Uptake of BDE-209 on zebrafish embryos as affected by SiO₂ nanoparticles

It was hypothesized that interactions between emerging contaminants such as decabromodiphenyl ether (BDE-209) and nanoparticles (NPs) such as nano-SiO₂ (nSiO₂), can affect contaminant transport in the aquatic environment and its ecotoxicity. This study assessed the influence of nSiO₂ on the uptake of BDE-209 by zebrafish embryo. The distribution of BDE-209 and nSiO₂ on the external chorion and the internal embryo mass (i.e., dechorionated embryo) was measured. For single exposure of nSiO₂ to zebrafish embryo, separately, results showed that nSiO₂ accumulation on the chorion surface was higher than that in the dechorionated embryo. The nSiO₂ accumulation on the chorion surface was 129-200 mg-nSiO₂/g-chorion at 48 h post fertilization, hpf, of exposure time, whereas the equilibrium adsorption of nSiO₂ on the dechorionated embryo was ca. 0.42-0.54 mg-nSiO₂/g-embryo at 6 hpf. Results showed that the formation of nSiO₂-BDE-209 associates promoted both extracellular and intracellular uptake of BDE-209 by zebrafish embryo, thereby increasing the bioconcentration of BDE-209 on the chorion surface and in embryo. The results also revealed that the accumulation of BDE-209 on the chorion was remarkably greater than that on the dechorionated embryo at 48 hpf. The uptake of BDE-209 was 17.2 ± 0.45 mg/g-chorion (or 86 ng-BDE-209/chorionated embryo) and 0.37 ± 0.01 mg/g-embryo (or 18.6 ng-BDE-209/dechorionated embryo), respectively, when co-exposure of zebrafish embryos to BDE-209 and nSiO₂. Results from the SEM and EDS analysis revealed that nSiO₂ already passed through the chorion and adhered to the embryo surface/mass.