Toxicity of CeO sub(2) nanoparticles - The effect of nanoparticle properties

Conflicting reports on the toxicity of CeO sub(2) nanomaterials have been published in recent years, with some studies finding CeO sub(2) nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO sub(2) from three different suppliers as well as CeO sub(2) synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO sub(2) nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO sub(2) nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results.