A long-wavelength mitochondria-targeted CO fluorescent probe for living cells and zebrafish imaging

Carbon monoxide (CO) not only causes damage to life and health as an environmental pollutant, but also undertakes many physiological functions in organisms. In particular, developing means that can be used for the determination of CO in organelles will provide insight into the vital role it plays. Studies have shown that mitochondrial respiration is closely related to CO concentrations, so it is critical to develop tools for CO detection in mitochondria. Here, we use a rhodamine derivative that can target mitochondria as fluorophores to construct a mitochondrial-labeled CO fluorescence probe (Rh-CO) with high sensitivity (detection limit: 9.4 nM), excellent water-solubility, and long emission (λem = 630 nm). Prominently, the probe has outstanding mitochondria-targeting capabilities. Moreover, we used transient glucose deprivation (TGD) and heme to stimulate endogenous CO production in living cells and zebrafish, respectively, and the probe exhibited excellent imaging capabilities. All in all, we expect this probe to contribute to a deeper understanding of the role played by CO in mitochondria.

A dual-lock-controlled mitochondria-targeted ratiometric fluorescence probe for simultaneous detection of atherosclerosis-related HClO and viscosity

Precise detection of inflammatory microenvironment-related viscosity and hypochlorous acid (HClO) contributes to illuminating the pathogenesis and further diagnosing of atherosclerosis (AS). Herein, a dual-lock-controlled mitochondria-targeted fluorescence probe (NS) for simultaneous imaging of HClO and viscosity in AS-related foam cells is presented. NS performs linear increase in green-fluorescence along with increased viscosity (excited at 425 nm), permitting "off-on" fluorescence imaging of viscosity. Meanwhile, upon HClO activation, NS exhibits red-shifted and enhanced fluorescence in orange, thus leading to ratiometric fluorescence quantification of HClO (excited at 465 nm). Such dual-lock-controlled effect makes NS realize simultaneous imaging of viscosity and HClO with high sensitivity and selectivity via "off-on" and ratiometric fluorescence readouts, respectively. Besides, endowed with mitochondria-targeting capacity, NS achieves in situ imaging of mitochondria viscosity and HClO in living RAW264.7 cells. Importantly, for the first time, NS realizes simultaneous imaging of mitochondria viscosity and HClO in macrophage-derived foam cells, revealing the close association between HClO level and viscosity change in mitochondria during foaming translation of macrophages in atherogenesis. This work not only provides a novel strategy and tool to image organelle-located viscosity and HClO in living systems, but also holds great potential in early diagnosis of AS.

Recent Development of Lysosome-Targeted Organic Fluorescent Probes for Reactive Oxygen Species

Reactive oxygen species (ROS) are extremely important for various biological functions. Lysosome plays key roles in cellular metabolism and has been known as the stomach of cells. The abnormalities and malfunctioning of lysosomal function are associated with many diseases. Accordingly, the quantitative monitoring and real-time imaging of ROS in lysosomes are of great interest. In recent years, with the advancement of fluorescence imaging, fluorescent ROS probes have received considerable interest in the biomedical field. Thus far, considerable efforts have been undertaken to create synthetic fluorescent probes for sensing ROS in lysosomes; however, specific review articles on this topic are still lacking. This review provides a general introduction to fluorescence imaging technology, the sensing mechanisms of fluorescent probes, lysosomes, and design strategies for lysosome-targetable fluorescent ROS probes. In addition, the latest advancements in organic small-molecule fluorescent probes for ROS detection within lysosomes are discussed. Finally, the main challenges and future perspectives for developing effective lysosome-targetable fluorescent ROS probes for biomedical applications are presented.

Rational Design of a Dual-Channel Fluorescent Probe for the Simultaneous Imaging of Hypochlorous Acid and Peroxynitrite in Living Organisms

Hypochlorous acid (HOCl) and peroxynitrite (ONOO^-) are two important highly reactive oxygen/nitrogen species, which commonly coexist in biosystems and play pivotal roles in many physiological and pathological processes. To investigate their function and correlations, it is urgently needed to construct chemical tools that can track the production of HOCl and ONOO^- in biological systems with distinct fluorescence signals. Here, we found that the coumarin fluorescence of coumarin-benzopyrylium (CB) hydrazides (spirocyclic form) is dim, and their fluorescence properties are controlled by their benzopyran moiety via an intramolecular photo-induced electron transfer (PET) process. Based on this mechanism, we report the development of a fluorescent probe CB2-H for the simultaneous detection of HOCl and ONOO^-. ONOO^- can selectively oxidize the hydrazide group of CB2-H to afford the parent dye CB2 (Abs_max/Em_max = 631/669 nm). In the case of HOCl, it undergoes an electrophilic attack on the benzopyran moiety of CB2-H to give a chlorinated product CB2-H-Cl, which inhibits the PET process within the probe and thus affords a turn-on fluorescence response at the coumarin channel (Abs_max/Em_max = 407/468 nm). Due to the marked differences in absorption/emission wavelengths between the HOCl and ONOO^- products, CB2-H enables the concurrent detection of HOCl and ONOO^- at two independent channels without spectral cross-interference. CB2-H has been applied for dual-channel fluorescence imaging of endogenously produced HOCl and ONOO^- in living cells and zebrafish under different stimulants. The present probe provides a useful tool for further exploring the distribution and correlation of HOCl and ONOO^- in more biosystems.

