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[Display omitted] • The high sensitivity of the probe with a detection limit of 58 nM. • Successful detection of endogenous and exogenous CO in living cells. • Capable of detecting CO in zebrafish. • NIR probe with a high signal-to-noise ratio for imaging CO in biological samples. Carbon monoxide (CO) is a highly emitted atmospheric pollutant that can pose a serious health risk when its concentration is too high. However, endogenous CO plays an important role in maintaining human health. The development of tools capable of detecting CO in environmental samples and biological samples is therefore essential. Although CO fluorescent probes have been reported, their further applications are limited by factors such as low sensitivity and emission wavelength. Here, we have constructed a CO probe with simple structure, high sensitivity, good selectivity and near-infrared (NIR) emission characteristics. The probe uses the dicyanoisophorone derivative as fluorophore and connects allyl moiety as the reaction site. After the response, the intramolecular charge transfer (ICT) process turns on and releases strong near-infrared fluorescence at 675 nm. The linear range of fluorescence intensity of the probe for CO concentration is 1–10 μM and the detection limit is as low as 58 nM. The high sensitivity and NIR emission give the probe excellent imaging of cellular exogenous and endogenous CO. Moreover, the probe can also be used to image CO in zebrafish. There is reason to believe that the probe can be a powerful tool for detecting CO concentrations in environmental samples and for analyzing the biological role of CO in organisms. [ABSTRACT FROM AUTHOR]

To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferroptosis is a non-apoptotic form of cell death characterized by iron-dependent lipid peroxidation and glutathione (GSH) depletion. Despite recent advances, challenges remain in understanding the bidirectional interactions or interplay between organelles during ferroptosis. In this study, we aimed to understand the interplay between mitochondria (Mito) and lysosomes (Lyso) in cell homeostasis and ferroptosis. For this purpose, we designed a single fluorescent probe that marks GSH in Mito and hypochlorous acid (HOCl) in Lyso with two distinct emissions. Using this dual-targeted single fluorescent probe (9-morphorino pyronine), we detected Mito-Lyso interplay in ferroptosis. We disclosed differences in Mito-Lyso interplay depending on the induction of ferroptosis. Although erastin treatment decreased GSH, RSL3 triggered a HOCl burst, and FIN56- and FINO2-induced ferroptosis increased GSH and HOCl. Additionally, we showed that only extracellular vesicles generated during erastin-induced ferroptosis could spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [Display omitted] • Simultaneous tracking of the GSH level in mitochondria (Mito) and the HOCl level in lysosomes (Lyso), respectively • Detected distinct Mito-Lyso interplay dynamics and GSH-HOCl crosstalk in ferroptosis • Diverse extracellular vesicle (EV) dynamics in different ferroptosis pathways • Spontaneous movement and docking of the EV accelerate neighboring cell death Wang et al. show the different dynamics of mitochondria-lysosome interplay in the four ferroptosis pathways. They identify diverse extracellular vesicles (EVs) in ferroptosis, of which only erastin-induced EVs can spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near-infrared fluorescence probe based on dicyanomethylene-4H-pyrans was designed and synthesized. • The probe exhibited high sensitivity and selectivity to Hg2+ in ultrafast response time. • The probe can visualize Hg2+ in living HepG2 cells. Mercury ions (Hg2+) are a class of heavy metal ions that can cause serious harm to the human body due to their toxicity, fluidity, and bioaccumulation. Direct contact with Hg2+ can cause adverse effects on the human body. In addition, long-term exposure to Hg2+ can lead to extreme toxicity of enzymes and proteins in the body, disrupting the cell cycle and thus endangering human life. It is becoming increasingly important to develop a method that is reliable, stable, and sensitive for detecting Hg2+. In this study, a near-infrared "turn-on" fluorescent probe based on dicyanomethylene-4 H -pyran, DCM-Hg, was designed and synthesized to determine Hg2+ over other metal ions. Probe DCM-Hg had a detection limit (LOD) of 3.35 μM when used to detect Hg2+. The Hg2+ concentrations and the fluorescence intensities at 695 nm showed a good linear correlation. Additionally, Hg2+ in HepG2 cells was successfully visualized using the current probe. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new benzobodipy based fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity with a fast response to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Hypochlorous acid (HOCl) is a significant reactive oxygen species within biological systems, and its anomalous metabolism has been linked to a range of diseases. Therefore, it is crucial to track and monitor the concentration of HOCl in living organisms to understand its biological functions and study its pathogenic mechanisms. In this study, we developed a photoinduced electron transfer (PeT) mechanism-based benzo-fused bodipy fluorescence probe, named BBy-Se , for highly sensitive and selective detection of HOCl in aqueous solutions. BBy-Se demonstrated a good turn-on fluorescence response to HOCl by specifically oxidizing the selenium atom. It exhibited significant Stokes shift (82 nm), low detection limit (10.9 nM) and rapid response (less than 10 s). Furthermore, the probe was successfully employed for real-time fluorescence imaging of HOCl in living HeLa cells and zebrafish, as demonstrated by the bioimaging results. The development of BBy-Se presents a new approach to explore the biological roles of HOCl and offers a valuable tool for studying its function in diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe based on 1,3,5-Triazine was designed and synthesized to detect Hg(Ⅱ). • The novel fluorescent probe exhibited high selectivity, good stability, large Stokes shift (100 nm). • The novel fluorescent probe has been successfully used for cell and zebrafish imaging. • The novel fluorescent probe has successfully detected Hg(II) in tobacco. Non-biodegradable, bioaccumulative, and highly toxic, mercury(II) poses a significant threat to both ecosystems and human health. Extensive data indicates that even extremely low levels of Hg(II) can cause significant harm to human health. In this paper, the thiocarbonate specific recognition site was used for the detection of Hg(II), which was successfully synthesized by the hydroxyl group of 1,3,5-Triazine with phenyl chlorothiocarbonate. The probe exhibited advantages of high sensitivity (0.253 μM), good selectivity, large Stokes shift (100 nm), and good biocompatibility. The probe TzAr-Nap-Hg successfully fluorescently imaged Hg(II) in cells, zebrafish and tobacco, making it possible to detect the content of Hg(II) in agricultural and sideline products. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric and ratiometric fluorescent probe TPA-Y with AIE characteristic has been developed; • TPA-Y exhibits a large emission peak separation up to 185 nm and gives low LOD (47.1 nM) for bisulfite; • Quantitative detection of bisulfite in food samples (sugar and red wine) was achieved; • TPA-Y can reversible response to HSO 3 -/H 2 O 2 cycles and cell imaging. Reversible detection of bisulfite (HSO 3 -) and hydrogen peroxide (H 2 O 2) is highly desirable in biology and food safety owing to their redox pair function in biological systems and their utilization in food industry. In this work, a ratiometric fluorescent probe (TPA-Y) with aggregation-induced emission (AIE) properties based on triphenylamine fluorophore was designed and synthesized for reversibly monitoring of HSO 3 -/H 2 O 2. Reaction of HSO 3 - with TPA-Y can result in ratiometric fluorescence changes (I 444 / I 629), and the emission spectrum blue shift reaches 185 nm, which can effectively avoid spectral overlap. Meanwhile, the solution color changed obviously from orange to colorless, enabling naked eye detection of HSO 3 -. TPA-Y was capable of quantitatively detect HSO 3 - in sugar and wine samples with the recovery rates ranging from 94.52 to 102.18%. In addition, TPA-Y is suitable to prepare paper strips and anti-counterfeiting ink for HSO 3 - detection. In addition, the original TPA-Y can be released after the addition product (TPA-Y-HSO 3 -) is oxidized by H 2 O 2 , and the HSO 3 -/H 2 O 2 redox cycle can repeat for at least six times. The probe TPA-Y can be applied to fluorescence imaging of reversible and dynamic interconversion between HSO 3 - and H 2 O 2 in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new H 2 S fluorescence probe with the thiolysis of dinitrophenyl ether is developed. • The probe can detect H 2 S with high selectivity and low LOD in aqueous solution. • The probe was successfully applied to detec H 2 S in test paper strips and food samples. • The probe was successfully used for imaging exogenous H 2 S in living cells. Small-molecular fluorescent probes are currently being developed for sensing of hydrogen sulfide and are attracted great attention because of the significant roles of H 2 S in food safety and living organisms. We report herein an efficient approach to modify the previous reported quinolinium-phenol vinylic conjugated fluorescent probes 4NS by combination of the accelerated nucleophilic addition of H 2 S to an aldehyde group followed by an intramolecular fast thiolysis of dinitrophenyl ether. The modified probe 4ANS can be able to efficient sense H 2 S and displays typical features, with good selectivity, high sensitivity (LOD = 15 nM), "naked-eye" colorimetric and turn-on fluorescent detection, rapid response time (<3 mins), and good biocompatibility. The mechanism involving thiolysis of dinitrophenyl ether was confirmed by HRMS analysis, and the practical application to detect H 2 S in food spoilage and cell imaging was successfully demonstrated. [ABSTRACT FROM AUTHOR]

