Self‐limited Phosphatase‐mimicking CeO2 Nanozymes

Abstract CeO 2 nanoparticles or nanoceria is a very interesting enzyme mimic (nanozyme) with a diverse range of catalytic activities. Most of the previous studies focused on its redox chemistry for mimicking oxidase, peroxidase, and catalase‐like activities, and as a scavenger of reactive oxygen species. Considering CeO 2 has both Ce(III) and Ce(IV) species and both interact strongly with inorganic phosphate, nanoceria has also been studied for its phosphatase‐like activity. We herein compared these species along with alkaline phosphatase (ALP). First, CeO 2 and Ce(IV) have good activity using p‐nitrophenylphosphate (p‐NPP) as a substrate, while other metal ions failed to show this activity. Since a reaction product is inorganic phosphate and we observed an interesting enzyme kinetic profile, the effect of phosphate was studied, which inhibited both CeO 2 and ALP. The inhibition constant was about 5‐fold smaller for CeO 2 . The inhibition effect of polyphosphates was even stronger. Due to the product inhibition effect, CeO 2 is unlikely to be a typical multiple turnover nanozyme, and the system is self‐limited. For the other anions, only F − showed a moderate inhibition effect on the cerium species, while adsorption of DNA did not inhibit the activity. Finally, heat treated ALP lost the activity, but CeO 2 and Ce(IV) remained active. This study has deepened our understanding of CeO 2 as a phosphatase mimicking nanozyme, which could be useful for biosensing and chemical biology applications.