Enhanced Peroxidase Activity Research Articles

Enhancing peroxidase activity of NiCo2O4 nanoenzyme by Mn doping for catalysis of CRISPR/Cas13a-mediated non-coding RNA detection

CRISPR/Cas13a with precise and controllable programming of endonuclease activity has been served as powerful tool for RNA sensing. Although with high sensitivity, existing CRISPR/Cas13a-based biosensors need complex amplification procedure or special equipment that limited quantification capability. Here, Mn-doped NiCo2O4 (Mn/NiCo2O4) nanozyme with enhanced peroxidase activity was synthesized and combined with CRISPR/Cas13a-based reaction to develop a simple, sensitive and universal biosensor for RNA detection, which is achieved through target recognition that activates Cas enzymes to cleave RNA reporter for inhibiting Mn/NiCo2O4 nanozyme to assemble on microplate. The Mn/NiCo2O4 nanozyme assembled on microplate can be monitored through colorimetric and fluorometric approaches. On one hand, Mn/NiCo2O4 nanozyme offers ideal peroxidase activity to catalyze colorimetric reaction, and as low as dozens of amol level of RNA target can be sensitively detected by naked eyes without any amplification procedures. On the other hand, Mn/NiCo2O4 can be also served as a signal amplifier to produce large amount of Co2+, Mn2+and Ni2+ to quench the fluorescence of calcein. The fluorescent approach can achieve higher sensitivity (about 40-fold) than colorimetric method. More importantly, the proposed biosensor can work well for multiple RNA detection in real biological samples, showing a great potential for monitoring non-coding RNA-related diseases.

Bimetallic FeCo metal–organic framework based cascade reaction system: Enhanced peroxidase activity for antibacterial performance

Metal-organic frameworks (MOFs), as a peroxidase (POD), can catalyze the conversion of H2O2 to reactive oxygen species (ROS) for antibacterial application. To achieve strong antibacterial activity, it is necessary to improve the enzyme-like activity of MOFs. In this study, FexCoMOF was synthesized by incorporating Co(II) to improve the electron transfer of Fe(III)/Fe(II), which enhanced its redox capacity as a nanozyme and further promoted the generation of hydroxyl radical (⋅OH), exhibiting higher POD activity. Doping with different amounts of Co(II) altered the particle size, specific surface area, and surface defects of FexCoMOF, thus exhibiting differential enzyme-like activities. Additionally, a glucose-responsive enzyme cascade reaction system based on Fe4CoMOF/glucose oxidase (GOx) was established. In the presence of glucose, the in situ-generated substrate H2O2 was in contact with the catalytic site and the generated gluconic acid enabled Fe4CoMOF to maintain maximum enzyme activity under physiological pH conditions, avoiding damage caused by the use of exogenous high concentrations of H2O2. In the in vitro antibacterial experiment, the minimum inhibitory concentration (MIC) of Fe4CoMOF/GOx was 10 μg mL−1 for Escherichia coli (E. coli) and 5 μg mL−1 for Staphylococcus aureus (S. aureus) (∼108 CFU mL−1). The increase in enzyme activity resulted in a considerable reduction in the dose of the antibacterial agent, which was conducive to improving bio-safety. The in vivo experiment in mice demonstrated that the glucose-responsive Fe4CoMOF-based cascade reaction system had excellent antibacterial properties and remarkably promoted wound healing. The antibacterial agent based on bimetallic MOF developed in this work provides a new idea for cascade catalytic antibacterial therapy and will have remarkable application prospects in biomaterials and nanomedicine.

Enhanced enzyme-like DNAzyme@MOFs for non-enzymatic uric acid detection in interstitial fluid

The increased uric acid (UA) level is closely related to many diseases. However, the detection of UA remains great challenges due to the pain of blood testing and the complexity of common methods. Therefore, the detection of UA is of great significance for public health. In this paper, a new method for UA detection is proposed. The swellable hydrogel microneedles (hydrogel MNs) can be used for minimally invasive extraction of skin interstitial fluid (ISF). The colorimetric detection of trace UA in ISF can be successfully achieved by virtue of DNAzyme@MOFs with enhanced peroxidase activity. This study provides a powerful tool for minimally invasive, painless, rapid and convenient detection of UA in clinical applications. This study not only avoids the use of expensive and unstable natural enzymes but also expands the applications of DNAzyme@MOFs in biomedical detection.

Spraying glycine betaine on fresh pistachio fruits (Pistacia vera L.) for preservation in cold storage

Oxidative stress occurs during storage, often leading to a decrease in fruit quality and subsequently reducing its marketability. In this investigation, the ability of glycine betaine (GB) to extend the quality and storage of fresh pistachios stored in cold conditions was evaluated. The independent variables in this study were the concentration of GB (0, 5, 10 and 15 mM) and storage period (at harvest, 25, 50, and 75 days after harvest). Over time, the chlorophyll and carotenoid content of both kernels and hulls, as well as phenolics, flavonoids, antioxidant activity, taste, aroma, appearance of shells and hulls, firmness, and overall weight, tend to decrease. However, glycine betaine (GB) significantly prevents these reductions. GB effectively countered the rise in malondialdehyde, ion leakage, and hydrogen peroxide levels in kernels over time. In GB-treated samples, anthocyanin levels initially increased when comparing harvest time in both kernels and hulls, but subsequently decreased. GB enhanced peroxidase activity and suppressed polyphenol oxidase activity. However, contrary to expectation, GB reduces phenylalanine ammonia lyase activity. Overall, higher GB concentrations lead to a more pronounced effect. Based on the results, GB, particularly at a concentration of 15 mM, is recommended for preserving fresh pistachios during cold storage.

Enhancing Resistance to Cercospora Leaf Spot in Mung Bean (Vigna radiata L.) through Bradyrhizobium sp. DOA9 Priming: Molecular Insights and Bio-Priming Potential.

Mung bean (Vigna radiata L.), a vital legume in Asia with significant nutritional benefits, is highly susceptible to Cercospora leaf spot (CLS) caused by Cercospora canescens, leading to significant yield losses. As an alternative to chemical fungicides, bio-priming with rhizobacteria can enhance plant resistance. This study explores the potential of Bradyrhizobium sp. strain DOA9 to augment resistance in mung bean against CLS via root priming. The results reveal that short (3 days) and double (17 and 3 days) priming with DOA9 before fungal infection considerably reduces lesion size on infected leaves by activating defense-related genes, including Pti1, Pti6, EDS1, NDR1, PR-1, PR-2, Prx, and CHS, or by suppressing the inhibition of PR-5 and enhancing peroxidase (POD) activity in leaves. Interestingly, the Type 3 secretion system (T3SS) of DOA9 may play a role in establishing resistance in V. radiata CN72. These findings suggest that DOA9 primes V. radiata CN72's defense mechanisms, offering an effective bio-priming strategy to alleviate CLS. Hence, our insights propose the potential use of DOA9 as a bio-priming agent to manage CLS in V. radiata CN72, providing a sustainable alternative to chemical fungicide applications.

Functional analysis of maize GRAS transcription factor gene ZmGRAS72 in response to drought and salt stresses

Abiotic stresses, such as drought and salt, are major factors affecting plant growth, development, and productivity. The GRAS gene family is a class of transcriptional regulators in plants that influence plant responses to various biotic and abiotic stresses. In this study, we cloned the maize (Zea mays L.) GRAS gene ZmGRAS72 and preliminarily analyzed its biological function. ZmGRAS72 was highly expressed in maize stems and young leaves, and was induced by abiotic stress and phytohormone treatments. Transient expression assays of maize protoplasts showed that ZmGRAS72 was localized to the nucleus. Heterologous expression of ZmGRAS72 in A. thaliana significantly improved plant tolerance to drought and salt stresses, increased chlorophyll content, decreased malondialdehyde content, and enhanced peroxidase activity. In addition, heterologous expression of ZmGRAS72 in A. thaliana upregulated or downregulated the expression levels of abscisic acid biosynthesis genes (NCED3), signaling genes (ABI1, ABI2, ABI4, and ABI5), and stress-related genes (RD22, RD29A, and KIN1) under abiotic stress. These results indicate that ZmGRAS72 may be responsive to abiotic stress, which forms a basis for further research on the mechanisms underlying the action of ZmGRAS72 in maize.