An off-on fluorescent probe (NS-CDs-AgNPs) was synthesized based on a one-pot microwave process by utilizing N, S co-doping carbon dots (NS-CDs) and silver nitrate as precursors. The significant peak of NS-CDs-AgNPs at 393 nm in ultraviolet spectrum indicated silver nanoparticle (AgNPs) were successfully synthesized. A faint blue fluorescence emission (442 nm) was displayed when excited NS-CDs-AgNPs at 371 nm. A remarkable fluorescence recovery was observed upon adding of trance Hg2+, whereas the other heavy metal ions did not elicit this response. The reason for this phenomenon was revealed in this work that a spontaneous redox reaction occurred between NS-CDs-AgNPs and Hg2+, which leaded to the formation of NS-CDs-Ag n -2NPsHg complexes. On the basis of this mechanism, a new off-on fluorescent analytical method was constructed for Hg2+ detection with linear range of 10–400 nM (R 2 = 0.9941), and the detection limit (LOD) of 5.16 nM. Additionally, satisfactory recovery (90.28%–106.13%) and the relative standard deviation (RSD) (RSD＜5.21%) were obtained in water sample detection. More importantly, the NS-CDs-AgNPs exhibited lower cytotoxicity and better biocompatibility, indicating a huge potential in cell imaging and clinical medicine. [Display omitted] • An off-on fluorescent probe NS-CDs-AgNPs was constructed on the basis of the in-situ formation of silver nanoparticles (AgNPs) through one-step microwave-assisted method. • The spontaneous redox reaction of NS-CDs-AgNPs with Hg2+ was confirmed as the main recognition mechanism. • The NS-CDs-AgNPs is not only highly selective for Hg2+ with a LOD of 5.16 nM (S/N = 3), but also have a lower cytotoxicity and satisfactory biocompatibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • An interesting self-fluorescent colloidal material. • Found enhanced fluorescence quenching, selectivity, scavenging and chelating capabilities for Hg2+ ions in aqueous solution. • Reversible and labile chelation behavior of Hg2+ established using EDTA and Na 2 S • Fluorescence behavior for cell imaging in live HADF. In this research work, an interesting sugar based fluorescent materials has been successfully developed to detect metal ions (Hg2+) in aqueous solution. The prepared colloid, 3-(benzimidazole-2-yl)-2-hydroxy benzaldehyde/chitosan (ChI) has significant characteristics as greener and eco-friendly material. ChI has found for switching of proton transfer between enol-imine and keto-enamine forms of ChI through excited-state intramolecular proton transfer (ESIPT) mechanism. The internal chemical-bonding and functionality of ChI are confirmed through FTIR, UV–Vis, fluorescence, SEM, TEM, DLS etc. ChI shows its fluorescence-quenching, selectivity, scavenging and chelating capabilities for Hg2+ ions in the presence of other cations in aqueous solution. Spectral and XRD analysis have established the remarkable continual and consistent detection of Hg2+ in aqueous system with a limit of detection of 0.204 nM. The strong chelating agent EDTA is used to regain of fluorescence of ChI in support of labile chelation ability of ChI and to show reversibility for continual detection of Hg2+ due to the strong EDTA/Hg2+ complexation. Scavenging ability is investigated using Na 2 S solution followed by the XRD analysis of precipitate appeared. Also, ChI shows its efficiency for the fluorescence cell imaging in live HADF cells with negligible cytotoxicity. Convincingly, ChI has processed as materials with very significant addition and advancement for its multimodal and eco-friendly behavior in current material development research. [ABSTRACT FROM AUTHOR]

