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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]

[Display omitted] • A mitochondria-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the mitochondria of living cells. Cysteine (Cys) is of great significance in biological systems and in the process of mitochondrial function. Highly selective and specificity recognizable probes for mitochondrial Cys are still in demand. In this work, a new fluorescent probe for detecting mitochondrial Cys was developed based on a rhodamine derivative. In this probe, acrylate unit was selected as group of Cys recognition and quaternized pyridinium moiety was utilized as mitochondrial targeting group. The probe showed colorless in daylight and extremely weak fluorescence in 365 nm due to its spirolactone structure when Cys did not exist. In the presence of Cys, the probe exhibited orange in daylight and produced intensely green fluorescence in 365 nm owing to the formation of the conjugated xanthene structure. The probe exhibited specific recognition for Cys. There was an excellent linear relationship between fluorescence intensity at 540 nm of the probe and the Cys concentration from 4.0 × 10-8 to 1.0 × 10-5 mol⋅L-1. And the detection limit was estimated to be 1.57 × 10-8 mol/L. Moreover, the probe was almost non-cytotoxic, possessed targeting-mitochondria ability and could sense Cys at the cellular level. The good bioimaging ability makes the probe a potential tool for studying mitochondrial Cys in biological samples. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an important endogenous gasotransmitter and has been implicated with a variety of biological processes. The development of an efficient method for monitor H 2 S fluctuations in biological systems is of great significance to understand its roles in physiological and pathological conditions. In this work, two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy for H 2 S detection with turn-on fluorescence signals were reported. Interestingly, SNARF-SeSPy exhibited excellent anti-interference via dual selenium-sulfur exchange reaction even in the presence of high concentrations of thiols, whereas SNARF-SSPy did not sense H 2 S in the same condition. Additionally, in the present of H 2 S, SNARF-SeSPy showed a rapid response and excellent sensitivity with a detection limit of 34 nM. Most importantly, SNARF-SeSPy featured low cytotoxicity and could be employed to detect and image exogenous/endogenous H 2 S in living cells and zebrafish. Image 1 • Two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy have been designed for efficient detection of H 2 S. • By comparing the two probes, only SNARF-SeSPy exhibited excellent anti-interference even in the presence of high concentration of thiols. • Results of imaging H 2 S in living cells and zebrafish demonstrated that SNARF-SeSPy could be employed to track exogenous and endogenous H 2 S in vitro and in vivo. [ABSTRACT FROM AUTHOR]

A near-infrared turn-on two-photon fluorescent probe ST-BODIPY for glutathione-specific detection was designed and synthesized by attaching triphenylamine to BODIPY skeleton through the Knoevenagel condensation to prolong the maximum emission wavelength to the NIR region. And 2,4-dinitrobenzenesulfonyl group (DNBS), as the fluorescence quencher and thiol recognition moiety, was modified in 8 position of BODIPY. In the presence of GSH, the probe afforded an "off-on" signal response with a significant NIR fluorescence enhancement centered at 719 nm accompanying by quantum yield increased to 0.44, which was ascribed to the glutathione-induced S N Ar (aromatic substitution) reaction. Surprisingly, we found that the probe could discriminate GSH from other biothiols including Cys and Hcy upon the addition of intracellular concentrations of them. Time-dependence also demonstrated that the probe could distinguish GSH from Cys and Hcy under physiological environment. The limit of detection (LOD) for GSH was calculated as 25.46 nM from the titration experiments, which is lower than most previously reported GSH-selective probes. Under the Ti:sapphire pulsed laser's 800 nm irradiation, ST-BODIPY toward GSH generated an "off-on" signal response with a significant enhancement of fluorescence emission at 719 nm after treatment with GSH. Besides, the 2PA cross section value (σ 2) was calculated to be 410 GM, suggesting that it could not only function well as an excellent two-photon fluorescent probe for the detection of intracellular GSH, but also be applied for two-photon imaging with high sensitivity in living cells. Moreover, ST-BODIPY probe has been successfully employed for monitoring exogenous and endogenous GSH in MCF-7 cells with satisfying results, perhaps it was feasible for detecting abnormal contents of GSH in a biological system and accomplishing the goal of maintaining normal human activities. Unlabelled Image • ST-BODIPY was designed by attaching triphenylamine to BODIPY skeleton through Knoevenagel condensation to afford the NIR dye. • Emission wavelength of ST-BODIPY reached NIR region which was at 719 nm. • ST-BODIPY was served as two-photon fluorescent probe with large 2PA cross section value (σ 2) of 410 GM. • ST-BODIPY was applied for endogenous and exogenous cell imaging. [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]

