Natural Horseradish Peroxidase Research Articles

Rapid aqueous preparation of carbon quantum dots and their application as nanozyme for the detection of hydrogen peroxide and uric acid

A green and rapid method was developed to synthesize a series of carbon quantum dots (Fe,N/CQDs, Fe,S/CQDs, S,N/CQDs and Fe,S,N/CQDs) through thermal decomposition using persimmon frost as a carbon source. All the synthesized CQDs have peroxidase-like activity, and the comparision of their steady-state kinetic parameters inferred that the peroxidase-like activity of Fe,S,N/CQDs is superior to those of Fe,S/CQDs and Fe,N/CQDs. Furthermore, Fe,S,N/CQDs exhibited good affinity towards 3,3′,5,5′-Tetramethylbenzidine (TMB) and H2O2 compared to natural horseradish peroxidase (HRP) and other nanozymes. In theory, uric acid (UA) can produce H2O2 with the catalysis by uricase. Fe,S,N/CQDs could catalyze the breakdown of H2O2 to produce reactive oxygen species (ROS), which can oxidize TMB (colorless) to oxTMB (blue). Based on the nanozyme-catalyzed oxidation of TMB, a simple and sensitive colorimetric sensor was developed for the quantitative analysis of H2O2 and UA. Low limit of detection (0.73 μM), wide linear range (1–80 μM) and good repeatability were obtained. The sensor was also demonstrated for the determination of UA in biological samples and satisfactory results were obtained.

Stimuli-responsive graphdiyne-silver nanozymes for catalytic ion therapy of dental caries through targeted biofilms removal and remineralization

Clinical mechanical decontamination and irrigants are not consistently effective in preventing intractable biofilm-induced dental caries, especially when biofilms have caused demineralization. Constructing stimuli-responsive nanocatalysts with improved catalytic activity for plaque biofilm removal and remineralization enhancement remains challenging. Herein, a coordination-reduction strategy driven by L-cysteine and graphdiyne (GDY) is employed to anchor low-dose Ag nanoparticles/Ag+ to GDY nanosheets to obtain GDY/L-cys/Ag (GLA) nanozymes. Subsequently, biomimetic approach is used to encapsulate GLA into a GS ointment composed of gelatin methacryloyl and sodium alginate to form biodegradable and adhesive GLA/GS. GLA demonstrates acidic plaque biofilm-activated peroxidase-like activity, surpassing affinity toward H2O2 than natural horseradish peroxidase, effectively catalyzing low-dose H2O2 into highly toxic hydroxyl radicals (•OH). This catalytic activity simultaneously enhances Ag+ release triggered by acidic plaque biofilms, generating additional reactive oxygen species that can suppress plaque biofilms on ex vivo human teeth by the synergistic effect of catalysis and released ions. Importantly, GLA/GS serves as template nucleation sites crosslinked to rich Ca2+, thereby attracting PO43- from saliva, prompting growth into hydroxyapatite on tooth enamel, facilitating rapid remineralization. Due to the safe nanocatalytic ion therapy, in an in vivo rodent model, GLA/GS + H2O2 effectively prevents dental caries without influencing surrounding oral tissues.

Electron Lock Manipulates the Catalytic Selectivity of Nanozyme.

Nanomaterials with enzyme-mimicking functions, termed nanozymes, offer attractive opportunities for biocatalysis and biomedicine. However, manipulating nanozyme selectivity poses an insurmountable hurdle. Here, we propose the concept of an energy-governed electron lock that controls electron transfer between nanozyme and substrates to achieve selectivity manipulation of enzyme-like catalysis. An electron lock can be constructed and opened, via modulating the nanozyme's electron energy to match the energy barrier of enzymatic reactions. An iron-doped carbon dot (FeCD) nanozyme with easy-to-regulate electron energy is selected as a proof of concept. Through regulating the conduction band which dominates electron energy, activatable oxidase and selective peroxidase (POD) with substrate affinity 123-fold higher than that of natural horseradish peroxidase (HRP) is achieved. Furthermore, while maintaining selectivity, FeCDs exhibit catalytic kinetics comparable to that of HRP upon transforming photons into electrons. Superior selectivity, efficient catalysis, and undetectable biotoxicity energize FeCDs as potent targeted drugs on antibiotic-resistant bacterial abscesses. An electron lock provides a robust strategy to manipulate selectivity toward advanced nanozymes.