• Two polarity-sensitive fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) with D-A-D structures were accurately synthesized by a simple synthetic method. • The two fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) exhibit good photophysical properties, such as bright fluorescence, large Stokes shift, and resistance to chemical interference. • Both fluorescent probes (Nap-LD-Ⅰ , Nap-LD-Ⅱ) easily penetrate the cell membrane, specifically localize and aggregate in lipid droplets and lysosomes with low cytotoxicity, and yellow and red fluorescent lipid droplets and lysosomes can be observed. • Both fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) were further investigated for the separate targeting of lysosomes and lipid droplets in HepG2 cells. • Both fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) can be used for imaging of zebrafish. Lipid droplets (LDs) and lysosomes, vital subcellular organelles in cells, played irreplaceable roles in the areas involved in the synthesis of cell membranes, the movement of substances and the transfer of energy. Moreover, the imbalance of LDs could cause the occurrence of certain diseases, such as cardiovascular disease, liver cancer, atherosclerosis and diabetes. LDs and lysosomes interact in some biological processes. In this work, two polarity-sensitive fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) were developed and synthesized by simple 1,8-naphthalimide scaffold modifications, which exhibited large Stokes shifts (173 nm and 190 nm), viscosity, pH stability and interference resistance. Notably, they were biocompatible and showed good targeting for bioimaging. LDs, lysosomes in HepG2 cells and zebrafish could be marked by bright yellow and red fluorescence after incubation with probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ). In addition, HepG2 cells were stained for NNap-LD-Ⅰ and NNap-LD-Ⅱ to monitor the corresponding reduction in the number of LDs in starvation-treated cells. Similarly, the targeting of the probes to the lysosomes was diminished during imaging after the cells were treated with chloroquine (CQ), resulting in a reduction in lamellar fluorescence. These remarkable characteristics suggested that the probes NNap-LD-Ⅰ and NNap-LD-Ⅱ were quite efficient fluorescent probes with good visualization of LDs and lysosomes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new dual-functional probe L was synthesized via solid phase peptide synthesis (SPPS) technology. • L has strong specificity to Cu2+ based fluorescent and colorimetric methods, the LOD was 7.1 nM. • The in situ generated L -Cu2+ ensemble was used for detection of l -His with a low detection limit (15.3 nM). • L was successfully used to sequential detection of Cu2+ and l -His in living cells based on low cytotoxicity. • Test strips and smartphone were designed for quick and easy visual inspection of Cu2+ and l -His with " naked eye". A new fluorometric and colorimetric dual-modalitye probe L for detection of Cu2+ and l -His was constructed based on peptide skeleton via solid phase peptide synthesis (SPPS) technology. L exhibited highly selective recognition towards Cu2+ through formation of L -Cu2+ ensemble with a 2:1 binding stoichiometry, and the limit of detection (LOD) for Cu2+ was determined to be 7.1 nM. Correspondingly, L -Cu2+ ensemble was investigated by fluorescence technique which clearly established the high selectivity towards l -His based on fluorescence "off–on" response, and the limit of detection (LOD) for l -His was calculated to be approximately 15.3 nM. The selective sensing of Cu2+ was efficiently reversible with l -His, which was no loss of fluorescence intensity in 10 cycles. Notably, the sensing behavior of L towards Cu2+ and l -His detections was shown to be available within the wider pH interval (7.0–12.0). Cells imaging studies have shown that L was easily applied to the continuous imaging of Cu2+ and l -His in living cells. Furthermore, the test strips were also prepared for rapid and sensitive identification of Cu2+ and l -His. Combining smartphones and color changes, the semi-quantitative relationship between the R/B and the concentration of Cu2+ was established, and the limit of detection (LOD) reached up to 0.29 µM. [ABSTRACT FROM AUTHOR]

Highlights • Fluorometric and colorimetric modes were realized. • AIE and ICT effects controlled the detection process. • Real-time imaging were achieved in live cells and zebrafish. Abstract Since hypochlorite (ClO−) possesses the ability that oxidizes electron-rich objects with accompanying variations in spectroscopic features, we present here an effective strategy for generating new molecular-level probe that will be compatible for application in ClO− detection. This optical sensor has been established on a donor-π-acceptor (D-π-A) electronic structure derived from a pyrene derivative appended by 2-thioxo-dihydro-pyrimidine-4,6-dione (abbreviated as Py-Pd). Specifically, it can serve as a dual-mode sensor which exhibits fluorometric and colorimetric responses to the presence of hypochlorite. The high sensitivity, selectivity, fast response time (30 s) as well as low detection limit (75 nM) have been realized. Extensive spectroscopic analyses support the oxidation cleavage of bridge C C linkage leads to the transformation of Py-Pd to pyrene-2-carbaldehyde (Py-CHO). Such real-time imaging of hypochlorite has been also achieved in live cells and zebrafish model. In this sense, this molecular-based system can be employed as an indicator for early evaluation of optical responses of reactive oxygen species. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Benzoxazole appended based probe (BS) was designed and synthesized. • BS showed good selectivity towards Zn2+ion with 'turnon' fluorescence emission. • BS-Zn2+ ensemble showed selective sensing towards PPi− ion. • BS and BS-Zn2+ ensemble could detect Zn2+ & PPi ions in live cells. Abstract A novel benzoxazole appended dipodal Schiff base (BS) was synthesized and its sensing property was investigated. The receptor BS detected Zn2+ ions selectively by turn-on fluorescence among the wide range of metal ions in DMSO-H 2 O (1:9 v/v, 50 mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) at pH 7.4. The different physicochemical parameters of BS-Zn2+ complex were investigated by UV–vis, photoluminescence, 1H NMR titration and ESI-MS techniques. The limit of detection (LOD) and binding constant (K b) of BS-Zn2+ complex have been determined by fluorescence titrations and found to be 4.53 × 104 M−1 and 0.52 μM. Moreover, binding ratio of BS and Zn2+ was found to be 1:1 by Job's method. Further, the BS–Zn2+ complex was used to sense pyrophosphate (PPi) ions as a secondary sensor in HEPES buffer solution. Overall, the sensitive fluorescence behavior of the receptor BS has been utilized as a powerful tracker for zinc ion and pyrophosphate ion in biological systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel fluorescent probe (DFI) was designed and synthesized. • DFI showed good selectivity towards H 2 S with 'turn on' fluorescence emission. • The detection limit of DFI probe towards H 2 S was found to be 0.13 nM. • DFI probe was able to detect H 2 S in live cells. Abstract A simple turn-on fluorescence sensor (2,2′-(2-(2,4-dinitrophenoxy)-5-methyl-1,3-phenylene)bis(1,4,5-triphenyl-1H-imidazole) (DFI) was synthesized, characterized and its sensing properties were investigated through fluorescence spectral studies. The new fluorescence sensor DFI shows a selective sensing of hydrogen sulfide (H 2 S) via enhancement of fluorescence intensity and the detection limit was found to be 0.13 nM. Subsequently, the probe DFI has been applied to be an effective bio-tracker for monitoring hydrogen sulfide in real samples as well as living cells. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel fluorescent probe for biothiols detection. • Red fluorescence with emission maxima at 640 nm and a large Stokes shift of 160 nm. • High sensitivity and selectivity. • The sensing mechanism was studied by MS and HPLC. • Endogenous biothiols imaging in living MCF-7 cells. Abstract Small molecule biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in physiological and pathological processes, which are related to many diseases. Hence the detection of cellular biothiols is of great significance. Here we reported a new probe DNT that was constructed by a donor-acceptor type dye NT-OH and a recognition site DNBS group. DNBS group also acted as a fluorescence quencher in this molecule. While in the presence of biothiols, the DNBS group reacted with the sulfydryl group of thiols by nucleophilic aromatic substitution reaction and then eliminated from the probe, turning on the red fluorescence of the probe with emission maxima at 640 nm and a large Stokes shift of 160 nm. Solution experiments revealed that DNT showed high sensitivity and selectivity to biothiols. Besides, it was further utilized to map endogenous biothiols in MCF-7 cells successfully. [ABSTRACT FROM AUTHOR]