For highly sensitive and selective detection of ClO− over other reactive oxygen species (ROS) and anions, a fluorescent probe MN-BODIPY by introducing a morpholine group into the 8-position of BODIPY which could be used for targeting lysosome and improving water solubility was designed and synthesized. As a result of the C=N isomerization mechanism at 2-position of BODIPY, the probe alone generated extremely weak fluorescence. However, in the presence of ClO−, the probe exhibited a dramatic enhancement of fluorescence intensity by a 29-fold increase at 530 nm accompanying with quantum yield changing from 0.03 to 0.25. Accordingly, the probe displayed fast response for ClO− within 60 s. The limit of detection (LOD) for ClO− was calculated as 16.5 nM from the titration experiments, which is lower than most previously reported ClO−-selective probes. Moreover, MN-BODIPY had been successfully employed for monitoring exogenous and endogenous hypochlorous in MCF-7 cells with satisfying results, perhaps it was feasible for detecting abnormal contents of hypochlorous in a biological system and accomplished the goal of maintaining normal human activities. At last, the fluorescence imaging showed that MN-BODIPY was capable of localizing lysosomes in living cells. Image 1 • MN-BODIPY displayed fast response towards ClO− within 60 s. • MN-BODIPY recognized ClO− with lower limit of detection of 16.5 nM. • MN-BODIPY was applied for intracelluar ClO− bioimaging. • MN-BODIPY could target lysosome. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two ratiometric fluorescent probes (Phe-HBT and Me-HBT) were developed to detect N 2 H 4 with high sensitivity. • The limits of detection are down to 80.6 nM for Phe-HBT and 99.2 nM for Me-HBT. • Smartphone and test kit applications were constructed for visual, rapid, and real time N 2 H 4 detection. • These probes are capable of on-site detection of N 2 H 4 in soil, sewage water, and food samples. • The probes can be used for monitoring vapor N 2 H 4 and cell imaging experiments. Hydrazine (N 2 H 4) is a toxic compound widely used in agricultural, chemical, pharmaceutical, and other industrial processes. It causes serious pollution to air, soil, and water. Therefore, the detection of N 2 H 4 is one of the prime scientific interests. In this study, two novel reaction-based ratiometric fluorescence probes (Phe-HBT and Me-HBT) for the selective and sensitive detection of N 2 H 4 are reported. The present approach, including the cyclization reaction induced by N 2 H 4, enables to visualization of N 2 H 4 at low levels by naked eyes under daylight or UV light with a fast response time of about 8.0 min for Phe-HBT and 16.0 min for Me-HBT. The detection limits of the probes were calculated to be 80.6 nM for Phe-HBT and 99.2 nM for Me-HBT. Both the probes displayed high specificities for N 2 H 4 among the tested potential competing analytes. Both probes were applied to detect aqueous trace N 2 H 4 in various samples such as food, soil, sewage water and living cells. Moreover, the detection of N 2 H 4 was successfully tested by smartphone application as well as the detection of gaseous N 2 H 4 by the modified fabric, showing its potential value in practical applications. [ABSTRACT FROM AUTHOR]