Fluorescent Probes Design Strategies for Imaging Mitochondria and Lysosomes

Modern cellular biology faces several major obstacles, such as the determination of the concentration of active sites corresponding to chemical substances. In recent years, the popular small-molecule fluorescent probes have completely changed the understanding of cellular biology through their high sensitivity toward specific substances in various organisms. Mitochondria and lysosomes are significant organelles in various organisms, and their interaction is closely related to the development of various diseases. The investigation of their structure and function has gathered tremendous attention from biologists. The advanced nanoscopic technologies have replaced the diffraction-limited conventional imaging techniques and have been developed to explore the unknown aspects of mitochondria and lysosomes with a sub-diffraction resolution. Recent progress in this field has yielded several excellent mitochondria- and lysosome-targeted fluorescent probes, some of which have demonstrated significant biological applications. Herein, we review studies that have been carried out to date and suggest future research directions that will harness the considerable potential of mitochondria- and lysosome-targeted fluorescent probes.

The Development of a 4-aminonaphthalimide-based Highly Selective Fluorescent Probe for Rapid Detection of HOCl

Recently, more and more evidence indicated that intracellular HOCl plays a crucial role in the regulation of inflammation and apoptosis, while excessive HOCl has an impact on human health problems. So, the development of methods for sensitive detection of HOCl is very vital to reveal its various physiological and pathological functions. In this paper, we have described a simple fluorescent probe for selective detection of HOCl, whereas for higher concentrations of other biological important substances, the probe almost does not respond. The experimental results show that the probe can quantitatively determine the range of 0-1 μM HOCl, the detection limit is 0.05 μM. In addition, the probe reacts quickly with HOCl (< 3 s), which is helpful to monitor HOCl in biological system because HOCl is highly reactive and short-lived. The ability of the probe to HOCl enables it to be used to track the HOCl levels in living systems.

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

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

A pyrene-pyridyl nanooligomer as a methoxy-triggered reactive probe for highly specific fluorescence assaying of hypochlorite

A novel pyrene-pyridyl conjugated oligomer (OPP-OMe) was conveniently prepared by one-pot Sonogashira coupling. Intriguingly, it was found that introducing only one methoxy moiety at the 4-pyridyl position can be sufficient for creating an oligomer-based ultrafine reactive fluorescent nanoprobe, i.e., OPP-OMe NPs (ca. 2.5 nm in diameter). Spectral analyses and elucidation of the intermediate structure revealed that the methoxy triggered-oxidation, together with nanoaggregation of OPP-OMe NPs, results in rapid, specific and supersensitive sensing of hypochlorite (LOD, 0.3 nM, S/N = 3).

A deep-red lysosome-targetable fluorescent probe for detection of hypochlorous acid in pure water and its imaging application in living cells and zebrafish

Hypochlorite plays a significant role in physiological processes, particularly regulation of lysosomal functions, and is involved in various diseases. Thus, it is crucial to develop highly sensitive and selective molecule tools to detect HClO in lysosomes. Herein, a novel 2H-benzo[h]chromene-pyridine derivative (1) was synthesized through condensation reaction, which exhibited a notable deep-red emission at 640 nm in pure water. This deep-red emission was specifically quenched by adding ClO^-. The response of probe 1 toward ClO^- was rapid (within 10 s), sensitive (detection limit of 0.012 μM), and effective over a wide range of pH (1.0-12.0). Due to the existence of morpholine as the lysosome-targeting unit, the probe was successfully utilized to monitor lysosomal ClO^-. Moreover, the probe 1 was also applied to detecting ClO^- in zebrafish.

