Long-term effect of cationic amino-modified polystyrene nanoparticles in brine shrimp Artemia franciscana: physiological and biochemical responses

Abstract

Nowadays, plastic litter is recognized as one of the main threats for marine ecosystems worldwide. Micro- ( 5 mm) and nanoplastics ( 1 μm) of polystyrene (PS) have been identified among the most common polymers found in marine litter. Brine shrimp Artemia has been already recognized as a suitable model among planktonic species for studying the impact of polystyrene nanoparticles (PS NPs), both using short- and long-term bioassays. Our study aims to evaluate the sub-lethal effects of 50 nm cationic amino-modified (PS-NH2) NPs in Artemia franciscana after long-term exposure (14 d). Toxicity tests were performed on newly hatched nauplii (Instar I), which were exposed to suspensions of PS-NH2 (0.1, 1 and 3 μg/mL) in natural sea water (NSW). Nauplii survival, growth and feeding behavior were investigated over longterm exposure. Further, NP toxicity was evaluated using a biochemical approach at the organism level looking at target enzymes already shown to be affected by PS-NH2 in previous short-term exposure studies. Activities of carboxylesterases (CbE), cholinesterases (ChE), glutathione-Stransferase (GST), catalase (CAT), lipid peroxidation (LP) as well as heat shock protein (HSP70) content all involved in important physiological and biochemical processes, such as biotransformation of xenobiotics, neuronal transmission and oxidative stress, were measured. Long-term exposure to PS-NH2 suspensions produced significant changes in survival and growth but not in feeding behavior of A. franciscana. All biomarkers studied were also significantly affected in organisms exposed to PS-NH2. These results confirm the stress responses already observed in previous short-term studies and provide new insight into the sub-lethal effects in term of neurotoxicity and oxidative stress of cationic nanoplastics to microcrustaceans, such as Artemia, over a prolonged exposure.