Hypochlorite Anion Research Articles

4-Cl-edaravone and (E)-2-chloro-3-[(E)-phenyldiazenyl]-2-butenoic acid are the specific reaction products of edaravone with hypochlorite.

3-Methyl-1-phenyl-2-pyrazolin-5-one (edaravone) is a synthetic one-electron antioxidant used as a drug for treatment against acute phase cerebral infarction in Japan. This drug also reacts with two-electron oxidants like peroxynitrite to give predominantly 4-nitrosoedaravone but no one-electron oxidation products. It is believed that this plays a significant role in amelioration of amyotrophic lateral sclerosis. The drug was approved for treatment of amyotrophic lateral sclerosis in Japan and USA in 2015 and 2017, respectively. In this study, we examined the reaction of edaravone with another two-electron oxidant, hypochlorite anion (ClO−). Edaravone reacted with ClO− in 50% methanolic phosphate buffer (pH 7.4) solution containing typical two-electron reductants, such as glutathione, cysteine, methionine, and uric acid, as internal references. The concentration of edaravone decreased at a similar rate as each co-existing reference, indicating that it showed comparable reactivity toward ClO− as those references. Furthermore, 4-Cl-edaravone and (E)-2-chloro-3-[(E)-phenyldiazenyl]-2-butenoic acid (CPB) were identified as primary and end products, respectively, and no one-electron oxidation products were detected. These results suggest that edaravone treatment can bring greater benefit against ClO−-related injury such as inflammation, and 4-Cl-edaravone and CPB can be good biomarkers for ClO−-induced oxidative stress.

A novel mitochondria-targeted phosphorescence probe for hypochlorite ions detection in living cells

Monitoring hypochlorite anion (ClO−) in living cells is particularly meaningful and valuable, because over-exposure of the ClO− may cause a potential health hazard towards animals and humans. Considering the special structure and properties of the gemini surfactant, a novel amphiphilic gemini-iridium complex Ir[(ppy-iso)2(bpy-tma2Br2)] (Ir-iso) with isoniazide as a recognition site for ClO− was designed. The Ir-iso possessed an excellent water-solubility as well as a strong ClO− binding capacity, as revealed from the rapid response of emission signal towards ClO−. It was worth noting that such probe had a highly-specific selectivity with a low detection limit (20.5 nM) and was suitable in physiological environment. The cell viability assay, cell imaging, and co-location studies further proved that the Ir-iso had little cytotoxicity and was specifically localized in the mitochondria of breast cancer cells, being a promising candidate of chemo-sensor to detect the endogenous ClO− in living cells.

Catalytic Decomposition of Hypochlorite Anions by Ceria Nanoparticles Visualized by Spectroscopic Techniques

Hypochlorous acid (HOCl) and hypochlorite anions (−OCl) are nonselective oxidants produced by activated neutrophils and monocytes and play an important role in the formation of immune response of a living organism. At the same time, because of the strong oxidative properties of hypochlorites, their concentrations in cells need to be under strict control. In this paper, cerium oxide nanoparticles (nanoceria) were used for spectroscopically controlled catalytic decomposition of hypochlorite anions. The processes of scavenging of hypochlorite anions by ceria nanoparticles and regeneration of nanoceria were monitored using the changes in hypochlorite absorption and 5d → 4f luminescence of Ce3+ ions during oxidation–reduction cycles. The high oxygen deficiency of ceria nanoparticles provides sufficient mobility of oxygen ions, leading to the involvement of both surface and bulk Ce3+ ions into oxidation, whereas the recovery of initial Ce3+/Ce4+ ratio is terminated by the slow diffusion of oxygen out of ceria nanoparticles.

A new "off-on" NIR fluorescence probe for determination and bio-imaging of mitochondrial hypochlorite in living cells and zebrafish.

