Natural Horseradish Peroxidase Research Articles

Peroxidase activity based on Cu2SnS3 quantum dots for the degradation and visual detection of zearalenone

For the first time, sulfur tin copper (Cu2SnS3) quantum dots with blue, green, yellow and red fluorescence were synthesized. It was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier infrared spectroscopy (FTIR). It was found that Cu2SnS3 quantum dots had excellent peroxidase catalytic properties and could effectively catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a dark blue product first and then a yellow product. Mie's constant shows that there is a greater binding capacity for substrates than natural horseradish peroxidase (HRP). FTIR shows that the catalytic activity of peroxide-mimetic enzymes of different colors of Cu2SnS3 quantum dots is related to the content of carboxyl groups (-COOH) on the surface of quantum dots. The essence of the catalytic activity originates from the generation of highly reactive hydroxyl radicals (•OH). Excitingly, Cu2SnS3 quantum dots were also able to degrade zearalenone (ZEN). Based on the peroxide-mimetic enzymatic activity and the catalytic degradation of Cu2SnS3 quantum dots for ZEN combined with molecularly imprinted polymers, a method was constructed for the degradation and visual detection of ZEN. Finally, the linear range for the determination of ZEN was 0.10–3.04 μmol/L with the limit of detection of 0.029 μmol/L. The color in the visual detection changes from yellow first to green and finally to dark blue. This method had been successfully used for the detection of ZEN in beer, corn and juice, respectively, with satisfactory results.

A polymetallic nanozyme with high peroxidase mimetic activity for rapid evaluation of total antioxidant capacity

Consumption of foods with high total antioxidant capacity (TAC) can reduce the risk of several illnesses in humans caused by the overproduction of pro-inflammatory cytokines in the body. Therefore, it is awfully important to build a rapid and sensitive platform for detecting TAC. In this work, a one-pot synthesized Bi0.3Fe1.7MoO6 with intrinsic peroxidase-like activity was made up for the shortcomings of natural enzymes for TAC detection. The peroxidase-like activity was evaluated by TMB chromogenic system in the presence of H2O2. Bi0.3Fe1.7MoO6 showed a higher affinity for H2O2 and TMB than that of natural horseradish peroxidase (HRP) and can be used to establish ascorbic acid (AA) sensing platform, which achieved a low detection limit (0.77 nM) and a good linear range (8–64 μM). The method has been proved to be applicable for the selective, stable, and reproducible TAC determination of food samples. Furthermore, the established TAC detection method applied to actual samples endows great potential for nutrition assessment.

TiO2-In-MIL-101(Cr) with Visible Light-Induced Peroxidase Activity for Colorimetric Detection of Blood Glucose.

In this work, metal-organic framework MIL-101(Cr) with regular morphology, stable structure, and good dispersion was prepared by the hydrothermal method. MIL-101(Cr) has two different sizes of pores, but after TiO2 nanoparticles (NPs) were in situ prepared, the two pores disappear. The result demonstrates that TiO2 NPs were located in the pores of MIL-101(Cr). TiO2-decorated MIL-101(Cr) forms an inside type II heterojunction and the band gap energy is narrowed, which can promote electron-hole separation and enhance the light absorption. Therefore, the heterojunction shows a high visible light-induced peroxidase-like activity. Kinetic studies exhibit that the K m value of TiO2-in-MIL-101(Cr) to TMB is 0.17 mM, and the affinity of TiO2-in-MIL-101(Cr) is higher than that of natural horseradish peroxidase (HRP). Then, a "turn-on" colorimetric assay based on TiO2-in-MIL-101(Cr) was constructed for the detection of blood glucose. The detection range is 1-100 μM (R 2 = 0.9950) with a limit of detection (LOD) of 1.17 μM. Compared with the clinical method, the constructed colorimetric method has accurate and reliable results for the clinical detection. The anti-interference experiment confirms that the method has high selectivity to glucose.