A hydroxyphenylquinazolinone-based fluorescent probe DAP-1 with a large Stokes shift (162 nm) was firstly developed for detection of cysteine. The probe DAP-1 with two acrylate as highly Cys-selective sites was designed based on the combination of excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) mechanism. Upon the treatment with cysteine, DAP-1 displayed a strong fluorescence enhancement (65-fold). The limit of detection obtained from fluorescent titration was as low as 0.03 μM. DAP-1 could detect cysteine with high selectivity and sensitivity. Significantly, DAP-1 could be used to detect cysteine in living cells. [ABSTRACT FROM AUTHOR]

A novel 4′-hydroxybiphenyl-4-carbonitrile-based fluorescent probe, 1 , for selective detection of cystein (Cys) over homocystein (Hcy) and glutathione (GSH) was developed. This probe had simple structure and could be easily synthesized with good yield from commercially available materials. Moreover, probe 1 showed a remarkable large Stokes shift (180 nm) and displayed a rapid (5 min) and highly sensitive response (the detection limit was 0.15 μM) for Cys with fluorescence turn-on signal changes (142-fold fluorescence enhancement). Importantly, probe 1 could be used to detect and image both exogenous and endogenous Cys in living A549 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • This is a rhodamine-based "off-on" fluorescent probe with a novel structure to detect tyrosinase activity. • The rhodamine fluorophore structure was improved by expanding the π-conjugation system, asymmetric synthesis, and fixing the N terminus, which greatly improved the fluorescence quantum yield of the fluorophore. • The use of 3-hydroxybenzyl oxygen as the recognition group of the probe effectively avoids the interference of reactive oxygen species in the detection of tyrosinase and improves the selectivity of the probe for tyrosinase. Tyrosinase (TYR) detection will be crucial in the prevention and early diagnosis of some illnesses, including epilepsy, albinism, and melanoma, due to the close linkage of abnormal expression of TYR with the occurrence of these diseases. Therefore, how to obtain a fluorescent probe that has a high fluorescence quantum yield and high specificity for detecting TYR activity will be of significance. In this work, we improved the rhodamine structure by expanding the π-conjugation system and using asymmetric synthesis to provide a fluorescent probe with good optical properties for the specific detection of TYR. The fluorescence quantum yield of fluorophore released from the probe by the enzymatic reaction with TYR was as high as 0.22, which was significantly greater than that of other previously reported fluorescent probes. We also chose 3-hydroxybenzyl oxygen as the recognition group, which can successfully lessen the interference from reactive oxygen species (ROS). At the same time, the probe demonstrated great sensitivity in detecting TYR activity, and the detection limit of TYR for the probe was calculated to be 0.45 U/mL. In addition, the probe has currently been successfully utilized to evaluate TYR activity in cells. Therefore, this probe is anticipated to be crucial in identifying TYR activity in challenging settings. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe DPY simultaneously responds to GSH/ONOO-with dual-emission. • DPY can co-target ER and Mito, tracking the GSH-ONOO- crosstalk in both organelles. • Fluorescent imaging in living cells discloses the ER-Mito contact change in ferroptosis. Ferroptosis is a recently proposed cell death mechanism characterized by iron-dependent lipid peroxidation. Reactive oxygen/nitrogen species (ROS/RNS) are responsible for lipid peroxidation in the endoplasmic reticulum (ER) and mitochondria (Mito) and result in glutathione (GSH) depletion in ferroptosis. Peroxynitrite (ONOO–) is a highly reactive RNS, and its equilibrium with GSH is vital to maintain redox homeostasis in ER and Mito. The GSH-ONOO– crosstalk is thus essential to understand the changes of ER and Mito in cells during ferroptosis. Further, the interplay between ER and Mito, the ER–Mito contact, is expected to change during ferroptosis, which has been observed in other cell death forms but not in ferroptosis. Here, we report a new fluorescent probe (DPY) with a dual response to GSH and ONOO– in both the ER and Mito. Fluorescence of DPY can be triggered by GSH and ONOO– at 608 (red) and 456 nm (blue) excited at 561 and 405 nm, respectively. The structure of DPY contains both the ER- and Mito-targeting units, and simultaneous anchoring of the probe is allowed in duple organelles. Application of the probe in cell imaging firstly reveals GSH/ONOO– crosstalk in ER and Mito in erastin- and RSL3-induced cells during ferroptosis. And a closer ER–Mito contact is also observed in hepatic cells during ferroptosis. Further studies on the blue-red merged images disclose the ER-Mito contact change in cells during ferroptosis through the observed difference in Pearson correlation coefficients. A similar trend is also verified in acetaminophen-induced ferroptosis. [ABSTRACT FROM AUTHOR]

A probe TR-NOOO- was employed for tracking ONOO– level during Erastin-induced ferroptosis. [Display omitted] • A novel fluorescent probe TR-ONOO- based on tetraphenylene derivatives and rhodamine analogs was constructed. • Probe TR-ONOO– showed high selectivity and rapid sensing for ONOO–. • The probe could image ONOO– in living cells during erastin-induced ferroptosis. The reactive nitrogen species peroxynitrite (ONOO–) involve physiological and pathological processes as a significant factor. Develop a probe for monitoring the ONOO– during ferroptosis is very significant. Here, we designed and synthesized a probe TR-ONOO– based on tetraphenylene derivatives and rhodamine analogs for detection of ONOO– with fluorescence-on. Considering the strong oxidative properties of ONOO–, the carbon–carbon double bonds of bridged tetraphenylene derivatives and rhodamine analogs in the TR-ONOO– molecule are oxidized, so that the designed probe can realize fluorescence turn-on. When adding the ONOO– to the probe TR-ONOO– solution, the fluorescence intensity has increased about 40 folds and the color changed from purple to light yellow, enabling naked-eye detection of ONOO–. Furthermore, the probe TR-ONOO– can recognize ONOO– with high selectivity and fast response time. Combining with fluorescence imaging, TR-ONOO– was successfully employed for tracking endogenous ONOO– real-time and the over expression of ONOO– was effectively visualized during erastin-induced ferroptosis. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe 1 has been developed for Cu 2+ by the incorporation of picolinate onto a tricyanofuran-based fluorophore. The probe was weakly fluorescent due to the masked phenolic group and the resulted inhibition of the push-pull character of the fluorophore. The chemoselective reaction of probe 1 with Cu 2+ leads to a dramatic fluorescence enhancement at 610 nm via the Cu 2+ -mediated hydrolysis of picolinate moiety and the subsequent release of the highly emissive fluorophore. This probe features high selectivity for Cu 2+ over other cations, as well as high sensitivity with a low detection limit of 54 nM. Moreover, cell cytotoxicity and imaging tests indicate that probe 1 is biocompatible and can be utilized for imaging Cu 2+ in live cells. [ABSTRACT FROM AUTHOR]