Catalytic removal of malachite green from aqueous solution by a peroxidase-mimicking Cu-Al layered double hydroxide nanoparticle: Synthesis, characterization, and application

Nanozymes are nanomaterials with inherent enzyme-like activities that have recently received much attention due to their high catalytic activity, low cost, and high stability. This research aimed to investigate the applicability of copper-aluminum layered double hydroxide (CuAl-LDH) for the catalytic decolorization of malachite green (MG). The enzyme-mimic activity of the prepared particles was tested using a colorimetric approach based on the oxidation of 3,3', 5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2), which results in the production of a blue-colored product with maximum absorption at 652 nm. The impact of different factors, including pH, temperature, TMB, and H2O2 concentrations, on the catalytic performance of CuAl-LDH was assessed. The kinetic parameters (Km and Vmax) were obtained to be 14.3 × 10−3 mM and 96.1 × 10−8 M/s (for TMB), and 0.05 × 10−3 mM, and 71.9 × 10−8 M/s (for H2O2), respectively. Compared to natural horseradish peroxidase (HRP), CuAl-LDH showed a high affinity for H2O2 and TMB. In addition, the results showed that CuAl-LDH could decolorize MG by 100% under optimum conditions of pH 4, 3.42 µM MG, and 4 mg/mL CuAl-LDH at 50 °C and within 13 min. These findings demonstrate the potential of CuAl-LDH, with intrinsic peroxidase-mimic activity, to decolorize and detoxify MG from industrial wastewater.

Ficin-copper hybrid nanoflowers with enhanced peroxidase-like activity for colorimetric detection of biothiols.

The proteolytic enzyme ficin exhibits peroxidase-like activity but it is low and insufficient for real applications. Herein, we developed ficin-copper hybrid nanoflowers and demonstrated that they have significantly enhanced peroxidase-like activity of over 6-fold higher than that of free ficin, with one of the lowest Km and highest kcat values among all reported ficin-based peroxidase-like nanozymes. This was most likely caused by the synergistic catalysis of co-existing ficin and crystalline copper phosphate within nanoflower matrices having a large surface area. The nanoflowers were easily prepared by incubating ficin and copper sulfate at ambient temperature, causing coordination interactions between ficin's amine/amide moieties and copper ions, followed by concomitant anisotropic growth of petals composed of copper phosphate crystals with ficin. When compared to free ficin and natural horseradish peroxidase, the resulting nanoflowers' affinity toward H2O2 was greatly increased, yielding Km values of half and one-tenth, respectively, as well as noticeably improved stability. The nanoflowers were then applied to colorimetric determination of biological thiols (biothiols), such as cysteine (Cys), glutathione (GSH), and homocysteine (Hcy), based on their inhibition of nanoflowers' peroxidase-like activity, producing reduced color intensities as the concentration of biothiols increased. This strategy achieved highly sensitive colorimetric determinations of Cys, GSH, and Hcy after only 25-min incubation. Additionally, using this technique, biothiols in human serum were successfully determined with excellent precision, suggesting the potential application of this technology in clinical settings, particularly in point-of-care testing environments.

Imide-functionalized Cu-MOF: Biomimetic peroxidase activity and detection of hydrogen peroxide and ascorbic acid

The synthesis of MOF with imide-functionalized aromatic conjugated carboxylic acid ligands has been a hot topic of field. A novel biomimetic peroxidase material (Cu-BDCPPI) was designed, synthesized and characterized by combining imide-functionalized aromatic conjugated carboxylic acid ligands N, N′-bis (3,5-dicarboxyphenyl) homophthalic diimide (H4BDCPPI) and catalytically active copper ions. The potential catalytic effect of Cu-H4BDCPPI on peroxidase-like activity was found firstly. It can catalyze the typical colorimetric substrate 3,3′,5,5′-tetramethylbenzyl (TMB) from colorless to blue ox-TMB in the presence of H2O2, and its enzymatic catalytic activity is similar to that of natural horseradish peroxidase (HRP). So, based on the catalytic performance of Cu-BDCPPI, a colorimetric method and test strips can be established for the detection of H2O2 and ascorbic acid (AA). This work provides a feasible strategy for synthesizing MOF materials with peroxidase like properties, expanding the application of MOF materials in the field of biological analysis.

