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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]

A one-pot, three-component reaction between isatoic anhydride, 1,3-diketones, and amines/arylhydrazines catalyzed by a combination of molecular I2 and Et3N in open-air affords a series of quinazolin-4(3H)-one derivatives in good yield. The protocol offers an operationally simple, facile, and cost-effective pathway utilizing easily accessible reagents under mild reaction conditions with significant substrate scope. The results of steady state and time-resolved absorption and emission spectroscopy indicate the potential of quinazolin-4(3H)-one derivatives as a fluorescence probe. They exhibit unique photophysical responses in different solvent environments. In addition, they can also act as FRET acceptors during interaction with protein lysozyme. Preliminary biological studies indicate that quinazolin-4(3H)-ones are cell permeable and can be used as a fluorescent probe for bio-imaging of human cervical cancer (HeLa) 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]

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74−, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30 μM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging. [ABSTRACT FROM AUTHOR]

Nitroreductase (NTR) has the ability to activate nitro group-containing prodrugs and decompose explosives; thus, the evaluation of NTR activity is specifically important in pharmaceutical and environmental areas. Numerous studies have verified effective fluorescent methods to detect and image NTR activity; however, near-infrared (NIR) fluorescence probes for biological applications are lacking. Thus, in this study, we synthesized novel NIR probes (NIR-HCy-NO2 1–3) by introducing a nitro group to the hemicyanine skeleton to obtain fluorescence images of NTR activity. Additionally, this study was also designed to propose a different water solubility and investigate the catalytic efficiency of NTR. NIR-HCy-NO2 inherently exhibited a low fluorescence background due to the interference of intramolecular charge transfer (ICT) by the nitro group. The conversion from the nitro to amine group by NTR induced a change in the absorbance spectra and lead to the intense enhancement of the fluorescence spectra. When assessing the catalytic efficiency and the limit of detection (LOD), including NTR activity imaging, it was demonstrated that NIR-HCy-NO2 1 was superior to the other two probes. Moreover, we found that NIR-HCy-NO2 1 reacted with type I mitochondrial NTR in live cell imaging. Conclusively, NIR-HCy-NO2 demonstrated a great potential for application in various NTR-related fields, including NTR activity for cell imaging in vivo. [ABSTRACT FROM AUTHOR]

Tyrosinase (TYR), an important biomarker for melanoma, offered significant information early detection of melanoma and may decrease the likelihood of mortality. Therefore, this article constructed a highly sensitive and selective green fluorescent functionalized carbon quantum dots (TYR-CQDs) for tyrosinase (TYR) activity detection by one-step hydrothermal protocol utilizing catechol, citric acid and urea as precursors. The prepared TYR-CQDs illustrated excellent linear relationship and broad linear range with a low detection limit, which exhibited high accuracy and recovery in quantitative determination of TYR in human serum samples. Furthermore, the TYR-CQDs had successfully realized intracellular TYR detection owing to excellent biocompatibility, high anti-interference ability and good cellular imaging capability, suggesting the potential biomedical applications in early diagnosis of melanoma and other tyrosinase-related diseases. [ABSTRACT FROM AUTHOR]

Biothiols, including glutathione (GSH), homocysteine (Hcy) and cysteine (Cys), play crucial roles in various physiological processes. Though an array of fluorescent probes have been designed to visualize biothiols in living organisms, few one-for-all imaging agents for sensing biothiols with fluorescence and photoacoustic imaging capabilities have been reported, since instructions for synchronously enabling and balancing every optical imaging efficacy are deficient. Herein, a new near-infrared thioxanthene-hemicyanine dye (Cy-DNBS) has been constructed for fluorescence and photoacoustic imaging of biothiols in vitro and in vivo. Upon treatment with biothiols, the absorption peak of Cy-DNBS shifted from 592 nm to 726 nm, resulting in a strong NIR absorption as well as a subsequent turn-on PA signal. Meanwhile, the fluorescence intensity increased instantaneously at 762 nm. Then, Cy-DNBS was successfully utilized for imaging endogenous and exogenous biothiols in HepG2 cells and mice. In particular, Cy-DNBS was employed for tracking biothiols upregulation in the liver of mice triggered by S-adenosyl methionine by means of fluorescent and photoacoustic imaging methods. We expect that Cy-DNBS serves as an appealing candidate for deciphering biothiols-related physiological and pathological processes. [ABSTRACT FROM AUTHOR]

In vivo selective fluorescence imaging of carboxylesterase 2 (CES2) remains a great challenge because existing fluorescence probes can potentially suffer from interference by other hydrolases. In addition, some fluorescent probes that have been separately reported for measuring CES2 activity in vitro are affected by autofluorescence and absorption of the biological matrix due to their limited emission wavelength or short Stokes shift. Herein, based on the substrate preference and catalytic performance of CES2, a novel and NIR fluorescent probe was developed, in which a hemi-cyanine dye ester derivative was used as the basic fluorescent group. In the presence of CES2, the probe was hydrolyzed to expose the fluorophore CZX-OH (λabs ∼ 675 nm, λem ∼ 850 nm), which led to a notable red-shift in the fluorescence (∼175 nm) spectrum. Confocal imaging of cells and live mice demonstrated that the fluorescent signal of this probe was related to the real activities of CES2 in cancer cells. All these results will powerfully promote the screening of CES2 regulators and the analysis of CES2-related physiological and pathological processes. [ABSTRACT FROM AUTHOR]

A simple multifunctional Schiff base fluorescence probe (E)-N′-(2,4-dihydroxybenzylidene)-2-hydroxybenzohydrazide (NDH) was designed and synthesized by the reaction of 2,4-dihydroxybenzaldehyde and salicylhydrazide. NDH acts as a "off–on" logic gate fluorescence probe for Al3+, Zn2+ and La3+ ions, providing different colors and detection limits of 1.22 μM, 2.47 μM and 2.94 μM, respectively. Moreover, the binding stoichiometry of NDH to Zn2+ was 2:1, but to other metal ions was 1:1, and was confirmed by Job' plot, 1H NMR and ESI–MS. Furthermore, the probe NDH was applied to detect Al3+, Zn2+ and La3+ ions in real water samples and Hela cells. This work might provide a new evidence that the fluorescent probe with "off–on" logic gate can serve as an economical and efficient strategy for simultaneous sensing multiple metal ions. A novel, highly sensitive and selective fluorescent probe was developed to trace Al3+, Zn2+ and La3+ in real water samples and live cells. [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]

A novel fluorescence probe for the detection of Al3+ was developed based on methionine protected gold nanoclusters (Met-AuNCs). A fluorescent Schiff base (an aldimine) is formed between the aldehyde group of salicylaldehyde (SA) and the amino groups of Met on the AuNCs, and developed for selective detection of Al3+ in aqueous solution. Al3+ can strongly bind with the Schiff base ligands, accompanied by the blue-shift and an obvious fluorescence emission enhancement at 455 nm. The limits of detection (LODs) of the probe are 2 pmol L−1 for Al3+. Moreover, the probe can successfully be used in fluorescence imaging of Al3+ in living cells (SHSY5Y cells), suggesting that the simple fluorescent probe has great potential use in biological imaging. [ABSTRACT FROM AUTHOR]

Fluorescent probes are intriguing material for ion detection. In this study, 4,4-difluoro-4-bora3a,4a-diaza-s-indacene (BODIPY) containing a dipicolylethylenediamine unit was developed as a colorimetric and fluorescence "turn-off" probe for Cu2+. The probe exhibited higher selectivity for Cu2+ than other common metal ions with a detection limit of 8.49 μM. With increasing Cu2+ concentration, the probe showed a red-shift in the absorption spectrum as well as fluorescence quenching, possibly due to the intramolecular charge transfer effect of the probe–Cu(II) complex. Furthermore, the probe was used for imaging Cu2+ in living cells based on confocal fluorescence imaging. The results show that the probe is an effective tool for detection copper ions. [ABSTRACT FROM AUTHOR]

A novel ratiometric fluorescent probe HB‐2 based on benzothiazole for hypobromous acid (HBrO) was synthesized and studied. After HBrO was added to the CH3CN‐HEPES solution of the HB‐2, the probe cyclized to form a sulfimine bond, which increased the conjugated degree of the system. The fluorescence emission peak of the reaction system at 447 nm gradually decreased, while the newly generated emission peaks gradually increased at 580 nm. The ratio of the fluorescence intensity at the two wavelengths of 447 nm and 580 nm increased about 234 times. Moreover, it has successfully been used to stain and record microscopy images of 4T1 cells, and the presence of exogenous HBrO could be judged by the change of fluorescence intensity. [ABSTRACT FROM AUTHOR]

In this paper, intrinsic dual-emission fluorescent carbon dots (CDs) doped with N and S atoms have been firstly fabricated. The characterization results show that CDs are successfully synthesized with two separate fluorescence emissions at 468 nm and 628 nm, respectively. The strong and selective interaction of Cr (VI) ions with CDs lead to obvious fluorescence decrease of CDs at 468 nm, which is caused by a mixed quenching mechanism. At the same time, the fluorescence at 628 nm increase. Interestingly, the CDs solution show obvious color change under the daylight and UV light, so visualization detection of Cr (VI) can be realized in water samples. Based on the data of the emission intensity ratios of F468/F628, Cr (VI) can be detected from 3.8 to 38.9 μM combined with the linear correlation coefficient of 0.998, and the lowest detection concentration is 47.2 nM. The platform is satisfactorily applied to the detection of Cr (VI) ions in water samples. In addition, the CDs could be applied as fluorescent probes for cell imaging with dual fluorescent emission. [ABSTRACT FROM AUTHOR]