• A new mitochondria-targeted fluorescent probe ZZY for the reversible recognition of SO 2 and FA was developed. • Probe ZZY showed good spectral performance for the reversible recognition of SO 2 and FA. • Probe ZZY exhibited low cytotoxicity and could be used to image SO 2 and FA reversibly in mitochondria. Sulfur dioxide (SO 2) and formaldehyde (FA) are the main contaminants emitted by factories and their interaction could produce secondary organic aerosols which are harmful to human health. In biological systems, SO 2 and FA levels are closely associated with many biological diseases. To explore the specific functions played by SO 2 and FA in vivo, a new fluorescent probe ZZY that can reversibly recognize SO 2 and FA in mitochondria was devised and synthesized. Probe ZZY showed advantages of great selectivity, good sensitivity and low cytotoxicity and the detection limit is 0.447 μM of SO 2. In addition, probe ZZY could reversibly recognize SO 2 and FA. More importantly, the probe showed good biocompatibility and could successfully perform reversible imaging of SO 2 and FA in mitochondria of living cells. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel fluorophore (NAP-PMA) has been constructed through appending 2-pyridinemethanamine to naphthalimide. The air and moisture stable fluorophore were adopted as a colorimetric and fluorometric probe for palladium cation, revealing simultaneously good selectivity, high sensitivity and low detection limit (22.5 nM). Moreover, NAP-PMA not only exhibited a visible naked-eye color change from yellowish green to pink, but also displayed highly selective recognition to palladium acetate. In addition, NAP-PMA could be used as paper strips to quantitatively detect Pd2+ in water. Surprisingly, the developed sensing platform NAP-PMA-Pd is capable of detecting CO in living cells by "turn on" mode with high selectivity and stability, providing a potential real-time monitor for CO-involved reactions in biological systems. A colorimetric and fluorometric naphthalimide-based probe, paper strips for palladium detection and CO cell imaging is reported. [Display omitted] • A colorimetric and fluorometric probe was constructed through appending 2-pyridinemethanamine to naphthalimide. • It can realize visual and fluorescence recognition specific for palladium acetate. • The probe exhibited record low detection limit as 22.5 nM together with good selectivity. • Paper strips detection of palladium cations in aqueous media was realized. • A sensing platform was exhibited for imaging of CO in living cells. [ABSTRACT FROM AUTHOR]

A naphthalimide-rhodamine probe for detecting Hg2+ was designed based on FRET mechanism, and the application in bioimaging and keypad lock were studied. [Display omitted] • A ratiometric and colorimetric probe of Hg2+ based on naphthimide and rhodamine was synthesized. • The detection mechanism had been verified by NMR, ESI-MS and HPLC spectra. • The probe can be used to construct molecular keypad lock and cell imaging. A novel FRET-based ratiometric fluorescent probe (Ro1) based on rhodamine and naphthalimide groups was designed and synthesized. The probe displayed high selectivity and sensitivity to Hg2+ and the significant color changed from yellow to pink could enable naked-eye detection of Hg2+. Ro1 also showed rapid respond to Hg2+ within 60 s with the limit of detection was 0.75 μM. The possible mechanism of probe Ro1 for detecting Hg2+ was investigated by using 1H NMR, ESI-MS and HPLC spectra. Further, Ro1 was designed as a molecular keypad lock with different sequences of Hg2+ and Cu2+ chemical input. Moreover, fluorescence imaging experiment of Hg2+ in living Hela cells demonstrated its potential applications in biological systems. [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]

