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The development of bifunctional AIEgens for direct delivering and visualizing bioactive species together remains a great challenge to date. Herein, we fabricated a novel photoactivatable nitric oxide (NO) donor with a built-in AIE fluorophore, which can rapidly release NO and AIEgen upon light irradiation. The ultrafast NO generation can be obtained in 2.1 ps, with the yielding of a greatly drastic fluorescence turn-on AIEgen probe (300,000-fold intensity enhanced). Using this NO donor, real-time cell images of NO-releasing through the emission of AIEgen were successfully achieved through direct excitation of the donor in cells in situ. [Display omitted] • The first AIE-caged photoactive NO donor was developed. • Ultra-fast NO release (2.1 ps) was achieved by photoexcitation. • An extremely high fluorescence intensity was obtained (300,000-fold). • The NO release was visualized by fluorescent technology. • Cell imaging was successfully performed using this NO donor. [ABSTRACT FROM AUTHOR]

Designing functionalized MOFs with specific reactivity and NIR photoelectrochemical and fluorescent response is critical for developing biosensing systems. Herein, SCy7, a conjugate macrocycle ligand with a specific fluorescence responsive group to HClO, was designed and synthesized. Responsive Nd-MOF nanorods were successfully prepared by using SCy7 as the organic ligand and Nd3+ as the metal central ion. Nd-MOF nanorods show good absorption characteristics in the wavelength range of 200–1200 nm with a band gap of 0.89 eV. Nd-MOF nanorods were employed as a photoactive material to construct a near-infrared photoelectrochemical cytosensor for MCF-7 cells by integrated with an aptamer. The photocurrent variation exhibits a good linear response to MCF-7 cells in the concentration range of 50–1.0 × 107 cells mL−1, and a comparatively low detection limit of 18 cells mL−1 (S/N = 3). The NIR PEC cytosensor was also employed for monitoring endogenous HClO released from MCF-7 cells as being stimulated by PMA. HClO is an electron acceptor that can convert the anodic photocurrent into cathodic photocurrent, thus achieving monitoring HClO through the conversion of photocurrent polarity. Furthermore, Nd-MOF was coated with F127 to improve its hydrophilicity and biocompatibility, and to provide a Nd-MOF@F127 with a fluorescence emission peak at 830 nm. Nd-MOF@F127 show specific fluorescence response to HClO, and thus was successfully used in imaging HClO variation in cells and breast cancer bearing mice. [Display omitted] • Nd-MOF nanorods with specific response to HClO were successfully synthesized. • A NIR PEC cytosensor based on Nd-MOF was developed for MCF-7 cells assaying. • Real-time monitoring HClO was achieved by photocurrent polarity conversion. • Fluorescence imaging HClO in cells and mice was performed by using Nd-MOF@F127. [ABSTRACT FROM AUTHOR]

In this work, arginine functionalized niobium carbide MXene quantum dots (arginine-Nb 2 C MQDs) were synthesized using Nb 2 AlC, NaOH and arginine as reagents. The as-synthesized probe showed bluish-green fluorescence under UV light at 365 nm. The structural and morphological changes of as-synthesized arginine-Nb 2 C MQDs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy and high-resolution transmittance electron microscopy (HR-TEM). The synthesized fluorescent arginine-Nb 2 C MQDs were stable, with an average size of 1.92 ± 0.52 nm. As-synthesized arginine-Nb 2 C MQDs act as a sensor for detecting superoxide anion (O 2 •−) via a fluorescence "turn-off" mechanism with the detection limit of 31.89 nM. The fluorescence of arginine-Nb 2 C MQDs is quenched by O 2 •− via dynamic fluorescence quenching mechanism. Fascinatingly, the synthesized arginine-Nb 2 C MQDs showed negligible cytotoxicity on HeLa cells and acted as promising candidates for sensing of O 2 •− in Saccharomyces cerevisiae cells. [Display omitted] • HF-free synthetic strategy was used for the fabrication of arginine-Nb 2 C MQDs. • Arginine-Nb 2 C MQDs act as a fluorescent sensor for selective detection of O 2 •−. • The developed approach exhibited an impressive detection limit of 31.89 nM for O 2 •−. • Arginine-Nb 2 C MQDs served as probe for cell imaging with minimal cytotoxicity. • The developed technique was used to determine O 2 •− in environmental samples. [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 filamentous protein 'actin' plays an essential role in maintaining a proper cellular health and any disruption in its structure and dynamics may induce the growth and metastasis of cancerous cells. Recent studies have shown that, actin can serve as a potential therapeutic target and an indicator to examine the efficacy of modern chemotherapeutic agents. In this regard, the microscopy imaging of actin using fluorescent dyes can pave the way toward development of efficient drugs for cancer treatment. Herein, we report the synthesis of an organic fluorescent dye (BCH) which shows good selectivity toward F-actin at physiological pH. The dye displays a large Stokes shift (∼232 nm), strong emission intensity, good photostability and great sustainability over a wide pH range of 2–10. The dye can directly bind and localize in the actin-rich region of gut, testes and eye of a model organism, Drosophila melanogaster in both living and fixed cells and enable their confocal microscopy imaging without using any actin binding domain. Interestingly, the BCH dye is proved to be nontoxic in the tested organism and has been successfully employed as a potential tool to visualize cellular actin in living tissues of larva and pupa of the organism. [Display omitted] • A benzil biscoumarinyl hydrazone based fluorescent dye has been synthesized. • The dye can bind and image cellular filamentous actin directly without any binding domain. • The dye is proved to be nontoxic in model organism Drosophila melanogaster. • The dye has been successfully employed to visualize cellular actin in living tissues of larva and pupa of the organism. [ABSTRACT FROM AUTHOR]

• A novel fluorescence strategy based on MPA-AgInZnS QDs for sensitive and effective detection of protamine and trypsin. • This assay we investigated was simple, cost-effective, convenient and does not need any complicated pretreatment. • We successfully applied the AgInZnS QDs to intracellular imaging and lysosomes localization. In this study, a fluorescence strategy based on MPA-AgInZnS quantum dots (AIZS QDs) for the sensitive, effective detection of protamine and trypsin was developed. Protamine as a cationic peptide exhibited electrostatic interactions with AIZS QDs, leading to the aggregation of QDs and subsequent enhancement of the fluorescence intensity. The added trypsin catalyzed the hydrolysis of protamine and led to less formation of AIZS QDs/protamine complex, thereby decreasing the fluorescence intensity. Thus, a method for direct determination of protamine and indirect measurement of trypsin using protamine as a tool was developed. The protamine and trypsin concentrations were determined by the detection of the change in fluorescence intensity. Under the optimized conditions, the fluorescence intensity exhibited a good linear response to the protamine concentration, with a limit of detection (LOD) of 0.13 μg mL−1, and trypsin exhibited a linear relationship, with an LOD of 0.04 μg mL−1. The probe exhibited good biocompatibility and low cytotoxicity according to the MTT assay. Moreover, the application of this probe for intracellular imaging and lysosome localization demonstrates potential development in the biomedical and clinical fields. [ABSTRACT FROM AUTHOR]

• The synthetic route of the probe is very simple. • The probe has good reversibility in physiological environment. • The probe Cu-1 shows excellent selectivity toward Cys. • This assay has high sensitivity and exhibits short response time. • This probe is AIE-active leading to high luminous efficiency in cell imaging. In this work, an effective and simple aggregation-induced emission (AIE) active fluorescent probe based on ESIPT luminescence principle, 2-hydroxy-1-naphthal-4-aminoantipyrine (1), was synthesized via a simple chemical reaction. It displayed strong fluorescence enhancement in water. The AIE mechanism of 1 was explored by electron microscopy and computational analysis. We demonstrate the combination effect of intramolecular hydrogen bonds and π-π stacking to endow 1 with such a property. Importantly, the ensemble of 1 with copper ions (Cu-1) as a fluorescent probe enables highly selective and sensitive turn-on fluorescence detection of cysteine (Cys) over other interfering substances. Under optimal detection conditions, this probe has a good linear relationship in the concentration range of Cys between 0 and 8 μM, and the detection limit of Cys was estimated as 84 nM. Furthermore, this assay exhibits good reversibility of 1 to Cu2+ and Cys. Due to its good biocompatibility evaluated by CCK-assay, the probe Cu-1 was finally applied in imaging of Cys within Min6 cells successfully. [ABSTRACT FROM AUTHOR]

Exploring base mismatching-fueled catalytic hairpin assembly (mf CHA) is intriguing to regulate the fluorescence of DNA-scaffolded red Ag nanoclusters (r AgNC) for rapid and amplifiable biosensing of miRNA-155 (miR-155). Herein, we report the first design of a miR-155-responsive mf CHA route with rapid reaction kinetics and high conversion efficiency to light-up the fluorescence of r AgNC. The mf CHA was operated by a signaling hairpin (SH) programmed with the r AgNC template sequence and miR-155-discernible segment, and a G-rich (G12) enhancing hairpin (EH*). To implement faster and more efficient mf CHA amplification as a big challenge in traditional CHA, the locked stem of SH and the loop of EH* were encoded with single mismatched base in different sites, endowing mf CHA with more negative reaction standard free energy as driving force. Note that the originally synthesized r AgNC in SH was non-emissive. However, the presence of miR-155 initiated hairpin assembly between SH and EH* , leading to the displacement of miR-155 for repeated recycling and progressive mf CHA. Rationally, the red fluorescence of r AgNC was remarkably lighted-up due to the proximity to G12 enhancer in the shared dsDNA duplex products. Thus, this mf CHA-based assay platform displayed good simplicity, cost-effectiveness, rapidness, high sensitivity, and potential application for cell imaging. [Display omitted] • A sensitive fluorescence biosensor is developed by using red AgNC (r AgNC) as signaling reporter. • Base mismatching of reactive hairpin stem is designed to fuel catalytic hairpin assembly (mf CHA). • The mf CHA route owns faster reaction kinetics and higher conversion efficacy than traditional CHA. • The r AgNC fluorescence emission is remarkably lighted-up when placing close to a G12 enhancer. • The targeting input is repeatedly displaced and recycled for amplifiable assay and cell imaging. [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]

Highlights • The method with photocaged probes for imaging was efficient and spatiotemporal. • The two probes NDPPI and NNDPPI could be applied in cells and human tissues with satisfactory results. • This strategy can be used in other modified reagents for controlling biological function with light. Abstract Two compounds with nitrobenzene-derived caging groups were designed and synthesized for cells and tissues imaging. After 350 nm irradiation, the two reagents can realize highly efficient fluorescence turn on with large Stokes shift. As for the two probes can bare out a common functional group of aldehyde group under UV irradiation, it may be used for detection of cysteine, DNA methylation in a spatiotemporal method with selectivity. The idea of design and synthesis might be used in other modified reagents for controlling biological function with light. [ABSTRACT FROM AUTHOR]

Graphical abstract Carbon dots and naphthalimide derivative molds into sensor assembly and addition of cysteine into sensor solution eliminates the FRET mechanism. Highlights • We embedded the carbon dots (CDs), gold, and naphthalimide derivative (L1) into a single ratiometric sensor assembly. • Sensor assembly works on the principle of FRET mechanism between CDs and naphthalimide. • Images of endogenous Cys in HeLa cells were recorded using confocal laser scanning microscope. Abstract The detection and discrimination of Cys amino acid from numerous other related biomolecules has great importance in clinical field for diagnosis of various diseases. Herein, to detect the Cys, we embedded the carbon dots (CDs), gold, and naphthalimide (L1) into a single ratiometric fluorescence sensor assembly. Sensor assembly works on the principle of FRET mechanism between CDs and naphthalimide when CDs and L1 adhered on gold nanoparticles surface. Gold metal was turned into solid support by in situ reduction of HAuCl 4 in the presence of CDs and L1. When the assembly was excited at 360 nm, emission maxima at 568 nm corresponded to naphthalimide emission was emerged that signifies the existence of a FRET between the CDs and naphthalimide fluorophores. With the addition of Cys, the FRET mechanism eliminated and the change in the fluorescence emission at two different wavelengths (450 nm and 568 nm) was recorded. The endogenous images of Cys was recorded by collecting the fluorescence images of HeLa cells under fluorescence microscope and also applied for the assay of Cys in blood serum. Cytotoxicity studies of CDs and sensor assembly were evaluated by performing the MTT assay. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Two-photon fluorescent benzocoumarin based ratiometric probe for bisulfite detection. • High sensitivity and excellent selectivity towards bisulfite over other various analytes. • Detection and quantification of endogenous bisulfite level in human serum. • Imaging of bisulfite in HeLa cells under one-photon and two-photon microscopies. Abstract Bisulfite, an equilibrium species with sulfite, is generated from endogenous sulfur dioxide in cell from biothiols. At its elevated level, bisulfite can cause several physiological disorder and diseases. To study such "bisulfite biology" in cell and in tissue, a two-photon fluorescent probe with ratiometric imaging capability is in great demand. To this end, we investigated an aryl aldehyde-type probe derived from a dipolar benzocoumarin dye. The probe sensed bisulfite through formation of the corresponding aldehyde–bisulfite adduct in aqueous buffer at pH 7.4, with excellent selectivity over other biologically relevant species and with well-resolved ratiometric fluorescence changes from 625 nm to 552 nm. The high sensitivity (LOD = 0.08 μM) and reactivity (within 30 s) of the probe towards bisulfite enabled us to quantify an endogenous bisulfite level present in human serum. The promising in vitro ratiometric behavior, however, was deteriorated in the cellular environment, owing to large red-edge and blue-shift effects, observed for both the probe and its bisulfite adduct in cell, which occurred into the unfavorable direction. Thus the cellular imaging with the probe was confined to observe the bisulfite level changes, using one-photon as well as two-photon microscopy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A dual responsive ratiometric fluorescent probe for N 2 H 4 and HSO 3 − was developed. • Different color changes based on different sensing mechanisms for N 2 H 4 and HSO 3 −. • It has high selectivity and low detection limit for N 2 H 4 and HSO 3 −. • Good recovery was achieved in industrial water for detecting N 2 H 4 and HSO 3 −. • It has good biocompatibility. Abstract Hydrazine and bisulfite are poisonous to the environment and human health, hence it is necessary to monitor hydrazine and bisulfite in the environment and living cells. In this study, we reported a smart fluorescent probe (CMCA) for discriminative detection of hydrazine and bisulfite. The single fluorescent probe can respond to hydrazine and bisulfite with two different sets of colorimetric and ratiometric fluorescence signals together with high selectivity, fast response and low detection limit. The discriminative sensing behaviors of the probe for hydrazine and bisulfite were ascribed to different reaction mechanisms, which were confirmed by 1H NMR and HR-MS spectra. The probe has been successfully used to discriminatively determine hydrazine and bisulfite in industrial wastewater with good recoveries. Furthermore, the probe was employed to visualize hydrazine and bisulfite in live cells from different fluorescence channels with good performance. Therefore, this probe has great potential applications for discriminative detection of hydrazine and bisulfite in the environment and living cells. [ABSTRACT FROM AUTHOR]

The estrogen receptors (ERα and ERβ) are vital transcription factors that play important role in physiological functions and are responsible for many hormone-regulated diseases. Herein, we report an environment-sensitive fluorescent probe 2 with a turn-on switch for in situ visualization of the estrogen receptor in living cells. Probe 2 exhibited high ER binding affinity and showed intense fluorescence emission upon binding to ER protein in vitro , and the fluorescence signal was reduced in the presence of a competitive ligand or after ER degradation. With this highly sensitive and selective probe, ER protein degradation was imaged at subcellular level. We believe that this new design strategy might be useful for the development of highly specific fluorescent probes on studies of the function of ER in live cells and related drug discovery. [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]

A series of naphthalene carbohydrazone based fluorescent chemosensors L 1 -L 4 were developed for the detection of Zn 2+ by significant fluorescence enhancement. The binding ratio of the L 1 -Zn 2+ complex was determined by a Job’s plot to be 1:1 and confirmed by ESI–MS studies. The corresponding of the L 1 -Zn 2+ ensemble was elucidated through X-ray crystallography along with spectroscopic studies. Furthermore, the L X -Zn 2+ (X   =   1–2) complexes can specifically detect pyrophosphate (PP i ) in HEPES buffer solution through fluorescence quenching. The detection limit of L X -Zn 2+ (X   =   1–2) for PP i sensing were calculated to be as low as 2.54 ppb and 0.94 ppb, respectively. In addition, due to their good cell membrane permeability and low cytotoxicity, L 1 -L 4 have been applied to sequentially detect Zn 2+ and PP i in living cells. More importantly, the electronic effect of substitute groups on fluorescence signaling have been studied by substituent properties ranging from electron-donating to electron-withdrawing, which sets up a promising strategy for the rational design of fluorescent sensors. [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]

A fluorescent chemodosimeter ( TPAII-2 ) for Hg 2+ was designed with four sulphur atoms in its trigger based on a multisulphite strategy and a control sensor ( TPAII-1 ) was synthesized according to the common design with the deprotection of dithiol. Compared to TPAII-1 , TPAII-2 displayed optimizing selectivity towards Hg 2+ over Ag + , one of the most interference species with strong sulphophile affinity. Further studies indicated the TPAII-2 still maintained the fast detection rate (<2 min) and high sensitivity (detection limited = 15 nM) in HEPES (contain 1% DMSO as cosolvent). As far as we known, sensors based on the deprotection of dithiol were still seldom reported in such solution because of their poor sensing actions in bulk of the aqueous. At last, TPAII-2 was utilized to monitor the Hg 2+ in Hela cells, which evidenced TPAII-2 could maintain the excellent sensing properties in more complex circumstance. More importantly, this recognizing method provided a powerful platform for sensing Hg 2+ in complex systems and highlighted the designing strategy combing the advantages from both coordination-based and reaction-based fluorescent sensors. [ABSTRACT FROM AUTHOR]

Sensing and monitoring of pH changes in live cells are of great importance for understanding of cellular signaling responses. In this study, we developed a highly sensitive and selective pH sensor, rhodamine-based fluorescence dye 1 . The fluorescent emission of 1 at 588 nm increased with the pH decreasing (from pH 7.0–4.0) due to the ring-opening of spirolactam by H + . 1 exhibited good water solubility, high quantum yield, and fast response to pH changes. Moreover, 1 can stain lysosomes in living cells with high photostability and low cytotoxicity. Importantly, 1 was used for monitoring pH changes in lysosomes induced by chloroquine, artesunate and dexamethasone. Therefore, our work provides the potential of probe 1 for visualizing the intracellular changes of pH in clinical and medical applications. [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]