For ratiometrically imaging peroxynitrite (ONOO−) in living cells, we devised and fabricated a novel fluorescent nanoprobe, NC-NP530/460, in this study. To achieve ratiometric fluorescence response towards ONOO−, NC-NP530/460 used 3-(2-benzothiazolyl) coumarin (Cou-Bz) as the internal reference and 1,8-naphthimide derivative (Naph-PN) as a fluorescent ONOO− probe. These compounds were incorporated into an amphiphilic block polymer called Pluronic F-127. In addition to an ultrafast response to ONOO−, NC-NP530/460 also showed great selectivity and sensitive detection (detection limit was 4.51 μM). It was important to note that NC-NP530/460 demonstrated solid performance for ONOO− fluorescence ratio imaging in living cells, highlighting its potential for ONOO−-related chemical biology research. [ABSTRACT FROM AUTHOR]

Mitochondrial viscosity and mitochondrial membrane potential (MMP) are vital parameters for reflecting mitochondrial conditions and they are closely correlative in various biological events. Accordingly, simultaneous detection of mitochondrial viscosity and MMP is imperative for elucidating their interactions, further exploring the mechanism of diseases, and investigating numerous pathological procedures. However, such profound research remains a big challenge due to the lack of high-performing single fluorescent probes capable of simultaneously visualizing of these two parameters. In this study, we developed a new kind of fluorescent carbon dots (CDs) that can successfully realize simultaneous monitoring of mitochondrial viscosity and MMP in living cells. The fluorescence of CDs can be specifically turned on as the viscosity of solvents increases from 0.89 to 945 cP. Meanwhile, the CDs accumulate in mitochondria under normal MMP conditions, switch to exist in both mitochondria and nucleoli under reduced MMP, and present only in nucleoli with the vanishment of MMP. Thus, various MMP situations can be easily differentiated through the changed spatial distributions of CDs. More importantly, based on the developed CDs, an increased mitochondrial viscosity accompanying a decreased MMP was simultaneously tracked in drug-stimulated cells. We envision that the developed CDs has a great potential to be utilized as a promising fluorescent probe for mitochondrion-related biology studies. The carbon dots were elaborately designed for simultaneous determination of mitochondrial viscosity and membrane potential through their fluorescence variation and location migration from mitochondria to nucleoli. [Display omitted] • The fluorescence of Carbon Dots (CDs) was specifically turned on as the viscosity of solvents increased. • Fluctuation of mitochondrial membrane potential was visualized through migration of CDs from mitochondria to nucleoli. • An increased mitochondrial viscosity accompanying a decreased membrane potential was simultaneously monitored in cells. [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]

Reactive oxygen species (ROS), a class of reactive oxidants, play critical roles in signal transduction, cell metabolism, immune defense, and other physiological processes. Abnormally excessive levels of ROS can cause diseases and thus, investigations into the relevant biology and medicine are significant. The behavior of ROS in inflammation has been rarely elucidated. In this work, two ROS fluorescent probes, FS-ROS1 and FS-ROS2 have been designed and synthesized. FS-ROS1 responds rapidly (~1 min) to ClO– and gradually (~30 min) to H2 O2 with an increase in fluorescence at ~656 nm and 640 nm of more than 100-fold in vitro. At a concentration of 10 μM, FS-ROS1 labels the L929 cell and Raw264.7 cell wells in 30 min with excellent biocompatibility and without washing. After labelling, FS-ROS1 exhibited a rational fluorescence increase upon the addition of 1, 10, 100, and 200 μM of H2 O2. Based on these results, inflammatory cells, stimulated with 800 nM dexamethasone and polyIC, showed a higher increase in fluorescence than the control cells. These results suggest that H2 O2 and ClO– might be important signaling molecules during inflammations. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS), a class of reactive oxidants, play critical roles in signal transduction, cell metabolism, immune defense, and other physiological processes. Abnormally excessive levels of ROS can cause diseases and thus, investigations into the relevant biology and medicine are significant. The behavior of ROS in inflammation has been rarely elucidated. In this work, two ROS fluorescent probes, FS-ROS1 and FS-ROS2 have been designed and synthesized. FS-ROS1 responds rapidly (~1 min) to ClO– and gradually (~30 min) to H2 O2 with an increase in fluorescence at ~656 nm and 640 nm of more than 100-fold in vitro. At a concentration of 10 μM, FS-ROS1 labels the L929 cell and Raw264.7 cell wells in 30 min with excellent biocompatibility and without washing. After labelling, FS-ROS1 exhibited a rational fluorescence increase upon the addition of 1, 10, 100, and 200 μM of H2 O2. Based on these results, inflammatory cells, stimulated with 800 nM dexamethasone and polyIC, showed a higher increase in fluorescence than the control cells. These results suggest that H2 O2 and ClO– might be important signaling molecules during inflammations. [ABSTRACT FROM AUTHOR]

The hybrid microgels of carbon dots (CDs) and gold nanoclusters (AuNCs) have been prepared with precipitation polymerization. This hybrid microgels exhibited dual emissions thanks to organic integration of CDs and AuNCs for their unique fluorescence properties maintained in the microgel system. The fluorescence intensity ratio at 570 nm and 450 nm of the dual-emitting has a good linear response to temperature varying at the range of 20–50 °C. In addition, the ratio of the dual emissions intensity of the hybrid microgel shows well linear relationship at pH range between 9.0 and 11.0, which promises to be used as pH sensor. Furthermore, this hybrid microgel is inherently non-cytotoxic, which could be used as high efficient fluorescent probes in living cell with dual colors. Thus, this novel dual-emission hybrid microgel system can be used not only as a multifunctional sensor, but also to expand potential applications in biomedical engineering. [ABSTRACT FROM AUTHOR]

We developed a dual-responsive fluorescent probe MC-V-P for the simultaneous detection of ONOO− and viscosity by different imaging channels. MC-V-P has high sensitivity and selectivity, and shows good stability at different pH levels. Notably, the probe has two independent fluorescence signals toward ONOO− and viscosity changes at 580 nm and 740 nm, respectively. Cell imaging experiment results demonstrated that MC-V-P exhibits low cytotoxicity and could be used to monitor viscosity and ONOO− in living HepG2 cells simultaneously. [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]

Carbon dots (CDs) are a strong alternative to conventional fluorescent probes for cell imaging due to their brightness, photostability, tunable fluorescence emission, low toxicity, inexpensive preparation, and chemical diversity. Improving the targeting efficiency by modulation of the surface functional groups and understanding the mechanisms of targeted imaging are the most challenging issues in cell imaging by CDs. Firstly, we briefly discuss important features of fluorescent CDs for live-cell imaging application in this review. Then, the newest modulated CDs for targeted live-cell imaging of whole-cell, cell organelles, pH, ions, small molecules, and proteins are elaborately discussed, and their challenges in these fields are explained. [ABSTRACT FROM AUTHOR]

A fluorescent probe II, 6-azido-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione with specific identification environment H2S, was designed and synthesized based on 4-bromine-1,8-naphthalimide and ethanamine. We used 4-bromine-1,8-naphthimide as raw materials to synthesize a new type of reactive fluorescent probe based on the mechanism of intramolecular charge transfer. These two materials are easily obtainable, low in cost, and can be synthesized through a simple two-step reaction. 1,8-Naphthalene anhydride has a moderate fluorescent ability as it introduces an electron-donating group at position 4. A change to its conjugate system can cause a push-pull electronic effect in the molecule and result in a very strong luminous effect. The structure of probe II was characterized by IR, ESI, and NMR. The preliminary screening was under the UV lamp. We found that probe II had a certain specific recognition effect on H2S in the DMSO solvent. After the solvent screening, DMSO was selected as a solvent to identify H2S specifically for the probe. The fluorescence spectroscopy illustrated that probe II showed green fluorescence in the DMSO solution. With the continuous addition of H2S, probe II showed red fluorescence at 510 nm, which produced a strong fluorescence emission peak that stood out from the rest of the spectrum. The experimental results showed that the probe had a very good sensitivity at detecting H2S (with a minimum concentration of 1 × 10–7 mol/L). Meanwhile, dozens of cations and anions do not interfere with the recognition of H2S by the probe molecule in the DMSO system. At the same time, we found that probe II could also recognize H2S by cell imaging technology. [ABSTRACT FROM AUTHOR]

Selective detection of H2S in the cellular systems using fluorescent CPs/MOFs is of great scientific interest due to their outstanding aqueous stability, biocompatibility and real‐time detection ability. Fabrication of such materials using complete biologically essential elements and applying them as an efficient biosensor is still quite challenging. In this context, two newly synthesized CPs containing biologically essential metal ion (Zn) and nitro/azido functional groups into the framework to sense extracellular and intracellular H2S by reducing into respective amines are presented. The CP‐1 containing the azide group acted as an efficient fluorescent turn‐on probe with the lowest detection limit (7.2 μM) and shortest response time (30 s) among the Zn‐based probes reported till date. Moreover, CP‐1 exhibited green luminescence in live cells after imaging a very low concentration of H2S, whereas the nitro analogue CP‐2 could not detect the target analyte due to its framework disruption. [ABSTRACT FROM AUTHOR]

β-Galactosidase (β-gal), an enzyme related to cell wall degradation, plays an important role in regulating cell wall metabolism and reconstruction. However, activatable fluorescence probes for the detection and imaging of β-gal fluctuations in plants have been less exploited. Herein, we report an activatable fluorescent probe based on intramolecular charge transfer (ICT), benzothiazole coumarin-bearing β-galactoside (BC-βgal), to achieve distinct in situ imaging of β-gal in plant cells. It exhibits high sensitivity and selectivity to β-gal with a fast response (8 min). BC-βgal can be used to efficiently detect the alternations of intracellular β-gal levels in cabbage root cells with considerable imaging integrity and imaging contrast. Significantly, BC-βgal can assess β-gal activity in cabbage roots under heavy metal stress (Cd2+, Cu2+, and Pb2+), revealing that β-gal activity is negatively correlated with the severity of heavy metal stress. Our work thus facilitates the study of β-gal biological mechanisms. [Display omitted] • An activatable fluorescence probe (BC-βgal) for detecting β-galactosidase was designed. • BC-βgal was high sensitivity and selectivity towards β-gal with fast response (8 min). • BC-βgal imaged the β-gal fluctuation in situ in cabbage roots. • BC-βgal evaluated the β-gal activity under heavy metal stress for the first time. [ABSTRACT FROM AUTHOR]

γ-Glutamyltranspeptidase (GGT) is a cell surface-associated enzyme, which has been proven to be closely related to many diseases. Thus, development of simple and effective GGT-activatable fluorescent probes for early diagnosis of diseases is of great significance. Herein, a series of simple isomeric pyridine-based GGT-activatable fluorescent probes has been successfully designed and synthesized. The preliminary experimental results indicate that Py-GGT-1 has a significant fluorescence response to GGT via a rare fluorescence-off approach. Further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, reveal that Py-GGT-1 has an excellent ability to monitor endogenous GGT activity. Mechanism studies through HRMS analysis, DFT calculations and molecular docking have theoretically verified the catalytic process between Py-GGT-1 and GGT. To develop its practical application, live-cell imaging and serum-sample analysis were carried out, demonstrating that Py-GGT-1 coud effectively track GGT within cells and organisms. Based its high selectivity and reasonable sensitivity, we expect that the probe will be applied in clinical diagnosis of GGT-related diseases in the future. • We have designed and synthesized a series of simple isomeric pyridine-based probes for GGT detection, which performed a good photophysical property and showed a rapid response to GGT. • Py-GGT-1 was selected as the optimal GGT-activatable probe based on further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, which revealed that Py-GGT-1 had an excellent ability to monitor endogenous GGT activity. • Mechanism studies through HRMS analysis, DFT calculations and molecular docking theoretically verified its catalytic process between Py-GGT-1 and GGT. • Compared with the reported GGT-activatable probes, our probe shows its simplicity, reliability and rapid response for in vitro monitoring GGT activity with high selectivity and reasonable sensitivity, which is expected to be applied in clinical diagnosis of GGT-related diseases in the future. [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]

[Display omitted] • The probe EDPH specializes in the detection of H 2 S with high selectivity, high sensitivity and good detection limits. • The probe EDPH has been shown to have applications in intracellular fluorescence imaging. • Purine-based fluorescent probes for the detection of H 2 S are a new direction. Hydrogen sulfide (H 2 S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H 2 S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H 2 S induced ether bond breakage in EDPH , resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H 2 S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H 2 S, which enabled the quantitative detection of H 2 S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H 2 S in living systems. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) plays important roles in both physiology and therapeutics. Nonetheless, the in-situ monitoring of NO release from most existing donors is challenging, inhibiting advanced research in both chemistry and biology. In this study, we introduce an innovative photochemotherapeutic agent that incorporates a nitroaniline NO moiety with an integrated pyrene fluorophore. This design enables controlled NO release upon light irradiation, allowing for precise quantification through a dramatic fluorescence enhancement (with a 3000-fold increase in intensity). Ultrafast spectroscopy data revealed that the NO release process is exceptionally rapid, completing within 13.3 ps. Additionally, the donor's fluorescence was successfully utilized for in situ cell imaging upon direct photoexcitation. Consequently, using this fluorescent probe enables the accurate visualization of NO release kinetics, dosage, and localization in real-time. The unique advantages of this NO donor are anticipated to significantly advance research in NO chemistry and biology. [Display omitted] • The first pyrene-based photoactivated NO donor was fabricated. • Photoactive ultrafast NO release (13.3 ps) was obtained. • Real-time NO-releasing was monitored by a strong fluorescent probe (3000-fold). • Cellular imaging was performed to demonstrate NO-releasing in situ. [ABSTRACT FROM AUTHOR]

