Uptake of Ag and TiO2 nanoparticles by zebrafish embryos in the presence of other contaminants in the aquatic environment

The present study aimed at evaluating the uptake of two widely used nanoparticles (NPs), namely, silver (Ag) and titanium dioxide (TiO2) NPs by zebrafish embryos under different simulated environmental conditions. AgNPs and TiO2NPs are widely used in a number of consumer products, and are thus likely to be introduced into the aquatic environments from both domestic and industrial sources. These NPs could interact with other contaminants in aquatic systems, which could affect their uptake by fish and biodistribution kinetics. To provide insights into these interactions, uptake studies were conducted in the presence of 12 elements and 3 major inorganic nutrients using (1) single (AgNPs and TiO2NPs separately), (2) binary (containing either both AgNPs and TiO2NPs or one of the NPs and elements/nutrients) and (3) multi-components (conducted in real water samples collected from a tropical reservoir). In addition to the uptake of NPs, mortality, hatchability and heart rates of zebrafish embryos were also measured as part of these experiments. Results showed that AgNPs were taken up by the embryos to a larger extent as compared to TiO2NPs. Moreover, AgNPs were more toxic to zebrafish embryos as compared to TiO2NPs. In the presence of elements (5 μg mL−1) and nutrients (5 and 10 μg mL−1) together with one of the two NPs (10 μg mL−1), both an increase and a decrease in the uptake of NPs were observed in embryos. Results from this exploratory study show that in the presence of environmental contaminants, the uptake of these NPs can be affected significantly. Furthermore, the toxic effects of NPs depend not only on their relative environmental concentrations, but also on those of other environmental pollutants.