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Early treatment is the best choice for cancer treatment. But there are many difficulties in the early diagnosis of cancer. Fluorescent probes can be used to detect small molecules or proteins overexpressed in tumor cells as a screening tool for tumor cells. However, many analytes are not specifically expressed in tumor cells. Therefore, the sensitivity and accuracy are both limited. Previous studies have shown that hydrogen peroxide (H2O2) is overexpressed in tumor cells. Similarly, melatonin can effectively bind to G-protein coupled receptors (MT1 and MT2), which are also overexpressed in some types of tumor cells. Hence, we constructed a novel melatonin-based targetable H2O2 fluorescent probe for precisely screening tumor cells. The results showed that the proposed probe can successfully detect endogenous and exogenous H2O2 in living cells and zebrafish, and accurately screen tumor cells. Importantly, this work not only proves the potential targeting capability of melatonin for tumor cells, but also provides new strategy of targeting plus activation for tumor cells screening. Moreover, the proposed probe in this work can serve as a potential tool for early diagnosis of cancer.

Hydrogen sulfide (H2S), a recognized environmental pollutant, comes from a wide range of sources. For example, H2S will be produced in the process of plant protein corruption, the decomposition of domestic sewage and garbage, food processing (wine brewing), etc. and once the concentration is too high, it will cause significant damage of environment and human body. Besides H2S is an important gas signal molecule in vivo, which can be transferred through lipid membrane. Its existence level is closely related to many diseases. If we can “visually” trace the transmembrane transmission of hydrogen sulfide, it will be very helpful for the study of oxidative stress processes, cell protection, signal transduction and related diseases closely related to H2S. Although some probes can detect H2S in environment, cytoplasm and organelles, there are few reports on the release and internalization of H2S. In this work, we report a H2S fluorescence probe that can retain on the cell membrane, named PCM. The probe PCM can not only detect endogenous and exogenous H2S, but also distinguish them, this provides a general strategy for the construction of probes to detect other biomarkers. In addition, PCM has been successfully applied to the detection of endogenous and exogenous H2S in zebrafish, which has the potential to become a new chemical tool and provide help for the research of H2S-related diseases.

Development of selective fluorescent probes for rapid and ultrasensitive detection of nitroxyl (HNO) is of great importance for biomedical researchers to investigate the detailed functions and mechanisms of HNO in living systems. Herein, based on an internal charge transfer (ICT) mechanism, we developed a novel ratiometric, colorimetric and far-red fluorescent probe (HNO-TCF) for the rapid and ultrasensitive detection of HNO in living cells. HNO-TCF exhibits high HNO-selectivity even in the presence of a high concentration of biological reductants including glutathione (GSH), hydrogen sulfide (H2S) and ascorbate (AA), which might be ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. The ICT-based fluorescent probe HNO-TCF displays a large (185 nm) red-shifted absorption spectrum and the color changes from yellow to blue upon addition of HNO. In addition, the results showed that HNO-TCF could quantitatively detect HNO in the range of 0 to 4 μM with a detection limit of 10 nM by ratiometric absorption and fluorescence spectrometry methods. Importantly, HNO-TCF was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.

We have synthesized a simple Golgi-targeting H

Mercury (Hg) is a heavy metal with high toxicity and easy migration; it can be enriched through the food chain, and cause serious threats to the natural environment and human health. So, the development of a method that can be used to detect mercury ions (Hg

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 (

Currently, the fluorescent probe is an important method for detecting heavy metal ions, especially mercury ion (Hg2+ ), which is harmful to the health of humans and the environment due to its toxicity and extensive use. In this paper, we designed and synthesized a colorimetric and long-wavelength fluorescent probe Hg-P with high sensitivity and excellent selectivity, which could detect Hg2+ by the changes of visual color, fluorescence and absorption spectroscopy. With the addition of Hg2+ to probe Hg-P solution, its color changed from yellow to pink, and showed a 171 nm red-shifted absorption spectrum. Probe Hg-P was used in real water and soil solution samples to detect Hg2+ , and the result is satisfactory. Therefore, this new probe shows great value and application in detecting Hg2+ in the environment.

In recent years, targeting drugs made by physical loading or chemical bonding of drugs on small molecular carriers have shown a very wide application prospect in the field of tumor and cancer treatment. How to achieve the release of drugs in cancer cells has become the core of this research. One of the most important bases for drug localization is to use the difference of small molecular biothiol concentration between cancer cells and normal cells. Details of the changes of biothiol levels in the growth and reproduction of cancer cells are still poorly understood, and the main reason is the lack of sensitive real-time imaging tools for biothiols in cancer cells. In this work, we reasonably designed and synthesized the combination of 4-hydroxy-1,8-naphthalimide and NBD-Cl as a concise fluorescent probe HN-NBD for imaging biothiols in live cells and zebrafish. In addition, due to the advantages of HN-NBD design, it is sufficiently sensitive to biothiols, and further imaging can distinguish cancer cells from normal cells. Probe HN-NBD would be of great significance to biomedical researchers for the study of biothiol-related diseases, the screening of new anticancer drugs, and the early diagnosis and treatment of cancers.

