomarkers, a proteomic approach was undertaken. Oxidative stress is the major NP-induced toxicity, but with distinct modes of action. Gills are more susceptible to oxidative stress while the digestive gland is the preferential site for NPs accumulation. The oxidative (enzymatic activation/inhibition, metallothionein induction and lipid peroxidation), genotoxic (DNA strand breaks) and neurotoxic (acetylcholinesterase inhibition) changes suggest that NPs toxicity is associated with ROS that induced a cascade of pathways (via nucleus and mitochondria) that ultimately lead to apoptosis but by different mechanisms. New biomarkers candidates were identified: caspase 3/7-1, cathepsin-L and zinc-finger protein for CuO NPs and precollagen-P, major vault protein and ras partial for Ag NPs exposure. Overall, these results show that even though oxidative stress and apoptosis are similar outcomes for NP toxicity, particle composition, size, solubility, aggregation and chemistry are key elements for determining their mode of action. This study contributed to understand the CuO and Ag NPs behaviour, bioavailability and toxicity in aquatic systems and their uptake and effects in filter-feeding organisms.