The abnormally elevated expression level of glutathione (GSH) has been observed in various human cancer cells and tissue. Thus, effective methods for glutathione detection are of great importance in early diagnosis of cancer. However, many fluorescent probes for GSH detection suffer from the interference of the abundantly existent nucleophilic biomolecules in biological environment. In this work, we propose a sequential activation strategy to overcome this problem by designing and synthesizing a series of 1,3,5-triazinyl resorufin turn-on fluorescent probe (Probes 1–3). As two electrophilic sites are presented in probes, GSH sequentially reacts with the resorufin and the triazine moiety, resulting in significant fluorescence augmentation (up to 165.0-fold). Designed probes possess low limit of detection as low as 1.8 μM). Cellular fluorescent imaging has been successfully applied to selectively detect GSH in several living cells. [Display omitted] • Novel sequential activation strategy allows the Probe 1–3 to detect GSH with high selectivity. • Designed fluorescent probes exhibited strong fluorescence intensity as response. • Designed probes realized GSH visualization in multiple cells with high fidelity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mitochondria-targeting fluorescence probe NIR1 for H 2 S visualization. • NIR1 has excellent detection limits as low as 30.2 nM. • NIR1 was successfully applied for H 2 S imaging analysis in living inflammatory mice. The mechanism of the interaction between the signaling molecule hydrogen sulfide (H 2 S) and mitochondria and its related diseases is difficult to elusive. Thus it is urgent to develop effective methods and tools to visualize H 2 S in mitochondria and in vivo. In this work, a robust mitochondrial-targeting NIR fluorescence "turn-on" fluorescent probe, NIR1, was reported, by adopting a Changsha-OH near-infrared (NIR) dye as the NIR fluorophore, a 2,4-dinitrophenyl (DNB) moiety as both the responsive site of the H 2 S and the fluorescence quenching group of the NIR fluorophore, and an oxygen onium ion site as the mitochondria-targeting group, for the detection and analysis of H 2 S in living Raw 264.7 cells and drug-induced inflammatory mice models. NIR1 exhibited a much smaller background fluorescence signal in lack of H 2 S, whereas strong enhanced NIR fluorescence "turn-on" was detected in the presence of H 2 S, these results showed a low detection limit (30.2 nM) for quantitative detection of H 2 S in aqueous solutions with concentrations ranging from 0 to 1 μM H 2 S. These characteristics were beneficial to direct detection and imaging analysis of H 2 S in complicated biosystems. Therefore, first, NIR1 was applied for the NIR detection of mitochondrial H 2 S in living inflammatory cells with satisfactory results. Finally, NIR1 was applied to detect H 2 S in drug-induced inflammatory mice models with agreeable results, demonstrating that NIR1 as a molecular tool has an excellent practical application in the study of the interaction between inflammatory and H 2 S. [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]

In this work, by installing a free-rotating benzene ring to suppress the intermolecular π–π stacking effect in the aggregated state, a naphthalimide-derived hypochlorite (ClO−) fluorescent probe, Probe A, with the aggregation-caused quenching (ACQ) effect was successfully transformed into Probe B possessing typical aggregation-induced emission (AIE) characteristics. The experimental results indicated that Probe B with good selectivity and a low detection limit (LOD) of 0.02 µM can also exhibit a significant ratiometric fluorescence color change from cyan to dark blue within 2 min in a nearly pure water solvent system after the addition of ClO−. Finally, by virtue of the good photophysical properties and ClO− sensing performance, Probe B and the Probe B loaded portable test paper were successfully applied to live cell imaging and the naked eye recognition of ClO−, respectively. [ABSTRACT FROM AUTHOR]

Photo-sensitive probes based on coumarin deserve extensive attention because of their high biocompatibility, quantum yield, and stability. The synthesis of coumarin and its derivatives is mainly based on four classical methods: Perkin synthesis, Knoevenagel synthesis, Wittig synthesis, and Pechmann synthesis. As everyone knows, fluorescent probes consist of a recognition group, a bridging group, and a luminescent group. Mechanism of fluorescent probes can be roughly summarized into four models: Chelation-induced enhanced fluorescence (CHEF), intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and aggregation-induced luminescence (AIE), which can instruct the design of coumarin-based photo-sensitive probes. Since the fluorescence-based probe was first reported, probes based on coumarin have found widespread application in analytical chemistry, proving to be a selective, efficient, and convenient tool in ion monitoring, molecular monitoring, cell imaging, drug delivery, and many other fields. In this critical review, the synthetic routes of these compounds and the design for fluorescent probes were reported. Furthermore, the recent researches on the employment of coumarin in analytical chemistry were also introduced. Finally, the future research trends and application foreground of coumarin derivatives were forecasted herein. [ABSTRACT FROM AUTHOR]

A new fluorescent probe (Q-lipo) was developed by conjugating a xanthene scaffold with a quinoline moiety for activatable imaging of lipophagy. Q-lipo with acidic pH activated near infrared fluorescence and the lipid droplet targeting ability allowed activatable fluorescence imaging and flow cytometry detection of lipophagy in live cells with high contrast. It was further utilized to study the effect of tumor-microenvironment related conditions on lipophagy. Q-lipo would provide a useful tool for studying lipophagy in live cells. [ABSTRACT FROM AUTHOR]

