Polarographic Studies on Associations of Midecamycin and Chloroquine with Hydrogen Peroxide

IntroductionReactive oxygen species( ROS) including su-peroxide anion O· -2 ,hydrogen peroxide H2 O2 andhydroxyl radical OH· form in human body as a re-sult of various biochemical processes.ROS may beessential for many cellular functions such as bacte-rial ingestion and the redox regulation of signaltransduction.However,it is also recognized thatROS as harmful agents cause severe damage to sev-eral cell components ( nucleic acids,proteins,polyoses,lipoids,DNA,etc.) ,resulting in thepat…     

Prussian Blue/Reduced Graphene Oxide Composite for the Amperometric Determination of Dopamine and Hydrogen Peroxide

Prussian blue has significant application for the construction of electrochemical biosensors. In this work, Prussian blue-reduced graphene oxide modified glass carbon electrodes were successfully fabricated using electrochemical deposition. The high surface area of graphene oxide enhanced the deposition of Prussian blue and the resulting electrocatalytic activity. Infrared spectroscopy and scanning electron microscopy showed that the relatively porous Prussian blue was on the surface of reduced graphene oxide. Cyclic voltammetry showed that Prussian blue-coated reduced graphene oxide composite films improved electron transfer compared to Prussian blue films. The Prussian blue-reduced graphene oxide composite film provided higher response for the reduction of hydrogen peroxide and the oxidation of dopamine compared with the Prussian blue film due to synergistic effects between the reduced graphene oxide and Prussian blue particles. The sensitivity of the electrode was 0.1617 µA µM^?1 cm^?2. The linear dynamic range extended from 0.5 µM to 0.7 mM dopamine with a limit of detection equal to 125 nM. This work provided a versatile strategy for the design and construction of sensitive amperometric sensors with robust electrocatalytic behavior.     

Thermodynamic and Kinetic Studies on Oxidation of Pyrogallol Red by Hydrogen Peroxide in the Absence and Presence of Molybdenum(VI)

Abstract

The oxidation of pyrogallol red (PGR) by hydrogen peroxide has been studied both in the absence and presence of molybdenum(VI) at pH of 7.0 by spectrophotometric detection. The reaction rate was studied with a fix-time method from 0.5 to 4.5 min. The effect of reagents concentration, ionic strength and temperature was studied to give the optimum conditions. At the optimizing conditions the rate constant, energy and entropy of activation and frequency factor have been calculated using the Arrhenius and Eyring plots.     

A New Electrochemical Biosensor for Determination of Hydrogen Peroxide in Food Based on Well‐Dispersive Gold Nanoparticles on Graphene Oxide

Herein, we describe a new method for the detection of hydrogen peroxide (H₂O₂) in food by using an electrochemical biosensor. Initially, ultrafine gold nanoparticles dispersed on graphene oxide (AuNP‐GO) were synthesized by the redox reaction between AuCl₄^? and GO, and thionine‐catalase conjugates were then assembled onto the AuNP‐GO surface on a glassy carbon electrode. With the aid of the AuNP‐GO, the as‐prepared biosensor exhibited good electrocatalytic efficiency toward the reduction of H₂O₂ in pH 5.8 acetic acid buffer. Under optimal conditions, the dynamic responses of the biosensor toward H₂O₂ were achieved in the range from 0.1 µM to 2.3 mM, and the detection limit (LOD) was 0.01 µM at 3s_B. The Michaelis–Menten constant was measured to be 0.98 mM. In addition, the repeatability, reproducibility, selectivity and stability of the biosensor were investigated and evaluated in detail. Finally, the method was applied for sensing H₂O₂ in spiked or naturally contaminated samples including sterilized milk, apple juices, watermelon juice, coconut milk, and mango juice, receiving good correspondence with the results from the permanganate titration method. The disposable biosensor could offer a great potential for rapid, cost‐effective and on‐field analysis of H₂O₂ in foodstuff.     

Electrochemical Sensing of Ascorbic Acid,Hydrogen Peroxide and Glucose by Bimetallic (Fe,Ni)−CNTs Composite Modified Electrode

In this research, bimetallic supported CNT modified electrode ( Fe,Ni/CNTs/GCE) has been developed for sensitive, stable and highly elctroactive sensing of glucose, ascorbic acid and hydrogen peroxide. Transition metals such as Iron (Fe) and Nickel (Ni) offer high electrical and thermal conductance, high active surface‐to‐volume ratio and presence of d‐band electrons gives enhanced electrocatalytic behavior. While, CNTs provide high surface area, stability and excellent conductivity. Synthesized material is characterized by SEM, EDS, XRD and FTIR to access morphology, elemental composition and structure. This unique combination is employed for the electrochemical sensing of ascorbic acid, glucose and hydrogen peroxide and different experimental parameters are optimized. Fe,Ni/CNTs/GCE shows good sensing efficiency at pH 7.4 which is ideally suitable for variety of analytes. The modified electrode also show good reproducibility and sensitivity under optimized conditions and can be reused upto 30 cycles without compromising the efficiency. With good linearity, reproducibility and limit of detection, this material possess significant potential as non‐enzymatic biosensor for variety of analytes.     

