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Nitroreductase (NTR) is overexpressed in hypoxic tumor cells, which is closely related to inflammation, tumorigenesis, tumor invasion and metastasis. Therefore, developing fluorescence probes for detecting intracellular NTR sensitivity has great significance for diagnosis and treatment of tumors. Therefore, we designed a novel fluorescent probe (Pro-CN) based on julolidine skeleton for the detection of NTR. The probe could discriminate rapidly NTR from other biological species like sulfhydryl compounds and some ions. Meanwhile, a fine linear relationship between fluorescence intensity of the probe and NTR consistence has been observed with a very low detection limit of 4.4 ng/mL. In addition, Pro-CN was successfully applied in imaging endogenous NTR in Hela cells and living zebrafish. The excellent performance of the probe makes it have great potential for monitoring NTR in complex biological systems, and it also provides the possibility of its application in human health, disease diagnosis and treatment. [Display omitted] • Probe Pro-CN exhibits a turn-on fluorescence for sensing NTR. • Pro-CN is highly sensitive to sense NTR with a very low detection limit of 4.4 ng/mL. • Pro-CN was successfully applied for imaging endogenous NTR in living Hela cells and zebrafish. [ABSTRACT FROM AUTHOR]

The tertiary structures of HSA and BSA show a 76 % similarity, and the abnormal levels of HSA in body fluids can cause many diseases. Therefore, accurate quantification of HSA and effectively distinguishing HSA from BSA have significant application value in various fields. In this paper, a deep-red fluorescent probe, NITH , based on 1,8-naphthalimide, is demonstrated as a potential tool for accurately quantifying HSA and distinguishing HSA from BSA. The probe not only exhibits large stokes shift (100 nm) and low detection limit (4.61 μg/L, 0.0692 nM), but also effectively detects HSA by entering its hydrophobic cavity and emitting red fluorescence. Furthermore, NITH is capable of tracking the distribution levels of HSA within the cells through endogenous and exogenous cellular imaging. The application of NITH spans various environments such as cells, zebrafish, urine, and test strips, solidifying it as an effective tool for HSA detection. [Display omitted] • NITH has been synthesized by introducing benzothiazole sulfonate at the 3-position of 1,8-naphthalimide. • NITH can effectively distinguish HSA from BSA. • NITH can quickly identify, detect and track HSA in bioimaging. • NITH can be successfully applied in test strips, urine, cells and zebrafish imaging. [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 protein structure-dependent probe (OTB) for human serum albumin (HSA) was designed. Molecular simulation were used to assist probe design. OTB exhibited favorable selective HSA sensitivity and strong HSA binding ability. As a cationic molecule, OTB could form a stable amphipathic complex with water-soluble pillar [5]arene (WP5). More interestingly, the WP5-OTB complex possessed better HSA responsiveness and stronger HSA binding ability than OTB. The detection limit (3σ/k) of WP5-OTB towards HSA was determined to be 0.33 μM. WP5-OTB complex possessed excellent anti-interference ability in the selective recognition of HSA. Common commercial drugs, fluorescent amino acids, and fatty acids had almost negligible effect on the HSA responsiveness of the complex. The WP5-OTB complex self-assembled into supramolecular fluorescent probe in aqueous solution, and the supramolecular probe possessed favorable HSA-induced bioimaging property, pH-sensitive drug delivery property, and photodynamic activity. [Display omitted] • A cationic ICT probe OTB was designed by fully considering its interaction with HSA. • OTB exhibited favorable serum albumin sensitivity and strong HSA binding ability. • The WP5-OTB complex possessed better HSA responsiveness and binding ability than OTB. • The WP5-OTB complex self-assembled into supramolecular fluorescent probe in solution. • The supramolecular probe had good bioimaging and chemo-photodynamic therapy properties. [ABSTRACT FROM AUTHOR]

SO 2 , the fourth endogenous gaseous signaling molecule, plays an important role in cells. Besides, SO 2 derivatives are used as preservatives in food and drinks. To understand the level of SO 2 derivatives in body and food, we developed a FRET-based fluorescent probe CPO. CPO had high energy transfer efficiency and high selectivity toward SO 2 derivatives. It could fast respond toward SO 2 derivatives in an aqueous solution (3 min) and possessed a low detection limit (68 nM). Furthermore, the SO 2 derivatives in tap water, sugar, vermicelli and cells were detected by probe CPO. In addition, probe CPO had a high colocalization coefficient (0.95) for lipid droplets. [Display omitted] • A novel FRET-based water-soluble fluorescent probe for fast response to HSO 3 − was reported. • The probe had good sensitivity and selectivity to HSO 3 −. • The probe was applied to detect HSO 3 − in tap water, food and cells. • The probe preferred to load on lipid droplets with a high Pearson's coefficient. [ABSTRACT FROM AUTHOR]

