In vivo toxicity evaluation of biologically synthesized silver nanoparticles and gold nanoparticles on adult zebrafish: a comparative study.

In this study, toxicity of biologically synthesized silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) was compared using zebrafish as a model organism. At 96 h, LC50 of AgNPs and AuNPs was found to be 24.5 µg/L and 41 mg/L, respectively. Following the LC50 determination, half of the LC50 of AgNPs (12.25 µg/L) and AuNPs (20.5 mg/L) was exposed to adult zebrafishes for 14 days. Morphological changes, liver marker enzymes, reactive oxygen species (ROS) generation, genotoxic effects and mRNA expression levels of oxidative stress and innate immune response related genes were studied using nanoparticle treated gill, liver and blood cells. In this study, AgNP-treated gill and liver tissues showed a number of morphological changes such as cell membrane damage, irregular cell outlines, pyknotic nuclei and complete disruption of gill and liver cells; on the contrary, AuNPs treated liver tissues alone showed such changes. The levels of liver marker enzymes such as alanine aminotransferase and aspartate aminotransferase were increased after AgNPs treatment when compared to AuNPs treatment. AgNP-treated liver cells showed higher levels of ROS generation than the control; on the other hand, AuNPs treatment exhibited lower levels of ROS generation than the control. Interestingly, AgNP-treated blood cells showed micronuclei formation and nuclear abnormalities, while AuNPs treatment did not show such effects. Based on these observations, it is clear that AgNPs may cause oxidative stress and immunotoxicity to adult zebrafish than the AuNPs. However, these results clearly reveal the significance of relatively safe and less toxic bionanomaterials for possible biomedical applications.