A novel nopinone-based fluorescent probe for colorimetric and ratiometric detection of hypochlorite and its applications in water samples and living cells

A novel fluorescent probe (OFN) based on nopinone for the detection of hypochlorite has been developed. The probe OFN exhibited a colorimetric and ratiometric response to hypochlorite with good selectivity, high sensitivity (the low detection limit is 0.136 μM) and fast response time (30 s). In response to ClO-, an obvious change was observed in both the fluorescence and absorption spectra, followed by the visible color change from colorless to yellow and the fluorescence color change from yellow to green. The sensing mechanism confirmed that the oxime group of OFN was oxidized to the aldehyde group, which was proved by HRMS and 1H NMR. What is more, the probe was used not only to detect the concentration of ClO- in water samples but also for monitoring ClO- in living cells.

A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2 S since 2015

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H₂ S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H₂ S is important to maintain normal physiological functions. Conversely, abnormal levels of H₂ S may contribute to various diseases. Due to the importance of H₂ S in physiology and pathology, research into the effects of H₂ S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applications in vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H₂ S, an 'evil and positive' molecule, is not only toxic, but also produces significant effects; a 'greedy' molecule, is not only a strong nucleophile under physiological conditions, but also undergoes a continuous double nucleophilic reaction. Therefore, in this tutorial review, we will highlight recent advances made since 2015 in the development and application of red/NIR fluorescent probes based on nucleophilic reactions of H₂ S.

A novel highly sensitive fluorescent probe for bioimaging biothiols and its applications in distinguishing cancer cells from normal cells

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.

Rhodol-based fluorescent probes for the detection of fluoride ion and its application in water, tea and live animal imaging

Herein, we presented two novel turn-on colorimetric and fluorescent probes based on a F^- triggered SiO bond cleavage reaction, which displayed several desired properties for the quantitative detection for F^-, such as high specificity, rapid response time (within 3 min) and naked-eye visualization. The fluorescence intensity at 574 nm (absorbance at 544 nm) of the solution was found to increase linearly with the concentration of F^- (0.00-30.0 μM) with the detection limit was estimated to be 0.47 μM/0.48 μM. Based on these excellent optical properties, the probes were employed to monitor F^- in real water samples and tea samples with satisfactory. Furthermore, it was successfully applied for fluorescent imaging of F^- in living nude mice, suggesting that it could be used as a powerful tool to predict and explore the biological functions of F^- in physiological and pathological processes.

A Reaction-Based Fluorescent Probe for Imaging of Native Hypochlorous Acid

Hypochlorous acid (HOCl), one of the reactive oxygen species (ROS), is highly reactive and short-lived. It is a challenge to dynamic monitor HOCl activity in living systems. Hence, we synthesized a new fluoresce nt probe RF1 based on protection of the hydroxyl group by N,N-dimethylthiocarbamate recognition group, which reached a low fluorescence background signal and highly sensitive property. On account of the electrophilic addition of Cl⁺ to the sulfide of thiocarbamate moiety, probe RF1 was converted to resorufin and triggered emitting bright. RF1 showed not only the highly sensitive and selective response to HOCl in vitro, but also can be applied in environmental water samples and detected HOCl by test strips. Besides, the ability of RF1 monitoring HOCl in HeLa cells by exogenous simulation and tracing native HOCl in macrophages cells were also explored.

Imaging of Hypochlorous Acid by Fluorescence and Applications in Biological Systems

In recent decades, HOCl research has attracted a lot of scientists from around the world. This chemical species is well known as an important player in the biological systems of eukaryotic organisms including humans. In the human body, HOCl is produced by the myeloperoxidase enzyme from superoxide in very low concentrations (20 to 400 μm); this species is secreted by neutrophils and monocytes to help fight pathogens. However, in the condition called "oxidative stress", HOCl has the capability to attack many important biomolecules such as amino acids, proteins, nucleotides, nucleic acids, carbohydrates, and lipids; these reactions could ultimately contribute to a number of diseases such as neurodegenerative diseases (AD, PD, and ALS), cardiovascular diseases, and diabetes. In this review, we discuss recent efforts by scientists to synthesize various fluorophores which are attached to receptors to detect HOCl such as: chalcogen-based oxidation, oxidation of 4-methoxyphenol, oxime/imine, lactone ring opening, and hydrazine. These synthetic molecules, involving rational synthetic pathways, allow us to chemoselectively target HOCl and to study the level of HOCl selectivity through emission responses. Virtually all the reports here deal with well-defined and small synthetic molecular systems. A large number of published compounds have been reported over the past years; this growing field has given scientists new insights regarding the design of the chemosensors. Reversibility, for example is considered important from the stand point of chemosensor reuse within the biological system; facile regenerability using secondary analytes to obtain the initial probe is a very promising avenue. Another aspect which is also important is the energy of the emission wavelength of the sensor; near-infrared (NIR) emission is favorable to prevent autofluorescence and harmful irradiation of tissue; thus, extended applicability of such sensors can be made to the mouse model or animal model to help image internal organs. In this review, we describe several well-known types of receptors that are covalently attached to the fluorophore to detect HOCl. We also discuss the common fluorophores which are used by chemist to detect HOCl, Apart from the chemical aspects, we also discuss the capabilities of the compounds to detect HOCl in living cells as measured through confocal imaging. The growing insight from HOCl probing suggests that there is still much room for improvement regarding the available molecular designs, knowledge of interplay between analytes, biological applicability, biological targeting, and chemical switching, which can also serve to further sensor and theurapeutic agent development alike.

