title: A phosphate-dependent shift in redox state of cerium oxide nanoparticles and its effects on catalytic properties.
abstract: Cerium oxide nanoparticles (CeNPs) have shown promise as catalytic antioxidants in cell culture and animal models as both superoxide dismutase and catalase mimetics. The reactivity of the cerium (Ce) atoms at the surface of its oxide particle is critical to such therapeutic properties, yet little is known about the potential for a protein or small molecule corona to form on these materials in vivo. Moreover Ce atoms in these active sites have the potential to interact with small molecule anions, peptides, or sugars when administered in culture or animal models. Several nanomaterials have been shown to alter or aggregate under these conditions, rendering them less useful for biomedical applications. In this work we have studied the change in catalytic properties of CeNPs when exposed to various biologically relevant conditions in vitro. We have found that CeNPs are resistant to broad changes in pH and also not altered by incubation in cell culture medium. However to our surprise phosphate anions significantly altered the characteristics of these nanomaterials and shifted the catalytic behavior due to the binding of phosphate anions to cerium. Given the abundance of phosphate in biological systems in an inorganic form, it is likely that the action of CeNPs as a catalyst may be strongly influenced by the local concentration of phosphate in the cells and/or tissues in which it has been introduced.
authors.affiliation: Burnett School of Biomedical Science, College of Medicine, University of Central Florida, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Singh
authors.forename: Talib
authors.initials: T
authors.lastname: Dosani
authors.forename: Ajay S
authors.initials: AS
authors.lastname: Karakoti
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.forename: Sudipta
authors.initials: S
authors.lastname: Seal
authors.forename: William T
authors.initials: WT
authors.lastname: Self
mesh_terms: D000818:Animals; D000838:Anions / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism; D002254:Carbonates / Q000737:chemistry; D002374:Catalase / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D002563:Cerium / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D013482:Superoxide Dismutase / Q000737:chemistry / Q000378:metabolism
chemical_list: D000838:Anions; D000975:Antioxidants; D001672:Biocompatible Materials; D002254:Carbonates; D010710:Phosphates; D013431:Sulfates; D002563:Cerium; C030583:ceric oxide; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase