Subcellular localization of gold nanoparticles in the estuarine bivalve Scrobicularia plana after exposure through the water

Nanoparticles are extensively used particularly in biomedical and industrial applications. Because of their colloidal stability, gold nanoparticles (AuNPs) are suspected being persistent in aquatic ecosystem. Thus, the potential toxicity of gold nanoparticles is addressed by using a bivalve model Scrobicularia plana. Using AuNPs in a range of sizes (5, 15, and 40 nm), we examined their subcellular localization in gills and digestive gland. Clams were exposed to AuNPs stabilized with citrate buffer and then diluted in seawater at the concentration of 100 μg L 1. After 16 days water-borne exposure, using transmission electron microscopy, few particles were observed in gills, distributed as free in the cytoplasm, or associated with vesicles. In the digestive gland, the most striking feature was the presence of individual or small aggregates 40 nm sized within the nuclei colocalized with DNA. Depending on the size, individual or small aggregates (40 nm AuNPs) or more aggregated NPs (5 and 15 nm) were observed, with at least one of the dimensions (40–50 nm) allowing the passage through nuclear pores. Disorganization of chromatin was marked with an increase in filamentous structures. In some parts no chromatin was visible. Moreover, the perinuclear space from nuclei was enlarged in contaminated clams when compared to controls.