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Monitoring hydrogen sulfide (H2S) in living organisms is very important because H2S acts as a regulator in many physiological and pathological processes. Upregulation of endogenous H2S concentration has been shown to be closely related to the occurrence and development of tumors, atherosclerosis, neurodegenerative diseases and diabetes. Herin, a novel fluorescent probe HND with aggregation-induced emission was designed. Impressively, HND exhibited a high selectivity, fast response (1 min) and low detection limit (0.61 μM) for H2S in PBS buffer (10 mM, pH = 7.42). Moreover, the reaction mechanism between HND and H2S was conducted by Job's plot, HR-MS, and DFT. In particular, HND was successfully employed to detect H2S in HeLa cells. [ABSTRACT FROM AUTHOR]

A new structurally simple fluorescent CP probe based on chromone was designed and synthesized, and its structure was fully characterized using various analytical techniques. The CP probe displays a high selectivity and sensitivity for sensing Fe3+ with a "turn-off" fluorescence response over other metal ions in a DMSO/H2O (4:1, v/v) solution. The experiment results show that the CP probe is stable over a wide pH range of 2.0–12.0. The detection limit for Fe3+ was calculated to be 0.044 μmol•L−1. The molar ratio method indicated that the binding mode between the CP probe and Fe3+ is a 1:1 complex formation. HR-MS and density functional theory (DFT) calculations were also performed to further confirm the recognition mechanism. Both fluorescence imaging experiments and the MTT assay demonstrated that the CP probe was suitable for detecting intracellular Fe3+ and no significant cytotoxicity in living cells. [ABSTRACT FROM AUTHOR]

Given the important role of carboxylesterase 2 (CES2) in the metabolism of various esters, it is of significance to develop a tool to determine endogenous CES2 activity in a rapid and highly selective manner. In this work, an "off-on" rhodamine-based fluorescent probe is reported as an effective tool for CES2 activity. Based on the substrate recognition preference of CES2 (large alcohol and small acyl groups), the probe with dimethyl carbamate as the recognition group performs well in terms of selectivity and sensitivity to CES2. The fluorescence switching control of the probe for CES2 was achieved by using the spirolactone structure of rhodamine. The probe shows the fast generation of a fluorescence signal at 634 nm upon hydrolysis of CES2 with excitation at 578 nm. The results showed a linear relationship between the fluorescence intensity at 634 nm and the CES2 activity from 0 to 4 μg/mL. The probe reacts rapidly with CES2, and the reaction is stable within 40 minutes. The probe is highly selective for CES2, with a detection limit as low as 0.303 μg/mL. In addition, the probe has currently been successfully utilized to evaluate CES2 activity in living cells. Hence, this probe is anticipated to be significant in identifying endogenous CES2 activity in intricate biological settings. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe based on azamonardine (Aza) fluorophore was designed and synthesized for the highly selective detection of cysteine (Cys) in vivo and in vitro. After reacting with acryloyl chloride, the fluorescence of Aza is effectively quenched, resulting in the formation of the Aza-acryl probe. Upon the addition of Cys, the ester bond of Aza-acryl is cleaved, releasing a new compound (Compound 1) with strong fluorescence, thereby achieving fluorescence turn-on detection of Cys. The structure of Aza-acryl was characterized using X-ray crystallography and NMR spectroscopy. Additionally, density functional theory was employed to elucidate the quenching mechanism of the acyl group on the Aza. Aza-acryl exhibits high selectivity towards Cys and distinguishes it from other biothiols such as homocysteine (Hcy) and glutathione (GSH). The mechanism of Aza-acryl for detecting Cys was investigated through HPLC, NMR spectroscopy, high-resolution mass spectrometry, and reaction kinetics experiments. Aza-acryl demonstrates excellent imaging capabilities for Cys in cells and zebrafish, providing a reliable and selectable tool for the detection and imaging of Cys in biological systems. [ABSTRACT FROM AUTHOR]

Endogenous sulfur dioxide (SO2), as a gas signal molecule, has a certain physiological functions. Understanding the role of endogenous SO2 in human physiology and pathology is of great significance to the biological characteristics of SO2,which bring challenges to develop fluorescent probes with excellent performance. Herein, we rationally designed and constructed a novel near-infrared bioprobe benzaldehyde-benzopyrylium (BBp) by employing the nucleophilic addition benzopyrylium perchlorate fluorophore and benzaldehyde moiety by means of C = C/C = O group that serves as both fluorescence reporting unit. Probe BBp exhibit excellent sensing performance with fluorescent "On − Off"rapid response (100 s) and long-wavelength emission (670 nm). With the treatment of HSO3−, the color of BBp solution obviously varies from purple to colorless, and the fluorescent color varies from red to colorless. By the fluorescence and colorimetric changes, probe BBp was capable of sensitive determination HSO3− with low limits of detection (LOD) of 0.43 μM, realizing visual quantitative monitoring SO2 derivative levels. Due to the low phototoxicity and good biocompatibility, it was successfully applied to monitor SO2 derivatives and fluorescence imaging in HepG2 and HeLa living cells. Hopefully, this work supplies a new strategy for designing NIR fluorescent probes for quantitative determination SO2 derivatives in biological samples. [ABSTRACT FROM AUTHOR]

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt 2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N′ -diethylaminocoumarin (CM(NEt 2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt 2) with β-hexosaminidase promoted generation of Rhod-CM(NEt 2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt 2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with k cat and K m values of 17 sec−1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt 2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt 2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme. [Display omitted] • Development of the sensitive and selective fluorescent probe for β-hexosaminidase. • Determination of levels of β-hexosaminidase activities in several types of cells. • Evaluation of effect of glucose concentrations in media on β-hexosaminidase activity. [ABSTRACT FROM AUTHOR]

