Detection and application of hypochlorous acid in both aqueous environments and living organisms.

The scarcity of water resources has raised concerns regarding drinking water safety. Excessive addition of hypochlorous acid (OCl-) as a disinfectant in drinking water can result in severe consequences. Moreover, abnormal levels of OCl- within the human body can lead to various diseases. Employing fluorescence analysis, the design and synthesis of specific fluorescent probes for simultaneous detection of OCl- in water environments and living organisms holds strategic significance in ensuring the safety of drinking water and mitigating potential risks caused by its abnormal concentrations. This article utilizes naphthalimide as a precursor to develop a novel probe enabling highly sensitive detection of OCl- in water environments and at the organelle level within living organisms. This endeavor serves to provide assurance for drinking water safety and offers health alerts.

A triphenylamine-based carbohydrazide hydrazone fluorescent probe for selective detection of hypochlorite and sensing acidic gases.

Hypochlorous acid and its hypochlorite are important reactive oxygen species in the body, and are involved in various physiological processes related to immunity; their rapid detection is of great significance. Here, we synthesized a fluorescent probe (TPAS) by condensation of 4-(diphenylamino)benzaldehyde, carbohydrazide, and salicylaldehyde, which can be used for the detection of ClO- in water and sensing of acidic gas in its solid state. The probe showed strong selective recognition of ClO- in acetonitrile and good tolerance to interference ions. There were good linear responses between the intensity of absorbance and fluorescence and the amount of ClO-. The TPAS solid and its paper strips can emit red fluorescence when exposed to volatile acidic vapours. After being treated with NH3, the red fluorescence can be restored to yellow. The response process of TPAS to ClO- and acid gases was characterized using nuclear magnetic resonance, electrospray ionisation mass spectrometry, transmission electron microscopy, and density functional theory calculations. Furthermore, it can be utilized in analyzing ClO- in commercially available bleaching products; the detection results were basically compatible with the labelled values. In addition, the probe is biocompatible and can be applied for imaging ClO- in zebrafish.

Cyanine based ratio fluorescent probe and its application in hypochlorite detection.

Hypochlorite (ClO-), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO- or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO- is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO-, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO-, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 µM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

De Novo Design of a Highly Stable Ratiometric Probe for Long-Term Continuous Imaging of Endogenous HClO Burst.

Long-term continuous imaging of endogenous HClO burst is of great importance for the elucidation of various physiological or pathological processes. However, most of the currently reported HClO probes have failed to achieve this goal due to their insufficient photobleaching resistance under a laser source. Herein, a highly stable ratiometric probe, HFTC-HClO 1, which is capable of continuously monitoring endogenous HClO burst over a long period of time, has been judiciously developed. Briefly, the de novo development of HFTC-HClO 1 mainly involved three main steps: (1) novel coumarins (HFTC 1-5) were designed and synthesized; (2) the most stable scaffold, HFTC 3, was selected through dye screening and cell imaging validation; and (3) based on HFTC 3, three candidate HClO probes were constructed, and HFTC-HClO 1 was finally selected due to its superior sensing properties toward HClO. Furthermore, HFTC-HClO 1 can quantitatively measure HClO levels in various real samples with excellent recovery (>90.4%), and the use of HFTC-HClO 1-coated test strips for qualitative analysis of HClO in real samples was also achieved. In addition, the application of HFTC-HClO 1 for long-term continuous monitoring of intracellular HClO burst was successfully demonstrated. Significantly, HFTC-HClO 1 was able to visualize HClO generated in the rheumatoid arthritis mouse model.

A facile near-infrared xanthene fluorescence probe for visualizing of hypochlorous acid in vitro and in vivo.