The phenolphthalein-based Schiff base fluorescent probe (PASB) was successfully applicable to detect Al3+ and PPi in food samples and cells. [Display omitted] • A novel phenolphthalein-based fluorescent probe PASB for detection of Al3+ and PPi was synthesized and characterized. • A dual response was established based on "Off–On–Off" strategy for detection of both Al3+ and PPi with the detection limits in the nanomolar range. • PASB cloud not only detect Al3+ in real samples, but also visualize Al3+ in living cells. • PASB is capable of imaging PPi by the PASB- Al3+ ensemble in biological systems. Herein, we report a new phenolphthalein appended Schiff base (PASB) as reversible fluorescent sensor for the detection of pyrophosphate (PPi) ions through the metal displacement mechanism. PASB showed sensing exclusively toward Al3+ ions in DMF/H 2 O (v/v = 1/4, pH 5.5) solution, which resulted in a significant fluorescence enhancement at 540 nm. The 1: 2 binding stoichiometry for the complex formation between PASB and Al3+ was confirmed by Job's plot and mass spectroscopic studies. Moreover, a solution of the in situ formed PASB–Al3+ complex displayed a high selectivity to PPi. The addition of PPi to PASB-Al3+ ensemble significantly quenched its fluorescence. Thus, a dual response was established based on "Off–On–Off" strategy for detection of both Al3+ and PPi. The detection limit is 5.86 nM and 26 nM for Al3+ and PPi, respectively. On this basis, we use PASB to detect Al3+ in food samples. Furthermore, PASB was successfully applicable to detect Al3+ and PPi for intracellular imaging in Human liver cancer cells. [ABSTRACT FROM AUTHOR]

The fluorescent probe, GXY-ADP-2, with xanthene structure as the fluorescent core was designed and prepared for the selective detection of peroxynitrite (ONOO−). ONOO− can be produced endogenously and exogenously and is a strong oxidant with a short half-life. Oxidative modifications of biomolecules, that can be attributed to the formation of ONOO−, occur in the reactions of biomolecules with secondary ONOO−-derived radical oxidants. Therefore, it is very important to develop a specific fluorescent probe for detecting ONOO− to monitor oxidative stress state. The excitation wavelength and emission wavelength of the probe are 689 nm and 739 nm respectively. In the process of co-incubation with ONOO−, generate a new substance with two internal conjugated structures through a special reaction mechanism, one giving the fluorescence with the excitation wavelength of 347 nm and the emission wavelength of 484 nm with the detection limit of 0.12 μM, and the other that with the excitation wavelength of 433 nm and the emission wavelength of 583 nm with the detection limit of 0.077 μM. The linear dynamic range of the probe is 0–5 μM. Its response is not affected by the other reactive oxygen species, thus can sensitively detect ONOO−. In bioimaging experiments with HepG2 cells, the green and blue cell fluorescence signals (583 nm and 433 nm, respectively) were increased, while the red one (739 nm) was significantly reduced, under lipopolysaccharide (LPS) induced oxidative stress, proving that the probe could sensitively detect ONOO− in living cells. This work provides a new tool for the dynamic changes of ONOO− and oxidative stress processes in biological systems. [Display omitted] • A new fluorescent probe, GXY-ADP-2, was developed for detection of ONOO−. • GXY-ADP-2 exhibited high specificity and sensitivity to ONOO−. • GXY-ADP-2 is a ratiometric fluorescent probe with three-channel fluorescence signal changed. • GXY-ADP-2 can detect the dynamic change of ONOO− in living cells. [ABSTRACT FROM AUTHOR]

A dual-site fluorescent probe based on naphthalimide and rhodamine was synthesized, which could rapidly and sensitively respond to H 2 S and Cu2+ with different fluorescence signals. [Display omitted] • The dual-responsive fluorescent probe (DTR-1) for detection of H 2 S and Cu2+ was developed. • DTR-1 could detect H 2 S and Cu2+ within 1 min. • The LOD for H 2 S and Cu2+ were calculated to be 0.035 μM and 0.16 μM, respectively. • DTR-1 was successfully applied to detect intracellular H 2 S and Cu2+. A highly selective and sensitive fluorescence probe (DTR-1) for simultaneously detecting H 2 S and Cu2+ with different fluorescence signals was synthesized. DTR-1 displayed remarkable fluorescence enhancement (560 nm, 34-fold) when H 2 S was added under excitation of 410 nm with the solution's color change from dark to green. The limit of detection (LOD) for H 2 S was calculated to be 0.035 µM. By contrast, the addition of Cu2+ enhanced obviously the emission intensity of DTR-1 with the maximal peak at 630 nm and color change from colorless to orange. LOD for Cu2+ was determined to be 0.16 µM. The sensing mechanism for H 2 S and Cu2+ in DMF/PBS (9/1, v/v, pH = 7.4) was studied by 1H NMR and ESI-MS. Furthermore, the potential application of DTR-1 in biological systems had been demonstrated through imaging of living cells. [ABSTRACT FROM AUTHOR]

