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Ferroptosis is a way of cell death mainly due to the imbalance between the production and degradation of lipid reactive oxygen species, which is closely associated with various diseases. Endogenous hypochlorous acid (HOCl) mainly produced in mitochondria is regarded as an important signal molecule of ferroptosis. Therefore, monitoring the fluctuation of endogenous HOCl is beneficial to better understand and treat ferroptosis-related diseases. Inspired by the promising aggregation-induced emission (AIE) properties of tetraphenylethene (TPE), herein, we rationally constructed a novel AIE-based fluorescent probe, namely QTrPEP, for HOCl with nice mitochondria-targeting ability and high sensitivity and selectivity. Probe QTrPEP consisted of phenylborate ester and the AIE fluorophore of quinoline-conjugated triphenylethylene (QTrPE). HOCl can brighten the strong fluorescence through a specific HOCl-triggered cleavage of the phenylborate ester bond and release of QTrPE, which has been demonstrated by MS, HPLC, and DLS experiments. In addition, combining QTrPE-doped test strips with a smartphone-based measurement demonstrated the excellent performance of the probe to sense HOCl. The obtained favorable optical properties and negligible cytotoxicity allowed the use of this probe for tracking of HOCl in three different cells. In particular, this work represents the first AIE-based mitochondria-targeting fluorescent probe for monitoring the fluctuation of HOCl in ferroptosis. [ABSTRACT FROM AUTHOR]

Reactive oxygen and nitrogen species (RONS) are a range of chemical individuals produced by living cells that contribute to the proper functioning of organisms. Cells under oxidative and nitrative stress show excessive production of RONS (including hydrogen peroxide, H 2 O 2 , hypochlorous acid, HOCl, and peroxynitrite, ONOO−) which may result in a damage proteins, lipids, and genetic material. Thus, the development of probes for in vivo detection of such oxidants is an active area of research, focusing on molecular redox sensors, including boronate-caged fluorophores. Here, we report a boronate-based styryl probe with a cationic pyridinium moiety (BANEP+) for the fluorescent detection of selected biological oxidants in vitro and in vivo. We compare the chemical reactivity of the BANEP+ probe toward H 2 O 2 , HOCl, and ONOO− and examine the influence of the major intracellular non-enzymatic antioxidant molecule, glutathione (GSH). We demonstrate that, at the physiologically relevant GSH concentration, the BANEP+ probe is efficiently oxidized by peroxynitrite, forming its phenolic derivative HNEP+. GSH does not affect the fluorescence properties of the BANEP+ and HNEP+ dyes. Finally, we report the identification of a novel type of molecular marker, with the boronate moiety replaced by the iodine atom, formed from the probe in the presence of HOCl and iodide anion. We conclude that the reported chemical reactivity and structural features of the BANEP+ probe may be a basis for the development of new red fluorescent probes for in vitro and in vivo detection of ONOO−. [Display omitted] • Pyridinium-linked styryl-based boronate fluorescent probe for detection of ONOO−. • Iodide ion influences reaction between boronate probes and biological oxidants. • Iodinated dye as a marker for boronate probe and HOCl reaction in the presence of I−. • Glutathione may change products formed in reaction of boronate probe with ONOO−. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO), a highly reactive oxygen species, has important effects on human health. High selectivity and sensitivity remain challenges of fluorescent probes for detection of ClO− with a large Stokes shift. This work designed and synthesized a novel phenothiazine-based fluorescent probe TF which can detect ClO− by colorimetric and fluorescent dual signals. TF displayed turn-on fluorescence effect toward ClO− with high selectivity (≥ 28-folds) and sensitivity (LOD = 0.472 μM), fast response time (< 1 min) and large Stokes shift (150 nm) in PBS (pH = 7.4, 40% DMSO). Meanwhile, TF can visualize ClO− on the mung bean sprouts model and apply as testing strips for portable and rapid detecting ClO− by the naked eyes. A phenothiazine-based fluorescent probe with large Stokes shift was synthesized and its responding rapidly ability to detect ClO− was studied. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide, which is mainly produced in mitochondria, plays deleterious and beneficial roles in cells depending on its localized concentration. Tumor cells have been observed to have increased H 2 O 2 levels due to enhanced metabolic activity. Moderately high levels of H 2 O 2 are crucial for the growth and survival of tumor cells. Monitoring mitochondrial H 2 O 2 is essential for revealing the factors that affect cellular redox balance. In the present work, we have developed a fast responsive fluorescent probe for the detection of H 2 O 2 in mitochondria. Hcy-S shows high selectivity, sensitivity and a fast response to H 2 O 2 , enabling imaging of basal levels of mitochondrial H 2 O 2 in tumor cells in 1 min. Hcy-S has been applied to the study of the impact of HClO on H 2 O 2 level. The results revealed that endogenous HClO raises the levels of H 2 O 2 by inactivating catalase and glutathione peroxidase in HeLa and A549 cells. This study offers a novel insight into the redox balance in tumor cells. • A mitochondria-targeted fluorescent probe of H 2 O 2 has been developed. • Hcy-S exhibits a selective, sensitive and fast response to H 2 O 2. • Fluorescent imaging of H 2 O 2 in tumor cells can be obtained in 1 min. • Basal HOCl deactivates CAT and GPx and raises the levels of H 2 O 2 in tumor cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probe MB-HPD showcases exceptional optical properties, featuring a near-infrared emission wavelength of 681 nm, an impressively low detection limit of 14.3 nM, and rapid detection capability within just 20 s. • Probe MB-HPD has substantiated its efficacy in imaging HClO across various biological entities. • Probe MB-HPD exhibited remarkable proficiency in detecting HClO within mouse arthritis models and APAP-induced liver injury models. As a crucial endogenous reactive oxygen species, hypochlorous acid (HClO) plays an indispensable role in numerous physiological and pathological processes. Additionally, it serves as a biomarker closely associated with inflammation and liver injury. The utilization of near-infrared fluorescence probes has surged in recent years for live biological imaging, owing to their minimal tissue damage and potent tissue penetration capabilities. In this work, a novel near-infrared fluorescence probe MB-HPD was synthesized to sensitively detect HClO. Probe MB-HPD exhibits remarkable selectivity, high sensitivity (14.3 nM), and rapid response towards HClO (20 s). Probe MB-HPD has demonstrated successful application in the imaging of HClO within cells and zebrafish. Remarkably, it has proven to be effective for detecting HClO within environmental samples, as well as imaging HClO in mice models of arthritis and APAP-induced liver injury. These findings indicate the broad applicability of probe MB-HPD , offering a promising avenue for designing highly selective near-infrared fluorescence probes suitable for real-time HClO monitoring. [ABSTRACT FROM AUTHOR]