Zinc ion is closely related to human health. Its content in human body is small, while the effect is large. However, it is not the more the better, must be in a scientific balance. Therefore, it is significant to the rapid detection of Zn2+ in the environment and organism. Herein, a fluorescent probe based on 2-hydroxy-1-naphthalene formaldehyde and furan-2-carbohydrazide was conveniently synthesized via Schiff base reaction. And this probe has been successfully applied to the accurate and quantitative detection of Zn2+ in real samples, showing turn on fluorescence, good selectivity, very low detection limit, real time response and reusability. In addition, this probe has the potential application to trace Zn2+ in living cells with low cytotoxicity. [ABSTRACT FROM AUTHOR]

Background: Ex vivo and in vivo detection and imaging of adenosine triphosphate (ATP) is critically important for the diagnosis and treatment of diseases, which still remains challenges up to present. Results: We herein demonstrate that ATP could be fluorescently detected and imaged ex vivo and in vivo. In particular, we fabricate a kind of fluorescent ATP probes, which are made of titanium carbide (TC) nanosheets modified with the ROX-tagged ATP-aptamer (TC/Apt). In the constructed TC/Apt, TC shows superior quenching efficiency against ROX (e.g., ~ 97%). While in the presence of ATP, ROX-tagged aptamer is released from TC surface, leading to the recovery of fluorescence of ROX under the 545-nm excitation. Consequently, a wide dynamic range from 1 μM to 1.5 mM ATP and a high sensitivity with a limit of detection (LOD) down to 0.2 μM ATP can be readily achieved by the prepared TC/Apt. We further demonstrate that the as-prepared TC/Apt probe is feasible for accurate discrimination of ATP in different samples including living cells, body fluids (e.g., mouse serum, mouse urine and human serum) and mouse tumor models. Conclusions: Fluorescence detection and imaging of ATP could be readily achieved in living cells, body fluids (e.g., urine and serum), as well as mouse tumor model through a new kind of fluorescent ATP nanoprobes, offering new powerful tools for the treatment of diseases related to abnormal fluctuation of ATP concentration. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al3+ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al3+ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al3+ in the range of 1–20 μmol L−1; the limit of detection (3σ) was only 0.32 μmol L−1. Furthermore, an AA-CQD probe was also utilized for detection of Al3+ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al3+ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research. [ABSTRACT FROM AUTHOR]

A new naphthalene-based boronate probe, NAB-BE , for the fluorescence-based detection of inflammatory oxidants, including peroxynitrite, hypochlorous acid, and hydrogen peroxide, is reported. The chemical reactivity and fluorescence properties of the probe and the products are described. The major, phenolic oxidation product, NAB-OH , is formed in case of all three oxidants tested. This product shows green fluorescence, with a maximum at 512 nm, and can be excited either at 340 nm or in the near infrared region (745 nm) for two-photon fluorescence imaging. Peroxynitrite is the fastest of the oxidants tested and, in addition to the phenolic product, leads to the formation of a nitrated product, NAB-NO 2 , which can serve as a fingerprint for peroxynitrite. The probe was applied to detect peroxynitrite in activated macrophages using fluorimetry and two-photon fluorescence microscopy, and both NAB-OH and NAB-NO 2 products were detected in cell extracts by liquid chromatography-mass spectrometry. The combined use of fluorometric high-throughput analyses, fluorescence imaging, and liquid chromatography-mass spectrometry-based product identification and quantitation is proposed for most comprehensive and rigorous characterization of oxidants in biological systems. [Display omitted] • Naphthalene-based boronate two-photon fluorescent probe for detection of peroxynitrite. • Peroxynitrite reacts with the probe almost a million times faster than H 2 O 2 and more than 30 times faster than HOCl. • The major, green fluorescent product formed during the reaction of NAB-BA with oxidants is NAB-OH. • Incubation of NAB-BA with macrophages activated to produce ONOO− yielded NAB-OH as well as the nitrated product, NAB-NO 2. • The probe accumulates in cells and detects oxidants in the cytosolic/extranuclear compartments. [ABSTRACT FROM AUTHOR]

