AIE-based fluorescent probe designed with xanthone as a π-bridge for detecting of ClO- in pericarp and living cells.

The role of ClO- in the physiological functioning of organisms is significant. In this paper, the four fluorescent probes HONx (HON1, HON2, HON3 and HON4) were prepared based on oxyanthracene through the introduction of different substituents, and their photophysical properties were investigated, among which the AIE effect of HON1 was the most significant, and therefore the fluorescent "turn-off" ClO- probe HON1-CN was chosen to be prepared by constructing the ClO- recognition site hydrazone bond at HON1. The ClO- recognises the hydrazone group in the probe HON1-CN, and when the hydrazone bond is broken, the aldehyde group is released, generating HON1 with yellow fluorescence. The probe HON1-CN is highly selective and stable for the detection of ClO- with a detection limit of 0.48 µM and a more than 10-fold increase in fluorescence intensity when the fluorescence is 'switched on', and to a lesser extent, the probe is also very good for the detection of hypochlorite ClO- in the pericarp. Finally, HON1-CN has also been used to detect the presence of ClO- in HeLa cells and zebrafish.

Oxyanion-Sensitive Catalytic Activity of Ni(II)/Oxyanion Systems for Heterogeneous Organic Degradation: Differential Oxidizing Capacity of Ni(III) and Ni(IV) as High-Valent Intermediates.

This study demonstrated that NiO and Ni(OH)2 as Ni(II) catalysts exhibited significant activity for organic oxidation in the presence of various oxyanions, such as hypochlorous acid (HOCl), peroxymonosulfate (PMS), and peroxydisulfate (PDS), which markedly contrasted with Co-based counterparts exclusively activating PMS to yield sulfate radicals. The oxidizing capacity of the Ni catalyst/oxyanion varied depending on the oxyanion type. Ni catalyst/PMS (or HOCl) degraded a broad spectrum of organics, whereas PDS enabled selective phenol oxidation. This stemmed from the differential reactivity of two high-valent Ni intermediates, Ni(III) and Ni(IV). A high similarity with Ni(III)OOH in a substrate-specific reactivity indicated the role of Ni(III) as the primary oxidant of Ni-activated PDS. With the minor progress of redox reactions with radical probes and multiple spectroscopic evidence on moderate Ni(III) accumulation, the significant elimination of non-phenolic contaminants by NiOOH/PMS (or HOCl) suggested the involvement of Ni(IV) in the substrate-insensitive treatment capability of Ni catalyst/PMS (or HOCl). Since the electron-transfer oxidation of organics by high-valent Ni species involved Ni(II) regeneration, the loss of the treatment efficiency of Ni/oxyanion was marginal over multiple catalytic cycles.

Assessing Atherosclerosis by Super-Resolution Imaging of HClO in Foam Cells Using a Ratiometric Fluorescent Probe.

Atherosclerosis (AS) is the leading cause of cardiovascular disease. Foam cells, with elevated lipid droplets (LDs) and HClO levels, are the main components of the atherosclerotic plaques that are characteristic of AS. Super-resolution imaging can be used to visualize the distribution of LDs in foam cells at the nanometer level, facilitating the identification of LDs and HClO. In the present study, we report the development of a ratiometric fluorescent probe, SFL-HClO, for super-resolution imaging of LDs and HClO. Super-resolution imaging with this probe revealed the precise structure of LDs at the suborganelle level. Moreover, the fluorescence behavior of SFL-HClO on the surface of LDs verified its excellent performance in detecting HClO in the foam cells. SFL-HClO can sequentially and specifically respond to LDs and HClO via "turn-on" and ratiometric signal output, respectively, thus contributing to precise imaging of foam cells. Importantly, we demonstrate that SFL-HClO can be used to report on upregulated HClO in atherosclerotic plaques in the aorta of AS mice, providing a suitable fluorescent tool for early atherosclerotic disease assessment.

Visualizing lysosomes hypochlorous acid in Parkinson's disease models by a novel fluorescent probe.

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.