Small molecular biothiols, such as cysteine (Cys), homocysteine (Hcy), reduced glutathione (GSH), and hydrogen sulfide (H2S), play crucial parts in regulating the redox balance of life activities, regulating normal physiological activities and preventing various diseases. Quantitative analysis of these important small molecular substances is very important for revealing their diverse physiological and pathological effects. Although many fluorescent probes have been reported to detect biothiols in cells, it is still not sufficiently advanced to detect biothiols with separated fluorescence emission peak by same wavelength excitation. In our work, we designed a simple conjugate of Nile red and NBD (7-nitro-1,2,3-benzoxadiazole) as long-wavelength fluorescent probe NR-NBD for the simultaneous discrimination of these biothiols at single wavelength excitation. Probe NR-NBD could efficiently discriminate Cys/Hcy, GSH and H2S by two separated fluorescence emission channels and absorption spectra. Importantly, probe NR-NBD has excellent specificity and sensitivity towards the monitoring of endogenous/exogenous Cys/Hcy and GSH/H2S in living cells and zebrafish.

Exploiting specific and sensitive techniques for tracking peroxynitrite (ONOO−) in the biological systems is of great significance to understand its diverse pathophysiology. Herein, we have constructed a simple, 4-hydroxynaphthalimide-derived two-photon fluorescent probe TPHQ for imaging ONOO− in live cells. Probe TPHQ with the recognition receptor of hydroquinone moiety exhibited excellent selectivity towards ONOO− over various bio-related analytes including H2O2 and OCl−. Additionally, probe TPHQ could rapidly monitor ONOO− with high sensitivity (DL = 16 nM). With probe TPHQ, the fluctuations of ONOO− levels in live cells were successfully tracked by the one-photon and two-photon fluorescence microscopy.

Highly specific and ultrasensitive fluorescent probes for tracking the intracellular native hypochlorous acid (HOCl) levels are urgently needed owing to its important molecular functions in the biological systems. In this contribution, a simple thiocarbamate-caged 7-hydroxycoumarin (TCHC) was developed as fluorescent probe for monitoring HOCl in live cells. Probe TCHC exhibited preeminent specificity towards HOCl over other various bioactive substances. Importantly, probe TCHC could sensitively detect HOCl in the range of 0–175 pM with the detection limit of 17 pM, which was attributed to the multiple fluorescence sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), and the chlorination. Furthermore, probe TCHC displayed an instant response towards HOCl (

It is still challenging to simultaneously distinguish general biothiols (cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) etc.) in complex redox environments, due to the lack of reliable and convenient method. Although a number of fluorescence and/or UV–vis absorption based measurements have been employed for single or multiple biothiols detection, few of them is capable of recognizing each biothiol with individual signal at the same time. We present a one-step obtained selenadiazole derivative (1) to distinguish Cys, Hcy and GSH, which not only can produce three new kind of fluorescent compounds, but also simultaneously induce different “turn-on” fluorescence emission and red-shifted absorption signals for discriminating each biothiol. With a series of systematically analyses elucidate that probe 1 possesses high sensitivity and good selectivity for the three biothiols. Furthermore, the detection mechanism was also verified via a stepwise selenium–nitrogen (Se N) bond cleavage process of probe 1 interacting with each biothiol. In the application of tracking in vitro and in vivo biothiols, probe 1 can be acted as a dual-mode fluorescent and colorimetric platform.

The development of highly specific and ultrasensitive fluorescent probes for tracking basal mitochondrial hypochlorite is very important to unravel its diverse cellular functions in the mitochondria of living cells. In this paper, we have developed a water-soluble, mitochondria-targeted near-infrared fluorescent probe NB-OCl for selectively measuring OCl- in the presence of higher concentration (500 μM) other biologically important substances. Surprisingly, the obtained results demonstrated that probe NB-OCl could sensitively determine OCl- in the range of 0-200 pM with the detection limit of 10.8 pM. To the best of our knowledge, NB-OCl is the first fluorescent probe for the specific determination of OCl- at the picomolar level. Moreover, probe NB-OCl exhibits a fast response for OCl- (< 5 s), which would be in favor of tracking the highly reactive and short-lived OCl- in the living systems. The preeminent recognition properties of probe NB-OCl enable its applications in the monitoring of basal OCl- and the fluctuations of endogenous/exogenous OCl- levels in the mitochondria of living cells.

