The interaction of phosphate species with cerium oxide: The known, the ambiguous and the unexplained.

Cerium oxide based nanozymes are intensively studied due to their catalytic activity and structural flexibility. Such nanozymes have a great future potential in human therapeutics and antimicrobial activity. The structural complexity of their surfaces enables a great variety of enzyme mimetic activities. However, selection of a specific activity remains challenging, as such activities are sensitive to morphological and compositional changes as well as the physicochemical and biological environments. When delivered into biological systems, many processes occur at the surface, redefining the biological identity and activity of the nanozyme. Inorganic phosphates and phosphate-bearing molecules are some critical examples of items that can interact with cerium oxide nanozymes. Inorganic phosphates can interact directly with cerium oxide and even have a scavenging activity converting the material into cerium phosphate. Phosphate-bearing molecules can absorb on the surface of the nanozyme where phosphatase activity may occur. Given the abundance of phosphates in biological environments, cerium oxide nanozymes are strongly affected by their local concentration. Here, we discuss the interaction of cerium oxide with phosphates and phosphate-bearing molecules, providing a focussed review of the computational and experimental literature, with a focus on the surface morphology and chemistry of the nanozyme and their impact on the phosphate adsorption and phosphatase activity.