Strategies for aflatoxins B1 and M1 degradation in milk: Enhancing peroxidase activity by physical treatments

This study aimed to evaluate the effect of physical treatments (ultrasound, microwave, ultraviolet light, and magnetic fields) on the activities of peroxidases from rice bran and soybean meal to degrade aflatoxins B1 and M1 in milk. The effects of physical treatments on peroxidase activities were evaluated. Peroxidases (0.015 U mL−1) were added to milk contaminated with aflatoxins B1 and M1 (5 ng mL−1) under refrigeration (4 °C, 24 h), and residual concentrations of mycotoxins were quantified. Physical treatments increased peroxidase activities from rice bran and soybean meal extracts. The most efficient treatment was ultraviolet light (365 nm, 45 min) applied to peroxidases extracted from rice bran; degradation increased by 16.7% and 10.6%, reaching 78.2% and 71.2% aflatoxins B1 and M1 in milk, respectively. Therefore, using low-cost peroxidase physically treated by ultraviolet light can be an alternative for the food indstry to mitigate aflatoxins B1 and M1 in milk.

Human cytochrome C natural variants: Studying the membrane binding properties of G41S and Y48H by fluorescence energy transfer and molecular dynamics

Cytochrome C (cyt C), the protein involved in oxidative phosphorylation, plays several other crucial roles necessary for both cell life and death. Studying natural variants of cyt C offers the possibility to better characterize the structure-to-function relationship that modulates the different activities of this protein. Naturally mutations in human cyt C (G41S and Y48H) occur in the protein central Ω-loop and cause thrombocytopenia 4. In this study, we have investigated the binding of such variants and of wild type (wt) cyt C to synthetic cardiolipin-containing vesicles. The mutants have a lower propensity in membrane binding, displaying higher dissociation constants with respect to the wt protein. Compressibility measurements reveal that both variants are more flexible than the wt, suggesting that the native central Ω-loop is important for the interaction with membranes. Such hypothesis is supported by molecular dynamics simulations. A minimal distance analysis indicates that in the presence of cardiolipin the central Ω-loop of the mutants is no more in contact with the membrane, as it happens instead in the case of wt cyt C. Such finding might provide a hint for the reduced membrane binding capacity of the variants and their enhanced peroxidase activity in vivo.

In situ phytoextraction of Mn and NH4+-N from aqueous electrolytic manganese residue solution by Pistia stratiotes: Effects of Fe/Co presence and rhizospheric microbe synergistic involvement

The electrolytic manganese industry produces a large amount of electrolytic manganese residue (EMR). Soluble Mn, NH4+-N, and other pollutants may be released from the open-air stacked EMR and transported to the environment along with rainfall or surface runoff. Aqueous EMR solution (AES) generally contains various elements required for plant growth, and phytoremediation can be applied to remove these pollutants from AES. Since the contents of Fe and Co vary greatly in AES depending on the ore sources as well as the pre-treatment processes, the presence of bioavailable Fe and Co at different levels may affect plant growth, the rhizosphere microbes, and pollutant removal. The present study investigated the in-situ removal of Mn(II) and NH4+-N from AES solution using free floating aquatic plant Pistia stratiotes, focusing especially on the effects of Fe/Co presence and rhizospheric microbe synergistic involvement on contaminant removal. The results showed that 69.08% of Mn and 94.99% of NH4+-N were removed by P. stratiotes in 24 d. Both the presence of Fe(II) and Co(II) facilitated the Mn(II) immobilization and increased Mn(II) removal by 19–31% due to the enhanced peroxidase activity and the increased Mn accumulating in roots The complete removal of Mn from AES was found in the presence of Fe(II) at 2 mg L−1 or Co(II) at 0.5 mg L−1 and more than 51% accumulated Mn in the roots was stored in the vacuole and cytoplasm. BioMnOx was found on the surface of the roots, revealing that rhizofiltration, rhizospheric plaque/biofilm formation, and Mn biogeochemical cycle exert synergic effects on Mn(II) immobilization. The findings of the present study demonstrate the feasibility of using P. stratiotes in the treatment of aqueous EMR solutions and the presence of an appropriate amount of bio-available Fe and Co can promote the removal of Mn(II) and NH4+-N.