Peroxynitrite (ONOO − ) is involved in various physiological and pathological processes. However the detailed mechanisms of ONOO − in the biological systems remain unclear, probably due to the lack of specific and sensitive methods for detecting ONOO − in living cells. Herein, based on the intramolecular charge transfer (ICT) mechanism, we have developed a highly specific and ultrasensitive ratiometric far-red fluorescent probe RFR-PN for monitoring ONOO − in living cells. Experimental results demonstrated probe RFR-PN possesses high specificity toward ONOO − than other various bioactive molecules. Probe RFR-PN could quantitatively and sensitively detect ONOO − with the detection limit of 0.9 nM by the ratiometric fluorescence method. Surprisingly, the fast response of probe RFR-PN for ONOO − ( − in the living systems. Moreover, probe RFR-PN was successfully applied to the fluorescence imaging of endogenous ONOO − in living cells.

The fluorescent probe has become an important method for the detection of heavy metal ions. In the present work, a new and simple fluorescent probe, Cu-P, for detecting copper ion (Cu2+) was designed and synthesized. The probe has shown high sensitivity and selectivity toward Cu2+. The detection limit was 13 nM (based on the 3σ/slope). A significant color change from yellow to pink was observed; thus, the probe Cu-P could serve as a "naked-eye" indicator for Cu2+. Furthermore, the proposed probe was used to detect Cu2+ in real water and soil extract samples, with the result being satisfactory. Therefore, our proposed probe would provide a promising method for the detection of Cu2+ in the environment.

The development of sensitive methods for imaging endogenous peroxynitrite (ONOO − ) in the mitochondria of living cells is very important to disclose its diverse physiological and pathological functions. In this paper, we have described a simple, mitochondria-targeted far-red fluorescent probe Mito-PN for selectively detecting ONOO − even though in the presence of higher concentration (1 mM) other biologically important substances. The experimental results indicated that probe Mito-PN could quantitatively determine ONOO − in the range of 0.5–8 μM with the detection limit of 17 nM. In addition, probe Mito-PN exhibits a fast response for ONOO − ( − in the biological systems. The excellent sensing properties of probe Mito-PN enable its applications in the tracking of the fluctuations of endogenous ONOO − levels in the mitochondria of living cells.

The sensitive and accurate detection of intracellular gasotransmitter carbon monoxide (CO) is of great significance for unraveling its diverse cellular functions. Herein, we report a simple highly specific and sensitive 4-hydroxynaphthalimide-based ratiometric fluorescent probe Ratio-CO for monitoring CO levels in living cells. Probe Ratio-CO could quantitatively detect CO in the range of 0–50 μM by the ratiometric fluorescence spectroscopy method and the detection limit was measured to be about 17.9 nM. Additionally, probe Ratio-CO has been proven to possess preeminent selectivity towards CO over other bioactive species. Most importantly, the excellent response properties of probe Ratio-CO enable its applications in the monitoring of the fluctuations of CO levels in living cells by the ratiometric fluorescence imaging technique, and we thus anticipate that this probe would be a novel tool for further elucidating the biological functions of CO in living systems.

Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide. For better diagnosis and precise resection of HNSCC, Fluorescent probe has been developed as an ideal tool to visualize tumor sites and to detect biological molecules. However, the targeting strategies of small molecular probes are limited. We designed probe RB-PN (Rhodamine biotin-peroxynitrite) with both sodium-dependent multivitamin transporter (SMVT)-targetable and peroxynitrite (ONOO−)-activatable tumor-targeting strategies. It can detect ONOO− with high specificity and selectivity, and rapid response. Besides, it exhibits prominent imaging abilities with enhanced accumulation by SMVT-transportation. The remarkable sensitivity, selectivity, turn-on signal change and rapid responsive time have been identified. We evidenced the dual-targeting strategy, and applied it in tumor visualization and ONOO− detection both in HNSCC cells and in vivo. We also identified the potential application of it in cytokine therapy using 3D micro-spheroid models. We expect RB-PN with a dual-targeting strategy could be conducive to the diagnosis of tumor pre-operatively or even intra-operatively.