Novel ratiometric fluorescent probe for real-time detection of alkaline phosphatase and its application in living cells. [Display omitted] • A novel ratiometric probe was constructed to detect alkaline phosphatase. • The introduction of spontaneously degradable linker is conducive to the construction of ratio fluorescent probes. • The detection limit is as low as 0.16 U/L with high selectivity and accuracy; • This probe possessing excellent biocompatibility. A novel ratiometric fluorescent probe has been developed through a simple synthetic route for the detection of alkaline phosphatase(ALP) in aqueous media and for fluorescence imaging in living cells. The introduction of a spontaneous-degradation spacer in the design of the fluorescent probe is beneficial for the ratio detection method and allows the selection of a fluorophore with an amino group. Under catalysis by ALP, the phosphate monoester bond breaks; this is followed by 1,4-elimination, decomposition of the carbamate moiety, and subsequent formation of the 4-amine-1,8-naphthalimide fluorophore. The probe APN shows a significant fluorescence colour change from blue to green in response to ALP, and the fluorescence intensity ratio of the probe solution (F 550 / F 480) has a good linear relationship with the ALP concentration in the range of 0 to 100 U L-1. Our studies have demonstrated that APN exhibits high accuracy in recognising ALP, with a detection limit as low as 0.16 U L-1. Furthermore, the probe shows very good biocompatibility, which is beneficial for its application in biological systems. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe tetrastyrene derivative (L) with aggregation induced emission (AIE) and high quantum yields prosperities is synthesized by a simple method. The optical properties of probe L to Al3+ are investigated using fluorescence emission spectral analysis and a low detection limit of 1.587 × 10−7 M for Al3+ in MeOH/H 2 O (v/v = 9/1, Tris = 20 mM, pH = 7.40) is obtained. The combination ratio of L to Al3+ (1:1) is determined by ESI-MS and Job's plot. Meanwhile, probe L has a good response to Al3+ in a wide pH range of 2–12. More importantly, the probe L shows very low cytotoxicity and strong fluorescence emission in living cells. This indicates that the probe L has potential application prospects in the detection of Al3+ in environmental and biological systems. A novel fluorescent probe with aggregation induced emission is synthesized, which exhibits good response to Al3+ in a wide pH range of 2–12 and very low cytotoxicity as well as strong fluorescence emission in living cells. Image 1 • Probe L has obvious AIE phenomenon. • The detection limits of probe L are 1.65 × 10−7 M for Al3+. • Probe L has good cell permeability and could be used as an efficient sensor for mapping Al3+ in living cells. [ABSTRACT FROM AUTHOR]

