CeO$_{2}$ nanoparticles as free radical regulators in biological systems

Cerium dioxide nanoparticles possess unique physical and chemical properties, among which the enzyme-like activity is of particular interest. In particular, they are able to perform the functions of pro- and antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and peroxidase. Due to the advantages associated with pH and temperature stability and low cost, CeO$_{2}$ nanoparticles can be considered as promising mimetics of these enzymes. In this paper, the antioxidant activity of a citrate-stabilized colloidal suspension of CeO$_{2}$ nanoparticles has been studied using chemiluminometry in model systems generating superoxide anion radical and hydrogen peroxide. In the lucigenin/xanthine/xanthine oxidase system, generating a superoxide anion radical, CeO$_{2}$ nanoparticles exhibit antioxidant properties increasing upon conjugation with SOD. When interacting with hydrogen peroxide, CeO$_{2}$ nanoparticles exhibit peroxidase-like activity. In the combined ROS generating system, lucigenin/Co(II)/H$_{2}$O$_{2}$, CeO$_{2}$ nanoparticles demonstrated prooxidant activity.