Quantification of Free Radical Scavenging Properties and SOD-Like Activity of Cerium Dioxide Nanoparticles in Biochemical Models

The enhanced chemiluminescence method in combination with mathematical modeling has been used to quantify the antioxidant properties and to study the superoxide dismutase-like (SOD-like) activity of a citrate-stabilized colloid solution of ultrasmall CeO2 nanoparticles (3 nm) in biochemical models. The trolox (a water-soluble analogue of vitamin E) equivalent antioxidant capacity of a 1 mu mol/L CeO2 sol was 0.049 +/- 0.004 mu mol/L; thus, the ability of CeO2 to act as a free radical scavenger is about 20 times lower than that of trolox. The antioxidant activity was estimated by the mathematical modeling method. The free radical scavenging rate constants were 2000 nM(-1) min(-1) for trolox and k(1) = 300 nM(-1) min(-1) and k(2) = 4 nM(-1) min(-1) for cerium dioxide. The SOD-like activity of 1 mmol/L CeO2 in SOD activity units was 2.00 +/- 0.03 nmol/L. Thus, the activity of CeO2 as a SOD mimetic is about six orders of magnitude lower than the activity of the native enzyme.