Detection Of Hydroxyl Radicals Research Articles

Marine Cyclic Dipeptide Cyclo (L-Leu-L-Pro) Protects Normal Breast Epithelial Cells from tBHP-induced Oxidative Damage by Targeting CD151

Background: Oxidative stress plays a key role in breast carcinogenesis. Cyclo (L-Leu-L-Pro) (CLP) is a homodetic cyclic dipeptide with 2,5-diketopiperazine scaffold isolated from marine actinobacteria. This study aimed to evaluate the protective activity of CLP and linear - (L-Leu-L-Pro) (LP) from tert-butyl hydroperoxide (tBHP)-induced damage using normal breast epithelial cell line model (MCF-12A). Methods: The cytoprotective activity was evaluated by detecting the changes in intracellular ROS, mitochondrial superoxide, hydroxyl radical, hydrogen peroxide, and lipid peroxidation detection assays as well as cytotoxic assays of MTT, LDH assays and phase contrast microscopy. Genoprotective activity was evaluated by (Apurinic/Apyrimidinic) AP site, alkaline Comet, and 8-hydroxy-2-deoxyguanosine assays. Results: The marine cyclic peptide, CLP, significantly protected MCF-12A cells by scavenging tBHP induced intracellular ROS such as super oxide, hydroxyl radicals and hydrogen peroxide, and by reducing the cytotoxicity and genotoxicity effect compared to LP. Moreover, the results showed that CD151 gene silencing by shRNA significantly reduced the overexpression of CD151, tBHP-induced ROS generation, cytotoxicity and genotoxicity in MCF-12A cells. The overexpression of CD151 caused increased levels of cytochrome P450, but was reduced following the application of CD151shRNA and CLP which led to elevated levels of intracellular ROS. Conclusion: In the present study we noticed that CD151 gene silencing by shRNA and treatment with CLP have similar effects on reducing the intracellular ROS. This study uncovers the protective activity of CLP against a CD151-mediated oxidative stress-induced cellular damage. Our observations suggest that the anti-stress and anti-inflammation properties of CLP might have implications in cancer and are worth testing in cancer cell lines and tumor cells.

An eco-friendly approach to low-temperature and near-neutral bleaching of cotton knitted fabrics using glycerol triacetate as an activator

Near-neutral bleaching of cotton fabrics at low temperature is of great importance for saving energy and ecological friendliness in textile industry. In this work, glycerol triacetate (GT) was investigated as an activator of hydrogen peroxide (H2O2) for low temperature bleaching of cotton knitted fabrics, and satisfactory whiteness was obtained. The bleaching properties of H2O2/GT system for cotton was assessed by the CIE whiteness index (WI), H2O2 decomposition rate, concentration of generated peracetic acid and bursting strength. Possible factors affecting the properties of cotton bleached by H2O2/GT bleaching system were discussed in detail. At 60 °C, adding only 10 mmol/L GT to the hydrogen peroxide solution (60 mmol/L) to bleach cotton knitted fabrics for 60 min, the WI was significantly increased from 52.09 to 68.92. By using benzenepentacarboxylic acid as a fluorescent probe for hydroxyl radical (HO·) detection, it was found that GT could clearly promote HO· generation and its concentration closely related to the WI of cotton fabric. Furthermore, the bleaching mechanism of H2O2/GT system was proposed by exploring the relationship between WI and HO· concentration. GT as a bleach activator has more economical benefits and better water solubility than tetraacetylethylenediamine. The H2O2/GT system may provide a cost-effective and environmentally friendly bleaching approach of cotton as alternative to conventional alkaline high-temperature bleaching.

