Abstract
Nanomaterials with enzyme-like activity have been the spotlight of scientific and technological efforts to substitute natural enzymes, not only in biological research but also for industrial manufacturing, medicine, and environment healing. Notable advancements in this field along the last years relied on to the rational design of single-atom active sites, knowledge of the underlying atomic structure, and realistic ab initio theoretical models of the electronic configuration at the active site. Thus, it is plausible that a next generation of nanozymes still to come will show even improved catalytic efficiency and substrate specificity. However, the dynamic nature of the protein cage surrounding most active sites in biological enzymes adds a flexible functionality that possess a challenge for nanozyme's mimicking of their natural counterparts. We offer a perspective about where the main strategies to improve nanozymes are headed and identify some of the big challenges faced along the road to better performance. We also outline some of the most exciting bio-inspired ideas that could potentially change this field.
Highlights
The concept of artificial enzyme was introduced in the 1970s, after the first observation of increased deacetylation reaction rates up to 107 times by of metal groups.[4]
We offer a perspective about where the main strategies to improve nanozymes are headed and identify some of the big challenges faced along the road to better performance
This reaction is still been investigated a century after Fenton’s first observation,[16] some of the basic, undisputed facts of the Fe2+/H2O2 system (i.e., Fenton reaction) can be summarized as follows: (a) when Fe2+ ions are in excess over H2O2, quantitative oxidation of Fe2+ by H2O2 occurs; (b) in the opposite situation, when the peroxide is in excess over Fe2+, a catalytic decomposition of the H2O2 takes place through 2 H2O2 ! 2 H2O þ O2 concurrently with the iron oxidation; (c) Fenton’s oxidation process involves the formation of hydroxyl from hydrogen peroxide with a catalytic redox cycling metal.[17,18]
Summary
Natural enzymes are those biomolecules that regulate the rates of biochemical reactions in living organisms, as an essential part of cell metabolic pathways. The concept of artificial enzyme was introduced in the 1970s, after the first observation of increased deacetylation reaction rates up to 107 times by of metal groups.[4] This observation was followed by countless reports on enzyme-like activities involving inorganic materials[5,6] and the term “nanozyme” was coined to identify them as a synthetic counterpart of natural enzymes.[7] With the irruption of nanotechnology, nanomaterials were confirmed to mimic several biological enzymes as a standalone inorganic system, with the pivotal report by Gao et al showing the peroxidase-like activity of Fe3O4 nanoparticles.[8] Since multiple enzymatic-like activities have been reported including peroxidase,[9] catalase,[10] superoxide dismutase,[11] and phosphatase.[12] some authors have questioned the very concept of nanozyme, arguing the fundamental differences between enzymatic activity and oxidation chemistry, as distinct mechanisms behind the observed formation of hydroxyl radical (OH) and related to a Fenton reaction process.[13,14] According to these authors, the two-electron oxidation expected for a peroxidase catalytic reaction does not occur on most of the “peroxidase-like nanozyme” reactions involving transition-metal oxide nanoparticles like Fe3O4. PrOx, SOx, Ox, Cat SOD, Cat PrOx, SOx, Ox, Cat SOx, GOx, Lac, Ox, Cat PrOx, SOD, Ox, Cat PrOx, Ox, Cat PrOx, Ox, Cat PrOx, Ox, Cat PrOx, Ox, Cat PrOx, Ox, Cat PrOx, SOD, GSHPx, PrOx, SOD, GSHOx, Cat SOD, Ox, Cat, PhEs, Nuc SOD, Ox, Cat
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