Photolyase-Like Catalytic Behavior of CeO 2

Guo

et al. 2020

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effect), a lower pH value, as well as a high level of oxidative stress. [4-9] Especially, the overproduction of reactive oxygen species (ROS) induces a serious oxidative stress, which is strongly implicated to various tumors. [8,9] In addition, a high ROS level is also considered to be an endpoint of the alteration of several important metabolic pathways in tumors. [8-11] Thus, modulation of the intratumor ROS level, either by scavenging ROS or increasing ROS, is a promising approach to anticancer therapy and ROS-related biomedical fields. [10-19] Recently, nanomaterial-enabled biocatalytic chemodynamic therapy has been demonstrated as a promising method for therapeutic intervention in a variety of tumors. [11-16,20] Through this biocatalytic tumor therapy, intratumor H 2 O 2 can be converted into toxic hydroxyl radicals (• OH) with the help of catalysts that can then induce tumor cell apoptosis and death through oxidative damage to various biomacromolecules, including DNA, lipids, and proteins. Nevertheless, the relatively deficient intratumoral H 2 O 2 level significantly lowers the biocatalytic therapeutic efficiency. [21-27] Thus, the focus has been on increasing the intratumoral H 2 O 2 level through oxidization of intratumoral molecules Catalytic generation of reactive oxygen species has been developed as a promising methodology for tumor therapy. Direct O 2 •− production from intratumor oxygen exhibits exceptional tumor therapeutic efficacy. Herein, this therapy strategy is demonstrated by a pH-responsive hybrid of porous CeO 2 nanorods and sodium polystyrene sulfonate that delivers high oxidative activity for O 2 •− generation within acidic tumor microenvironments for chemodynamic therapy and only limited oxidative activity in neutral media to limit damage to healthy organs. The hydrated polymer-nanorod hybrids with large hydrodynamic diameters form nanoreactors that locally trap oxygen and biological substrates inside and improve the charge transfer between the catalysts and substrates in the tumor microenvironment, leading to enhanced catalytic O 2 •− production and consequent oxidation. Together with successful in vitro and in vivo experiments, these data show that the use of hybrids provides a compelling opportunity for the delivery selective chemodynamic tumor therapy.

Section: Resultsmentioning

confidence: 99%

Section: (5 Of 11)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A pH‐Responsive Polymer‐CeO₂ Hybrid to Catalytically Generate Oxidative Stress for Tumor Therapy

Tian

Guo

et al. 2020

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“…Nanozymes refer to nanoparticle‐based enzyme mimics, and they have attracted extensive interest recently due to their low cost, high stability and versatile catalytic activities . Nanoceria is an interesting and important nanozyme, and it has been studied mainly for its redox activity to mimic oxidase, peroxidase, catalase, and superoxide dismutase (SOD) .…”

Section: Introductionmentioning

confidence: 99%

Self‐limited Phosphatase‐mimicking CeO₂ Nanozymes

2020

ChemNanoMat

CeO2 nanoparticles or nanoceria is a very interesting enzyme mimic (nanozyme) with a diverse range of catalytic activities. Most of the previous studies focused on its redox chemistry for mimicking oxidase, peroxidase, and catalase‐like activities, and as a scavenger of reactive oxygen species. Considering CeO2 has both Ce(III) and Ce(IV) species and both interact strongly with inorganic phosphate, nanoceria has also been studied for its phosphatase‐like activity. We herein compared these species along with alkaline phosphatase (ALP). First, CeO2 and Ce(IV) have good activity using p‐nitrophenylphosphate (p‐NPP) as a substrate, while other metal ions failed to show this activity. Since a reaction product is inorganic phosphate and we observed an interesting enzyme kinetic profile, the effect of phosphate was studied, which inhibited both CeO2 and ALP. The inhibition constant was about 5‐fold smaller for CeO2. The inhibition effect of polyphosphates was even stronger. Due to the product inhibition effect, CeO2 is unlikely to be a typical multiple turnover nanozyme, and the system is self‐limited. For the other anions, only F− showed a moderate inhibition effect on the cerium species, while adsorption of DNA did not inhibit the activity. Finally, heat treated ALP lost the activity, but CeO2 and Ce(IV) remained active. This study has deepened our understanding of CeO2 as a phosphatase mimicking nanozyme, which could be useful for biosensing and chemical biology applications.

“…To date, nanozymes have been reported to mimic oxidase, peroxidase, catalase, superoxide dismutase, alkaline phosphatase, and nuclease. [ 4–8 ] Nanozymes have been widely used for analytical applications [ 9–15 ] such as replacing horseradish peroxidase (HRP) for signal amplification in immunoassays. In addition, some molecules can regulate the activity of nanozymes and therefore are classified as promotors or inhibitors.…”

Section: Introductionmentioning

confidence: 99%

Nanozyme‐based luminescence detection

Zhang

2020

Luminescence

Nanozymes refer to nanomaterial‐based enzyme mimics. Most nanozyme assays use chromogenic molecules as substrates that can produce an absorbance change in the visible region upon reaction. For certain applications, such as imaging, fluorescence and luminescence signals are required. Fluorescence detection is also advantageous for sensor development due to its low background signal and high sensitivity. A few substrates, such as Amplex Red and luminol, allow luminescence generation with many oxidative nanozymes. In addition, these substrates can work at neutral pH, useful for intracellular applications. In this review, we summarize luminescence signalling‐based nanozyme systems. We begin with the properties of commonly used substrates. A few specific nanozymes are highlighted, including metal nanoparticles, metal oxide nanomaterials, carbon‐based nanomaterials, and metal–organic frameworks. Finally, a few future research opportunities are discussed.