Detection Of Hydroxyl Radicals Research Articles

A rapid and sensitive method for hydroxyl radical detection on a microfluidic chip using an N-doped porous carbon nanofiber modified pencil graphite electrode.

Hydroxyl radicals (˙OH) play an important role in human diseases. Traditional detection methods are time consuming and require expensive instruments. Here, we present a simple and sensitive method for the detection of hydroxyl radicals on a microfluidic chip using an electrochemical technique. Aniline monomer is electrochemically polymerized on the surface of a pencil graphite electrode and carbonized at 800 °C. The resulting N-doped porous carbon nanofiber-modified pencil graphite electrode is embedded into a microfluidic chip directly as a working electrode. 4-Hydroxybenzoic acid (4-HBA) is selected as the trapping agent owing to its unique 3,4-DHBA product and high trapping efficiency. A low detection limit of 1.0 × 10(-6) M is achieved on the microfluidic chip. As a demonstration, the microfluidic chip is successfully utilized for the detection of ˙OH in cigarette smoke. The strong π-π stacking and hydrophobic interactions between the nitrogen-doped carbon materials and the pencil graphite make the modified electrode well-suited for the microfluidic chip.

Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions

The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less.

Detection of hydroxyl radical in isolated Goto-Kakizaki (GK) rat arteries by trapping with 4-hydroxybenzoic acid

Detection of hydroxyl radical in isolated Goto-Kakizaki (GK) rat arteries by trapping with 4-hydroxybenzoic acid

Fluorescence and HPLC Detection of Hydroxyl Radical by a Rhodamine-Nitroxide Probe and its Application in Cell Imaging

A rhodamine nitroxide probe was designed to detect the hydroxyl radical (·OH), which presented high selectivity for ·OH over other reactive oxygen species (ROS) and linear fluorescence response to ·OH produced by Fenton reaction. The product was detected by HPLC-MS, indicating that the main product of the reaction was O-methylhydroxylamine and the product peak areas measured by HPLC-UV/vis and HPLC-FLD both enhanced proportionally with the increase of ·OH concentration. The application of the probe in biological system was explored to trace the production of ·OH in cells under oxidative stress condition induced by rotenone which can inhibit the mitochondria respiratory chain complex I and we found that appropriate rotenone may induce the normal human liver cells (L02) and human hepatoma cells (HepG2) to produce ·OH at different degrees.

In situ measurement of superoxide and hydroxyl radicals by frequency mixing detection technique

Frequency mixing magnetic detection (FMMD) was used to detect superoxide from hypoxanthine and xanthine reaction and to detect hydroxyl radical from the Fenton reaction. FMMD was also applied to measure the reactive oxygen species (ROS) level released from microglial cells. We could assess the formation and extinction of the free radicals without a spin trap reagent. The FMMD signal amplitude scaled with the concentration of the radicals. It was verified that no signals are obtained from the substrates and reagents. Based on the observations and on previous research, we suggest that the FMMD signals originate from superoxide and hydroxyl radicals, indicating that FMMD can be used to detect O-centered radicals. Subsequent analysis of free radicals generated from living microglial cells showed that there were significant differences between the activated microglial cells and resting ones. The results of this research are promising regarding the applications of FMMD for in situ measurement of free radicals from various sources, including the cell.

The quantitative detection of HO˙ generated in a high temperature H2O2 bleaching system with a novel fluorescent probe benzenepentacarboxylic acid