This work describes a hydrothermal method for the preparation of multi-functional carbon quantum dots of the type La-CQDs. The La-CQDs are 4.3 ± 0.3 nm in diameter and have a good dispersion and exhibit excellent emission property and high stability, as well as excitation-dependent emission behavior with typical excitation/emission peaks at 350/460 nm. They can also be used as an effective fluorescent probe for the quenchometric determination of mercury ion in aqueous solution with a detection limit of 0.1 µM. The particles are readily internalized by liver epithelial HepG2 cells and enable multi-color fluorescence imaging by displaying green and red emission if excited with 488 and 543 nm light, respectively. Intravenous injection of the quantum dots in nude mice, in turn, enabled tissue imaging. The La-CQDs possess abundant phosphate, hydroxyl, pyridinic, pyridine-like and pyrrole-like nitrogen groups. Therefore, they can exhibit strong fluorescence, improve the accuracy as an optical monitoring code both in vitro and in vivo , and enhance blood compatibility. In vitro investigations show that La-CQDs do not exhibit significant apoptotic effects on NIH3T3 cells even at a high concentration (2.5 mg/mL) while they exhibit improved antibactericidal capacity of the La-CQDs against gram-positive S. aureus and gram-negative E. coli bacteria was also observed. No apparent pathological damages are observed in all organs during the 30-day period, which suggests that La-CQDs do not produce detectable long-term toxicological responses. [ABSTRACT FROM AUTHOR]

An efficient, aminothiazole based, fluorescent probe ( E )-2-(2-aminothiazol-5-yl)- N '-((2-hydroxynaphthalen-1-yl)methylene)acetohydrazide (NTH) for the detection of Al 3+ ions was synthesized and characterized by different physico-chemical and spectroscopic tools. An attractive glowing blue color was observed in the presence of Al 3+ with single channel emissions for NTH (λ em 451 & λ ex 391 nm). NTH, selectively detected Al 3+ ions among various other ions without any significant interference in Tris-HCl buffer solution (10 mM, pH ∼ 7.4). The >C N isomerization was responsible for the turn ‘on’ fluorescence response after Al 3+ binding. The stoichiometry of NTH with Al 3+ was determined to be 1:1 by Job’s plot. The binding constant and limit of detection (LOD) were observed as 3.65 × 10 9 M −1 and 1.09 × 10 −9 M, respectively. The 1 H NMR titration and DFT studies were also performed in support of binding details of NTH-Al 3+ complex. MTT assay on live A549 cells suggested viability of the probe to A549 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicated that the accumulation of Al 3+ in the cytoplasm of cells could be detected by NTH. [ABSTRACT FROM AUTHOR]

Herein, we reported a novel probe with near-infrared fluorescent emission (750 nm) and a large Stokes shift (118 nm) for the detection of H 2 S. The probe can specific and sensitive detection (LOD as low as 4.5×10–8 M) of H 2 S, accompanying an ideal color changes from purple to green natural light, which could rapid detect HS– over other analytes through the "naked eye". The probe was successfully be utility for H 2 S image in cells and mice. [Display omitted] • The novel NIR probe was developed based on the nucleophilic substitution mechanism. • The probe can specific and sensitive detection of H 2 S, accompanying color changes from purple to green. • The probe can be used as a useful tool for studying the physiological and pathological phenomena related to hydrogen sulfide. As a kind of gas signal molecules, H 2 S is related to in human health and disease. Herein, we developed a novel probe with near-infrared fluorescent emission (750 nm) and a large Stokes shift (118 nm) for the detection of H 2 S. The probe can specific and sensitive detection (LOD as low as 4.5 × 10–8 M) of H 2 S, accompanying an ideal color changes from purple to green natural light. Based on the advantages of excellent cell permeability and cytotoxicity data, the probe was be utility for H 2 S image in cells and mice. [ABSTRACT FROM AUTHOR]

A novel indazole fused rhodamine fluorescent dye with large Stokes shift and stable fluorescence in water for constructing an Hg2+-selective probe and cell imaging applications. [Display omitted] • A indazole fused rhodamine dye InRh has been prepared with stable fluroescence in water. • Probe InRhH can respond to Hg2+ with high selectivity and sensitivity by fluorescence and absorption spectra. • Probe InRhH shows promising application in tracing Hg2+ in living cells. Developing selective and sensitive probes for mercury ion (Hg2+) is of great significance because Hg2+ exhibits high toxicity and poses a potential threat to public health and the environment. Herein, a newly designed indazole fused rhodamine dye InRh has been prepared, which shows stable fluorescent signals in water at a wide pH range of 1.0–10.0. Based on the dye InRh, a novel fluorescent probe InRhH for Hg2+ is further developed by modifying the spirolactone ring of InRh to form a closed spirolactam ring. The probe shows selective fluorescence "off–on" signal changes to Hg2+ with a visible color change and response time of 40 min in H 2 O/CH 3 CN (pH = 6.0, v/v = 4/1), and the detection limit for Hg2+ is measured to be 0.33 nM. The recognition mechanism for Hg2+ can be ascribed to the binding interactions between Hg2+ and probe in a 2: 1 coordination mode, which promotes the occurrence of spirolactam ring opening and further hydrolysis. In addition, the InRhH can be applied for test strip experiments and tracing 10−6 M level Hg2+ with visible color change. Furthermore, the suitable cytotoxicity allows the probe to apply for sensing Hg2+ in living HeLa cells by fluorescence imaging. [ABSTRACT FROM AUTHOR]

A new fluorescence "turn on" Hg2+ probe 3,3'-(((2-hydroxy-5-methyl-3-(4-oxo-3,4-dihydroquinazolin-2-yl)phenyl)methylene)bis(sulfanediyl))dipropionic acid (QBDA) based on Hg2+-triggered transformation of dithioacetal to aldehyde has been developed. Probe QBDA exhibits high selectivity and sensitivity to Hg2+ over other metal ions in PBS buffered (20 mM, pH = 7.4) solution, the detection limit of QBDA for Hg2+ was estimated to be 2.04 x 10-8 M and the potential interference from Ag+ can be suppressed in PBS buffered normal saline solution. Living cell imaging investigations show that QBDA possesses good cell permeability, and can act as a light-up imaging probe for Hg2+ ions in MCF-7 cell. [ABSTRACT FROM AUTHOR]