Hypochlorite anion (ClO-) has been recognized as host defense destructing incursive bacteria and pathogens, a signal molecule inducing occurrence of apoptosis and a noxious agent when it is overproduced. It is significant to detect ClO- in mitochondria for getting meaningful physiological and pathological information. Compared with the fluorescence probes of emission wavelength in ultraviolet or visible region, those with near-infrared (NIR) fluorescence signal are advantageous due to the deeper tissue penetrability and less photo-bleaching effect. In this work, a new "off-on" NIR ClO--specific fluorescence probe (Mito-NClO) especially located in mitochondria was designed and synthesized by condensation of diaminomaleonitrile with a new fluorophore (Mito-NCHO). A marked "turn-on" NIR fluorescence signal was observed on account of the oxidation of the imine bond by NaClO. Moreover, in the range from 0 to 20 μM, this probe had the capability to quantitatively detect ClO- with a detection limit as low as 90.2 nM. Additionally, the probe exerted other excellent properties, including larger stokes shift (117 nm), better aqueous solubility, high selectivity toward ClO-, rapid response and selective mitochondrial location. Furthermore, the bio-imaging experiments clearly demonstrated that Mito-NClO facilitated the visualization of exogenous and endogenous ClO- in living HeLa cells and zebrafish model. Therefore, we speculate that the probe Mito-NClO can be served as an ideal tool for the monitoring of ClO- in biosystems.

An o-hydroxyl aldehyde structure based naphthalimide derivative: Reversible photochromic properties and its application in ClO- detection in living cells.

A bifunctional organic compound 2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1H-benzo[de] isoquinoline-5-carbaldehyde (BHC) with photochromic properties in solid state and probe detection for ClO- in complete water solution was synthesized and fully characterized. A 'white-yellow-white' reversible photochromic behavior could be observed when alternating UV/vis light irradiation on the solid BHC powder. Good fatigue resistance and adjustable bleaching rate were shown when heating conditions changes. In addition, BHC displayed a high selectivity and low detection limit (1.16 × 10-8 M) for ClO-. The photoluminescent fluorescence "on-off" recognition result can be easily identified and BHC has been tested for safely imaging living cells and detecting hypochlorite anion in vitro and vivo. A better water solubility of BHC effectively reduces damage caused by organic solvent in cell imaging progress.

The apoA-I mimetic peptide 4F protects apolipoprotein A-I from oxidative damage.

High density lipoprotein (HDL) is prone to modification by the oxidizing and chlorinating agent hypochlorite anion (OCl-). Oxidation of apolipoprotein (apo) A-I, the major protein in HDL, reduces ABCA-1 mediated cholesterol efflux and other protective responses to HDL. The apoA-I mimetic peptide 4F has been shown to undergo oxidation; however, the ability of the peptide to mediate cholesterol efflux remains intact. Here, we show that 4F protects apoA-I from hypochlorite-mediated oxidation. Mass spectral analysis of apoA-I shows that tyrosine residues that are prone to hypochlorite-mediated chlorination are protected in the presence of 4F. Furthermore, 4F enhances the cholesterol efflux ability of apoA-I to a greater extent than either 4F or apoA-I alone, even after hypochlorite oxidation. These observations suggest that apoA-I in lipid complexes may be protected by the presence of 4F, resulting in the preservation of its anti-inflammatory and anti-atherogenic properties. These studies also form the basis for the future studies of nanoparticles possessing both apoA-I and 4F.

Arborization of Aqueous Chlorides in Pulsed Electromagnetic Fields as a Justification of Their Ability to Initiate the Formation of New Neuronal Dendrites

It is well known that low-frequency pulsed electromagnetic fields are able to stimulate the restoration of damaged neural contacts. Despite the fact that this effect is widely used by physicians, the physical basis of such an action of low-frequency pulsed electromagnetic fields remains unknown. In this aspect, it is of interest that the drying of chloride solutions prepared in negatively charged water is accompanied by the formation of tree-shaped crystals, i.e. their arborization. Based on this, it was suggested that low-frequency pulsed electromagnetic fields cause negative electrification of aqueous solutions of chlorides, which are the main inorganic anions of nerve tissues, and, as a result, axonal arborization of neurons. During the experimental verification of such an assumption, the formation of tree-like crystals in drying solutions of chlorides was detected, through which weak constant and low-frequency pulsed electric currents were previously passed. This made it possible to suggest an explanation of the nature of axonal arborization of neurons, including those damaged, which is observed under the influence of low-frequency pulsed electromagnetic fields in vivo. Since chlorides are the main inorganic anions of blood, it was also proposed to explain the formation of new capillaries under the action of low-frequency pulsed electromagnetic fields. After a more detailed analysis, it was suggested that this kind of negative electrization of aqueous solutions of chlorides was due to free hydrogen atoms, which are the products of water electrolysis. However, it was suggested that oxygen atoms, which also appear during the electrolysis of water, are bound by chloride anions to form hypochlorite anions. Thus, such oxygen atoms are not able to cause a positive electrification of aqueous media in which there are electrical currents, including currents, caused by low-frequency pulsed electromagnetic fields. Thus, the importance of chlorine anions for regenerative processes, in general, was justified. However, it has been suggested that these hypochlorite anions can stimulate cell proliferation, as well as other active forms of oxygen. Thus, an understandable physicochemical basis of the therapeutic effects of low-frequency pulsed electromagnetic fields was proposed and partially experimentally established.