A time-dependent density functional theory study of a fluorescent probe to detect hydroxyl radicals: Inhibiting the twisted intramolecular charge-transfer process

Due to the relevance to excited-state processes, sensing mechanisms of fluorescent probes were difficult to study directly by experimental methods. This work investigated theoretically the sensing mechanism of a reported bifunctional fluorescent probe to detect intracellular hydroxyl radicals and their environmental viscosity (J. Am. Chem. Soc. 2019, 141, 18301). Calculations were performed at the B3P86/TZVP/SMD level using density functional theory and time-dependent density functional theory. The transition from the ground-state (S0) to the first singlet excited state (S1) was calculated to have the largest oscillation strength for the probe. The wavelength that corresponded to the S0-S1 vertical excitation energy (427 nm) agreed well with the maximum absorption band at 400 nm in the ultraviolet–visible spectra. Theoretical results showed that the probe had two distinct geometries in the S0 and S1 states, respectively. This difference was caused by the different distributions of frontier molecular orbitals that were involved in the S0-S1 transition and corresponds to a twisted intramolecular charge transfer. The S1-state potential energy curve of the probe molecule confirmed that the twisted intramolecular charge transfer could proceed spontaneously with a potential barrier of only 12.20 kJ/mol. This result provided an irradiative approach for the probe molecule to dissipate the S1-state energy, which explained its fluorescence quenching. In contrast, the hydroxyl oxidation reaction changed frontier molecular orbitals of the probe molecule, which made its S1 state a local S1 state with a strong fluorescence emission. Precisely due to the mechanism, the hydroxyl radicals could be detected by changes in the fluorescence signal of the probe molecule.

Photo‐Induced Self‐Cleaning and Wettability in TiO2 Nanocolumn Arrays Obtained by Glancing‐Angle Deposition with Sputtering

AbstractIn this work, the preparation of regular nanosized columnar structures of titanium dioxide by means of glancing angle deposition with magnetron sputtering (MS‐GLAD) followed by thermal annealing is reported. MS‐GLAD gives rise to metallic titanium columnar structures with regular width and length that after thermal treatment are fully oxidized to form TiO2 nanocolumns that maintain the morphological features of the original metallic ones. Further functionalization with gold by means of multiple ion cluster source results in well‐dispersed Au nanoparticles across the nanocolumns’ surface with a narrow size distribution centered at ca. 8.5 nm. The obtained nanostructures show photocatalytic self‐cleaning activity as shown by the elimination of an organic layer deposited on their surface and the detection of hydroxyl radicals. Photoelectrochemical measurements show a better charge separation at the Au/TiO2 interface. In addition, wettability studies show that the degree of hydrophobicity of the surface is increased by the presence of nanocolumns, both in the dark and under UV illumination. This behavior is not modified by the presence of Au nanoparticles on the surface. The obtained results open up interesting implications in the tunability of the properties of nanostructured thin films for this kind of photo‐activated application.

A microfluidic dosimetry cell to irradiate solutions with poorly penetrating radiations: a step towards online dosimetry for synchrotron beamlines.

Synchrotron radiation can induce sample damage, whether intended or not. In the case of sensitive samples, such as biological ones, modifications can be significant. To understand and predict the effects due to exposure, it is necessary to know the ionizing radiation dose deposited in the sample. In the case of aqueous samples, deleterious effects are mostly induced by the production of reactive oxygen species via water radiolysis. These species are therefore good indicators of the dose. Here the application of a microfluidic cell specifically optimized for low penetrating soft X-ray radiation is reported. Sodium benzoate was used as a fluorescent dosimeter thanks to its specific detection of hydroxyl radicals, a radiolytic product of water. Measurements at 1.28 keV led to the determination of a hydroxyl production yield, G(HO.), of 0.025 ± 0.004 µmol J-1. This result is in agreement with the literature and confirms the high linear energy transfer behavior of soft X-rays. An analysis of the important parameters of the microfluidic dosimetry cell, as well as their influences over dosimetry, is also reported.

Dual-emission copper nanoclusters-based ratiometric fluorescent probe for intracellular detection of hydroxyl and superoxide anion species.