In this work, dual-emissive ratiometric fluorescent system was constructed by the introduction of an ideal internal reference. By virtue of its unique alkalinity, N2H4 could undergo a hydrazinolysis reaction with the ester group of F1, inducing remarkable fluorescence enhancement while the blue fluorescence of the internal reference DPA remained constant. Consequently, the fluorescence intensity ratios (I540/I440) were proportional to the concentrations of N2H4, which was beneficial for the exactly quantitative detection. The skillful strategy granted the sensing system advantages such as relative good solubility in aqueous media, easy-to-design, simple synthesis, large emission shift, good ratiometric response, as well as the successful application in real water samples and cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two spirobifluene-based turn-on fluorescent probes for Cysteine were synthesized. • The probes shows highly selectivity for Cysteine. • The probes had been applied to imaging Cysteine under two-photon excitation. • One probe displayed excellent detection limit for Cysteine. Two spirobifluene-based fluorescent probes SPF1 and SPF2 , were designed and synthesized. The probes displayed "turn-on" fluorescence response for Cysteine. One of the challenges in developing a Cysteine probe is to secure high selectivity. SPF1/SPF2 can discriminate Cysteine from GSH as well as Hcy, and showed high substrate selectivity. The detection limit of SPF1 is 36 nM, which is excellent comparing with other optical sensors for Cysteine. The sensing mechanism of SPF1/SPF2 was verified by experimental data and theoretical calculations. There was a good linear relationship between the fluorescence intensity of SPF1/SPF2 and the concentration of Cysteine. The MTT tests indicated that SPF1/SPF2 had low cytotoxicity and good biocompatibility. Theoretical calculations demonstrated that SPF1 , SPF2 , and their related reaction products with Cysteine exhibited good two-photon absorption properties. Finally, SPF1/SPF2 had been successfully applied to the imaging of Cysteine in living cells under two-photon excitation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Al3+ Schiff base probe JHK was designed and synthesized. • JHK has high selectivity, high fluorescence quantum yield and low detection limit for Al3+. • JHK was successfully applied to living cells and zebrafish. A novel fluorescent probe N'-(2-hydroxybenzylidene)-indole-3-formylhydrazine (JHK) was designed and synthesized based on the condensation reaction of indole-3-formylhydrazine and salicylaldehyde. The probe JHK solution could highly selectively recognize Al3+ by the obvious fluorescence enhancement (288-fold) after adding Al3+. And the probe solution with Al3+ had a very high fluorescence quantum yield (89.29 %). The detection limit was calculated to be 1.135 nM, which was significantly lower than many reported detection limits, indicating that the probe JHK had pretty good sensitivity. The ratio of JHK to Al3+ (1:1) and the sensing mechanism were determined by Job's plot, 1H NMR spectra, FTIR spectra, ESI-MS and Gaussian calculation. The probe solution and medium-speed filter paper were successfully used to make test papers for more convenient detection of Al3+. Furthermore, the probe JHK had been successfully applied to the detection of Al3+ in real water, zebrafish and living cells. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a multifunctional gaseous signaling molecule that plays a vital role in several biological processes. In the present study, a BODIPY-based fluorescent probe called 8-[4-((1,4,7,10-tetraazacyclododecane)methyl)phenyl]-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza- s -indacene (BA–Cyclen)–Cu was designed and synthesized; this probe is a Cu(Ⅱ) complex that uses Cu(Ⅱ) decomplexation to achieve the sensitive and rapid detection of aqueous H 2 S via the "turn-on" mode. We observed that BA–Cyclen–Cu exhibited good membrane permeability, low toxicity, and lysosome-targeting ability, facilitating H 2 S detection in living cells. Furthermore, we demonstrated the potential biological applications of the probe by measuring exogenous H 2 S originating from Na 2 S and GYY4137, a slow-release donor, and endogenous H 2 S generated via the catalysis of cystathionine- β -synthase in both normal (H9c2) and cancerous (U87) cells. Moreover, BA–Cyclen–Cu was successfully used to detect exogenous H 2 S by the external standard method in fetal bovine serum, the serum of a healthy person, and the serum of a patient with liver cancer. [Display omitted] • BA-Cyclen-Cu displayed high selectivity, sensitivity and fast response toward H 2 S with "turn-on" mode. • BA-Cyclen-Cu have a good performance on exogenous/endogenous H 2 S sensing in cancer cells and normal cells. • BA-Cyclen-Cu was successfully used to detect H 2 S in serum samples. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide and biothiol molecules such as Cys and GSH acted important roles in many physiological processes. To simultaneously detect and distinguish them was quite necessary by a suitable fluorescent probe. A novel chemosensor 4-(4-(benzo[d]thiazol-2-yl)-2-methoxyphenoxy)-7-nitrobenzo[c][1,2,5]oxadiazole (BMNO) was designed to detect H2S/Cys/GSH using the combination of nitrobenzofurazan (NBD) and benzothiazole fluorophores linked by a facile ether bond. The probe BMNO was developed for simultaneous identification of H2S, Cys and GSH. Noticeably, the color changes (from colorless to light purple, light orange and light yellow) of probe BMNO solutions for sensing H2S, Cys and GSH could be observed by naked eyes, respectively. The probe BMNO exhibited high selectivity and sensitivity for H2S, Cys and GSH showing distinct optical signal with detection limit as low as 0.15 μM, 0.03 μM and 0.14 μM, respectively. The sensing mechanism was clarified by spectrum analysis and some controlled experiments. In addition, these outstanding properties of probe BMNO enabled its practical applications in detection H2S in beer, and in cell imaging for Cys and GSH as well. [ABSTRACT FROM AUTHOR]

An endoplasmic reticulum (ER) targetable two-photon fluorescent probe termed ER-N3 is presented for the determination of hydrogen sulfide (H2S) in living cells and mice. The results demonstrate that ER-N3 was highly selective and sensitive to H2S. Confocal fluorescence imaging in living cells indicated that ER-N3 was accumulated in the endoplasmic reticulum and visualized exogenous and endogenous H2S production. Moreover, a burst of H2S upregulated by the nitric oxide donor sodium nitroprusside was monitored. Meanwhile, the increase of H2S ended following the addition of DL-propargylglycine, an inhibitor for cystathionine β-synthase and cystathionine γ-lyase that are the main sources of H2S. Importantly, the exogenous H2S was visualized in abdominal tissue of mice by utilizing two-photon fluorescence microscopy. The ER-N3 fluorescent probe may be an excellent tool to image H2S fluctuations in the endoplasmic reticulum and characterize the relationship between H2S and disease in vivo. [ABSTRACT FROM AUTHOR]

Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and synthesized a novel Cd2+ fluorescence probe based on the pyridine-pyrimidine structure, 4-(methylsulfanyl)-6-(pyridin-2-yl)pyrimidin-2-amine (3), as a low-molecular-weight fluorescence probe for Cd2+. Compound 3 could successfully discriminate between Cd2+ and Zn2+ and exhibited a highly selective turn-on response toward Cd2+ over biologically related metal ions. The dissociation constant (Kd) and the limit of detection (LOD) of 5.4 × 10− 6 mol L− 1 and 4.4 × 10− 7 mol L− 1, respectively, were calculated using fluorescence titration experiments. Studies with closely related analogs showed that the bis-heterocyclic moiety of 3 acted as both a coordination site for Cd2+ and a fluorophore. Further, the methylsulfanyl group of compound 3 is essential for achieving selective and sensitive Cd2+ detection. Fluorescence microscopy studies using living cells revealed that the cell membrane permeability of compound 3 is sufficient to detect intracellular Cd2+. These results indicate that novel bis-heterocyclic molecule 3 has considerable potential as a fluorescence probe for Cd2+ in biological applications. [ABSTRACT FROM AUTHOR]

It is well known that sulfite (SO32−) plays an indispensable role in various physiological processes. Abnormal levels of SO32− can trigger a wide variety of diseases involving respiratory, nervous and cardiovascular systems. Hence, it is necessary to find an efficient approach for detection of SO32−. In this study, a pyrene derivative, (E)-4-(3-oxo-3-(pyren-1-yl)prop-1-en-1-yl)phenyl acrylate (PPA), was designed and synthesized for monitoring SO32−. The probe possessed simple synthetic steps, excellent anti-interference ability and specific response to SO32− in the presence of other substances. The reaction between PPA and SO32− was ascribed to Michael addition and the detection mechanism was confirmed by HRMS spectra analysis and FTIR analysis. Additionally, PPA responded linearly to detect SO32− within the rang of 0–100 μM. The limit of detection was calculated as low as 0.17 μM in accordance with the recommendation of IUPAC (CDL =3sb/m). Notably, PPA was further applied in biological imaging in HepG2 cells, which provided a possibility to monitor SO32− in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel probe BD-C based on the FRET-ICT mechanism was designed to detect cysteine. • Probe BD-C had superior selectivity without the interference of other biological thiols. • Probe BD-C had large Stokes shift and the energy transfer efficiency reached 98.8%. • Probe BD-C had superior endoplasmic reticulum-targeting. Cysteine is an important thiol amino acid that is abundantly present in cells and has an important function in various life processes of the human body. Therefore, it is of great significance to develop an accurate method for monitoring cysteine concentration in cells. We designed and synthesized a novel FRET-ICT-based ratiometric fluorescence and colorimetric probe (BD-C) for detecting cysteine. As cysteine was gradually added, the fluorescence intensity of probe BD-C in buffer solution decreased at 614 nm and increased at 428 nm. The logarithm of the fluorescence intensity ratio to cysteine exhibited favorable linearity in the concentration range of 0.5–14.0 μM, with a detection limit of 395 nM. The energy transfer efficiency of this FRET system is up to 98.8%. BD-C demonstrated preeminent selectivity for cysteine and could specifically react with cysteine, though other sulfhydryl amino acids, such as GSH and Hcy, were present. Furthermore, BD-C exhibited outstanding targeting ability to the endoplasmic reticulum (ER) and was successfully applied in cellular imaging. [ABSTRACT FROM AUTHOR]

Intracellular viscosity is closely related to a series of biological processes and could be a biomarker for various diseases. Herein, we reported a deep-red emission viscosity probe ACI, which showed a turn-on fluorescence effect with excellent selectivity encountering high viscous medium. To assure the practical biological application, ACI demonstrated not only a long wavelength emission at 634 nm but also a long wavelength excitation at 566 nm, which were crucial to afford deeper penetration depth and higher sensitivity in bioimaging. The photophysical properties and viscosity recognition mechanism of the probe were carefully discussed here. Theoretical calculations furtherly confirmed that high viscous medium could inhibit the twisted intramolecular charge transfer (TICT) process of the probe which quenched the fluorescence in low viscous media, and restore the emission. More importantly, it was successfully applied to visualize the viscosity in living cells. [ABSTRACT FROM AUTHOR]

A new fluorescence probe 1 for sulfur dioxide derivatives has been developed which acts through nucleophilic addition of the derivatives and shows high stability, specificity, and sensitivity. In the presence of SO2 derivatives, the fluorescence intensity of probe 1 significantly decreases within a short time period of 40 s, along with a low detection limit of 0.32 µM. Fluorescence imaging capability of probe 1 was also investigated, showing clear detection of SO2 derivatives in living cells. The results indicate that this probe has a great potential for the detection of SO2 derivatives in broad biological and relevant samples. [ABSTRACT FROM AUTHOR]

Biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play key roles in biological processes, and detecting such thiols selectively is critical for understanding functions of biothiols. In this work, a pyridazine annelated perylene–based fluorescent probe PAPC is synthesized for highly selective detection of Cys. PAPC exhibits strong blue emission in PBS, while the red emission at 605 nm can be observed in the presence of Cys. The probe PAPC shows ratiometric fluorescence (I605/I460) detection of Cys with wide linear range of 1–120 μM and low detection limit of 0.19 μM. Super large Stokes shift (170 nm) and ratiometric fluorescence endow the probe low background signal. The discrimination of Cys over Hcy and GSH can be achieved through the difference of the ratiometric fluorescence. In addition, the probe has been proven to track Cys in real samples such as urine and HeLa cells. Therefore, PAPC probe is a promising candidate for detecting Cys in practical application. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a critical gasotransmitter playing an important role in various physiological and pathological processes. The development of fluorescent probes for rapid, sensitive, and selective lysosomal H2S sensing has attracted much attention. Herein we report a rhodamine based probe MF‐N3 that can selectively accumulate in lysosomes and give turn‐on fluorescence in the presence of both H2S and protons. Results show that MF‐N3 has an exclusive response to H2S in the acidic lysosomal environment but does not respond in other organelles or in neutral environments. This strategy can circumvent the fluorescence interference from H2S of other sources, thus providing a high sensitivity and selectivity on lysosomal H2S imaging by fluorescence microscopy. This pH‐dependent lysosome‐targeting fluorescent probe has been successfully applied to lysosomal H2S imaging in living cells and is of great potential for applications to the environmental and biological systems. [ABSTRACT FROM AUTHOR]

