Toxicity, uptake, and accumulation of nano and bulk cerium oxide particles in Artemia salina

Although the toxicological impact of metal oxide nanoparticles has been studied for the last few decades on aquatic organisms, the exact mechanism of action is still unclear. The fate, behavior, and biological activity of nanoparticles are dependent on physicochemical factors like size, shape, surface area, and stability in the medium. This study deals with the effect of nano and bulk CeO2 particles on marine microcrustacean, Artemia salina. The primary size was found to be 15 ± 3.5 and 582 ± 50 nm for nano and bulk CeO2 (TEM), respectively. The colloidal stability and sedimentation assays showed rapid aggregation of bulk particles in seawater. Both the sizes of CeO2 particles inhibited the hatching rate of brine shrimp cyst. Nano CeO2 was found to be more toxic to A. salina (48 h LC50 38.0 mg/L) when compared to bulk CeO2 (48 h LC50 92.2 mg/L). Nano CeO2-treated A. salina showed higher oxidative stress (ROS) than those treated with the bulk form. The reduction in the antioxidant activity indicated an increase in oxidative stress in the cells. Higher acetylcholinesterase activity (AChE) was observed upon exposure to nano and bulk CeO2 particles. The uptake and accumulation of CeO2 particles were increased with respect to the concentration and particle size. Thus, the above results revealed that nano CeO2 was more lethal to A. salina as compared to bulk particles.