Artificial metalloenzyme with peroxidase-like activity based on periodic mesoporous organosilica with ionic-liquid framework

Artificial enzymes were developed as alternatives to natural enzymes. Considering the unique characteristics of periodic mesoporous organosilica (PMO) materials, a rational design approach was investigated to simulate the coordination sphere around the iron active center in natural horseradish peroxidase (HRP) and fabricate a new peroxidase-like nanozyme. Well-ordered mesoscopic structure, high surface area, tunable pore size, high thermal-hydrothermal stability, and facile surface functionalization are unique properties of PMOs which allow them be potential candidate for enzyme mimic catalysis. In the present study, a monofunctional PMO with ionic-liquid framework (PMO-IL) was prepared as a support to incorporate the iron protoporphyrin IX hemin. The interior surface of mesochannels were also modified by imidazole functional groups. The synthetic peroxidase-like nanomaterial was fully characterized using several techniques such as N2 adsorption-desorption analysis, Thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) spectroscopy, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDAX). Peroxidase-like activity of the current nanomaterial was evaluated using 2,2′-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS) in the presence of hydrogen peroxide in neutral pH condition. Michaelis-Menten kinetic parameters indicated enhanced affinity toward substrate. Results imply that the biomimetic pathways can be developed to achieve a new generation of nanozymes with excellent thermal stability and long-term storage stability which are promising as peroxidase mimics for various applications.

Food-borne melanoidin based peroxidase mimic for the precise detection of total antioxidant capacity

Drawing on the structure of the natural horseradish peroxidase (HRP) active site, in this study, food-borne Melanoidin and Fe3+ were used to construct a peroxide mimic enzyme, which possessed excellent peroxidase (POD)-like activity with the Km values of 0.088 mM and 0.358 mM toward 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), respectively. Given the good POD-like activity of Melanoidin/Fe3+, a convenient, selective, and sensitive method for the determination of ascorbic acid (AA) was defined. The method covered the 10–100 μM AA concentration range with a 1.19 μM detection limit. With favorable anti-interference and strong stability, Melanoidin/Fe3+ was successfully applied to the determination of AA in foods and medicines. The high activity of Melanoidin/Fe3+ provides a new strategy for designing high-performance nanozymes, which has great potential in exogenous dietary and healthcare applications.

Nanozyme Based on Dispersion of Hemin by Graphene Quantum Dots for Colorimetric Detection of Glutathione.

Compared with natural enzymes, nanozymes have the advantages of good catalytic performance, high stability, low cost, and can be used under extreme conditions. Preparation of highly active nanozymes through simple methods and their application in bioanalysis is highly desirable. In this work, a nanozyme based on dispersion of hemin by graphene quantum dot (GQD) is demonstrated, which enables colorimetric detection of glutathione (GSH). GQD was prepared by a one-step hydrothermal synthesis method. Hemin, the catalytic center of heme protein but with low solubility and easy aggregation that limits its catalytic activity, can be dispersed with GQD by simple sonication. The as-prepared Hemin/GQD nanocomplex had excellent peroxidase-like activity and can be applied as a nanozyme. In comparison with natural horseradish peroxidase (HRP), Hemin/GQD nanozyme exhibited a clearly reduced Michaelis–Menten constant (Km) when tetramethylbenzidine (TMB) was used as the substrate. With H2O2 being the substrate, Hemin/GQD nanozyme exhibited a higher maximum reaction rate (Vmax) than HRP. The mechanisms underlying the nanozyme activity were investigated through a free radical trapping experiment. A colorimetric platform capable of sensitive detection of GSH was developed as the proof-of-concept demonstration. The linear detection range was from 1 μM to 50 μM with a low limit of detection of 200 nM (S/N = 3). Determination of GSH in serum samples was also achieved.