Résumé: La révolution très récente de la microscopie optique, associée à l'optimisation de la résolution spatiale et de la vitesse d'observation, a ouvert l'accès à la visualisation d'objets nanométriques. Ainsi, l'utilisation d'une nouvelle génération de microscopes de super-résolution combinée à l'amélioration des marqueurs fluorescents pour les protéines ou les lipides, permet désormais d'étudier le cycle réplicatif des virus à l'échelle de la molécule unique dans des modèles cellulaires fixés, mais aussi vivants, avec une précision nanométrique. Après une brève description chronologique et technique de ces nouvelles approches, nous détaillerons dans cette revue quelques exemples de microscopies de super-résolution ayant permis de revisiter notre compréhension du cycle de réplication de certains virus affectant l'humain, dans l'étude des relations hôte-pathogènes à l'échelle du virus et de la molécule unique. The recent revolution in optical fluorescence microscopy, supported by the optimization of both spatial resolution and acquisition speed, led to the ability to visualize nano-scaled objects. Currently, the use of a new generation of super-resolution fluorescence microscopes coupled to improved fluorescent probes gives the possibility to study the replicative cycle of viruses in living cells, at the single-virus and molecule level. In this review, after a brief chronological description of these new approaches, we highlight several examples of super-resolution microscopies that have allowed to revisit our understanding of several human viruses and of host-pathogen interactions. [ABSTRACT FROM AUTHOR]

To selectively detect H2S based on the thiolysis reaction of 7-nitro-1,2,3-benzoxadiazole (NBD), amines attracted increasing attention since NBD amine is regarded as a new H2S reaction site. Herein, a novel fluorescent probe, triphenylamine piperazine NBD (TPA-Pz-NBD), was developed. The results showed that it exhibited high selectivity towards H2S via fluorescence spectroscopy and solution color. Furthermore, TPA-Pz-NBD not only detected H2S by a dual-channel, turn-on fluorescence signal at 500 nm and turn-off fluorescence signal at 545 nm, respectively, but also displayed a wide detection range of 0–125 μM. In addition, living cell imaging results indicated that TPA-Pz-NBD holds potential for the detection of intracellular H2S. [ABSTRACT FROM AUTHOR]

Fluorescent probes with outstanding physical and biological properties are superior for functional fluorescent dyes design. However, few studies pay attention to the stability of specific groups in fluorescent probes. The aldehyde group in the fluorescent probe is highly active but unstable under certain conditions. Therefore, we introduced ethoxy groups to realize the conversion to aldehyde groups under acidic conditions and avoid the instability of straightforward aldehyde groups. In this work, two fluorophores based on the multi acetal difluoroboraindacene (BODIPY) units with combination of the pharmaceutical intermediate chalcone have been firstly developed. In the design part, chalcone was introduced as a medium for fluorophore and multiple acetal. The mild synthesis strategy is based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole) and connects with chalcone in (2E,2′E)-3,3′-(1,3-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). The emission wavelengths of the products are around 530 nm with high fluorescence intensity. To highlight the biological characteristics of these novel BODIPY fluorescents, we further demonstrated biological analysis studies on MTT and flow cytometry assays. The IC50 values of BODIPY 5 ranged from 79 ± 6.11 to 63 ± 5.67 μM and BODIPY 6 were found to be 86 ± 4.07 to 58 ± 10.51 μM in tested cell lines. Flow cytometry data analysis shows that the representative agent 6 and reference have similar rational apoptosis rates in first quadrant. Last but not least, 6 shows outstanding biological compatibility and cell imaging potential in live cell imaging and in vivo assay, not only is the fluorescence prominent enough, but also rapidly distributes. Thus, our study reports a mild synthesis strategy and full biological analysis on BODIPY fluorescents, and the subtle modulation of the physical and biological properties by pharmaceutical substituents makes these designed chalcone-BODIPY-based dyes hopeful to realize drug functional fluorescent dyes. Two new highly sensitive BODIPY fluorophores are synthesized based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole), which connects with chalcone in (2E,2′E)-3,3′-(1,3/4-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). Multiple acetals were introduced and the physical and biological properties of BODIPYs are described with MTT assay and in vitro and in vivo imaging. [ABSTRACT FROM AUTHOR]

As one of the most important minerals in the body, potassium is vital for the heart and neurons. Methods that can non‐invasively and accurately monitor changes in potassium balances would benefit disease diagnoses as well as offer insight into pathologies. Among the sensing approaches, fluorescent probes serve as a unique detection method for its simplicity, tunable detection range, and bioimaging ability. The design of new probes with highly selective K+ receptors and transduction functionality remains a challenge that is motivated by numerous sensing and detection applications. In this minireview, fluoroionophores are summarized that undergo transduction, producing fluorescence signals when interacting with, e. g. potassium ions. The properties of ionophores (afford selective interaction with potassium) and fluorophores (generate signal read‐out) are discussed. Molecular structure design and sensing mechanisms are included along with cell imaging applications. The selectivity towards K+ and the absorption/emission characteristics of the probes are of particular interest. [ABSTRACT FROM AUTHOR]

Live‐cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real‐time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase‐2 (COX‐2). We developed celecoxib‐azide derivative 14, possessing favorable biophysical properties and excellent COX‐2 selectivity profile. In cellulo strain‐promoted fluorogenic click chemistry of COX‐2‐engaged compound 14 with non/weakly‐fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX‐2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein‐ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX‐2 in live cells with superior sensitivity in the visible range. [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]