MOFs-Based Magnetic Nanozyme to Boost Cascade ROS Accumulation for Augmented Tumor Ferroptosis.

The emerging cell death modality of ferroptosis has garnered increasing attention for antitumor treatment but still suffers from low therapeutic efficacy. A metal-organic frameworks (MOFs)-based magnetic nanozyme (PZFH) comprising porphyrin-based Zr-MOF (PCN) on zinc ferrite (ZF) nanoparticles modified with hyaluronic acid, delivering excellent magnetophotonic response for efficient ferroptosis, is reported here. PZFH shows multienzyme-like cascade activity encompassing a photon-triggered oxidase-like catalysis to generate O2 -, which is converted to H2O2 by superoxide dismutase-like activity and subsequent ·OH by magneto-promoted peroxidase (POD) behavior. Newly formed Fe─N coordination and increased Fe2+/Fe3+ levels in the PZFH contribute to the enhanced POD activity, which is further enhanced by accelerated surface electron transfer when exposure to alternated magnetic field. Accumulation of lipid peroxides is eventually accomplished through the conversion of ·OH radicals and singlet oxygen (1O2) produced through laser irradiation. When combined with the depletion of inhibition of glutathione and glutathione peroxidase 4, PZFH exhibits significantly enhanced ferroptosis in tumor-bearing mice, offering insights into nanomedicine for ferroptosis and holding great promise in clinical antitumor therapies.

Response of antioxidant activity, active constituent and rhizosphere microorganisms of Salvia miltiorrhiza to combined application of microbial inoculant, microalgae and biochar under Cu stress

Salvia miltiorrhiza, a widely used medicinal herb renowned for its properties in promoting blood circulation, removing blood stasis and alleviating pain, is currently facing quality degradation due to excessive heavy metal levels, posing a threat to medication safety. In order to investigate the effects of microbial inoculant, microalgae and biochar on the growth of Salvia miltiorrhiza under copper (Cu) stress, as well as its Cu absorption, antioxidant activity, active component contents and rhizosphere microbial community, a pot experiment was conducted. Salvia miltiorrhiza plants were cultivated in the soil containing 400 mg/kg of Cu for six months and treated with microbial inoculant, microalgae and biochar, either individually or in combination. Almost all soil amendment treatments led to an increase in root biomass. Notably, co-application of microbial inoculant and microalgae had the optimal effect with a 63.07 % increase compared to the group treated solely with Cu. Moreover, when microbial inoculant was applied alone or in combination with microalgae, the Cu content in plant roots was reduced by 19.29 % and 25.37 %, respectively, whereas other treatments failed to show a decreasing trend. Intriguingly, Cu stress increased the active component contents in plant roots, and they could also be enhanced beyond non-stress levels when microbial inoculant and microalgae were applied together or in combination with biochar. Analyses of plant antioxidant activity, soil properties and rhizosphere microorganisms indicated that these amendments may alleviate Cu stress by enhancing peroxidase activity, facilitating plant nutrient absorption, and enriching beneficial microorganisms capable of promoting plant growth and mitigating heavy metal-induced damage. This study suggests that the combined application of microbial inoculant and microalgae can reduce Cu levels in Salvia miltiorrhiza while enhancing its quality under Cu stress.

Synergizing Pyroelectric Catalysis and Enzyme Catalysis: Establishing a Reciprocal and Synergistic Model to Enhance Anti-Tumor Activity.