A coumarin-dihydroperimidine dye as a fluorescent chemosensor for hypochlorite in 99% water.

The hypochlorite anion (OCl−), a reactive oxygen species (ROS), is an important microbicidal agent in the immune system. Accurate and selective detection of OCl− in environmental and biological samples by a fluorescent molecular sensor is an important subject. All previously reported sensors, however, have suffered from tedious multi-step synthesis for the sensors and the use of large amounts of organic solvents for the analysis. Herein, we report that a coumarin–dihydroperimidine dye prepared by facile condensation behaves as a fluorescent sensor for OCl− in 99% water. The sensor exhibits weak fluorescence, but OCl−-selective dehydrogenation of its dihydroperimidine unit creates a strong blue fluorescence. This turn-on fluorescence response facilitates selective and sensitive detection of OCl− in the physiological pH range. Ab initio calculation revealed that the fluorescence enhancement by OCl− is triggered by intramolecular proton transfer from the coumarin –OH to the imine nitrogen of the formed perimidine moiety.

A Highly Selective Fluorescence Turn‐On Probe for the Sensing and Bioimaging of Hypochlorite Anion in Aqueous Media

AbstractA newly designed and structurally characterized 2,6‐diformyl −4‐methyl‐phenol based moiety detects the hypochlorite ions as low as 75.9 nM selectively in DMSO–H2O (1:9, v/v) solution (100 mM HEPES buffer, pH 7.4) based on oxidation cleavage reaction of the thioacetal linkage. To establish this reaction based pathway in favor of sensing hypochlorite ions, the detailed spectroscopic studies have been carried out systematically supported by theoretical (DFT) studies. The efficacy of this non‐cytotoxic probe has been checked by acquiring the fluorescence images of the distribution of the hypochlorite (ClO−) ion in living cells.

A fluorometric and mitochondrion-targetable probe for rapid, naked-eye test of hypochlorite in real samples

Hypochlorite anion is a ubiquitous reactive molecule in the terminal disinfection systems, inflammatory stress and immune systems. Thus, rapid and visual monitoring ClO− in water and biological samples is very meaningful for water quality safety and toxicity assessment of contaminants. Herein, a colorimetric and fluorometric probe (Rh-ClO) based on rhodamine B fluorophore and thiophene-2-carbohydrazide has been unveiled and successfully utilized for ClO− detection in water samples and HeLa cells. Upon addition of ClO−, color changes of solution from colorless to pink were immediately visible to the naked-eyes, meanwhile, brilliant red fluorescence was observed under excited at UV light (365nm). Rh-ClO displayed high selectivity and sensitivity for ClO−, and the detection limit was 7μmol/L calculated from the fluorescence titration. With the aid of its merits including rapid response to ClO− within 10s, Rh-ClO and its test paper could successfully detect ClO− in water. Additionally, HeLa cells image co-stained with Rh-ClO and Rh123 demonstrated that Rh-ClO possessed excellent and fast cell-membrane permeability and mitochondrion-targetability. It was clearly confirmed that Rh-ClO would be a promising probe for rapid tracking of ClO− in water samples and in mitochondria of living cells.