Heightened oxidative stress is the principal driver behind the altered metabolism of neurotransmitters within the brains of Parkinson's disease (PD). Hypochlorous acid (HClO), a variant of reactive oxygen species (ROS), plays a crucial role in several lysosomal activities. An irregular concentration of HClO may result in significant molecular damage and contribute to the onset of neurodegenerative disorders. Despite this, the precise role of lysosomal HClO in PD remains unclear, due to its fast reactivity and low levels. This is further complicated by the lack of effective in situ imaging techniques for accurately tracking its dynamics. Therefore, it is of great significance to use effective tools to map the lysosomal HClO during the pathological process of PD. In this study, we propose a fluorogenic probe named Lys-PTZ-HClO for the specific and sensitive detection of HClO. Lys-PTZ-HClO exhibits features like a fast response time (10 s) and a low detection limit (0.72 μM). Benefiting from its superior properties, the probe was used to visualize the basal HClO levels, and the variation of HClO levels in lysosomal of living cells. More importantly, this probe was successfully applied for the first time to reveal increased lysosomal HClO in a cellular model of PD. [Display omitted] • Two probes, Lys-PTZ-HClO and Lys-PTZ-HClO-1, were developed for HClO detection. • This probe showed exceptional selectivity and sensitivity in HClO detection with a low LOD (0.72 μM). • Lys-PTZ-HClO can effectively target lysosomes and monitor lysosomal HClO changes in living cells. • Lys-PTZ-HClO was successfully used for imaging HClO variation in PD cellular model. [ABSTRACT FROM AUTHOR]

Fluorophores with "push-pull" electronic structures can quench their fluorescence by shielding either part, and can be easily used to construct "double-locked" fluorescent probes. At present, research in this area is still rare. To demonstrate its feasibility, here we selected 6-acetyl-2-naphthol, a simple fluorophore with a characteristic "push-pull" structure (hydroxy-ketone) to construct a double-locked probe for the detection of HClO/H 2 O 2. Specifically, 1,3-oxathiolane was employed as an HClO-responsive group to shield the ketone (pull group), while the hydroxy (push group) was protected by an H 2 O 2 -responsive boronate ester group, resulting in the HClO/H 2 O 2 -specific probe Sa1. In vitro experiments confirmed that Sa1 emits fluorescence only in the presence of both HClO and H 2 O 2 , exhibiting remarkable concentration- and time-dependent fluorescence responses. Additionally, Sa1 displayed excellent selectivity and low toxicity. Finally, through cell and zebrafish imaging experiments, the dual detection capability of Sa1 in biological systems was validated. [Display omitted] • A "double-locked" fluorescent probe Sa1 based on a "push-pull" fluorophore was constructed. • Simple and versatile design integrates 6-acetyl-2-naphthol fluorophore with HClO/H 2 O 2 -responsive groups. • High specificity and selectivity for HClO/H 2 O 2 makes probe valuable for optical imaging applications. • Imaging experiments in cells and zebrafish demonstrate Sa1 's potential for biomedical research. [ABSTRACT FROM AUTHOR]

[Display omitted] • The near infrared ratiometric probe (FLD) could detect HClO in multi-applications. • The test strips loaded with probe FLD realized the visual detection of HClO. • The portable platform based on probe FLD and smartphone was established. • HClO levels was observed in the cell models of oxidative stress and ferroptosis. During the COVID-19 epidemic, hypochlorous acid (HClO) was frequently utilized for indoor and outdoor disinfection. The sensitive and selective detection of HClO puts forward high requirements for food safety. Furthermore, HClO is crucial for physiological and pathological activities. However, excessive HClO is harmful to the environment, animals, and humans. Therefore, it is imperative to construct a highly selective and sensitive HClO detection method to determine the safety of food and water, as well as the role of physiological and pathological processes. Herein, we successfully developed a near-infrared (NIR) ratiometric fluorescent probe FLD , which had high practicality and wide application range and was utilized to detect HClO in real samples and organisms. Probe FLD had the advantages of simple synthesis, high selectivity and sensitivity, significant colorimetric change, and low detection limit. Probe FLD was loaded onto test strips to create a single, reasonably priced solid sensor that enabled the visual detection of HClO. The experiments with real samples showed that the probe had good accuracy and precision. Importantly, the measurement of HClO levels in oxidative stress and ferroptosis models was successfully accomplished. Overall, probe FLD 's outstanding qualities make it a good prospect for application in environmental monitoring, food safety, and biology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• A "turn-on" fluorescence probe (PNL) based on a novel hypochlorous acid (HOCl)-induced cyclization response mechanism is developed. • PNL features short response time (10 s), excellent selectivity, low cytotoxicity and reliability at a wide range of pH values (3.0–11.5). • Quantitative determination of HOCl in real water samples has been achieved via the smartphone utilizing PNL as a probe. • Applications of PNL in fluorescence imaging of HOCl in vitro and visualization of HOCl in an inflammatory model are successfully demonstrated. Hypochlorous acid (HOCl), as an important reactive oxygen species (ROS), plays key roles in normal physiological activities. Simultaneously, HOCl is also an efficient and strong oxidant, and is widely used in disease prevention and disinfection. Nevertheless, abnormal expression or excessive intake of HOCl may cause some serious diseases. Accordingly, the high sensitivity and specificity detection of HOCl in organisms and the environment is significant for understanding its roles in biology and environmental protection. Herein, a novel responsive 1,8-naphthalimide-based fluorescence probe PNL for the detection of HOCl was reported by a novel recognition mechanism. In the presence of HOCl, the PET effect of PNL was inhibited by the HOCl-induced cyclization reaction, leading to the "turn-on" fluorescence response. The recognition mechanism of PNL towards HOCl was determined by HR-MS, and the fluorescence "turn-on" sensing mechanism was rationalized via DFT calculation. PNL possesses the advantages of short response time (10 s), excellent selectivity, low cytotoxicity and reliability at a wide range of pH (3.0–11.5). Furthermore, the quantitative determinations of HOCl in practical water samples were achieved via the smartphone using PNL as the probe. Most importantly, the applications of PNL in fluorescent imaging of HOCl in vitro and the visualization of HOCl in an inflammatory model were successfully demonstrated. The development of PNL would also provide more abundant design strategies for the construction of HOCl fluorescence probes in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new lysosome-targeted fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Lysosomes, as crucial acidic organelles in cells, play a significant role in cellular functions. The levels and distribution of hypochlorous acid (HOCl) within lysosomes can profoundly impact their biological functionality. Hence, real-time monitoring of the concentration of HOCl in lysosomes holds paramount importance for further understanding various physiological and pathological processes associated with lysosomes. In this study, we developed a bodipy-based fluorescent probe derived from pyridine and phenyl selenide for the specific detection of HOCl in aqueous solutions. Leveraging the probe's sensitive photoinduced electron transfer effect from phenyl selenide to the fluorophore, the probe exhibited satisfactory high sensitivity (with a limit of detection of 5.2 nM and a response time of 15 s) to hypochlorous acid. Further biological experiments confirmed that the introduction of the pyridine moiety enabled the probe molecule to selectively target lysosomes. Moreover, the probe successfully facilitated real-time monitoring of HOCl in cell models stimulated by N -acetylcysteine (NAC) and lipopolysaccharide (LPS), as well as in a normal zebrafish model. This provides a universal method for dynamically sensing HOCl in lysosomes. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) and peroxynitrite (ONOO−) are pivotal biomarkers of oxidative stress, intricately associated with diverse physiological and pathological processes. Nonetheless, due to the lack of methods to detect both HOCl and ONOO−, many of their roles remain obscure. In order to resarch the intrinsic interrelationship between HClO and ONOO− and the distribution of the two active substances within the cell, it is highly beneficial to develop fluorescence sensors capable of exhibiting distinct signals for HClO, ONOO−, and the combination of HClO/ONOO−. Here, we reasonably designed and constructed a new fluorescence sensor (DURC) with three different fluorescence signal outputs of blue, red and blue/red for HClO, ONOO−, and the combination of HClO/ONOO−, respectively. DURC exhibits high sensitivity in detecting HClO (58.6 nM) and ONOO− (89.3 nM). Moreover, DURC could effectively detects exogenous and endogenous HClO/ONOO− in living cells. Hence, this innovative fluorescent probe with a dual response capability can serve as a valuable tool for investigating the functions of HClO and ONOO−, as well as their involvement in physiological and pathological processes. [Display omitted] • DURC with high sensitivity, selectivity and rapid response to ONOO− and HClO/ONOO− with three sets of fluorescence signals. • DURC possesses a 7-hydroxycoumarin and rhodamine. • DURC was successfully adopted to detect endogenous HClO and ONOO−. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) plays important roles in many pathological and physiological processes. Herein we present a novel strategy to develop HOCl probe by one-step synthesis of rhodamine-thiophene dyad, rho-T. Unexpectedly, the thiophene moiety did not cause the fluorescence quenching of the xanthene moiety. Upon addition of HOCl, the ClO− anion attacks the carbon 9 position of rho-T and chlorinate the xanthene ring, resulting in fluorescence and absorption quenching of rho-T. rho-T exhibits linear response with increasing concentration of HOCl (R2 = 0.9875) with high sensitivity (Limit of Detection (LOD) = 2.36 nM) and selectivity in a fast response time (10 s). Finally, rho-T was successfully employed to detect HOCl in living cells and mice. Rhodamine-thiophene dyad for colorimetric and fluorescent sensing HOCl based on a novel mechanism. [Display omitted] • Rhodamine-thiophene dyad was synthesized through one-step reaction for HOCl sensing. • Excellent sensitivity, selectivity and fast response toward HOCl. • New sensing mechanism for HOCl was proposed. • The chemoprobe is capable of detecting HOCl in living cells and mice. [ABSTRACT FROM AUTHOR]