A colorimetric and fluorescence turn-off probe 10-(4-azido phenyl)-5,5-difluoro-5h-dipyrrolo[1,2-c:1',2'-f][1,3,2] diazaborinin-4-ium-5-uide, 1, for selective detection of H2S is reported. The probe displayed a robust decrease in fluorescence intensity with high sensitivity, specificity and least toxicity to detect exogenous H2S and also in live normal human oral fibroblast cells loaded with probe 1. The detection limit of probe 1 being 0.17 µm for H2S. A colorimetric and fluorescence turn-off BODIPY probe 1, for selective detection of exogenous H2S in live normal human oral fibroblast cells loaded with probe 1 and poisonous H2S gas formed under biodegradation in sewage waters and water tanks and corroded pipe lines. The detection limit of probe 1 being 0.17 μM [ABSTRACT FROM AUTHOR]

The spectroscopic properties for a number of new hydroxylated 2-stilbazoles were studied by absorption and fluorescence spectroscopy. The maximum absorption and emission wavelengths, the molar extinction coefficients, and the Stokes shift values of derivatives were given. The dependence of the spectral characteristics on pH was shown. The possibility of creating molecular logic systems and fluorescent dyes for bioimaging based on these derivatives was demonstrated. The dependence of fluorescence on the medium redox properties was established for an one of derivatives. The possibility of a fluorescent probe creating on its basis to assess the oxidative state of living systems was demonstrated. The probe has good biocompatibility and can be successfully used for fluorescence imaging in cells. [ABSTRACT FROM AUTHOR]

In this paper, a new strategy was presented for fluorescence labeling and imaging Al3+ in live cells with excess aluminum ions using thiolated fluorescence gold nanoclusters (Au NCs). The glutathione (GSH)-capped Au NCs were prepared via a green, facile one-pot method in aqueous solution and displayed excellent stability, ultrasmall size, monodispersity, and larger Stokes shift, which exhibits a relatively weak fluorescence at 650 nm Al3+-induced fluorescence enhancement of the GSH-Au NCs can be observed due to Al3+-triggered aggregation-induced emission (AIE) effect, which allows the role of GSH-Au NCs as a fluorescence light-up probe for detection of Al3+. Moreover, it was demonstrated that the fluorescence probe for Al3+ showed a wide detection range from 100 to 600 μM and good selectivity against other metal ions and common biomolecule. Furthermore, due to the advantages of excellent biocompatibility, low toxicity, red emission and high specificity, the proposed GSH-Au NCs fluorescence probes are suitable for the imaging of high concentrations of aluminum ions in cells, which can be applied to the diagnosis of cellular aluminum poisoning. Schematic illustration of the synthesis process of GSH-Au NCs and the fluorescence enhancement of GSH-Au NCs after adding Al ion due to the Al3+ triggered aggregation of the GSH-Au NCs. Image 1 • First report of the Al3+ rapid fluorescence detection in live cells with excess aluminum ions using thiolated Au NCs. • Al3+ as linkers can induce photoluminescence boost of thiolated Au NCs nearly 40-fold through AIE. • The biosensor is suitable for imaging of excess aluminum ions in cells due to their hypotoxicity, red emission of 650 nm. [ABSTRACT FROM AUTHOR]

A fluorescence-enhanced and lysosome-targeted Al3+ probe (1) based on a pyrazole-containing hydrazone was developed in this work. The fluorescent probe 1 displays an OFF–ON fluorescence response to Al3+ in the lysosome pH environment. In addition, the resultant 1 –Al3+ complex could act as an ON–OFF fluorescence sensor for F−. Fluorescence imaging shows that 1 is suitable for visualization of Al3+ in lysosomes of HeLa cells. Image 1 • A quite simple hydrazone-based fluorescent probe for Al3+ has been developed. • The probe displayed an OFF-ON response toward Al3+ in aqueous solution. • The resultant Al3+ complex of the probe could act as an on-off fluorescent sensor for F−. • The probe has been used for imaging of Al3+ in lysosomes of HeLa cells. [ABSTRACT FROM AUTHOR]

• Small molecule fluorescence probe. • Highly selective for Ni (II) (≥160-fold). • Compatible with living cells. • Simple and low-cost detection. In this paper, we unveil a new highly selective and sensitive mito-tracker (NiP) for Ni2+ detection. NiP itself held very weak fluorescence and exhibited a high selectivity (≥160-fold) toward Ni2+ over other metal ions, with a limit of detection of 21.6 nmol. We demonstrate the practicality of NiP for the rapid determination of Ni2+ levels in mitochondria of living cells. This approach offers advantages by being fast, simple and low cost. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are an important organelle as the main energy storage site in cells. LDs viscosity controls the material and energy exchange between it and other organelles. Furthermore, the LDs metabolic abnormalities, cell dysfunction, some diseases may be attributed to the singular LDs viscosity. Currently, the fluorescent probes for sensing the variations of LDs viscosity are still scarce and expose some drawbacks of low fluorescence quantum yield, low sensitivity and LDs polarity interference. Thus, the development of high performance probes is significant to detect LDs viscosity. We hereby provide a lipophilic fluorescent probe (TPE-BET) with high fluorescence quantum yield (Φ f , 0.91 in glycerol) for imaging LDs viscosity in living cells. With the increase of viscosity from 0.54 cp to 934 cp, the fluorescence at λ ex /λ em = 405/520 nm and the fluorescence quantum yield of TPE-BET linearly increased by 64.9 and 128.5 folds, respectively. Meanwhile, the outstanding LDs staining capability of TPE-BET may provide a high spatial resolution for LDs imaging. The cell imaging of TPE-BET not only successfully observed the viscosity variations of LDs in cell stress models, e.g., ferroptosis, inflammation and mitophagy, but also revealed the increased viscosity and extracellular delivery of LDs in heavy metal cell injury models (Hg/As) for the first time, which may supply concrete evidence for understanding the structure and function of LDs. This represents a new fluorescent probe TPE-BET with high fluorescence quantum yield for imaging LDs viscosity, which may decrease the dose of probe and excitation light intensity along with the improvement on signal noise ratio (S/N). The imaging results of TPE-BET clarified that LDs viscosity may be an appraisal index on cell differentiation, state evaluation and drug screening. [Display omitted] • A lipophilic probe (TPE-BET) with high fluorescence quantum yield was developed for imaging lipid droplet (LDs) viscosity. • TPE-BET shows high spatial resolution, which provide information including the distribution, size and morphology of LDs. • The LDs viscosity was detected in various cell models such as ferroptosis, mitophagy and heavy metal cell injury models. • LDs viscosity may be an appraisal index on cell differentiation, state evaluation and drug screening. [ABSTRACT FROM AUTHOR]

