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Ammonia is a common toxic gas in industrial and agricultural production, which will cause harm to the environment and human health in certain extent. Here, a novel fluorescent probe (R)- 1 based on 1,1′-binaphthol (BINOL) was synthesized for real-time, on-site and quantitative detection of ammonia. The mechanism study shows that the functional groups of –CHO and –OH on (R)- 1 interact with ammonia, which changes the electronic state of the probe molecule and excites strong fluorescence. A test strip for rapid detection of ammonia was developed, which changed from light yellow to reddish brown under natural light after interacting with ammonia, thus realizing the rapid detection and easy visualization of ammonia. Meanwhile, bioimaging experiments shows that probe (R)- 1 can detect exogenous ammonia in cells. [Display omitted] • Specific selective fluorescence recognition of ammonia. • Fast response time (300 s) and high sensitivity (0.96 ppm). • A test strip for real-time and visual detection of ammonia. • Exogenous ammonia fluorescence imaging of cells. [ABSTRACT FROM AUTHOR]

According to DFT calculations, the coordination ratio (1:1) and mechanism of action (PET) of NRh6G-FA with Cu2+ were further investigated and elucidated. NRh6G-FA has been successfully applied to the detection of Cu2+ in CHM samples, "naked eye" identification and bioimaging of Cu2+ in living MCF-7 cells. [Display omitted] • A near-infrared rhodamine-like probe NRh6G-FA responsive to Copper (II) ions was designed and synthesized. • The responses of NRh6G-FA to Cu2+ were thoroughly confirmed by Job's plot, ESI-HRMS and DFT calculations. • NRh6G-FA can be successfully applied to recovery experiments and "naked eye" detection of Cu2+ in Chinese herbal medicine. • NRh6G-FA has low cytotoxicity and can be used for the detection of Cu2+ in living cells. Copper is one of the common among the heavy metal pollution in Chinese herbal medicine (CHM). So, it is essential to develop rapid and accurate testing method to quantify the Cu2+ content in CHM. Herein, we prepared a coordination-based near-infrared fluorescent probe (NRh6G-FA) by introducing a hemicyanine dye in rhodamine 6G scaffold. NRh6G-FA had a high sensitivity, anti-interference performance, fast response (within 60 s), visualization (from light yellow to green) for Cu2+ and excellent sensing performance for the detection of Cu2+ at low concentrations (LOD = 0.225 μM). The most likely mechanism was verified on the basis of Job's plot, ESI-HRMS and DFT calculations. NRh6G-FA could be successfully applied for the detection and "naked eye" recognition of Cu2+ in CHM samples. Moreover, NRh6G-FA was used to visualize Cu2+ in living MCF-7 cells by confocal fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe 3-STF is first designed based on 3-thiolflavone. • The probe 3-STF exhibited a specific "turn-on" fluorescence response towards biothiols (Cys, Hcy, and GSH) with a large stokes shift of 140.6 nm. • The detection of biothiols did not suffer from the interference of other amino acids. • The detection mechanism was discussed in detail. • The probe 3-STF can be successfully applied to monitor endogenous and exogenous biothiols in HepG-2 cells. Abnormal levels of intracellular biothiol species, including glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), are closely relevant to a variety of diseases. In this study, we first report the design and synthesis of a 3-thiolflavone-based probe 3-STF with an S–S linkage both as the fluorescence quenching agent and the recognition site. Upon treatment with biothiols, the S–S linkage was cleaved by nucleophilic attack of RS-, and 3 -STF exhibited a specific "turn-on" fluorescence response at 543.8 nm upon 390 nm excitation. Meanwhile, 3 -STF was proved to be highly sensitive and selective for the detection of biothiols over other nucleophiles such as amino acids and H 2 S. The sensing mechanism was further verified by 1H NMR and ESI-MS analysis. In addition, 3-STF with low cytotoxicity can be successfully applied to detect endogenous and exogenous biothiols in HepG-2 cells. [ABSTRACT FROM AUTHOR]

A new hemicyanine-based near-infrared "off-on" recognition Cu2+ fluorescent probe NRh-NP was designed and successfully synthesized. The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. NRh-NP has high sensitivity, selectivity and a low limit of detection (33 nM as fluorescence sensor and 35 nM as UV sensor) to Cu2+. According to Job's plot and ESI-HRMS, the coordination ratio of NRh-NP to Cu2+ was 1:1. DFT theoretical calculations proved that the sensor mechanism was photo-induced electron transfer (PET). More importantly, NRh-NP has excellent membrane permeability and low cytotoxicity, which could be used not only for the detection of Cu2+ in human breast cancer cells (MCF-7), but also for imaging Cu2+ in living mice. [Display omitted] • The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. • The responses of NRh-NP toward Cu2+ were fully proved by Job's plot, ESI-HRMS and DFT theoretical calculations. • NRh-NP has high sensitivity and selectivity with detection limit as low as 33 nM. • NRh-NP can be used for Cu2+ imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

