Selective Detection Of Hypochlorous Acid Research Articles

A Hydroxytricyanopyrrole-Based Fluorescent Probe for Sensitive and Selective Detection of Hypochlorous Acid.

Hypochlorous acid (HOCl) is a reactive substance that reacts with most biomolecules and is essential in physiological and pathological processes. Abnormally elevated HOCl levels may cause inflammation and other disease responses. To further understand its key role in inflammation, HOCl must be detected in situ. Here, we designed a hydroxytricyanopyrrole-based small-molecule fluorescent probe (HTCP-NTC) to monitor and identify trace amounts of HOCl in biological systems. In the presence of HOCl, HTCP-NTC released hydroxyl groups that emit strong fluorescence covering a wide wavelength range from the visible to near-infrared region owing to the resumption of the intramolecular charge transfer process. Additionally, HTCP-NTC demonstrated a 202-fold fluorescence enhancement accompanied by a large Stokes shift and a low detection limit (21.7 nM). Furthermore, HTCP-NTC provided a rapid response to HOCl within 18 s, allowing real-time monitoring of intracellular HOCl. HTCP-NTC exhibited rapid kinetics and biocompatibility, allowing effective monitoring of the exogenous and endogenous HOCl fluctuations in living cells. Finally, based on fluorescence imaging, HTCP-NTC is a potential method for understanding the relationship between inflammation and HOCl.

A novel TCF-aza-BODIPY-based near-infrared fluorescent probe for highly selective detection of hypochlorous acid in living cells

Hypochlorous acid/hypochlorite (HOCl/ClO-) plays important roles in killing bacterial and causing damage to living tissues, and its abnormal levels could lead to many diseases. Although great efforts have been devoted, fluorescent probes for HOCl/ClO- with near-infrared fluorescence, good selectivity/sensitivity, and low background are still important and urgent. In this work, a novel double-bond-linked TCF-aza-BODIPY-based near-infrared fluorescent probe (3) was rationally designed, successfully prepared, and applied for sensing HOCl/ClO- in both solutions and living RAW264.7 cells, showing good selectivity and fluorescence “turn-on” phenomenon at 670 nm with low background. The limit of detection towards ClO- was determined to be 0.36 μM through the linear fluorescence changes at 670 nm in a broad ClO--concentration range of 0–150 μM. Furthermore, the sensing mechanism was investigated by mass spectrometry and compared with 1, suggesting that the remarkable spectroscopic changes could be ascribed to the oxidization of the double bond to the aldehyde group, accompanied with the leaving of the TCF group. Confocal imaging experiments also confirmed the remarkable intracellular fluorescence enhancements through incubation of ClO- and phorbol ester 12-myristate 13-acetate (PMA) in RAW264.7 cells. Therefore, for the first time, we reported a near-infrared TCF-aza-BODIPY-based fluorescent probe for highly sensitive and fluorescence “turn-on” detection of both exogenous and endogenous HOCl in living RAW264.7 cells through the quick oxidation of a conjugated double bond.

Selective detection of hypochlorous acid in living cervical cancer cells with an organoselenium-based BOPPY probe

The synthesis and crystal structure of the first selenium-containing BOPPY probe. The probe is selective for exogenous and endogenous HOCl detection in HeLa cells with a “turn-on” fluorescence response.

Rational construction of long-wavelength emissive AIE molecules and their application for sensitive and visual detection of HClO

Herein, two small-molecule fluorescent dyes, 2-(4-(diethylamino)-2-((4-(4,4,5,5- tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)benzylidene)malononitrile (BASM) and ethyl-2-cyano-3-(4-(diethylamino)-2-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)phenyl)acrylate (BASE) with aggregation-induced emission characteristics are facilely synthesized and they were applied for the sensitive and selective detection of hypochlorous acid (HClO). For these novel AIE molecules, intricate structure and enormous π-conjugation system are no longer necessary. Due to the enhanced effect of intramolecular charge transfer and restricted intramolecular rotation, BASM and BASE displayed reinforced and long-wavelength emission in solid states and aggregated states. Moreover, the BASM has been rationally designed as a fluorescent probe of HClO based on the selective reaction between the BASM and HClO which generates a fluorescence efficient cyano iminocoumarin. The BASM displays a wide linear range for HClO from 0.5 to 10 μM and the limit of detection is as low as 6.46 nM. Intriguingly, excess amount (10–50 μM) of HClO causes fluorescence quenching due to a unique oxidation process, also explains the sensitivity and selectivity of BASM towards HClO. Furthermore, probe BASM is successfully employed for several practical applications such as detection of HClO in actual samples, fabrication of paper-based sensors, and fluorescence imaging in living bacteria.