• Development of a novel red-emitting fluorescent probe (HSA) for the detection of Cys. • The probe can high sensitivity detect Cys with a low LOD. • Successfully verified the experimental results by the theoretical calculation study. • The probe can be used for exogenous Cys monitoring and endogenous Cys cell imaging experiments. Herein, we synthesized a red-emitting fluorescence turn-on probe (HSA) for specific detection of cysteine (Cys) over other biothiols (glutathione (GSH) and homocysteine (Hcy)). The acrylate group was chosen as the recognition site for specific discrimination of Cys. Absorption and emission spectra display a high selectivity towards Cys over GSH/Hcy, organic small-molecule interfering substances and anions, with a high sensitivity towards Cys (0.12 μM) in 1% ethanol-containing PBS buffer solution (25 mM, pH = 7.4). Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were conducted to clarify the luminescence mechanism of the probe. Furthermore, the probe was successfully applied to the determination of free Cys in human serum and the fluorescence imaging of endogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

Abstract A red emissive fluorescent probe 1,7-dimethyl-3,5-bis(4-methoxyphenyl-vinyl)-8-(10-n-butyl-10H-phenothiazine-3-yl)BODIPY 1,7-dimethyl-3,5-bis(4-methoxyphenyl-vinyl)-8-(10- n -butyl-10 H -phenothiazine-3-yl)BODIPY (avyl-BODIPY-PTZ) with a special orthogonal donor-acceptor structure was designed and synthesized for rapid, sensitive, and selective discrimination of ClO−, over other reactive oxygen species and anions. The probe displays a linear ratiometric absorption (A 578 /A 640) and fluorescence (F 599 /F 660) response toward ClO− with a fast response velocity (~10 s). The limit of detection (LOD) for ClO− was obtained as 22.6 nM from the fluorescence titration experiment. The fluorescence enhancement of the probe can be observed from the 32-fold enhancement in ratiometric value (F 599 /F 660) and the increasement of quantum yield from 0.01 at 660 nm to 0.28 at 599 nm. The oxidation of S atom in phenothiazine by ClO− to form the sulfoxide-type structure was proposed as the recognizing mechanism according to the Mass spectral analysis. The ratiometric enhancement of fluorescence was rationalized by the theoretical calculations. The orthogonal donor-acceptor structure according to optimized calculation and solvent effects of avyl-BODIPY-PTZ illustrated that the ClO− oxidation induced conversion from the nonradiative TICT process to the radiative LE process and caused the fluorescence ratiometric enhancement. The probe with low cytotoxity can successfully permeate into living cells and the cell images can be achieved in single channel. Moreover, after addition of ClO−, another bright red emission channel of the probe switched on and the probe displayed two-channel emission in living cells. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract Nitric oxide (NO) plays vital roles in many physiological process and is closely related to many diseases. So far, a number of fluorescent probes have been constructed for the detection of NO successfully. However, the probes still suffer from long-time reaction and limited selectivity. Herein, a fluorescent probe named dRB-OPD is synthesized and used to recognize NO. The probe contains a deoxy-rhodamine B as fluorophore and o-phenylenediamino as reaction site. dRB-OPD shows fast response to NO within 40 s with 170-fold fluorescence enhancement. Moreover, the probe shows high selectivity towards NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Particularly, the probe can avoid the serious interference from cysteine (Cys) found in the rhodamine lactam-based fluorescent NO probes (RB-OPD). In addition, the probe is applied for the detection of exogenous and endogenous NO in the HepG2 and RAW 264.7 cells with satisfactory results. Graphical abstract fx1 Highlights • A fluorescent probe named dRB-OPD is synthesized and used to recognize NO. • The probe has fast response to NO within seconds (< 40 s). • The probe shows high selectivity towards NO over DHA, AA, and MGO. • dRB-OPD can avoid the serious interference from cysteine (Cys) found in RB-OPD. • The probe is used for monitoring exogenous and endogenous NO in living cells. [ABSTRACT FROM AUTHOR]

Abstract A new fluorescent probe was designed and synthesized according to the photo-induced electron transfer theory (PET) and the results of density functional theory calculation. The synthesized probe had a larger Stokes shift (130 nm) and double emission peak in response to highly toxic thiophenols, which could be applied in rapid and high sensitive detection of thiophenol in aqueous solution. A 25-fold fluorescence intensity enhancement was achieved and the fluorescent intensity at 460 nm had a linear relationship to the thiophenol in concentration range of 0–2.0 μM. Furthermore, a remarkable detection limit (6 nM) could be achieved. 50-fold other species have no interference to the detection. The practical utility of the probe was demonstrated by live HeLa cells imaging and thiophenol detection in real water samples. In linear range of 0–2.0 μM, the probe showed good recoveries (from 95% to 108%) for thiophenol detection in natural water samples. This method possesses high sensitivity, lower detection limit and fast response (i.e., 10 min, which is shorter than the average time response of other reported methods), indicating that the synthesized probe would be promising for real-time detection of thiophenols. Graphical abstract fx1 Highlights • DFT calculations were used to design a thiophenol sensor and understand the mechanism. • A novel double emission fluorescent probe BIN-T was synthesized and characterized. • BIN-T possesses high fluorescence quantum yield and fast response to thiophenol. • The probe can be applied in thiophenol assay in real water samples and bioimaging. [ABSTRACT FROM AUTHOR]