Nanozyme activity is greatly weakened by the microenvironment and multidrug resistance of tumor cells. Hence, a bi-catalytic nanoplatform, which promotes the anti-tumor activity through "charging empowerment" and "mutual complementation" processes involved in enzymatic and pyroelectric catalysis, by loading ultra-small nanoparticles (USNPs) of pyroelectric ZnSnO3 onto MXene nanozyme (V2CTx nanosheets), is developed. Here, the V2CTx nanosheets exhibit enhanced peroxidase activity by reacting V3+ with H2O2 to generate toxic ·OH, accelerated by the near-infrared (NIR) light mediated heat effect. The resulting V4+ is then converted to V3+ by oxidizing endogenous glutathione (GSH), realizing an enzyme-catalyzed cycle. However, the cycle will lose its persistence once GSH is insufficient; nevertheless, the pyroelectric charges generated by ZnSnO3 USNPs continuously support the V4+/V3+ conversion and ensure nanoenzyme durability. Moreover, the hyperthermia arising from the V2CTx nanosheets by NIR irradiation results in an ideal local temperature gradient for the ZnSnO3 USNPs, giving rise to an excellent pyroelectric catalytic effect by promoting band bending. Furthermore, polarized charges increase the tumor cell membrane permeability and facilitate nanodrug accumulation, thereby resolving the multidrug resistance issue. Thus, the combination of pyroelectric and enzyme catalysis together with the photothermal effect solves the dilemma of nanozymes and improves the antitumor efficiency.

Efficient bionic nanozyme based on AuPt NPs@ZIF-90 used for cyclic catalysis multimodal tumor therapy.

Multimodal therapy based on nanozyme is expected to become a novel option for tumor treatment. However, the catalytic efficiency of nanozymes and the hypoxia microenvironment of tumors limit the therapeutic effect of nanozymes. Herein, we screened a small molecule of midazole-2-carboxaldehyde (ICA) to prepare ZIF-90 and embedded gold and platinum nanoparticles to obtain ZAAP. ZAAP possessed a multi-enzymatic cascade of catalytic processes including greatly enhanced peroxidase activity via a "bionic" catalytic microenvironment (enhanced 23-fold), catalase and glucose oxidase activities, resulting in glucose decomposition to continuously supply H2O2, peroxidases for the catabolism of H2O2 to generate ROS and peroxidase-induced oxygen generation for continuous oxidation of glucose. All the above processes built a catalysis cycle that greatly promotes the generation of ROS and oxygen as well as the consumption of glucose, leading to the chemical dynamic therapy function and alleviating tumor hypoxia. In addition to the photothermal effect of ZAAP, a synergistic treatment of chemical dynamic/photothermal/starvation therapy was achieved, and the tumor inhibition rate reached 96.4% within 2 weeks, indicating that ZAAP shows great potential in nanozyme-based synergistic multimodal tumor treatment.

Nitrogen doped 1 T/2H mixed phase MoS2/CuS heterostructure nanosheets for enhanced peroxidase activity

Heteroatom doping and phase engineering are effective ways to promote the catalytic activity of nanoenzymes. Nitrogen-doped 1 T/2H mixed phase MoS2/CuS heterostructure nanosheets N-1 T/2H-MoS2/CuS are prepared by a simple hydrothermal approach using polyoxometalate (POM)-based metal–organic frameworks (MOFs) (NENU-5) as a precursor and urea as nitrogen doping reagent. The XPS spectroscopy (XPS) and Raman spectrum of N-1 T/2H-MoS2/CuS prove the successful N-doping. NENU-5 was used as the template to prepare 1 T/2H-MoS2/CuS with high content of 1 T phase by optimizing the reaction time. The use of urea as nitrogen dopant added to 1 T/2H-MoS2/CuS, resulted in N-1 T/2H-MoS2/CuS with an increase in the content of the 1 T phase from 80 % to 84 % and higher number of defects. N-1 T/2H-MoS2/CuS shows higher peroxidase activity than 1 T/2H-MoS2/CuS and a catalytic efficiency (Kcat/Km) for H2O2 twice as high as that of 1 T/2H-MoS2/CuS. The enhanced catalytic activity has probably been attributed to several reasons: (i) the insertion of urea during the hydrothermal process in the S-Mo-S layer of MoS2, causing an increase in the interlayer spacing and in 1 T phase content, (ii) the replacement of S atoms in MoS2 by N atoms from the urea decomposition, resulting in more defects and more active sites. As far as we know, N-1 T/2H-MoS2/CuS nanosheets have the lowest detection limit (0.16 µm) for the colorimetric detection of hydroquinone among molybdenum disulfide-based catalysts. This study affords a new approach for the fabrication of high-performance nanoenzyme catalysts.