The fluorescent imaging of formaldehyde ( FA ) in live cells and plant tissues plays important role in physiological and pathological studies. However, the development of effective tools or facile strategies to selectively detect FA in bio-systems still remains a great challenge. Herein, two simple probes ( BT-1 and BT-2 ) based on N -heterocyclic derivates have been designed and synthesized for detection of FA in live cells and plant tissues with a significant fluorescence enhancement and large Stokes shifts (about 116 nm). These probes can fast react with FA (less than 3 min), showing the potential ability of detection FA in real time. After interaction with FA , BT-1 has a longer absorption and emission wavelength, better response characteristics as compared with BT-2 . In vitro tests, the maximal fluorescence intensity of each spectrum exhibited excellent linear correlation with the concentration of FA added. Furthermore, the test strips coated with BT-1 can not only differentiate different concentrations of FA and but also recognize FA gas from other relative gases through the changes of fluorescence color which can easily observed by naked eye as these test strips were excited by hand-held UV lamp. More importantly, BT-1 has been successfully used to detect exogenous and endogenous FA in live Arabidopsis thaliana tissues, demonstrating its potential application for studies of physiological and pathological processes associated with FA . [ABSTRACT FROM AUTHOR]

Ozone detection has been extensively explored in atmospheric, environmental, and biological science, but investigations have been seriously impeded by the lack of efficient tools. In this study, a simple and sensitive ozone indicator named Cou–Bu was developed based on the specific reaction of but-3-enyl with O 3 and ozonation-induced elimination of a coumarin carbamate. The specific reaction could enhance fluorescence by >60-fold within 10 s without the addition of amines as a catalyst. A detection limit as low as 4.7 nM was achieved. When applied to cell imaging, Cou–Bu showed low toxicity (IC 50 > 100 μM) and responded to cytoplasm O 3 specifically. Cou–Bu could also find its application in the semi-quantitative determination of ambient O 3 in disk tests. [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]

A new highly selective chemosensor 1 ( E )-5-((2-hydroxybenzylidene)amino)-1H-imidazole-4-carboxamide was designed and synthesized for the sequential recognition of Zn 2+ and S 2− in a near-perfect aqueous media. The sensor 1 exhibited a green color fluorescence in the presence of Zn 2+ . The detection limit (1.18 μM) of 1 for Zn 2+ is much lower than World Health Organization guideline (76 μM) in drinking water. 1 can detect and quantify Zn 2+ in real water samples and the sensing mechanism of Zn 2+ by 1 was explained by DFT calculations. Moreover, resulting 1 -Zn 2+ complex can detect hydrogen sulfide through turn-off fluorescent change, without any anion interference. The detection limit (2.60 μM) of 1 -Zn 2+ complex for S 2− was much lower than EPA guideline (7.8 mM) by odor in drinking water. Furthermore, sensor 1 could detect sequentially Zn 2+ and S 2− in living cells. [ABSTRACT FROM AUTHOR]

Two novel spirobifluorene derivatives containing arylamine groups, SPF-M and SPF-P were synthesized. As the protonation of the aromatic amine N atoms, SPF-M and SPF-P showed significant pH-dependent spectral properties. The pK a values are below 3.0 and they are suitable for extremely acid conditions. Under the UV light, SPF-M permit detection with the “naked eye” which makes it particularly attractive. To our knowledge, SPF-M and SPF-P represent the first examples that two-photon pH sensors were used to measure the extremely acidic pH value. When the pH is higher than 4.0, SPF-M and SPF-P exhibited strong one- and two-photon excited fluorescence and showed no dramatic spectral changes toward pH variations. Thus, the feasibility of SPF-M and SPF-P as multiphoton luminescence bioprobe under physiological conditions is demonstrated by two-photon scanning microscopy imaging experiments on 293T cells. [ABSTRACT FROM AUTHOR]

Development of fluorescent glycopolymeric probes with high water solubility, multivalency, stimuli responsiveness, high cellular internalization efficiency and good photostability, is in urgent demand. Aggregation Induced Emission (AIE) property of glucose based acrylamides (Glc-acryl and Glc-bis) have been studied at various pH, concentration and their application towards lectin recognition, bacterial detection and cell imaging have been probed. The emissions of glycoacrylamides are found to be pH dependent and exhibit Aggregation Induced Emission Enhancement (AIEE) in t -butanol-water mixtures. Fluorescent assay unravelled the specific recognition property of pendant glucose residues on glycoacrylamides towards protein, Concanavalin A (Con A), with an association constant (K a ) of 144 × 10 3 M −1 and 76.3 × 10 3 M −1 , for the interaction with Glc-acryl and Glc-bis, respectively. The limit of detection (LOD) of Con A by Glc-acryl and Glc-bis was found to be 7.85 pM and 3.49 nM, respectively. Incubation with E.coli revealed that the relationship between the fluorescence signal and E.coli concentration was linear from (1.00 × 10 6 ) to (1.70 × 10 8 ) cells/mL (R 2 = 0.98) with LOD (at S/N ratio of 3) of E.coli being 7.30 × 10 5 cells/mL. The cell penetration studies of synthesized glycoacrylamides with INT407 cell lines showed good cellular uptake. [ABSTRACT FROM AUTHOR]

A rhodamine-based fluorescent chemdosimeter SHR for Cu 2+ has been developed based on the spirocyclic ring-opening mechanism. SHR is colorless and nonfluorescent due to intramolecular spirocyclization. Upon incubation with Cu 2+ in aqueous media, a highly efficient ring opening of SHR occurs via Cu 2+ -promoted phenylhydrazine oxidation, causing a dual chromogenic and fluorogenic response. The fluorescent intensity at 580 nm increases linearly with Cu 2+ concentration and as low as 10 nM of Cu 2+ can be readily detected. The proposed chemodosimeter shows high selectivity toward Cu 2+ over other metal ions and proves to be able to image Cu 2+ levels in live cells. [ABSTRACT FROM AUTHOR]

Quinoline based novel fluorescent probes have been synthesized for the selective and sensitive detection of Cu 2+ ions. The probes FQ-1 and FQ-2 exhibit a turn-on fluorescence response towards Cu 2+ ions under physiological conditions in living cells as well. The detection limit of Cu 2+ using the probes FQ-1 and FQ-2 was found to be 1.8 nM and 44.2 nM respectively. [ABSTRACT FROM AUTHOR]