Abstract A rhodamine hydrazone 1 bearing coumarin moiety was designed and prepared. Compound 1 exhibited high selectivity toward Co2+ and trivalent metal ions with fluorescence enhancement in CH 3 OH solution. However, 1 selectively responded to Al3+ in nearly pure H 2 O media and was further applied to monitor Al3+ in live cells. Moreover, 1 could also act as a colorimetric probe toward Cu2+ in either CH 3 OH or H 2 O solution. In addition, sensor 1 displayed aggregation-induced ratiometric emission (AIRE) activities in mixed H 2 O/CH 3 OH solution. Graphical Abstract Unlabelled Image Highlights • A rhodamine hydrazone sensor bearing coumarin moiety with aggregation induced ratiometric emission has been developed. • The sensor could detect Al3+ in H 2 O solution with fluorescence enhancement. • The sensor has been used for imaging of Al3+ in living cells. • The sensor could recognize Co2+ and trivalent metal ions based on different 'turn-on' emission. • The sensor is a colorimetric probe toward Cu2+ in either CH 3 OH or aqueous solution. [ABSTRACT FROM AUTHOR]

A new "turn-on" fluorescent probe Py based on rhodamine and piperonaldehyde was designed and synthesized for detecting Fe3+ in cells. The free probe Py was non-fluorescent. While only upon addition of Fe3+, the significant increase of the fluorescence and color were observed which could be visible directly by "naked-eye". The probe Py shows high selectivity and sensitivity for Fe3+ over other common metal ions in EtOH-H2O (3/2, v/v) mixed solution. The association constant and the detection limit were calculated to be 4.81 × 104 M−1 and 1.18 × 10−8 mol/L respectively. The introduction of piperonaldehyde unit could increase probe rigidity which could enhance its optical properties. Meanwhile, the binding mode between Py and Fe3+ was found to be a 1:1 complex formation. The density functional theory (DFT) calculations were performed which would further confirm the recognition mechanism between probe Py and Fe3+. In addition, the probe has been proved to be reversible for detecting Fe3+. Moreover, the probe Py was used to detect Fe3+ in cells successfully. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new ESIPT-based fluorescent probe for Hg2+ has been designed and developed. • The probe exhibits high sensitivity for mercury ions in aqueous solution. • The probe was successfully used for fluorescence imaging of Hg2+ in live cells. Abstract A new Excited-State Intramolecular Proton Transfer (ESIPT) based fluorescent probe for the detection of Hg2+ has been rationally designed and developed. Based on the specific reactivity of mercury-promoted hydrolysis, the probe exhibits high selectivity and sensitivity for mercury ions in almost pure aqueous solution (containing only 1% DMSO) with a low detection limit of 1.9 ppb. Furthermore, the probe was also successfully used for fluorescence imaging of Hg2+ in live cells. [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]

Abstract Hydrogen sulfide (H 2 S) can undergo dual nucleophilic reaction, which is a wise and effective way to distinguish biothiols and H 2 S. A novel H 2 S fluorescence probe, 4-{2-[4-(2-disulfide pyridyl-benzoyloxy)-phenyl]-vinyl}-1-methyl-pyridinium[ e ]iodide (DSPBP), with two nucleophilic reaction sites has been developed. The spectra results showed that DSPBP could detect H 2 S in ratiometric and colorimetric signals and has excellent selectivity and sensitivity. The fluorescence ratiometric signals (F 520 /F 450) displayed a prominent increase from 0.74 to 7.08, the fluorescence color turned to yellow form blue simultaneously. The linear range was 2–14 μM and its detection limit was 25.7 nM. Moreover, the biocompatibility of DSPBP was fine and its toxicity was very low. It has been successfully used for imaging H 2 S in cells. Graphical Abstract Unlabelled Image Highlights • A ratiometric fluorescence probe (DSPBP) for H 2 S with bis-nucleophilic center was developed. • DSPBP showed rapid response time, high selectivity and sensitivity for H 2 S over biothiol. • DSPBP would used to detect H 2 S in living cells. [ABSTRACT FROM AUTHOR]

Abstract We reported a novel and readily synthesized fluorescent "turn-on" probe L (Dansyl-Glu-Pro-Gly-Cys) based on dansyl group combine tetrapeptide. The probe L exhibited highly sensitive fluorescent recognition to Cd2+ ions in HEPES buffer solutions (10.0 mM, pH 7.4). The 2:1 binding stoichiometry of L with Cd2+ were determined based on fluorescence titration and the Job's plot investigation. The competitive experiments were found to be highly selective for the Cd2+ ions even in the existence of excess competing metal ions including Zn2+, Pb2+, Hg2+ and Cu2+ ions. The binding constant of the complex L -Cd was calculated to be 5.18 × 1010 M−2, and showed great affinity compared to other probes. In addition, the detection limit of the probe L for Cd2+ ions was calculated to be 45 nM, which presented a pronounced sensitivity toward Cd2+ ions. Most importantly, the probe L had wide range of pH and good biocompatibility, and were successfully applied to selectively detected Cd2+ ions within pH range of 7–12 and bioimaging studies in live cells. Graphical Abstract Unlabelled Image Highlights • A novel fluorescent peptide-based probe (L) was synthesized. • L exhibited exclusively selective fluorescent "turn-on" response toward Cd2+ ions. • L displayed high sensitivity for Cd(II) with a low detection limit of 45 nM. • L could serve as a potential probe to detect Cd2+ ions in 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]

Abstract Hydrogen sulfide (H 2 S) is a signaling gasotransmitter that plays an important role in modulating the functions of different systems. We have reported a xanthene-based colorimetric and fluorescence Probe A for the selective detection of H 2 S over other sulfide-containing analytes. The emission intensity increases linearly with NaSH concentrations in the low concentration range suggested that it shows high sensitivity toward H 2 S with a detection limit as low as 7 nM. This probe exhibits an enhanced up to 250-fold fluorescence enhancement at λ em 510 nm in the presence of H 2 S (50 μΜ). In addition, Probe A can be applied for fluorescent imaging of H 2 S in living cells, providing a potentially powerful molecular imaging tool for imaging H 2 S. Graphical abstract A new xanthene-based colorimetric and fluorescence Probe A for the selective detection of H 2 S. fx1 [ABSTRACT FROM AUTHOR]