Bioinspired construction of histidine-doped porphyrin covalent organic framework nanozyme with enhanced peroxidase-like activity for sensitive uric acid detection

Imitating catalytic sites of natural enzymes is a promising approach to accurately improve the catalytic performances of nanozymes. Herein, inspired by the structure of natural horseradish peroxidase (HRP), three-component condensation strategy is unitized to design histidine (His) functionalized iron porphyrin covalent organic frameworks (Fe-COF-H3) nanozyme with peroxidase-like (POD-like) activity. The introduced His could form favorable microenvironment around the iron porphyrin structure, enhancing the catalytic capacity of COF nanozyme. Taking advantage of its excellent POD-like activity, Fe-COF-H3 was utilized as a carrier to immobilize urate oxidase (UOx) for the construction of enzyme-nanozyme cascade system (UOx@Fe-COF-H3). The UOx@Fe-COF-H3 was successfully applied for the colorimetric detection of uric acid (UA) in biological samples. This work not only offers a new insight to develop high-efficiency COF nanozymes, but also expands the application of COF nanozyme for the construction of enzyme-nanozyme cascade system.

Transition Metal High-Entropy Nanozyme: Multi-Site Orbital Coupling Modulated High-Efficiency Peroxidase Mimics.

Strong substrate affinity and high catalytic efficiency are persistently pursued to generate high-performance nanozymes. Herein, with unique surface atomic configurations and distinct d-orbital coupling features of different metal components, a class of highly efficient MnFeCoNiCu transition metal high-entropy nanozymes (HEzymes) is prepared for the first time. Density functional theory calculations demonstrate that improved d-orbital coupling between different metals increases the electron density near the Fermi energy level (EF ) and shifts the position of the overall d-band center with respect to EF , thereby boosting the efficiency of site-to-site electron transfer while also enhancing the adsorption of oxygen intermediates during catalysis. As such, the proposed HEzymes exhibit superior substrate affinities and catalytic efficiencies comparable to that of natural horseradish peroxidase (HRP). Finally, HEzymes with superb peroxidase (POD)-like activity are used in biosensing and antibacterial applications. These results suggest that HEzymeshave great potential as new-generation nanozymes.

A Facile Synthetic Approach for Zn2TiO4@NiCo2O4 Core‐Shell Nanoparticles Using Layered Double Hydroxide Precursors and Studies on Their Peroxidase‐Like Activity

AbstractIn the present work, a facile synthetic approach has been developed for Zn2TiO4@NiCo2O4 core‐shell nanoparticles (NPs) using layered double hydroxide (LDH) as precursors. The Zn2TiO4 microspheres (ZTS) constitute the core and the shell consists of NiCo2O4 nanoparticles. X‐ray diffraction (XRD) results confirm presence of both Zn2TiO4 and NiCo2O4 phases in Zn2TiO4@NiCo2O4 core‐shell nanoparticles. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses indicate formation of hierarchical porous shell structure of NiCo2O4 with varying thickness (132±20 nm to 171±35 nm) on the Zn2TiO4 spheres. Optical studies indicate bandgap of ~2.2 eV corresponding to NiCo2O4 nanoparticles in the Zn2TiO4@NiCo2O4 core‐shell nanoparticles. The Zn2TiO4@NiCo2O4 core‐shell nanoparticles possess high surface area (124 m2/g to 160 m2/g) as measured from Brunauer‐Emmett‐Teller (BET) analysis. Magnetic studies of Zn2TiO4@NiCo2O4 core‐shell nanoparticles indicate soft ferromagnetic and hard ferromagnetic behavior at 300 K and 5 K, respectively. The Zn2TiO4@NiCo2O4 core‐shell nanoparticles act as nanozyme and they exhibit better peroxidase‐like activity as compared to pure NiCo2O4 NPs and natural horseradish peroxidase (HRP).

