Peroxidase-like Activity of CeO2 Nanozymes: Particle Size and Chemical Environment Matter

Abstract

The enzyme-like activity of metal oxide nanoparticles is governed by a number of factors, including their size, shape, surface chemistry and substrate affinity. For CeO2 nanoparticles, one of the most prominent inorganic nanozymes that have diverse enzymatic activities, the size effect remains poorly understood. The low-temperature hydrothermal treatment of ceric ammonium nitrate aqueous solutions made it possible to obtain CeO2 aqueous sols with different particle sizes (2.5, 2.8, 3.9 and 5.1 nm). The peroxidase-like activity of ceria nanoparticles was assessed using the chemiluminescent method in different biologically relevant buffer solutions with an identical pH value (phosphate buffer and Tris-HCl buffer, pH of 7.4). In the phosphate buffer, doubling CeO2 nanoparticles’ size resulted in a two-fold increase in their peroxidase-like activity. The opposite effect was observed for the enzymatic activity of CeO2 nanoparticles in the phosphate-free Tris-HCl buffer. The possible reasons for the differences in CeO2 enzyme-like activity are discussed.

Biocompatible ligands modulate nanozyme activity of CeO2nanoparticles

“…At the same time, the other important factors would also govern the biochemical properties of ceria-based nanozymes, including CeO 2 particle size and shape, surface hydroxylation and protonation, ligand-to-NPs ratio; the ionic strength and pH of the medium. 22,42,43,53,107,126 The analysis of these factors is therefore a multiparametric task that is crucial for the practical applications of nanozymes.…”

“…CeO 2 nanoparticles (CeO 2 NPs) are a very special enzyme mimic (nanozyme) exhibiting multiple enzyme-like catalytic properties. 5–10 Nowadays CeO 2 NPs were reported to exhibit superoxide dismutase (SOD)-, 11–16 catalase-, 17–19 peroxidase-, 20–23 oxidase-, 24–26 phosphatase-, 27 photolyase-, 28 phospholipase-, 29 nuclease-, 30 haloperoxidase-, 31 lipo- and phospholipoperoxidase-like 32 activities. This series can be supplemented with a relatively recently discovered uricase-like activity of cerium-containing mixed valence state metal organic frameworks.…”

“…34,35 An important factor which governs the functional characteristics of cerium-based biomaterials is the size of the CeO 2 NPs. The size effect has been traced in the catalytic 36,37 and photocatalytic 38,39 properties of ceria nanoparticles as well as in their enzyme-like activity including peroxidase-, 22 SOD-, 13 catalase-like 13 properties and antioxidant activity. 40,41 Another important factor in the chemistry of metal oxide nanoparticles, including CeO 2 NPs is the acidity (pH) of the medium.…”

Optimizing the Composition of the Substrate Enhances the Performance of Peroxidase-like Nanozymes in Colorimetric Assays: A Case Study of Prussian Blue and 3,3′-Diaminobenzidine

“…Usually, authors use substrates from commercial kits specifically designed for HRP. However, there is a growing body of evidence indicating that not only the pH but also the composition of substrate solutions can affect the oxidoreductase-like activity of nanozymes [21][22][23][24]. Moreover, the effect of the buffer varies among different chromogenic substrates [25].…”

Antimicrobial Activity of Citrate-Coated Cerium Oxide Nanoparticles

“…It is difficult to unambiguously identify the reason for such fundamental discrepancies. It is highly probable that this is due to the methods of obtaining the nanoparticles and therefore to the resulting nanoparticles differing in physical and chemical properties, size, the structure of the particles and their chemical composition, environmental conditions, and surroundings [ 56 , 57 , 58 , 59 , 60 ]. This creates additional difficulties in the comparative analysis of the results of studies conducted by different authors, even if they have ostensibly used the same chemical substance.…”