Bioaccessibility and cellular transport study of silver and titanium dioxide nanoparticles from exposed seaweed and mussels using Caco-2 cells

Bioavailability studies on pollution pre-concentrator organisms such as algae and mussels are necessary to ensure food safety, particularly in the case of nanomaterials whose industrial applications have increased in recent years. Thus, the bioaccessibility and the bioavailability of total Ag and Ti and AgNPs and TiO₂NPs from raw and cooked seaweed (Palmaria palmata and Ulva sp.) and cooked mussels (Mytilus edulis) exposed to 1.0 mg L^-1 of 15 nm PVP-AgNPs, 1.0 mg L^-1 of 25 nm citrate-TiO₂NPs, or 1.0 mg L^-1 5 nm citrate-TiO₂NPs, for 28 days, were evaluated. Samples were subjected to an in vitro process simulating human gastrointestinal digestion while cell transport from the intestinal lumen to the bloodstream was mimicked using Caco-2 cell cultures. Total Ag and Ti in the digest samples, the bioaccessible fractions, the apical, and basolateral fractions were determined by ICP-MS, while AgNPs and TiO₂NPs were determined by single-particle-ICP-MS (SP-ICP-MS). Finally, the presence of nanoparticles in the Caco-2 cells was verified by single-cell-ICP-MS (SC-ICP-MS). AgNP bioaccessibility ratios were between 22% and 97% for seaweed and 18% for mussels, while for TiO₂NPs were between 17% and 81% (seaweed) and 76% and 100% (mussels). Nanoparticle cellular transports were in all cases less than 1%. However, the mass percentages of Ag as NPs and Ti as NPs in the Caco-2 cells for raw and cooked seaweed were 9% and 7% and 20% and 6%, respectively. These results confirm a small transport of the nanoparticles through the Caco-2 cells under the proposed experimental conditions.