Cerium-zirconium oxide nanocatalysts as free radical scavengers for biomedical applications

Administering CeO2 nanoparticles into cell cultures was found to improve cell culture's viability both in vitro and in vivo. In this dissertation, an in vitro study conducted in our laboratory has observed the reduction of endogenous free radical concentration in CeO2 treated cell cultures. Furthermore, it is found that CeO2 nanoparticles scavenge free radicals through catalysis. Based on the findings, a series of CeO2-based nanocrystallites of greater catalytic activities was developed, aiming to achieve the same therapeutic efficacy to cell cultures with lower nanoparticle doses.;In this dissertation, zirconium-doped CeO2 (Ce xZr1-xO2) nanoparticles were synthesized and characterized. Their free radical scavenging activities were tested against harmful endogenous oxygen species, including hydrogen peroxide and superoxide radicals. It is found that the scavenging activity of CexZr 1-xO2 nanoparticles was promoted up to four times when scavenging hydrogen peroxide. The scavenging activity of Ce xZr1-xO2 nanoparticles was promoted up to nine times when scavenging superoxide radicals. Importantly, their free radical scavenging activities to hydrogen peroxide correlate to the reported oxygen vacancy concentrations in the same materials. Their free radical scavenging activities to superoxide radicals correlate to the reported reducibility in the same materials. The results suggest that oxygen vacancies, lattice oxygen, electrons, and holes are involved in free radical scavenging.;In addition, it is found that CexZr1-xO 2 nanoparticles regulate antioxidant protein's redox states upon catalysis. This might be a distinct antioxidant defense pathway that reactivates antioxidant protein's function, and to explain the superior protection of CeO2 nanoparticles.