Size and surface-dependent effects of silver nanoparticles on Gammarus fossarum (Crustacea, Amphipoda): link between physiological and behavioural responses
Mehennaoui K.(1, 2), Georgantzopoulou A.(1),Cambier S.(1), Garaud M.(2), Andreï J.2, Felten V.(2), Serchi T.(1), Contal S.(1), Ziebel J.(1), Guignard C.(1), Balachandran YL.(3), Pain-Devin S.(2), Giambérini L.(2), Gutleb A.C.(1)
1: Luxembourg Institute of Science and Technology, Département Environnement et Agro-biotechnologie (EVA). 41, rue du Brill – L-4422 Belvaux. (+352) 47 02 61-423
2: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360 Campus Bridoux - 8, rue du Général Delestraint, F-57070 Metz
3: Department of Biotechnology, Bharathiar University, Coimbatore, Tamilnadu, India
Silver nanoparticles (AgNPs) are widely used in daily life products for their antibacterial properties. Their increased and non-regulated use will lead to their release in aquatic environments. The aim of this study was to investigate the toxic effects of different sizes of “conventionally synthetized” (AgNPs 20 nm and 200 nm) and “green synthetized” (AgNPs 23 nm and 27 nm) particles on survival, physiological and behaviour responses of Gammarus fossarum.
G. fossarum was selected for its wide distribution, ease of sampling and identification, sensitivity to many pollutants in addition to its major functional role in freshwater ecosystems.
A first experiment aimed at determining the toxicity of AgNPs and AgNO3, and to compare the sensitivity of two different populations of G. fossarum (G.f1 and G.f2). The results showed that, after 72h exposure, AgNO3 was the most toxic form for both populations, followed by AgNPs 23 nm, AgNPs 27 nm and AgNPs 20 nm. No mortality was recorded for animals exposed to AgNPs 200 nm. G.f2 appeared to be the most sensitive population and was selected for the second experiment.
Thus, G.f2 individuals were exposed during 72h to 1 and 3µg.L-1 of AgNO3, AgNPs 20 nm, AgNPs 23 nm and AgNPs 27 nm. The selected concentrations represented the EC5 and EC20 of AgNPs 23 nm. Effects on survival, osmoregulation, antioxidant responses, defence mechanisms, cellular damage, energy reserves and behaviour were investigated.
AgNO3 and AgNPs 23 nm led to a significant decrease in survival rates, osmoregulation and locomotor activity. The other targeted responses were not impacted. AgNPs 20 nm and AgNPs 27 nm had no effects on any of the studied responses. Soluble Ag from AgNPs in exposure medium were assessed using ICP-MS. The amount of soluble Ag was under the limit of quantification.
The results showed that AgNO3 and AgNPs 23 nm altered osmoregulation which appeared to be an effective marker as it indicates the physiological health status of G. fossarum. Locomotor activity, which was the most impacted response, reflects the potential effects of AgNPs 23 nm at the population level.
In addition to highlighting the potential of G. fossarum as a model organism in nanotoxicology, this study illustrates that AgNO3 and AgNPs 23 nm act at very low concentrations and their toxicity is highly dependent on their physico-chemical properties. Indeed, in addition to the size, this study demonstrated the importance of the methods of synthesis in nano-ecotoxicology.