A fluorescent probe ( 1 ) for distinguishing amongst biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), is developed based on different cascade reactions. The key design feature of fluorescent probe 1 is the integration of two potential reaction groups for the thiol and amino groups of biothiols in one molecule. By reacting with the halogen atom and α, β-unsaturated malonitrile in probe 1 , Cys, Hcy and GSH can generate a total of three main products with distinct photophysical properties. Probe 1 shows a strong fluorescence turn-on response to Cys with blue–green emission by using an excitation wavelength of 390 nm. At an excitation wavelength of 500 nm, probe 1 responds to GSH over Cys and Hcy and emits strong orange fluorescence. The discrimination of biothiols can be demonstrated by cell imaging experiments, indicating that probe 1 can be a useful tool for the selective imaging of Cys and GSH in living cells. [ABSTRACT FROM AUTHOR]

Herein, we report a novel fluorescent probe based on coumarin to detect cysteine (Cys). The probe can react rapidly and selectively with Cys but not with the other amino acids. When the Cys was added to the solution of the probe, we could observe obvious color change from pale green to bright green. The detection limit of this probe for Cys was found to be 0.06 μM. Additionally, bioimaging of intracellular Cys by this probe was successfully applied in living cells, which indicating that this probe holds great potential for biological applications. [ABSTRACT FROM AUTHOR]

Liquid-ordered (Lo) and liquid-disordered (Ld) microdomains in plasma membrane play different yet essential roles in various bioactivities. However, discrimination of the two microdomains in living cells is difficult, due to the similarity in their constituents and structures. Up to now, polarity sensitive probes are the only tool for imaging the two microdomains, but their small difference between emission spectra in the two microdomains (less than 50 nm) limited their application in living cells. In this work, we first presented an aggregation/monomer type of fluorescent probe ( 2,7-9 E -BHVC12 ) with much larger separation in emission wavelength (up to 100 nm), for dual-color visualizing the two membrane microdomains in living cells. The probe can form red-emissive aggregates and yellow-emissive monomers when induced by Lo and Ld microdomains, respectively, and thus enables clear visualization of the two membrane microdomains in living cells with dual colors, and thus high-fidelity images of substructures of plasma membrane have been obtained. According to the images of three kinds of normal cells and three kinds of cancer cells stained with 2,7-9 E -BHVC12, significant difference in plasma membrane microstructure of cancer cells was found. In terms of 2,7-9 E -BHVC12 , normal cells were mainly consisted of either Lo or Ld microdomains all over their membranes, while cancer cells all clearly display coexistence of Lo and Ld membrane microdomains. Therefore, 2,7-9 E -BHVC12 can serve as a powerful tool for studies of membrane microdomains, and the different results of normal and cancer cells would also deepen our understanding in cancer science. [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]

An off-on fluorescent probe (CuCIN), coumarin-naphthol linked by an imine group, for detecting Cu 2+ in DMSO-HEPES buffer (1:99, v/v) solution was successfully developed. Mechanism studies suggested that CuCIN firstly formed a complex with Cu 2+ in a 1:2 metal-to-ligand ratio, and then 60-fold fluorescence enhancement was observed when Cu 2+ promoted the imine hydrolysis to release the fluorescence compound 7-diethylaminocoumarin-3-aldehyde. This probe displayed desired properties such as high selectivity toward other metal ions, low detection limit (12.7 nM) and low cytotoxicity. Bio-imaging study revealed that the new probe CuCIN could be applied for imaging living cells with good cell permeability. We hope to apply this probe in the biomedical research field for the imaging of disease-relevant Cu 2+ . [ABSTRACT FROM AUTHOR]

The 4−N,N-dimethyl-1,8-naphthalimide based fluorescent probes have been explored for selective detection of Au 3+ . Both probes show a pronounced fluorescence enhancement response to Au 3+ . Hydroxy is introduced as ligand of Au 3+ for Probe 1 and the newly designed Probe 2 contains an alkyne moiety to recognize Au 3+ through an irreversible C≡C bond hydrolysis reaction. Probe 1 exhibits higher performance such as faster response, lower detection limit of 0.050 μM and the better responsive effect in 99.5% water system compared with most of probes published. The Probe 2 displays high stability to pH, suitable water solubility, wider linear range (0–100 μM) to Au 3+ , and live-cells imaging with low cytotoxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-site fluorescent probe (MTRN) for HClO and H 2 S was constructed by combining naphthalimide fluorophore with rhodamine fluorophore. • The detection limits (LOD) for HClO and H 2 S were calculated to be 3.39 nM and 0.13 μM, respectively. • MTRN was successfully exploited for detecting HClO and H 2 S in cell imaging and test strip. HClO and H 2 S commonly coexist in organisms and act synergistically to maintain the redox dynamic balance in vivo; however, it is difficult to trace precisely and simultaneously HClO and H 2 S by single recognition-type fluorescent probes. In this paper, a novel probe (MTRN) was designed for detecting specifically HClO and H 2 S with dual-emission property by using an acrylate and a phenyl isothiocyanate as recognition sites. MTRN possessed outstanding performances including ultrasensitivity (LOD = 3.39 nM), high specificity and short response time (<2 min) for HClO under excitation of 530 nm with the fluorescence's color change from dark to red. Moreover, upon treating with H 2 S, the fluorescence peak centered at 488 nm of MTRN enhanced obviously within 1 min and color changed from colorless to blue, the LOD was found to be 0.13 µM. The possible reaction mechanism for HClO and H 2 S in CH 3 CN/PBS (9/1, v/v) was substantiated via 1H NMR and HRMS. Above all, MTRN was successfully used to detect HClO and H 2 S in HeLa cells and made into test strips to detect HClO and H 2 S. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple probe has been developed for the "turn-on" fluorescent detection of ClO− based on aggregation-induced emission. • The probe could monitor ClO− with low detection line (246 nM) in semi-aqueous solution. • The probe worked within wide pH rang of 2.0–13.0, and the process of quench completed within 10 s. • The probe has been successfully used for monitoring exogenous and endogenous ClO− in living cells. In this study, we developed a benzo[ h ]chromene-based probe (1) for the detection of hypochlorite (ClO−) based on a typical aggregation-induced emission (AIE) output. Probe 1 shows high selectivity and sensitivity toward ClO−, with a rapid response speed (within 10 s) and a low detection limit (246 nM). Sufficient spectroscopic analyses uphold the oxidation fracture of bridge C=C bond with the aid of ClO−, leading to the change of 1 to 2H-benzo[h]chromene-3-carbaldehyde (1a). In addition, the as-synthesized probe was applied in imaging exogenous and endogenous ClO− in living cells. [ABSTRACT FROM AUTHOR]

Phosphorus and nitrogen doped carbon dots (PN-CDs) were conveniently prepared by carbonization of adenosine-5′-triphosphate using a hydrothermal treatment. The PN-CDs with P/C atomic ratio of ca. 9.2/100 emit blue luminescence with high quantum yields of up to 23.5%. The PN-CDs were used as a novel sensing platform for live cell imaging of reactive oxygen species (ROS) and reactive nitrogen species (RNS), including ClO − , ONOO − , and NO in macrophages. The nanosensor design is based on our new finding that the strong fluorescence of the PN-CDs can be sensitively and selectively quenched by ROS and RNS both in vitro and in vivo. These results reveal that the PN-CDs can serve as a sensitive sensor for rapid imaging of ROS and RNS signaling with high selectivity and contrast. [ABSTRACT FROM AUTHOR]