Singlet oxygen (1O 2) and hypochlorite (ClO-) are two important reactive oxygen species. They coexist in living systems and can be interconverted in organisms, being involved in a variety of pathophysiological processes. Lipid droplets (LDs) are organelles that transport and store lipids, and 1O 2 and ClO- tend to destroy unsaturated lipids, leading to lipid oxidation and causing a range of diseases. Here we proposed the first dual-response fluorescent probe DBCC that can simultaneously distinguish 1O 2 and ClO- within LDs. The probe is almost non-fluorescent, while significant fluorescence enhancement can be observed in the blue and green channels after treatment with 1O 2 and ClO-, respectively. With the excellent properties of high sensitivity, good selectivity and wide tolerance range, the probe DBCC has been successfully used to detect 1O 2 and ClO- in HepG2 cells and zebrafish, and faultlessly realized endogenous and exogenous 1O 2 and ClO- imaging in LDs. This work provides a powerful analytical tool for further investigating the levels of 1O 2 and ClO- in LDs and associated diseases. [Display omitted] • A dual-response fluorescent probe DBCC based on Nile red skeleton was developed. • The probe can detect 1O2 and ClO- simultaneously. • The probe exhibits excellent lipid droplets targeting ability. • 1O2 and ClO- imaging in vivo and in vitro were achieved. [ABSTRACT FROM AUTHOR]

In this paper, we designed and synthesized a novel phenylazo-based fluorescent probe (RHN) for the sensing and imaging of hypochlorous acid (HClO) in mitochondria in living cells. In this process, HClO promoted the oxidation of the phenylazo group to generate a free Rhodol fluorophore moiety, which in turn restored strong fluorescence and realized the detection of HClO. As expected, RHN exhibited high selectivity, high sensitivity and rapid response, with detection limits as low as 22 nM (1.155 ng/mL). Importantly, the results of the cell imaging experiments indicated that RHN has the ability to image and sense HClO in mitochondria, which is of great significance for exploration of the specific role of HClO in both the immune system and diseases. [ABSTRACT FROM AUTHOR]

Scheme 1 Illustration of the synthetic procedure of Br-CDs-AM and the application in sensing HClO in food matrices and lysosomal imaging. [Display omitted] • Br-CDs with excellent photostability were synthesized by self-doping strategy. • Br-CDs-AM as a probe was made of Br-CD and N -aminomorpholine by substitution reaction. • HClO in milk, yogurt and meat samples were detected accurately (96.5 %–108 %). • • Br-CDs-AM can be used to locate lysosome and visualize HClO in live cells. Hypochlorous acid (HClO) is used in food preservation. However, excessive HClO can deteriorate nutritional composition of food, compromise its quality, and potentially induce various diseases. Consequently, the development of multifunctional fluorescent probes for the sensitive and selective detection of HClO is highly anticipated for food safety. In this work, we designed a nanoprobe using N -aminomorpholine (AM)-functionalized bromine-doped carbon dots (Br-CDs-AM) for sensing HClO. This nanoprobe exhibits pH stability, strong resistance to photobleaching, superior long-term photostability (12 weeks), high sensitivity (19.3 nM), and an ultrarapid response (8 s) for detecting HClO residues in food matrices with percentage recovery (96.5 %–108 %) and RSDs less than 5.34 %. In addition, extremely low cytotoxicity and outstanding biocompatibility enable the nanoprobe to be used primarily for lysosome tracking and rapidly visualizing HClO in live cells. Thus, this study provides a new pathway to design unconventional nanoprobes for food safety assessment and subcellular organelle-specific imaging HClO. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly sensitive and selective fluorescent probe (RH-C) for the detection of HClO in the living cells was developed. • Detail reaction mechanism of RH-C to HClO was proposed according to MS test. • Fluorescence imaging demonstrated that erastin-induced ferroptosis could increase HClO level in living cells. • Fluorescence imaging data demonstrated that VE could efficiently scavenge the endogenous HClO during ferroptosis. Ferroptosis is a burgeoning iron-dependent cell death form, and has close relation with hypochlorous acid (HClO). Exploring the fluctuation of the HClO level in living cells during ferroptosis could contribute to the profound study of the biological functions of HClO during ferroptosis. Here, we present a turn-on probe (RH-C) for the imaging of intracellular HClO during ferroptosis. The probe RH-C utilized the N,N -dimethylthiocarbamate group as a selective recognition site for HClO, and displayed desirable sensitivity and selectivity to HClO. The probe RH-C could detect the exogenous and endogenous HClO in living cells. Furthermore, RH-C was competent in monitoring the changes of endogenous HClO level during the process of ferroptosis. Biological imaging results suggested that erastin-induced ferroptosis can result in the excessive production of the endogenous HClO, and ferrostatin-1 (Fer-1) and vitamin E (VE) could block the massive accumulation of HClO in living cells. [ABSTRACT FROM AUTHOR]