The abnormality of Cys concentration in organism could lead to a series of diseases, so its effective detection is of great importance in disease diagnosis. Here we developed a novel ESIPT fluorescent probe HBT-IDAc based on the classic ESIPT fluorophore 2-(2′-hydroxyphenyl)benzothiazole (HBT) and indanone, which could selectively and sensitively detect Cys with a large Stokes shift up to 210 nm and the detection limit to 0.89 μM. In addition, the probe exhibited good anti-interference and low cytotoxicity, and has been successfully applied to monitor Cys in cells. • A novel ESIPT fluorescent probe for selective and sensitive detection of Cys was developed. • The probe has the large stokes shift (210 nm) and good LOD (0.89 μM) in aqueous environment. • The probe exhibits low cytotoxicity and has been applied for imaging Cys in cells. [ABSTRACT FROM AUTHOR]

Mercury ion (Hg2+) is highly toxic to the environment and organisms, therefore, monitoring and quantitative detection of Hg2+ is of great significance. In this work, a new fluorescent probe TPEH that integrated tetraphenylethene (TPE) and 2-(2 ′ -hydroxyphenyl)benzothiazole was designed and synthesised. In EtOH/HEPES (2:8, v/v, pH = 7.2) solution, TPEH displays fluorescence turn on detection of Hg2+ with the advantages of swift response (<100 s), high selectivity and strong disturbance-resistant, a large Stokes shift (220 nm), and low limit of detection (81.7 nM). The sensing mechanism was proved to be Hg2+-triggered releasing of the aggregation-induced emission (AIE)-active precursor compound 2. TPEH has been successfully applied to detect Hg2+ in seafood and tea, and image Hg2+ in living cells. In addition, TPEH can be used to detect the content of Hg2+ in actual water samples with the aid of smartphone. [Display omitted] • A new AIE-based fluorescent probe TPEH for Hg2+ detection has been developed. • TPEH has the advantages of rapid response (<100 s), a large Stokes shift (220 nm), and a low detection limit (81.7 nM). • TPEH can detect Hg2+ in seafood and tea, and image Hg2+ in living cells. • TPEH can detect Hg2+ in actual water samples with the help of smartphone. [ABSTRACT FROM AUTHOR]

Herein, we designed a potent ClO− probe named ETMC , which exhibited aggregation-induced emission (AIE) characteristic in solid state and water/EtOH binary solvent. Probe ETMC exhibited an colormetric from yellow to blue and ratiometric response to ClO− with high selectivity and sensitivity, and a low detection limit of 3.66 × 10−7 M. Moreover, probe ETMC could be applied to visibly and quantitatively detect the different concentraction of ClO− in test paper. Importantly, probe ETMC could effectively detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. Also, the sensing mechanism of probe ETMC for ClO− was confirmed by FT-IR, 1H NMR, HRMS, DLS, TEM and DFT calculation. In this work, probe ETMC, which exhibited aggregation-induced emission (AIE) characteristic in solid state and water/EtOH binary solvent was developed and could effectively detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. Also, the probe ETMC has been successfully applied in visibly and quantitatively detection the different concentraction of ClO−. [Display omitted] • A fluorescent probe ETMC with AIE effect was developed, which exhibited an colormetric and ratiometric response to ClO−. • The probe ETMC could be applied to visibly and quantitatively detect the different concentraction of ClO− in test paper. • The probe ETMC could detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. [ABSTRACT FROM AUTHOR]