In recent years, more and more chemists and biologists pay attention to the research of fluorescent probes, and great progress has been made in the design and application. In this review, we first discuss the excellent photophysical properties of 4-hydroxy-1,8-naphthalimide (HNI) structure, including excellent photostability, high fluorescence quantum yield, and easy modification of the structure. Then, by discussing the fluorescence behavior of the probe in the corresponding recognition process, the contributions of fluorescent probes built on the platform of HNI in the fields of chemical sensing, biological imaging, pharmaceutical chemistry, environment and food safety in the past ten years are systematically introduced (173 references). At the same time, we hope to develop more powerful fluorescent chemical sensors, which can play a more extensive and exciting role in the future.

Mercury (Hg) is one of the heavy metal pollutants in the environment. Even a very small amount of mercury can cause serious harm to human beings. Herein, we reported a new carbonothioate-based fluorescent probe for the detection of Hg2+ without interference from other metal ions. This probe possessed a very large Stokes shift (192 nm), which could improve the detection sensitivity by minimizing the interferences resulted from self-absorption or auto-fluorescence. With the addition of Hg2+ to the probe solution, considerable fluorescence enhancement was observed. Additionally, the Hg2+ concentration of 0-16 μM and fluorescence intensity showed a good linear relationship (y = 22106× + 53108, R2 = 0.9955). Finally, the proposed probe was used to detect Hg2+ in real water samples, and its result was satisfactory. Therefore, our proposed probe would provide a promising method for the determination of Hg2+ in the environment.

Developing some methods that can simply and effectively detect mercury ions (Hg2+) in the environment and biological systems are very important due to the problems of high toxicity and biological accumulation. Herein, we report a simple rhodol-derived colorimetric and fluorescent probe rhodol-Hg with a recognition receptor of carbonothioate for the specific determination of Hg2+. The color of probe rhodol-Hg solution changed remarkably from colorless to pink in the presence of Hg2+, thus rhodol-Hg could act as a "naked-eye" probe for Hg2+. Additionally, this probe exhibited high selectivity and ultrasensitivity in aqueous solution with the limit of detection (LOD) of 1.4 nM toward Hg2+, and the linear range was 0 - 0.8 μM determined by turn-on fluorescence spectrometry. Importantly, this probe has been successfully used for the detection of Hg2+ in environmental waters and living cells.

The development of techniques for the specific and sensitive detection of HClO is of great importance owing to the diverse functions of HClO in the environment and biological systems. In this paper, based on the intramolecular charge transfer (ICT) mechanism, we have designed and synthesized a simple, ratiometric, colorimetric and fluorescent chemodosimeter 4-(2-(benzo[d]thiazol-2-yl)-2-cyanovinyl)phenylboronic acid (BTCBA) for the specific detection of HClO over other various analytes. ICT-based chemodosimeter BTCBA displayed a large (124 nm) red-shifted ratiometric absorption spectrum and the color changes from colorless to green upon addition of HClO with a fast response time (completed within 1 min). BTCBA could act as a “naked-eye” indicator for HClO, and thus it would provide a convenient method for monitoring HClO in the environment. Additionally, BTCBA could detect HClO quantitatively in the range of 0–14 μM with the detection limit of 9.5 nM (3σ/slope) using the turn-on fluorescence spectrometry method. The ultrasensitive and fast response properties offer the chemodosimeter BTCBA a pleasant opportunity to monitor the fluctuation of exogenous HClO levels in living cells, and we thus anticipate that this chemodosimeter would provide a promising tool for further unraveling the diverse functions of HClO in biological sciences.

The development of techniques for detecting HOCl at the subcellular level is very important to elucidate its cellular functions. Due to its relatively low concentration, it is still a great challenge to specifically track the basal HOCl in normal cells. In this paper, based on the unique chlorination of HOCl by the initiation of chlorinium ions (Cl+) in an acidic medium, we have developed a simple pH-mediated lysosome-targetable fluorescent probe Lyso-HOCl for the specific detection of HOCl over other bioactive molecules at higher concentration (500 μM). Our results show that Lyso-HOCl possesses a detection limit of 8.0 pM, and can quantitatively detect HOCl at the picomolar level. The ultrasensitive and ultrafast response property of probe Lyso-HOCl offers a good opportunity to monitor the basal HOCl and the fluctuation of endogenous HOCl levels in the lysosomes of macrophages (Raw 264.7 cells), and we thus anticipate that this probe would provide a promising tool for further unraveling the biological functions of HOCl in subcellular lysosomes.

A fluorescent probe 1 has been successfully developed to determine human serum albumin (HSA). Probe 1 expresses a dramatic fluorescence enhancement to HSA without interference from other amino acids. Under the optimal conditions, the calibration graphs are linear over the range of 0 - 13.3 μg/mL with the limit of determination of 0.61 μg/mL. Thus, this probe shows high sensitivity and selectivity to HSA.