The haloform reaction is one of the earliest named reactions in the field of organic chemistry. However, despite its long and rich history, the utility of this named reaction in chemosensing systems is unexplored to date. Herein, we adapt this named reaction and integrate it with the typical spirocycle ring-opening reaction of rhodamines to develop a new fluorescent probe (RCK-Cl) for hypochlorous acid (HOCl). Probe RCK-Cl has a α-chloro-α-cyanoketone (COCClCN) caging group incorporated into a spiro-9 H-xanthene fragment, and exists in the colorless, nonfluorescent spirocyclic form in aqueous solution. Upon treatment with HOCl, RCK-Cl undergoes a chlorination to give RCK-2Cl , which is unstable and undergoes spontaneous hydrolysis to form rhodamine B, thereby affording a fluorescence turn-on response. Due to the unique HOCl-induced chlorination involved in the sensing process, RCK-Cl exhibits exceptional specificity towards HOCl over other reactive oxygen/nitrogen species. The new probe features fast response, high sensitivity toward HOCl, and can not only track the fluctuations of endogenous HOCl within living cells but also visualize the production of HOCl generation in acetaminophen (APAP)-induced liver injury in the zebrafish model. This study provides a new strategy for creating HOCl probes to interrogate its function in biological phenomena. [Display omitted] • A rhodamine-based turn-on fluorescent probe for HOCl was designed and synthesized. • The probe was constructed by integrating the haloform-type reaction with the spirocyclic ring-opening of rhodamines. • The probe has a α-chloro-α-cyanoketone (COCClCN) caging group incorporated into a spiro-9 H-xanthene fragment. • The probe exhibits excellent selectivity toward HOCl. • The probe has been shown to visualize the HOCl generation in the APAP-induced liver injury in the zebrafish model. [ABSTRACT FROM AUTHOR]

Some biological small molecules such as hydrogen sulfide (H 2 S) and hypochlorous acid (HClO), play pivotal roles in numerous biological and pathological processes and are associated with various diseases. The detection and monitoring them is of continued research interest. Here we report a sequential detection mode fluorescence probes that allow for the sensing of HS– and ClO–. The mixture of P and HS– constructs a specific sensing system S for ClO–. The substitution product S is stable in air, which also could be used independently. Mechanism studies demonstrate that HS– substitutes the Cl atom in P. Furthermore, the addition of ClO– facilitates a ring-forming reaction, resulting in the formation of a thiofuran ring within the product (T). Interestingly, P has a highly ordered steric packing and could self-assemble into a rice-spike-like structure. Upon the addition of HS–, the assemblies decompose into free molecules. After interaction with ClO–, these molecules further transform to T with strong assembled capacity, featuring a larger number of nanosheets. This study provides a novel mechanism for sensing HS– and ClO–, cell and living animal imaging further indicating the good application prospects of these probes in biosensing and bioimaging. [Display omitted] • Three fluorescent probes for detection HS– and ClO– in sequence were developed. • The responsiveness to ClO– is based on the thiofuran ring-forming reaction. • The self-assembly may play positive roles in the detection of HS– and ClO–. • These probes were applied as HS− and ClO− imaging in living cells and mice. [ABSTRACT FROM AUTHOR]

Herein we developed a cascade detection mode for the detection of HS− and ClO− by the novel probe NM-Cl bearing a conjugating naphthalene-dicyanoisophorone unit. The probe displayed sensitive and remarkable fluorescent enhancement in response to HS−, but not to other analytes. The mixture of probe and HS− constructed a specific sensing system for ClO− by fluorescent quenching response. The mechanism studies indicated that the successive reacting of HS− substitution Cl atom in probe and then addition of ClO− facilitation a thiofuran ring-forming induced differentiated fluorescence emission. This study provides a novel mechanism for the detection of HS− and ClO−, the imaging of cell and living animal further indicating the good application prospects of the probe in biosensing and bioimaging. A highly specific and visible method for cascade detection HS− and ClO−. The substitution reaction of the Cl atom by SH group facilitates sensitive detection toward HS−. The responsiveness to ClO− is based on the thiofuran ring-forming reaction, which providing a brand-new mechanism for sensing ClO−. This cell and living animal imaging indicating the good application prospects of these probes in biosensing and bioimaging. [Display omitted] • A novel fluorescent probe for cascade detection of HS− and ClO− was developed. • The responsiveness to ClO− is based on the thiofuran ring-forming reaction, which provides a band-new mechanism for sensing ClO−. • The application of the probe in living cells and mice imaging reveal its potential for HS− and ClO− sensing. [ABSTRACT FROM AUTHOR]

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. 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. 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 facile near-infrared (NIR) probe NOF3 was designed and exhibited excellent sensitivity and selectivity toward HClO, the probe was successfully applied to visualize endogenous and exogenous HClO in living cells and mice. [Display omitted] • A facile HClO-activated NIR probe NOF3 was designed based on rhodamine skeleton. • Excellent sensitivity and selectivity of NOF3 towards HClO with a low detection limit of 0.146 μM. • The NOF3 can measure endogenous and exogenous HClO in living cells. • Successful application of NOF3 to visualize HClO in inflamed mice. [ABSTRACT FROM AUTHOR]

Herein, a red‐emitting fluorescent probe DM‐BDP‐OCl containing a para‐DMTC benzyl pyridinium moiety at the meso position of BODIPY as self‐immolative portion for the detection of HOCl was designed and synthesized. DM‐BDP‐OCl exhibited excellent specificity and a fast response for HOCl beyond other ROS/RNS. It was used for the accurately measurable detection of HOCl with a linear range from 0 μM to 50 μM, and the detection limit for HOCl reached 60 nM. Moreover, the probe could directly monitor fluctuations of exogenous and endogenous HOCl in living HeLa and RAW 264.7 cells. This work provided a powerful and convenient imaging tool for probing pathological and physiological actions of HOCl. [ABSTRACT FROM AUTHOR]

Hypochlorite (HClO) is involved in various physiological and pathological processes as well as regulation of lysosomal functions. Thus, it is appreciated to develop efficient molecule tools for precisely detecting HClO in lysosomes. Although several lysosomal-targetable fluorogenic probes for HClO have been developed to date, they still suffered from the discounted sensing performance under lysosomal acidic condition. Herein, on the basis of the "AND" logic gate strategy, a novel dual-activatable fluorogenic probe CS has been rationally designed by simultaneously incorporating HClO recognition site and pH-sensitive group with lysosomal-targetable characteristic into a coumarin fluorophore. Different from the single-activated ones previously reported, CS exhibited good sensitivity, high specificity and fast response towards HClO under the acidic conditions but was out of operation in the neutral or alkaline environment. Importantly, it had been successfully applied for spatial-resolution imaging of exogenous or endogenous HClO in lysosomes. A novel dual-activatable fluorogenic probe CS has been rationally designed. This probe exhibited good sensitivity, high specificity and fast response towards HClO under the lysosomal acidic conditions, and it has been successfully applied for visualizing exogenous or endogenous HClO in lysosomes of living cells. Image 1 • A novel dual-activatable fluorescent probe CS for HClO and acidic condition was rationally designed. • The probe exhibited good sensitivity, high specificity and fast response towards hypochlorous acid. • The probe was applied to detect exogenous and endogenous hypochlorous acid in living cells. • The probe demonstrated an excellent lysosome-targetable ability. [ABSTRACT FROM AUTHOR]

