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Methidathion (MTDT), a common organophosphorus pesticide with high insecticidal activity, is widely used for pest control. However, the misuse of MTDT leads to widespread residues and endangers human health. Therefore, it is crucial to develop a simple and highly sensitive method for the detection of MTDT residues. Herein, ZIF-90/MnO2/g-C3N4/Fe3O4 composite particles were synthesized: The MnO2 nanosheets could absorb the energy of the excited g-C3N4 to quench the ECL of g-C3N4 while ZIF-90 acted as a mimetic enzyme to catalyze the formation of thiocholine from MTDT. The thiocholine caused the reduction of MnO2 to Mn2+, restoring the ECL signal of g-C3N4. Combined with molecular imprinting technique, an electrochemiluminescence sensor was constructed for the determination of MTDT. The determination range was 1.00 × 10–9 ~ 7.00 × 10–7 g/L, and the detection limit was 6.58 × 10–10 g/L. Structurally similar organophosphorus pesticides showed no cross-reactivity. The method has high sensitivity and specificity, and has been successfully applied to the determination of MTDT residue in fruits with recoveries in the range 93.75% ~ 102.37%. [ABSTRACT FROM AUTHOR]

Glucose mainly serves as an energy source, highly crucial for development and respiration. Dysregulation can result in diabetes mellitus and related complications. In the current study, Erythrina suberosa sawdust-deposited manganese dioxide nanoparticles (MnO2 NPs) were used for colorimetric glucose detection. Sawdust-deposited MnO2 NPs were synthesized using Dalbergia sissoo extract and characterized with different analytical techniques such as XRD, FTIR, EDX, SEM, and UV–Vis spectrophotometer. Various functional groups in FTIR spectrum of MnO2 were reported such as –OH, Mn–O, and –OH coupled with Mn. XRD spectrum showed that the particles were in orthorhombic phase with a particle size of 38 nm. SEM analysis showed that the particles are dispersed homogenously on the surface of sawdust. EDX analysis showed the presence of various elements in the synthesized platform at different ratios. Color change from colorless to blue–green was noticed by the addition of glucose with the naked eye and analyzed confirmed by a UV–Vis spectrophotometer. To achieve optimum results, various parameters were optimized, such as nanoparticles loading, TMB concentration, pH, and incubation time. The proposed sensor's limit of detection and limit of quantification were calculated to be 1.8 × 10–8 M and 6.25 × 10–8 M, respectively, with a linear range of 1 × 10–9–3.6 × 10–7 M and an R2 value of 0.9992. The reaction time of the suggested sensor for glucose sensing was just 150 s. The proposed sensor has also been used for the detection of glucose in the urine samples of diabetic patients. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Bioprocess Engineering is the property of Chinese Journal of Bioprocess Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Donghua University (Natural Science Edition) is the property of Journal of Donghua University (Natural Science) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

CO2 conversion to formic acid in a single‐step reaction was investigated by incorporating MoSe2 nanoparticles into a cryogel‐based reactor system, resulting in a formate dehydrogenase (FDH) enzyme‐mimicking system. MoSe2 nanoparticles were synthesized via the microwave synthesis method, and they took part as the cofactor of the enzymatic system. Following, in combination with MACys‐Ru(bipyr)2‐MACys, MoSe2 nanoparticles were used as the cofactor of the conversion reaction in the MACys‐Ru(bipyr)2‐MACys‐co‐p(HEMA) cryogel column‐based reactor system. Synthesized nanoparticles were characterized by Fourier transformed infrared spectroscopy, field emission‐scanning electron microscopy, transmission electron microscopy, and energy dispersive x‐ray spectroscopy. The conversion reaction was monitored using high‐pressure liquid chromatography, and the parameters affecting the conversion yield (e.g., pH change and reusability of the reactor) were investigated. The results showed that the obtained mimic FDH‐based CO2 conversion column system worked like a reactor in the conversion of CO2 into formic acid. Besides, the developed cryogenic reactor provided a reusable single‐step conversion reaction with a high yield at room temperature in mild conditions. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fluorescent nanomaterials mainly include fluorescent carbon nanomaterials, fluorescent metal nanomaterials, multifunctional composite nanomaterials and metal frames. The materials not only have unique fluorescence intensity and high photostability, but also have unique quantum effect, small size and other properties of nanomaterials. In recent years, due to its high stability, low cost, easy preparation and other characteristics, it has gradually become the preferred material for mimic enzyme, which has brought new development opportunities for food, medical and biochemical fields. In this paper, the application of fluorescent nanomaterials as mimetic enzymes in biochemical analysis in recent years and the latest research progress are briefly summarized, and the future challenges and prospects of fluorescent nanomaterials as mimetic enzymes are prospected.

Natural enzymes are trace proteins produced by living cells in human body. It is precisely because of the existence of enzyme that the daily operation of organisms can be carried out orderly. At present, enzymes are used in many fields such as biomedicine, catalysis and detection. However, natural enzymes have many disadvantages, such as easy inactivation, poor stability, difficult synthesis, complex purification and high price, which hinder the large-scale application. In the past decades, as a new generation of artificial enzymes, nanomaterials mimic enzymes has gradually become a substitute for natural enzyme due to their high stability and good repeatability. Nanomaterial mimetic enzymes play an important role in many fields. The application of nanomaterial mimetic enzymes in the detection of O2·- and salvianolic acid in the field of electrochemical sensing was focused on in this paper, as well as in the detection of small biological molecules such as glutathione, glucose, cholesterol and H2O2, which can effectively detect the content of heavy metal salts and pesticides in the field of environmental pollution prevention and control, nanomaterials mimic enzymes can also prevent cancer, virus infection and other diseases by detecting specific sequences of DNA. Finally, it was expected that the future research of nanomaterials mimic enzymes will focus on the coupling between nanomaterials mimic enzymes, reaction mechanism, optimization of enzyme reaction environment and substrate selectivity, which will be the key research direction in the future.