Singlet oxygen plays an important role in cancer chemotherapy and biology of reactive oxygen species. In recent years, there are some reports of selective fluorescent probes for detection and imaging of singlet oxygen but the existing probes have some major drawbacks including complicated synthetic routes, poor fluorescence enhancement effects. We report herein that anthracenylmethyl modified non-fluorescent derivatives of fluorescein and rhodamine-6G can reacts with 1 O 2 , which resulted in C C bond cleavage that detach anthracene unit from the fluorophores resulting in strong fluorescence enhancement. These probes exhibit high selectivity and sensitivity in detection and imaging of 1 O 2 in chemical and in living cells. Our approach makes it simple and flexible for development of reaction-based 1 O 2 fluorescent probes for broad application in chemical, biomedical, and environmental sciences. [ABSTRACT FROM AUTHOR]

Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are interconnected and play essential roles in many biological processes. It is significant importance to detect these thiols for investigating their functions in cells and disease diagnosis. In this work, we have designed and synthesized two novel BODIPY-based turn-on fluorescent probes ( BDP-Ph and BDP-R-Ph ) carrying 4-methoxythiophenol moiety at meso position as good leaving group for highly selective detection of Cys and Hcy. Furthermore, the probes have been successfully applied to detect intracellular Cys and Hcy by fluorescent imaging in living cells. [ABSTRACT FROM AUTHOR]

A novel dual site controlled probe has been developed on the basis of rhodamine and biphenylcarbonitrile unit. The probe showed not only rapid fluorescence response to pH, but also good colorimetric recognition performance for copper ions in the HEPES buffer solution (pH 7.0). The optimal geometric configuration of the probe RhB-H with different structures and the [RhB-H-Cu 2+ ] complex were calculated at B3LYP level by DFT method. On this basis, the response mechanism of pH was analysed combining with the 1 H NMR titration experiment. Moreover, the cytotoxicity studies indicated that the probe had good biocompatibility and low toxicity. Then the probe was also successfully applied on real-time monitoring of the intracellular pH changes by exhibiting different fluorescence and emission intensity. These results demonstrated that the probe could be usefully involved in biological and biomedical research. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are critical cellular organelles associated with various physiological processes in eukaryotic cells. To visualize LDs and research their complex physiological functions, various fluorescence imaging models including the confocal imaging, the lambda scan imaging and the stimulated emission depletion (STED) super-resolution imaging have been successfully employed in recent years. However, since different fluorescence imaging models have different requirements for fluorescent probes, it is very challenging to employ single fluorescent probe for multimodal fluorescence imaging. Herein, an advanced organic fluorescent probe Lipi-DSBOMe has been sophisticatedly developed for purpose. Featuring with the advantages of high staining selectivity towards LDs, polarity sensitive luminescence, high photostability and low STED saturation intensity, this fluorescent probe is well suited for multimodal fluorescence imaging. For instance, employed with this probe for three-dimensional (3D) confocal imaging to quantitatively determine the change of number of LDs under the oleic acid stimulation, lambda scan imaging to precisely measure the polarity of LDs in different types of cells, and STED imaging to measure the size of LDs with the state-of-the-art resolution (42 nm). In overall, employing this single fluorescent probe for multimodal fluorescence imaging has allowed to provide abundant information about LDs, thus effectively promoting the LDs biology studies. [Display omitted] • An advanced fluorescent probe was developed for multimodal imaging of LD. • Abundant information about LD could be provided by multimodal fluorescence imaging. • The highest resolution (42 nm) of LD was achieved in STED super-resolution imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Near-infrared "turn-on" H 2 S fluorescence probe NIR-H 2 S constructed by novel fluorophore dye NIR-OH , excited at 686 nm and emitted at 736 nm. • Easily acquisitive (3 steps synthesis), Naked-eye visible colour change (from purple to green), high selectivity, high sensitivity (0.353 μM H 2 S), satisfactory response and low cytotoxicity. • Successfully imaged exogenous and endogenous H 2 S in living cells. Hydrogen sulfide (H 2 S) plays a substantial role as a messenger in the physiological and pathological processes of many diseases. Recently, the fluorescence probe of H 2 S based on organic dye has attracted great attention. However, the emission of many probes is in the UV–vis region (400–600 nm), so it has the disadvantages of shallow tissue penetration and more vulnerable to spontaneous fluorescence interference. Although several H 2 S probes have been developed that emit more than 650 nm, there is a complex structure difficult to synthesize or unstable in storage. Aimed at simply structural and easily synthesized H 2 S fluorescent probes with emission wavelength more than 650 nm, a novel near-infrared (NIR) probe (NIR-H 2 S) here was rationally designed with 4-(2-carboxyphenyl)-7-(diethylamino)-2-(4-hydroxystyryl)chromenylium (NIR-OH) as a fluorescent dye and 2,4-dinitrophenyl moiety as a recognition group. Addition of H 2 S, the "turn-on" NIR fluorescence response at 736 nm of NIR-H 2 S was displayed, accompanied by a visual colour change from purple to green when excited at 686 nm. As an easily acquisitive H 2 S probe, NIR-H 2 S has been successfully applied to cell imaging for H 2 S detection with the advantages such as long fluorescence emission, low toxicity, high sensitivity and strong selectivity. [ABSTRACT FROM AUTHOR]

A new chromene pyrazoline derivatives fluorescent probe L was designed and synthesized. The probe L appears in a 55-fold fluorescence enhancement after 5 equiv. Zn 2+ was added, and it also exhibits high sensitivity and selectivity for response to Zn 2+ in ethanol-water (V:V = 1:1) solution through “OFF-ON” type process and a possible photoinduced electron transfer (PET). Notably, the probe L distinguishes between Zn 2+ and Cd 2+ . The association constant was considered as 2.38 × 10 3  M −1 via fluorescence titration experiments. The probe L-Zn 2+ complex forms a 1:1 binding stoichiometry which was discussed by Job’s plot. The probe is very highly sensitive with fluorometric detection limit of 1.603 × 10 −10  M. It also shows good reversibility upon addition of EDTA. Furthermore, the viability of L to Zn 2+ has practical application in live cell imaging. [ABSTRACT FROM AUTHOR]