Amphiphilic polymer-encapsulated Au nanoclusters with enhanced emission and stability for highly selective detection of hypochlorous acid.

It is of vital importance to develop probes to monitor hypochlorous acid (HClO) in biological systems as HClO is associated with many important physiological and pathological processes. Metal nanoclusters (NCs) are promising luminescent nanomaterials for highly reactive oxygen species (hROS) detection on the basis of their strong reaction ability with hROS. However, metal NCs typically can respond to most common hROS and are susceptible to etching by biothiols, hindering their application in the construction of effective HClO probes. Herein, we proposed a strategy to develop a nanoprobe based on Au NCs for highly sensitive and selective detection of HClO. We synthesized luminescent benzyl mercaptan-stabilized Au NCs and encapsulated them with an amphiphilic polymer (DSPE-PEG). After encapsulation, an obvious emission enhancement and good resistance to the etching by biothiols for Au NCs were achieved. More importantly, the DSPE-PEG encapsulated Au NCs can be used as a nanoprobe for detection of HClO with good performance. The luminescence of the Au NCs was effectively and selectively quenched by HClO. A good linear relationship with the concentration of HClO in the range of 5–35 μM and a limit of detection (LOD) of 1.4 μM were obtained. Additionally, this nanoprobe was successfully used for bioimaging and monitoring of HClO changes in live cells, suggesting the application potential of the as-prepared amphiphilic polymer-encapsulated Au NCs for further HClO-related biomedical research.

A general strategy for selective detection of hypochlorous acid based on triazolopyridine formation

Triazolopyridines are an important kind of fused-ring compounds. A HOCl-promoted triazolopyridine formation strategy is reported here for the first time in which hypochlorous acid (HOCl) mildly and efficiently promotes the formation of 1,2,4-triazolo[4,3-a]pyridines NT1-NT6 from various 2-pyridylhydrazones N1-N6. N6, a rhodol-pyridylhydrazone hybrid, was developed into a fluorescent probe for the selective detection of HOCl, and successfully applied to probe endogenous HOCl in living cells and zebrafish in situ and in real time. The present intramolecular cyclization reaction is selective and atom-economical, thereby not only providing an important approach for the convenient synthesis of triazolopyridines, but also offering a general strategy for sensitive, selective and biocompatible detection of endogenous HOCl in complex biosystems.

Toward rapid and selective detection of hypochlorous acid in pure aqueous media and its application to cell imaging: BODIPY-derived water-soluble macromolecular chemosensor with high sensitivity

Hypochlorous acid (HOCl), an important reactive oxygen species (ROS), plays a central role in many vital biological processes. Here a tailor-made boron dipyrromethene (BODIPY)-based polymeric probe (P1) incorporating aldoxime units was synthesized, targeting both colorimetric and fluorometric HOCl detection in pure aqueous media. On treatment with HOCl, P1 showed a distinct color change from pink to yellow and turn-on fluorescence with high sensitivity with an extremely low limit of detection (LOD = 17 nM). P1 also exhibited excellent selectivity over other competitive reactive oxygen and nitrogen species, with outstanding hydrolytic and photolytic stability, demonstrating its suitability for in-field applications. Such rapid, selective, and sensitive HOCl detection by P1 originated from oxidative dehydrogenation of BODIPY-aldoxime units to form nitrile oxide. Moreover, P1 showed low cytotoxicity and was successfully employed for imaging exogenously produced HOCl in human liver cancer cell line HepG2. Given its high water solubility, the newly designed polymeric probe enabled rapid, selective, and sensitive HOCl detection in pure aqueous media.

A water-soluble BODIPY-based fluorescent probe for rapid and selective detection of hypochlorous acid in living cells.

We designed and synthesized 4,4-di-(4'-methylmercaptophenoxy)-8-(N-methylpyridinium-2-yl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (probe 1) as a water-soluble BODIPY derivative for rapid and selective detection of hypochlorous acid. The pyridinium-2-yl linked at the meso position of BODIPY core was used to maintain highly fluorescent nature and to increase water solubility. Methylmercaptophenoxy was selected as responsive site installed on the boron atom (to replace the fluorine atom) and induced the photoinduced electron-transfer (PeT) effect to quench the fluorescence of BODIPY. The probe exhibited 83.9 μg mL-1 solubility in PBS (10 mM, pH 7.4), and possessed very low fluorescence (Φf = 0.0013). Upon addition of HClO, the probe could display a distinct response in 1 min and generate marked fluorescence enhancement by 100-fold due to the oxidation of thioether into sulfoxide to terminate PeT process. A limit of detection of 53 nM was calculated for HClO in the linear response range from 0 μM to 10 μM, and the probe was successfully applied to image HClO in living cells.