The successful synthesis of ruthenium oxide/reduced graphene oxide (RuO2/rGO) heterostructures by one-pot hydrothermal method using graphene oxides and RuCl3 as precursors is reported. The heterostructures had high peroxidase-like (POD-like) activities, which catalyzes the oxidation of classical peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to create a blue colored reaction product. The catalytic activity was significantly enhanced by the synergistic effect between RuO2 nanoparticles and rGO. RuO2/rGO had a low Km of 0.068 mM and a high vmax of 1.228 × 10−7 M·s−1 towards TMB in the TMB-H2O2 catalytic oxidation system. In addition, the POD-like activity originating from the electron transfer mechanism was confirmed by cytochrome C (Cyt C) oxidation experiment. A colorimetric method based on RuO2/rGO heterostructures was developed with good sensitivity and selectivity for glucose detection with a limit of detection of 3.34 μM and a linear range of 0–1500 μM. The RuO2/rGO heterostructures have potential applications in the biomedical areas, such as biosensor and diagnostics. [ABSTRACT FROM AUTHOR]

A new type of composite metal–organic framework (Fe3O4@Au/MOF) nanoparticle was prepared by self-assembly method, which had the recyclability of Fe3O4 magnetic particles (Fe3O4NPs) and the advantage of gold nanoparticles (AuNPs) that could accelerate electron transfer. In addition, the mimic enzyme activity of Fe3O4@Au/MOF has been significantly increased because of the presence of Fe3O4NPs and AuNPs. Then physical and chemical characterization of the composite nanoparticle was carried out through advanced technologies, such as Fourier transform infrared spectroscopy, transmission electron microscope and X-ray photoelectron spectroscopy. Finally, based on the peroxidase-like activity enhanced by Fe3O4@Au/MOF composite nanoparticle, a highly specific enzyme-free electrochemical sensor was prepared for the detection of p-aminophenol. The results showed that the optimal catalytic system was the reaction temperature of 50 °C, the addition amount of Fe3O4@Au/MOF of 0.005 g, scanning rate of 0.1 V s−1, and buffer solution pH 5. The working curve equation is |Ipa|= 2.7372C + 2.1068, R2 was 0.9952, and the minimum detection limit was 0.38 μmol L−1 (S/N = 3) when the p-aminophenol concentration was located in the range of 0.1–10 mmol L−1. The detection system possessed an excellent recovery rate and anti-interference. In addition, the proposed method was validated to determine p-aminophenol in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The mimic enzyme has become a research hotspot in recent years because of its advantages of high stability, convenient preparation, and low price. In this article, Co3O4 nanosheets synthesized by a simple hydrothermal method possess the characteristics of a peroxidase-like activity. The results demonstrated that 3,3′,5,5′-Tetramethylbenzidine (TMB) could be oxidized by H2O2 to produce a typical blue product (oxTMB) which has a strong absorption at 650 nm wavelength with the help of the Co3O4 nanosheets. Thus, a simple and sensitive colorimetric detection method for H2O2 was established with a good linear relationship (2–200 μM) and a low limit of detection (0.4 μM). Meanwhile, the colorimetric product can effectively quench the fluorescence emitted by Ru(bpy)32+. Therefore, a colorimetric and fluorescence dual detection mode photochemical sensor for H2O2 detection is constructed based on the principle of the inner filter effect (IFE) between the colorimetric product (oxTMB) and Ru(bpy)32+. It can effectively avoid the false positive problem of a single detection mode. In the presence of glucose oxidase, glucose can be catalyzed to produce gluconic acid and H2O2; therefore, the sensor can also be used for the determination of glucose with a good linear relationship (0.02–2 μM) and a low limit of detection (5 nM). Experimental results showed that the sensor has a high sensitivity and strong anti-interference ability which can be used for the detection of actual samples.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rapid and accurate detection of phenolic wastewater from industries has created global concern. Herein, core–shell magnetic cellulose nanocrystal supported MOF (Fe3O4/CNC@ZIF-8) with robust peroxidase-like activity was synthesized with tannic acid as modifier and bridge. The peroxidase-mimic catalytic activity of as-prepared Fe3O4/CNC@ZIF-8 was further investigated using o-phenylenediamine (OPD) as peroxidase substrates in the presence of H2O2. Moreover, the experimental conditions were optimized and the kinetic analysis results showed that Fe3O4/CNC@ZIF-8 had higher affinity towards both the substrate OPD and H2O2 than horseradish peroxidase (HRP). Finally, a phenol colorimetric assay with a linear range of 2–200 µM and a detection limit of 0.316 µM was constructed. The catalytic mechanism of Fe3O4/CNC@ZIF-8 with phenol was further investigated by fluorescence test and the generated ·OH was proved to act a crucial role to produce quinoid radicals. Additionally, the synthesized magnetic material had excellent stability and recyclability and ease to separation. These results suggest that the Fe3O4/CNC@ZIF-8 may be one of the promising candidates as peroxidase mimic for colorimetric detection of phenol. [ABSTRACT FROM AUTHOR]

