The Vital Role of Buffer Anions in the Antioxidant Activity of CeO2 Nanoparticles

Cerium oxide (CeO₂) nanoparticles display excellent antioxidant properties by scavenging free radicals. However, some studies have indicated that they can cause an adverse response by generating reactive oxygen species (ROS). Hence, it is important to clarify the factors that affect the oxidant/antioxidant activities of CeO₂ nanoparticles. In this work, we report the effects of different buffer anions on the antioxidant activity of CeO₂ nanoparticles. Considering the main anions present in the body, Tris‐HCl, sulfate, and phosphate buffer solutions have been used to evaluate the antioxidant activity of CeO₂ nanoparticles by studying their DNA protective effect. The results show that CeO₂ nanoparticles can protect DNA from damage in Tris‐HCl and sulfate systems, but not in phosphate buffer solution (PBS) systems. The mechanism of action has been explored: cerium phosphate is formed on the surface of the nanoparticles, which interferes with the redox cycling between Ce³⁺ and Ce⁴⁺. As a result, the antioxidant activity of CeO₂ nanoparticles is greatly affected by the external environment, especially the anions. These results may provide guidance for the further practical application of CeO₂ nanoparticles.