Elevated CO2 concentration enhances drought resistance of soybean by regulating cell structure, cuticular wax synthesis, photosynthesis, and oxidative stress response

The atmospheric [CO2] and the frequency and intensity of extreme weather events such as drought are increased, leading to uncertainty to soybean production. Elevated [CO2] (eCO2) partially mitigates the adverse effects of drought stress on crop growth and photosynthetic performance, but the mitigative mechanism is not well understood. In this study, soybean seedlings under drought stress simulated by PEG-6000 were grown in climate chambers with different [CO2] (400 μmol mol−1 and 700 μmol mol−1). The changes in anatomical structure, wax content, photosynthesis, and antioxidant enzyme were investigated by the analysis of physiology and transcriptome sequencing (RNA-seq). The results showed that eCO2 increased the thickness of mesophyll cells and decreased the thickness of epidermal cells accompanied by reduced stomatal conductance, thus reducing water loss in soybean grown under drought stress. Meanwhile, eCO2 up-regulated genes related to wax anabolism, thus producing more epidermal wax. Under drought stress, eCO2 increased net photosynthetic rate (PN), ribulose-1,5-bisphosphate carboxylase/oxygenase activity, and alerted the gene expressions in photosynthesis. The increased sucrose synthesis and decreased sucrose decomposition contributed to the progressive increase in the soluble saccharide contents under drought stress with or without eCO2. In addition, eCO2 increased the expressions of genes associated with peroxidase (POD) and proline (Pro), thus enhancing POD activity and Pro content and improving the drought resistance in soybean. Taken together, these findings deepen our understanding of the effects of eCO2 on alleviating drought stress in soybean and provide potential target genes for the genetic improvement of drought tolerance in soybean.

Unlocking the Potential of Fertilizer and Pesticide Integration: Investigating the Promoting Effect of Organic Water-Soluble Fertilizers on Pesticide Degradation for Sustainable Agriculture

Abstract: 
 In the present study, the dynamic degradation profile of the pesticide acaricide was investigated in the presence of varying concentrations of organic water-soluble fertilizers. Field experiments were carried out to assess the influence of organic water-soluble fertilizers on pesticide degradation rates. It was found that, under specific conditions, organic water-soluble fertilizers can promote the degradation of pesticides. To elucidate the factors responsible for this observation, both biological and abiotic aspects were examined. With regard to the biological factors, plant peroxidase activity was analyzed at different concentration levels of organic water-soluble fertilizers during the course of the field experiments. It was determined that organic water-soluble fertilizers can enhance peroxidase activity. Concerning the abiotic factors, high-pressure mercury lamps were utilized in ultraviolet (UV) degradation experiments on the acaricide, incorporating various concentrations of organic water-soluble fertilizers. Furthermore, washing experiments simulating rainwater effects were conducted on representative vegetable species from the Brassicaceae, Asteraceae, Amaranthaceae and Amaranthus tricolor families. The results of the UV degradation experiment showed no significant difference in the acaricide degradation rate, regardless of the presence or absence of organic water-soluble fertilizers. Additionally, the washing experiment demonstrated the effectiveness of organic water-soluble fertilizers in reducing pesticide residues in common vegetable varieties. The findings of this study have important implications for pesticide management and agricultural practices, emphasizing the potential of organic water-soluble fertilizers in facilitating the degradation of pesticides and minimizing their environmental impact.

CeO2@nanogel/Au nanozymes to enhance peroxidase activity for a novel ultrasensitive SERS assay of H2O2 determination

Although the fact that H2O2 is employed in the medical, food, and chemical industries, trace detection of H2O2 remains a difficult and significant problem. For the detection of H2O2 residues, SERS assays based on enzyme inhibition techniques show promise. As a result, we csynthesized CeO2@nanogel/Au nanoparticles with dual enzyme-like capabilities to detect hydrogen peroxide in this study. CeO2 nanozymes possess both peroxidase-like and oxidase-like activities which could oxidize colorless 3,3′,5,5′-tetramethylbenzidine to blue TMB oxide. Surprisingly, after the addition of nanogel, CeO2@nanogel were prepared and both of its dual enzymatic activities decreased, especially the oxidase-like enzymes almost disappeared. To better investigate the enzyme catalytic activity, Au NPs were introduced and CeO2@nanogel/Au nanozymes were self-assembly prepared. Based on the significantly enhancement of CeO2@nanogel/Au nanozymes peroxidase activity, we developed a Raman detection method for H2O2 with TMBox as the probe molecule. The Raman intensity showed good linearity for the concentration of H2O2 in the range of 10-9 M−10−1 M with a correlation coefficient of R2 = 0.9922 and a detection limit of 2.68 × 10-12 M. Thus, the proposed SERS mode sensor exhibited good selectivity and interference resistance, providing a new avenue for environmental monitoring.