Ferroptosis is a non-apoptotic form of cell death characterized by iron-dependent lipid peroxidation and glutathione (GSH) depletion. Despite recent advances, challenges remain in understanding the bidirectional interactions or interplay between organelles during ferroptosis. In this study, we aimed to understand the interplay between mitochondria (Mito) and lysosomes (Lyso) in cell homeostasis and ferroptosis. For this purpose, we designed a single fluorescent probe that marks GSH in Mito and hypochlorous acid (HOCl) in Lyso with two distinct emissions. Using this dual-targeted single fluorescent probe (9-morphorino pyronine), we detected Mito-Lyso interplay in ferroptosis. We disclosed differences in Mito-Lyso interplay depending on the induction of ferroptosis. Although erastin treatment decreased GSH, RSL3 triggered a HOCl burst, and FIN56- and FINO2-induced ferroptosis increased GSH and HOCl. Additionally, we showed that only extracellular vesicles generated during erastin-induced ferroptosis could spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [Display omitted] • Simultaneous tracking of the GSH level in mitochondria (Mito) and the HOCl level in lysosomes (Lyso), respectively • Detected distinct Mito-Lyso interplay dynamics and GSH-HOCl crosstalk in ferroptosis • Diverse extracellular vesicle (EV) dynamics in different ferroptosis pathways • Spontaneous movement and docking of the EV accelerate neighboring cell death Wang et al. show the different dynamics of mitochondria-lysosome interplay in the four ferroptosis pathways. They identify diverse extracellular vesicles (EVs) in ferroptosis, of which only erastin-induced EVs can spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescent probe WZ-HOCl for detecting HOCl was designed. • WZ-HOCl could quantitatively detect HOCl with high sensitivity. • WZ-HOCl can distinguish normal hepatocytes and hepatoma cells by detecting HOCl. • WZ-HOCl was successfully used for imaging HOCl in inflammatory and liver disease models. Hypochlorous acid (HOCl) is a common reactive oxygen species (ROS) associated with the development of liver, tumor, inflammatory, and other diseases. In this work, the turn-on fluorescent probe named (WZ-HOCl) with a naphthalimide structure was designed and synthesized to detect endogenous HOCl in disease models. WZ-HOCl can achieve a fast response to HOCl with good linearity in the range of 0–45 μM (LOD = 147 nM). The application of WZ-HOCl in bioimaging was investigated by constructing a series of cellular disease models, and the results showed that WZ-HOCl could sensitively detect endogenous HOCl in inflammatory and liver disease models. It can also be used to differentiate between hepatocytes and hepatoma cells. WZ-HOCl will provide new methods and ideas for fluorescent probes in detecting drug-induced liver injury, alcoholic and non-alcoholic steatohepatitis, and some inflammation-related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new benzobodipy based fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity with a fast response to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Hypochlorous acid (HOCl) is a significant reactive oxygen species within biological systems, and its anomalous metabolism has been linked to a range of diseases. Therefore, it is crucial to track and monitor the concentration of HOCl in living organisms to understand its biological functions and study its pathogenic mechanisms. In this study, we developed a photoinduced electron transfer (PeT) mechanism-based benzo-fused bodipy fluorescence probe, named BBy-Se , for highly sensitive and selective detection of HOCl in aqueous solutions. BBy-Se demonstrated a good turn-on fluorescence response to HOCl by specifically oxidizing the selenium atom. It exhibited significant Stokes shift (82 nm), low detection limit (10.9 nM) and rapid response (less than 10 s). Furthermore, the probe was successfully employed for real-time fluorescence imaging of HOCl in living HeLa cells and zebrafish, as demonstrated by the bioimaging results. The development of BBy-Se presents a new approach to explore the biological roles of HOCl and offers a valuable tool for studying its function in diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A FRET based ratiometric fluorescent probe was developed for the detection of HClO. • Probe 1 displayed a short response time, a low detection limit and a large Stokes shift. • Probe 1 was an effective fluorescent tool to image HClO in living cells and zebrafish. Hypochlorous acid (HClO) is a reactive oxygen species and a relatively strong antibacterial substance in the immune defense system. The normal concentration of HClO in the human body is approximately 200 μM, and its high concentration can cause tissue damage and some diseases. Herein, a chromenoquinoline-based ratiometric fluorescent probe was developed to detect and quantify HClO. The developed Probe 1 exhibited the advantages of large Stokes shift (137 nm), high synthetic yield (84.7 %), simple synthesis method, short response time (<4 min), low detection limit (5.1 nM), and low toxicity. The probe was successfully validated in live cells and zebrafish. [ABSTRACT FROM AUTHOR]

An ICT fluorescence probe PIP-AH for colorimetric detection of hypochlorous acid and its applications in water samples and living cells. [Display omitted] • A novel fluorescent probe (PIP-AH) of HClO with ultrarapid-response (within 5 s), low detection limit (57.66 n mol·L–1) and the distinct colorimetric change (from green to blue) was synthesized. • PIP-AH can make into the portable test papers for colormetric determining HClO conveniently and be directly applied to detect HClO content in various actual water samples. • This probe was qualified for monitoring the variation of HClO levels in HeLa cells. Hypochlorous acid (HClO)/hypochlorite (ClO–) gets involved in many physiological and pathological processes. Although there is a lot of work that has been specifically reported in response to HClO, the ultrafast and colorimetric detection of HClO in the living body remains a challenge. Herein, we designed and synthesized a novel fluorescent probe PIP-AH based on the intramolecular charge transfer (ICT) mechanism, which showed an ultrarapid-response (within 5 s), the low detection limit (57.66 n mol·L–1) and the distinct colorimetric change (from green to blue) toward HClO titration in water solution. PIP-AH can make into the portable test papers for colorimetric determining HClO conveniently. Moreover, PIP-AH can be directly applied to detect HClO content in various actual water samples. Significantly, this probe was qualified for monitoring the variation of HClO levels in HeLa cells. [ABSTRACT FROM AUTHOR]

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 (Φ f = 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. Unlabelled Image • A water-soluble BODIPY dye with bis(4'-methylmercaptophenoxy) on the boron atom for the detection of HClO was reported. • The probe displayed highly sensitive response to HClO. • The probe could sense HClO in living cells. [ABSTRACT FROM AUTHOR]

• A novel water-soluble fluorescent probe with a large Stokes shift (about 115 nm) for detecting HOCl was designed. • The probe exhibited a remarkable fluorescence enhancement (˜ 227-fold). • The probe showed ultrasensitivity (DL = 3.30 nM) and fast response (<5 s) for HOCl. • The probe was successfully applied in tracking basal HOCl in living cells and zebrafish. Hypochlorous acid (HOCl) as a biologically important reactive oxygen species (ROS) plays crucial roles in the physiological and pathological processes. It is thus meaningful to explore an effective method for detecting basal HOCl in living systems. We herein report a large Stokes shift (about 115 nm) fluorescent probe LSS-HA for highly specific and ultrasensitive detection of HOCl with excellent water-solubility. Probe LSS-HA exhibited a remarkable fluorescence enhancement (˜ 227-fold) due to the adoption of high-quantum-yield fluorophore in aqueous solution. Besides, probe LSS-HA showed ultrasensitivity (detection limit is 3.30 nM) and fast response (<5 s) for HOCl. Furthermore, probe LSS-HA was successfully applied for imaging basal HOCl in living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Highlights • A "light-up" probe for ClO− based on TEMPO-oxidation was synthesized for the first time. • The probe showed high selectivity and sensitivity for ClO− with a LOD of 63.7 nM. • The detection mechanism was based on intermolecular-cyclization reaction. Abstract A highly selective and sensitive fluorescence "light-up" probe PTH for ClO− has been developed, which is designed by a new strategy based on TEMPO-oxidation for the first time. PTH exhibits excellent properties including quick response (within 2 min), lower detection limit (63.7 nM), good linearity (R 2 = 0.9863) and specific selectivity. More importantly, its application of detection ClO- in real samples has also been achieved. [ABSTRACT FROM AUTHOR]