Probing the toxic hypochlorous acid in natural waters and biosystem by a coumarin-based fluorescence probe.

Since the onset of the SARS-CoV-2 pandemic in early 2020, there has been a notable rise in sodium hypochlorite disinfectants. Sodium hypochlorite undergoes hydrolysis to generate hypochlorous acid for virus eradication. This chlorine-based disinfectant is widely utilized for public disinfection due to its effectiveness. Although sodium hypochlorite disinfection is convenient, its excessive and indiscriminate use can harm the water environment and pose a risk to human health. Hypochlorous acid, a reactive oxygen species, plays a crucial role in the troposphere, stratospheric chemistry, and oxidizing capacity. Additionally, hypochlorous acid is vital as a reactive oxygen species in biological systems, and its irregular metabolism and level is associated with several illnesses. Thus, it is crucial to identify hypochlorous acid to comprehend its environmental and biological functions precisely. Here, we constructed a new fluorescent probe, utilizing the twisted intramolecular charge transfer mechanism to quickly and accurately detect hypochlorous acid in environmental water and biosystems. The probe showed a notable increase in fluorescence when exposed to hypochlorous acid, demonstrating its excellent selectivity, fast response time (less than 10 seconds), a large Stokes shift (∼ 102 nm), and a low detection limit of 15.5 nM.

Natural harmaline acts as novel fluorescent probe for hypochlorous acid and promising therapeutic candidate for rheumatoid arthritis.

Endogenous hypochlorous acid (HOCl) is one of the most important reactive oxygen species (ROS) and acts as a distinct biomarker that is involved in various inflammatory responses including rheumatoid arthritis (RA). Therefore, it's crucial to develop an efficient method for the tracking and analysis of HOCl levels in vivo. Natural products continue to be compounds of interest, because they not only offer diverse and specific molecular scaffolds but also provide invaluable sources for new drug discovery. Herein, we firstly demonstrated harmaline (HML), a natural alkaloid mainly found in Peganum harmala L, could be acted as a novel fluorescent probe for HOCl with exceptional precision and responsiveness. Remarkably, this probe not only specifically tracked HOCl levels in cells and inflammatory RA mouse models, but also exhibited effective anti-inflammatory effects on RAW264.7 cells and anti-proliferative effects on fibroblast-like synoviocytes. Furthermore, HML has the potential to alleviate LPS-induced inflammation by inhibiting the NF-κB signaling pathway. This study represents the first example of a natural product that can simultaneously act as a fluorescent probe for specific ROS and a promising therapeutic candidate for a specific disease, which will undoubtedly extend the application of fluorophore-rich natural products.

Ratiometric fluorescent probe with AIE characteristics for hypochlorite detection and biological imaging.

It is very important and highly valuable to detect ClO- in samples and living cells with accuracy and speed. In this work, a novel fluorescent probe NA was prepared from 4-bromo-1,8-naphthalic anhydride by acylation reaction and Suzuki coupling reaction and used for the detection of ClO-. Thiomethyl serves as the recognition group for probe NA, while naphthalimide serves as fluorescent chromophore. The probe exhibited an extremely pronounced blue shift from yellow to blue fluorescence within 1 min after the addition of hypochlorite (ClO-). The probe demonstrates high sensitivity to ClO- with a limit of detection (LOD) of 1.22 µM. Also, probe NA demonstrates excellent selectivity and immunity to interference. Additionally, simple fluorescent test strips containing probe NA were prepared in this study, enabling rapid detection of ClO- in water samples. And NA had been effectively used to image endogenous and exogenous ClO-fluorescence in living cells. The results suggest that probe NA has significant potential for portable detection and biological applications.

Hypochlorous Acid-Modified Serum Albumin Causes NETosis in the Whole Blood Ex Vivo and in Isolated Neutrophils.