BACKGROUND: Hypochlorous acid (HClO) is an important biomarker for inflammation, cardiovascular disease, and even cancer. It is of great significance to accurately monitor and quantitatively analyze the fluctuations of HClO to better understand their physiological functions. Traditional HClO detection methods such as high-performance liquid chromatography (HPLC), and mass spectrometry are preferred, but are costly and unsuitable in vivo. Near-infrared (NIR) fluorescence imaging has the advantages of high sensitivity, high temporal and spatial resolutions, minimal autofluorescence, and deep tissue penetration, which facilitates its application in biological systems. Therefore, the development of sensitivity and simple NIR fluorescence monitoring HClO methods in vivo and in vitro is essential and desirable. RESULTS: Herein, we present a NIR probe NOF3 by integrating the rhodamine scaffold and HClO-triggered moiety for the real-time detection of HClO in vitro and in vivo. NOF3 reacts with the HClO and releases the NOF-OH fluorophore of emitted signals at 730 nm, which is in the NIR region. The designed probe detected concentrations of HClO ranging from 0 to 17 µM with a low detection limit of 0.146 µM, presenting excellent sensitivity and selectivity toward HClO over other species. NOF3 manifests significantly turn-on NIR fluorescent signals in response to HClO concentration, which makes it favorable for monitoring dynamic HClO distribution in vivo. We exemplify NOF3 for the tracking of endogenously overexpressed HClO distribution in RAW 264.7 cells, and further realize real-time in vivo bioimaging of HClO activity in inflammation mice. SIGNIFICANCE: The facile NIR NOF3 probe was successfully applied to visualize endogenous and exogenous HClO in living cells and mice. This study provides not only an effective tool for spatial and temporal resolution HClO bioimaging in vivo but also possesses great potential for use in future research on HClO-related biology and pathology.

A novel fluorescent probe based on carbazole-thiophene for the recognition of hypochlorite and its applications.

A carbazole thiophene-aldehyde and 4-methylbenzenesulfonhydrazide conjugate CSH was synthesized by introducing 5-thiophene aldehyde at the 3-position of the carbazole group as the precursor and then condensing it with 4-methylbenzenesulfonhydrazide. CSH has high selectivity and sensitivity towards ClO-, which can specifically identify ClO- by UV-Vis and fluorescence spectroscopy. CSH can rapidly respond to ClO- in the physiological pH range through a fluorescence quenching pattern, accompanied by the color of CSH changing markedly from turquoise to yellowish green under the 365 nm UV light. Probe CSH exhibits a quantitative response to ClO- (0-11 µM) with a low detection limit (1.16 × 10-6 M). Cell imaging experiments have shown that CSH can capture fluorescent signals in the cyan and yellow channels of HeLa cells through fluorescence confocal microscopy, and can successfully identify exogenous ClO- in HeLa cells. In addition, probe CSH can also be used to detect ClO- in environmental water samples. These results indicate that CSH has potential application prospects in the environmental analysis and biological aspects.

Fluorescent Biomass-Based Platform for Detection of ClO- in Cells and Water-Soluble Systems.

The generation and presence of excessive hypochlorous acid derivative ionic form (ClO-) could cause various diseases, such as arteriosclerosis, DNA damage, and cardiovascular illness. It is a critical need to develop a highly sensitive sensor for reliable detection of ClO- in cells and water-soluble systems. In this work, a hydroxyl group has been introduced into the compound 2-amino-3-(((E)-4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzylidene)amino)maleonitrile (NDC) to increase its solubility in water, at the same time, the hydrazone unit was designed as a specific recognition group for the "off-on" fluorescence probe of ClO-. The probe NDC presents high selectivity, sensitivity, anti-interference, and low detection limit (67 nM) for ClO-. The recognition mechanism that ClO- breaks the C=N bond and forms the fluorescent compound 4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzaldehyde (ND-3) has been confirmed by time-of-flight mass spectrometry. The probe NDC presents a good performance in the actual test of water samples and can be designed as the test papers for the quick and convenient detection of ClO- range from 0 to 1 µM. Moreover, the practical application was demonstrated by the successful imaging of endogenous and exogenous ClO- in HeLa cells. Our fluorescent biomass-based platform opens vast possibilities for repeatability, sensitivity, and selectivity detection of ClO- in cells and water-soluble systems.

Visualization of the elevated levels of hypochlorous acid in Alzheimer's disease with a ruthenium(II) complex-based luminescence probe.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that devastatingly affects people's lives. Accumulating evidence indicates that the pathological progression of AD is inseparably connected with hypochlorous acid (HClO). However, further exploring the biological function remains an open challenging due to a lack of effective tools to image HClO in AD brains. To this end, a ruthenium(II) luminescence probe, Ru-HClO, is developed for quantitative detection and visualization of HClO in nerve cells and AD brains. Ru-HClO shows quenched luminescence due to the PET process (excited electron transfer from Ru(II) center to diaminomaleonitrile) and the CN bond isomerization in the excited state. The HClO-triggered specific cleavage reaction with Ru-HClO cleaves the CN bond to form highly luminescent Ru-COOH. Ru-HClO shows rapid response speed, high sensitivity and selectivity, excellent biocompatibility, which makes the probe to be applied to semi-quantitative analysis of HClO in nerve cells and high-throughput screening of anti-AD drugs in the AD cell model. Moreover, using Ru-HClO as a probe, present work further validated that the elevated levels of HClO secretion were accompanied by the AD progressed. These findings may provide valuable results for figuring out the biological roles that HClO played in AD but also for accelerating anti-AD therapeutic discovery.

