Evidence of one-way flow bioaccumulation of gold nanoparticles across two trophic levels

This work reports a one-way flow bioaccumulation of gold nanoparticles (AuNPs) in aquatic organisms between two trophic levels. First, Dunaliella salina cells were exposed to citrate-capped AuNPs at different concentrations and during distinct exposure periods to assess internalization and behavior. Afterward, D. salina was incubated with both citrate-capped and functionalized (PEGylated) AuNPs for 24 h and later fed to Mytilus galloprovincialis. Analysis was carried out to assess Au content, histological differences and oxidative stress. These algae were fed to the model organism M. galloprovincialis (Mediterranean mussel) as it is considered of major importance for assessing toxic effects and bioaccumulation of different pollutants in aquatic environments. Elemental Au analysis revealed an uptake of about 76 % of the initial amount of AuNPs (and 36 % for PEGylated AuNPs) in microalgae. Mussel gills and digestive gland showed variable Au content in individuals fed with D. salina previously exposed to AuNPs. No significant morphological alterations were observed in D. salina or mussel digestive glands. Glutathione-s-transferase activity and total antioxidant capacity were assessed as oxidative stress biomarkers showing that AuNPs are not prone to trigger the induction of defenses against oxidative stress.