An S-alkyl thiocarbamate-based biosensor for highly sensitive and selective detection of hypochlorous acid.

We reported a near-infrared biosensor that features a dihydromethylene blue and an S-alkyl thiocarbamate linker to detect hypochlorous acid in a drastic fluorescence turn-on response. We achieved high sensitivity at the nanomolar level and high selectivity that resolves the interference issue with mercury ions and other transition metal ions. We demonstrated the response mechanism by analysing the released segments, and investigated the imaging capability to detect both exogenous and endogenous hypochlorous acid in living cells.

Selenide-containing organic resonance molecules as turn-on fluorescent probes for the selective detection of hypochlorous acid.

A new series of N-P[double bond, length as m-dash]Se resonance-based fluorescent molecules were developed and used for the detection of hypochlorous acid (HClO) with rapid response and high selectivity. These Se-containing molecules can selectively detect trace amounts of HClO in nM, showing significantly strengthened fluorescence due to the enhanced resonance variation with an increased distance between the fluorophore and Se. The design of N-P[double bond, length as m-dash]Se resonance molecules in donor-resonance-acceptor (D-r-A) architectures could be an important way to develop high-performance turn-on fluorescent probes for HClO detection.

A near-infrared ratiometric fluorescent probe for rapid and selective detection of hypochlorous acid in aqueous solution and living cells

A new ratiometric fluorescent probe (XWJ) was developed on the basis of Förster resonance energy transfer (FRET). The probe constructed by dansyl and 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene) malononitrile, exhibited a higher efficiency of energy transfer (up to 93.59%). The probe emerged excellent sensitivity and selectivity toward hypochlorous acid (HOCl). In particular, upon addition of HOCl, the probe can reveal a clear response in 25s and manifest an obvious change in fluorescence colour from red to bright yellow, which could be recognized by naked eyes. Furthermore, the calibration curve is linear in the concentration range of 0–55μM with the detection limit of 0.19μM, which means that the probe can detect HOCl in low concentration. Besides, the fluorescence emission of the acceptor arises near-infrared region (NIR) and the probe possesses a large pseudo Stokes shift (300nm) and well-separated dual emission (550/670nm). The probe showed outstanding sensitivity and selectivity toward HOCl in cell imaging.

A pinacol boronate caged NIAD-4 derivative as a near-infrared fluorescent probe for fast and selective detection of hypochlorous acid

Hypochlorous acid (HOCl) is one of highly reactive oxygen species (ROS). It is involved in both immune defense against invading microbes and the progression of many diseases including cardiovascular disease and neurodegeneration disorders. It is generated from hydrogen peroxide (H2O2) and chloride ions in the presence of myeloperoxidase in activated neutrophils. To illustrate HOCl’s biological functions, fluorescent probes, particularly those fluorescence emissions are in the near-infrared range, are highly needed for in vivo applications. Herein, we reported the design of a pinacol boronate caged near-infrared (NIR) fluorescent probe 1 derived from an Aβ binding fluorophore NIAD-4 for fast and selective detection of HOCl/ClO− over other ROS. Upon exposure to HOCl/ClO−, the pinacol boronate caging group of the probe 1 was quickly converted to electron-donating hydroxyl group, which increased intramolecular charge transfer (ICT) in the excited state and resulted in the red-shift and intensity enhancement of fluorescence emission. The probe bears several unique features: (1) It could be used as either a ratiomatic or turn-on fluorescent probe; (2) Reaction of the caging group boronate with HOCl is very fast and finishes within seconds, which provides the selectivity over H2O2; (3) The NIAD-4 fluorophore provides additional selectivity for detection of HOCl over peroxynitrite. Moreover, the utility of the probe in imaging HOCl/ClO− was demonstrated in in vitro phantom imaging studies using mouse brain homogenate as biological relevant media.

A pH-sensitive multifunctional fluorescent probe based on N-annulated perylene for the sensitive and selective detection of hypochlorous acid

The pH-sensitive multifunctional fluorescent probePNPMbased onN-annulated perylene was firstly developed for detecting HOCl selectively. And the probe could detect pH and HOCl simultaneously, and was successfully employed to detect HOCl in serum and water samples.

