摘要 :
Bacterial infection has become a global health issue.The misuseantibiotics has been resulting in increased drug resistance and bioaccumulation.Therefore,developing a highly safe antibacterial agent,with high antibacterial performa...
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Bacterial infection has become a global health issue.The misuseantibiotics has been resulting in increased drug resistance and bioaccumulation.Therefore,developing a highly safe antibacterial agent,with high antibacterial performance is demanding.Inspired by the natural motors performing automated tasks in complicated living environments,we demonstrate tadpole-like nanoparticles(TNPs)with several functions,including high photothermal conversion efficiency,peroxidase-like catalytic activity,glutathione peroxidase-like activity,and catalase-like activity.TNPs produce hydroxyl radical(>>OH)at an extremely low concentrationhydrogen peroxide0.006%,which can damage bacterial cell membranes,proteins,and DNA.Moreover,the glutathione peroxidase-like activity disrupts the anti-oxidative mechanismbacteria and improves the permeabilitythe cell membranes,consequently enhancing the killing effectROS.In addition,TNPs possess tadpole-like asymmetry to overcome Brownian motion,demonstrating strong directional motion propelled by 02.The in vivo experiments indicate that TNPs could also shorten the inflammatory period and promote angiogenesis,making them a very promising antibacterial agent.
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The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.e., direct blocking with N-ethylmalei...
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The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.e., direct blocking with N-ethylmaleimide (NEM), or using tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to interrupt disulfide bonds then blocking thiol groups with NEM, were applied to block thiol groups of ficin, ficin-NEM (ficin-N) and ficin-TCEP-NEM (ficin-TN) were produced, respectively. The blocking of thiol groups accelerated the peroxidase activity dramatically. The peroxidase catalytic activity of ficin-N and ficin-TN toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2 was about 2.5-fold and 5-fold increase compared with ficin, respectively, which accompanied a color change from colorless to blue and followed classic Michaelis-Menten model. The kinetic parameters indicated that higher affinity of ficin-N (K-m = 0.31) and ficin-TN (K-m = 0.39) to H2O2 compared with ficin (K-m = 0.58), and ficin-TN had the highest K-cat which increased by 6.5 times and 4.5 times for TMB and H2O2, respectively. According to these findings, a colorimetric method with high sensitivity for the detection of biothiols was developed due to sulfhydryl compounds inhibited the peroxidase activity of ficin. Comparing with ficin and ficin-N, ficin-TN had the widest detection range (0.01-16 mu M) and the lowest detection limit (3 nM). The practical applications of ficin-TN for biothiol determination in human serum samples have been demonstrated with satisfactory results. Ficin-N and ficin-TN are promising to apply to the bioanalysis.
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Considering the significance of H2O2 to chemical industry and environmental security, it is meaningful to develop convenient and sensitive analytical methods for H2O2 detection under the harsh environment. Herein, a hollow porous ...
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Considering the significance of H2O2 to chemical industry and environmental security, it is meaningful to develop convenient and sensitive analytical methods for H2O2 detection under the harsh environment. Herein, a hollow porous N-doped carbon skeleton coated on the surface of Co4N nanoparticles (Co4N@NC) was obtained by pyrolysis of Co-MOF. Carbon coating and the hollow porous structure of Co4N@NC can not only stabilize Co4N NPs, but also promote the electron transfer between the active center and subtracts, affording Co4N@NC high catalytic activity and stability under harsh conditions (such as high temperature, acidic and basic conditions, high salt concentration). Co4N@NC shows excellent peroxidase-like activity and performs well in colorimetric analysis for H2O2 and glucose with a detection limit of 0.032 mu M and 0.29 mu M, respectively.
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The Au-Hg amalgam anchored on the surface of reduced graphene oxide nanosheets (Au-Hg/rGO) has been synthesized successfully and characterized by various techniques such as transmission electron microscopy, X-ray diffraction and X...