Single-atom nanozymes catalytically surpassing naturally occurring enzymes as sustained stitching for brain trauma

Regenerable nanozymes with high catalytic stability and sustainability are promising substitutes for naturally-occurring enzymes but are limited by insufficient and non-selective catalytic activities. Herein, we developed single-atom nanozymes of RhN4, VN4, and Fe-Cu-N6 with catalytic activities surpassing natural enzymes. Notably, Rh/VN4 preferably forms an Rh/V-O-N4 active center to decrease reaction energy barriers and mediates a “two-sided oxygen-linked” reaction path, showing 4 and 5-fold higher affinities in peroxidase-like activity than the FeN4 and natural horseradish peroxidase. Furthermore, RhN4 presents a 20-fold improved affinity in the catalase-like activity compared to the natural catalase; Fe-Cu-N6 displays selectivity towards the superoxide dismutase-like activity; VN4 favors a 7-fold higher glutathione peroxidase-like activity than the natural glutathione peroxidase. Bioactive sutures with Rh/VN4 show recyclable catalytic features without apparent decay in 1 month and accelerate the scalp healing from brain trauma by promoting the vascular endothelial growth factor, regulating the immune cells like macrophages, and diminishing inflammation.

The peroxidase-like catalytic activity of in situ prepared cobalt carbonate and its applications in colorimetric detection of hydrogen peroxide, glucose and ascorbic acid

In this study, the cobalt carbonate (CoCO3) was in situ prepared using cobalt (Ⅱ) and carbonate at room temperature, and the intrinsic peroxidase-like activity of CoCO3 was demonstrated for the first time through the oxidation of chromogenic substrate 3, 3', 5, 5' - tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The effects of pH, reaction temperature, and incubation time on the catalytic activity of CoCO3 were studied. Under the optimal reaction conditions, the Michaelis constant (Km) of CoCO3 to H2O2 is 0.443 mM, which is lower than that of natural horseradish peroxidase and the previously reported peroxidase mimics. Furthermore, the mechanism exploration experiments confirm that the catalytic activity of CoCO3 is mainly attributed to the hydroxyl radical (•OH). Finally, based on the outstanding peroxidase-like activity of CoCO3, a colorimetric sensor for the detection of H2O2, glucose, and ascorbic acid (AA) was developed, which shows satisfactory selectivity and recovery. In addition, the total antioxidant capacity of three types of tea, dried lemon, three kinds of fresh fruit juice, and vitamin C tablet were determined. In short, this study reports a novel in situ generated CoCO3, which can be prepared rapidly at room temperature, eliminating the harsh, cumbersome, and time-consuming synthesis and purification process. The developed sensor based on the newly found excellent peroxidase-like activity of in situ prepared CoCO3 for the determination of H2O2, glucose, and AA is fast, simple, low cost, and high sensitivity.

Investigation on the Peroxidase-like Activity of Vitamin B6 and Its Applications in Colorimetric Detection of Hydrogen Peroxide and Total Antioxidant Capacity Evaluation.

The peroxidase-like activity of vitamin B6 (VB6) was firstly demonstrated by catalyzing the peroxidase chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) at the existence of H2O2. The influence of different factors on the catalytic property of VB6, including pH, temperature, VB6 concentration, and incubation time, were investigated. The steady-state kinetic study results indicate that VB6 possesses higher affinity to H2O2 than natural horseradish peroxidase and some other peroxidase mimics. Besides, the radical quenching experiment results confirm that hydroxyl radical (•OH) accounts for the catalytic process. Based on the excellent peroxidase-like catalytic activity of VB6, the colorimetric methods for H2O2 and gallic acid (GA) detection were developed by measuring the absorbance variance of the catalytic system. Under the optimal conditions, the linear ranges of the methods for H2O2 and GA determination with good selectivity are 50.0–600.0 μM and 10.0–50.0 μM, respectively. In addition, the developed method was applied in the detection of H2O2 in milk samples and evaluation of total antioxidant capacity of different tea infusions. This study may broaden the application prospect of VB6 in environmental and biomedical analysis fields, contribute to profound insight of the physiological functions of VB6, as well as lay foundation for further excavation of small-molecule peroxidase mimics.