An imidazo[1,5-α]pyridine-based fluorescence probe NIPY-DNP with a large Stokes shift (193 nm) has been successfully developed for highly selective, sensitive and rapid detection of H 2 S. The selective deprotection of 2,4-dinitrophenyl ether group of NIPY-DNP by H 2 S led to a dramatic fluorescent enhancement (273-fold) at 505 nm within 5 min in PBS buffer solution. The sensing mechanism is proposed on the basis of the thiolysis reaction by H 2 S, which has been confirmed by HPLC and HRMS. The detection limit is 0.36 μM, which is superior to the other reported H 2 S probes. Additionally, cell imaging studies demonstrated that NIPY-DNP could be used to visualize H 2 S in living cells. [ABSTRACT FROM AUTHOR]

An imidazo [1,5-α]pyridine-based fluorescent probe MIPY-DNP with a large Stokes shift (173 nm) for the sensing of thiophenols in aqueous medium has been developed. This probe with 2,4-dinitrophenyl ether as a highly thiophenol-selective group was constructed based on the combination of PET and ESIPT mechanisms. Upon the treatment with thiophenols, MIPY-DNP produced a remarkable fluorescence enhancement (209-fold) at 478 nm. The detect limit for thiophenols was calculated to be as low as 5.6 nM. Importantly, the practical utility of MIPY-DNP for the selective detection of thiophenols has been successfully demonstrated in both real water samples and living cells. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe 1 based on acridine orange was developed for the selective detection and bioimaging of biothiols. The probe exhibits higher selectivity and turn-on fluorescence response to cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) than to other amino acids. Importantly, the probe responds to GSH and Cys/Hcy with distinct fluorescence emissions in PBS buffer at pH of 7.4. The Cys/Hcy-triggered tandem S N Ar-rearrangement reaction and GSH-induced S N Ar reaction with the probe led to the corresponding amino-acridinium and thio-acridinium dyes, respectively, which can discriminate GSH from Cys/Hcy through different emission channels. Interestingly, Cys finishes the tandem reaction with the probe and subsequently forms amino-acridinium and Hcy/GSH induces S N Ar reaction with the probe to form thio-acridiniums at weakly acidic conditions (pH 6.0), enabling Cys to be discriminated from Hcy/GSH at different emissions. Finally, we demonstrated that probe 1 can selectively probe GSH over Cys and Hcy or Cys over GSH and Hcy in HeLa cells through multicolor imaging. [ABSTRACT FROM AUTHOR]

A fluorescent probe targeting the ERBB2 receptor tyrosine was designed, synthesized and evaluated as reporter of ERBB2 dynamics in overexpressing BT474, i.e. Her2(+), cells. Two cyanoquinazoline ( CQ ) probes modeled after type-I ( CQ1 ) or active state and type-II ( CQ2 ) or inactive state inhibitors were designed and synthesized with extended π systems that impart binding-induced, turn-on fluorescence. Solution spectroscopy revealed that CQ1 exhibited attractive photophysical properties and displayed turn-on emission in the presence of purified, soluble ERBB2 kinase domain, while CQ2 was found to be non-emissive, likely due to quenching via a photoinduced electron transfer mechanism. Live cell imaging with CQ1 revealed that this probe targeted an intracellular population of ERBB2, which increased following treatment with type-I inhibitors, gefinitib and canertinib, but showed no response to type-II inhibitors. CQ1 thus provides a novel means of imaging the dynamic response of ERBB2(+) cells to kinase inhibitors. [ABSTRACT FROM AUTHOR]

A new benzothizole-based fluorescent probe 1 for Hg 2+ recognition utilizing “ESIPT+AIE” strategy has been developed. In THF/H 2 O (1:1, v/v, PBS 20 mM, pH = 8.5) mixed solution, probe 1 displays rapid fluorescence responses to Hg 2+ ions with high selectivity and sensitivity through Hg 2+ -triggered releasing of a compound possessing “ESIPT+AIE” characteristics. Cell imaging investigations indicate that probe 1 is cell permeable with low toxicity to MCF-7 cells, and applicable to detect Hg 2+ ions in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

One-pot synthesis of N -CDs was applied as a highly efficient "ON-OFF-ON" fluorescent probe for the rapid detection of CAL and l -Arg/ l -Lys in living cells. As a consequence, these N -CDs as a powerful analysis tool displayed more prominent and influential ability in real-time monitoring CAL and l -Arg/ l -Lys, and might offer a new opportunity for exploring the physiological and pathological processes of amino acid metabolism diseases. [Display omitted] • The nitrogen-doped carbon dots (N -CDs) were synthesized via a simple one-step hydrothermal method. • These CDs could rapidly and selectively detect CAL and l -Arg/ l -Lys with the detection limits as low as 58 nM, 18 nM/16 nM, respectively. • The N -CDs as a fluorescent probe displayed low toxicity and were suitable for sensing CAL and l -Arg/ l -Lys in living cells. The disorder of amino acid metabolism and the abuse of small molecule drugs pose serious threats to public health. However, due to the limitations of existing detection technologies in sensing cinnamaldehyde (CAL) and l -Arginine/ l -Lysine (l -Arg/ l -Lys), there is an urgent need to develop new sensing strategies to meet the severe challenges currently facing. Herein, nitrogen-doped carbon dots (N -CDs) were developed using a simple one-pot hydrothermal carbonization method. These N -CDs exhibited numerous distinctive characteristics such as excellent photoluminescence, high water dispersibility, favorable biocompatibility, and superior chemical inertness. Strikingly, the as-prepared CDs as a highly efficient fluorescent probe possessed significant sensitivity and selectivity toward CAL and l -Arg/ l -Lys over other analytes with a low detection limit of 58 nM and 16 nM/18 nM, respectively. The fluorescence of N -CDs could be quenched by CAL through an electron transfer process. Then, the strong electrostatic interaction between l -Arg/ l -Lys and N -CDs induced the efficient fluorescence recovery. More importantly, the outstanding biosafety and excellent analyte-responsive fluorescence characteristics of N -CDs have also been verified in living cells as well as in serum and urine. Overall, the N -CDs had a wide application prospect in the diagnosis of amino acid metabolic diseases and small molecule drug sensing. [ABSTRACT FROM AUTHOR]