A fluorescent nanoprobe based on copper nanoclusters (CuNCs) has been developed for ratiometric detection of hydroxyl radicals (•OH) and superoxide anion radicals (O2•-). Two differently luminescent CuNCs, namely cyan-emissive poly(methacrylic acid)-protected copper nanoclusters (PCuNCs) and orange-emissive bovine serum albumin-protected CuNCs (BCuNCs), were conjugated to obtain a hybrid, dual-emission nanoprobe (PCuNCs-BCuNCs) with the corresponding peaks at 445nm and 652nm at an excitation wavelength of 360nm. In particular, the fluorescence peak at 445nm gradually enhanced with the incremental addition of •OH and O2•-. However, the fluorescence emission at 652nm was greatly quenched in the presence of •OH, while in case of O2•-, the fluorescence intensity remained constant. The differential response of the PCuNCs-BCuNCs towards •OH and O2•- formed the basis of ratiometric detection. Under optimal conditions, the PCuNCs-BCuNCs exhibited good sensitivity and linearity towards •OH and O2•- with limits of detection of 0.15μM and 1.8μM, respectively. Moreover, the nanoprobe exhibited high selectivity for •OH and O2•- over other potential ROS interferences. Besides, PCuNCs-BCuNCs were eventually applied for qualitative and quantitative ratiometric assessment of intracellular •OH and O2•- in L-132 cells. Therefore, this strategy unveils a new potential for copper nanocluster-based sensing of ROS.

2',7'-dichlorofluorescin-based analysis of Fenton chemistry reveals auto-amplification of probe fluorescence and albumin as catalyst for the detection of hydrogen peroxide.

Fluorophore 2',7'-dichlorofluorescin (DCF) is the most frequently used probe for measuring oxidative stress in cells, but many aspects of DCF remain to be revealed. Here, DCF was used to study the Fenton reaction in detail, which confirmed that in a cell-free system, the hydroxyl radical was easily measured by DCF, accompanied by the consumption of H2O2 and the conversion of ferrous iron into ferric iron. DCF fluorescence was more specific for hydroxyl radicals than the measurement of thiobarbituric acid (TBA)-reactive 2-deoxy-D-ribose degradation products, which also detected H2O2. As expected, hydroxyl radical-induced DCF fluorescence was inhibited by iron chelation, anti-oxidants, and hydroxyl radical scavengers and enhanced by low concentrations of ascorbate. Remarkably, due to DCF fluorescence auto-amplification, Fenton reaction-induced DCF fluorescence steadily increased in time even when all ferrous iron was oxidized. Surprisingly, the addition of bovine serum albumin rendered DCF sensitive to H2O2 as well. Within cells, DCF appeared not to react directly with H2O2 but indirect via the formation of hydroxyl radicals, since H2O2-induced cellular DCF fluorescence was fully abolished by iron chelation and hydroxyl radical scavenging. Iron chelation in H2O2-stimulated cells in which DCF fluorescence was already increasing did not abrogate further increases in fluorescence, suggesting DCF fluorescence auto-amplification in cells. Collectively, these data demonstrate that DCF is a very useful probe to detect hydroxyl radicals and hydrogen peroxide and to study Fenton chemistry, both in test tubes as well as in intact cells, and that fluorescence auto-amplification is an intrinsic property of DCF.

Synthesis of Dihydroquinolines as Scaffolds for Fluorescence Sensing of Hydroxyl Radical.

A mild synthetic method to prepare dihydroquinolines has been presented. These dihydroquinolines, for the first time, showed great potential for fluorescence detection of the important biorelevant hydroxyl radicals (•OH). Sensitive and selective •OH detection and intracellular organelle-targeted fluorescence imaging of •OH have been demonstrated by using one of the synthetic dihydroquinolines. Moreover, dihydroquinoline has also exhibited promising potential to construct advanced fluorescence probes for •OH with tunable photophysical properties.

Synergistic interaction of Z-scheme 2D/3D g-C3N4/BiOI heterojunction and porous PVDF membrane for greatly improving the photodegradation efficiency of tetracycline