A novel imidazo[1,2-a]pyridine-rhodamine ratiometric fluorescent probe IP-Hg for Hg2+ based on a fluorescence resonance energy transfer mechanism has been developed. The probe has been proved to show high sensitivity and high selectivity toward Hg2+. Furthermore, it could be used for imaging Hg2+ in cells and in polluted water. Image 1 • A ratiometric fluorescent probe for sensing Hg2+ based on new imidazo[1,2-a]pyridine fluorophore has been synthesized. • The probe exhibits highly sensitivity and selectivity toward Hg2+ (LOD: 9.1 nM). • The ratiometric fluorescent probe displays a remarkable emission shift (220 nm). • The probe show low cytotoxicity and can image in cells. [ABSTRACT FROM AUTHOR]

Hypochloric acid (HOCl) plays vital roles in cell signaling and homeostasis which involved in many related diseases. Therefore, the accurate detected level of OCl− for discussing the complex contributions of OCl− to human health is of great significance. In this study, a novel mitochondrion-targeting fluorescent probe DMI bearing a carbon-carbon double bond as an OCl−-responsive site has been developed. Probe DMI exhibited specific fluorescence response toward OCl− with fast response (within 4 s) and high sensitivity (detection limit is 0.05 μM), where the obvious color changes could be observed by the naked eye. More importantly, DMI could be applied in the bioimaging of OCl− in living A549 cells successfully benefited from its good sensing properties and low toxicity. Fluorescence co-localization test was further carried out and confirmed mitochondria-targetable ability of DMI which can be used for investigating physiological function of HOCl at organelle levels. Image 1 • Probe DMI is a mitochondria-targeting visual fluorescence probe. • DMI could highly sensitive and selective detected of hypochlorite. • The mechanism of DMI has been proved to be via oxidation fracture of C C. • DMI can be used to imaging of OCl− in living A549 cells. [ABSTRACT FROM AUTHOR]

When diabetes is diagnosed, the majority of insulin-secreting pancreatic β cells are already dysfunctional or destroyed. This β cell dysfunction/destruction usually takes place over many years, making timely detection and clinical intervention difficult. For this reason, there is immense interest in developing tools to bioimage β cell mass and/or function noninvasively to facilitate early diagnosis of diabetes as well as to assist the development of novel antidiabetic therapies. Recent years have brought significant progress in β cell imaging that is now inching towards clinical applicability. We explore here the need to bioimage human β cells noninvasively in various types of diabetes, and we discuss current and emerging tools for bioimaging β cells. Further developments in this field are expected to facilitate β cell imaging in diabetes. Diabetic patients suffer from β cell failures that manifest in the loss of β cell mass and/or function. Presently, there is no clinically validated bioimaging probe for the measurement of human pancreatic β cells, which makes early detection of diabetes difficult. Multiple proposed β cell-specific markers have been targeted using radioactively labeled tracers or contrast agents detectable by MRI, PET, or SPECT. Emerging technologies also explore fluorescent low molecular weight probes to target β cells. Currently, many β cell bioimaging tools are studied in a preclinical setting in rodent models and provide valuable proof-of-concept to be further matured. A small number of potential β cell-specific probes have now reached clinical studies. Successful clinical translation could revolutionize the early diagnosis and treatment of diabetes. [ABSTRACT FROM AUTHOR]

