  Research on cerium oxide nanoparticles (nanoceria) has captivated the
scientific community due to their unique physical and chemical properties, such
as redox activity and oxygen buffering capacity, which made them available for
many technical applications, including biomedical applications. The redox
mimetic antioxidant properties of nanoceria have been effective in the
treatment of many diseases caused by reactive oxygen species (ROS) and reactive
nitrogen species. The mechanism of ROS scavenging activity of nanoceria is
still elusive, and its redox activity is controversial due to mixed reports in
the literature showing pro-oxidant and antioxidant activity. In lieu of its
current research interest, it is critical to understand the behaviour of
nanoceria in the biological environment and provide answers to some of the
critical and open issues. This review critically analyses the status of
research on the application of nanoceria to treat diseases caused by ROS. It
reviews the proposed mechanism of action and shows the effect of surface
coatings on its redox activity. It also discusses some of the crucial issues in
deciphering the mechanism and redox activity of nanoceria and suggests areas of
future research.