Novel diaminomaleonitrile-based fluorescent probe for ratiometric detection and bioimaging of hypochlorite

Highly sensitive and selective detection for hypochlorite anion (OCl−) is of extreme significance due to its important role and function in biological systems. Herein, a diaminomaleonitrile derivative (DMD) has been developed as a novel ratiometric and colorimetric fluorescent probe for OCl− detection. Consistent with the UV–vis spectral change, the probe DMD exhibited promptly a color change from canary yellow to gules upon the addition of OCl−, which could be easily observed by naked-eyes. In addition, the detection limit was found to be 0.5 nM, which is much lower than that of many reported OCl− probes. More importantly, owing to its excellent sensing properties and negligible cytotoxicity, probe DMD can be conveniently applied to image intracellular OCl− in living cells, indicating it a promising tool in biological applications.

A thiocoumarin-based fluorescent probe for detection of hypochlorite with high selectivity over other typical desulfurizing agents (Hg2+/Ag+)

A thiocoumarin dye, Probe 1, has been developed for the detection of hypochlorite anion (ClO−) via the desulfurization of thiocoumarin. The heavy atom effect efficiently quenched the fluorescence of Probe 1. Upon the addition of ClO−, Probe 1 was instantaneously oxidized into its oxo form, resulting in a strong yellow fluorescence with an emission maximum at 552 nm and a large Stokes shift (141 nm). This probe exhibited excellent selectivity toward ClO− over other reactive oxygen species, common metal ions and anions. Gratifyingly, the typical desulfurizing agents such as Hg2+ and Ag+ had little interfering effect on the behavior of Probe 1 for the detection of ClO−. This probe dispalyed a low detection limit (1.7 × 10−7 M). Importantly, the application of this probe for the detection of endogenous ClO− in living cells had been successfully demonstrated.

A Ratiometric Fluorescent Probe for Selective Detection of Hypochlorite Anion

A new fluorescent probe based on rhodamine and naphthalimide was synthesized for the discrimination of hypochlorite anion. Upon addition of NaClO, the emission intensities ratio (I576 nm/I528 nm) of the probe 1 increased quickly accompanied with the obvious change of color. The probe 1 also exhibited highly selectivity and fast response to hypochlorite anion. Furthermore, the newly proposed probe has been applied for natural water samples, and a satisfied result was obtained.

Primum non nocere - The effects of sodium hypochlorite on dentin as used in endodontics.

The antimicrobial and tissue-dissolution capacities of NaOCl render it a well-accepted agent for root canal debridement. These highly desirable properties, however, appear to be intertwined with the untoward effect of collagen matrix degradation within mineralized dentin. Because of its small size, the hypochlorite anion is capable of infiltrating mineralized collagen and destroying the collagen fibrils, producing a mineral-rich, collagen sparse ghost mineral matrix with reduced flexural strength. Findings from the present work challenge the biosafety of NaOCl when it is used in high concentrations and for lengthy time periods during root canal treatment, and laid the background work for future biomaterials design in debridement of the canal space.

Intracellular detection of toxic hypochlorite anion by using a nontoxic rhodamine based sensor

Intracellular detection of toxic hypochlorite anion by using a nontoxic rhodamine based sensor

Coumarin-Based Fluorescent Probe for Hypochlorites and Real Application in Tap Water.

Taking advantages of both the oxidation property of hypochlorite and different coordination properties of Cu+ and Cu2+ ions, we developed a new fluorescent probe for hypochlorite anion, namely, compound C1. In the presence of ClO-, the sensing system displayed extraordinary fluorescence quenching, which was beneficial to the production of a high signal output during detection process. By virtue of its special oxidation property, the probe displayed high selectivity for ClO- over other anions. Moreover, this novel sensing system could be used for the analysis of ClO- levels in tap water and potentially in environmental samples.

The development of 1,3-diphenylisobenzofuran as a highly selective probe for the detection and quantitative determination of hydrogen peroxide