A novel nanoparticle with multilayer core–shell architecture for cell imaging is designed and synthesized by coating a fluorescent YVO 4 :Eu core with a diblock copolymer, MPEG- b -PMAA. The synthesis of YVO 4 :Eu core, which further makes MPEG- b -PMAA-YVO 4 :Eu NPs adapt for cell imaging, is guided by the model determined upon the evaluation of pH and C Eu% . The PMAA block attached tightly on the YVO 4 :Eu core forms the inner shell and the MPEG block forms the biocompatible outermost shell. Factors including reaction time, reaction temperature, C Eu% and pH are optimized for the preparation of the YVO 4 :Eu NPs. A precise defined model is established according to analyzing the coefficients of pH and C Eu% during the synthesis. The MPEG- b -PMAA-YVO 4 :Eu NPs, with an average diameter of 24 nm, have a tetragonal structure and demonstrate luminescence in the red region, which lies in a biological window (optical imaging). Significant enhancement in luminescence intensity by MPEG- b -PMAA-YVO 4 :Eu NPs formation is observed. The capping copolymer MPEG- b -PMAA improves the dispersibility of hydrophobic YVO 4 :Eu NPs in water, making the NPs stable under different conditions. In addition, the biocompatibility MPEG layer reduces the cytotoxicity of the nanoparticles effectively. 95% cell viability can be achieved at the NPs concentration of 800 mg L −1 after 24 h of culture. Cellular uptake of the MPEG- b -PMAA-YVO 4 :Eu NPs is evaluated by cell imaging assay, indicating that the NPs can be taken up rapidly and largely by cancerous or non-cancerous cells through an endocytosis mechanism. [ABSTRACT FROM AUTHOR]

Time-resolved fluorescence technique can reduce the short-lived background luminescence and auto-fluorescence interference from cells and tissues by exerting the delay time between pulsed excitation light and signal acquisition. Here, we prepared persistent luminescence nanoparticles (PLNPs) to design a universal time-resolved fluorescence resonance energy transfer (TR-FRET) platform for biosensing, lifetime imaging of cell apoptosis and in situ lifetime quantification of intracellular caspase-3. Three kinds of PLNPs-based nanoprobes are assembled by covalently binding dye-labeled peptides or DNA to carboxyl-functionalized PLNPs for the efficient detection of caspase-3, microRNA and protein. The peptides-functionalized nanoprobe is also employed for fluorescence lifetime imaging to monitor cell apoptosis, which shows a dependence of cellular fluorescence lifetime on caspase-3 activity and thus leads to an in situ quantification method. This work provides a proof-of-concept for PLNPs-based TR-FRET analysis and demonstrates its potential in exploring dynamical information of life process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel benzocoumarin-based fluorescent probe BL for monitoring HOCl was designed and synthesized. • BL exhibits simple synthesis, excellent selectivity, fast response (<60 s), high sensitivity (DL, 5.64 nM). • BL was successfully applied to detect HClO spiked in tap water, 84 disinfectants and lake water, and has achieved satisfying recovery rates. • BL could readily fabricate solid-state visual sensors to be used to convenient detect HClO. • BL was nontoxic andsuccessfully used to monitor the variations of endogenous/exogenous HOCl in live RAW 264.7 macrophages. Hypochlorous acid (HOCl) is widely used in daily production and life. It is also a kind of endogenously produced reactive oxygen species (ROS) in the human immune system, plays a crucial role in many pathophysiological processes. This work designed and synthesized a novel based on benzocoumarin fluorescent probe BL for specific detection HOCl. BL has brilliant selectivity, high sensitivity (5.64 nM), fast response (60 s), moderate water-solubility. The intramolecular charge transfer (ICT) sensing mechanism of BL has been verified by fluorescence, UV, MS, and density functional theory (DFT) calculations. BL can make into a solid-state visual sensor to detect HOCl conveniently. BL was also applied to detect HClO spiked in tap water, 84 disinfectants, lake water, and satisfying recovery rates. Finally, BL was low toxic and used to track the variations of endogenous/exogenous HClO in living cells successfully. Totally, BL provides a powerful and reliable monitoring tool to reveal the biological functions of HOCl and ensure safe use. [ABSTRACT FROM AUTHOR]

[Display omitted] • We developed a novel near-infrared (NIR) fluorescent probe Cy-BNN for sensing pH under extremely acidic conditions. • The pk a value of Cy-BNN as low as 3.32. • Cy-BNN could be used for monitoring pH changes in the mitochondria of living cells. In this paper, a novel near-infrared (NIR) fluorescent probe Cy-BNN for sensing local microscopic pH under extremely acidic conditions (pH < 4) was constructed and reported. For the preparation of Cy-BNN , a barbituric acid moiety was fused in the polymethine chain of the cyanine dye to introduce nitrogen atoms as protonation center. In different pH, the balance of quaternary ammonium salts and free amines of Cy-BNN was adjusted, and the pk a value of Cy-BNN was calculated based on the Sigmoidal equation. Surprisingly, the pk a value of Cy-BNN as low as 3.32, implying that Cy-BNN can be used for sensing extreme acidity. As expected, Cy-BNN exhibited highly selective response to H+ over diverse analytes, and can be used to monitoring the intracellular pH fluctuation under extremely acidic conditions. Importantly, Cy-BNN can be used to specifically target mitochondria, providing potential possibilities for monitoring mitochondria–lysosome interactions in live cells and mitophagy process. [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 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]

A naphthalimide-based fluorescent probe CP has been synthesized with simple steps. It can selectively and sensitively recognize copper ions (Cu 2+ ) in HEPES buffer (50 mM, pH 7.2). The fluorescence intensity of CP is linearly proportional to the concentration of Cu 2+ ranging from 0–8.3 μM (correlation coefficient R 2 =0.9808). The resulted complex CP@Cu can serve as a turn-on fluorescent probe for the detection of histidine and histidine rich proteins in broad pH application range. Upon the addition of histidine, the fluorescence intensity of CP@Cu exhibits a linear correlation with the concentration of histidine ranging from 0–200 μM (correlation coefficient R 2 =0.9912). Moreover, CP@Cu has potential for imaging histidine in vitro experiments and has promise in real sample applications with great validity. [ABSTRACT FROM AUTHOR]