A novel highly specific and ultrasensitive fluorescent probe for monitoring hypochlorous acid and its application in live cells

Based on the important role of hypochlorous acid (HOCl) in the immune system and numerous physiological processes, the detection of intracellular basal HOCl is of significant interest. In this work, we present a simple thiocarbamate-protected fluorescein fluorescent probe, TCFL, for imaging basal HOCl in live cells. Surprisingly, probe TCFL could determine HOCl quantitatively in a large concentration range with a detection limit of 0.65 nM. In addition, probe TCFL showed excellent specificity for HOCl in the presence of other higher concentration analytes (1 mM). Moreover, probe TCFL exhibited a rapid response (within 3 s) to HOCl and thus could provide a tool for real-time monitoring of HOCl. Importantly, probe TCFL with outstanding response features could be applied for monitoring basal HOCl in live cells.

A highly specific, ultrasensitive, thiocarbamate-caged fluorescein probe was developed for real-time detection of HOCl in live cells.

A carbonothioate-based far-red fluorescent probe for the specific detection of mercury ions in living cells and zebrafish

A simple far-red fluorescent probe was developed to monitor mercury ions in environmental water samples and in living systems.

A highly specific fluorescent probe for rapid detection of hypochlorous acidin vivoand in water samples

We report the development of a new chromogenic and fluorogenic probe for the detection of HOCl in zebrafish, mice with arthritis and environmental water samples.

Ratiometric fluorescent probes for capturing endogenous hypochlorous acid in the lungs of mice

Hypochlorous acid (HClO) is a promising diagnostic marker for inflammation and relevant diseases. Although many probes were previously developed for HClO imaging, the development of organ targeting probes is still lacking. Herein, we designed and synthesized a series of cyanine derivatives as ratiometric fluorescent probes to detect endogenous HClO in the lungs with inflammation. By installing diverse lipid chains and amino groups on cyanine, we identified that ClO1, with one n-octadecane chain and two 2-[[2-(dimethylamino)ethyl]methylamino]-ethyl groups, is a superior probe to target the lungs over other major organs in mice. ClO1 was able to sense both exogenous and endogenous HClO in A549 (human lung epithelial) cells through fluorescence ratiometric imaging. In a lipopolysaccharide (LPS)-induced lung inflammation mouse model, ClO1 effectively captured endogenous HClO in the lungs after intravenous administration. Overall, these cyanine-derived probes merit further development as organ targeting HClO sensors.

A novel isolongifolanone based fluorescent probe with super selectivity and sensitivity for hypochlorite and its application in bio-imaging

In this study, a novel biocompatible fluorescent probe (DN) capable of detecting ClO^- in physiological medium was rationally designed and synthesized from natural and renewable isolongifolanone. This probe underwent a highly specific and sensitive oxidation reaction with ClO^- and liberated an isolongifolanone derivative (PA) emitting intensive blue fluorescence. In response to ClO^-, the fluorescence emission of DN was obviously enhanced within a short time. The detection limit of DN toward ClO^- was found to be as low as 5.86 × 10^-9 M. IR, MS and DFT calculation were employed to further confirm the sensing mechanism. Moreover, the test strips coated with DN could easily recognize ClO^- from other relevant species through the changes of fluorescence color under 365 nm UV lamp. More importantly, we also successfully demonstrated the potential application of DN for the detection of intracellular hypochloritein living cells.

Red-emitting fluorescent probe for detecting hypochlorite acid in vitro and in vivo

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 (I₄₈₀/I₆₁₂) increasing from 0.28 to 27.46. The emission intensities ratio (I₄₈₀/I₆₁₂) was linearly enhanced (I₄₈₀/I₆₁₂ = 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.

A near-infrared fluorescent probe based on photostable Si-rhodamine for imaging hypochlorous acid during lysosome-involved inflammatory response

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.

