LAUSR

Abstract 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 CeO 2 nanoparticles (3 nm) in biochemical models. The trolox (a water-soluble analogue of vitamin E) equivalent antioxidant capacity of a 1 µmol/L CeO 2 sol was 0.049 ± 0.004 µmol/L; thus, the ability of CeO 2 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 СеО 2 in SOD activity units was 2.00 ± 0.03 nmol/L. Thus, the activity of CeO 2 as a SOD mimetic is about six orders of magnitude lower than the activity of the native enzyme.