Recently, growing attention has been paid to the detection of hydrazine (NH2 NH2 ) because of its important roles in industrial chemical and high toxicity to human beings. Herein, we have constructed a new colorimetric and far-red fluorescent probe containing a receptor of 4-bromobutanoate to selectively detect hydrazine. The probe could detect hydrazine quantitatively in the range of 40-500 μM with the detection limit of 2.9 μM. In addition, the probe could monitor hydrazine by the ratiometric method with a large (185 nm) red-shifted absorption spectrum, and the color changes from yellow to blue make it as a 'naked-eye' indicator for hydrazine. Consequently, our proposed probe would be of great benefit for monitoring hydrazine in aqueous solution.

Mercury ions as high toxic pollutants have received wide-spread attention because of their poisonousness, persistence and enrichment. To better understand the distribution of mercury species and supplement more detailed toxicological research, it is necessary to develop some methods for monitoring mercury ions with high sensitivity and selectivity. Therefore, a simple rhodol-based highly selective fluorescent probe, RH-Hg, has been developed for monitoring Hg

Hypochlorous acid (HOCl) has received special attention by virtue of its pivotal antimicrobial nature, and the appropriate amount of HOCl is beneficial to innate immunity of host to cope with microbial invasion. However, the uncontrollable accumulation of HOCl is implicated in many human diseases and even cancers. Thus, to determine its deeper biological functions, it is significantly important to specifically monitor intracellular HOCl in biosystems. Herein, we rationally designed a simple fluorescent probe

Exploring techniques for monitoring the intracellular signaling molecule carbon monoxide (CO) in biosystems is important to help understand its various cellular functions. Therefore, a simple long-wavelength colorimetric fluorescent probe LW-CO was designed for selectively and sensitively detecting intracellular CO in living systems. Probe LW-CO is ultrasensitive and can track CO levels in the range of 0–1 μM, with a detection limit of about 3.2 nM. Additionally, the obvious color changes of probe LW-CO with CO (yellow to pink) provide a convenient way for on-site detection of CO with the naked eye. Probe LW-CO was applied to track the exogenous levels of CO in RAW264.7 cells. Probe LW-CO proved to be an efficient method for investigating various cellular functions of CO.

Biothiols such as cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) are widely found in mammalian cells. They are closely related to the production and metabolic pathways and play very important roles in physiological and pathological activities. Therefore, the quantitative detection of these biothiols is of great significance. Although many fluorescent probes have been successfully used to track biothiols in biological samples, the fluorescence method for simultaneously detecting these biothiols using separated fluorescence emission channels under single wavelength excitation is still immature. In this work, we prepared the conjugate of seminaphthorhodafluor (SNARF) dye and 7-nitro-1,2,3-benzoxadiazole (NBD) using as a simple long-wavelength fluorescent probe SNARF-NBD for specific detection of biothiols. Cys/Hcy and GSH/H2S were identified by two separated fluorescence emission channels under single wavelength excitation, which showed good selectivity and sensitivity. In addition, SNARF-NBD has low cytotoxicity and shows good imaging ability in living cells and zebrafish.

Peroxynitrite (ONOO-) has been proven to participate in various physiological and pathological processes, and may also be a contributing factor in many diseases. In view of this, there is a need to develop detection tools for unambiguously tracking a small amount of endogenous ONOO- to reveal its exact mechanisms. In this paper, a colorimetric and red-emitting fluorescent probe Red-PN, based on a rhodamine-type fluorophore and hydrazide reactive site is described. The probe Red-PN possesses the advantages of rapid response (within 5 s), visual color change (from colorless to pink), preeminent sensitivity (detection limit = 4.3 nM) and selectivity. Because of these outstanding performances, it was possible to accurately detect endogenous ONOO-. It was encouraging that the probe Red-PN could be used effectively for tracking the relatively low levels of endogenous and exogenous ONOO- in living cells and zebrafish. Thus, it is envisioned that the probe Red-PN would have promising prospects in applications for imaging ONOO- in a variety of biological settings.

Liver cancer is a kind of high mortality cancer due to the difficulty of early diagnosis. And according to the reports, the concentration of reactive oxygen species (ROS) was higher in cancer cells than normal cells. Therefore, developing an effective fluorescent probe for hepatoma-selective imaging of hypochlorous acid (HOCl) which is one of the vital ROS is of great importance for understanding the role of HOCl in liver cancer pathogenesis. However, the cell-selective fluorescent probe still remains a difficult task among current reports. Herein, a galactose-appended naphthalimide (Gal-NPA) with p-aminophenylether as a new receptor and galactose moiety as hepatoma targeting unit was synthesized and employed to detect endogenous HOCl in living HepG2 cells. This probe was proved to possess good water solubility and could respond specifically to HOCl. In addition, probe Gal-NPA could completely react to HOCl within 3 s meanwhile accompanied by tremendous fluorescence enhancement. The quantitative linear range between fluorescence intensities and the HOCl concentrations was 0 to 1 μM (detection limit = 0.46 nM). More importantly, fluorescence confocal imaging experiments showed that probe Gal-NPA could discriminate hepatoma cells over other cancer cells and simultaneously trace endogenous HOCl levels in living HepG2 cells. And we thus anticipate that probe Gal-NPA has the potential application for revealing the functions of HOCl in hepatoma cells.