Type 2 diabetes mellitus (T2DM) is accompanied by halogenative stress resulting from the excessive activation of neutrophils and neutrophilic myeloperoxidase (MPO) generating highly reactive hypochlorous acid (HOCl). HOCl in blood plasma modifies serum albumin (Cl-HSA). We studied the formation of neutrophil extracellular traps (NETs) in the whole blood and by isolated neutrophils under the action of Cl-HSA. It was found that Cl-HSA induces neutrophil priming and NETosis. MPO-containing as well as MPO-free NETs were found. These NETs with different composition can be a product of NETosis of one and the same neutrophil. NET formation in neutrophils with vacuolated cytoplasm was detected. In the presence of Cl-HSA, acceleration of NET degradation was observed. Accelerated NET degradation and neutrophil priming can be the factors contributing to the development of complications in T2DM.

Construction of a dual "off-on" near-infrared fluorescent probe for bioimaging of HClO in rheumatoid arthritis.

Hypochlorous acid (HClO) serves as a critical biomarker in inflammatory diseases such as rheumatoid arthritis (RA), and its real-time imaging is essential for understanding its biological functions. In this study, we designed and synthesized a novel probe, RHMB, which ingeniously integrates rhodamine B and methylene blue fluorophores with HClO-specific responsive moieties into a single molecular framework. Upon exposure to HClO, RHMB exhibited significant dual-channel fluorescence enhancement characterized by high sensitivity (LODs of 2.55 nM and 14.08 nM), excellent selectivity, and rapid response time (within 5 s). Notably, RHMB enabled reliable imaging of both exogenous and endogenous HClO in living cells and in zebrafish, employing a unique duplex-imaging turn-on approach that highlighted its adaptability across various biological contexts. Furthermore, RHMB effectively monitored HClO fluctuations in an RA mouse model and assessed the therapeutic efficacy of diclofenac (Dic) in alleviating RA symptoms. These findings underscore the potential of RHMB as an invaluable tool for elucidating the biological roles of HClO in various diseases.

Phosphodiesterase 4 is overexpressed in human keloids and its inhibition reduces fibroblast activation and skin fibrosis.

There is a pressing medical need for improved treatments in skin fibrosis including keloids and hypertrophic scars (HTS). This study aimed to characterize the role of phosphodiesterase 4 (PDE4), specifically PDE4B in fibrotic skin remodeling in vitro and in vivo. In vitro, effects of PDE4A-D (Roflumilast) or PDE4B (siRNA) inhibition on TGFß1-induced myofibroblast differentiation and dedifferentiation were studied in normal (NHDF) and keloid (KF) human dermal fibroblasts. In vivo, the role of PDE4 on HOCl-induced skin fibrosis in mice was addressed in preventive and therapeutic protocols. PDE4B (mRNA, protein) was increased in Keloid > HTS compared to healthy skin and in TGFß-stimulated NHDF and KF. In Keloid > HTS, collagen Iα1, αSMA, TGFß1 and NOX4 mRNA were all elevated compared to healthy skin confirming skin fibrosis. In vitro, inhibition of PDE4A-D and PDE4B similarly prevented TGFß1-induced Smad3 and ERK1/2 phosphorylation and myofibroblast differentiation, elevated NOX4 protein and proliferation in NHDF. PDE4A-D inhibition enabled myofibroblast dedifferentiation and curbed TGFß1-induced reactive oxygen species and fibroblast senescence. In KF PDE4A-D inhibition restrained TGFß1-induced Smad3 and ERK1/2 phosphorylation, myofibroblast differentiation and senescence. Mechanistically, PDE4A-D inhibition rescued from TGFß1-induced loss in PPM1A, a Smad3 phosphatase. In vivo, PDE4 inhibition mitigated HOCl-induced skin fibrosis in mice in preventive and therapeutic protocols. The current study provides novel evidence evolving rationale for PDE4 inhibitors in skin fibrosis (including keloids and HTS) and delivered evidence for a functional role of PDE4B in this fibrotic condition.

A ratiometric fluorescent probe for selective detection of hypochlorite (ClO-) and gallium (III) (Ga3+) ions in environmental and food samples.