We report perylenediimide-benzimidazolium based fluorescent ‘turn-on’ probe BIM-PDI for selective detection of human serum albumin (HSA) and bovine serum albumin (BSA) proteins. In HEPES buffer (0.1% DMSO), BIM-PDI self-assembles into aggregates and shows absorption maxima at 500 nm and weak fluorescence centered at 577 nm. The addition of HSA or BSA (1 × 10 −9 –5 × 10 −8 M) to the solution of BIM-PDI results in decrease in the emission intensity at 577 nm. However, further increase in concentration of HSA/BSA results in appearance of new blue shifted emission band at 540 nm. The minimum detection limit for HSA/BSA is 3.01 × 10 −10 M at 577 nm and 4.2 × 10 −8 M at 540 nm. On addition of BSA to the solution of BIM-PDI , the size of the aggregates decreased from 100 to 250 nm to <10 nm assigned to microencapsulation driven disassembly of BIM-PDI aggregates responsible for ‘turn-on’ response in fluorescence spectrum. Site-selective experiments using warfarin and diazepam drugs show that BIM-PDI preferably binds at site-I of HSA/BSA proteins. In clinical application of BIM-PDI , we estimated HSA content in blood serum and urine samples. BIM-PDI showed potential application in serum albumin protein tracking and imaging. [ABSTRACT FROM AUTHOR]

A simple triazole bridged molecular probe containing anthracene and quinoline moieties has been designed and synthesized as a fluorescent molecular probe ( 7 ). The photophysical behavior of the probe 7 has been examined and tested for the recognition of ions in partial aqueous medium and HeLa cell. The probe 7 has shown strong affinity for Hg 2+ and has been utilized to develop a stable ensemble, 7·Hg 2 + . The ensemble, 7·Hg 2+ upon interaction with different class of anions showed high affinity for cyanide with ∼16 fold fluorescence enhancement and high limit of detection, 1.25 μM. The live cell imaging studies showed that ensemble 7·Hg 2+ is capable to detect CN − intracellularly. The analytical applicability of the probe for Hg 2+ and CN − has been tested on the test paper strips. Additionally, the naked eye sensitive “ On–Off–On ” switching behavior of 7 has been utilized to mimic the function of a sequential logic circuit at molecular level. The 1 H NMR titration, ESI-MS spectroscopy and DFT calculation confirms the binding behavior between 7 and Hg 2+ . [ABSTRACT FROM AUTHOR]

Thiazole orange ( TO ) stains most nucleic acids giving strong fluorescence signal non-specifically. To resolve the poor discriminating ability of TO among tertiary structures of DNAs, a planar and rotatable π–conjugated small molecule designed by replacing the methylene bridge with an ethylene that slightly increases its structural flexibility, while maintain the crucial conjugated co-planar two-ring system. The study addressed the origin of signal discrimination for the molecule upon binding with different DNA structures and the results demonstrate that the molecule exhibits excellent fluorescence signal discrimination between the DNA G-quadruplexes and other DNA tertiary structures. In a typical staining assay, the molecule induced 30-fold greater fluorescence signal upon binding with Pu27 than that of ssDNA and dsDNA. Molecular modelling studies also support that the flexible ethylene bridge between the two-ring system is the crucial factor for inducing selectivity towards G-quadruplexes. Furthermore, the selectivity, sensitivity, and stability of the molecule were investigated with various techniques. The application of the molecule as a selective staining agent for imaging of G-quadruplex in human prostate cancer cells PC3 and mouse fibroblast L929 was also investigated. The strongly observed green fluorescence signal in the cell nucleus suggests that the molecule is able to enter into the nucleus and then binding with G-quadruplexes. [ABSTRACT FROM AUTHOR]

Superoxide anion radical (O 2 − ), the “primary” reactive oxygen species (ROS) in living systems, is linked to a variety of physiological and pathological processes. Therefore, developing an effective strategy to monitor the fluctuation of O 2 − in biological systems is of great importance. This paper describes a new turn-on two-photon fluorescent probe for endogenous O 2 − detection and imaging, which was rationally designed and synthesized via a non-redox strategy. In the presence of O 2 − , the probe exhibited notable fluorescence enhancement (∼235-fold) with a low detection limit down to 1 nM, indicating a high signal-to-background ratio and excellent sensitivity. In addition, short response time, good biocompatibility, low cytotoxicity, long-term stability against light illumination, specificity to O 2 − over general reductants, and pH stability were demonstrated, indicating that the requirements for cellular O 2 − determination are met. Furthermore, the probe was successfully applied in two-photon fluorescence imaging of endogenous O 2 − in living cells and tissues and showed high imaging resolution and a deep-tissue imaging depth of ∼150 μm, illustrating the promising potential for practical applications in complex biosystems and providing a valuable theoretical basis and technical support for the study of physiological and pathological functions of O 2 − . [ABSTRACT FROM AUTHOR]

A supramolecular ligand for the specific detection of Cd 2+ ions, [pyridine-2,6-diylbis (methyleneimino-2,1-phenylene)]bis(phenyl methanone) ( L ) was synthesized, and characterized by various spectral techniques and single crystal X-ray crystallography. The L exhibits “turn-on” fluorescence and excellent selectivity towards Cd 2+ ions in acetonitrile/HEPES buffer medium (1:5 v/v). The lowest quantum yield and shorter emission lifetime of L (Φ = 0.0293, τ = 9.98 ns) was corroborated by the operation of PET process. This PET is quenched during the complex formation between L and Cd 2+ leads to high quantum yield and longer emission lifetime (Φ = 0.1770, τ = 13.46 ns). The L forms 1:1 complex with Cd 2+ is confirmed by Job’s plot and ESI-Mass techniques. The binding of L with Cd 2+ was studied by UV–vis and NMR. The reversible of L.Cd 2+ with EDTA establishes the reuse of L. The lower detection limit of L was found to be 10.21 nM. The impact of fluorescence with respect to pH, time, temperature and solvent concentrations was investigated to find its practical applications. The sensor was applied for the determination of Cd 2+ ions in water samples. DFT studies explain the binding mechanism between the L and Cd 2+ . The cell imaging studies established that L has been used to detect the intracellular Cd 2+ ions in HeLa cells. [ABSTRACT FROM AUTHOR]