A novel fluorescent probe, benzenepentacarboxylic acid (BA), was developed for the quantitative detection of hydroxyl radicals (HO˙) in a simulated hydrogen peroxide (H2O2) bleaching system. Compared to terephthalic acid (TA), a commonly-used fluorescent probe of HO˙ with four possible reaction sites, the present probe has only one reaction site for HO˙ addition that results in the formation of a single fluorescent product, hydroxybenzenepentacarboxylic acid (HBA). The generation of the single pure fluorescent product by BA, rather than mixtures by TA, made the present probe more sensitive, accurate and reproducible in the quantitative detection of HO˙. Based on the working curve obtained from the fluorescence intensity and HBA concentration, a fluorimetric method for the quantitative detection of HO˙ was developed. The present probe BA was successfully used for the quantitative detection of HO˙ under alkaline and high temperature (80 °C) conditions, in a simulated H2O2 bleaching system. The method was highly sensitive, reproducible, and applicable in a wide temperature range of 20–98 °C. The present novel fluorescent probe will be potential tool for evaluating the generation and function kinetics of HO˙ generated in biological and environmental fields.

Iron terephthalate metal–organic framework: Revealing the effective activation of hydrogen peroxide for the degradation of organic dye under visible light irradiation

Metal–organic frameworks (MOFs), a new class of porous crystalline materials, have attracted great interest as a promising candidate for sustainable energy and environmental remediation. In this study, we demonstrate that an iron terephthalate metal–organic framework MIL-53(Fe) synthesized by a facile solvothermal reaction was capable of activating hydrogen peroxide (H2O2) to achieve high efficiency in photocatalytic process. It could completely decompose the 10mgL−1 Rhodamine B (RhB) in the presence of a certain amount of H2O2 under visible light irradiation within 50min. The catalytic activities were found to be strongly affected by the various operating parameters, such as solution pH, initial dye concentration, and H2O2 dosage. The activation effects of MIL-53(Fe) were investigated through the detection of hydroxyl radicals (OH) and transient photocurrent responses, which revealed that the H2O2 behaved in two ways during the catalytic process: (i) it could be catalytically decomposed by MIL(Fe)-53 to produce OH radicals through the Fenton-like reaction; (ii) it could capture the photogenerated electrons in the conduction band of excited MIL-53(Fe) to form OH radicals under visible light irradiation. The ability of such iron-based MOFs to activate H2O2 may enable rational design of advanced MOF-based catalysts for environmental remediation.

Intestinal NF-E2-related factor-2 expression and antioxidant activity changes in rats undergoing orthotopic liver autotransplantation

Liver transplantation is known to trigger intestinal injuries. Oxidative damage that is induced by reactive oxygen species (ROS) plays a crucial role in ischemia-reperfusion injuries. NF-E2-related factor-2 (Nrf2) and its modulated antioxidant enzymes form the critical endogenous antioxidant system to scavenge ROS. The present study investigated the dynamic changes of intestinal ROS levels, Nrf2 expression and antioxidant enzyme activity following orthotopic liver autotransplantation (OLAT). Sprague-Dawley rats were randomly divided into five groups consisting of one sham group and four groups with rats that underwent OLAT and were evaluated following 4, 8, 16 and 24 h, respectively. The intestinal specimens were collected for histopathological examination and the detection of hydrogen peroxide (H2O2), hydroxyl radical (•OH), malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels and the expression of Nrf2. The present study demonstrated that OLAT resulted in severe intestinal injury, which manifested as a significant change in the intestine pathological scores as early as 4 h and peaking at 8 h post-treatment. Oxidative stress was also revealed by the increase of the H2O2, •OH and MDA levels. Significant decreases were observed in the activity of SOD and CAT and a dramatic decrease occurred in the levels of GSH at 4 and 8 h post-treatment. All the parameters were restored gradually at 16 and 24 h post-treatment. The expression of Nrf2 in the intestinal tissues increased significantly at 4, 16 and 24 h following OLAT. The present study shows that an imbalance between oxidants and antioxidants contributes to intestinal oxidative injury, and that the upregulation of Nrf2 is not sufficient to withstand intestinal oxidative injury following OLAT.

