Influence of abiotic factors on developmental and cardiovascular toxicity of metal nanoparticles in zebrafish embryo

Rapid advances in nanotechnology have consequently increased the volume of nano wastes, and their potential release into aquatic environments pose significant threats to aquatic organisms. Therefore, corresponding health and safety of engineered nanoparticles (NP) requires further assessment. Several toxicity studies have documented the adverse effects of heavy metal NPs to fish, however, most studies have been conducted under pristine laboratory conditions where the influence of abiotic factors that could alter the behavior and toxicity of NP were not considered. This study investigated the developmental and cardiovascular toxicity of two PVP coated AgNPs of different sizes (50nm and 5nm) and uncoated CuONPs on zebrafish embryos with increasing NP concentrations alone as well as the combined effect in the presence of abiotic factors including HA and artificial sunlight. A dose-dependent decrease in hatch rate, survival, heart rate and increased deformity rate was found in zebrafish embryos treated with both AgNPs, with the smaller 5nm AgNP exerting toxicity at a higher extent. In contrast, CuONP completely inhibited embryos from hatching without noticeable differences with increasing concentrations. The two abiotic factors were found to induce different effects on the toxicity of NPs to the zebrafish embryos. The presence of HA consistently mitigated the toxicity of all three NPs to the zebrafish, however, UV irradiation was found to enhance the toxicity of both AgNPs, and slightly decreased that of CuO NPs. These results suggest the effect of the abiotic factors (HA and UV) were NP-specific. Overall, the results of this study clearly demonstrated the dynamic influences of abiotic factors, which may be a result of dynamic and complex transformation behavior of the NPs that could not be explained by size and surface charge alone. Therefore, this study highlighted the importance of abiotic factors for environmental realistic toxicity assessment of emerging contaminants, such as metal NPs, in the future.