An efficient fluorescein based probe (H 2 L) for the dual sensing of Al 3+ and Cu 2 + has been synthesized and characterized. H 2 L was highly selective toward these two ions with different fluorescence signals and binding modes in two different media. In EtOH-H 2 O (3:2, v/v; pH 4.0), H 2 L selectively binds Al 3+ to form a 1:1 ligand/metal complex, giving rise to a visible pale pink-to-yellow color change and fluorescence enhancement at 440 nm, while in CH 3 CN-H 2 O (2:3, v/v; pH 7.2), H 2 L and Cu 2+ form a 1:2 ratio complex, resulting in a color change from pink to orange-yellow and a significant fluorescence enhancement at 520 nm. The binding modes were confirmed by fluorescence, absorption, IR, ESI-MS and 1 H NMR titrations. The detection limits were calculated to be 7.32 × 10 −8 M and 1.47 × 10 −8 M for Al 3+ and Cu 2+ , respectively. Cell imaging studies demonstrate that this sensor is capable of sensing Al 3+ and Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

Evolution of fluorometric sensing methods has brought an enormous opportunity and exhibited novel potentials for enzymatic activities determination. Herein, we have established an accurate and straightforward fluorescent sensing approach for tyrosinase (TYR) activity based on the formation of fluorescent silicon nanoparticles (Si NPs). Influenced by TYR-induced hydroxylation of phenol into catechol, and an easy reaction between catechol and 3(2-aminoethylamino) propyl (dimethoxymethylsilane) (AEAPDMMS) to generate Si NPs, we have designed a label-free fluorescence turn-on probe for TYR activity measurement. After optimization of all reaction parameters, the proposed approach could selectively determine TYR activity in the linearity range of 0.08–9 U mL−1 with the limit of detection (LOD) of 0.03 U mL−1. The practicability of the method in real sample was assessed by measuring TYR activity in human serum sample with successful results. In addition, Si NPs were wonderfully acceptable for Hela and SiHa cells imaging by virtue of their tolerable cytotoxicity and impressive biocompatibility. Therefore, the designed fluorescent biosensor exhibited a potential and widespread implementation in clinical diagnoses assays. • Silicon nanoparticles based-fluorescence probe was used to determine Tyrosinase. • Tyrosinase could easily make hydroxylation of phenol into catechol. • No further surface modification or purification of silicon nanoparticles was applied. • The designed approach exhibited high performance for Hela and SiHa cell imaging capability. • The designed method was used to determine Tyrosinase in human serum samples. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2), as a known important sulfur oxide in RSS, has an essential role in achieving the homeostasis of organisms. The development of a highly sensitive and selective fluorescent probe for monitoring SO 2 is of great interest in understanding its pathophysiology. Herein, we developed a new near-infrared FRET-based fluorescent probe QD , in which quinolinium fluorophore was selected as the donor and the dicyanoisophorone fluorophore was selected as the acceptor. Probe QD had dual colorimetric and ratiometric fluorescence, larger Stokes shift (277 nm) and longer emission wavelength (677 nm). The fluorescence spectrum showed that QD was highly selective and sensitive with excellent linear response concentration range of 2.5–80 μM. Importantly, probe QD allowed detection of SO 2 derivatives and bioimaging of lysosome-targeted in live cells. [Display omitted] • Showing a strong NIR fluorescence. • Large Stokes shift of 277 nm and wide detection rang of 2.5–80 μM. • Showing high sensitivity and selectivity. • Achieving the dual colorimetric and ratiometric fluorescent strategy. • Achieving the detection of exogenous and endogenous SO 2 derivatives in living cells. [ABSTRACT FROM AUTHOR]

Highly selective and sensitive monitoring of peroxynitrite (ONOO-) in living systems is of significance since it is closely related with the occurrence of multiple diseases. Herein, we successfully constructed ultrathin NAP@Cd-3,5-PDC (NAP@Cd-3,5-PDC-NS, NAP: 2-(6-(4-methylpiperazin-1-yl)− 1,3-dioxo-1 H-benzo[de]isoquinolin-2(3 H)-yl) acetic acid, 3,5-PDC = 3,5-pyridine dicarboxylic acid) fluorescent nanosheets through a simple solution route and subsequent ultrasonication at room temperature. Experiments revealed that the presence of Cd-3,5-PDC-NS significantly enhanced the fluorescence emission of NAP. Under excitation of 398 nm light, the as-obtained NAP@Cd-3,5-PDC-NS could emit about 7-fold stronger photoluminescence than NAP with an equivalent concentration. Also, the as-obtained composite nanosheets could be stably dispersed in phosphate buffer solution (PBS) for 42 days without obvious structure and fluorescence changes. Intriguingly, the strong fluorescence of NAP@Cd-3,5-PDC-NS could be severely quenched by ONOO- without interferences from some other active species, anions/cations, and amino acids. The detection limit of NAP@Cd-3,5-PDC-NS for ONOO- was as low as 61.5 nM, which was 15 times lower than that of the NAP probe alone. Moreover, the as-obtained fluorescent probe could be applied to HepG2 cell imaging, showing its potential application in disease diagnosis. • Ultrathin NAP@Cd-3,5-PDC NS is prepared by a simple solution route and subsequent ultrasonication. • As-obtained NAP@Cd-3,5-PDC NS can form stable sol in PBS and emit strong fluorescence. • Strong fluorescence of NAP@Cd-3,5-PDC NS is sensitively and selectively quenched by ONOO-. • NAP@Cd-3,5-PDC NS sensor bears a far lower detection limit down to 61.5 nM for ONOO-. • NAP@Cd-3,5-PDC NS can be applied for imaging of HepG2 cell. [ABSTRACT FROM AUTHOR]