Herein, a two-photon mitochondria-targeting fluorescent probe (TPNP) which can be activated by the azo reductase (AzoR) has been developed for imaging the hypoxic microenvironment of tumors in vivo. The probe TPNP showed a low detection limit (LOD = 1.85 eq), high selectivity, and considerable steadiness in different pH conditions (3.0–11.0). In living cells, it could co-locate with the commercial dye in the mitochondria (co-localization coefficient: 0.92) and indicate hypoxia in both one-photon and two-photon fluorescence imaging. Its AzoR-activation mechanism was further verified by the docking simulation as well as the experiments of adding AzoR or electron transporter inhibitors. Moreover, the in vivo real-time fluorescence imaging proved that TPNP could monitor hypoxia and the tumor progression in mouse tumor models. Overall, this designed probe exhibited high sensitivity, synthetic ease, and excellent fluorescent properties, which might therefore enlighten new ideas for the diagnosis of tumors in future studies. • A new hypoxia-sensitive fluorescent probe (TPNP) for tumor detection is reported. • TPNP exhibited high sensitivity, synthetic ease, and impressive fluorescent properties. • TPNP can monitor the presence of solid tumors in the xenograft mice model. [ABSTRACT FROM AUTHOR]

Abstract Recently, the fluorescence detection of H 2 S in biological systems has attracted the attention of many analytical chemists. However, most of H 2 S probes showed shorter fluorescence emission (<600 nm) with fluorescence intensity change induced by H 2 S, which has some disadvantages of shallower tissue penetration and bigger autofluorescence interference. Herein, we have rationally designed a near-infrared and ratiometric fluorescent probe (YC−1) for the detection of H 2 S based on isophorone. The detection process can be monitored by naked-eye. Addition of H 2 S, YC−1 showed that the emission ratios of fluorescence intensity at 540 and 660 nm (I540/I660) with an obvious enhancement from 0.05 to 13.3. Besides, the color of YC−1 changes from pink to yellow. As a probe for H 2 S, YC−1 exhibited better selectivity, better sensitivity and lower detection limits (0.17 μM). Moreover, YC−1 showed lower toxicity to HepG−2 cells and can be used for cell imaging. Graphical abstract Image 1 Highlights • 1. A novel ratiometric and near-infrared fluorescent probe for detecting H2S was developed. • 2. The probe showed higher selectivity and lower detection limit (0.17 μM) for H2S monitored by naked-eye. • 3. The probe can be used for monitoring exogenous and endogenous H2S in HepG-2 cells. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen sulfide (H 2 S) is a powerful toxin which has a strong stimulating effect on the eye, respiratory system and central nervous system. Therefore, it is essential to detect H 2 S in biological samples. Fluorescence imaging technology has the advantages of real-time and non-invasive, so it is very advantageous to detect H 2 S in living cells. In this work, we designed and synthesized a fluorescent probe (named ND-N 3) based on naphthalimide derivative with symmetric structure and double recognition sites. The fluorescence intensity at 532 nm of ND-N 3 obviously increased with the increase of H 2 S concentration. Apart from this, the probe showed excellent selectivity and rapid response time. More importantly, ND-N 3 can be used to detect endogenous/exogenous H 2 S in living cells. Graphical abstract Image 1 Highlights • A novel H 2 S fluorescent probe (named ND-N 3) with dual-sites based on naphthalimide derivative. • The application of the probe for selective detection H 2 S in HepG-2 cells has been successfully demonstrated. • The probe has a good linear relation and limit of detection is only 0.02 μM. [ABSTRACT FROM AUTHOR]

Abstract A new imidazo [1,5- a ]pyridine-based fluorescent probe, named MZC-AC, is developed for the detection of cysteine (Cys) based on an excited state intramolecular proton transfer (ESIPT) mechanism. The probe MZC-AC uses an acrylate moiety as the ESIPT blocking group as well as the recognition site. Upon the treatment with Cys, MZC-AC exhibits a dramatic fluorescence enhancement (85-fold) and a large Stokes shift (166 nm). The limit of detection obtained from fluorescent titration was as low as 0.07 μM. MZC-AC displays highly sensitive and selective response to Cys over homocysteine (Hcy) and glutathione (GSH). Significantly, MZC-AC could be used to detect Cys in living cells. Graphical abstract Image 1 Highlights • An imidazo [1,5- a ]pyridine-based fluorescent probe MZC-AC was developed. • MZC-AC can detect cysteine with high sensitivity and selectivity. • MZC-AC shows a large Stokes shift. • The limit of detection was as low as 0.07 μM. • MZC-AC can be applied in imaging intracellular cysteine in living cells. [ABSTRACT FROM AUTHOR]