Nanocomposite membranes promoted by mimic enzyme was developed and optimized for biogas upgrading at moderately high pressure applications up to 15 bar. Zn based mimic enzyme (Zn-cyclen) was synthesized. Different concentrations of selected mimic enzyme were added in nanocomposite membranes containing 1% crystalline nanocellulose (CNC) and 2% polyvinyl alcohol (PVA). The addition of mimic enzyme improved separation performance. The optimal results were obtained with 5 µmol/g addition of mimic enzyme at 10 pH. Furthermore, the addition of mimic enzyme showed abrupt change in moisture uptake ability and the maximum values were found for addition of 0.005wt% of mimic enzyme loading. Permeation testing showed that presence of moisture content plays important role in the activation of mimic enzyme. Furthermore, at high pH values mimic enzyme showed improved CO2 hydration rates. SEM results exhibited smooth morphology and no significant different in membrane thickness with increase in the mimic enzyme concentration. Moreover, the decline in membrane performance was observed with increasing pressure up to 15 bar. CNC/PVA based membranes with optimal loading of mimic enzyme showed significantly high separation than pure PVA membrane; a permeance of 0.34 [m3(STP)/m2 bar hr] and selectivity of 42. [ABSTRACT FROM AUTHOR]

A facile colorimetric method for rapid detection of putrescine (Put) and cadaverine (Cad) based on the peroxidase-like activity of (Fe,Co) codoped-CDs was developed. With the enzymatic hydrolysis by diamine oxidase (EC 1.4.3.6, DAO), Biogenic amines (BAs) were decomposed to produce H2O2 which oxidizes 3,3',5,5'-tetramethyl-benzidine with the catalysis of (Fe,Co)-codoped CDs. By means of principal component analysis, Put and Cad were differentiated from BAs and their total amounts were detected by measuring the spectral absorption at 652 nm with a linear range from 0.25 to 10 mg kg−1. The colorimetric method was applied to the detection of Put and Cad in various fish samples with a detection limit ((3σ/k, n = 9)) of 0.06 mg kg−1. Besides verifying with HPLC, the recoveries of the colorimetric method were also tested by spiking standards at three levels with the range of 98.2%–115.7%, indicating that the established colorimetric method was accurate and sensitive. [ABSTRACT FROM AUTHOR]

Supramolecules mediated porous metal nanostructures are meaningful materials because of their specific properties and wide range of applications. Here, we describe a general and simple strategy for building Au-networks based on the guestinduced 3D assembly of Au nanoparticles (Au-NPs) resulted in host-guest interaction resolved sulfonatocalix[4]arene (pSC4)-modified Au-NPs aggregate. The diverse guest molecules induced different porous network structures resulting in their different oxidize ability toward glucose. Among three different kinds of guest, hexamethylenediamine-pSC4-Au-NPs have high sensitivity, wide linear range and good stability. By surface characterization and calculating the electrochemical properties of the Au-NPs networks modified glassy carbon electrodes, the giving Au-NPs network reveals good porosity, high surface areas and increased conductance and electron transfer for the electrocatalysis. The synthesized nano-structures afford fast transport of glucose and ensure contact with a larger reaction surface due to high surface area. The fabricated sensor provides a platform for developing a more stable and efficient glucose sensor based on supramolecules mediated Au-NPs networks. [ABSTRACT FROM AUTHOR]

An amphoteric phenolic compound with carboxyl and amino functional groups was synthesized and used as mimic glucose isomerase to catalyze the isomerization of glucose into fructose. The mimic enzyme displayed excellent catalytic activity for isomerization of glucose to fructose under mild conditions. The yield of fructose and selectivity of fructose could reach 33.0 % and 93.5 % after reacting 4 h, respectively, at pH 8.5 and 80 °C. The catalysis reaction rate constant kcat and Michaelis constants KmG, KmF were calculated. The activation energy of glucose to fructose was evaluated as 65.9 kJ mol−1. The possible catalysis reaction mechanism was proposed. The acid‐base groups on the catalyst play an important role in proton extraction and transfer, as well as in the rotation of local carbon chain, which leads to the highly selective isomerization of glucose into fructose under mild conditions. [ABSTRACT FROM AUTHOR]

Abstract Recently, mimic enzymes have obtained particular interest by their high activity, stability, and biocompatibility. In this work, by coupling copper hydroxide nanozyme and G-quadruplex/hemin DNAzyme to form a double-integrated mimic enzyme, a visual, sensitive and selective immunosensor was established to detect microcystin-LR (MC-LR). In this immunoassay, the microplates were modified with core-shell silica/nickel silicate as the substrate to capture MC-LR antigens. Then, Cu(OH) 2 nanocages with fine regulation were used as the label to capture the secondary antibody for immunoreaction and the DNA primer for propagation, followed by using hybridization chain reaction to amplify the DNA primer, thus numerous DNAzymes (G-quadruplex/hemin) can be formed on the surface of Cu(OH) 2 nanocages with the aid of hemin. Such double-integrated mimic enzyme including Cu(OH) 2 nanozymes and DNAzymes showed excellent peroxidase activity for the chromogenic reaction of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), which realized the visual detection of MC-LR in the range from 0.007 to 75 μg/L with the detection limit of 6 ng/mL, and thus provided the probability for the portable assessment of MC-LR in real sample. Graphical abstract Image 1 Highlights • A novel visible immunosensor was built to detect MC-LR sensitively and selectively. • Core-shell silica/nickel silicate was synthesized as the substrate to immobilize antigens. • Cu(OH) 2 nanocages were finely tuned with different catalytic abilities with ABTS. • Double-integrated mimic enzyme was prepared from Cu(OH) 2 nanozyme and G-quadruplex/hemin DNAzyme. [ABSTRACT FROM AUTHOR]