Currently-reported silicon quantum dots (SiQDs) usually have blue fluorescence, which limits its applications in biological fields, so it is of great significance to develop SiQDs with non-blue fluorescence, especially adjustable multicolor fluorescence. In this study, neutral red was selected as the dopant to prepare a series of N doped silicon quantum dots (N-SiQDs) with adjustable fluorescence colors from blue to orange by simply controlling preparation conditions. Due to the complexion between the N-SiQDs and Cu2+, the fluorescence of N-SiQDs was quenched, and thus N-SiQDs were employed as the fluorescent probe for the detection of Cu2+ in tap water and artificial cerebrospinal fluid with good selectivity, wide linear range (0.05–5 μM) and low detection limit (0.02 μM). In addition, the N-SiQDs were applicable to cell imaging and intracellular detection of Cu2+ as the orange fluorescence of the N-SiQDs could avoid background fluorescence interference from biological samples. Furthermore, N-SiQDs of varied fluorescence colors could be well solidified, exhibiting the potential for the optical device. The present study provided an easy-to-handle and effective way to synthesize multicolor fluorescent SiQDs. [Display omitted] • A novel nitrogen doped SiQDs with multicolor fluorescence was synthesized. • The fluorescence color of N-SiQDs was adjusted by controlling reaction conditions. • The fluorescence of N-SiQDs can be selectively quenched by Cu2+. • The N-SiQDs can be used for cell imaging and cellular detection of Cu2+. • The N-SiQDs of varied fluorescence colors can be well solidified. [ABSTRACT FROM AUTHOR]

A new quinoline appended pyrazoline derivative, 3-(1- benzothiazol-2-yl-5-furan-2yl-4,5-dihydro-1H-pyrazol-3yl)-4-hydroxy-1Hquinoline-2-one (QFP) sensor was synthesized and showed high selectivity and sensitivity towards Ni 2+ ion in H 2 O-DMSO(9:1) at pH = 7.4 in PBS buffer. Theoretical study of absorption behavior is quite agreeable with the experimental value. In addition, the sensor can be used as an intracellular imaging agent to monitor nickel ions in live cells and also can be used for environmental monitoring of real samples. [ABSTRACT FROM AUTHOR]

A new and dual-response fluorescent probe (QLBM) based on quinoline and benzimidazole groups has been designed and developed for recognition of copper(II) ion (Cu 2+ ) and iron(III) ion (Fe 3+ ) simultaneously. This sensor displays a favorable selectivity for Cu 2+ and Fe 3+ ions over a range of other common metal cations in 100% aqueous medium (50 mM Tris buffer, pH 7.2), leading to prominent fluorescence on-off. The detection limits were 1.35 × 10 −7 M for Cu 2+ and 1.24 × 10 −7 M for Fe 3+ respectively. This dual-response fluorescent probe for Cu 2+ and Fe 3+ was distinguished by further reduction of the ascorbic acid. It is reported for the first time to use ascorbic acid to discriminate Cu 2+ and Fe 3+ by fluorescent probe technology. The recognizing mechanism of QLBM toward Cu 2+ and Fe 3+ has been investigated in detail by NMR, HR-MS and density functional theory (DFT) calculations. Moreover, further application of the sensor in fluorescence imaging was studied in HeLa cells due to the low cytotoxicity and good photophysical properties, suggesting that QLBM could be used as a fluorescent sensor for tracking Cu 2+ and Fe 3+ in cells. [ABSTRACT FROM AUTHOR]

Herein, a simple, green, and low-cost way was developed in the synthesis of fluorescent carbon dots (CDs) with well-distributed size, using one-pot hydrothermal treatment of rose-heart radish. The as-prepared carbon dots exhibit exceptional advantages including high fluorescent quantum yield (13.6%), excellent biocompatibility, low-toxicity, and satisfactory chemical stability. More strikingly, as-synthesized N-CDs generate strong response to Fe 3+ ions and gives rise to the fluorescence quenching. This phenomenon was used to develop a fluorescent method for facile detection of Fe 3+ with a linear range from 0.02 to 40 μM and a detection limit of 0.13 μM (S/N = 3), and further extended to measure environmental water samples with satisfactory recoveries. Eventually, the low toxicity and strongly fluorescent carbon dots were applied for cell imaging and the quenched fluorescence by adding Fe 3+ , demonstrating their potential towards diverse applications. [ABSTRACT FROM AUTHOR]

A new FRET-based ratiometric fluorescent probe (DSPT) for the detection of bisulfite was developed by the dansyl-piperazine-benzothiazolium conjugate platform, in which C C conjugated with benzothiazolium was recognition unit and benzothiazolium moiety was mitochondria-targeted unit. The C C double bond group would undergo Michael addition reaction with bisulfite, triggering significant fluorescence ratio increasing which was linear to the concentrations of bisulfite. The probe can be used in real sample including dry white wine and tap water. Besides, the test strips for bisulfite were prepared. Moreover, cell imaging results indicate that this probe is cell-membrane permeable and mitochondria-targetable, and can be applied to monitor both exogenous and endogenous bisulfite in ratiometric fluorescence imaging. [ABSTRACT FROM AUTHOR]

A novel ethylenediamine (EDA) based chemosensor 5 [dimethyl 2,2′-((3-oxocyclohex-1-ene-1,2-diyl)bis(azanediyl))dibenzoate] has been designed and synthesized for the turn on fluorescence sensing of Cu 2+ ions. The molecular geometry configuration of 5 is identified by X-ray diffraction and its corresponding orbital electron distributions are predicted by density functional theory (DFT). The probe 5 exhibits strong and selective complexing ability towards Cu 2+ over the other metal ions tested in both acetonitrile and aqueous solvent systems. MeCN-HEPES buffer system is more suitable for the selective fluorescence sensing of Cu 2+ ions. In addition, the lowest detection limit is 0.30 μM for Cu 2+ ions. This probe has also been applied successfully for the confocal fluorescence imaging of MDCK cells. Therefore, this probe can be used in both the environmental and biological systems for the detection of Cu 2+ . [ABSTRACT FROM AUTHOR]

Co 2+ fluorescent probes have been scarcely developed in recent years because it is difficult to selectively sense cobalt ions in presence of competitive divalent ions. Herein, is an account of synthesis and characterization of reasonably designed turn-on fluorescent probe SGPB1 with Salicylhydrazide as binding site based on BODIPY adapted fluorophore. It was capable to operate in CHEF mechanism toward Co 2+ and showed high sensitivity and remarkable selectivity for Co 2+ with 10-fold fluorescence enhancement. Furthermore, cell imaging experiments proved that SGPB1 was suitable for detecting Co 2+ in biological environment. [ABSTRACT FROM AUTHOR]

