Bioaccumulation and depuration of TiO2 nanoparticles by zebrafish through dietary exposure: Size- and number concentration-resolved analysis using single-particle ICP-MS

The bioaccumulation and depuration of TiO2 nanoparticles (TiO(2)NPs) by zebrafish via the dietary exposure following the OECD Test Guideline 305 (OECD TG305) was evaluated using particle size- and number concentration-resolved analysis based on single-particle ICP-MS (spICP-MS). We found that using enzymatic digestion without H2O2 or excessive heating can recover 84.0 +/- 4.0% and 94.5 +/- 3.5% of TiO2NP mass and number concentrations from fish tissue, respectively, without altering the size distribution of parent TiO(2)NPs. OECD TG305 can allow for the evaluation of bioaccumulation and depuration of TiO(2)NPs by fish based on the particle mass and number dose metrics. The toxicokinetic modeling can reasonably describe the mass- and number-based measurement data with the derived absorption efficiency a at similar to 0.2, depuration rate at similar to 0.5 d(-1), and kinetic biomagnification factor (BMFk) at similar to 0.007 comparable with available data. The mass concentrationand number concentration-based bioaccumulation metrics including body burdens are correlated for TiO(2)NPs that remained nano-sized in vivo and exhibited marginal physicochemical alterations upon uptake by fish. The result indicates that the traditional mass concentration metric may be used to represent the fish bioaccumulation potential for chemically inert NPs like TiO2.