The construction of highly sensitive detection methods for hydroquinone (HQ) in environment and cosmetics is of great significance for environmental protection and human health. In this work, a novel detection method for HQ was successfully developed by constructing a metal-organic framework mimic enzyme colorimetric sensor (Mn/Fe-MOF@Pd 1.0) with excellent peroxidase-like activity, which was synthesized by doping manganese ions into Fe-MOF by introducing bimetallic active centers, thereby improving the peroxidase-like activity of Fe-MOF, and the acid resistance and stability of Mn/Fe-MOF were improved by supporting palladium (Pd NPs). It is proven that Mn/Fe-MOF@Pd 1.0 promoted the decomposition of hydrogen peroxide (H 2 O 2) to generate active species, therefore, oxidized chromogenic substrate discoloration. On this basis, the detection of HQ based on the Mn/Fe-MOF@Pd 1.0 colorimetric sensor was constructed, in which the limit of detection (LOD) was 0.09 μM in the linear range of 0.3–30 μM. Furthermore, Mn/Fe-MOF@Pd 1.0 was successfully used for detecting HQ in hydroquinone whitening cream and actual water samples. The successful synthesis of Mn/Fe-MOF@Pd 1.0 may provide new insights for further study of the enzyme-like activity of metal-organic framework composites, and the constructed facile and sensitive sensor system could broaden the application prospects of HQ detection. Schematic diagram of the synthesis of Mn/Fe-MOF@Pd and its colorimetric sensing of HQ [Display omitted] • A novel metal-organic framework composite Mn/Fe-MOF@Pd 1.0 was successfully synthesized. • The peroxide-like activity of Fe-MOF was increased by constructing bimetallic active sites. • The acid tolerance and stability of Mn/Fe-MOF were improved by loading palladium (Pd). • The mechanism of the peroxidase-like catalyzed reaction of Mn/Fe-MOF@Pd 1.0 was discussed. • The colorimetric sensor constructed by Mn/Fe-MOF@Pd 1.0 has high selectivity and sensitivity to hydroquinone (HQ). [ABSTRACT FROM AUTHOR]

Glutathione peroxidase is key for the removal of H2O2 and other hydroperoxides and therefore, it has an important role in the maintenance of the reactive oxygen species (ROS) metabolic balance in vivo. The native enzymes of the glutathione peroxidase family (GPx) have many defects, such as instability in vitro and poor availability. GPx mimetics has become a topic of considerable interest in artificial enzyme research. Many forms of GPx mimics have been synthesized, by including selenium and tellurium (double-bridged and single-bridged, 2-substituted and 6-substituted) in a mother molecule but differences the GPx mimics enzymatic activity have rarely been compared. We designed and synthesized eight cyclodextrin derivatives and used two types of enzyme assays to determine their activities. The results show that: (a) tellurium-containing GPx mimics have higher activity than that of selenium-containing GPx mimics; (b) dual-bridged mimics have higher activity than bis-bridged mimics; and (c) 2-position modified cyclodextrin has higher activity than 6-position modified cyclodextrin. [ABSTRACT FROM AUTHOR]

A carbon nanotube (CNT) enhanced polyvinyl alcohol (PVA)-mimic enzyme nanocomposite membrane was developed for CO 2 separation from flue gas under humidified conditions. A thin layer of PVA membrane containing mimic enzyme with uniformly dispersed CNTs on a porous support was prepared by dip coating. The thicknesses of the membranes was controlled by adjusting the polymer concentrations in the casting solutions. The membranes with the optimal concentration of the mimic enzyme (Zn-cyclen, 0.005 mmol/g) and different loadings of CNTs (0, 0.5, 1.0 and 1.5 wt%) in PVA at pH 5, 9 and 12 were prepared and tested for CO 2 /N 2 separation. The addition of the CNTs as nano-fillers increased the degree of water swelling in the membrane, thus also significantly improved the CO 2 /N 2 separation performance. A membrane containing 1.0 wt% CNTs at pH 12 showed the highest CO 2 permeance of 0.98 m 3 (STP)/m 2 h bar and a CO 2 /N 2 selectivity of 120, which is 30% higher in CO 2 permeance and 15% higher in CO 2 /N 2 selectivity compared with that of the counterpart membranes without CNT addition. [ABSTRACT FROM AUTHOR]

Prussian blue (PB) and gold modified polystyrene (PS) nanocomposites (PS@Au@PB) were synthesized and characterized by TEM, SEM, FTIR, UV–vis and EDS. The formation mechanism of PB induced by gold nanoparticles on PS nanospheres was proposed. The peroxidase-like and catalase-like activities of the synthesized nanocomposites were investigated. Peroxidase-like activity was found to follow Michaelis–Menten kinetics. The calculated kinetic parameters indicated that the PS@Au@PB nanocomposites possess strong affinity with the substrates and high catalytic activity. A sensitive method for glucose detection was developed using glucose oxidase (GO x ) and PS@Au@PB nanocomposites. The detection limit for glucose was determined to be as low as 3.9 μM and the linear range was from 15.6 to 250.0 μM. It suggests that PS@Au@PB nanocomposites can serve as a useful reagent in some biological detections. [ABSTRACT FROM AUTHOR]

This work presents a CO 2 membrane absorption process using a K 2 CO 3 solvent promoted by a Zinc complex containing a cyclic ligand of 1,4,7,10-tetracyclodode cane (Zn-cyclen) in a membrane contactor. Zn-cyclen (referred as mimic enzyme in this work) resembles the natural enzyme carbonic anhydrase (CA), but is more stable, has a much longer life time and much smaller molecular weight (235 g/mol) compared with CA. The mass transfer resistances in the membrane, gas and liquid phases in the membrane contactor were determined. The effects of gas film and liquid film resistances on the overall mass transfer coefficient were studied by varying the gas and liquid velocities. A tubular, hydrophobic porous glass membrane contactor with pore size of 200 nm was used to study the CO 2 absorption in potassium carbonate (0.5 M K 2 CO 3 ) solution promoted by different concentrations of mimic enzyme. The kinetic rate constant for absorption of CO 2 in the K 2 CO 3 solvent promoted by mimic enzyme was increased by 10 fold compared to the experiment without mimic enzyme. The significantly improved CO 2 separation performance demonstrates a novel approach to the effective enhancement of CO 2 absorption by using a low cost, chemically stable mimic enzyme. [ABSTRACT FROM AUTHOR]