• Naphthalimide-based a lysosome-targeting fluorescent probe LyNP-H 2 S for H 2 S sensing. • LyNP-H 2 S displays a significant 262-fold fluorescence intensity enhancement in the presence of H 2 S at 540 nm. • Moreover, LyNP-H 2 S can rapid image H 2 S in lysosome and inflamed tissues. Since the fluctuation of cellular hydrogen sulfide (H 2 S) is a very important third endogenously generated gaseous signaling molecule and plays a key role in the development of numerous human disorders, the real-time fluorescence detection of H 2 S in living systems has attracted plenty of interest during past decade. Although a lot of H 2 S fluorescent probes have been reported, the relationship between the physiology and pathology of H 2 S in organelles remains unclear, especially for inflammatory tissue. In this work, by adopting a weakly basic morpholine group as the lysosome-targeting site, a naphthalimide derivative as the signal reporter group and a 4-dinitrobenzene-ether (DNB) as fluorescence signal quencher and H 2 S-selective recognition moiety, we reported a new lysosome-targeting TP fluorescent probe LyNP-H 2 S for H 2 S detection and imaging in living cells and inflamed tissues. The probe LyNP-H 2 S exhibits very low fluorescence signal in the absence of H 2 S, and displays a significant 262-fold fluorescence intensity enhancement in the presence of H 2 S at 540 nm. Moreover, LyNP-H 2 S has the capability of quantitative detection of H 2 S at concentrations ranging from 0 to 12.0 μM (limit of detection = 9.8 nM), rapid response, as well as high sensitivity and selectivity toward H 2 S. Impressively, the results of living cell and inflamed tissues imaging test demonstrate that LyNP-H 2 S has the potentiality of being an ideal probe for real-time H 2 S detection in biosystems. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe DCM-O 3 with NIR fluorophore was developed for ozone detection. • The probe DCM-O 3 exhibited high selectivity and sensitivity for ozone with the calculated detection limit of 6.2 × 10−7 M. • The probe DCM-O 3 was successfully employed to monitor ozone in the living A549 cells with low cytotoxicity. Nowadays, ozone has been widely applied in industry and medical therapies. However, excessive exposure to ozone can lead to lung dysfunction and many respiratory symptoms. As a member of reactive oxygen species (ROS), ozone was also involved in various physiology and pathology process. Given the fact of this, the effective detection of ozone in the atmosphere and biological system is of vital significance. Herein, we reported a novel dicyanomethylene-4H-pyran (DCM)-based fluorescent probe DCM-O 3 with butenyl being the recognition moiety for monitoring ozone. The probe displayed high selectivity towards ozone, and its response towards ozone could be completed within 5 min under the optimal condition. Besides, a good linear correlation was obtained between the ozone concentrations (0–50 μM) and the corresponding fluorescent intensity at 560 nm, and the limit of detection (LOD) was calculated to be 6.2 × 10−7 M. Moreover, the probe DCM-O 3 showed low cytotoxicity and was successfully applied to detect ozone in live cells. Given all the merits, the probe DCM-O 3 could function as a robust tool for researchers to investigate ozone-related diseases in the complex biological environment. [ABSTRACT FROM AUTHOR]

• BHMBH with benzothiazole fluorophore was synthesized and characterized. • BHMBH exhibits highly sensitivity fluorescence enhancement to Al3+ along with color change. • Limit of detection (LOD) for Al3+ was reached the level of 10−7 M. • BHMBH was successfully applied in the detection of Al3+ on test paper and imaging in HSC. An easy prepared benzothiazole-based probe (E)-5-(benzo[d]thiazol-2-yl)-2-hydroxy-3- methoxybenzaldehyde benzoyl hydrazone (BHMBH) was designed and synthesized, which displayed a significant fluorescence enhancement (over 500-fold) and obvious color changes in the recognition of Al3+. The binding ratio of probe BHMBH to Al3+ was determined as 1:1 according to Job's plot. The binding mechanism was fully clarified by the experiments such as FT-IR spectrum, ESI-MS analysis, and 1H NMR titration. The limit of detection (LOD) for Al3+ was determined as low as 0.232 μM based on the fluorescence titration of BHMBH. Moreover, the results of real sample experiments including real water sample, test papers, and cell image were all well demonstrated that BHMBH was capable of sensing Al3+ in environmental and biological system as well. [ABSTRACT FROM AUTHOR]