A new fluorescent probe ( ABPA ) based on 1,8-naphthalimide, which designed on the “ receptor 1 -fluorophore-spacer-receptor 2 ” model and employed conjugated addition/cyclization sequence mechanism for Cys detection was reported. The probe shows high selectivity and sensitivity for cysteine (Cys) over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). It displays a highly sensitive fluorescence emission to Cys with a detection limit of 0.12 μM (S/N = 3), which is far below the normal level of Cys (30–200 μM) in living cells. Furthermore, ABPA was successfully applied to bioimage intracellular Cys in living cells with low cytotoxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized a fluorescent probe based on the structure of GFP for detection of cysteine in vitro. • The probe is characterized by outstanding sensitivity, selectivity and anti-interference. • Probe successfully used for imaging in MCF-7 cells and applied to cysteine detection in mouse serum with high accuracy. Cysteine (Cys) is a vital amino acid in the body, and its abnormal expression level is associated with many diseases. In this study, a novel fluorescent probe ACHB was synthesized, showing high selectivity, anti-interference ability and achieving accurate detection of cysteine. Different from most previous off–on probes, ACHB showed an on–off fluorescence response to Cys. Acrylic ester was used as a recognizer while green fluorescence protein (GFP) chromophore derivative 4-hydroxybenzylidene-imidazolinone (HBI) was used as the fluorophore. The addition of Cys leads to the hydrolysis of the red-emitting probe (613 nm), releasing a precursor with a lower fluorescent signal and showing an on–off spectral signal, which was ideal for obtaining sensitive detection with high specificity. Furthermore, the probe was successfully applied for simultaneous determination of cysteine (Cys) in living cells and biological sample (mouse serum). In conclusion, probe ACHB is a promising tool to display the intracellular cysteine concentration level, providing a good visualization method for clinical diagnosis and scientific basic research. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe ( NR ) for HOCl based on a new naphthalimide-rhodamine platform involving through-bond energy transfer (TBET) process is presented. Rhodamine B thiohydrazide and naphthalimide derivative were linked to form a structure of monothio-bishydrazide. Free NR only emitted the fluorescence of naphthalimide. The treatment of NR with HOCl converted the monothio-bishydrazide into 1,2,4-oxadiazole. As a result, naphthalimide donor and rhodamine acceptor were connected with electronically conjugated bonds, and the spiro ring of rhodamine was opened. Hence, a typical TBET process took place, resulting in the increase of rhodamine emission at 582 nm as well as the decrease of naphthalimide emission at 532 nm. I 582 /I 532 ratios showed desirable HOCl-dependent performance and responded linearly to minor changes of HOCl concentration (0–5 μM). The detection limit was determined to be 14.5 nM. NR exhibited high selectivity, rapid response and low cytotoxicity. Moreover, NR has been employed for the imaging of artificially loaded HOCl and endogenously produced HOCl with satisfying results. Therefore, NR may act as a practical molecular tool for monitoring HOCl fluctuations in biological systems. [ABSTRACT FROM AUTHOR]

We report a room-temperature strategy for the synthesis of single-crystalline fluorescent graphene quantum dots (GQDs) via electron-beam irradiation. The precursor contained high-activity nitro groups is easy to fusion GQDs with the method. Under optimized conditions (0.02 g 1,3,6-trinitropyrene, radiation dose of 400 kGy and 10 ml 0.5 mol/L hydrazine hydrate), the GQDs exhibit highly efficient fluorescence at 475 nm with a quantum yield of 32%. The PL maximum is well corresponded with the excitation wavelength. Moreover, the single-exponential fluorescence lifetime (4.86 ns) exhibited the intrinsic PL characteristic. The pH stability in neutral and alkaline solution, solid solubility and storage time stability of GQDs are satisfactory. Their application as a safety fluorescent probe for cell imaging is demonstrated. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe (Naphsulf-O) for hydrazine was developed by protecting the hydroxy group of the fluorophore 6-acetyl-2-hydroxynaphthalene via O-4-nitrobenzenesulfonylation, where 4-nitrobenzene was used as a fluorescence quenching moiety as well as an electrophile. Upon nucleophilic aromatic substitution (NAS) reaction of hydrazine toward the probe, the protecting group was removed and fluorophore was released. The probe exhibits a large Stokes shift, excellent selectivity and high sensitivity for hydrazine detection in aqueous solution with a detection limit of 0.716 ppb (22 nM), which is of great importance in both environmental and biological system. Furthermore, it was successfully applied to imaging of hydrazine in living cells. [ABSTRACT FROM AUTHOR]

Thiophenols, a class of toxic and polluting compounds, are widely used in industrial production. Meanwhile, some aliphatic thiols play important roles in living organisms. Therefore, the development of probes for specific thiophenol detection is of great importance. Herein, a novel highly sensitive and selective ‘off-on’ fluorescent probe for detecting thiophenols has been developed by an ICT mechanism through a rational design. The probe displays a large Stokes shift (140 nm) and 60-fold fluorescence intensity enhancement. More importantly, the probe features a rapid signal response time (within 100 s), a good linearity range and the detection limit is as low as 13 nM. In addition, the ability of the probe to detect thiophenols in living cells (HepG2 cells) via an enhancement of the fluorescence has also been demonstrated. [ABSTRACT FROM AUTHOR]

A new coumarin-based fluorescent probe CAA containing an acrylamide group has been designed and synthesized for the detection of biothiols. The probe CAA shows high selectivity and sensitivity for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) over other amino acids. A fluorescence turn-on response is induced by a Michael-type reaction. It shows a highly sensitive fluorescence emission to Cys, Hcy, and GSH, with detection limits of 192 nM for Cys, 158 nM for Hcy, and 155 nM for GSH (S/N = 3). Furthermore, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that CAA can be an effective fluorescent probe for thiols in living cells. [ABSTRACT FROM AUTHOR]