The abnormal expression of cytochrome P450 2J2 (CYP2J2) is closely related to the proliferation of human cancer cells. In this study, a red-emitting probe with an aggregation-induced emission (AIE) effect for the quantification of CYP2J2 was developed by modifying the typical AIE fluorescent group tetraphenylethylene (TPE) through two-step synthesis. Upon addition of CYP2J2, the probe underwent O-demethylation and spontaneously 1,6-elimination reactions of p-hydroxybenzyl that allowed it to alter its photophysical properties, thus realizing light-up detection of CYP2J2 with extremely large Stokes shift (236 nm), excellent sensitivity and selectivity, low detection limit (1.09 nM). Moreover, this new AIE-active probe with good biocompatibility was admirably employed to tracking endogenous CYP2J2 in living cells. • An AIE-based fluorescent probe (TPE-Bn) was designed to detect CYP2J2. • This probe showed significant Stokes shift (236 nm), good photostability, excellent sensitivity and selectivity, and low cytotoxicity. • This probe can be used to visualize endogenous CYP2J2 in living cells and tissues. [ABSTRACT FROM AUTHOR]

A simple fluorescent probe (TPE-1) based on the combination of tetraphenylethene (TPE) and 2-(2′-hydroxyphenyl)benzothiazole (HBT) was synthesized. TPE-1 possesses both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) characteristics. The TPE-1 aggregates exhibited rapid (10 s) and highly selective recognition of Cu2+ in THF/H 2 O (1:9, v/v, HEPES 20 mM, pH = 7.4) solution, and was induced an "on-off" change in the fluorescence. TPE-1-Cu 2+ complexes generated in situ can also be used as sensing ensembles for highly selective detection of H 2 S by Cu2+ displacement. As a result, the fluorescence of TPE-1 was recovered again, and an "on-off-on" fluorescence variation was used to relay Cu2+ and H 2 S recognition. The detection limits of the probes for Cu2+ and H 2 S are 9.91 × 10−8 M and 3.80 × 10−7 M, respectively. In addition, the probes can be applied to detect Cu2+ and H 2 S in some food samples and can also be applied to cell imaging experiments. Relay recognition of Cu2+ and H 2 S by a fluorescent probe regulated by AIE and its application in food and cell imaging. [Display omitted] • An AIE-based fluorescent probe TPE-1 was designed and synthesized. • TPE-1 can relay identify Cu2+ and H 2 S with high sensitivity, high selectivity, large Stokes shift, and low detection limit. • TPE-1 can rapidly relay responses to Cu2+ and H 2 S with on-off-on fluorescence changes. • TPE-1 is suitable to assay the Cu2+ and H 2 S level in water, seafood, tea and red wine samples. [ABSTRACT FROM AUTHOR]

In this work, a colormetric fluorescent probe named NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed based on 2-hydrazinobenzothiazole and 6-methoxy-2-acetonaphthone for sensing hypochlorous acid (HClO) with high selectivity and sensitivity (detection limit: 1.7 nM). Also, NMH had a strong anti-interference effect and a fluorescence color change in the solution which can be seen by the"naked eye". Moreover, NMH could be applied to detect ClO− in tap water and test paper. In addition, cell imaging experiments showed that probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. In this work, probe NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed and could be applied to detect ClO− with colormetric response in tap water, test paper and living cells. [Display omitted] • A selective fluorescent probe NMH with aggregation-induced emission characteristic was developed by one step reaction. • The probe NMH could be widely used as a "naked eye" probe for detecting ClO− by the color changes from purple to blue. • The probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

In view of crucial role of biothiols in various physiological processes, exploitation of convenient and efficient sensing method for the biothiols detection is of terrific scientific significance. Although recently some related work has been done, the application of fluorescent probes for rapid simultaneous detection of biothiols in both vivo and vitro has been rarely reported. In this work, we successfully designed and developed a simple fluorescent probe DEMCA-NBSC based on coumarin fragment, which presents remarkable emission enhancement and exhibits yellow-green fluorescence with a 365 nm UV lamp irradiation after addition of biothiols (Hcy/Cys/GSH), and the intensified emission response is ascribed to biothiols induced the cleavage of NBSC group to form a fluorescent compound DEMCA-OH , which exhibited a strong aggregation induced emission (AIE) property. It is worth mentioning that DEMCA-NBSC exhibits rapid response (within 3 min), high selectivity, outstanding sensitivity, lower the detection of limit (0.236 μM, 0.223 μM, 0.365 μM for Cys, GSH and Hcy, respectively) to biothiols, and DEMCA-NBSC possesses low toxicity and high sensitivity when used in biological systems, thus, it can successfully achieve rapid biothiols detection and intracellular imaging by difference in fluorescent signals. This probe provides an effective tool for the real-time detection of biothiols in both vivo and vitro. [Display omitted] • Designed a novel AIE "turn on" fluorescent probe DEMCA-NBSC for biothiols detection in both vivo and vitro. • Detection abilities for biothiols with high sensitivity, specifity and lower limit of detection (LOD). • The probe DEMCA-NBSC realized detection and recognition for biothiols with a rapid response time. [ABSTRACT FROM AUTHOR]