Peroxidase Effect of Ce 2 (WO 4 ) 3 Nanoparticles to Detection of Glucose as a Colorimetric Sensor

During this study, Cerium tungstate nanoparticles (CWNPs) are synthesized by precipitation and calcination. Glucose detection was performed in solution and paper-based. For this purpose, glucose is converted to gluconic acid and Hydrogen peroxide (H2O2) in the presence of glucose oxidase and O2. CWNPs, due to their peroxidase activity in the presence of H2O2, lead to oxidation of TMB and production of TMBox. Subsequently, the glucose was detected in the solution and on paper by creating a blue color after 10 and 4 minutes. The significant difference in the rate of color change of sugars compared to glucose in the presence of CWNPs confirmed the selectivity of this approach.

Vanadium Disulfide Nanosheet Boosts Optical Signal Brightness as a Superior Enzyme Label to Improve the Sensitivity of Lateral Flow Immunoassay.

The color-enzyme lateral flow immunoassay (LFIA) has attracted widespread attention to expand the detection range and improve sensitivity via amplifying the color signal after catalyzing the substrate. As a kind of layered transition-metal dichalcogenide (TMD), the vanadium disulfide nanosheet (VS2NS) possesses superior peroxidase-like catalytic activity. Here, a VS2NS was applied as an enzyme label in the LFIA to detect 17β-estradiol (E2). Compared to natural horseradish peroxidase, the VS2NS expresses a more prominent enzyme catalytic performance, stability, and adsorption ability. Under optimal conditions, the calculated limit of detection (cLOD) of the VS2NS-based LFIA is 0.065 ng mL-1 for E2, which is sixfold lower than that of the optimized colloidal nanoparticle-based LFIA (cLOD = 0.406 ng mL-1). Besides, the detection linear range of the VS2NS-based LFIA can be widened by 1.5 times after the catalytic reaction. Moreover, the VS2NS-based LFIA exhibits excellent practicability in real sample detection. Simultaneously, this study helps open up the application of the VS2NS in the trace analysis of LFIAs, which can broaden TMDs' scope of application and better show their properties of color enzymes.

Vitamin B3 as a high acid-alkali tolerant peroxidase mimic for colorimetric detection of hydrogen peroxide and glutathione

Small-molecule enzyme mimics as biocatalysts have been extensively applied in diverse colorimetric sensors fabrication. However, excavating potential organic enzyme mimics with high catalytic activity still remains challenging. In this study, the peroxidase mimicking activity of nicotinic acid (VB3) was demonstrated for the first time through chromogenic substrate 3, 3′, 5, 5′-tetramethylbenzidine (TMB) at the existence of hydrogen peroxide (H 2 O 2 ). The catalytic activity of VB3 kept more than 80% of its optimum activity in a broad pH range of 3.0–9.0. In addition, the kinetic parameter (Michaelis constant, K m = 0.037 mM) of VB3 catalysis to H 2 O 2 is smaller than natural horseradish peroxidase (HRP) and previously reported peroxidase mimics. The catalytic mechanism of VB3 is mainly attributed to the active species of hydroxyl radical ( OH) and partially attributed to the superoxide free radicals ( O 2 − ). A convenient and sensitive colorimetric method based on VB3-H 2 O 2 -TMB chromogenic system for H 2 O 2 and glutathione detection was fabricated with the linear ranges of 5.0–100.0 μM and 5.0–50.0 μM, respectively. In short, this work will not only bring new enlightenment on the physiological functions and practical applications in the analytical field of VB3, but also provide a new type of structural reference for small-molecule enzyme mimics.