A turn-on fluorescence strategy for hypochlorous acid detection based on DNAzyme-assisted cyclic signal amplification.

Hypochlorous acid (HClO) is a crucial active oxygen component and one of the innate immunity's barrier substances in the body. Abnormal fluctuations in HClO concentration can lead to increased oxidative stress, cellular dysfunction, and the onset of various diseases. Thus, developing convenient, affordable, efficient, and sensitive methods to monitor HClO concentration in healthcare and pathophysiology research is highly significant. In this study, we developed a novel fluorescence strategy for HClO detection based on nucleic acid oxidative cleavage and Pb2+-dependent DNAzyme. By introducing a phosphorothioate site in the hairpin-structured nucleic acid sequence, the nucleic acid probe specifically recognized HClO and underwent oxidative cleavage. Upon cleavage, the enzyme strand is liberated, forming DNAzyme. This DNAzyme then cleaves the substrate strand, liberating the initially quenched fluorescent dyes and generating a turn-on fluorescent signal. The enzyme strand produced by the oxidative cleavage of HClO can be repeatedly utilized, thus realizing the cyclic signal amplification to reduce background noise. We verified the detection mechanism of this strategy through stepwise fluorescence spectroscopy analysis and electrophoresis. Under optimal experimental conditions, the method achieved a detection limit of 5.38 nM and a linear range of 1 nM-800 nM. This method demonstrated exceptional performance in actual biological sample testing and presented an exciting opportunity for expanded utilization in clinical diagnosis and medical research.

Dental Bleaching with Phthalocyanine Photosensitizers: Effects on Dentin Color and Collagen Content.

With the increasing demand for tooth bleaching in esthetic dentistry, its safety has been the focus of a comprehensive body of literature. In this context, the aim of the present study was to evaluate the application effects of pentalysine ß-carbonylphthalocyanine zinc (ZnPc(Lys)5)-mediated photodynamic therapy in dentin bleaching and its effects on dentin collagen. We first established a new and reproducible tooth staining model using dentin blocks stained by Orange II and then bleached with ZnPc(Lys)5 (25 µM) and hydrogen peroxide (10% or 30%). Data were analyzed with one- and two-way ANOVA and a significance level of p < 0.05. ZnPc(Lys)5 effectively bleached the dentin samples to an extent comparable to hydrogen peroxide at either 10% or 30% concentrations. Further studies on the dentin morphology, chemical element distribution, and protein constituents, using an electron microscope, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and SDS-PAGE, demonstrated that treatment with the photosensitizer preserved the dentin structure and, at the same time, the major organic component, collagen type I. For comparison, hydrogen peroxide (10% or 30%) treatment significantly degraded the collagen protein. This work indicated that the photosensitizer exerts potent bleaching effects on dentin staining; importantly, does not damage dentin and its collagen content; and opens up a new strategy to further explore various photosensitizers for the bleaching of both tooth enamel and dentin.

Hypochlorous acid-activated near-infrared fluorescent probe for in vivo/exogenous detection and dairy toxicity evaluation.

Oxidative stress has been reported to be closely associated with many diseases, and an excessive overdose of hypochlorite (ClO-) can also induce stress-related diseases. In this study, we designed and synthesized a NIR probe, named W-1a based on computational analysis of DCM (4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran) derivatives for specific detection of ClO-. The probe exhibited dual fluorescence and colorimetric sensing with a response time of <1 min and a detection limit of 0.15 µM. Additionally, the probe was successfully applied for fluorescence imaging of ClO- at the cellular level and ebrafish endogenous/exogenous ClO- assay and dairy toxicity assessment. Thus, we present a potential method for developing an efficient and reliable detection of ClO- in early stage using near-infrared dyes.

Visualizing stimulus-responsive dual-ligand fluorescent probes for hypochlorite: A novel strategy for real application in tap water.