• A novel peptide-based fluorescent chemosensor L was synthesized. • L exhibited a highly selective to Zn2+ and Cu2+ through differential response. • L had excellent sensitivity with detection limits of 13.2 nM for Zn2+ and 4.1 nM for Cu2+ ions. • L was low toxicity and could be used to monitor Zn2+ and Cu2+ in living cells. A novel fluorescent chemosensor with dansyl-appended tetrapeptide (identified as L), was designed and synthesized using solid phase synthesis (SPPS) technology. At room temperature, L displayed high water solubility and highly selective fluorescence "turn-on" response towards Zn2+ detection in 100% aqueous solutions. Conversely, L exhibited highly selective detection of Cu2+ through fluorescence quenching by a mechanism intrinsic to the paramagnetic species. The binding stoichiometry with L and Zn2+/Cu2+ ions were determined from the Job's plot to be 2:1, and further verified with fluorescence titration, ESI-HRMS and DFT-Calculations studies. The lowest measured detection limits for L were 13.2 nM for Zn2+ and 4.1 nM for Cu2+, respectively, with excellent sensitivity. In addition to that, L was successfully analyzed quantitatively for Zn2+ and Cu2+ ions using logic gate construction. Furthermore, L exhibited excellent cell permeation and low biotoxicity during bioimaging studies, L was able to selectively identify Zn2+ and Cu2+ ions in living LNcap cells, suggesting that the chemosensor L will be a promising biomolecular chemosensor for multifunctional detection of Zn2+ and Cu2+ through differential responses in environmental and biological systems. [ABSTRACT FROM AUTHOR]

• It is the first QM-based AIE fluorescent probe for ONOO−. • QM-ONOO− showed bigger Stokes shift (190 nm) than the reported. • QM-ONOO− possessed rapid response, and low detection limit (27.5 nM). • The exogenous and endogenous ONOO− imaging in MCF-7 cells demonstrated its value of practical tool. Peroxynitrite (ONOO−), as one type of reactive nitrogen species (RNS) , is closely related to multiple pathophysiological processes. Visualization of ONOO− in living system is essential for further study of its physiological functions. However, most existing ONOO− fluorescent probes continuously display the aggregation-caused quenching (ACQ). In present research, a new activatable AIEgen fluorescent probe QM-ONOO− for ONOO− recognition and imaging was proposed. Activation of the probe by ONOO−, induced aggregation of QM−OH. This sensor showed fast response time (<4 min) and high sensitivity (DL, 27.5 nM), large Stock's shift (190 nm), long emission wavelength. Furthermore, the outcomes indicate that QM-ONOO− as an activatable AIEgen fluorescent sensor was robust chemical tool to detect endogenous peroxynitrite in living biological system. [ABSTRACT FROM AUTHOR]

Hypochlorous acid has played several functions in the biological system. However, excess HOCl can cause damage to biomolecules and result in some diseases. Accordingly, a new fluorescent probe, BSP , has been developed for fast recognition of HOCl through the HOCl-induced oxidation of methyl phenyl sulfide to sulfoxide. The reaction of BSP with HOCl caused a 22-fold fluorescence enhancement (quantum yield increase from 0.006 to 0.133). The detection limit of HOCl is found to be 30 nM (S/N = 3). The fluorescence enhancement is due to the suppression of the photo-induced electron transfer from the methyl phenyl sulfide moiety to BODIPY. Eventually, the cellular fluorescence imaging experiment showed that BSP could be effectively used for monitoring HOCl in living cells. Unlabelled Image • A fluorescent probe BSP has been developed for highly selective detection of HOCl. • The probe BSP can be applied in detecting exogenous and endogenous HOCl in living cells. • The probe BSP can quantitatively detect HOCl with a low detection limit 30 nM. [ABSTRACT FROM AUTHOR]