Fe-MIL-88A hexagonal rods as peroxidase mimetic at neutral pH for one-pot glucose colorimetric assay

• Rod-like Fe-MIL-88A was prepared via a simple hydrothermal method. • The Fe-MIL-88A possessed peroxidase-like properties under neutral conditions. • A one-pot colorimetric method for glucose detection was developed based on the Fe-MIL-88A as a peroxidase mimic. • The proposed method with high selectivity and acceptable reproducibility was accurate, reliable and applicable. In consideration of the promising application of peroxidase (POD)-like nanozymes in biomedical analysis, the development of POD mimics with good catalytic performance under neutral conditions remains significant. As a new catalyst, metal-organic frameworks have been explored as candidate nanozymes owing to their high catalytic activity, good stability, flexible and simple synthesis methods, diverse types, and properties. Herein, rod-like Fe-MIL-88A was successfully synthesized via a simple hydrothermal method. Fe-MIL-88A exhibited POD-like properties under neutral conditions and a stronger affinity for substrate 3,3 ' ,5,5 ' -tetramethylbenzidine and H 2 O 2 than natural horseradish POD. This result was primarily due to the additional exposed (100) facets of rod-like Fe-MIL-88A, which can catalyze the decomposition of H 2 O 2 to •OH more easily. Based on the POD-like properties of Fe-MIL-88A under neutral conditions, combined with glucose oxidase, a one-pot colorimetric analysis method for glucose detection was established. The proposed measurement had a linear range of 1–100 µM and a limit of detection of 0.45 µM. The colorimetric method was accurate, reliable, highly selective, convenient, and time-saving. Furthermore, the one-pot method was successfully applied to detect the concentration of glucose in human blood samples, and the measured results were consistent with those of commercial glucose meters, indicating that the proposed method can be a potential candidate for glucose detection.

Comparative study of Pd@Pt nanozyme improved colorimetric N-ELISA for the paper-output portable detection of Staphylococcus aureus

Staphylococcus aureus is a frequent pathogenic bacterium that has a significant detrimental influence on the health of the human body. Therefore, developing a practical and portable detection platform is critical to ensuring food safety. Nanozymes are a kind of engineered nanomaterials with superior enzyme-like activities, providing infinite possibilities for the development of highly sensitive analytical assays. In this study, mesoporous core−shell palladium@platinum (Pd@Pt) nanozymes were synthesized and then applied as a signal amplifier in Staphylococcus aureus colorimetric immunoassay. At the same time, a careful comparative study of the catalytic performance with natural horseradish peroxidase (HRP), Pd@Pt nanozymes and their complexes Pd@Pt-HRP (HRP coupling with Pd@Pt nanozymes) were firstly performed, as well as clever using a colorimeter to achieve portable signal output. Pd@Pt-HRP bioprobes enable remarkable peroxidase-like catalytic activity, resulting in the highest sensitivity with a limit of detection (LOD) improved from 1 × 105 to 1 × 103 CFU/mL. In all, this work conducted a valuable comparative study and presented an improved strategy for the portable detection of pathogenic bacteria, which was expected to be used in a wide range of applications in food safety regulation and biomedicals arenas.

Peroxidase-Mimicking Activity of Biogenic Gold Nanoparticles Produced from Prunus nepalensis Fruit Extract: Characterizations and Application for the Detection of Mycobacterium bovis.