Indirect Determination of Hydroxyl Radicals in Fine Particle Mist Generated from an Odor Control Technology via HPLC

Size distribution analysis of microsized water particle mist generated from an odor control technology showed the majority of particles to be in the low micron range. The indirect detection and determination of hydroxyl radicals generated by their reaction with benzene to produce phenol was performed through UV-Vis spectrophotometry (UV-Vis) and high performance liquid chromatography (HPLC). These techniques gave verification of the presence of hydroxyl radical species in the water samples collected via this odor control technology. This technology is currently being utilized at various wastewater treatment plants.

γ-Fe2O3 nanoparticles: An easily recoverable effective photo-catalyst for the degradation of rose bengal and methylene blue dyes in the waste-water treatment plant

γ-Fe2O3 nanoparticles (NPs) were synthesized from a single-source precursor complex [Fe3O(C6H5COO)6(H2O)3]NO3 by a simple thermal decomposition process and have been characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopic techniques. The NPs were highly pure and well crystallized having hexagonal morphology with an average particle size of 35nm. The prepared γ-Fe2O3 (maghemite) NPs show effective photo-catalytic activity toward the degradation of rose bengal (RB) and methylene blue (MB) dyes under visible light irradiation and can easily be recoverable in the presence of magnetic field for successive re-uses. The possible photo-catalytic decomposition mechanism is discussed through the detection of hydroxyl radical (OH) by terephthalic acid photo-luminescence probing technique.

Enhanced Sonocatalytic Activity, Kinetic Analysis, and Sonocatalytic Mechanism for Silver Phosphate by Br Modifying with Ionic Liquids

The Ag3PO4 and Ag3PO4 sonocatalysts with surface enrichment of Br− anions (Br–Ag3PO4) were synthesized using a facile precipitate process. Various analysis, including X‐ray diffraction, transmission electron microscopy, scanning electron microscope, Brunauer–Emmett–Teller, photoluminescence (PL) spectra, and UV–Vis absorption spectra were carried out to investigate the property and structure. The effect of a variety of changing conditions on ultrasonic degradation of organic dye has been investigated. Both of them exhibited obvious activity for sonocatalytic degradation of organic dyes. However, Br–Ag3PO4 sonocatalysts showed much higher activity than that of Ag3PO4. By XRD analysis, the Br− anions of the surface of Ag3PO4 has been transformed into AgBr in the preparation process. The high activity could be attributed to AgBr for modifying Ag3PO4. By detecting hydroxyl radicals (·OH) in the reactive solution, we found that AgBr on the surface of Ag3PO4 can help to produce a lot of additional ·OH radicals. These ·OH radicals may be significant reason to improve Ag3PO4 activity, which further proved the ·OH radical mechanism of Ag3PO4 degradation of dyes under ultrasonic radiation. In addition, kinetic analysis and sonocatalytic mechanism were discussed in detail.

Basis for Sensitive and Selective Time-Delayed Luminescence Detection of Hydroxyl Radical by Lanthanide Complexes

Molecular probes for the detection of hydroxyl radical (HO•) by time-delayed luminescence spectroscopy directly in water at neutral pH with high sensitivity and selectivity are presented. The bimolecular probes consist of a lanthanide complex with open coordination sites and a reactive pre-antenna composed of an aromatic acid or amide; the latter binds to and sensitizes terbium emission upon hydroxylation by HO•. These probes exhibit long luminescence lifetimes compatible with time-delayed measurements that remove interfering background fluorescence from the sample. Six different reactive pre-antenna (benzoate, benzamide, isophthalate, isophthalamide, trimesate, and trimesamide) and two different terbium complexes [Tb-(1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid)) (Tb-DO3A) and Tb-(1,4,7,10-tetraazacyclododecane-1,7-bis(acetic acid)) (Tb-DO2A)] were evaluated. Of these the trimesamide/Tb-DO3A system enables the most sensitive detection of HO• with an about 1000-fold increase in metal-centered time-delayed emission upon hydroxylation of the pre-antenna to 2-hydroxytrimesamide. Excellent selectivity for both the trimesamide/Tb-DO3A and trimesate/Tb-DO3A systems over other reactive oxygen and nitrogen species are observed. Notably, the increase in metal-centered luminescence intensity is not associated with a decrease in the hydration number (q) of Tb-DO3A, suggesting that the antenna is interacting with the lanthanide via a second sphere coordination environment or that coordination by the antenna occurs by displacement of one or more of the carboxylate arms of DO3A. Formation of a weak ternary complex Tb-DO3A•hydroxytrimesamide was confirmed by temperature-dependent titration and a decrease in K(app) with increasing temperature.