Biothiols play an important role in cell protein metabolism and signal transduction, especially Hcy was considered as a new risk factor closely related to many diseases. However, there remain some limitations in selectively detecting Hcy due to its structural similarity to Cys. It is urgent for us to develop a novel indicator to study the pathological process of Hcy. Herein, we constructed a new fluorescent probe TCF-SBD composed of tricyanofuran fluorophore and SBD reaction site for detecting Hcy. The probe TCF-SBD exhibited a strong yellow emission response to Hcy in an "off-on" manner, and showed good selectivity for Hcy over Cys and GSH. The sensing mechanism was confirmed by HPLC, NMR titration and DFT studies. The probe was sensitive to the detection of Hcy with LOD low to 0.23 μM. The powerful probe TCF-SBD succeeded in real-time and selectively visualizing Hcy in living cells. [Display omitted] • Fluorescence probe based on substitution-rearrangement process was synthesized for selective detection of Hcy. • The probe displayed high selective and sensitive for Hcy (detection limit is 0.23 μM). • The probe was applied for fluorescence imaging of exogenous Hcy in living cells. [ABSTRACT FROM AUTHOR]

A series of fluorescent dyes based on 2-(2′-hydroxyphenyl)benzothiazole derivatives were designed and synthesized. Because of their structural characteristics of "AIE + ESIPT", they have long-wavelength emission and a larger Stokes shift. The fluorescent probe HBTN-Y was prepared based on the fluorescent dye HBTN. Probe HBTN-Y can recognize cysteine (Cys) with a high selectivity, "OFF-ON" fluorescence response, a large Stokes shift (263 nm) and long-wavelength emission (637 nm) in MeCN/H 2 O (1:1, v/v, PBS 20 mM, pH = 8.4) solution. The probe exhibits good anti-interference ability, a low detection limit of 6.51 × 10−6 M, and is suitable for application at near neutral and weak alkaline pH (7–9) conditions. Moreover, HBTN-Y is applicable to image Cys in living MCF-7 cells. A new fluorescence "AIE + ESIPT" characteristics probe HBTN-Y for the detection of cysteine has been developed. [Display omitted] • A series of fluorescent dyes with "AIE + ESIPT" features were synthesized. • A cascade reaction-based fluorescence "turn on" probe (HBTN-Y) has been developed. • HBTN-Y displays highly selective recognition for Cys in an aqueous solution. • HBTN-Y can detect Cys with a long wavelength emission and a large Stokes shift. • HBTN-Y is capable of imaging Cys in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

Carboxylesterases (CEs) are involved in biotransformation of numerous drugs, environmental toxicants, and carcinogens containing ester groups. Abnormal CEs levels are associated with various diseases. Herein, we developed a novel water-soluble merocyanine-based probe 1 to detect CEs activity using acetate ester as a recognition site. The notable emission at 510 nm of the probe in neat aqueous solution was partially quenched and red-shifted to 580 nm after adding CEs. The fluorescent ratiometric response of 1 toward CEs activity is sensitive (with the detection limit of 0.98 × 10−6 U/ml), rapid (within 10 min), and effective in a wide pH range (4.0–10.0). Due to the existence of morpholine as a lysosome-targeting group, the probe was successfully utilized to monitor lysosomal CEs activity. More importantly, the probe was successfully applied to detect and image carboxylesterase activity in zebrafish. [Display omitted] • A water-soluble lysosome-targetable fluorescent probe has been developed. • The probe could monitor carboxylesterases activity with the detection limit (0.98 × 10−6 U/mL) in neat aqueous solution. • The probe works within a wide pH rang of 4.0–10.0 along with a rapid hydrolytic process within 10 min. • The probe has been successfully sensing carboxylesterases activity in lysosomes of living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Here, a coumarin-based probe 4-chloro-3-formyl-2-oxo-2H-chromen-7-yl acrylate (named CFCA), which performed high efficient and specific recognition for cysteine (Cys), was successfully synthesized and characterized by NMR and MS. The CFCA probe showed colorimetric and "turn-on" fluorescent signals to Cys, and its color changes could be recognized by naked eyes. CFCA responded to Cys with the characteristics of rapid response time (less than 40 s), high selectivity, and excellent anti-interference. Among all kinds of samples, only Cys could significantly enhance the fluorescence intensity of the solution, which was not affected by the presence of other interferences. At the same time, within a certain concentration range, there was a good linear relationship between relative intensity of fluorescence and Cys concentration. The detection limit has been calculated to be as low as 0.33 μM. And the sensing mechanism of CFCA with Cys has been well confirmed by 1H NMR and HR-MS spectra. Moreover, the fluorescence probe CFCA was successfully used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. • A coumarin-based probe CFCA was successfully prepared, synthesized, and applied for Cys detection. • CFCA can perform high efficiency and specificity colorimetric and fluorescent double signal recognition for Cys. • CFCA has been used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. [ABSTRACT FROM AUTHOR]