Nitroxyl is reported to be associated with particular physiological or pathological states. Although some fluorescent probes for nitroxyl have been reported, none of them can be used for monitoring mitochondrial nitroxyl in living cells with spatial specificity. Herein, for the first time, we develop a mitochondria-targetable NIR fluorescent probe based on a merocyanine skeleton. The proposed probe is constructed by using 2-(diphenylphosphino)benzoyl group as the nitroxyl recognition moiety and the lipophilic indolium cation as the mitochondria-targeted site. The probe displays an intense fluorescence turn-on response to nitroxyl via the aza-ylide formation and its subsequent Staudinger ligation to release the NIR fluorophore. The probe is highly sensitive and selective towards nitroxyl over other biologically relevant reactive oxygen and nitrogen species. Cell imaging and colocalization experiments prove that the probe is suitable for visualizing nitroxyl in the mitochondria of living cells. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), as one of the important reactive oxygen/nitrogen species, is associated with many physiological and pathological activities. Therefore, effective detection methods with high sensitivity and rapid response time are essential to reveal its functions. A novel Rhodol-based fluorescent probe RN is constructed and synthesized by introducing of 1,1-dimethylhydrazone as a recognition group. Due to the oxidative breakage of the C N bond by ONOO−, the probe has significant fluorescence enhancement change with excellent detection properties such as rapid response time, high sensitivity and selectivity. Moreover, probe RN show low cytotoxicity and is successfully capable of imaging endogenous and endogenous ONOO− in living cells. These properties indicate that RN has great application potential for imaging of ONOO− in biological systems. [Display omitted] • New Rhodol derivative is designed as fluorescent probe (RN) for monitoring of ONOO−. • Probe RN exhibits turn-on fluorescent change toward ONOO− with high sensitivity and rapid response time (<60s). • Probe RN can be used for monitoring endogenous ONOO− changes in cells. [ABSTRACT FROM AUTHOR]

Biological thiols are crucial in biological processes. Therefore, a probe capable of targeting and imaging biothiols in living cells, as well as rapidly labelling the thiols in proteins, is desirable and imperative. Herein, we designed and synthesized FRB-T containing α , β -unsaturated ketones to recognize thiols for detecting biothiols and selectively labelling the sulfhydryl-containing proteins. The probe initially exhibited weak fluorescence and then performed 1, 4-Michael addition reaction between its α , β -unsaturated ketone and thiols, along with the spiro ring-opening, leading to remarkable fluorescence enhancement and colour changes. The specificity of FRB-T towards thiols was high, and its detection limits were 70 nM for cysteine (Cys) and 1.51 μg/mL for ovalbumin (OVA). Furthermore, FRB-T has also been successfully applied to biothiols imaging in Hela cells, and rapid labelling of the sulfhydryl-containing proteins without washing step. [Display omitted] • A biothiol-specific probe with strong fluorescence enhancement and colorimetric response. • The probe owns low LOD of 70 nM and 1.51 μg/mL for Cys and OVA respectively. • A new type of reagent for labelling sulfhydryl-containing proteins without washing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A julolidine-chalcone derivative as Al3+ fluorescent probe was developed. • The probe can detect Al3+ with high selectivity and anti-interference. • Hydroxyl oxygen and carbonyl oxygen on the probe will coordinate with Al3+. • The probe can monitor Al3+ in actual water and biological system. A fluorescent probe 1 based on julolidine-chalcone derivative, which can specifically recognize aluminum ion with high selectivity and anti-interference, was developed. Probe 1 has good fluorescence stability and can detect Al3+ with turn-on fluorescence in a wide pH range of 4.0–9.0. The probe has good repeatability for the detection of Al3+ and fluorescence turn-on and off can be repeated with the alternate Al3+ and EDTA. The sensing mechanism is speculated that Al3+ will coordinate with hydroxyl oxygen and carbonyl oxygen on the probe through in situ 1H NMR and HRMS combing with Job's plot. The probe can also detect Al3+ in actual water samples and applied to monitor Al3+ in biological system. [ABSTRACT FROM AUTHOR]

Herein, a simple and green method was developed for the construction of water soluble fluorescent gold nanoclusters (Au NCs) with the assistance of l -carnosine as both a protecting ligand and a weak reducing agent. The as-prepared Au NCs, with the smaller size (2.31 nm) and longer fluorescence lifetime (7.48 ns), exhibited bright blue photoluminescence under UV light (365 nm) with a quantum yield of 3.4%, excellent stability, and low toxicity for cancer HeLa cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescent NTR probe NFP-NTR based on the benzo[ cd ]indol fluorophore was designed for nitroreductase imaging in living cells under hypoxia conditions. • The probe NFP-NTR showed excellent sensitive capability with calculated limit detection of 17 ng/mL. • The probe NFP-NTR displayed high selectivity towards NTR over other analytes. • The probe NFP-NTR was successfully employed as a desirable tool for cellular imaging of endogenous NTR in Hela cells at the condition of hypoxia. Nitroreductase (NTR) plays a vital part in the activation of drugs and the biodegradation of nitroaromatic compounds. With the enhanced expression level of NTR in hypoxic solid tumors, it has been widely used as one of the biomarkers to evaluate the degree of tumor hypoxia. In this work, we reported a benzoindole-based fluorescent probe NFP-NTR for nitroreductase detection. NFP-NTR can react with NTR specifically to cleave the p-nitrobenzyl ether bond when nicotinamide adenine dinucleotide (NADH) is present, showing significant fluorescence augment characteristics. Encouragingly, NFP-NTR exhibited excellent selectivity and satisfactory sensitivity, with a detection limit of 17 ng/mL. In addition, this probe has been successfully used to image live Hela cells under hypoxic conditions with low cytotoxicity, indicating that probe NFP-NTR has great potential to further elucidate more biological applications of NTR. [ABSTRACT FROM AUTHOR]