Abstract: Acrylic acid 3-acetyl-2-oxo-2 H-chromen-7-yl ester (ACA) was rationally designed and synthesized as a simple and effective fluorescent probe for sensing cysteine with high selectivity and naked-eye detection. The probe can detect cysteine by fluorescence spectrometry with a detection limit of 0.657μM and can be used with calf serum and in live cell imaging. The conjugate addition/cyclization sequence mechanism of the reaction between ACA and cysteine was confirmed by ESI-MS and fluorescence spectra. [Copyright &y& Elsevier]

Abstract: We report a novel colorimetric and red-emitting fluorescent probe for hydrazine detection based on resorufin platform. This OFF–ON fluorescent probe shows a large (117nm) red-shifted absorption spectrum and the color changes from colorless to red upon addition of hydrazine in the aqueous solution, which can serve as a “naked-eye” probe for hydrazine. Moreover, this probe also shows a significant fluorescence increase (~16 folds) and excellent linear relationship at physiological pH. Utilizing this sensitive and selective probe, we have successfully detected hydrazine in living cells. [Copyright &y& Elsevier]

[Display omitted] • Synthesis of 1,1′-((1E,1′E)-((4,5-dimethyl-1,2-phenylene)bis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol) (PAMN). • Spectroscopic and photochemical investigations of PAMN. • PAMN exhibited a high sensitivity and selectivity toward Al3+ in DMSO-H 2 O (1:1 v/v, pH = 7.20) by forming a 1:1 complex with Al3+ ion. • PAMN was valid for fluorescence imaging of Al3+ in the Hela cell lines. A novel efficient fluorescent probe 1,1′-((1E,1′E)-((4,5-dimethyl-1,2-phenylene)bis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol) (PAMN) for the recognition of Al3+ was synthesized and extensively characterized using various physicochemical techniques. Free PAMN fluoresced weakly, but when aluminium added, it fluoresced dramatically against various metal ions. The recognition process was relied mainly on the chelation-controlled C=N isomerization combined with an inhibition of the excited-state intramolecular proton transfer (ESIPT). The energies of both HOMO and LUMO for PAMN and PAMN-Al3+ complex were estimated by DFT calculations to elucidate the configuration of the complex. PAMN coordinated with Al3+ in [1:1] stoichiometry with an association-constant of 2.18 × 105 M−1. Upon coordination with Al3+ ions , PAMN displayed a good linear relationship in extremely low concentrations with a limit of detection of 7.05 × 10−9 M. The living-HeLa-cell imaging displayed that the probe had excellent cell membrane permeability, with great potential for intracellular Al3+ ion tracing via the fluorescence imaging technique. [ABSTRACT FROM AUTHOR]

Abstract: The 4-propargylamino-1,8-naphthalimide based fluorescent probe 1 has been explored as a sensor for selective detection of Au3+. 4-Amino-1,8-naphthalimides, that possess typical intramolecular charge transfer (ICT) electronic characteristics, have been widely used as versatile platforms for fluorescent probes. The newly designed probe 1 contains a propargylamine moiety at C-4 of the naphthalimide chromophore that reacts with Au3+ to generate a product that has distinctly different electronic properties from 1. Specifically, the probe undergoes a remarkable change in its absorption spectrum upon addition of Au3+ that is associated with a distinct color change from yellow to light pink. In addition, a blue shift of ca. 56nm also takes place in the emission spectra of the probe. Consequently, 1 serves as a reaction-based sensor or so called chemodosimeter for Au3+. Importantly, surfactants enhance the rate of reaction of 1 with Au3+, thus, enhancing its use as a real time sensor. Finally, the results of studies probing its application to bioimaging of Au3+ in live cells show that the probe 1 has a unique ability to sense Au3+ in cells and, in particular, in lipid droplets within cells. [Copyright &y& Elsevier]

Abstract: A new fluorescent nanoprobe, 4-amino-2,2,6,6-tetramethylpiperidine oxide (AT)-functionalized CdTe quantum dots (QDs–AT), was synthesized, for selective detection of nonprotein thiols based on electron transfer (ET). In the presence of nonprotein thiols, the nitroxide radicals in QDs–AT were converted to hydroxylamines, resulting in the fluorescence recovery of the quenched QDs. The detection mechanism of the probe was investigated using Rh-Se-2 probe. The nanoprobe has high sensitivity toward glutathione (GSH) with a detection limit of 7.1×10−8 M. The fluorescent imaging of living cells showed that QDs–AT could distinguish the concentration differences of GSH in HL-7702 and HepG2 cells. [Copyright &y& Elsevier]

• Based on a series of D-π-A and A-π-A' fluorescent probes to study the effect of end groups on its performance. • This series of probes can be used to detect endogenous SO 3 2− • This series of probes has high sensitivity and selectivity to SO 3 2− Based on the addition reaction of sulfur dioxide derivatives and C C , a series of D-π-A and A-π-A' fluorescent probes were designed by combining different electronic groups with benzoindole to study the influence of different end groups on the performance of such probes. When sulfite is detected, the fluorescence of ratio-type probe changes from red to blue, the fluorescence of turn-on probe changes from colorless to blue. The response time ranges from 90–300 s, the detection limit ranges from 10 nM–70 μM and the Stokes shift ranges from 1800 to 6800 cm−1, all with high specificity. In addition, A2 has been successfully applied to cell imaging of endogenous sulfur dioxide derivatives. [ABSTRACT FROM AUTHOR]

In this work, a new turn-on near-infrared fluorescent probe based on N , N -dimethylaniline as a donor and pyridinium group as an acceptor has been successfully constructed for superoxide anion detection, which exhibits a remarkable fluorescence enhancement with a low limit of detection and an excellent mitochondrial targeting effect in MCF-7 cells with good biocompatibility after treatment of lipopolysaccharide. [Display omitted] • A new fluorescent probe DMPS-O for O 2 •- detection with a large Stokes shift was developed. • DMPS-O showed a remarkable near-infrared fluorescence enhancement after reacting with O 2 •-. • DMPS-O was suitable for detecting endogenous O 2 •- in MCF-7 cells. • DMPS-O was capable of locating mitochondria in cells. Superoxide anion (O 2 •-), as a kind of crucial reactive oxygen species (ROS), often causes a series of oxidative damage and various biological dysfunction when it is excessive in cells. Compared with other detection methods, fluorescence detection is often used for cell imaging due to its high temporal and spatial resolution. Hence, a novel "turn-on" fluorescent probe DMPS-O based on N , N -dimethylaniline as a donor and pyridinium group as an acceptor was designed and synthesized to detect superoxide anion. DMPS-O showed a remarkable fluorescence enhancement in the near-infrared region and a large Stokes shift after reacting with superoxide anion and its limit of detection was calculated to be 22.2 nM. Finally, CCK-8 and confocal fluorescence imaging experiments revealed that the fluorescent probe DMPS-O with low cytotoxicity was suitable for detecting endogenous superoxide anions and locating mitochondria in the MCF-7 and HepG2 cells. [ABSTRACT FROM AUTHOR]