Hypochlorite (ClO-) and gallium (Ⅲ) ions (Ga3+) have extensive applications in various human industries and daily activities. However, their inherent toxicity poses significant risks to environmental preservation and human well-being. Hence, the development of reliable and handy detection tools for ClO- and Ga3+ in the environment and food is crucial. In this study, a ratiometric fluorescent probe was prepared based on benzothiazolaldehyde and pyridine-2-carboxylic acid hydrazide, which exhibited exceptional performance characteristics for the selective detection of ClO- and Ga3+. These features include high specificity, low detection limits (0.28 µM for ClO-, 0.13 µM for Ga3+), mild pH conditions (pH 4-11 for ClO-, pH 6-11 for Ga3+), fast response time (within 30 s), as well as versatile applicability across different matrices such as water, soil, food, and plant samples. Additionally, this probe can be used with a smartphone color recognition app. The probe offers a convenient and effective tool for the detection of ClO- and Ga3+, demonstrating its potential application value in environmental monitoring and food safety.

Visualizing ClO- fluctuations in drug-induced liver injury and bacterium via a robust ratiometric fluorescent probe.

As a type of reactive oxygen species, hypochlorous acid (ClO-) plays an important role in sterilization, disinfection and protection in organisms. However, excessive production of ClO- is closely related to various diseases. In this work, we have designed a robust ratiometric fluorescent probe, RDB-ClO, using the excited-state intramolecular proton transfer (ESIPT) strategy. RDB-ClO was achieved by modifying 2-(2-(benzo[d]thiazol-2-yl)-6-(diethylamino)-3-oxo-3H-xanthen-9-yl) benzoic acid (RDB-OH) with a 1-naphthoyl chloride group, specifically for the sensitive detection of ClO-. In the presence of ClO-, RDB-ClO demonstrated relatively good performance, showing swift response time (35 s), low detection limit of 5.1 nM and high selectivity towards ClO-. Notably, the convenience and accessibility detection of ClO- has been implemented using test strip and agarose probe. RDB-ClO effectively tracked both endogenous and exogenous ClO- in HeLa cells, HepG2 cells and zebrafish. Additionally, it is successfully applied to detect changes of exogenous ClO- content in E. coli. and acetaminophen (APAP)-induced liver injury in mice. The development of RDB-ClO represents a promising molecular tool for studying the pathogenesis of DILI and biotransformation of ClO- in bacteria.

Levonorgestrel protected Au10 cluster for hypochlorite sensing in living organisms.

BACKGROUND: Highly reactive oxygen species (ROS) could lead to serious damage in living cells and are associated with many diseases like cancers. Metal cluster with strong fluorescence has great potential in biosensing and many thiolate ligands-protected clusters have been applied in ROS sensing. RESULTS: In this work, we synthesized levonorgestrel protected Au10 cluster with specific sensing ability for highly ROS via crystal transformation from Au8 cluster, demonstrating the significance of inner core structure on detecting performance. The detection limit of Au10 cluster for ClO- could reach as low as 0.1 µM. This fluorescent probe not only achieving detection of exogenous ClO- in living cells and zebrafish, but also successful imaging of endogenous ClO- in HeLa and HepG2 cells. SIGNIFICANCE: In comparison to previously reported cluster-based sensors for ROS, this work proposes a different reaction mechanism of metal nanoclusters for ROS detection (breakage of gold-alkynyl bond and oxidation of alkynyl group). This provides new directions for designing specific ROS probes and broadens the applications of metal clusters in disease diagnostics.

Win-win integration: A mitochondria targeted AIE photosensitizer for hypochlorite detection and type I & type II photodynamic therapy.