Facile Synthesis of Ultra‐wide Two Dimensional Bi2S3 Nanosheets: Characterizations,Properties and Applications in Hydrogen Peroxide Sensing and Hydrogen Storage

The ultra‐wide two dimensional Bi₂S₃ nanosheets (2D Bi₂S₃ Ns) as non‐toxic graphene‐like nanomaterials have been prepared through solvothermal decomposition of a single‐source precursor, Bi(S₂CNEt₂)₃, in ethylenediamine media for 2 h in 180 °C. The morphology, structure, properties and catalytic activity of prepared 2D Bi₂S₃ Ns were characterized with XRD, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV‐Visible spectroscopy, cyclic voltammetry (CV), amperometry, electrochemical charge/discharge technique and electrochemical impedance spectroscopy (EIS). The SEM image showed the 2D Bi₂S₃ Ns with a thickness of 15±4 nm and lengths of several micrometers is synthesized. The UV−Vis spectrum of 2D Bi₂S₃ Ns showed high sensitivity to visible‐near infrared light with its direct energy band gap of ≈1.22 eV. These Bi₂S₃ Ns showed high electron transfer ability and good electrochemical behavior and also exhibited electro‐catalytic activity toward the reduction‐oxidation of hydrogen peroxide. It is found that Bi₂S₃ Ns could detect H₂O₂ at wide linear concentration range (50.0 μM–8.0 mM) with detection limit 8 μM, using amperometry as measuring technique. Also the synthesized Bi₂S₃ Ns exhibited excellent electrochemical H₂ storage properties. As a result, based on above properties, the Bi₂S₃ Ns can be used as a valuable and useful nanomaterial for H₂ storage, high‐energy batteries, electrocatalytic fields and electrochemical sensing.     

Influence of Modifications on the Efficiency of Pyrolysed CoTMPP as Electrode Material for Horseradish Peroxidase and the Reduction of Hydrogen Peroxide

A tailor‐made horseradish peroxidase (HRP) bulk composite electrode was developed on the basis of pyrolyzed cobalt tetramethoxyphenylporphyrin (CoTMPP) by modifying pore size and surface area of the porous carbon material through varying amounts of iron oxalate and sulfur prior to pyrolyzation. The materials were used to immobilize horseradish peroxidase (HRP). These electrodes were characterized in terms of their efficiency to reduce hydrogen peroxide. The heterogeneous electron transfer rate constants of different materials were determined with the rotating disk electrode method and a k_S (401±61 s^?1) exceeding previously reported values for native HRP was found.     

贮氢合金材料电化学与表面性能的研究进展

贮氢合金材料电化学与表面性能的研究进展①杨勇李骏林祖赓（厦门大学化学系，固体表面物理化学国家重点实验室，厦门３６１００５）八十年代后期以来，人们对地球的环境保护提出了更高的要求，而便携式电器（如移动电话，摄像机与笔记本电脑等）对电池的需求也大量增加...     

Automated Determination of Hydrogen Peroxide at the Micro-Molar Level in Rainwater and Snow Using a Stopped-Flow Approach in a Hybrid Sequential Injection/Flow Injection Manifold

A new automated method is reported for the determination of H₂O₂ in real samples. The method is based on the quenching effect of the analyte on the reaction between tris(2-carboxyethyl)phosphine (TCEP) and Ellman's reagent (DTNB). All necessary steps were accomplished under flow conditions using a hybrid sequential injection (SI)/flow injection (FI) setup. The sensitivity was enhanced by applying a stopped-flow step (120 s) in order to promote the reaction between H₂O₂ and TCEP. The proposed analytical protocol was validated for linearity (10–75 µmol L^?1), limits of detection (c _L = 1.0 µmol L^?1), quantitation (c _Q = 3.3 µmol L^?1), precision (s _r = 1.3–1.7%), accuracy, and selectivity. It was then applied successfully to the analysis of H₂O₂ in spiked rainwater and snow samples.     