Endogenous peroxynitrite a highly reactive oxidant plays significant roles in various physiopathological processes in living organisms. Therefore, sensing and monitoring of peroxynitrite with accurate detection specifically, is an immense challenge. To address this issue, we synthesized a water soluble, mitochondria-targeting "turn-on" fluorescent probe (BICBzBF) for the detection of mitochondrial peroxynitrite. BICBzBF (pale yellow) demonstrated high sensitivity and selectivity in fluorometric tracing of peroxynitrite over other ROS/RNS tested. This arylboronate-masked probe responds to peroxynitrite, resulting in the corresponding phenol derivative; a strong fluorescence accompanied a change to red rose as observed by the naked eye. The probe responds to peroxynitrite within <120 s, shows a lower nanomolar detection limit (60.5 nM), exhibits a remarkable ca. 32-fold intense increase. Taking these features fully into account, BICBzBF was evaluated in how it monitors peroxynitrite exogenously and endogenously. Moreover, BICBzBF successfully traced ONOO− in inflammatory living zebrafish animal model which are chemically induced for inflammation. The results obtained in both exogenous and endogenous studies demonstrate that BICBzBF actively detects ONOO−; major accumulation in retina and intestine indicate BICBzBF could serve as a potential molecular imaging tool in investigations of the role(s) played by peroxynitrite in a variety of physiological and pathological contexts. • BICBzBF allows for rapid detection of ONOO− (<120 s) with remarkable 32-fold enhancement and detection limit (60.5 nM). • It possessed satisfactory photostability, showed large stroke shift (126 nm). • It actively monitors ONOO− exogenously and endogenously in live cells as well as in inflammatory living zebrafish. • Vasculature and neuronal development of transgenic live zebrafish shows no significant toxic exposure. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an important endogenous gaseous signal transmitter. In this work, a novel near-infrared fluorescent probe DS for the detection of H 2 S was designed and synthesized based on the theoretical analysis. The optical investigation results showed that H 2 S could be detected quantitatively in the concentration range 0.0–10.0 μM, and the detection limit was calculated to be 9.0 nM (fluorescence intensity) and 88.2 nM (absorbance). Furthermore, probe DS was successfully applied for imaging H 2 S in living cells, which exhibited the admirable advantages of membrane permeability and biocompatibility. Moreover, a portable fluorescence nanofibrous film prepared by electrospinning was successfully constructed for the visual detection of H 2 S under the UV lamp, indicating its potential applications in the area of portable membrane sensing. Image 1 • A novel near-infrared fluorescent probe based on DCM scaffolds for H 2 S was developed. • The probe displayed the detection limit of 9.0 nM for H 2 S. • The probe was successfully applied for imaging H 2 S in living cells. • The probe showed potential applications in the area of portable membrane sensing. [ABSTRACT FROM AUTHOR]

Biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play important roles in various physiological and pathological processes. However, it is still a great challenge to selectively detect Cys/Hcy and GSH in biological samples due to the similarity of structures and re-activities of these biothiols. In this paper, a new dual-channel near infrared-7-nitro-1,2,3-benzoxadiazole (NIR-NBD) fluorescent probe has been developed for the discriminative detection of Cys/Hcy and GSH. The probe is composed of two functional parts: a near-infrared dye of dicyanoisophorone, as fluorophore precursor, and NBD as both fluorophore precursor and sensing group. It was observed that NIR-NBD probe displayed two different fluorescent signals in response to biothiols, green-red for Cys/Hcy and red for GSH. It also showed a near infrared emission (756 nm), low detection limit, fast response, high stability, selectivity and sensitivity. Furthermore, NIR-NBD was effectively applied for the discriminative detection of Cys/Hcy and GSH in HeLa cells. Image 1 • A novel dye of dicyanoisophorone derivative was designed and synthesized. • A dual-channel fluorescent NIR-NBD probe was developed for the discriminative detection of Cys/Hcy and GSH. • The NIR-NBD probe was successfully used for imaging Hcy/Cys and GSH in living cells. [ABSTRACT FROM AUTHOR]

A novel quinoline-fused Rhodamine dye is designed and synthesized to achieve near-infrared fluorescent emission by expanding the π-conjugated system. Ratiometric fluorescent probe (RhQ) is further constructed by introducing the 3,5-ditrifluormethylthiophenol moiety into dye through a thioester bond to take advantage of spirocyclization open-ring states of Rhodamine platform. The probe exhibits remarkable dual-channel fluorescence response toward Cys/Hcy in aqueous solutions between near-infrared and visible emission, arising from the formation of closed spirolactam configuration disrupting molecular π-conjugation system. RhQ is highly selective and sensitive to Cys/Hcy with detection limits of 0.12 μM and 0.25 μM for Cys and Hcy, respectively. Moreover, imaging in cellular experiment indicates that probe displays excellent mitochondrial targeting ability, lower cytotoxicity and ratiometric responses with two well-defined emissions to ensure exactly comparison and quantitative analysis of Cys/Hcy changes in the cell. Image 1 • A novel quinoline-fused rhodamine dye is designed and applied to construct the ratiometric fluorescent probe (RhQ). • Probe RhQ displays remarkable ratiometric fluorescent change with high selectivity and sensitivity toward Cys/Hcy. • Probe RhQ can be used to visualize monitor Cys concentration changes in mitochondria. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2) as a common environmental pollutant, participates in a variety of physiology and pathological processes in vivo. Lysosomes are considered to be cleaners of living cells and play a vital role in the process of metabolism. Exposure to excess SO 2 will result in the increase risk of lysosomal dysfunction and induce multiple diseases. Herein a smart fluorescent probe LYSO-SO 2 is developed, which achieved the ratio (F 561 nm /F 634 nm) identification of SO 2 in vitro. LYSO-SO 2 showed high sensitivity (detection limit 15.8 nM), rapidly response (within 5 s), and excellent selectivity. Additionally, this probe LYSO-SO 2 has been successfully applied to the ratio monitoring SO 2 in lysosomes which may provide an effective quantitative method for studying the physiological and pathological functions of SO 2 in living cells. • A ratiometric fluorescent probe LYSO-SO 2 was proposed, which achieved the ratio (F 561 nm /F 634 nm) identification of SO 2. • Probe LYSO-SO 2 showed excellent sensitivity (15.8 nM), high selectivity and rapid response (within 5 s). • Probe LYSO-SO 2 was successfully applied to the detection of lysosomes SO 2 in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

In this work, we have developed a new carbazole-based fluorescent probe (E)-1-methyl-4-(2-(5-(9-phenyl-9 H -carbazol-3-yl) thiophen-2-yl)vinyl)pyridin-1-ium (PCTP) for ratiometric and colormetric ClO− sensing. PCTP displayed red emission due to the intramolecular charge transfer (ICT) effect of phenylcarbazol moiety, while this effect can be rapidly weakened and led to the significant fluorescence change (from red to green) in the presence of ClO−. PCTP is more highly selective and sensitive towards ClO− detection than other various biological related species. The detection limit (LOD) was calculated to be 10.8 nM. More importantly, PCTP has been successfully applied in ClO− imaging in living cells and zebrafishes. • A novel colormetric and ratiometric fluorescent probe (PCTP) was designed and synthesized for detecting ClO−. • PCTP displays a low detection limit (10.8 nM) and large Stokes shift (124 nm). • PCTP successfully performed well in sensing ClO− in living cells and zebrafishes. [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]