In the present study, a facile, eco-friendly, and controlled synthesis of gold nanoparticles (Au NPs) using Prunus nepalensis fruit extract is reported. The biogenically synthesized Au NPs possess ultra-active intrinsic peroxidase-like activity for the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Chemical analysis of the fruit extract demonstrated the presence of various bioactive molecules such as amino acids (l-alanine and aspartic acids), organic acids (benzoic acid and citric acid), sugars (arabinose and glucose), phenolic acid, and bioflavonoids (niacin and myo-inositol), which likely attributed to the formation of stable biogenic Au NPs with excellent peroxidase-mimicking activity. In comparison with the natural horseradish peroxidase (HRP) enzyme, the biogenic Au NPs displayed a 9.64 times higher activity with regard to the reaction velocity at 6% (v/v) H2O2, presenting a higher affinity toward the TMB substrate. The Michaelis–Menten constant (KM) values for the biogenic Au NPs and HRP were found to be 6.9 × 10–2 and 7.9 × 10–2 mM, respectively, at the same concentration of 100 pM. To investigate its applicability for biosensing, a monoclonal antibody specific for Mycobacterium bovis (QUBMA-Bov) was directly conjugated to the surface of the biogenic Au NPs. The obtained results indicate that the biogenic Au NPs-QUBMA-Bov conjugates are capable of detecting M. bovis based on a colorimetric immunosensing method within a lower range of 100 to 102 cfu mL–1 with limits of detection of ∼53 and ∼71 cfu mL–1 in an artificial buffer solution and in a soft cheese spiked sample, respectively. This strategy demonstrates decent specificity in comparison with those of other bacterial and mycobacterial species. Considering these findings together, this study indicates the potential for the development of a cost-effective biosensing platform with high sensitivity and specificity for the detection of M. bovis using antibody-conjugated Au nanozymes.

Rational design of FeS2-encapsulated covalent organic frameworks as stable and reusable nanozyme for dual-signal detection glutathione in cell lysates

Developing artificial nanozyme has been demonstrated to be a promising approach to replace natural enzyme and promote industrialization of enzymes. Covalent organic frameworks (COFs) has aroused great interest in mimicking the structure of natural enzymes owing to its abundant functional group. However, without metal component, COFs suffered from unsatisfactory enzyme-like activity. Here, inspired by natural enzyme, FeS2-encapsulated COFs (FeS2@SNW-1) was designed as novel peroxidase-like nanozyme via hydrothermal and solvothermal method for the first time. The results of kinetic experiments demonstrate that the obtained peroxidase-like nanozyme has higher affinity for substrate molecules than natural horse radish peroxidase (HRP). Importantly, the potential application of FeS2@SNW-1 nanozyme was evaluated by dual-signal detection of the biomolecule glutathione (GSH) in the cell lysate. Meanwhile, the satisfactory results highlight that it is an effective strategy to improve the stability and reusability of the nanozyme by utilizing the outer layer of COFs to encapsulate the active site FeS2. In addition, facile fluorescent test strip was developed to detect GSH based on nanozyme. This study will not only provide favorable approach to design ideal nanozyme, but also broaden the analytical application of COF-based nanozyme.

Study on the peroxidase-like activity of cobalt phosphate and its application in colorimetric detection of hydrogen peroxide

The Co3(PO4)2.8 H2O nanozyme was in situ synthesized through direct reaction between cobalt (Ⅱ) and phosphate, and its peroxidase-like activity was studied in the presence of hydrogen peroxide (H2O2) using a chromogenic substrate 3, 3′, 5, 5′ - tetramethylbenzidine (TMB). The effects of pH value, temperature, and incubation time on the conversion of TMB to oxidized TMB (oxTMB) catalyzed by Co3(PO4)2.8 H2O in the presence of H2O2 were optimized. The peroxidase-like activity of Co3(PO4)2.8 H2O conforms to the Michaelis-Menten kinetics, and its Michaelis constant (Km) is 0.073 mM, showing a higher H2O2 affinity than natural horseradish peroxidase (HRP) and some other peroxidase nanozymes. The mechanism exploration experiment confirmed that the hydroxyl radical (•OH) is the main active species in the catalytic reaction of Co3(PO4)2.8 H2O. Finally, based on the inherent peroxidase-like activity of Co3(PO4)2.8 H2O, a simple colorimetric detection method for H2O2 was established, with a linear range of 15.0 − 100.0 μM and a detection limit of 4.385 μM. The method was applied to the determination of H2O2 in milk samples with the spiked recovery of 90.2%− 106.2%. This study reports a novel nanozyme that can be easily produced in situ, which is exempt from the harsh, cumbersome, and time-consuming synthesis and purification procedures. In addition, the H2O2 colorimetric detection method based on the nanozyme has the advantages of low cost, convenient, high sensitivity, and good selectivity.