Immobilization of Enzymes on the Nano‐Au Film Modified Glassy Carbon Electrode for the Determination of Hydrogen Peroxide and Glucose

A new enzyme‐based amperometric biosensor for hydrogen peroxide was developed relying on the efficient immobilization of horseradish peroxidase (HRP) to a nano‐scaled particulate gold (nano‐Au) film modified glassy carbon electrode (GC). The nano‐Au film was obtained by a chitosan film which was first formed on the surface of GC. The high affinity of chitosan for nano‐Au associated with its amino groups resulted in the formation of nano‐Au film on the surface of GC. The film formed served as an intermediator to retain high efficient and stable immobilization of the enzyme. H₂O₂ was detected using hydroquinone as an electron mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano‐Au film maintained excellent electrocatalytical activity to the reduction of H₂O₂. The experimental parameters such as the operating potential of the working electrode, mediator concentration and pH of background electrolyte were optimized for best analytical performance of amperometry. The linear range of detection for H₂O₂ is from 6.1×10^?6 to 1.8×10^?3 mol L^?1 with a detection limit of 6.1 μmol L^?1 based on signal/noise=3. The proposed HRP enzyme sensor has the features of high sensitivity (0.25 Almol^?1cm^?2), fast response time (t_90%≤10 s) and a long‐term stability (>1 month). As an extension, glucose oxidase (GOD) was chemically bound to HRP‐modified electrode. A GOD/HRP bienzyme‐modified electrode formed in this way can be applied to the determination of glucose with satisfactory performance.     

Electrocatalytic Activity of Nanohybrids Based on Carbon Nanomaterials and MFe2O4 (M=Co,Mn) towards the Reduction of Hydrogen Peroxide

We report the advantages of hybrid nanomaterials prepared with electrogenerated ferrites (MFe₂O₄; M: Co, Mn) and multi‐walled carbon nanotubes (MWCNTs) or thermally reduced graphene oxide (TRGO) on the electro‐reduction of hydrogen peroxide. Glassy carbon electrodes (GCE) modified with these hybrid nanomaterials dispersed in Nafion/isopropanol demonstrated a clear synergism on the catalytic reduction of reduction of hydrogen peroxide at pH 13.00. The intimate interaction between MFe₂O₄ and carbon nanomaterials allowed a better electronic transfer and a facilitated regeneration of M²⁺ at the carbon nanomaterials, reducing the charge transfer resistances for hydrogen peroxide reduction and increasing the sensitivities of the amperometric response.     

Insights into the Mechanism of the Reaction between Tetrachloro‐p‐Benzoquinone and Hydrogen Peroxide and their Implications in the Catalytic Role of Water Molecules in Producing the Hydroxyl Radial

Detailed mechanisms for the formation of hydroxyl or alkoxyl radicals in the reactions between tetrachloro‐p‐benzoquinone (TCBQ) and organic hydroperoxides are crucial for better understanding the potential carcinogenicity of polyhalogenated quinones. Herein, the mechanism of the reaction between TCBQ and H₂O₂ has been systematically investigated at the B3LYP/6‐311++G** level of theory in the presence of different numbers of water molecules. We report that the whole reaction can easily take place with the assistance of explicit water molecules. Namely, an initial intermediate is formed first. After that, a nucleophilic attack of H₂O₂ onto TCBQ occurs, which results in the formation of a second intermediate that contains an OOH group. Subsequently, this second intermediate decomposes homolytically through cleavage of the O? O bond to produce a hydroxyl radical. Energy analyses suggest that the nucleophilic attack is the rate‐determining step in the whole reaction. The participation of explicit water molecules promotes the reaction significantly, which can be used to explain the experimental phenomena. In addition, the effects of F, Br, and CH₃ substituents on this reaction have also been studied.     

Reagentless Biosensor for Hydrogen Peroxide Based on the Immobilization of Hemoglobin in Platinum Nanoparticles Enhanced Poly(chloromethyl thiirane) Cross‐linked Chitosan Hybrid Film

An unmediated hydrogen peroxide (H₂O₂) biosensor was prepared by co‐immobilizing hemoglobin (Hb) with platinum nanoparticles enhanced poly(chloromethyl thiirane) cross‐linked chitosan (CCCS‐PNs) hybrid film. CCCS could provide a biocompatible microenvironment for Hb and PNs could accelerate the electron transfer between Hb and the electrode. Spectroscopic analysis indicated that the immobilized Hb could maintain its native structure in the CCCS‐PNs hybrid film. Entrapped Hb exhibited direct electrochemistry for its heme Fe(III)/Fe(II) redox couples at ?0.396 V in the CCCS‐PNs hybrid film, as well as peroxidase‐like activity to the reduction of hydrogen peroxide without the aid of an electron mediator.     