A new fluorescein-based fluorescent probe for the detection of Au 3+ has been developed. This probe was derived from 4′,5′-fluoresceindicarboxaldehyde and exhibited highly selective and sensitive response toward gold(III) ions in aqueous solution. There is a good linear relationship between the fluorescence intensity at 523 nm and the concentrations of Au 3+ ranging from 0 μM to 60 μM, which makes it effective for the detection of Au 3+ . The limit of detection (LOD) was evaluated to be 0.07 μM based on S/N = 3. The fluorescence enhancement was attributed to the irreversible C N bond hydrolysis that occurred to this probe in the presence of Au 3+ , generating the fluorescent 4′,5′-fluoresceindicarboxaldehyde. Furthermore, the imaging experiments indicated that this probe is cell-permeable and can be used to detect Au 3+ within living cell. [ABSTRACT FROM AUTHOR]

Drug-induced liver injury (DILI) as an acute liver disease has caused serious concern in public health problems. As a kind of reactive oxygen species, HClO has come into scientists' vision as a marker of DILI. Herein, we construct a BODIPY-based near-infrared (NIR) fluorescent probe (BDP-R-ClO) for the selective and sensitive response of hypochlorous acid. The probe could realize the rapid detection of HClO, with a 20-fold fluorescence enhancement at 661 nm and the detection value of which was only 1.8 nM. Moreover, BDP-R-ClO could diagnose and visualize DILI by monitoring the fluctuation of HClO concentration in vitro and in vivo , and evaluate the detoxification of hepatoprotective drugs. Through the visualization of HClO in the mice liver injury models, BDP-R-ClO not only proved its applicability but also indicated that it had great potential in the diagnosis and monitoring of HClO-related diseases. [Display omitted] ● A novel BODIPY-based NIR fluorescent probe for detection of HClO was developed. ● Probe exhibited favorable selectivity and sensibility towards HClO. ● Probe could be utilized to visualize HClO via fluorescence imaging in live cells and in vivo. ● Probe realized the diagnosis of APAP-induced hepatotoxicity, and evaluated the detoxification of hepatoprotective drugs. [ABSTRACT FROM AUTHOR]

Abstract: A coumarin-based fluorometric probe, HS1, has been successfully developed for highly sensitive and selective detection of hypochlorous acid (HOCl). The probe is based on the specific HOCl-promoted oxidation of oxime. The reaction is accompanied by a 7-fold increase in the fluorescent quantum yield (from 0.03 to 0.21). The fluorescence intensity of the reaction between HOCl and HS1 shows a good linearity in the HOCl concentration range of 1–20μM and a low detection limit of 25nM (S/N=3). In addition, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that the HS1 probe could be an efficient fluorescent probe for HOCl in living cells. [Copyright &y& Elsevier]

Highlights: [•] A novel thiol-reactive fluorescence probe based on the 1,8-naphthalic anhydride fluorophore. [•] The probe can selectively detect thiols by the turning on of its fluorescence. [•] Cell permeability and live cell imaging of thiols are also demonstrated. [Copyright &y& Elsevier]

In situ imaging of nitric oxide (NO) is of great importance to study the critical roles of NO in various physiological and pathological processes. In most currently available fluorescent probes for NO, the o-phenylenediamine (OPD) based derivatives are the most greeted and studied, in which the OPD serves as the reactive site and fluorescence quencher to modulate a turn-on process via photoinduced electron transfer (PET). In this work, a unique turn-off probe containing OPD moiety, N-1 , was designed and synthesized, which was radically different from the typical PET-based turn-on fluorescent probes. By theoretical calculation of molecular orbital, it was verified that not the widely used PET mechanism, but the intramolecular charge transfer (ICT) mechanism should be responsible for the turn-off process. Probe N-1 exhibited a remarkable performance with 7-folds fluorescence intensity decrease (at 490 nm), a low detection limit (20 nM), a fast response to NO within 12 min and a high selectivity for NO over other relevant analytes. Furthermore, probe N-1 was also applied to imaging NO in living cells. All results demonstrated that the new probe N-1 could be a practical and ideal NO indicator with good biological significance. [Display omitted] • O-phenylenediamine-hemicyanine-based probe for NO with a unique turn-off property. • Theoretical calculation verified ICT rather than PET induced the turn-off process. • High selectivity towards NO with low detection limit and short response time. • N-1 was of low toxicity and successfully applied in cell imaging for NO detection. [ABSTRACT FROM AUTHOR]