A mimic enzyme promoted facilitated transport membrane was developed and optimized for postcombustion CO 2 capture. This composite membrane has a thin dense polyvinyl alcohol (PVA) selective layer containing a low molecular weight mimic enzyme and a polysulfone (PSf) ultrafiltration porous support. The selected mimic enzyme (i.e., Zn–cyclen) was characterized by HNMR 1 , ESI-MS and dissociation constant (pKa). The membrane morphology was studied by scanning electron microscope (SEM). The effect of mimic enzyme loading and the pH value of the membrane casting solution was investigated. The optimal Zn–cyclen loading of 5 µmol/g PVA and a pH value of 9 were determined. The influence of humidity on the performance of the membrane was also studied by conducting experiments at variable relative humidity levels (i.e., 50–100%). This membrane showed a CO 2 permeance of 0.69 [m 3 (STP)/(m 2 bar h)] and a CO 2 /N 2 selectivity of 107, which is significantly higher than that of a PVA membrane without mimic enzyme operating under the same conditions. [ABSTRACT FROM AUTHOR]

An efficient metalloporphyrins/HO/NO nitration of phenols has been developed. The total yield of nitrophenol could reach up to 55.1 %, which is about 4 and sixfold higher than that of horse radish peroxidase catalysis and peroxynitrite nitration, respectively. Furthermore, the nitration system attained an enhanced regioselectivity of 1.0 o/ p ratio, and exhibited a good substrate scope of monophenols. This protocol is environmentally friendly compared with HNO/HSO nitration, and stable, inexpensive and organic solvent tolerant compared with enzyme catalytic nitration and peroxynitrite nitration reaction. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this work, the Cu-based metal−organic frameworks composite, labelled as GOx@HKUST-1 @antibody, was prepared by simple reaction at room temperature to construct a competitive immunocolorimetric Aflatoxin B1(AFB1) sensor. In this assay, the HKUST-1 composite was given a triple function: glucose oxidase(GOx) stabilizer, peroxidase mimic and carrier material of AFB1 antibody. Under coordination modulation of benzoic acid, glucose oxidase encapsulated HKUST-1 presented octahedron with uniform size (average size: 10.3 µm), which was conducive to the immune reaction and magnetic separation. By immune combination and magnetic separation, GOx@HKUST-1 @antibody was redispersed and used as reactor of the cascade to amplify the detection signal. With the help of the external HKUST-1, GOx can catalyze glucose to produce hydrogen peroxide to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), which turns the solution blue. The target AFB1 can compete with AFB1-BSA-modified Fe 3 O 4 nanoparticles for GOx@HKUST-1 @antibody, which can result to the decreasing of the color signal. The method showed ultra high sensitivity for AFB1 with a detection limit of 0.004 ng mL−1, and high stability owing to the protection effect of HKUST-1 on the GOx and antibody. In addition, such competitive immunoassays can be extended to the detection of other biotoxin targets. [Display omitted] • GOx@HKUST-1 @antibody was obtained as immunocolorimetric aflatoxin B1 probe. • HKUST-1 was given a triple function: enzyme stabilizer, mimic and carrier material. • The composite was simply prepared under coordination modulation of benzoic acid. • Due to the cascade effect, the detection limit of sensor was as low as 0.004 ng mL−1. • The sensor showed high sensitivity, selectivity and long-term storage stability. [ABSTRACT FROM AUTHOR]

Highlights: [•] The catalytic activity of Pd NPs has been studied as mimic enzyme. [•] Pd NPs can be used for the detection of H2O2. [•] A new method for detecting the content of sarcosine in urine samples of prostatic carcinoma was proposed. [Copyright &y& Elsevier]

Abstract: The iron-based biomimetic compound was used as the mimic enzyme for the delignification of pulp and paper wastewater in this work. It was prepared by ferric sulfate and polycarboxylic acid (PA), forming the Fe–PA complex. The XRD pattern of the Fe–PA complex and its delignification mechanism were discussed. The optimal control conditions of Fe–PA complex on delignification were evaluated by using the Fe–PA complex in practical applications. The XRD pattern reflected the characteristic of a stereochemical cell with iron as the active center in Fe–PA complex, and the delignification mechanism of the Fe–PA complex was based on the complexation and flocculation. The optimal control conditions of Fe–PA complex on delignification were determined and the results showed as the dosage of Fe–PA complex (0.6mmol/L), dosage of H2O2 (60mg/L), pH of the reaction system (5.5) and contact time (30min). In addition, the excellent effect and low cost of Fe–PA complex in practical applications were determined by comparing those of conventional flocculation method, and these results illustrated an effective and economical method in pulp and paper wastewater treatment. [Copyright &y& Elsevier]