Abstract It is of great significance to design a single probe, which can detect two different types of analytes. Herein, we synthesized the first dual-function fluorescent probe (probe FSQTZ) for the detection of water content and hypochlorite (ClO−) under different excitation wavelengths. The probe itself had strong fluorescence in four dry organic solvent, and the increase of water content could cause its fluorescence quenching and fluorescence color change. The probe was especially responsive to water in acetone (LOD = 0.014 wt %), and it can be employed to detect tiny amounts of water in commercial products such as aginomoto, salt, dried jasmine, and dried dates. Meanwhile, probe FSQTZ can selectively detect ClO− in aqueous solution with a remarkable large Stokes shift (168 nm), a rapid response time (within 10 s), an obvious change of color, a wide pH range of response, and it was also applied for imaging ClO− in PC12 cells. Furthermore, the CIE 1931 chromaticity diagram was successfully used to show the accurate color changes of probe. Graphical abstract Image 1 Highlights • The first dual-function fluorescent probe for the detection of water content and ClO− was designed. • The probe was especially responsive to water in acetone solution (LOD = 0.014 wt %). • The probe can quickly (within 10 s) detect ClO− with a large Stokes shift (168 nm). • The probe can detect water content in commercial products and image ClO− in living cells. [ABSTRACT FROM AUTHOR]

Abstract Hypochloric acid (HClO) is mainly distributed in acidic lysosomes of phagocytes and closely associated with numerous physiological and pathological processes, especially inflammatory response. Fluorescent probe has become an important tool for imaging HClO in lysosomes, but suffered from interference from autofluorescence in vivo , phototoxicity to biosamples and photobleaching phenomenon due to their short-wavelength excitation and emission. Unfortunately, up to now, no near-infrared (NIR) lysosome-targetable fluorescent probe has been reported for imaging HClO. In this paper, a near-infrared fluorescent probe Lyso - NIR - HClO for imaging lysosomal HClO was reported for the first time. Lyso - NIR - HClO based on Si-rhodamine is consisted of a morpholine unit as a lysosome-targetable group and a HClO-mediated cyclization reaction site as a response group, which was applied for highly selective and sensitive detection and imaging for endogenous and exogenous HClO in lysosomes, with a linear range from 5.0 × 10−8 to 1.0 × 10−5 M and a detection limit of 2.0 × 10−8 M in vitro. Attributed to NIR emission and excellent photostability of Si-rhodamine, Lyso - NIR - HClO exhibits excellent performances in vivo , such as low interference from intracellular autofluorescence, stable and persistent fluorescence signal and good tissue penetration, which are in favor of accurate, time-lapse and long-term imaging for HClO. Finally, we applied the probe Lyso - NIR - HClO to visualize endogenous HClO during lysosome-involved inflammatory response including bacteria-infected cells and inflamed mouse model with satisfactory results. The above results proved that Lyso - NIR - HClO would be a potentially useful tool for the study of biological functions and pathological roles of HClO in lysosomes, especially role of lysosome in the inflammatory response. Graphical abstract Image 1 Highlights • A near-infrared fluorescent probe for imaging lysosomal HClO, Lyso - NIR - HClO , was reported for the first time. • Lyso-NIR-HClO exhibited excellent performances in vivo based on NIR emission and excellent photostability of Si-rhodamine. • Lyso-NIR-HClO was successfully applied to visualize endogenous HClO during lysosome-involved inflammatory response. [ABSTRACT FROM AUTHOR]

Abstract A dual-functional fluorescent probe based on coumarin fluorophore for monitoring ClO− and Cu2+ was synthesized and characterized. The identification mechanisms for ClO− and Cu2+ induced different colorimetric and ratiometric changes. ClO− caused a colorimetric change from yellow to colorless and 120 nm blue-shifted emission spectra from red to blue. Besides, Cu2+ induced a remarkable fluorescence quenching behavior and 36 nm blue-shifted absorption spectra accompanied by the color change from yellow to luminous yellow. As expected, Probe 1 displayed excellent selectivity and sensitivity for detecting ClO− and Cu2+ over other competing ions in their respective systems. The limits of detection for ClO− and Cu2+ were 24.62 nM and 0.39 nM, respectively. The recognition mechanisms were proved by 1H NMR, mass spectrum and theoretical calculations. More importantly, the reversibility of Cu2+ could be applicable to rapid quantification for ClO−/Cu2+. Thus, the strategy for sensing ClO−/Cu2+ was carried out, which revealed broad applications of Probe 1 in multiple actual water and biology. Graphical abstract Unlabelled Image Highlights • A novel coumarin-based fluorescent probe for multiple ions was achieved. • The probe can distinguish ClO− and Cu2+ in different mixed solutions by adjusting the cyclic reversibility of Cu2+. • The probe showed rapid responses for ClO− and Cu2+ in multiple real water with high sensitivity and selectivity. • The probe can be used to monitor exogenous ClO− and Cu2+ in organisms. [ABSTRACT FROM AUTHOR]

Abstract In this paper, two simple probes (L1 and L2) have been designed and synthesized for detection of ClO− with large Stokes shifts (about 200 nm). Both probes can react with ClO− in less than one min and display obvious changes in fluorescence, which showing potential ability of detection ClO− in real time. ES-MS analysis was utilized to confirm our design strategy and the possible detection mechanism. Owing to the delicate difference of structure of two probes, L2 has a significant fluorescence ratio response to ClO− and the fluorescence of L1 is quenched. L1 has a longer emission wavelength, better response characteristics and weaker cytotoxicity (IC 50 28.1 μM) as compared with L2. The detection limit of L1 is even as low as 0.09 μM. What's more, it is successfully used in monitoring ClO− real water samples and in living cells. Graphical abstract Image 1 Highlights • Two fluorescent sensors with 1,3,4-thiadiazole and 2-(2'-hydroxyphenyl) benzoxazole moiety was designed to detect hypochlorite. • DFT calculations were used to assist designing these sensors. ES-MS analysis was used to confirm our design strategy and the detection mechanism. • Both sensors had large Stokes shifts and shown very low detection limit, fast and highly selective fluorescence response to ClO−. • The sensor L1 could successfully apply for the determination of ClO− in real water samples and in living cells. [ABSTRACT FROM AUTHOR]