A novel single-component fluorescent probe using N -acetylgalactosamine as the hepatocyte-specific moiety and 3-nitrophthalimide as the fluorescent reactive unit was designed and synthesized for specifically detecting hepatocellular carbon monoxide in the liver of zebrafish in situ during acute liver injury. [Display omitted] • A novel one-component hepatocyte-specific fluorescent probe (HCP) was designed and successfully synthesized. • HCP exhibited a fast and high degree of fluorescence response to trace CO in solutions. • HCP could selectively visualize the endogenous CO in HepG2 cells over other cells. • HCP could be used to image hepatocellular endogenous CO release in the liver of zebrafish in situ during acute liver injury. A novel single-component fluorescent probe HCP using N -acetylgalactosamine (GalNAc) as the hepatocyte-specific moiety and 3-nitrophthalimide as the fluorescent reactive unit was designed and synthesized to specifically detect hepatocellular carbon monoxide (CO) in vitro and in vivo. The spectral experimental results indicate that HCP displayed high selectivity to CO and could be used to detect trace CO in an aqueous solution with a prominent fluorescent response (more than 80 times). Bioimaging results show that HCP could specifically transport to asialoglycoprotein receptor overexpressed HepG2 cells and could image endogenous CO release in HepG2 cells and the liver of zebrafish in situ during acute liver injury. [ABSTRACT FROM AUTHOR]

This study reports the generation of curauá-derived carbon dots (C-dots) and their suitability for Fe(III) detection, bioimaging and FACS analysis. C-dots were generated from curauá (Ananas erectifolius) fibers by a facile one-step hydrothermal approach. They exhibited graphite-like structure with a mean diameter of 2.4 nm, high water solubility, high levels of carboxyl and hydroxyl functional groups, excitation-dependent multicolor fluorescence emission (in the range 450 nm - 560 nm) and superior photostability. C-dots were highly selective and effective for the detection of ferric Fe(III) ion in an aqueous medium with a detection limit of 0.77 μM in the linear range of 0–30 μM, a value much lower than the guideline limits proposed by the World Health Organization (WHO). In biological cell systems, C-dots were very well tolerated by B16F1 mouse melanoma and J774.A1 mouse macrophages cell lines, both of which effectively internalized C-dots in their cytoplasmic compartment. Finally, C-dots were effective probes for long-term live cell imaging experiments and multi-channel flow cytometry analysis. Collectively, our findings demonstrate that curauá-derived C-dots serve as versatile and effective natural products for Fe(III) ion sensing, labeling and bioimaging of various cell types. This study adds novel C-dots to the library of carbon-based probes and paves the way towards a sustainable conversion of a most abundant biomass waste into value-added products. [Display omitted] • Fluorescent C-dots was successfully prepared using Ananas erectifolius (curauá) by hydrothermal approach. • C-dots show an excitation -dependent emissive property and strong photostability. • C-dots were used as a fluorescent probe for a label-free selective detection of Fe(III) ions in aqueous medium. • C-dots could be used as a low-cost fluorescent probe for labeling and bioimaging of B16F1 and J774.A1 cell lines. [ABSTRACT FROM AUTHOR]

• Dehydroabietate-based fluorescent probe for Hg2+ and Fe3+ was synthesized and characterized. • Detection limits of the sensor were 31.0 nM and 31.2 nM for Hg2+ and Fe3+ ions, respectively. • The sensor have a wide pH range for ion detection (5 ~ 12), and a short response time (10 s). • Fluorescent imaging experiments using MCF-7 and SMCC-7721 cell were carried out successfully. A novel dehydroabietic acid-based fluorescent probe (DBH) containing 2,4-diarylbenzimidazole moiety was designed and synthesized, and the compound was characterized by its UV–Vis, FT-IR, 1H NMR, 13C NMR and ESI-MS spectra. DBH could be used for the detection of Fe3+ and Hg2+ through the selective fluorescence quenching in EtOH/H 2 O solution. The probe DBH showed excellent selectivity and sensitivity towards Fe3+ and Hg2+ over other metal ions. The limits of detection were calculated as 3.12 × 10−8 M and 3.10 × 10−8 M, respectively. Especially, DBH have a wide pH range for ion detection (5 ~ 12), and a short response time (10 s). Job's plot method in combination with ESI-MS and FT-IR spectra was used to determine the stoichiometry of DBH -Fe3+/Hg2+ complexes as both 2:1. Moreover, DBH exhibited low cytotoxicity to MCF-7 and SMCC-7721 cells (IC 50 > 100 μM). In the fluorescent cell imaging experiments, DBH could be used as a prominent intracellular probe for the detection of Fe3+ and Hg2+ in living cells. [ABSTRACT FROM AUTHOR]