Mercury, as a highly toxic heavy metal, can cause very serious harm to human health and even death in severe cases. Therefore, we synthesized a novel ratiometric fluorescent probe for detecting mercury ions, with mercaptoethanol as the recognition receptor. Probe CMER could determine mercury ions in 0–1.6 μM and the detection limit is 7.6 nM. Moreover, CMER manifested a fast response for Hg2+ (within 5 s) and simultaneously observed that the color changed from light yellow to orange by naked eye. In addition to these preeminent spectral properties, the probe also had satisfactory bioimaging results in RAW 264.7 macrophage cells and zebrafish.

Hypobromous acid is an important reactive oxygen species (ROS), which is involved in operating various cellular functions. However, the abnormal production of HOBr can induce the generation of a variety of diseases. Although fluorescence probes are huge contributor to our understanding of the biological roles of HOBr, relatively few probes have been used to detect HOBr. Hence, we constructed a ratiometric fluorescent probe Ratio-HOBr with high selectivity to sensitively monitor HOBr. Probe Ratio-HOBr exhibited quick response (

The development of probes for selective detection of mercury ions (Hg2+) is an important mission to accomplish because of the toxicity and ubiquity of Hg2+. Herein, we designed and synthesized a novel fluorescent probe O-(N-butyl-1,8-naphthalimide)-4-yl-O-phenyl carbonothioate (CBONT) for selective and sensitive detection of Hg2+ by turn-on fluorescence spectroscopy. Probe CBONT exhibited a fast response for Hg2+ with excellent sensitivity (limit of detection = 1.9 nM, 3σ/slope), and it might be attributed to the adoption of a new recognition receptor of carbonothioate moiety. Additionally, probe CBONT could serve as a “naked-eye” indicator for Hg2+. Finally, probe CBONT could be successfully applied to detect the concentrations of Hg2+ in real water samples. Our proposed recognition receptor would open up new, exciting opportunities for designing highly selective and ultrasensitive fluorescent probes for the determination of Hg2+ in real water samples.

Mercury (Hg) and its derivatives pose a serious threat to the environment and human health. Thus, the development of methods for the selective and sensitive determination of Hg(2+) is very important to understand its distribution, and to implement more detailed toxicological studies. Herein, we developed a new method for the detection of Hg(2+) based on the tricyanoethylene derivative and mercaptoethanol. This method could selectively detect Hg(2+) in a 100% aqueous solution by the naked-eye within the range of 1 - 60 μM. Importantly, this method also could detect Hg(2+) quantitatively by ratiometic absorption spectroscopy in the range of 0.1 - 6 μM with a detection limit of 55 nM. We anticipate that this proposed method will be used widely to monitor Hg(2+) in the environment.

The development of simple techniques for monitoring hypochlorous acid (HOCl) in living cells is urgently needed to disclose the important roles of HOCl in biological systems. Although a number of fluorescent probes have been exploited to detect HOCl, most of them are easily influenced by other competing reactive oxygen species (ROS) and reactive nitrogen species (RNS), and disturbed by many factors including variabilities in excitation, probe distribution and environmental conditions due to the recognition of HOCl based on the fluorescence changes in single wavelength. Herein, in this work, we present a simple fluorescent probe AETU-HOCl containing a new recognition group (2-amino-ethyl)-thiourea (AETU) for the ratiometric detection of HOCl in living cells. Probe AETU-HOCl exhibits outstanding selectivity for HOCl over other ROS/RNS at higher concentrations (0.5 mM, 100 equiv.). More importantly, the rapid response (1 min) and high sensitivity (a detection limit of 3.9 nM) allow it to successfully visualize the intracellular HOCl levels by the ratiometric imaging. The present study would offer a simple, ratiometric, rapid, and ultrasensitive assay for the accurate determination of HOCl in the biological systems.