As an effective ingredient of disinfectants, ClO- inevitably remains in water, which induces potential health hazards such as lung damage and kidney disease. In this study, we synthesized stimulus-responsive dual-ligand luminol-Tb-GMP coordination polymer nanoparticles (luminol-Tb-GMP CPNPs) as highly selective fluorescent probes for the real-time and visual detection of ClO- . CPNPs consist of Tb3+ , a nuclear metal, that coordinates with GMP and luminol, an auxiliary ligand. GMP can be oxidized by ClO- and damage its structure, resulting in fluorescence quenching of CPNPs. The two-ligand CPNPs sensor has a rapid fluorescent response, significant fluorescent color change, and high sensitivity, with a linear range of 2-18 µM and a detection limit of 0.14 µM. It has been successfully used to detect ClO- in tap water, fountain water, and drinking water. Simultaneously, the portable filter paper strip was prepared to expand the range of applications outside the laboratory, which will provide a promising application for the real-time and semiquantitative analysis of ClO- .

Superoxide: The enigmatic chemical chameleon in neutrophil biology.

The burst of superoxide produced when neutrophils phagocytose bacteria is the defining biochemical feature of these abundant immune cells. But 50 years since this discovery, the vital role superoxide plays in host defense has yet to be defined. Superoxide is neither bactericidal nor is it just a source of hydrogen peroxide. This simple free radical does, however, have remarkable chemical dexterity. Depending on its environment and reaction partners, superoxide can act as an oxidant, a reductant, a nucleophile, or an enzyme substrate. We outline the evidence that inside phagosomes where neutrophils trap, kill, and digest bacteria, superoxide will react preferentially with the enzyme myeloperoxidase, not the bacterium. By acting as a cofactor, superoxide will sustain hypochlorous acid production by myeloperoxidase. As a substrate, superoxide may give rise to other forms of reactive oxygen. We contend that these interactions hold the key to understanding the precise role superoxide plays in neutrophil biology. State-of-the-art techniques in mass spectrometry, oxidant-specific fluorescent probes, and microscopy focused on individual phagosomes are needed to identify bactericidal mechanisms driven by superoxide. This work will undoubtably lead to fascinating discoveries in host defense and give a richer understanding of superoxide's varied biology.

A NIR BODIPY-based ratiometric fluorescent probe for HClO detection with high selectivity and sensitivity in real water samples and living zebrafish.

Hypochlorous acid (HClO) plays an important role in many physiological and pathological activities. In this work, a novel BODIPY-based Near-infrared (NIR) ratiometric fluorescent probe BODIPY-Hyp was designed for the rapid detection of HClO. The probe BODIPY-Hyp was highly selective and sensitive for HClO with a low detection limit of 16.74 nM and short response time of less than 60 s. The probe BODIPY-Hyp in response to HClO exhibited a significant blue-shifted fluorescence emission from 700 nm to 530 nm, and its fluorescence intensity ratio (I530 nm/I700 nm) increased about 1200 times before and after adding HClO. Moreover, the reaction mechanism of BODIPY-Hyp with HClO was verified by HRMS analysis, 1H NMR titration and DFT calculations. Furthermore, BODIPY-Hyp was successfully processed into a portable test strip-based device for the detection of HClO. In addition, the probe BODIPY-Hyp could be used in real time to monitor the levels of HClO in living zebrafish larvae. In conclusion, BODIPY-Hyp has great application potential in the life and environmental sciences.

A novel AIRE-based fluorescent ratiometric probe with endoplasmic reticulum-targeting ability for detection of hypochlorite and bioimaging.

Hypochlorite (ClO-) plays an important role in the human immune defense system, but high concentrations of ClO- in the endoplasmic reticulum (ER) damage cellular proteins, causing ER stress, cell death, and various diseases. Herein, we developed a simple hydrazone probe (1) featuring aggregation-induced ratiometric emission, which would quickly (within 20 s) and sensitively (detection limit of 15.4 µM) respond to ClO- in an almost pure aqueous solution via a fluorescent ratiometric output. Furthermore, the probe was employed to track the level of ClO- in the ER of HeLa cells and zebrafish.

Liver Injury Traceability: Spatiotemporally Monitoring Oxidative Stress Processes by Unit-Emitting Carbon Dots.