A cyanine-based near-infrared fluorescent probe for highly sensitive and selective detection of hypochlorous acid and bioimaging

Hypochlorous acid (HOCl) is a kind of reactive oxygen species which plays an important role in biological process. HOCl detection is of great importance in disease prevention and treatment. Herein, a cyanine-based near-infrared (NIR) fluorescent probe for HOCl has been designed and synthesized. This probe can react with HOCl in a dose-response manner along with the fluorescence of the probe quenched, the reaction through an electrophilic addition to the double bond and subsequent oxidation reaction. Experiments indicate that the probe can be acted as a selective and sensitive indicator for HOCl and the limit of detection for HOCl is estimated to be 22nM. What's more, this probe shows a low toxicity to cells and can be applied to visualize HOCl molecules in living cells. Therefore, the proposed method may make a significant contribution to HOCl detection.

A rhodamine hydrazide-based fluorescent probe for sensitive and selective detection of hypochlorous acid and its application in living cells

A rhodamine hydrazide-based fluorescent probe was developed for sensitive and selective detection of HOCl in aqueous media and living cells.

A hypochlorous acid turn-on fluorescent probe based on HOCl-promoted oxime oxidation and its application in cell imaging

A coumarin-based fluorometric probe, HS1, has been successfully developed for highly sensitive and selective detection of hypochlorous acid (HOCl). The probe is based on the specific HOCl-promoted oxidation of oxime. The reaction is accompanied by a 7-fold increase in the fluorescent quantum yield (from 0.03 to 0.21). The fluorescence intensity of the reaction between HOCl and HS1 shows a good linearity in the HOCl concentration range of 1–20μM and a low detection limit of 25nM (S/N=3). In addition, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that the HS1 probe could be an efficient fluorescent probe for HOCl in living cells.

Hypochlorous acid turn-on boron dipyrromethene probe based on oxidation of methyl phenyl sulfide

A boron dipyrromethene (BODIPY)-based fluorometric probe, HCS, has been successfully developed for the highly sensitive and selective detection of hypochlorous acid (HOCl). The probe is based on the specific HOCl-promoted oxidation of methyl phenyl sulfide. The reaction is accompanied by a 160-fold increase in the fluorescent quantum yield (from 0.003 to 0.480). The fluorescent turn-on mechanism is accomplished by suppression of photoinduced electron transfer (PET) from the methyl phenyl sulfide group to BODIPY. The fluorescence intensity of the reaction between HOCl and HCS shows a good linearity in the HOCl concentration range 1–10μM. The detection limit is 23.7nM (S/N=3). In addition, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that the HCS probe could be an efficient fluorescent detector for HOCl in living cells.

A BODIPY‐Based Probe for the Selective Detection of Hypochlorous Acid in Living Cells

Reactive oxygen species (ROS) are essential for a wide range of biological and pathological events. [1] During infection and inflammation, the phagocytic leukocytes, including neutrophils, monocytes, and macrophages generate reactive oxygen species (ROS) to kill invading bacteria and pathogens. [2] Among ROS, hypochlorous acid (HOCl/OCl )i s a highly reactive oxygen species produced from hydrogen peroxide (H2O2) and chloride ions (Cl ) by the enzyme myeloperoxidase (MPO), which is secreted by activated neutrophils. [3] Although hypochlorous acid plays important roles in the human immune-defense system, overproduction of ROS in living organism has detrimental effects on biological molecules, including nucleic acids, lipids, and proteins, resulting in the inhibition of various protein functions, and contributes to the progression of numerous human diseases, such as atherosclerosis, cancer, cardiovascular diseases, and rheumatoid arthritis. [4] Despite its importance in human health and disease, not as much is known about the mechanism of action and specific roles of HOCl in living systems in comparison with other ROS, owing to slower progress in the development of suitable probes. Several fluorescence probes for the detection and visualization of HOCl in living cells have recently been developed on the basis of the strong oxidizing properties of HOCl. [5–7] HOCl-induced oxidation reactions were employed in the design of fluorescent probes in which the fluorescence properties were regulated by the conversion of the spirocyclic form of rhodamine fluorophores into their ringopened form, [5] or through photoinduced-electron-transfer processes. [6] To facilitate practical applications of such probes, next-generation designs should emphasize higher analyte selectivity, limit susceptibility to autooxidation, and avoid demanding multistep syntheses. Herein, we report the facile synthesis and properties of a new boron-dipyrromethene (BODIPY) dye bearing a methylthioether group, and its biological application as a highly sensitive and selective

Selective Detection of Hypochlorous Acid

The authors synthesized a ­BODIPY-based fluorescent probe for hypochlorous acid 9 from p-methoxyphenol 1 and pyrrole-2-carboxaldehyde 4. The fluorescence of 9 is quenched through a photo-electron-transfer (PET) process from the BODIPY to the p-methoxyphenyl moiety. Upon exposure to HOCl, 9 is transformed to its benzoquinoid analogue 10 in which no PET takes place resulting in a fluorescence response.