The development of selective fluorescent probes for rapid and sensitive detection of hypochlorite anion (OCl − ) is of great importance for biomedical researchers to investigate the detailed functions and mechanisms of OCl − in living systems. Herein, based on the internal charge transfer (ICT) mechanism, employing 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) fluorophore, we developed a novel visual and far-red fluorescent dual-channel probe TCF-OCl for the rapid and sensitive detection of OCl − in aqueous solution and living cells. TCF-OCl exhibits high OCl − -selectivity even in the presence of other reactive oxygen species (ROS), which may be ascribed to the excellent reactivity of the arylboronate recognition moiety toward OCl − . ICT-based fluorescent probe TCF-OCl displays a considerable absorption spectrum (at 570 nm) enhancement and the color changes from faint yellow to red upon addition of OCl − . In addition, the results showed that TCF-OCl could quantitatively detect OCl − in the range of 0 to 50 μM with the detection limit of 0.4 μM by visual and fluorescent spectrometry methods. Importantly, TCF-OCl was successfully applied to the fluorescence imaging of OCl − levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of OCl − in living systems.

Nitroxyl (HNO) has attracted increasing attention for its ability to enhance myocardial contractility and vasorelaxation in heart failure. However, studies of the detailed functions and mechanisms of HNO in vivo are hampered by a lack of reliable detection methods. Herein, we report a novel 2-(diphenylphosphino)benzoate-caged 2-(2′-hydroxyphenyl)benzothiazole fluorescent chemodosimter ( HNO-HBT ) for the sensitive and rapid detection of HNO in living cells. HNO-HBT exhibits high HNO-selectivity even in the presence of high concentration of biological reductants including glutathione (GSH), hydrogen sulfide (H 2 S) and ascorbate (AA), which is ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. In addition, the results showed that HNO-HBT could quantitatively detect HNO in the range of 0–40 μM with the detection limit of 50 nM. Importantly, HNO-HBT was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.

Currently, there is a great need to develop methods for the selective detection of fluoride anions (F(-) ) owing to their toxicity in the environment and biological function in living systems. In this study, we developed a new fluorescent probe (probe 1) employing a Si-O bond as a highly selective recognition receptor for detecting F(-) via intramolecular charge transfer. Probe 1 could detect F(-) quantitatively using the turn-on fluorescence spectroscopy method with excellent sensitivity in the range of 4-38 μM and a detection limit of 0.26 μM; the detection time was < 17 min. We anticipate that probe 1 would be used widely to monitor F(-) in the environment. Copyright © 2015 John Wiley & Sons, Ltd.

It is very important to determine mercury owing to its complex biological poisonousness that could cause various physical diseases and even death. In this study, we designed a novel coumarin-based ratiometric fluorescent probe, CR-Hg, with DL-dithiothreitol moiety as the recognition receptor to detect mercury ions (Hg2+). CR-Hg could realize the quantitative detection of Hg2+ between 0 and 1.4 μM with low detection limit (1.6 nM). Furthermore, CR-Hg could react quickly with Hg2+ in a few seconds and accompanied by color changes from pale yellow to orange. In the end, the applications of CR-Hg in the water samples, living cells and zebrafish more deeply indicated that the probe could serve as a novel promising tool for revealing mercury distribution in the environment and organisms.

As one of the reactive oxygen species (ROS), hypochlorous acid (HOCl) plays a key role in the pathogenesis of a range of diseases. The detection of HOCl has been a hot research topic. Herein, this paper proposes a new conjugate of 4-hydroxy-1,8-naphthalimide and p-methylaminophenylether as fluorescent probe HNPE with simple synthesis and excellent performances to detect HOCl. The probe has a good linear relationship with HOCl (0–1 μM), and its detection limit is 6.56 nM. Moreover, this probe has good selectivity, which can distinguish HOCl from other common analytes. Importantly, the probe HNPE has some achievements in HOCl imaging of living cells and zebrafish. Hence, the probe HNPE is competent as a tool to visualize HOCl in biosystems.

In the appropriate Golgi stress response, adaptive repair will occur by changing or triggering the expression of related pathways. Furthermore, it also can inhibit the cytotoxicity of cells in the altered redox homeostasis. Elevated biosynthesis and transport of cysteine (Cys) will be induced to restore the abnormal redox state, and more evidences are needed to confirm this process in the Golgi stress response. Herein, we developed a novel Golgi-targetable Cys-specific fluorescent probe GT-Cys for sensitively detecting Cys generation during the Golgi stress response. In probe GT-Cys, thiobenzoate moiety was chosen as recognition group of Cys, and 4-CF3-7-aminoquinoline dye was selected as fluorophore and Golgi targetable unit. Probe GT-Cys can selectively and sensitively respond to Cys. Additionally, it has good targetable properties, facilitating the study of complicated stress response of Golgi apparatus. Importantly, the applications of probe GT-Cys in biological imaging showed that it is sensitive enough to basal Cys, especially to endogenous Cys during the Golgi stress response.