Effects of Chemical Structures Interacting with Amine Oxidases on Glucose,Lipid and Hydrogen Peroxide Handling by Human Adipocytes

Benzylamine is a natural molecule present in food and edible plants, capable of activating hexose uptake and inhibiting lipolysis in human fat cells. These effects are dependent on its oxidation by amine oxidases present in adipocytes, and on the subsequent hydrogen peroxide production, known to exhibit insulin-like actions. Virtually, other substrates interacting with such hydrogen peroxide-releasing enzymes potentially can modulate lipid accumulation in adipose tissue. Inhibition of such enzymes has also been reported to influence lipid deposition. We have therefore studied in human adipocytes the lipolytic and lipogenic activities of pharmacological entities designed to interact with amine oxidases highly expressed in this cell type: the semicarbazide-sensitive amine oxidase (SSAO also known as PrAO or VAP-1) and the monoamine oxidases (MAO). The results showed that SZV-2016 and SZV-2017 behaved as better substrates than benzylamine, releasing hydrogen peroxide once oxidized, and reproduced or even exceeded its insulin-like metabolic effects in fat cells. Additionally, several novel SSAO inhibitors, such as SZV-2007 and SZV-1398, have been evidenced and shown to inhibit benzylamine metabolic actions. Taken as a whole, our findings reinforce the list of molecules that influence the regulation of triacylglycerol assembly/breakdown, at least in vitro in human adipocytes. The novel compounds deserve deeper investigation of their mechanisms of interaction with SSAO or MAO, and constitute potential candidates for therapeutic use in obesity and diabetes.     

Influence of High Voltage Needle Electrode Material on Hydrogen Peroxide Formation and Electrode Erosion in a Hybrid Gas–Liquid Series Electrical Discharge Reactor

Formation rates of hydrogen peroxide and electrode erosion rates for a range of different electrode materials were determined in a gas–liquid pulsed electrical discharge reactor with a high voltage electrode needle in the liquid and a ground electrode suspended in the gas over the liquid. It was found that the H₂O₂ formation rates and efficiencies did not depend on the electrode material. Electrode erosion from lowest to highest followed the series: nickel chromium, thoriated tungsten, diamond-coated tungsten, stainless steel, tungsten carbide and tungsten copper alloy. Smooth crater-like morphology was found for nickel chromium, titanium and tungsten carbide and a much finer surface structure with small protrusions for the tungsten, tungsten copper and the copper. Doubling the electrode diameter lead to an increase in the H₂O₂ formation per eroded length by a factor of three but it also decreased the energy efficiency yield of H₂O₂ by more than 20%.     

Controllable Release and High‐Efficiency Collection of Hydrogen Peroxide: Application on the Quantitative Investigation of Biomolecule Oxidation Induced by Reactive Oxygen Species

Hydrogen peroxide and hydroxyl radical, both important members of the reactive oxygen species (ROS) family, can cause serious oxidative damages in biological systems. In order to proclaim and prevent oxidation stress, researches on the biomolecule oxidation induced by H₂O₂ or OH^. are in crucial need. However, due to the high reactivity of ROS, traditional methods are difficult to achieve the in situ quantitative investigations on those reactions involving ROS. In this work, using scanning electrochemical microscopy technique (SECM) in a tip generation‐substrate collection mode (TG‐SC), the controllable release and the high‐efficiency collection of electrogenerated H₂O₂ were achieved. Compared to ex situ fluorescence method, SECM improved the collection efficiency approximately two times larger. Based on it, SECM combined with surface plasmon resonance (SPR) was employed to in situ monitor the protein oxidation (taking Cu₁₂⁺? MT as a model) induced by H₂O₂. OH^., which was generated from the interaction between H₂O₂ and Cu₁₂⁺? MT, can attack the peptide chain and induced the unrepairable protein oxidation damage. The whole process was quantitatively characterized by SPR, and the linear relationship between SPR dip shift and the amounts of released H₂O₂ was successfully built. Our work proves that the combined SECM‐SPR technique can realize the in situ quantitative determinations of the biomolecule oxidation induced by ROS, which affords an avenue for further elucidation on the mechanisms of oxidation stress in organisms.     

