Environmental safety of nanocellulose: an acute in vivo study with marine mussels Mytilus galloprovincialis

The growing application of nanocellulose in various industrial sectors with potential release into the natural environment demands a safety assessment and thus ecotoxicity. Herein, we tested two types of cellulose nanofibers, non-oxidized (CNF) and TEMPO-oxidized (TOCNF), by performing acute in vivo studies with the marine bivalve Mytilus galloprovincialis at 1 mu g L(-1 )and 1 mg L-1 as resembling realistic and acute exposure scenarios, respectively. Uptake and sub-lethal biological responses (lysosomal membrane stability, neurotoxicity, oxidative stress and biotransformation) were investigated along with changes in fibers with water salinity. TOCNF resulted in more dispersion than CNF in natural sea water (NSW) probably owing to higher repulsion among fibers driven by their negative surface charges and colloidal organic material. Both CNF and TOCNF were found in mussel tissues (gills and hemolymph) using labelled stocks. The destabilization of lysosomal membranes of hemocytes was observed; similarly, the inhibition of P-gp efflux activities in the gills was stronger for CNF at the highest concentration (1 mg L-1 ). Cholinergic enzymes (ASCh-ChE activities) were inhibited in hemocytes, gills and digestive glands regardless of CNF oxidation and concentration tested. In contrast, neither oxidative stress nor biotransformation was affected in the digestive glands and gills of the mussels. Overall, the findings showed CNF uptake by marine mussels and the disruption of gill functionality and immune cells by mechanical interaction even in environmentally realistic exposure scenarios. The paucity of data on the hazards posed by CNF for aquatic species demands that safety aspects be considered in future risk assessment scenarios.