A fast-responsive fluorescent probe PI-Py was designed and synthesized for sensitive and selective detecting hypochlorite (ClO−). The probe PI-Py was intrinsically non-fluorescent due to the PET effect of the phenothiazine moiety. After reacting with ClO−, the PET effect was blocked, and a strong green emission of the BODIPY unit was recovered. The probe PI-Py showed an excellent selectivity towards ClO− in comparison of other ROS. The limit of detection for ClO− was calculated to be 1.7 nM, proving the probe's high sensitivity. Moreover, the probe PI-Py has been proved to be effective in visualizing the variations of exogenous ClO− in living HeLa cells. A co-localization study employing Mito Tracker red reveals that the PI-Py is specifically located in the mitochondria. A new BODIPY-based fluorescent probe for ClO− was developed successfully. This probe can be used in visualizing the changes of exogenous ClO− in the mitochondria. Image 1 • A novel BODIPY-based fluorescent probe PI-Py was synthesized. • The probe PI-Py showed an excellent selectivity and sensitivity towards ClO−. • Fluorescent titrations, MS spectra support a PET OFF-ON mechanism. • Living cells imaging for exogenous ClO− located in the mitochondria was observed. [ABSTRACT FROM AUTHOR]

Herein, a novel cyclometalated iridium (III) complex (Ir-1) with good water-solubility was designed and synthesized to sensitively detect hypochlorite (ClO−) in aqueous buffer solution. The sensor Ir-1 was prepared by incorporating a methacrylate group into cyclometalated ligands, which was a specific response site toward ClO− through an oxidation process. Ir-1 displayed strong emission at 615 nm, while significant fluorescence quenching was observed upon addition of ClO− with a low detection limit of 0.41 μM. Moreover, probe Ir-1 exhibited a rapid response (<30 s) for ClO− with high selectivity over potentially competing species. The sensing process was evidenced by NMR and MS characterization. Further application in bioimaging of ClO− was successfully performed in living HepG2 cells. Image 1 • A water-soluble fluorescent probe based on cyclometalated iridium (III) complex was designed and synthesized. • The probe displayed a fast response toward ClO− (<30 s) with a low detection limit of 0.41 μM. • The probe showed high selectivity toward ClO− over other reactive oxygen species. • The probe was successfully applied for bioimaging of ClO− in living cells. [ABSTRACT FROM AUTHOR]

A colorimetric and ratiometric fluorescent probe DTF for HSO 3 − was synthesized from natural and renewable nopinone. The fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time (60 s). The detection process was accompanied with the visible color change from yellow to colorless and the fluorescent color change from green to blue. The fluorescence intensity ratio (F 430 /F 520) was linear with the concentration of HSO 3 − in the range of 0–80 μM, with a limit detection of 79.2 nM. The sensing mechanism was confirmed by 1H NMR and HRMS spectra. Above all, the novel fluorescent probe DTF was successfully applied to determine the concentration of HSO 3 − in food samples and HeLa cells. In this manuscript, we designed and synthesized a novel nopinone-based fluorescence probe for colorimetric and ratiometric detection of HSO 3 −, with high sensitivity, good selectivity and fast response time. The novel probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. Image 1 • This is the first report that the synthesis of HSO 3 −-specific fluorescence probe based on nopinone. • The colorimetric and ratiometric fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time. • Probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is an important kind of gasotransmitter associated closely with pathogenesis of inflammation and detection of CO in living systems is of great attraction in recent years. To data, accurate fluorescent detection of CO in vivo is still challenging. In this study, we reported for a new simple NIR fluorescent probe CO–B with stable allyl ether as the specific CO-reactive site. The detection mechanism of this probe has been proven through the rearrangement of conjugated π-electron system. CO–B featured large Stokes shift (135 nm), low toxicity, good sensitivity (detection limit of ∼110 nM) and selectivity for CO detection. CO–B successfully served as an indicator for imaging CO in Heme-stimulation inflammation model. Finally, CO–B was also employed for in vivo imaging CO in living mice with low background interference. All together, probe CO–B was potentially valuable as a promising tool for monitoring and tracking CO in preclinical applications. Image 1 • A new stable NIR fluorescent probe CO–B for CO detection was reported. • CO–B was easy-to-get with only two step reactions. • CO–B featured large Stokes shift (135 nm), low toxicity, good sensitivity and selectivity for CO detection. • CO–B was successfully employed for imaging CO in cells and in living mice. [ABSTRACT FROM AUTHOR]