Effects of Hydrogen Peroxide on In Vitro Cultures of Tea (Camellia sinensis L.) Grown in the Dark and in the Light: Morphology,Content of Malondialdehyde,and Accumulation of Various Polyphenols

Tea plants (Camellia sinensis L.) are phenol-accumulating crops that are widely used for public health. The healing effect of tea leaf products is due to the biosynthesis of such phenolic compounds (PCs) as flavans, which have P-vitamin capillary-strengthening activity. Due to their limited habitat and the value of their specialized metabolites of a phenolic nature, a promising approach is to establish in vitro cultures from them that retain the ability to form PCs, which is characteristic of ex vivo tea plants. The aim of this study was to investigate the effect of exogenic H₂O₂ (0.01 mM; 0.1 mM; 1 mM) on the growth, morphology, degree of stress response, and accumulation of various phenolic compounds in tea plant callus cultures of different ages (24 or 36 days) grown under different cultivation conditions (darkness or light). According to the results obtained, the H₂O₂ effect on tea callus cultures of different ages did not cause changes in their morphophysiological characteristics, both after 2 h of exposure (rapid response of callus culture, RRCC) and after 48 h (delayed response of callus culture, DRCC). The determination of the malondialdehyde (MDA) content, which serves as an indicator of changes in the level of lipid peroxidation (LPO) and the presence of stress responses in plant cells, indicated either its maintenance at the control level, a decrease, or an increase. All these effects depended on the growth conditions of the tea callus cultures (darkness or light), their age, the duration of exposure (rapid or delayed response), and the H₂O₂ concentration. Similar trends were noted for the total content of PCs as well as the amount of flavans, proanthocyanidins (soluble and insoluble forms), and lignin. The plant cell responses reflected changes in its adaptation programs, when specialized metabolites act as a target for the action of H₂O₂, thereby contributing to an increase in their resistance.     

十二醇聚氧乙烯醚的表面性能及在水悬浮剂中的应用

探讨了十二醇聚氧乙烯醚(AEO)的EO链长对其临界胶束浓度(cmc)、表面张力(γcmc)、胶束生成自由能(ΔGm)、分子面积(Acmc)和亲水亲油平衡(HLB)值等表面性能的影响;同时研究了不同EO链长的AEO对质量分数25%代森锰锌水悬浮剂(SC)的流变性能[黏度、储能模量(G’)、流动点时的应变(γflow)、触变性]和物理贮存性能(热贮前悬浮率、热贮后悬浮率和倾倒性)的影响.结果发现,AEO的cmc,γcmc,ΔGm,Acmc和HLB值随着EO链长的增加而增大;AEO能够明显改善代森锰锌SC的黏度,以AEO-9所制备的SC黏度最小,且AEO的EO链长越长,所对应的SC结构恢复越慢,恢复慢的样品其倾倒残留率过高;G’和γflow能反映SC内部结构变化,可作为评价农药SC物理稳定性流变学指标.     

Substituents Effects to the Electrochemical,and In Situ Spectroelectrochemical Behavior of Metallophthalocyanines: Electrocatalytic Application for Hydrogen Evolution Reaction

This study describes the effects of the number of fluoro substituents to the electrochemical, in situ spectroelectrochemical, and electrocatalytic activities of metallophthalocyanines for the hydrogen evolution reaction. Tuning of the number of fluoro groups shifts the redox processes and affects the aggregation tendencies of the complexes. An in situ electrocolorimetric method was applied to investigate the color of the electrogenerated anionic and cationic forms of the complexes. Cobalt phthalocyanines incorporated into Nafion film on a glassy carbon electrode decreases the overpotential of the working electrode for H⁺ reduction. The number and position of the electron withdrawing substituents and nature of the metal center change the electrocatalytic activities for the hydrogen evolution reaction in aqueous solutions.     

Amperometric Hydrogen Peroxide Biosensor Based on the Immobilization of Horseradish Peroxidase (HRP) on the Layer‐by‐Layer Assembly Films of Gold Colloidal Nanoparticles and Toluidine Blue

The precursor film was first formed on the Au electrode surface based on the self‐assembly of L ‐cysteine and the adsorption of gold colloidal nanoparticles (nano‐Au). Layer‐by‐layer (LBL) assembly films of toluidine blue (TB) and nano‐Au were fabricated by alternately immersing the electrode with precursor film into the solution of toluidine blue and gold colloid. Cyclic voltammetry (CV) and quartz crystal microbalance (QCM) were adopted to monitor the regular growth of {TB/Au} bilayer films. The successful assembly of {TB/Au}_n films brings a new strategy for electrochemical devices to construct layer‐by‐layer assembly films of nanomaterials and low molecular weight materials. In this article, {TB/Au}_n films were used as model films to fabricate a mediated H₂O₂ biosensor based on horseradish peroxidase, which responded rapidly to H₂O₂ in the linear range from 1.5×10^?7 mol/L to 8.6×10^?3 mol/L with a detection limit of 7.0×10^?8 mol/L. Morphologies of the final assembly films were characterized with scanning probe microscopy (SPM).