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

Nanoceria (CeO 2 NPs) is an extensively studied nanozyme with interesting oxidase-mimicking activity. Since it can work in the absence of toxic and unstable H 2 O 2 , CeO 2 NPs has been widely used in biosensing. CeO 2 NPs often encounters phosphate containing molecules that may affect its catalytic activity and various reports exist in the literature showing both promoted and inhibited activity. In this work, we systematically studied five types of phosphates including orthophosphate, pyrophosphate, triphosphate, a polyphosphate with 25 phosphate units (Pi 25 ), and also DNA oligonucleotides of various lengths and sequences. DNA was included since they contain a phosphate backbone that can strongly adsorb on nanoceria. We observed inhibited activity by a high concentration of DNA in both acetate and phosphate buffer, however, we only observed obvious increase activity by relatively low concentration of DNA in phosphate buffer. These discoveries provide an important understanding for further use of CeO 2 NPs in biosensor development, materials science, and nanotechnology.