Cerium oxide nanoparticle: a remarkably versatile rare earth nanomaterial for biological applications

Cerium oxide nanoparticles (CeONPs) have received much attention because of their excellent catalytic activities, which are derived from quick and expedient mutation of the oxidation state between Ce4+ and Ce3+. The cerium atom has the ability to easily and drastically adjust its electronic configuration to best fit its immediate environment. It also exhibits oxygen vacancies, or defects, in the lattice structure; these arise through loss of oxygen and/or its electrons, alternating between CeO2 and CeO2−x during redox reactions. Being a mature engineered nanoparticle with various industrial applications, CeONP was recently found to have multi-enzyme, including superoxide oxidase, catalase and oxidase, mimetic properties that produce various biological effects, such as being potentially antioxidant towards almost all noxious intracellular reactive oxygen species. CeONP has emerged as a fascinating and lucrative material in biological fields such as bioanalysis, biomedicine, drug delivery, and bioscaffolding. This review provides a comprehensive introduction to CeONP’s catalytic mechanisms, multi-enzyme-like activities, and potential applications in biological fields. Cerium oxide nanoparticles have the unique power to act as both oxidation and reduction catalysts, thanks to the ability of cerium to rapidly switch between two oxidation states. Can Xu and Xiaogang Qu from the Chinese Academy of Sciences review how this dual catalytic activity yields enzyme-like behavior that can be harnessed for cancer-detecting assays and new biomedical applications. The nanoparticles mimic enzyme species, such as superoxide dismutases and catalases, that repair the damage caused by free radicals and reduce harmful reactive oxygen levels in the body. With tiny dimensions that allow them to enter cellular spaces inaccessible to traditional medicines - including crossing the blood-brain barrier for Alzheimer's disease treatments - these nanomaterials may offer potent remedies against degenerative diseases. Xu and Qu stress the need for systematic biological testing, however, to resolve possible toxicity concerns. Cerium oxide nanoparticles (CeONPs) have attracted much attention because they possess multi-enzyme mimetic properties and have been used in bioanalysis, biomedicine, drug delivery, bioscaffold and so on. This review summarizes recent achievements on CeONPs catalytic mechanisms, the multi-enzyme-like activity, and their biomedical applications, such as in treatment of cancer, diabetes and Alzheimer’s disease.