Designing photocatalytic membranes with excellent photocatalytic and self-cleaning ability based on the synergistic effect between the crystal structure of membrane matrix and photocatalyst is highly desirable. Herein, Z-scheme 2D/3D g-C3N4/BiOI heterojunction blended in beta-phase polyvinylidene fluoride membrane (β-phase PVDF) was prepared via solvent crystallization and phase inversion technique. As expected, the designed g-C3N4/BiOI/β-phase PVDF photocatalytic membranes (CN/BI/β-phase PVDF PMs) achieved exceptional photocatalytic degradation efficiency for tetracycline (94.6%) as compared to the CN/BI heterojunction power (84.0%) and two other control membrane matrixes (CN/BI/PAN and CN/BI/CA PMs) within 120 min. Meanwhile, the dynamic cyclic degradation system of CN/BI/β-phase PVDF PMs was also investigated that reached to be 94.8% in 80 min. Besides, the CN/BI/β-phase PVDF PMs not only had outstanding self-cleaning activity and remarkable permeability (up to 30,688 L·m−2·h−1) but also had high stability and reusability even after five runs. Importantly, the hydroxyl radical detection and ESR analysis identified that the β-phase PVDF membrane could promote photoinduced carrier separation efficiency of 2D/3D g-C3N4/BiOI heterojunction. This work may open up a novel strategy for designing and constructing high-efficient photocatalytic membranes for water treatment.

Dynamic Detection of Endogenous Hydroxyl Radicals at Single-Cell Level with Individual Ag-Au Nanocages.

Hydroxyl radicals (•OH) are a type of short-lived radical which is the most aggressive reactive oxygen species due to its high reactivity to biomolecules. Dynamic measurement of •OH level in living cells is critical for understanding cell physiology and pathology. In this manuscript, we prepare individual Ag-Au@PEG/RGD nanocages for in situ determination of endogenous •OH at single-cell level, whose spectral shift rate correlate to the •OH concentration. The high-selective response to •OH relies on the specific oxidization of the conjugated PEG/RGD outside and the silver etching inside the nanocages that resulted in a significant LSPR signal and scattered color changes. The spectral red-shift rate of LSPR has a linear relationship with the logarithm of •OH concentration in range of 100 pM to 1 μM, suitable for the measurement of endogenous •OH. Thus, the individual nanocages were successfully used to monitor the dynamic intracellular •OH level of single tumor cells under oxidative stress. This strategy has great potential in promoting •OH mediated cell homeostasis and injury research.

Covalent organic frameworks functionalized carbon fiber paper for the capture and detection of hydroxyl radical in the atmosphere

Developing a fast, sensitive and convenient method for the detection of hydroxyl radicals (OH) in the atmosphere could help us know the precursor levels of atmospheric species and control air pollution. In this work, the carbon fiber paper (CFP) functionalizing with a kind of covalent organic frameworks (COFs), formed from 1,3,5-triformylphloroglucinol (Tp) and benzidine (BD) (COF(TpBD)), was firstly used a new platform for OH trapping and detection. The COF(TpBD) modified CFP was acted as a filter to impregnate salicylic acid (SA) and a detector to detect 2,5-dihydroxybenzoic acid (2,5-DHBA) which was produced from the reaction between the impregnated SA and OH in the atmosphere. This method provided a linearity for 2,5-DHBA from 5.0 × 10−14 mol/L 1.0 × 10−9 mol/L with a detection limit of 6.9 × 10−15 mol/L, which is corresponding to the amount of OH from 3.0 × 107 to 6.0 × 1011 molecules/cm3 with the detection limit of 4.1 × 106 molecules/cm3. This COF(TpBD)-CFP platform has been successfully applied for the detection of OH concentration under different conditions of Yangzhou when the sampling time was shortened to 30 min. This work has provided a new method for atmospheric OH detection with excellent sensitivity, simplicity, and high speed.

Detection of Hydroxyl Radicals Using Cerium Oxide/Graphene Oxide Composite on Prussian Blue.

A composite sensor consisting of two separate inorganic layers of Prussian blue (PB) and a composite of cerium oxide nanoparticles (CeNPs) and graphene oxide (GO), is tested with •OH radicals. The signals from the interaction between the composite layers and •OH radicals are characterized using cyclic voltammetry (CV). The degradation of PB in the presence of H2O2 and •OH radicals is observed and its impact on the sensor efficiency is investigated. The results show that the composite sensor differentiates between the solutions with and without •OH radicals by the increase of electrochemical redox current in the presence of •OH radicals. The redox response shows a linear relation with the concentration of •OH radicals where the limit of detection, LOD, is found at 60 µM (100 µM without the PB layer). When additional composite layers are applied on the composite sensor to prevent the degradation of PB layer, the PB layer is still observed to be degraded. Furthermore, the sensor conductivity is found to decrease with the additional layers of composite. Although the CeNP/GO/PB composite sensor demonstrates high sensitivity with •OH radicals at low concentrations, it can only be used once due to the degradation of PB.