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The Au-Hg amalgam anchored on the surface of reduced graphene oxide nanosheets (Au-Hg/rGO) has been synthesized successfully and characterized by various techniques such as transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The Au-Hg/rGO nanocomposites were found to possess excellent peroxidase-like catalytic activity and can quickly catalyze the oxidation of colorless 3,3’,5,5’-tetramethylbenzidine (TMB) to blue oxTMB in the presence of H_2O_2. The obvious color change offered accurate determination of the H_2O_2 concentration by recording the absorbance at 652 nm using a UV-vis spectrophotometer. The linear response range for H_2O_2 was from 5 μM to 100 μM and the detection limit was 3.25 μM (S/N = 3). Furthermore, a kinetic study indicated that the catalytic behavior of Au-Hg/rGO nanocomposites followed the typical Michaelis-Menten theory and Au-Hg/rGO nanocomposites showed good affinity for H_2O_2. We envision that the simple and sensitive colorimetric detection system holds great promising applications in clinical diagnostics and food and environment monitoring.
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A simple method was proposed for the preparation of CeVO_4. The as-synthesized CeVO_4 was, for the first time, demonstrated to exhibit both peroxidase-like and oxidase-like activity, which catalyzes the oxidation of 3, 3', 5, 5'-t...
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A simple method was proposed for the preparation of CeVO_4. The as-synthesized CeVO_4 was, for the first time, demonstrated to exhibit both peroxidase-like and oxidase-like activity, which catalyzes the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to form a typical blue solution in the presence or absence of H_2O_2. Moreover, the mechanism of its dual-enzyme activity was investigated in detail. The Michaelis constant (K_m) value for CeVO_4 (0.136mM) was lower than that of horseradish peroxidase (0.424mM) with TMB as the substrate. Interestingly, hydroquinone (H_2Q), dihydroxybenzene isomer, undergoes reduction accompanying the oxidation of TMB by the CeVO_4 oxidase mimic along with a visible color change, while the other two dihydroxybenzene isomers, i.e., resorcinol (RC) and catechol (CC), do not. Based on these findings, a colorimetric platform was developed to discriminate H_2Q from RC and CC. Under optimal conditions, a linear relationship between the H_2Q concentration and absorbance was observed from 0.05 to 8 μM, and a limit of detection of 0.04 μM was achieved. Moreover, this colorimetric platform can selectively reveal H_2Q concentrations in the presence of other dihydroxybenzene isomers.
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The emergence of drug-resistant bacterial strains has challenged the use of traditional antibiotic therapies. Therefore, there is an urgent need to develop novel antibacterial materials or methods to effectively eradicate bacteria...
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The emergence of drug-resistant bacterial strains has challenged the use of traditional antibiotic therapies. Therefore, there is an urgent need to develop novel antibacterial materials or methods to effectively eradicate bacteria. Herein, we demonstrated a novel antibacterial system consisting of cupric oxide nanoparticles combined with ascorbic acid (CuO NPs/AA), which could act as a potent nanoantibiotic targeting both Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) in vivo and in vitro, without noticeable cytotoxicity to mammalian tissue. The CuO NP/AA antibacterial system killed these microbes through a combined mechanism involving biofilm inhibition, cell membrane destruction, DNA damage, and enzyme inactivation. The antibacterial properties of CuO NPs/AA were mainly attributed to the generation of reactive oxygen species (e.g., .OH) produced through the intrinsic ascorbate oxidase- and peroxidase-like activities of CuO NPs, highlighting their use as antibacterial nanozymes to treat bacterial infections.
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In the present work, 13 p-substituted phenols with different functional groups have been systematically evaluated as metHb substrates by means of HPLC analysis. Non-hyperbolic kinetics were observed and Hill coefficients in the 0....