BACKGROUND: Photodynamic therapy (PDT) is a pioneering and effective anticancer modality with low adverse effects and high selectivity. Hypochlorous acid or hypochlorite (HClO/ClO-) is a type of inflammatory cytokine. The abnormal increase of ClO- in tumor cells is related to tumor pathogenesis and may be a "friend" for the design and synthesis of responsive phototherapy agents. However, preparing responsive phototherapy agents for all-in-one noninvasive diagnosis and simultaneous in situ therapy in a complex tumor environment is highly desirable but still remains an enormously demanding task. RESULTS: An acceptor-π bridge-donor-π bridge-acceptor (A-π-D-π-A) type photosensitizer TPTPy was designed and synthesized based on the phenothiazine structure which was used as the donor moiety as well as a ClO- responsive group. TPTPy was a multifunctional mitochondria targeted aggregation-induced emission (AIE) photosensitizer which could quickly and sensitively respond to ClO- with fluorescence "turn on" performance (19-fold fluorescence enhancement) and enhanced type I reactive oxygen species (ROS) generation to effectively ablate hypoxic tumor cells. The detection limit of TPTPy to ClO- was calculated to be 185.38 nM. The well-tailored TPTPy anchoring to mitochondria and producing ROS in situ could disrupt mitochondria and promote cell apoptosis. TPTPy was able to image inflammatory cells and tumor cells through ClO- response. In vivo results revealed that TPTPy was successfully utilized for PDT in tumor bearing nude mice and exhibited excellent biological safety for major organs. SIGNIFICANCE AND NOVELTY: A win-win integration strategy was proposed to design a tumor intracellular ClO- responsive photosensitizer TPTPy capable of both type I and type II ROS production to achieve photodynamic therapy of tumor. This work sheds light on the win-win integration design by taking full advantage of the characteristics of tumor microenvironment to build up responsive photosensitizer for in situ PDT of tumor.

A dual-functional NIR fluorescence probe for detecting hypochlorous acid and bisulfite in biosystem.

BACKGROUND: Bisulfite (HSO3-) serves as a bleaching agent, antioxidant, antimicrobial, and regulator of enzymatic reactions in biosystem. However, abnormal levels of bisulfite can be detrimental to health. Hypochlorous acid (HOCl), which acts as bioactive small molecules, is crucial for maintaining normal biological functions in living organisms. Disruption of its equilibrium can lead to oxidative stress and various diseases. Therefore, it's essential to monitor the fluctuations of HOCl and HSO3- at cellular and in vivo levels to study their physiological and pathological functions. RESULTS: This study constructed a novel NIR bifunctional colorimetric fluorescent probe using thienocoumarin-indanedione structures to identify hypochlorite (ClO-) and bisulfite (HSO3-). By using CSO-IO to recognize HSO3- and HOCl, two distinct products were generated, displaying green and blue fluorescence, respectively. This property effectively allows for the simultaneous dual-functional detection of HSO3- (LOD: 113 nM) and HOCl (LOD: 43 nM). SIGNIFICANCE: In this work, the biocompatible molecule CSO-IO has been effectively designed to detect HOCl/HSO3- in living cells and zebrafish. As a result, the dual-functional fluorescent probe has the potential to be utilized as a molecular tool to detect HSO3- derived compounds and HOCl simultaneously within the complex biological system.

A self-assembled nanoprobe for rapid detection of hypochlorite in pure water and its application in living cells, food and environmental systems.

As an important ROS species participating in various physiological and pathological processes, high level of hypochlorite (ClO-) poses significant health and safety concerns, necessitating efficient detection methods. Herein, this study introduces a water-soluble fluorescent nanoprobe Nano-SJD, effectively detect ClO- in both food samples and living cells. The small molecular probe SJD with N, N-dimethylthiocarbamyl (DMTC) as recognition moiety was constructed based on a naphthalene derivative. To further improve the water solubility, SJD was assembled with an amphiphilic copolymer (mPEG-DSPE) to prepare a water soluble fluorescent nanoprobe Nano-SJD. Fortunately, the nanoprobe preserves the excellent properties of small molecules and performs very well optical response to ClO- in aqueous solution, possessing the advantages including ultra-rapid response (within 1 s), minimal interference, low detection limits (0.39 µM) and good pH stability. What's more important, we have also developed smartphone-compatible test paper strips for convenient on-site detection of ClO- in real-water samples. Additionally, the robust fluorescent imaging behavior of Nano-SJD for visualization of ClO- in living cells highlights its broad potential in biosystem applicability.