Here, a colorimetric aptasensor was constructed for sensitively detecting quinclorac (QNC), a common herbicide. The aptasensor involved a novel amplification strategy and a classical strand displacement strategy. The amplification strategy, termed exonuclease III (Exo III)-assisted cyclic release of phosphorodiamidate morpholino oligomer (PMO) mimic enzyme strategy, was developed based on two new findings on PMO: 1) DNA hybridized with PMO could resist Exo III digestion; 2) a designed G-rich PMO (named P2) could bind to hemin to form a G-quadruplex PMOzyme with peroxidase-like activity. In this strategy, a designed DNA-PMO duplex (D1-P1) completely hybridized with DNA2 (D2) in the other designed DNA-PMO duplex (D2-P2) to trigger D2 degradation by Exo III and cyclic release of P2. After that, the hemin-binding P2 catalyzed colorless tetra-methyl benzidine (TMB) to blue TMB+. The cycle process was performed at high Exo III concentrations without strict control and with constant background signals. In that case, the developed strategy was sensitive, efficient, easy to operate, reliable, and ultralow background. Meanwhile, a QNC aptamer was used to develop the strand displacement strategy based on magnetic beads. The colorimetric aptasensor was sensitive and selective for QNC detection with a detection limit of 7.1 ng mL−1. It was successfully applied to detect QNC in soil and river water with good recovery rates (92–98%) and a relative standard deviation (n = 3) <5%. The success of this study could provide a general reference strategy for developing sensitive aptasensors and other nucleic acid-related sensors. [Display omitted] • DNA hybridized with phosphorodiamidate morpholino oligomer resists Exo III digestion. • A G-rich phosphorodiamidate morpholino oligomer can bind to hemin to form a PMOzyme. • The PMOzyme has better peroxidase-like activity than the DNAzyme. • The enzymatic cycle is operated at high Exo III concentrations without strict control. • A colorimetric aptasensor is developed for sensitive detection of quinclorac. [ABSTRACT FROM AUTHOR]

The oxidation of adrenaline by dioxygen using copper phthalocyanine (CuPc) as the catalyzer was studied. CuPc has the optimal catalytic pH of 8.0 and the optimal catalytic temperature of 55 °C. It also has good storage and operation stability. The fiber optic adrenaline biosensor based on CuPc catalysis and fluorescence quenching was fabricated and studied. This sensor has the detection range of 7.0×10−5–1.5×10−4 mol/L, the response time of 4 min, good reproducibility and stability. [ABSTRACT FROM AUTHOR]

Two kinds of water-soluble metallophthalocyanines, binuclear cobalt phthalocyanine (Co2Pc2) and binuclear ferric phthalocyanine (Fe2Pc2), were synthesized through phenylanhydride-urea route and characterized by elemental analysis and FT-IR spectra. Binuclear metallophthalocyanine derivatives (Mt2Pc2) were immobilized on silk fibers and modified viscose fibers to construct bioactive fibers of mimic enzyme. Mt2Pc2 was used as the active center of bioactive fibers, viscose and silk fibers as the microenvironments. The catalytic oxidation ability of bioactive fibers on the malodors of methanthiol and hydrogen sulfide was investigated at room temperature. The experimental results indicated that the catalytic activity of such bioactive fibers was closely correlative to the types of bioactive fibers and substrates. [ABSTRACT FROM AUTHOR]

Some transition metals–sodium dodecyl sulphate (M–SDS) complexes are used to mimic the active group of peroxidase. The catalytic characteristics of these mimic-enzymes in the oxidation reaction of fluorescence substrate, pyronine B (PB), with hydrogen peroxide have been studied. Though the catalytic activities of M–SDS complexes are much lower than horseradish peroxidase (HRP), they can catalyze the oxidation reaction of PB with hydrogen peroxide leading to fluorescence quenching of PB. Mo(VI)–SDS complex exhibited the highest catalytic activity among same type mimic enzymes. Under optimum conditions, linear relationship between fluorescence quenching F0/F and concentration of H2O2 is in the range of 0.0–8.6 × 10−7 M. By coupling this mimic catalytic reaction with the glucose oxidase, glucose can be detected. Linear relationship between F0/F and concentration of glucose is in the range of 0.0–1.4 × 10−7 M. The method has been applied to the determination of glucose in human serum and the results are in good agreement with the method of phenol-4-aminoantipyrine. [ABSTRACT FROM AUTHOR]

Mn(II)–sodium dodecyl sulphate complex (Mn(II)–SDS) is used to mimic the active group of peroxidase. The catalytic characteristic of this mimic enzyme catalyst in the oxidation reaction of fluorescence substrate, tetraethyldiaminoxanthyl chloride (Pyronine B (PB)), with hydrogen peroxide has been studied. The experimental results show that Mn(II)–SDS complex has similar catalytic activity that of peroxidase. The steady-state catalytic rate depends upon mimic enzyme and substrate concentrations, and the Michaelis–Menten parameters Km, Vmax and Kcat are 7.6×10−6 M, 7.9×10−7 M s−1 and 7.9 s−1, respectively. The catalytic activity of Mn(II)–SDS complex is compared with those of HRP and Hemin. Though the catalytic activity of Mn(II)–SDS complex is 15.9% of that of HRP, it can catalyze the oxidation reaction of PB with hydrogen peroxide lead to fluorescence quenching of PB. Under optimum conditions, linear relationship between fluorescence quenching F0/F and concentration of H2O2 is in the range of (0.0–3.6) × 10−7 M. The detection limit is determined to be 3.0×10−9 M. By coupling this mimic catalytic reaction with the catalytic reaction of glucose oxidase (GOD), glucose can be detected. Linear relationship between F0/F and concentration of glucose is in the range of (0.0–1.4) × 10−7 M. The detection limit is determined to be 4.2×10−9 M. This method is applied to the determination of glucose in human serum and the results are in good agreement with the phenol-4-aminoantipyrine (4-AAP). [Copyright &y& Elsevier]