• A novel turn-on probe (ABTT-MA) based on "AIE + ESIPT" effect was developed. • The maleimide-appended probe presents high selectivity to Cys over structure-like Hcy and GSH. • New insight into the high selectivity of maleimide-appended probe: Michael addition/S,N-intramolecular rearrangement cascade reaction. • ABTT-MA was allowed in aqueous media with the lowest detection limit (9.4 nM). • ABTT-MA was successfully applied to imaging exogenous and endogenous Cys in living cells. Biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play pivotal roles in numerous physiological events, however, due to the similar structures and reactivities, differentiation of these biothiols remains a challenging task. Herein, we reported a maleimide-appended fluorescent probe ABTT-MA capable of specific sensing of Cys over other structure-alike biothiols with an ultralow detection limit (9.4 nM). Via a series of investigations into the mechanism, the high selectivity toward Cys is ascribed to a Michael addition/S,N-intramolecular rearrangement cascade reaction, in which the involvement of the mercapto and the adjacent amino groups is necessary to proceed the sensing process. Given this presupposition, Cys could be kinetically discriminated from Hcy and GSH. Upon the addition of Cys, a strong fluorescence appeared and the intensity at 503 nm was correlated with Cys concentration linearly over a wide range (0–10 μM). Thanks to the aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) activity, the selective detection of Cys was realized not only in aqueous media but in the paper-based point-of-care test (POCT). Significantly, the practicability of ABTT-MA in exogenous and endogenous Cys imaging in living cells was elucidated as well. [ABSTRACT FROM AUTHOR]

A 2,7-naphthyridine derivative (AND-OH) was used as a fluorophore in the development of a novel fluorescent turn-on probe (AND-DNBS) by introducing a 2,4-dinitrobenzenesulfonate functionality. This fluorescent probe was successfully used for sensing glutathione (GSH) in aqueous media and showed favorable properties such as a rapid response time (45 s) and a significant Stokes shift (227 nm). The characteristics of the developed probe are better than those of another probe, namely ND-DNBS , which was also synthesized by our group and most other previously reported fluorescent probes for GSH. The AND-DNBS probe was able to detect GSH via a red emission in living A549 cells and zebrafishes. These results show that AND-DNBS has potential applications as an excellent probe for detecting GSH in various environments. Image 1 • 2,7-Naphthyridine derivative was applied as a fluorophore to construct a new fluorescent probe AND-DNBS for sensing of GSH. • AND-DNBS displayed a remarkable Stokes shift, rapid response time and high fluorescence enhancement when detecting GSH. • AND-DNBS was successfully applied for detecting GSH imaging in living cells and zebrafish models. [ABSTRACT FROM AUTHOR]

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. Image 1 • Probe HNPE with the p -alkylaminophenylether moiety showed high sensitivity to HOCl (DL = 6.56 nM). • Probe HNPE exhibited preeminent selectivity towards HOCl over other reactive oxygen species. • Probe HNPE was applied to the visualization of native HOCl in living cells and zebrafish. • The concise p -alkylaminophenylether moiety could be used to construct different types of HOCl fluorescent probes. [ABSTRACT FROM AUTHOR]

Overexpression of tumor biomarker glutathione (GSH) has been documented in numerous types of cancers, therefor GSH-activated light-up chemosensors for tumor identification require great attention. A new colorimetric/fluorescent probe (7-(diethylamino)-2-oxo-2H-chromen-3-yl)methylene)-4-(dimethylamino) benzohydrazide (HL) was prepared, which could be applied in discriminating Cu2+ and further recognizing GSH based on its Cu complex. Firstly, the probe HL toward Cu2+ exhibited selective fluorescence quenching and obvious color change from yellow to orange-red under visible light. Further, when GSH was introduced to the Cu2+-2HL system, the fluorescence recovered rapidly due to the high affinity of GSH to Cu2+, meanwhile the color reverted back to former yellow. Based on fluorescence titration, the detection limits were calculated as 2.40 × 10−8 M and 1.29 × 10−7 M for Cu2+ and GSH, respectively. The combination mode of HL with Cu2+ was investigated in detail by Job plots, ESI-MS, FT-IR, and DFT studies. Probes HL and Cu2+-2HL showed relatively less toxicity and were employed for biological imaging in cells and zebrafish. Remarkably, the detection for endogenous GSH by this developed sensor platform implied great potential application prospect in cancer diagnosis. A highly selective fluorescent/colorimetric probe system for detecting Cu2+ and tumor biomarker glutathione. Image 1 • New chemosensor for colorimetric and fluorescent detection of Cu2+ and GSH. • The probe displays high selectivity, excellent sensitivity and short response time. • Fast recognition of Cu2+ and GSH can be achieved by naked eye. • Detecting endogenous and exogenous glutathione in living cells and zebrafish. • Cancer identification was achieved by endogenous GSH sensing. [ABSTRACT FROM AUTHOR]

