Promotion and Inhibition of the Oxidase-Mimicking Activity of Nanoceria by Phosphate, Polyphosphate, and DNA.

Nanoceria (CeO2 nanoparticles) is an extensively studied nanozyme with interesting oxidase-mimicking activity. As they can work in the absence of toxic and unstable H2 O2 , CeO2 nanoparticles have been widely used in biosensing. CeO2 nanoparticles often encounter phosphate-containing molecules that can affect their catalytic activity, and various reports exist in the literature showing both promoted and inhibited activity. In this work, we systematically studied five types of phosphate: orthophosphate, pyrophosphate, triphosphate, trimetaphosphate, and a polyphosphate with 25 phosphate units (Pi25 ). In addition, DNA oligonucleotides of various length and sequence. DNA was included as they contain a phosphate backbone that can strongly adsorb on nanoceria. We observed that a high concentration of DNA in acetate buffer inhibited activity, whereas a low concentration of DNA in phosphate buffer increased activity. The change of activity was also related to the type of substrate and related to the aggregation of CeO2 . These discoveries provide an important understanding for the further use of CeO2 nanoparticles in biosensor development, materials science, and nanotechnology.