Two-dimensional derivatives obtained by oxidation of MXene for simulating the oxidative properties of natural enzymes

Oxidation-derived nanoparticles (CDs/TiO x ) of Ti3C2 were prepared for the first time by simple oxidation of Ti3C2. CDs/TiO x was a two-dimensional hybrid of amorphous carbon and titanium oxides with a lateral dimension of about 50 nm. H2O2 was used as the oxygenator and the reduction product was H2O, which was environmentally friendly and inexpensive. Carboxyl, carbonyl, and hydroxyl groups are formed naturally during the oxidation derivative process. The decreased size increases the specific surface area and provides the possibility for the abundant presence of functional groups. The oxidation process converts MXene from reducing to oxidizing and achieves the ability of the derivatives to mimic peroxidase. Compared with natural horseradish peroxidase, the Michaelis constant for H2O2 was ten-fold lower. A cascade catalytic reaction system of glucose oxidase with CDs/TiO x was constructed, and the generated H2O2 could be further used to catalyze the oxidation of nicotinamide adenine dinucleotide (NADH) to NAD+. With the assistance of NAD+-dependent dehydrogenase, NADH could be restored to 95% of the initial level. This assay system can detect glucose levels scientifically and accurately in the range of 0.02–10 mM and remains viable after 20 cycles.

A smartphone-assisted colorimetric sensor based on Fe1-xS nanozyme for detection of glucose and ascorbic-acid in soft drinks

Due to their distinct enzyme-like catalytic activity, iron-based nanomaterials have attracted considerable attention from researchers in the field of biomolecular detection. However, the current literature predominantly focuses on iron oxide nanozymes, with limited attention given to iron sulfide (FexSy) nanozymes. In this work, a glutathione-modified Fe1-xS nanoparticles (Fe1-xS NPs) with a diameter of 4–6 nm was synthesized in one-pot aqueous solution at room temperature. The resulting Fe1-xS NPs exhibited superior peroxidase-like (POD) activity compared to natural horseradish peroxidase, indicating their potential as a promising alternative for POD applications. A sensor utilizing the POD activity of Fe1-xS NPs was developed for detecting glucose and ascorbic-acid (AA) in soft drinks. The detection limits for glucose and AA were determined to be 37 and 5.3 μM, respectively, with broader linear ranges of 200–700 and 10–500 μM. Moreover, Fe1-xS NPs demonstrated exceptional selectivity and anti-interference properties in detecting glucose and AA in soft drinks. Furthermore, this study proposed a smartphone-assisted colorimetric sensor based on Fe1-xS nanozymes for rapid and specific detection of glucose and AA. This technique has the potential to be utilized in the future for convenient and efficient detection of glucose and AA.

G-/C-rich ssDNA-based Fe and Cu/Fe nanoclusters with peroxidase-like activity for intracellular ROS production and cytotoxicity applications.

Five G-/C-rich single-stranded DNA (ssDNA) with different sequences and lengths were templated to prepare the DNA-Cu, DNA-Fe, and bimetallic DNA-Cu/M nanoclusters (NCs). The peroxidase-like activities of these nanomaterials were studied using H2O2 and 3,3',5,5''-tetramethylbenzidine (TMB) as the reaction substrates in HAc-NaAc buffer. It was found that T30-G2-Fe NCs and T30-G2-Cu/Fe NCs, with a size of about 2nm, exhibit similar and the strongest enzyme-like activity under optimal conditions. Both NCs possess a similarly high affinity to substrates, and the Michaelis-Menten constant (Km) values to TMB and H2O2 are about 11 and 2-3 times lower than those of natural horseradish peroxidase (HRP), respectively. The activity of both nanozymes decreases to about 70% after being kept for one week in pH 4.0 buffer at 4°C, which is comparable with HRP. Hydroxyl radicals (•OH) are the main reactive oxygen species (ROS) produced in the catalytic reaction. Moreover, both NCs can facilitate in situ generation of ROS in HeLa cells using endogenous H2O2. MTT assays indicate that the T30-G2-Cu/Fe NCs exhibit the strong selective cytotoxicity to HeLa cells over HL-7702 cells. The cellular viability is about 70% and 50% after incubating with 0.6M NCs for 24h without or with 2mM H2O2, respectively. The current study shows that the T30-G2-Cu/Fe NCs have the potential for chemical dynamic treatment (CDT).

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.