Non-heme Iron Single-Atom Nanozymes as Peroxidase Mimics for Tumor Catalytic Therapy.

Single-atom nanozymes (SAzymes) open new possibilities for the development of artificial enzymes that have catalytic activity comparable to that of natural peroxidase (POD). So far, most efforts have focused on the structural modulation of the Fe-N4 moiety to mimic the metalloprotein heme center. However, non-heme-iron POD with much higher activity, for example, HppE, has not been mimicked successfully due to its structural complexity. Herein, carbon dots (CDs)-supported SAzymes with twisted, nonplanar Fe-O3N2 active sites, highly similar to the non-heme iron center of HppE, was synthesized by exploiting disordered and subnanoscale domains in CDs. The Fe-CDs exhibit an excellent POD activity of 750 units/mg, surpassing the values of conventional SAzymes with planar Fe-N4. We further fabricated an activatable Fe-CDs-based therapeutic agent with near-infrared enhanced POD activity, a photothermal effect, and tumor-targeting ability. Our results represent a big step in the design of high-performance SAzymes and provide guidance for future applications for synergistic tumor therapy.

Piezoelectric enhanced sulfur doped graphdiyne nanozymes for synergistic ferroptosis–apoptosis anticancer therapy

Graphdiyne has excellent potential due to its enzymatic properties. Metal-free sulfur-doped Graphdiyne (S-GDY) has piezoelectric characteristics, and ultrasonic excitation of S-GDY enhances peroxidase activity. It can turn hydrogen peroxide into toxic hydroxyl radicals and induce apoptosis in 4T1 cells. More importantly, the ultrasound (US) enhanced nanozyme induced 4T1 cell ferroptosis by promoting an imbalanced redox reaction due to glutathione depletion and glutathione peroxidase 4 inactivation. S-GDY exhibited enhanced nanozyme activity in vitro and in vivo that may directly trigger apoptosis-ferroptosis for effective tumor therapy. Altogether, this study was expected to provide new insights into the design of piezoelectric catalytic nanozyme and expand their application in the catalytic therapy of tumors.Graphical

ATP and ssDNA aptamer-mediated peroxidase-like activity of rGO@PDA@CeO2 nanozyme: Exosomal proteins profiling and detection at physiological pH for colorimetric sensor

Exosomes are extracellular vesicles that inherit molecular markers from their parent cells for the transfer and delivery of membrane and cytosolic molecules between cells. Exosome detection and protein profiling provide noninvasive access to disease diagnosis and treatment. The nanozyme designed in this paper contains polydopamine-functionalization of graphene oxide (rGO@PDA) units that can adsorb ssDNA aptamers and CeO2 metal oxide nanosheet units with peroxidase activity. As auxiliary regulator, adenosine triphosphate (ATP) enhances peroxidase activity of rGO@PDA@CeO2 under a wide range of pH (4–7.4), which breaks through the limitation that traditional nanozymes can only exhibit peroxidase activity under acidic conditions. The ssDNA aptamers, which are recognition probes of exosome, can be adsorbed on the surface of rGO@PDA by aromatic stacking, competing with ATP molecules. Thus, the ssDNA aptamer acts as the switch for colorimetric sensor to flexibly regulate the peroxidase activity of the rGO@PDA@CeO2 under physiological conditions, and realizes sensitive detection of exosomes. This assay achieves a detection linear range of 0.46 × 107–108 particle/mL and a limit down to 3.81 × 105 particles/mL. In addition, this aptasensor sensitively profiles six exosomal protein across five cell types and clinical samples, suggesting their potential in clinic diagnosis.