A novel AIE-based mitochondria-targeting fluorescent probe for monitoring of the fluctuation of endogenous hypochlorous acid in ferroptosis models.

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.

Facile synthesis of long-wavelength emission carbon dots for hypochlorite sensing and intracellular pH imaging.

Hypochlorite (ClO-), a typical reactive oxygen species, plays an irreplaceable roles in various biological processes. In this work, long-wavelength emission carbon dots (LW-CDs) were fabricated through one-step hydrothermal method by using l-cysteine (cys) and neutral red (NR) as precursors for monitoring of hypochlorite and intracellular pH. Characterizations of as-prepared LW-CDs showed that they had excellent water solubility, high optical stability and sensitive response behavior. Fluorescence intensity of LW-CDs decayed in the presence of ClO- linearly from 10 to 162.5 µM (LOD = 1.021 µM) based on static quenching effect with ideal selectivity. Besides, LW-CDs revealed a pH responsive behavior in the pH range of 2.0 to 10.0, exhibited dual good linear relationships in the pH ranges of 4.2-5.8 and 5.8-7.4. The LW-CDs can also be utilized as imaging reagents in Hela living cells owing excellent biocompatibility and low cytotoxicity. These results demonstrated that the as-mentioned LW-CDs are expected to serve as excellent long wavelength emitting nanomaterials for fluorescence sensing and monitoring of cell fluctuations.

A cyanine based fluorescent probe for detecting hypochlorite in vitro and in vivo.

Hypochlorite (ClO-) is recognized as a bioactive substance that plays a crucial role in various physiological and pathological processes. The increase of ClO- content in cells is a key factor in the early atherosclerosis lesions, which are closely linked to cardiovascular and cerebrovascular diseases. Therefore, the development of an efficient and sensitive method for detecting hypochlorite in tap water, serum, and living cells, including animal model in vivo is of paramount importance. In this study, a novel fluorescent probe (Cy-F) based on the cyanine group was designed for the specific detection of ClO-, demonstrating exceptional selectivity, high sensitivity, and rapid response. The probe successfully detected ClO- in tap water and serum with a limit of detection (LOD) of 2.93 × 10-7 M, showcasing excellent anti-interference capabilities. Notably, the probe exhibited good biocompatibility, low biological toxicity, and proved effective for detecting and analyzing ClO- in live cells and zebrafish. This newly developed probe offers a promising approach and valuable tool for detecting ClO- with biosafety considerations, paving the way for the design of functional probes tailored for future biomedical applications.

Synthesis of non-modified near-infrared carbon dots for hypochlorite detection and cell membrane imaging.

Devising carbon dots with long wavelength emission (red light or near infrared), high selectivity and good bio-compatibility is critical in fluorescence detection and imaging, but achieving this goal remains a great challenge. Herein, near-infrared emissive carbon dots (NIR-CDs) with obvious emission characteristic of 653 nm were synthesized through hydrothermally treatment of toluidine bule and gallic acid. Noticeably, the NIR-CDs exhibited excellent selectivity and sensitivity to hypochlorite (ClO-), and the limit of detection is as low as 42.7 nM. The selective recognition reaction between ClO- and the surface functional groups of NIR-CDs inhibits the fluorescence from NIR-CDs. The quenching mechanism was confirmed by fluorescence lifetime decays, FT-IR spectroscopy and UV-vis absorption spectra. More remarkably, the NIR-CDs have rich hydrophilic groups showed lower cytotoxicity, excellent bio-compatibility and specific cell membrane localization ability. The established spectrofluorometric method based on NIR-CDs has been used to determination of ClO- level in tap water sample, the recoveries were 97.7 %-103.3 %. In addition, the NIR-CDs also has been successfully applied for the imaging of cell membrane. The study provides a novel idea for developing NIR ClO- probe as well as cell membrane localization probe based on CDs, which present bright prospects in real water samples monitoring and cell membrane imaging.