Exploration and application of a highly sensitive bis(salamo)-based fluorescent sensor for B4O72- in water-containing systems and living cells

A highly selective fluorescent sensor H4L based on a bis(salamo)-type compound with two N2O2 chelating moieties as ionophore was successfully developed. Sensor H4L was found to have excellent selectivity for B4O72- over many other anions (Br-, CI-, CN-, CO32-, HCO3-, H2PO4-, HSO4-, NO3-, OAc-, S2O3-, SCN-, SO42-, Hcy (homocysteine) and H2O2), and it exhibited an approximately 150-fold enhancement of the fluorescence response to B4O72- in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Significantly, its fluorescence intensity was enhanced in a linear fashion with increasing concentrations of B4O72-. The detection limit of sensor H4L towards B4O72- was 8.61 × 10-7 M. The test strips could conveniently, efficiently and simply detect B4O72- ions in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Furthermore, sensor H4L showed excellent membrane permeability in living cells, and it was successfully used to monitor intracellular B4O72- by confocal luminescence imaging.

Mitochondria and lysosome-targetable fluorescent probes for HOCl: recent advances and perspectives

Hypochlorous acid (HOCl), as one of the reactive oxygen species (ROS), plays an important role in the destruction of pathogens in the immune system. However, abnormal concentration of biogenic HOCl can also damage host tissues, and it has been shown to be associated with many diseases. Accordingly, detection of HOCl at the subcellular level is important for understanding inflammation and cellular apoptosis. Toward this end, in the past few years, a wide variety of fluorescent HOCl probes have been engineered and applied for imaging of HOCl in subcellular organelles. In this review, we highlight the representative cases of the fluorescent HOCl probes with mitochondria and lysosome-targetable ability. The discussion includes their design strategies, sensing mechanisms, and applications in bio-imaging of HOCl in mitochondria and lysosomes.

A highly specific and ultrasensitive near-infrared fluorescent probe for imaging basal hypochlorite in the mitochondria of living cells

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.

A ratiometric hypochlorite sensor guided by PET controlled ESIPT output with real time application in commercial bleach

A ratiometric hypochlorite sensor based on enhancement of radiative ESIPT by switching off non-radiative PET amenable to quality control of commercial bleach.

A Michael addition–cyclization-based switch-on fluorescent chemodosimeter for cysteine and its application in live cell imaging

We designed and synthesized a fast response fluorescent probe, BTAC (benzothiazol-azacoumarin), for detection of cysteine (Cys).

A highly specific and sensitive ratiometric fluorescent probe for carbon monoxide and its bioimaging applications

A simple highly specific and sensitive ratiometric fluorescent probe has been constructed to monitor carbon monoxide levels in living cells.

A sensitive two-photon ratiometric fluorescent probe for γ-glutamyltranspeptidase activity detection and imaging in living cells and cancer tissues

We develop a novel ratiometric two-photon fluorescent probe that allows highly sensitive and selective detection and imaging of γ-glutamyltranspeptidase activities.

A novel near-infrared fluorescent probe for highly selective recognition of hydrogen sulfide and imaging in living cells

A novel near-infrared fluorescent probe (L) based on a 1,4-diethyl-1,2,3,4-tetrahydro-7H-pyrano[2,3-g]quinoxalin-7-one scaffold has been synthesized and characterized. Probe L displays highly selective and sensitive recognition to H₂S over various anions and biological thiols with a large Stokes shift (125 nm) in THF/H₂O (6/4, v/v, Tris–HCl 10 mM, pH = 7.4). This probe exhibits turn-on fluorescence for H₂S through HS⁻ induced thiolysis of dinitrophenyl ether. Confocal laser scanning micrographs of MCF-7 cells incubated with L confirm that L is cell-permeable and can successfully detect H₂S in living cells.

A novel “off–on” fluorescent probe (L) for H₂S detection with NIR emission and imaging H₂S in living cells.

Ratiometric imaging of lysosomal hypochlorous acid enabled by FRET-based polymer dots

FRET-based fluorescent polymer dots (FPD) with good membrane permeability have been developed for ratiometric imaging of lysosomal HClO in living cells.

Selective visualization of endogenous hydrogen sulfide in lysosomes using aggregation induced emission dots

The AIE dots (AIED) with superior sensor properties have been developed for selective imaging of lysosomal H₂S in living cells.

A simple, cyanovinylene-based, ratiometric, colorimetric and fluorescent chemodosimeter for the specific and sensitive detection of HClO in living cells

A simple, cyanovinylene-based, ratiometric, colorimetric and fluorescent chemodosimeter was developed to sensitively and selectively monitor HClO in living cells.