A novel [Co(L)(H 2 O) 2 ] (1) was obtained by hydrothermal method and it exhibited a 1D chain with exposed carboxyl groups, the unique coordination mode made it have unusual physical and chemical stability. Meanwhile, 1 showed peroxidase-like and weak oxidase-like activity. 1 as a peroxidase mimic enzyme had an excellent affinity for the substrates luminol and H 2 O 2. Compared with HRP, 1 had catalytic activity in a wide pH range and showed the best catalytic activity at pH 7.4. Meanwhile, the catalysis process of 1 was reversible and recyclable, and the catalytic activity remained stable after different pH and temperatures and long-time storage. Based on the inhibition of glutathione on luminol-H 2 O 2 -MOF 1 chemiluminescence signal, a chemiluminescence method for the determination of glutathione has been proposed with high sensitivity and selectivity and had been applied for detecting glutathione in cell lysate with satisfactory results. [Display omitted] • A novel Co (Ⅱ)-based MOF material with double enzyme mimetic activity was synthesized. • The unique coordination mode made Co-MOF have unusual physical and chemical stability. • The Co-MOF had favorable catalytic activity in a wide pH range. • A CL sensing method for glutathione was developed using the luminol-H 2 O 2 -Co-MOF system under neutral condition. [ABSTRACT FROM AUTHOR]

[Display omitted] •. • The CFCD exhibits good peroxidase-like activity. • The colorimetric method could be identified by bare eyes to realize on-the spot analysis and rapid detection. • The colorimetric/fluorescence sensor possesses fast response ability for GSH detection. In the current investigation, fluorescent carbon quantum dot nanoparticles were prepared using hydrothermal method. In order to achieve green preparation, waste corncob was used as raw material. Transmission electron microscope was used to examine the urface morphology of the synthesized fluorescent carbon quantum dot nanoparticles. Optical characterization was done by analyzing the ultraviolet–visible spectroscopy and fluorescence absorption spectrum. The peroxidase activity and catalytic performance of corncob fluorescent carbon quantum dots have been researched and compared with some simulated enzymes, and corncob fluorescent carbon quantum dots with peroxisase-like activity and fluorescence characteristics were used for the detection of glutathione by dual-mode colorimetric/fluorometric sensor. Our experimental results displayed that the corncob fluorescent carbon quantum dots have nanostructures and the catalytic activity of corncob fluorescent carbon quantum dots was better than that of other nanoparticles. The detection results of glutathione show that the limit of detection was 8.0133 nmol/L for the fluorometric sensor and the limit of detection was 0.3024 μmol/L for the colorimetric sensor with good selectivity and high sensitivity, exhibiting their potential for application in nanosensors. [ABSTRACT FROM AUTHOR]

Smart nanomaterials that can simultaneously detect and eliminate contaminants in water environment are significant for health protection. To achieve such goal, Co-MOF-74 was in-situ assembled on regenerated cellulose membranes followed by calcination process, thus achieving dual-functional Co 3 O 4 /cellulose derivative membrane (Co 3 O 4 /CDM) catalyst. The Co 3 O 4 morphology was readily controlled by further recrystallization of the deposited MOF precursor. Combining the high enrichment ability of cellulose membrane and outstanding peroxidase-active of Co 3 O 4 , the fast color reaction for phenol was accomplished within 10 min by Co 3 O 4 /CDM with the assistance of H 2 O 2 and 4-aminoantipyrine (4-AAP). Moreover, the Co 3 O 4 /CDM also portrayed an excellent degradation property for phenol elimination via sulfate radical-advanced oxidation processes (SR-AOPs). The degradation efficiency of phenol reached 93% in 20 min, and the possible mineralization mechanism was proposed based on the XPS and LC-MS analysis. Thus, Co-MOF-74 derived Co 3 O 4 /CDM shows excellent properties in aiding the colorimetric detection and degradation of phenol in aqueous solutions. [Display omitted] • In situ synthesis of Co-MOF-74 based Co 3 O 4 /cellulose derivative membrane (Co 3 O 4 /CDM) • Cellulose regenerated membrane can serve as a support for anchoring of Co-MOF-74 NPs. • Hydrothermal recrystallization approach can facilitate well distributed nanoparticles on membrane. • The recyclable Co 3 O 4 /CDM as enzyme mimics also showed high PMS activation property. • As-prepared Co 3 O 4 /CDM with dual-functional can enrich, detect and degrade phenol. [ABSTRACT FROM AUTHOR]

• Iron-cobalt co-doped carbon dots were synthesized with high peroxidase-like activity. • Doped-carbon dots were labeled with antibody for enzyme-linked immunosorbent assay. • Histamine in fish samples was accurately detected based on the immunoassay. Due to complex matrixes and specific reagent deficiency, the rapid detection of histamine is still a challenge to date. Based on the high peroxidase-like activity of iron-cobalt co-doped carbon dots, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was established for histamine detection using the mimic enzyme labeled with histamine antibody (His-Ab). Through the competitive binding of the labeled His-Ab to solid-phase and sample antigens, histamine content was detected with a linear range of 2.5–150 μg mL−1. The detection limit based on 3σ/K was 0.50 mg kg−1, which was much lower than those of commercial His-kit and HPLC methods. The ic-ELISA method was applied to histamine detection in fish samples with the recovery of (103.4 ± 0.5)%, which was in accord with those of commercial His-kit and HPLC methods. The results indicated that the established ic-ELISA method was suitable for rapid detection of histamine in fish samples with high accuracy, sensitivity and stability. [ABSTRACT FROM AUTHOR]