Exploring the etiology of liver injury is critical to fundamental science and precise treatment, which has not yet been achieved by molecule imaging techniques. Herein, we manage to conquer this challenge by spatiotemporally monitoring oxidative stress processes using the proposed unit-emitting carbon dots (UE-C-dots) as fluorescent probes. We discover and reveal that the UE-C-dots can specifically determine hypochlorous acid (HClO) molecules, one of the important reactive oxygen/nitrogen species (ROS/RNS) in liver injury, by an excited state oxidation mechanism. Other ROS/RNS do not interfere with the assay even if their concentrations are 1000 times higher than that of HClO due to the lowest unoccupied molecular orbital level mismatch. Real-time tomographic imaging demonstrates that different stimuli cause distinctly different HClO bursts in both temporal and spatial dimensionalities. Therefore, the measurement and analysis of temporal information substantially extend our understanding on the relationships of hepatic oxidative stress and corresponding physiological/pathological behaviors.

BODIPY-Based Fluorescent Probes for Selective Visualization of Endogenous Hypochlorous Acid in Living Cells via Triazolopyridine Formation.

In this work, the two pyridylhydrazone-tethered BODIPY compounds (2 and 3) were synthesized. These compounds aimed to detect hypochlorous acid (HOCl) species via cyclic triazolopyridine formation. The open forms and the resulting cyclic forms of BODIPYs (2, 3, 4, and 5) were fully characterized by nuclear magnetic resonance, mass spectrometry, infrared spectroscopy, and single-crystal X-ray diffraction. These two probes can selectively detect HOCl through a fluorescence turn-on mechanism with the limit of detections of 0.21 µM and 0.77 µM for compounds 2 and 3, respectively. This fluorescence enhancement phenomenon could be the effect from C = N isomerization inhibition due to HOCl-triggered triazolopyridine formation. In cell imaging experiments, these compounds showed excellent biocompatibility toward RAW 264.7 murine live macrophage cells and greatly visualized endogenous HOCl in living cells stimulated with lipopolysaccharide.

Development of a new paper-based voltage step electrocoagulation technique and application to wine classification.

This study developed a novel voltage step electrocoagulation (VSEC) technique on paper for analysis and classification of red wine samples. The concept relies on the electrode system applying voltage steps along a strip of filter paper soaked with a wine sample. The system employed a cathode array system (CAS) for voltage step application and an aluminium anode undergoing corrosion to form the green sludges responsible for wine color bleaching along the paper. The VSEC technique led to the shade of colors along the paper which can be observed by the naked-eye or using image processing software. The system was applied to classify 15 wine samples into different groups and to perform dilution and adulteration tests. In addition, the approach could be applied to approximate antioxidant properties of the wine samples as observed via the correlation between the results from VSEC and IC50 values obtained from the DPPH assay with an R2 of 0.76.

Rational construction of deep-red fluorescent probe for rapid detection of HClO and its application in bioimaging and paper-based sensing.

Hypochlorous acid (HClO), the core bactericidal substance of the human immune system, plays a vital role in many physiological and pathological processes in the human body. In this work, we designed and synthesized a novel deep-red fluorescent probe TCF-ClO for the determination of hypochlorous acid through theoretical analysis. The results showed that probe TCF-ClO exhibited excellent characteristics of long-wavelength emission (635 nm), fast response (< 1 min), and low detection limit (24 nM). In addition, it had been successfully used for imaging of HClO in living HeLa cells. More importantly, the TCF-ClO composited paper-based sensing material was successfully constructed. The RGB/gray value was obtained from a mobile phone and computer, which could achieve the quantitative detection of HClO, with a linear detection range of 0-50 µM and a detection limit of 1.09 µM (RGB mode)/3.38 µM (gray mode). The function of the paper-based sensor extended from qualitative to quantitative detection of HClO, and it is expected to become a portable device widely used in the environmental area.

Tetraphenylethylene-thiosemicarbazone based ultrafast, highly sensitive detection of hypochlorite in aqueous environments and dairy products.

We have designed and synthesised a novel fluorescent probe with a tetraphenylethylene (TPE) scaffold as an active fluorescent unit and thiosemicarbazide (TSC) group as a recognition unit. The probe, TPE-TSC, exhibited superior selectivity towards hypochlorite (ClO-) with a low limit of detection (2.0 nM). It also demonstrated a turn-off response for a brief period (<30 s) via an oxidation reaction. Furthermore, high-resolution mass spectrometry (HRMS) revealed that TPE-TSC reacted with ClO- by forming a carboxylic acid moiety in nearly 100% aqueous environments. More significantly, the probe detected ClO- in disinfectant, spiked milk samples, and spiked water samples. In all, TPE-TSC proposes an optimistic approach precisely for the determining the quality of milk and water contaminated with ClO- and trace amounts of ClO- in disinfectants.