1,3-Diphenylisobenzofuran (DPBF) has been developed as a selective probe for the detection and quantitative determination of hydrogen peroxide in samples containing different reactive nitrogen and oxygen species (RNOS). DPBF is a fluorescent probe which, for almost 20 years, was believed to react in a highly specific manner toward some reactive oxygen species (ROS) such as singlet oxygen and hydroxy, alkyloxy or alkylperoxy radicals. Under the action of these individuals DPBF has been rapidly transformed to 1,2-dibenzoylbenzene (DBB). In order to check if DPBF can act as a unique indicator of the total amount of different RNOS, as well as oxidative stress caused by an overproduction of these individuals, a series of experiments was carried out, in which DPBF reacted with peroxynitrite anion, superoxide anion, hydrogen peroxide, hypochlorite anion, and anions commonly present under biological conditions, namely nitrite and nitrate. In all cases, except for hydrogen peroxide, the product of the reaction is DBB. Only under the action of H2O2 9-hydroxyanthracen-10(9H)-one (oxanthrone) is formed. This product has been identified with the use of fluorescence spectroscopy, NMR spectroscopy, high performance liquid chromatography coupled with mass spectrometry, infrared spectroscopy, elemental analysis, and cyclic voltammetry (CV). A linear relationship was found between a decrease in the fluorescence intensity of DPBF and the concentration of hydrogen peroxide in the range of concentrations of 0.196–3.941 mM. DPBF responds to hydrogen peroxide in a very specific way with the limits of detection and quantitation of 88 and 122.8 μM, respectively. The kinetics of the reaction between DBBF and H2O2 was also studied.

Low-level laser therapy stimulates the oxidative burst in human neutrophils and increases their fungicidal capacity.

Low-level laser therapy (LLLT) is known to enhance mitochondrial electron transfer and ATP production; thus, this study asked whether LLLT could stimulate the oxidative burst in human neutrophils (PMN) and improve their ability to kill microorganisms. Blood from healthy human subjects was collected and PMN were isolated from the samples. PMN were treated in vitro with 660nm or 780nm CW laser light at 40mW power and increasing energies up to 19.2J and were subsequently incubated with Candida albicans cells. Generation of hydroxyl radicals, hypochlorite anions and superoxide anions by PMN were checked using fluorescent probes and chemiluminescence assays; a microbicidal activity assay against C. albicans was also performed. LLLT excited PMN to a higher functional profile, which was translated as superior production of reactive oxygen species (ROS) and increased fungicidal capacity. The most efficacious energy was 19.2J and, interestingly, the 660nm light was even more efficacious than 780nm at increasing the respiratory burst of PMN and the fungicidal capacity. Human neutrophils (PMN) were stimulated in vitro with 660nm or 780nm CW laser light at 40mW of power and a total energy of 19.2J. Low-level laser therapy (LLLT) excited PMN to a higher functional profile, which was translated as a superior production of reactive oxygen species (ROS) such as hydroxyl radicals (HO• ) and hypochlorite anions (ClO- ) (Figure) and increased fungicidal capacity against Candida albicans cells.

A high-resolution mitochondria-targeting ratiometric fluorescent probe for detection of the endogenous hypochlorous acid

Hypochlorite anion, one of the biologically important reactive oxygen species, plays an essential role in diverse normal biochemical functions and abnormal pathological processes. Herein, an efficient high-resolution mitochondria-targeting ratiometric fluorescent probe for hypochlorous acid detection has been designed, synthesized and characterized. It is easily synthesized by the condensation reaction (CC) of a 2-(2-hydroxyphenyl) quinazolin-4(3H)-one fluorophore and a cyanine group (mitochondria-targeting), which made the whole molecular a large Stokes shift (210nm) and the two well-resolved emission peaks separated by 140nm. As a result, it is considered as a good candidate for high resolution hypochlorous acid imaging in live cells. The ratiometric fluorescent probe exhibited outstanding features of high sensitivity, high selectivity, rapid response time (within 50s), and excellent mitochondria-targeting ability. Moreover, the probe can also be successfully applied to imaging endogenously hypochlorous acid in the mitochondria of living cells with low cytotoxicity, and high resolution.

Highly selective, sensitive and naked-eye fluorescence probes for the direct detection of hypochlorite anion and their application in biological environments

Two novel rhodamine B-based fluorescent probes RBT and RBP for the hypochlorite anion (ClO−) were designed, synthesized, and characterized. They exhibited highly selective and sensitive recognition toward ClO− over other metal ions, nonmetal ions, reactive oxygen species (ROS), reactive nitrogen species (RNS) and special oxidants in ethanol-water (4/6, v/v, 20mmol/L HEPES, pH 7.0) media in the fluorescence and UV–vis spectra. Cytotoxicity and bioimaging studies by L929 cells and living mice indicated that the probes were low cytotoxicity, cell permeable and suitable for detecting ClO− in biological environments.