Photoactivity under visible light of defective ZnO investigated by EPR spectroscopy and photoluminescence

The photochemical and photophysical properties of a defective zinc oxide prepared by precipitation have been investigated using mainly electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. As already reported in the literature the band gap of the oxide contains intra band gap states related to the presence of point defects (mainly cation vacancies) in the structure. The concentration and the energy levels of such defects, a fraction of them being paramagnetic, are the basis of a mechanisms of double and multiple excitations allowing visible photons with energy lower than the band gap value (hν <Eg) to promote electrons from the valence band (VB) to the conduction band (CB) similarly, though less efficiently, to what done by UV light with hν >Eg. Remarkably, some of the paramagnetic defects present in the bulk of the as prepared materials derive from excitation of VB electrons induced by ambient light illumination.The electron excitation from VB to CB has been observed upon irradiation under vacuum at 77 K with polychromatic light and applying four different filters to the emitted radiation with cut-off in the range between 400 nm and 495 nm. The process has been monitored by EPR as the photoexcitation ends up in the formation of trapped electron centers (signal at g = 1.96) and trapped hole centers (signal in the range 2.021 >g > 2.003) both clearly detected by this technique. A scheme of the energy state distribution in the band gap of the defective oxide, obtained coupling EPR and photoluminescence results, is proposed. Finally, a non-negligible fraction of the visible light generated carriers reach the surface of the nanocrystals, entailing the typical redox reactions of photocatalysis as indicated by the detection of hydroxyl radicals in solution performed by spin-trapping. For this reason, the wet chemistry prepared zinc oxide can be considered a visible light active (VLA) system.

DNA Strand Break Properties of Protoporphyrin IX by X-Ray Irradiation against Melanoma.

Recent reports have suggested that 5-aminolevulinic acid (5-ALA), which is a precursor to protoporphyrin IX (PpIX), leads to selective accumulation of PpIX in tumor cells and acts as a radiation sensitizer in vitro and in vivo in mouse models of melanoma, glioma, and colon cancer. In this study, we investigated the effect of PpIX under X-ray irradiation through ROS generation and DNA damage. ROS generation by the interaction between PpIX and X-ray was evaluated by two kinds of probes, 3′-(p-aminophenyl) fluorescein (APF) for hydroxyl radical (•OH) detection and dihydroethidium (DHE) for superoxide (O2•-). •OH showed an increase, regardless of the dissolved oxygen. Meanwhile, the increase in O2•- was proportional to the dissolved oxygen. Strand breaks (SBs) of DNA molecule were evaluated by gel electrophoresis, and the enhancement of SBs was observed by PpIX treatment. We also studied the effect of PpIX for DNA damage in cells by X-ray irradiation using a B16 melanoma culture. X-ray irradiation induced γH2AX, DNA double-strand breaks (DSBs) in the context of chromatin, and affected cell survival. Since PpIX can enhance ROS generation even in a hypoxic state and induce DNA damage, combined radiotherapy treatment with 5-ALA is expected to improve therapeutic efficacy for radioresistant tumors.

Degradation of octane using an efficient and stable core-shell Fe3O4@C during Fenton processes: Enhanced mass transfer, adsorption and catalysis

Volatile organic compound (VOC) elimination technologies have been investigated to alleviate health damage and to reduce serious environmental risks. The degradation of hydrophobic and refractory VOCs calls for advanced oxidation processes with high degradation efficiency and low-level toxic byproduct generation. In this study, core-shell Fe3O4@C was employed as an advanced oxidation microreactor for hydrophobic and refractory VOC removal during the Fenton process, and octane was chosen as a typical target pollutant. The average octane removal efficiency increased by 41.6%, while the main byproduct concentrations decreased by 65.8% in the initial 60 min compared with Fe3O4. Density functional theory (DFT) calculations revealed the key role of FeOC bond during the regeneration of Fe(II) species, and the enhanced octane adsorption process by the carbonyl sites. Calculation of mass transfer enhancement factor proved that the carbon shell was critical during mass transfer process. The advanced oxidation mechanism was investigated by detection and measurement of byproducts and hydroxyl radicals and XPS analysis. The synergism and the octane degradation pathway was proposed based on the two main types of reactions. This core-shell Fenton system suggests a promising approach for catalyst and microreactor design in advanced oxidation technologies for refractory VOCs removal.

