No abstract

A nanometric revolution is underway, promising technical innovations in a wide range of applications and leading to a potential boost in environmental discharges. The propensity of nanoparticles (NPs) to be transferred throughout trophic chains and to generate toxicity was mainly assessed in primary consumers, whereas a lack of knowledge for higher trophic levels persists. The present study focused on a predatory fish, the European eel (Anguilla anguilla) exposed to gold NPs (AuNPs; 10 nm, polyethylene glycol-coated) for 21 d at 3 concentration levels in food: 0 (NP0), 1 (NP1), and 10 (NP10) mg Au kg −1. Transfer was assessed by Au quantification in eel tissues, and transcriptomic responses in the liver and brain were revealed by a high-throughput RNA-sequencing approach. Eels fed at NP10 presented an erratic feeding behavior, whereas Au quantification only indicated transfer to intestine and kidney of NP1-exposed eels. Sequencing of RNA was performed in NP0 and NP1 eels. A total of 258 genes and 156 genes were significantly differentially transcribed in response to AuNP trophic exposure in the liver and brain, respectively. Enrichment analysis highlighted modifications in the immune system-related processes in the liver. In addition, results pointed out a shared response of both organs regarding 13 genes, most of them being involved in immune functions. This finding may shed light on the mode of action and toxicity of AuNPs in fish.

According to the US National Nanotechnology Initiative, nanoparticles are a set of solid particles with a diameter ranged from 1 to 100 nm. Numerous domains employ nanoparticles (such as industry, cosmetic, construction, medicine…) due to their specific properties. The significant arise of nanomaterials application leads to a boost of environmental discharges and especially in aquatic systems which represent an important pollutants receptacles. Nevertheless, the lack of knowledge about the toxicity of nanomaterials can be detrimental for the aquatic ecosystems sustainability. Trophic transfer is often referred as an important pathway of nanoparticles contamination in aquatic systems being reportedly the main exposure route to organisms. Among their great variety of nature and characteristics, gold nanoparticles (AuNPs, PEG coating, diameter 10nm) have been chosen as model contaminant due to their high stability in solution. This work aims to characterize: (i) AuNPs transfer within food chain and (ii) a histological study of AuNPs damages in fish. Thereby natural river biofilms contaminated in laboratory for 48h at environmental AuNPs' concentrations were grazed by the fish Hypostomus plecostomus during a 21‐days laboratory experiment. Gold analyses (by atomic absorption spectroscopy) revealed that biofilms presented a high AuNPs retention capacity. Secondly, results point out that AuNPs were effectively transferred from natural biofilms to the grazer fish showing their ability to enter the food chain. Regarding AuNP fish distribution, organs involved in metabolism and excretion ( i.e . liver and kidney) presented a significant bioaccumulation. Moreover, transmission electron microscopy observations showed tissue alterations indicating inflammatory responses for all organs studied. AuNPs appeared to be: (a) distributed by the circulatory system into fish organs without entering the erythrocytes and (b) not degraded once internalized by the fish.