Manufactured nanoparticles in the aquatic environment-biochemical responses on freshwater organisms: A critical overview

The enormous investments in nanotechnology have led to an exponential increase of new manufacturednano-enabled materials whose impact in the aquatic systems is still largely unknown. Ecotoxicity andnanosafety studies mostly resulted in contradictory results and generally failed to clearly identify biologi-cal patterns that could be related specifically to nanotoxicity. Generation of reactive oxygen species (ROS)is one of the most discussed nanotoxicity mechanism in literature. ROS can induce oxidative stress (OS),resulting in cyto- and genotoxicity. The ROS overproduction can trigger the induction of anti-oxidantenzymes such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidases (GPx), whichare used as biomarkers of response. A critical overview of the biochemical responses induced by the pres-ence of NPs on freshwater organisms is performed with a strong interest on indicators of ROS and generalstress. A special focus will be given to the NPs transformations, including aggregation, and dissolution,in the exposure media and the produced biochemical endpoints.