A novel quinazolinone based turn-on fluorescence probe for sensitive monitoring hypochlorite was prepared using the mild condensation reaction between 2-(2′-hydroxyphenyl)-4(3H)-quinazolinone derivative and 4-methylbenzenesulfonyl hydrazide. The probe exhibited specific selectivity to ClO− with obvious optical signal changes from weak fluorescence at 560 nm to a strong fluorescence emission at 520 nm and color changes from colorless to yellow, which could be noticed by the naked eye. The detection limit toward hypochlorite is as low as 11.4 nM. Moreover, the probe could sensitively response to ClO− in living cells with satisfying imaging effect and has been successfully applied to the determination of ClO− in practical water samples, which indicated that the probe has certain application potential for hypochlorite monitoring. Unlabelled Image • A quinazolinone based fluorescent probe for detection of ClO− was designed and synthesized. • Probe QBH showed a rapid and remarkable fluorescence "turn-on" response to ClO−. • The QBH could detect ClO− quantitatively with a detection limit as low as 11.4 nM. • The sensing mechanism is analyzed through the NMR and MS spectra. • The probe was successfully applied to the determination of ClO− in practical water samples. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide shows great importance in various physiological and biochemical processes. The development of fluorescence probes for facile and efficient detection of H 2 S has attracted increasing attention of researchers. Herein, we synthesized two fluorescence probes based on simple naphthalene structure for detection of H 2 S. Upon reaction with H 2 S, the probe DN - DM exhibited a red fluorescence emission with large Stokes shift. The probe showed high sensitivity, pH insensitivity and good selectivity for H 2 S over other analytes including common biothiols. The detection mechanism was based on the thiolysis of the dinitrophenyl ether moiety, which was confirmed by 1H NMR spectral analysis. The DFT calculation was also performed for a deeper understanding of the photophysical properties. In addition, these probes showed good cell-membrane permeability and could be utilized for detection of H 2 S in living cells. Dimethylamino naphthalene-based fluorescent probes are designed and synthesized for detection of hydrogen sulfide in living cells. Unlabelled Image • Two fluorescent probes for H 2 S detection are designed and synthesized. • The probe DN-DM exhibits a red fluorescence emission upon exposure to H 2 S. • The probes show large Stokes shifts, high selectivity and sensitivity for H 2 S detection. • The probes have been successfully applied for imaging H 2 S in living cells. [ABSTRACT FROM AUTHOR]

In this study, a mitochondria-specific fluorescent probe for efficient ratiometric detection of Cys was designed and investigated. Probe 1 is composed of a xanthylene skeleton and a benzyl group containing an acryloyl moiety. The probe showed excellent water solubility, good selectivity and sensitivity toward Cys over other analytes, and afforded an extremely low detection limit of 33.7 nM. The possible detection mechanism was ascertained by HRMS analysis. Moreover, probe 1 had excellent mitochondrial-targeting ability (the Pearson's correlation coefficient was 0.96), and was capable of monitoring endogenous Cys in living HeLa cells by dual channel ratiometric bioimaging, demonstrating its significant potential in biological applications. Image 1 • A novel ratiometric and mitochondria-targetability fluorescent probe 1 with a xanthylene skeleton for Cys was developed. • Probe 1 showed excellent water solubility, high selectivity and sensitivity (detection limit of 33.7 nM) towards Cys. • Probe 1 could be successfully used for imaging cellular exogenous and endogenous Cys. [ABSTRACT FROM AUTHOR]

• A novel bifunctional fluorescent probe CBTA was developed. • CBTA showed high sensitivity and selectivity to HSO 3 − and N 2 H 4 in ultrafast time. • CBTA has low detection limits for bisulfite and hydrazine. • CBTA could visualize endogenous HSO 3 − in living cells. The probe CBTA is a novel bifunctional fluorescent probe that can detect bisulfite and hydrazine hydrate in a rational manner. And probe CBTA could specifically detect bisulfite and hydrazine hydrate among different analytes. Moreover, the response time of probe CBTA to SO 2 derivatives and hydrazine is extremely short, and the detection limits for bisulfite and hydrazine are as low as 5.6 nmol and 39 nmol. Cellular experiments also indicated that the probe CBTA was low in cytotoxicity and could be applied to cellular fluorescence imaging. Therefore, the probe CBTA could provide an efficient means for detecting SO 2 derivatives and hydrazine in vitro. [ABSTRACT FROM AUTHOR]