Highly efficient and stable FeIIFeIII LDH carbon felt cathode for removal of pharmaceutical ofloxacin at neutral pH

The traditional electro-Fenton (EF) has been facing major challenges including narrow suitable range of pH and non-reusability of catalyst. To overcome these drawbacks we synthesized FeIIFeIII-layered double hydroxide modified carbon felt (FeIIFeIII LDH-CF) cathode via in situ solvo-thermal process. Chemical composition and electrochemical characterization of FeIIFeIII LDH-CF were tested and analyzed. The apparent rate constant of decay kinetics of ofloxacin (OFC) with FeIIFeIII LDH-CF (0.18 min−1) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05 min−1) at pH 3 with 0.1 mM Fe2+ under same current density (9.37 mA cm-2). Also, a series of experiments including evolution of solution pH, iron leaching, OFC removal with trapping agent and quantitative detection of hydroxyl radicals (OH) were conducted, demonstrating the dominant role of OH generated by surface catalyst via ≡ FeII/FeIII on LDH cathode for degradation of organics as well contributing to high efficiency and good stability at neutral pH. Besides, formation and evolution of aromatic intermediates, carboxylic acids and inorganic ions (F–, NH4+ and NO3–) were identified by High-Performance Liquid chromatography, Gas Chromatography–Mass Spectrometry and ionic chromatography analyses. These findings allowed proposing a plausible degradation pathway of OFC by OH generated in the heterogeneous EF process.

In situ detection of hydroxyl radicals in mitochondrial oxidative stress with a nanopipette electrode.

A novel nanopipette electrode was facilely constructed for the detection of ˙OH based on the inner surface wettability. The nanopipettes with excellent analytical performance were empolyed for in situ detection of ˙OH changes induced by mitochondrial oxidative stress and further utilized to study the association of ˙OH with Alzheimer's disease.

A new FRET probe for ratiometric fluorescence detecting mitochondria-localized drug activation and imaging endogenous hydroxyl radicals in zebrafish.

A new FRET probe has been prepared for ratiometric fluorescence detection of hydroxyl radicals. It has been successfully used for detecting mitochondria-localized drug activation in living cells and imaging endogenous hydroxyl radicals in zebrafish gastrointestinal (GI) tracts under normal culturing conditions.

Synthesis and activity of a coumarin-based fluorescent probe for hydroxyl radical detection.

As a type of reactive oxygen species (ROS), hydroxyl radical (·OH) is closely associated with many kinds of diseases. The present study aimed to develo p a novel OH fluorescent probe based on coumarin, a new compound that has not been previously reported. This probe exhibited good linear range and selectivity for ·OHl, and is able to avoid interference from some metal ions and other kinds of ROS (H2 O2 , O2 .- , 1 O2 , and HClO). Meanwhile, this probe has been used to evaluate the ·OH-scavenging efficiency of different compounds, such as isopropyl alcohol, cytosine, uracil, Tempo, Glutathione (GSH), and dimethyl sulfoxide (DMSO). Therefore, the present study shows that this probe not only can effectively measure the level of ·OH, but also can assess the ·OH-scavenging efficiency of different compounds. Furthermore this current study suggested that following further optimization, this probe may be potentially applied in the diagnosis of oxidative stress in human body.

Fluorescence detection of hydroxyl radical generated from oxygen reduction on Fe/N/C catalyst

Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction (ORR) in fuel cells. However, poor stability of Fe/N/C catalyst, mainly attributed to the oxidation corrosion by aggressive •OH radical, severely hampers its applications. However, the exact mechanism for generation of •OH is unclear yet. Herein, we developed a fluorescent method to effectively detect •OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe. A great difference in potential dependence between •OH and H2O2 generated from the ORR was observed, which suggests that •OH is not generated from the decomposition of H2O2 as traditional viewpoint.