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In the present work, 13 p-substituted phenols with different functional groups have been systematically evaluated as metHb substrates by means of HPLC analysis. Non-hyperbolic kinetics were observed and Hill coefficients in the 0.37-1.00 range were obtained. The catalytic constants and the Hill coefficients were found to be quantitatively correlated with two independent variables: the energy level of the highest-occupied molecular orbital (Ehomo), which describes the intrinsic redox activity of the substrates and the pK_a-values, which are related to substrate ionization. Oxygen evolution in the presence of each phenol derivative was also measured, and good correlation between peroxidase-like and catalase-like activities of the protein was observed. It is also shown that bovine metHb, although less active than other peroxi-dases, may represent a good alternative from an economical point of view for phenol removal processes. The equations here obtained may serve as a basis to further explore the potential use of metHb-mediated reactions in the treatment of phenols in wastewaters and to predict which phenol will be removed most efficiently under this treatment with satisfactory reliability.
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Due to possessing an extremely small size and a large surface area per unit of volume, nanomaterials have specific characteristic physical, chemical, photochemical, and biological properties that are very useful in many new applic...
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Due to possessing an extremely small size and a large surface area per unit of volume, nanomaterials have specific characteristic physical, chemical, photochemical, and biological properties that are very useful in many new applications. Nanoparticles' catalytic activity and intrinsic ability in generating or scavenging reactive oxygen species in general can be used to mimic the catalytic activity of natural enzymes. Many nanoparticles with enzyme-like activities have been found, potentially capable of being applied for commercial uses, such as in biosensors, pharmaceutical processes, and the food industry. To date, a variety of nanoparticles, especially those formed from noble metals, have been determined to possess oxidase-like, peroxidase-like, catalase-like, and/or superoxide dismutase-like activity. The ability of nanoparticles to mimic enzymatic activity, especially peroxidase mimics, can be used in a variety of applications, such as detection of glucose in biological samples and waste water treatment. To study the enzyme-like activity of nanoparticles, the electron spin resonance method represents a critically important and convenient analytical approach for zero-time detection of the reactive substrates and products as well as for mechanism determination.
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Ficin has dual enzyme activity, i.e., protease and peroxidase-like activity. In some respects, its application is limited by the protease activity of ficin. Herein, we used tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to b...
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Ficin has dual enzyme activity, i.e., protease and peroxidase-like activity. In some respects, its application is limited by the protease activity of ficin. Herein, we used tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to break the three pairs of disulfide bonds of ficin, and then blocked the free thiol groups with N-ethylmaleimide (NEM) to synthesize ficin-TN. The results showed that ficin-TN had increased peroxidase-like activity and reduced protease activity. According to this phenomenon, we have exploited a colorimetric method with high sensitivity and selectivity for the one-step detection of glucose. Comparing with ficin, ficin-TN has wider detection range (0.1-300 mu M) and lower detection limit (88 nM), and our method is simpler and more timesaving than other two-step methods. Furthermore, the actual appliances of ficin-TN for glucose detection in human serum have been illustrated with satisfied result, suggesting that its promising utilization in various fields. (C) 2020 Elsevier B.V. All rights reserved.
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A bimetallic metal-organic framework of the type MOF(Co/2Fe), synthesized by a hydrothermal method, is demonstrated to exhibit peroxidase-like activity and oxidase-like activity. The material catalyzes the oxidation of 3,3,5,5-tet...
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A bimetallic metal-organic framework of the type MOF(Co/2Fe), synthesized by a hydrothermal method, is demonstrated to exhibit peroxidase-like activity and oxidase-like activity. The material catalyzes the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) to produce a blue product both in the absence and presence of H2O2. Its catalytic activity strongly depends on temperature and the solution pH value. With its dual enzyme mimetic activity, MOF(Co/2Fe) has the advantages of low cost, good stability, ease of preparation, and attractive MichaelisMenten behavior. The mechanisms and kinetics of the pseudo-enzymatic activity were studied in some detail. A colorimetric method was developed for determination of H2O2 that is based on the peroxidase-like activity of MOF(Co/2Fe). Under the optimal conditions, the absorbance of oxidized TMB at 652 nm increases linearly in the 10 to 100 mu M H2O2 concentration range, with a 5 mu M limit of detection.
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