Iron plays an essential role in the chemical transformation of cells via the transition of multiple oxidation states of iron. Misregulation of iron may lead to the disorder of reactive oxygen species (ROS) catalyzed by iron, which is associated with diverse diseases. Therefore, the monitoring of labile iron in vivo is crucial for revealing its diverse functions in the biosystems. In this work, a novel “off-on” fluorescent probe NT-Fe was designed to detect ferrous ion (Fe2+) in both aqueous solutions and biological systems, based on the reduction of nitroxides to hydroxylamine. Probe NT-Fe manifested highly selective and sensitive detection (DL = 89 nM) of Fe2+. In addition, probe NT-Fe can detect Fe2+ within 50 s, which is conducive to real-time detection of labile iron in the biological system. Moreover, the intracellular Fe2+ can be tracked with probe NT-Fe in living cells effectively. Most of all, as far as we know, probe NT-Fe has been used for the first time to monitor Fe2+ in zebrafish.

CO-releasing molecule-2 (CORM-2), as a safe donor for releasing CO, has been widely adopted to disclose the physiopathological roles of CO and used as therapeutic drug replacing gaseous CO. The accurate determination of CORM-2 levels in biological systems is central for understanding its safe use as therapeutic agent and the cellular functions of CO. In this paper, a novel fluorescent probe CPD-NB was synthesized, which provided a safe and convenient way for detecting CORM-2 without the requirement of Pd2+ as an additional substrate. It featured a robust fluorescence response to CORM-2 with desirable sensitivity (the detection limit was as low as 4 nM), and showed high selectivity toward CORM-2 over other biologically relevant species. Moreover, with the low cytotoxicity of probe CPD-NB, the visualizations of CORM-2 changes in live cells and zebrafish were also achieved. Thus, we expected that probe CPD-NB could be as an ideal platform for safe and powerful imaging of CORM-2 in biological systems, and may thus promote the progress of CO-related research.

Hypobromous acid (HOBr) is profoundly implicated in many physiological and pathological conditions. In vivo, the production of HOBr is a double-edged sword for organisms. Appropriate amount of HOBr have effective antibacterial activity, however, abnormal production of HOBr can easily cause tissue damages. Unfortunately, the detailed cellular functions of HOBr are still unclear, which are mainly because highly specific and sensitive sensing of HOBr in living organism remains to be challenged. Based on that, a new n aphthalimide-derived 1-(2- a mino e thyl) p iperidine-containing highly selective fluorescent probe NAEP-HOBr for bioimaging endogenous HOBr was designed. Probe NAEP-HOBr possesses satisfactory sensitivity reflected in low detection limit (200 nM), pleasurable selectivity over others biological molecules, and rapid response for HOBr (∼1 min). Moreover, probe NAEP-HOBr is competent for tracking endogenous HOBr in living cells and zebrafish, which further provides an effective and powerful tool for tracking the fluctuations of endogenous HOBr in living organisms.

Developing a reliable tool for monitoring peroxynitrite (ONOO−) in the complex organisms is critical to uncover its detailed cellular functions in numerous physiological and pathological processes. Thus, a novel ratiometric fluorescent probe was reasonably designed for ONOO−, in which the rhodol-HBT conjugate dye was chosen as a fluorophore, and hydrazine moiety was adopted as recognition receptor of ONOO−. The probe exhibited outstanding sensitivity, specificity, and a fast response towards ONOO−. More importantly, the probe with a large emission shift (Δλem = 127 nm) has been proven to be capable of tracking ONOO− with high resolution in live cells and zebrafish. This work provides a simple and reliable tool for detecting and imaging ONOO− in the living systems, and thus we anticipate that the designed probe could be used as a powerful imaging tool in unraveling biological functions of ONOO−.

As a reactive nitrogen species (RNS), peroxynitrite (ONOO−) is known for its crucial functions in biological systems. Excessive formation of ONOO− is very closely related to the pathogenesis of a series of diseases, and thus, effective methods are needed for highly sensitive detection of ONOO−. Herein, a simple fluorescent probe RHHP-PN was proposed to detect ONOO−, and manifested obvious color changes from colorless to red in less than 10 s. Besides, it is not only suitable for quantitative detection of ONOO−, but also satisfactory in distinguishing ONOO− from other related species. What is particularly noteworthy is the fluorescence bioimaging for tracing endogenous and exogenous ONOO− in living cells and zebrafish. Therefore, probe RHHP-PN could be used as an imaging tool to visualize intracellular ONOO− in biological systems.