Nanostructured titanium dioxide: fate in the aquatic environment and effects on the marine mussel mytilus edulis

Master's thesis in Biological chemistryThe rapid development of nanotechnology and the corresponding increase in the use of nanoparticles in commercial products have led to concerns about their health risks and environmental impact. As the aquatic systems act as a sink for many pollutants, nanoscale particles are likely to enter the aquatic environment and pose a threat to aquatic organisms. In particular, filter-feeding organisms, such as the blue mussel Mytilus edulis, may represent a unique target group for nanoparticle toxicology. The present study reviews the key aspects concerning fate and behavior of nanoparticles in the aquatic systems, the availability for uptake by biota and toxic effects in aquatic invertebrates, with a particular focus on nanostructured titanium dioxide (nano-TiO2). The experimental part of this study, explores the hypothesis that nano-TiO2 can cause sub-lethal impacts on Mytilus edulis exposed through the water column. The behaviour of nano-TiO2 in the aquatic system is explored and the possible effects of in vivo exposure to nano-TiO2 on mussel haemocytes (blood cells) are investigated. Mussels were exposed to different concentrations of nano-TiO2 suspensions for six days and a lysosomal biomarker was evaluated in the haemocytes. The results show a great tendency of nano-TiO2 to aggregate when dispersed in water, in particular in seawater, which will affect the subsequent fate within the aquatic environment. Significant lysosomal membrane destabilisation is found in mussel haemocytes exposed to 5 and 25 mg L-1 nano-TiO2, as evaluated by the neutral red retention time (NRRT) assay. Overall, the obtained data demonstrates that nano-TiO2 can induce sub-lethal effects in the filter-feeding organism