Abstract Hypochlorous acid (HClO), one of the most important reactive oxygen species (ROS), is a potent antimicrobial agent for the immune system against invasive bacteria and a wide range of pathogens. Therefore, it is critical to develop sensitive and selective methods for visualization of HClO in biological samples. In this work, a two-photon fluorescent probe HN2-TP) with long-wavelength emission (far-red: 630 nm) based on rhodamine analogue for bioimaging HClO was developed. Owing to a specific HClO induced cyclization reaction, the new probe shows large fluorescence enhancement (about 106-fold), good linear range with high sensitivity (detection limit: 40 nM), high selectivity and fast response when monitoring HClO in vitro. More importantly, by successfully imaging HClO in living cells and tissues, this kind of two-photon fluorescent probe with long-wavelength emission is expected for accurate sensing in complex biosystems, which could eliminate undesired autofluorescence and self-absorption. Graphical abstract A novel two-photon fluorescent probe with long-wavelength emission is developed for highly sensitive and selective monitoring HClO in living cells and tissues. fx1 Highlights • Hypochlorous acid (HClO) is a potent antimicrobial agent for the immune system. • A long-wavelength two-photon probe was developed for bioimaging HClO in vivo. • This two-photon probe may present new avenues for accurate sensing applications. [ABSTRACT FROM AUTHOR]

Abstract We present a lysosome-targetable and ratiometric fluorescent probe, TJ2 , for visually monitoring exogenous and endogenous HOCl in living cells by using a built-in S atom within the π-extended rhodamine fluorophore as a pH-independent recognition site. Based on the oxidation-promoted intramolecular charge transfer processes, TJ2 demonstrates fast ratiometric fluorescence response, excellent selectivity, and high sensitivity (2.3 nM) toward HOCl. Furthermore, TJ2 is highly lysosome-targetable, which could be used for ratiometric monitoring of the levels of HOCl in lysosomes. Graphical abstract A ratiometric lysosome-targetable fluorescent probe has been designed and synthesized for the sensitive and selective detection of HOCl. Image 1 Highlights • A ratiometric probe TJ2 has been synthesized for lysosomal HOCl imaging. • The probe showed fast fluorescence response, excellent selectivity, and high sensitivity (2.3 nM) toward HOCl. • The probe could be used for ratiometric monitoring of the level of lysosomal HOCl in living cells in real time. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new AIE based fluorescent probe for monitoring the level of ClO− in PBS solution is constructed. • A LOD of 13.2 nM was calculated for ClO− in aqueous buffer solution. • The probe exhibits two-photon excitation performance since its fluorescence was observed under excitation by an NIR light. • The probe can be applied for detection of ClO− in solution, aggregated forms, solid state and living cells. Abstract We report here a brand new AIE based fluorescent probe (MTPA-Cy) for monitoring the level of ClO−. MTPA-Cy was synthesized via condensation reaction of 3-ethyl-1,1,2-trimethyl-1H-indolium iodide with 4-(bis(4-methoxyphenyl)amino)benzaldehyde, in which indole quaternary salt was incorporated as the mitochondria-target and 4-(bis(4-methoxyphenyl)amino)benzene (TPA) the AIE-active fluorescent reporter. Oxidation by ClO− of the ethylene bridge between TPA unit and indole quaternary salt moiety triggered substantial absorption and fluorescence changes. Upon introduction of ClO−, absorption of MTPA-Cy at 538 nm declined while a new absorption at shorter wavelength around 365 nm developed, manifested by an obvious color change from red to colorless, and fluorescence at 514 nm increased by 16.3-fold under excitation of 365 nm which means a large Stokes shift of ca. 150 nm. A LOD of 13.2 nM was calculated for ClO− in aqueous buffer solution, allowing thereby for detection of ClO− in a wide variety of biological systems. The oxidation product also exhibits two-photon excitation performance since its fluorescence was observed under excitation by an NIR light of 730 nm. MTPA-Cy was applied for detection of ClO− in solution, aggregated forms, solid state and living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new benzobodipy-based HOCl fluorescent probe has been designed and developed. • The probe exhibits an excellent sensitivity and low detection limit to HOCl. • The probe could be applied for real-time fluorescence imaging of HOCl in live cells and zebrafish. Hypochlorous acid (HOCl) is an essential endogenous reactive oxygen species in biological systems, playing a critical role in various physiological processes. Real-time monitoring of HOCl concentration in living organisms is essential for understanding its biological functions and pathological roles. In this study, we developed a novel fluorescent probe based on benzobodipy, BBDP , for rapid and sensitive detection of HOCl in aqueous solutions. The probe exhibited a significant fluorescence turn-on response to HOCl based on its specific oxidation reaction towards diphenylphosphine, with high selectivity, instantaneous response (less than 10 s), and low detection limit (21.6 nM). Furthermore, bioimaging results illustrated that the probe could be applied for real-time fluorescence imaging of HOCl in live cells and zebrafish. The development of BBDP may provide a new tool for exploring the biological functions of HOCl and its pathological roles in diseases. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) is a crucial reactive oxygen species in biological systems, and its abnormal metabolism is associated with various diseases. Therefore, it is essential to accurately detect HOCl to understand its biological function and develop related therapeutic strategies for diseases. In this work, we developed a novel fluorescence probe, BCy-S , based on the twisted intramolecular charge transfer (TICT) mechanism for rapid and sensitive detection of HOCl in an aqueous solution. The probe exhibited a significant turn-on fluorescence response to HOCl, with high selectivity, rapid kinetics (less than 40 s), large Stokes shift (about 170 nm), and low detection limit (35.2 nM), based on the specific oxidation reaction of HOCl with sulfur atoms. Additionally, the outcomes of the bioimaging experiment showed that BCy-S was capable of real-time fluorescence visualization of HOCl in living HeLa cells and zebrafish. The development of BCy-S presents a new tool for investigating the physiological function of HOCl and its pathological role in diseases. [Display omitted] • A new TICT-based HOCl fluorescent probe has been designed and developed. • The probe exhibits an excellent sensitivity, large Stokes Shift and low detection limit to HOCl. • The probe could be applied for real-time fluorescence imaging of HOCl in live HeLa cells and zebrafish. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO) is a reactive oxygen species (ROS) that plays a critical role in numerous pathological and physiological processes. Abnormal concentrations of HClO in vivo have been closely linked to many diseases, including inflammatory disorders and cancer. In this work, an on-off fluorescent probe PTZ based on phenothiazine was synthesized for specific detection of HClO. PTZ demonstrated excellent selectivity, biocompatibility, rapid response, pH stability, and low limits of detection (5.2 nM). Furthermore, PTZ can detect both exogenous and endogenous HClO rapidly in living cells and zebrafish, which provides it with broad potential applications in life sciences. Rapid and sensitive phenothiazine-based fluorescent probe for detecting endogenous HClO in living cells and zebrafish. [Display omitted] [ABSTRACT FROM AUTHOR]