Abstract: The present work proposed a novel ECL protocol to probe the interactions between mimic enzymes and small biological molecules. Iron(II) phthalocyanine (FePc) and two imidazoles (imidazole and histidine) were chosen as model molecules of mimic enzyme and small biological molecules, respectively. The interactions between FePc and the imidazoles were probed by a sensitive luminol–O2 ECL system. Before complexing with the imidazoles, FePc can inhibit luminol–O2 ECL due to its electrocatalysis towards O2, however, after complexing with the imidazoles, FePc decreases the electrocatalysis, leading to the observation of an enhanced luminol–O2 ECL. Additionally, the proposed protocol enables detection limits of 1.0×10−8 molL−1 and 1.0×10−7 molL−1 to be achieved, respectively, for imidazole and histidine under the physiological pH condition (pH 7.4). [Copyright &y& Elsevier]

Nanozyme-based chemodynamic therapy (CDT) has emerged as an effective cancer treatment because of its low side effects and without the requirement of exogenous energy. The therapeutic effect of CDT highlights the pivotal importance of active sites, H 2 O 2 supplement and the glutathione (GSH) depletion of a nanozyme. The construction of a single kind of catalyst with multiple functions for the enhanced CDT is still a big challenge. In this work, seven types of bimetallic nanoparticles are synthesized using a metal-organic framework (MOF) as a stable host instead of a Fenton or Fenton-like ions supplier. Among them, Cu-Pd@MIL-101 with an alloy loading of 9.5 wt% modified by PEG (9.5% CPMP) is found to exhibit the highest peroxidase (POD) like activity combined with a superoxide dismutase (SOD) mimic activity and the function of GSH depletion. The in vivo results suggest that the stable and ultrafine nanoparticles possess favorable CDT effect for tumor and good biosafety as well as biocompatibility. This work has provided a credible strategy to construct nanozymes with an excellent activity and may pave a new way for the design of enhanced tumor CDT treatment., (© 2021 Wiley-VCH GmbH.)

We develop a low-background electrochemical biosensor for one-step detection of uracil DNA glycosylase (UDG) based on the host-guest interaction and iron-embedded nitrogen-rich carbon nanotube (Fe–N–C) that mimics enzyme-mediated electrocatalysis to achieve signal amplification. In this work, Fe–N–C is initially immobilized on a glassy carbon electrode, followed by the immobilization of β –cyclodextrin (β –CD). We construct the signal probes by assembling the methylene blue (MB)-labeled hairpin DNAs onto the surface of Au nanoparticles (AuNPs) to form the MB-hairpin/AuNP probes. Due to the steric effect of AuNPs and the stem–loop structure of hairpin DNA, MB is prevented from entering the cavity of β -CD on the electrode. In contrast, UDG enables the removal of uracil from the U•A pairs in the stem of hairpin DNA probe to generate apurinic/apyrimidinic (AP) sites, leading to the assembly of MB-hairpin/AuNP probes on the electrode based on host–guest reaction between β -CD and MB. Meanwhile, L-cysteine (RSH) is oxidized by O 2 to disulfide L-cystine (RSSR) and H 2 O 2. In the presence of H 2 O 2 , Fe–N–C catalyzes the oxidation of MB to generate an amplified electrochemical signal. Notably, the Fe–N–C-catalyzed oxidation of MB is mediated by the oxidation of RSH by O 2 instead of external H 2 O 2 , greatly simplifying the experimental procedures and improving the electrochemical signal. Due to the introduction of host–guest recognition, this electrochemical biosensor displays a low-background signal and high signal-to-noise ratio, enabling the one-step sensitive measurement of UDG with a detection limit of 7.4 × 10−5 U mL−1. Moreover, this biosensor can measure UDG in crude cell extracts and screen the inhibitors, providing a new platform for biomedical research. • We develop a low-background electrochemical biosensor for sensitive detection of uracil DNA glycosylase. • This biosensorinvolves the host–guest interaction and the FeCN mimic enzyme-based electrocatalysis signal amplification. • The FeCN-catalyzed oxidation of methylene blue is mediated by the oxidation of L-cysteine by O 2 instead of external H 2 O 2. • This biosensor exhibits high sensitivity and good selectivity. [ABSTRACT FROM AUTHOR]

• A facile approach to prepare a mimic multi-enzyme system was reported. • Efficient cooperation between chemo-catalytic and nature enzyme was achieved. • A biosensor for rapid detection of glucose was prepared based on the system. • Enhanced reusability and stability of immobilized GOx were achieved. The combination of chemo- and enzyme catalysis for multi-step tandem reactions has presented great challenges for decades. Herein, glucose oxidase (GOx) and a metal-organic framework MOF-545(Fe), which possessed peroxidase-like activity, were combined to construct a mimic multi-enzyme system for tandem catalysis. MOF-545(Fe) not only served as a support for the enzyme immobilization, but also contributed its catalytic activity to co-operate with natural enzymes for the cascade reactions. Based on the prepared mimic multi-enzyme system GOx@MOF-545(Fe), a colorimetric biosensor for glucose rapid detection was achieved with a low limit of detection (0.28 μM) and high specificity. Meanwhile, due to the protection of MOF-545(Fe), the immobilized enzyme exhibited excellent reusability and stability, e.g. long-term stability, thermal stability and anti-organic solvent stability. After being stored at room temperature for 7 days, the immobilized enzyme retained 92% of activity, while only 40% of activity of free enzyme was retained. And the immobilized enzyme maintained 71% of its initial activity after 5 cycles. This strategy of combining MOF mimics and natural enzymes for tandem catalysis may provide a novel and facile approach to design a highly efficient, stable, functional chemo-enzyme composites catalyst, which holds great promise for applications in biosensing, biopharmaceutical and industrial catalysis. [ABSTRACT FROM AUTHOR]