Prooxidant potential of СеО$_2$ nanoparticles towards hydrogen peroxide

The multifaceted enzyme-like activity of CeO$_{2}$ nanoparticles (CeNPs) expands the prospects for their potential biomedical applications. In this regard, there is a need for a comprehensive analysis of the redox behavior of CeO$_{2}$ nanoparticles in relation to key molecules of free radical homeostasis. Here, the prooxidant potential of CeNPs towards H$_{2}$O$_{2}$ was investigated to elucidate both prooxidant capacity and prooxidant activity of CeNPs. To describe the kinetics in the luminol-H$_{2}$O$_{2}$ system at pH 8.5 upon the addition of citrate-stabilized CeO$_{2}$ sol (3 nm), a numerical model of three reactions is proposed. The rate constants being a measure of prooxidant activity, were k$_{1}$ = 9.0 $\cdot$10$^{4}$ $\mu$M$^{-1}$min$^{-1}$, k$_{2}$ = 2.0 $\cdot$ 10$^{6}$ $\mu$M$^{-1}$min$^{-1}$, k$_{3}$ = 2.9 $\cdot$10$^{5}$ $\mu$M$^{-1}$min$^{-1}$. The functionalization of CeO$_{2}$ nanoparticles surface with ammonium citrate increases their prooxidant capacity by two-fold, while modification with maltodextrin decreases it by six-fold. It was shown that the prooxidant capacity of citrate-stabilized CeO$_{2}$ sol in Tris-HCl is approximately four-fold higher than in phosphate buffer solution at pH 7.4.