An efficient and highly selective dihydrazone based fluorescent probe N ′, N ′–bis((2–hydroxynaphthalen–1–yl)methylene)malonohydrazide (H 2 nmh), has been synthesized for selective detection of Al 3+ ions and characterized by different physico–chemical and spectroscopic techniques. The probe shows an enhanced fluorescence in the presence of Al 3+ ions in ethanol–water (2:3 v/v) solution which is not observed in the presence of other cations (Na + , K + , Mg 2+ , Ca 2+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ and Hg 2+ ). The binding modes of H 2 nmh with Al 3+ were studied by UV–vis, fluorescence and 1 H NMR titrations. The probe act as dibasic hexa–dentate ligand and interacts with two Al 3+ ions with a binding constant K B = 5.74 × 10 9 M −1 and detection limit 5.78 × 10 −8 M. Detailed insights of probe–metal interaction mechanism were studied by mean of density functional theory (DFT) as well as time dependent–DFT calculation. MTT assay on live MCF–7 cells has been performed to evaluate the cytotoxicity of the probe which suggests viability of the probe to MCF–7 cells even at higher concentration (100 μM) with no serious cytotoxicity in cells. Live cell imaging study clearly indicates that the accumulation of Al 3+ in the cytoplasm of cells can be detected by H 2 nmh. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an important gas signal molecule, which participates in a variety of pathological and physiological processes. In this paper, a novel near-infrared fluorescence probe (NIR-H 2 S) with azido as the reaction site was designed and synthesized. NIR-H 2 S utilizes the reducibility of H 2 S to detect H 2 S, which effectively avoids the interference of biological thiols. NIR-H 2 S is a D-π-A dye, and thiophene is the π-bridge, which can not only enhance the π conjugation of the molecules but also increase the vibrational flexibility of the molecules. Therefore, NIR-H 2 S shows a significant near-infrared (NIR) turn-on signal at 693 nm, with a large Stokes shift (258 nm). Cell imaging experiments show that NIR-H 2 S has high contrast imaging ability and can be used to detect H 2 S in cells. The excellent performance of NIR-H 2 S indicates that NIR-H 2 S is one of the valuable candidate probes for the detection of H 2 S in living cells. • A fluorescence probe NIR-H 2 S was designed based on D-π-A. • NIR-H 2 S exhibits fluorescence turn-on response at 693 nm toward H 2 S. • NIR-H 2 S has a large Stokes shift (258 nm), which greatly improves sensitivity and signal-to-noise ratio in imaging. • Using azide as response site, NIR-H 2 S has excellent selectivity to H 2 S. [ABSTRACT FROM AUTHOR]

Telomerase was regarded as a pivotal tumor marker for cancers diagnosis and prognosis evaluation. Hence, the accurate quantification detection and distribution information of telomerase in complex biological environment is undoubtedly very important. Herein, we developed a dual-mode strategy for telomerase detection which combined the advantages of both surface-enhanced Raman scattering (SERS) and fluorescence approaches. The nanoprobes, consists of Au NPs and specific nucleic acid probes, would be triggered by telomerase to generate electromagnetic hot spots enhanced Au dimers for telomerase fluorescence imaging and label-free Raman detection after entering the living cells. In addition, a stronger fluorescent signal was generated after two signal amplifications. With the help of ATP and catalytic hairpin assembly (CHA), more Au dimers will be generated to increase the Raman signal. The experimental results showed that the dual-mode nanoprobe has great selectivity and sensitivity to telomerase and could distinguish different kinds of tumor cells by in situ imaging. Limit of detection (LOD) was 7.76 HeLa cells for fluorescence detection and 2.98 Hela cells fore SERS detection. This nanoplatform would be a promising dual-mode diagnostic strategy for biomarkers in complex biological environment. • Au Dimers self-assembly enhanced the intensity of hot spots in the nanogaps. • The Raman signal of adenine in the nanogaps was significantly amplified. • Fluorescence method can achieve in situ imaging analysis of intracellular targets. [ABSTRACT FROM AUTHOR]

Based on fluorescent resonance energy transfer (FRET), we developed a ratiometric fluorescent probe 1 for sensing Cu 2+ . As expected, probe 1 exhibited high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Cu 2+ in aqueous solution. A significant color change from pale yellow to pink could be observed, enabling naked-eye detection of Cu 2+ . Furthermore, fluorescence imaging experiment of Cu 2+ in living MGC-803 cells demonstrated its value of practical applications in biological systems. [ABSTRACT FROM AUTHOR]

The present article deals with the detailed complexation study along with exploration of possible utilization of 25,26,27,28- tetra -hydroxy-11,23- di -( tert -butyl)-5,17- di -(2-antracenyl)azocalix[4]arene (7 ) and 25,26,27,28- tetra -hydroxy-11,23- di -( tert -butyl)-5,17- di -(1-pyreneyl)azocalix[4]arene (8) as bio-imaging fluorescent probe to detect Cu 2+ in human colon cell line, SW-620, observed by fluorescence microscopy. Complexation properties of ligands 7 and 8 toward selected transition metal ions have been investigated by UV–vis and fluorescence spectroscopies. It has been noticed that ligands 7 and 8 are not only proved to be an efficient Cu 2+ selective chromoionophore but also possess effective fluorescence properties by complexing with Cu 2+ ions. The FTIR spectroscopic method has also been applied for further confirmation of the complexation phenomenon of ligands 7 and 8 with metal ion and were found to be adequate. Moreover, fluorescence microscopy studies showed that ligand 7 may be used as fluorescent probe to detect Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

A novel p -dimethylaminobenzamide-based Schiff base derivative DTBL was synthesized via a simple reaction and utilized as a “turn-on” fluorescent indicator for copper ion (Cu 2+ ). It showed extraordinary high selectivity toward Cu 2+ in MeCN–H 2 O (v/v = 3:2, pH = 5) HOAc-NaOAc buffer solution, and the fluorescence intensity change were noticeable for the Cu 2+ detection even in the presence of different kinds of foreign ions and compounds at very high concentrations. The 2:1 stoichiometry of DTBL-Cu 2+ complex was calculated from Job’s plot based on fluorescence titrations. The good linear relationship easily exhibited a dynamic response range for Cu 2+ from 0 to 3.4 μM and the detection limit (0.32 nM) of DTBL for Cu 2+ was far lower than the maximum allowable level of the WHO limit (30 μM) for drinking water. Moreover, the adaptability of DTBL for biological applications was also demonstrated by fluorescence imaging of intracellular Cu 2+ in living cells. The results indicate that DTBL should be available for the research on the biological and environmental applications associated with Cu 2+ . [ABSTRACT FROM AUTHOR]