Role of Autofluorescence in Flow Cytometric Analysis of Escherichia coli Treated with Bactericidal Antibiotics

Bactericidal antibiotics kill by different mechanisms as a result of a specific interaction with their cellular targets. Over the past few years, alternative explanations for cidality have been proposed based on a postulated common pathway, depending on the intracellular production of reactive oxygen species. Detection of hydroxyl radicals relies on staining with specific fluorescent dyes that can penetrate the cell and are detected using flow cytometry. Flow cytometry has become an important tool in microbiology to study characteristics of individual cells within large heterogeneous cellular populations. We show here that Escherichia coli treated with different bactericidal antibiotics exhibits increased autofluorescence when analyzed by flow cytometry. We present evidence suggesting that this change in autofluorescence is caused by altered cell morphology upon antibiotic treatment. Consistent with this view, mutant cells that fail to elongate upon norfloxacin treatment show no increased auto-fluorescence response. Finally, we present data demonstrating that changes in autofluorescence can impact the results with fluorescent probes when using flow cytometry and confound the findings obtained with specific dyes. In summary, recent findings that correlate the exposure to cidal antibiotics with the production of reactive oxygen species need to be reconsidered in light of such changes in autofluorescence. Conclusive evidence for an increase of hydroxyl radicals after treatment with such drugs is still missing.

Co3O4 nanoparticles as an efficient catalase mimic: Properties, mechanism and its electrocatalytic sensing application for hydrogen peroxide

Nanomaterial-based enzyme mimics have recently attracted considerable interest due to their easy preparation, low cost, high stability and so on. Herein Co3O4 nanoparticles (NPs) were used as a catalase mimic, catalyzing the decomposition of hydrogen peroxide to oxygen. The catalytic activity of Co3O4 NPs increased dramatically by adjusting the pH from acid to neutral and alkaline conditions. The catalytic activities and the mechanisms were investigated using the procedures of thermodynamics, steady-state kinetics and hydroxyl radical detection. The activation energy of Co3O4 NPs was determined to be 43.3kJmol−1 which was similar to 42.8kJmol−1 of catalase. The catalytic behaviour of Co3O4 NPs showed a typical Michaelis–Menten kinetics and good affinity to H2O2. The turnover number and specificity constant of Co3O4 NPs were very close to those of catalase. Based on the above results, Co3O4 NPs were an efficient catalase mimic. A catalytic mechanism was proposed where hydroxyl radicals took part in the catalytic recycles. Co3O4 NPs had better stability than natural catalase when they were exposed to solutions with different pH values and temperatures. As an efficient and stable catalase mimic, Co3O4 NPs were used as the amperometric sensor for the detection of hydrogen peroxide.

Capillary electrophoretic analysis of hydroxyl radicals produced by respiring mitochondria

Here, we report the use of a capillary electrophoretic method with laser-induced fluorescence detection to evaluate hydroxyl radicals produced by respiring mitochondria. The probe, hydroxyphenylfluorescein (HPF), is separated from the product, fluorescein, in under 5 min with zeptomole and attomole limits of detection for fluorescein and HPF, respectively. Purification of the probe with a C-18 SPE column is necessary to reduce the fluorescein impurity in the probe stock solution from 0.4% to less than 0.001%. HPF was responsive to hydroxyl radicals produced by isolated mitochondria from L6 cells, and this signal was blunted when DMSO was added to scavenge hydroxyl radicals and when carbonyl cyanide m-chlorophenylhydrazone was added to depolarize the mitochondria. The method was used to compare hydroxyl radical levels in mitochondria isolated from brown adipose tissue of lean and obese mice. Mitochondria from obese mice produced significantly more hydroxyl radicals than those from lean mice.