Hemin loaded Zn−N–C single-atom nanozymes for assay of propyl gallate and formaldehyde in food samples

Single-atom nanozymes (SAzymes) show distinct advantages in catalytic activity and selectivity owing to their stability and special characteristic of maximum atomic utilization. Inspired by the structure of natural horseradish peroxidase (HRP), we developed a simple method for specific determination of both propyl gallate (PG) and formaldehyde (HCHO) by utilizing the intrinsic peroxidase mimics activity of hemin (hem) loaded Zn–nitrogen–carbon single-atom nanozymes (Zn–N–C@hem SAzymes). Zn–N–C@hem was prepared via a salt-template strategy and self-assembly, where hemin exhibits enhancing peroxidase-like activity can catalyze oxidation of colorless PG to yellow product. Upon introduction of HCHO into Zn–N–C@hem/PG system, complete suppression of PG oxidation was showed, resulting in distinguished decrease in absorbance. The colorimetric sensors of PG and HCHO based on Zn–N–C@hem/PG were developed at their respective linear range of concentration 1.25–200 mg/kg and 5–250 mg/kg. The practicability of the rapid analysis of PG and HCHO in food samples has been verified with reliable results.

Mesoporous Core-Shell Pd@Pt Nanospheres as Oxidase Mimics with Superhigh Catalytic Efficiency at Room Temperature.

Mesoporous Pt-Pd bimetallic core-shell nanospheres (mPd@Pt NSs) with palladium-rich cores and platinum-rich shells were synthesized via a simple, two-step, wet chemical strategy mediated by nitrogen-doped carbon dots. The BET surface area of mPd@Pt NSs was found to be 210.4 m2·g-1, which is significantly higher than the currently reported unsupported Pt-based nanomaterials. Because of the large active surface area, the as-prepared mPd@Pt NSs show superhigh oxidase activity and exhibit excellent oxidase-like catalytic efficiency with a catalytic constant (Kcat) as high as 2.1 × 103 s-1 at room temperature, which is of the same order of magnitude as the natural horseradish peroxidase (HRP) (Kcat = 4.3 × 103 s-1) at 37 °C and five-fold greater than the reported Kcat values of oxidase-like nanozyme obtained at 30 °C.

The synthesis and excellent peroxidase-like activity for the colorimetric detection of H2O2 of core-shell Fe/FeS2@C nanoparticles

In this work, we have successfully synthesized the core-shell Fe/FeS2@C nanoparticles using the arc-discharge method combined with heat treatment technology. The study shows that as-prepared core-shell Fe/FeS2@C nanoparticles exhibit excellent peroxidase-like activity. As for TMB and H2O2, the Michaelis–Menten constant value (Km: 0.1021 mM, 0.037 mM) of the core-shell Fe/FeS2@C nanoparticles are much lower than that of natural horseradish peroxidase (HRP)(Km: 3.7 mM), respectively. And the core-shell Fe/FeS2@C nanoparticles hold the two response ranges of the sensor to H2O2 are 2–200 μM and 200–1000 μM, respectively. The corresponding detection limits (LOD) are 0.42 μM (3σ/slope). Moreover, it is no evident influence on the result while adding Cu2+, K+, Na+, NH4+, Ni2+, Zn2+, Ca2+, Mg2+, NO3-, Glucose, and some biomolecules into the reaction systems. The excellent peroxidase-like activity for the colorimetric detection of H2O2 results from the synergistic effect between the Fe/FeS2 core and the graphite C shell, which increases the active sites of the core-shell Fe/FeS2@C nanoparticles sites as well as the electronic state densities of graphite C near its Fermi level, resulting in accelerating the cyclic effect between the Fe3+ and Fe2+. As a result, the Fe/FeS2@C core-shell nanoparticles acquire an excellent peroxidase-like catalytic performance.