• A new thiophene-based dual functional sensor TSA was designed and synthesized. • Sensor TSA exhibits colorimtric response for Cu2+ and fluorimetric response for Al3+. • Sensor TSA shows low detection limit of 0.217 μM for Cu2+ and 49 nM for Al3+. • Sensor TSA was used for detection of Al3+ and Cu2+ in water, food samples and test strips. • Sensor TSA was applied to image intracellular Al3+ in live HeLa cells. A new thiophene-based colorimtric and fluorimetric dual functional sensor TSA was synthesized, which can highly sense Al3+ and Cu2+ ions in aqueous solution through two approaches: a significant fluorescence enhancement caused by Al3+ and a visible color change from colorless to yellow induced by Cu2+. The sensor TSA showed a highly binding affinity only toward Al3+ and Cu2+ even in the presence of other competitive metal ions with low detection limits of 49 nM and 0.217 μM, respectively. The mechanisms of TSA for sensing Al3+ and Cu2+ were based on the metal ions coordination of TSA , which have been demonstrated by HR ESI-MS and 1H NMR titration. In addition, sensor TSA was successfully applied to quantify Al3+ and Cu2+ in environmental water and food samples with good precision and accuracy. Moreover, the TSA -based test stips/silica can conveniently and practically detect and discriminate Al3+ and Cu2+ in water. Furthermore, sensor TSA has also been applied to detect Al3+ in live HeLa cells. This work provides a new approach with easily synthetic route and economically cheap for ultrasensitive, selective, quantitative and differentiable detection of Al3+ and Cu2+ in environmental, food and biological systems. [ABSTRACT FROM AUTHOR]

A new oligothiophene-based sensor 3 TH for monitoring Hg2+ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The 3 TH shows the significant specificity toward Hg2+ through "naked-eye" colorimetric detection as well as via ratiometric fluorescence enhancement response with low detection limit of 62 nM. In addition, sensor 3 TH shows high selectivity and sensitivity for Hg2+ with fast response in a suitable pH range. Moreover, the 3 TH -based test strips was used to conveniently detect Hg2+ ions in water. Furthermore, considering its good "turn-on" fluorescent sensing behavior and low cell cytotoxicity, 3 TH was successfully applied to detect and image Hg2+ in real water samples and living cells, which shows great potentials for application in environmental and biological systems. Image 1 • A novel naked-eye colorimetric and turn-on ratiometric fluorescent sensor 3 TH for Hg2+ was developed. • 3 TH towards Hg2+ features good selectivity, high sensitivity, fast response in a wide pH range. • 3 TH shows low cytotoxicity and excellent "turn-on" fluorescent sensing properties. • 3 TH was used to detect and image Hg2+ in water, test strips and living cells. [ABSTRACT FROM AUTHOR]

Developing specific and sensitive method for endogenous peroxynitrite (ONOO−) in living systems is valuable to understand its various pathological events. In this work, a simple and novel fluorescent probe (HPP) based on aggregation induced emission (AIE) as well as excited state intramolecular proton transfer (ESIPT) processes for endogenous ONOO− detection was constructed containing a diphenylphosphinate as the reactive site and a salicylaldehyde azine as the fluorophore. The probe showed specific fluorescence turn-on response toward ONOO− owing to the diphenylphosphinate group of HPP reacted with ONOO−, releasing the salicylaldehyde azine with both AIE and ESIPT characteristics. In addition, the probe exhibited a large Stokes shift, an excellent light-up ratio, high selectivity and excellent sensitivity with a low detection limit of 8 × 10−8 M for endogenous ONOO−. Moreover, the probe could be applied to bioimaging of endogenous ONOO− in live cell, which demonstrated the probe can be used as effective tool for investigation of ONOO− in biological systems. Unlabelled Image • A novel and simple AIE-ESIPT fluorescent probe was designed and synthesized. • The probe exhibited a large Stokes shift, excellent selectivity and sensitivity for ONOO−. • The probe could be applied to bioimaging of endogenous ONOO− in live cell. [ABSTRACT FROM AUTHOR]