Potentiometric sensing of nuclease activities and oxidative damage of single-stranded DNA using a polycation-sensitive membrane electrode

A simple, general and label-free potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed potentiometrically with detection limits of 2.7×10−4U/µL for S1 nuclease, and of 3.9×10−4U/µL for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2×10−4U/µL for S1 nuclease, and of 4.5×10−4U/µL for DNase I. Moreover, the proposed potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities.

Sensitive electrochemical detection of hydroxyl radical based on MBs–DNA–AgNPs nanocomposite

A sensitive electrochemical method for the detection of hydroxyl radical (OH) was successfully developed based on magnetic beads (MBs)–DNA–Ag nanoparticles (AgNPs) (MBs–DNA–AgNPs) nanocomposite. MBs were utilized for bioseparation and AgNPs as signal indicator. When OH broke the DNA strands, AgNPs were detached from the surface of the MBs–DNA–AgNPs nanocomposite. Magnetic particles could be easily removed from the solution and the detached AgNPs were collected. Therefore, the anodic stripping voltammetry (ASV) signal of dissolved silver on glassy carbon (GC) electrode depended on the amounts of OH. The results show that the ASV signal linearly increases with the increase of the concentration of OH in the range of 0.05–4μM, and the detection limit is as low as 10nM, which is much lower than the detection limit obtained on the recently developed electrochemical and photoelectrochemical methods. In addition, the developed method has potential application in the screening of antioxidants.

Detection of hydroxyl radicals during regeneration of granular activated carbon in dielectric barrier discharge plasma system

To understand the reactions taking place in the dielectric barrier discharge (DBD) plasma system of activated carbon regeneration, the determination of active species is necessary. A method based on High Performance Liquid Chromatography with radical trapping by salicylic acid, has been developed to measure hydroxyl radical (•OH) in the DBD plasma reactor. The effects of applied voltage, treatment time, and gas flow rate and atmosphere were investigated. Experimental results indicated that increasing voltage, treatment time and air flow rate could enhance the formation of •OH. Oxygen atmosphere and a suitable GAC water content were contributed to •OH generation. The results give an insight into plasma chemical processes, and can be helpful to optimize the design and application for the plasma system.

Rhodamine cyclic hydrazide as a fluorescent probe for the detection of hydroxyl radicals

A new rhodamine fluorescent probe for monitoring ˙OH has been developed based on the oxidative C-H abstraction reaction of rhodamine cyclic hydrazide. The probe exhibits excellent selectivity for ˙OH with virtually no interference by other ROS/RNS species. Fluorescent imaging of A549 and RAW264.7 cells is also successfully demonstrated to detect intracellular ˙OH in live cells.

Sensitive electrochemical detection of hydroxyl radical with biobarcode amplification

By using biobarcode nanoparticles, we have successfully constructed a DNA-based biosensor for amplified electrochemical detection of hydroxyl radical (OH). Thiolated DNA1 (SH-DNA1) was firstly immobilized on the planar gold (Au) electrode. OH generated from Fenton reaction could induce serious oxidative damage of the DNA layer adsorbed on the electrode surface, which was monitored by an intercalating probe, methylene blue (MB). In order to enhance the sensitivity of the biosensor, DNA2-functionalized Au nanoparticles (DNA2-AuNPs) were used to amplify the response signal. The developed DNA-based biosensor could detect OH quantitatively with wide linear range up to 10mM and low detection limit of 3μM, and exhibited satisfactory selectivity. On the other hand, this electrochemical biosensor could have potential application in the evaluation of antioxidant capacity.