Peroxidase‐Like Activity of Cupric Oxide Nanoparticle

Abstract

Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. Besides their fundamental importance, natural enzymes also have significant practical applications in medicine, chemical industry, food processing, and agriculture due to their excellent properties, such as high substrate specificities and high efficiency under mild conditions. However, natural enzymes also bear some serious disadvantages to limit their practical applications. In general, natural enzymes, which are globular proteins, can be digested by proteases. Like all proteins, the secondary, tertiary, and quaternary levels of enzyme structure are maintained by weak, noncovalent forces and can be easily disrupted by environmental changes, such as heating or chemical denaturants, which leading to the loss of their catalytic activity. Furthermore, preparation, purification, and storage of natural enzymes are usually time-consuming and expensive.

TiO2@CeOx Core–Shell Nanoparticles as Artificial Enzymes with Peroxidase-Like Activity

“…In general, nanozymes require a higher peroxide concentration than HRP to reach the maximum activity. 34,35,38 Interestingly, our core-shell NPs escape this trend.…”

“…As a matter of fact, if H 2 O 2 is tested as a substrate, by changing its concentration in the presence of 0.2 mM TMB the TC1 K M app value increases by about 20 times and its calculated value (6.29 mM) is higher than that measured for HRP, 34 however order of magnitude smaller than other oxides (CuO 85.6 mM, Fe 3 O 4 154 mM, see Table 1) 34,35 and comparable with other highly efficient mimics (graphene oxide 3.99 mM, FeS 7.2 mM). 36,38 Surprisingly, also TC3 shows an increase of the K M app (1.39 mM), but quite modest, smaller than the natural enzyme.…”

“…The results (double reciprocal plots) are shown in Figure S4 Table 1), but lower with respect to HRP (0.43 mM), 34 denoting a good affinity for TMB, which is a common feature of all inorganic mimics of peroxidase, such as Fe 3 O 4 , 34 CuO, 35 and FeS. 36,37 On the contrary, the affinity towards the oxidant is much scarcer.…”

“…This result is of paramount importance since the main limit of inorganic mimics is their need for high concentration of H 2 O 2 in order to work efficiently, which prevents their application in sensitive environments. 34,35 To rationalize the differences observed in the catalytic activity, we acquired the Ce 3d photoemission lines after the reaction of the TC samples with a 0.058 M solution of H 2 O 2 (i.…”

High-efficiency catalytic degradation of phenol based on the peroxidase-like activity of cupric oxide nanoparticles

“…Being inspired by the application of peroxidase, various nanomimetics, such as Fe 3 O 4 nanoparticles (Zhang et al 2008(Zhang et al , 2009), gold nanoparticles (Han et al 2008), iron oxide-based nanoparticles (Zelmanov and Semiat 2008), and c-FeOOH nanosheets (Peng et al 2011), have been used as catalysts for the catalytic oxidation of phenol. In the previous study, we have found that cupric oxide nanoparticle is a highly effective catalyst to peroxidase substrates, and the binding affinity for the substrate 3,3',5,5'-tetramethylbenzidine (TMB) is higher than that of HRP and other peroxidase nanomimics (Chen et al 2011). Based on this finding, we studied in this work the potential application of cupric oxide nanoparticles in phenol removal.…”