A simple Schiff base was prepared by mild condensation reaction between a coumarin fluorescent group and diaminomaleonitrile, and it could serve as an excellent fluorescent probe for fast detection of ClO− with high selectivity and sensitivity. Along with addition of ClO−, this probe fleetingly showed noteworthy “turn-on” phenomenon accompanied by an increase of fluorescence intensity and the change of emission color from yellow to blue. This change of fluorescence is so significant that it can be observed by the naked-eye under a handheld ultraviolet light of 365 nm. However, other common reactive oxygen species exhibited no or very little fluorescent response under the same conditions. The limit of detection of this probe toward ClO− had a sensitivity feature as low as 9.6 nM. On account of these excellent features of short response time, remarkable fluorescence and color signal changes, high sensitivity and selectivity, this probe was effectively used for the fluorescence detection of ClO− in water samples. The values of the relative standard deviation were between 1.41% and 2.91%. More importantly, this probe displays excellent imaging capability in cytoplasm as well as very low cell toxicity and was unambiguously applied to image ClO− in living cells.A fluorescent probe based on coumarin for detection of ClO- was successfully developed, which can besuccessfully used for the detection of ClO− in living cells and in water sample because of the excellentfeatures including short response time, remarkable fluorescence and color signal changes, high sensitivityand selectivity [ABSTRACT FROM AUTHOR]

A novel water-soluble fluorescent probe based on the removal of HON moiety was presented, which could monitor ClO − with rapid response and excellent selectivity. In physiological pH condition, a good linear balance between the fluorescence intensity and the ClO − concentration was found with high sensitivity (8.3 nM). Additionally, this probe could be immobilized on test strips, which exhibited visible changes under UV light illumination. Its outstanding performance made the successful application in water samples and RAW264.7 cells. [ABSTRACT FROM AUTHOR]

Due to the importance of hypochlorous acid (HClO) in biological and industrial, development of fluorescent probes for HClO has been an active research area. Here, a new red-emitting ratiometric fluorescent probe ( P ) was synthesized and well defined characterization via NMR, HR-MS, and fluorescence spectrum, which serves as a selective and sensitive probe for ClO − group. The probe showed a ratiometric fluorescent response to hypochlorite at the emission intensities ratio (I 480 /I 612 ) increasing from 0.28 to 27.46. The emission intensities ratio (I 480 /I 612 ) was linearly enhanced (I 480 /I 612  = 0.064 X + 0.096) with the ClO − concentration range from 1 to 30 μM. The detection limitation for ClO − in aqueous solution is 0.47 μM. Moreover, this biocompatible red-emitting ratiometric fluorescent probe was utilized to the fluorescence imaging of ClO − in living cells and Zebrafish. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe ( DAME ) for sensing hypochlorous acid (HClO) with excellent selectivity was presented. The fluorescent probe was composed of coumarin derivative as the fluorophore and dimethylcarbamothioic chloride group with a sulfide moiety as modulator. Additionally, the sulfide moiety would be oxidized by HClO, and then free dye of coumarin derivate was released and exhibited significant fluorescence. In addition, the probe could respond to HClO in solutions within 60 s and the limit of detection was down to 34.75 nM. Moreover, the probe was used for the detection of HClO in tap water through the home-made test paper. And confocal images confirmed that probe DAME could be used for recognizing HClO in living cells. [ABSTRACT FROM AUTHOR]

Monitoring native hypochlorous acid (HOCl) levels in living cells is of great significance because HOCl plays vital roles in various physiological and pathological processes. In this paper, we reported a novel biscoumarin-based two-photon fluorescent probe BCTP for monitoring native HOCl levels in living cells. Probe BCTP containing the recognition group of dimethylthiocarbamate moiety displayed preeminent selectivity towards HOCl over other various bioactive species (1 mM). Additionally, probe BCTP could quantitatively determine HOCl in the range of 0–3 nM with the detection limit of 27 pM. Moreover, probe BCTP could offer a promising tool for the real-time detection of HOCl (response time within 3 s). The potential applications of probe BCTP in the monitoring of native HOCl levels and the fluctuations of endogenous HOCl levels in living cells have been demonstrated by two-photon excitation microscopy with higher sensitivity. [ABSTRACT FROM AUTHOR]

It is extremely important and necessary to develop a highly sensitive and excellent selective fluorescence probe for detection of ClO − in living systems because the excess production of ClO − was related to a series of diseases. Herein, a novel turn-on colorimetric fluorescent probe ADT-MAM based on naphthalenone scaffold was successfully designed and synthesized for highly selective and sensitive detection of ClO − with fast response time, a large Stokes shift, low limit of detection and wide pH range in applications. Meanwhile, probe ADT-MAM allowed colorimetric detection of ClO − by naked eyes. Fluorescence titration experiments showed that the probe has an excellent linear relationship (R 2  = 0.9949) and a low detection limit of 0.15 μM. HOMO-LUMO energy based on density functional theory (DFT) has been calculated in order to provide a better understanding of optical property for ADT-MAM and DTC. Moreover, the probe could be applied to sense exogenous imaging of ClO − in HeLa cells and A549 cells with negligible cytotoxicity, cell membrane permeability and good biocompatibility. The success of subcellular imaging suggested that such a novel probe ADT-MAM could be applied to further reveal essential biological functions and pathological roles of ClO − in extensive biological systems. [ABSTRACT FROM AUTHOR]

Developing highly specific and ultrasensitive techniques for monitoring hypochlorous acid (HOCl) in the environment and living systems is very important to guarantee its safe use and disclose its diverse biological functions. We herein presented a simple water-soluble lysosome-targeted fluorescent probe TCRH for the detection of HOCl. Probe TCRH could sensitively monitor HOCl at the nanomolar levels with the detection limit of 0.12 nM. Additionally, probe TCRH with the response unit of thiocarbamate could selectively detect HOCl over other various analytes. Furthermore, probe TCRH showed an ultrafast response for HOCl (<3 s), implying that it could offer a real-time analytical assay of HOCl. Finally, probe TCRH was used for monitoring the basal lysosomal HOCl levels without exogenous stimuli and tracking the fluctuations of endogenous/exogenous HOCl levels in the lysosomes of live RAW 264.7 macrophage cells. [ABSTRACT FROM AUTHOR]

We report a benzo[ a ]phenoxazine-based far red-emitting probe which selectively senses reduced nicotinamide adenine dinucleotide (NADH) and its phosphate ester NADPH, the most indispensable coenzymes found in all living cells, with “ turn-off ” fluorescence response at 650 nm. The original probe can be regenerated quantitatively through oxidation using hypochlorous acid, a reactive oxygen species, which was accompanied by restored fluorescence at 650 nm. This probe was also applied for fluorescence imaging of NADH in HeLa cells. [ABSTRACT FROM AUTHOR]

Due to the prominent photochemical and photophysical properties, the benzofurazan (NBD) fluorophore is a popular platform for constructing fluorescencet sensors. We reported herein a strategy to tune the fluorescence of NBD by modulating the push-pull pairs on the benzene ring, and obtained two novel fluorescent probes, MeS-DMAB and EtS-DMAB , which can selectively detect hypochlorous acid (HOCl) over other reactive oxygen species in aqueous solution with a large stokes shift (∼170 nm). The synthesis and optical properties of these two probes were described. The reaction products of HOCl with MeS-DMAB were isolated and characterized. It turns out that oxidation of the thioether to the corresponding sulfoxide accounts for the turn-on fluorescence. Finally, the probe EtS-DMAB was successfully applied to image exogenous and endogenous HOCl in live cells. [ABSTRACT FROM AUTHOR]