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

In this work, a dicyanoisophorone-based turn-on fluorescent probe, DCIP , for highly selective and sensitive detection of cysteine was designed based on nucleophilic substitution mechanism. Moreover, compared with typical cysteine probes, DCIP showed great selectivity and sensitivity for cysteine over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). Further, the detection limit toward cysteine was calculated to be as low as 0.70 μM. In addition, the utility of DCIP as a bioanalytical molecular tool was demonstrated by fluorescence imaging of biothiols in living cells. [ABSTRACT FROM AUTHOR]

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

The development of small-molecule G-quadruplex DNA probes has attracted significant attention in recent years. However, G-quadruplexes can display a wide variety of topologies, which process different structures and functions. Therefore, selective discrimination one G-quadruplex structure over another is promising. Herein, we reported the design, synthesis and biological evaluation of a long-chain fatty amine functionalized triphenylamine-quinolinium conjugate 1b . Significant enhancement of the fluorescence intensity (over 180 fold) was observed when 1b bound with HRAS G-quadruplex DNA, while much weaker enhancements were presented in the presence of other G-quadruplexes (45–90-fold) and single/double-stranded DNAs (less than 20-fold), indicating 1b had an excellent selectivity to HRAS . The details of the interactions were investigated by UV–Vis, FID and CD analysis. The results show 1b could interact and stabilize HRAS structure mainly by π-π stacking binding mode. The introduced amine chain of the structure core was found to be better in the terms of inducing selectivity toward G-quadruplex structure. In addition, the application of 1b as a fluorescent agent for living cell imaging was also demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] Mitochondrial viscosity is an important parameter in biological system, of which the abnormality is related to a variety of diseases. Therefore, it is necessary to develop fluorescent probes for imaging mitochondrial viscosity. Herein, two red-emission fluorophores (L1 and L2) with donor–π–bridge-acceptor (D-π-A) structure were facilely synthesized and systematically studied. These fluorophores were demonstrated to be viscosity-sensitive, and particularly, L2 could precisely target mitochondria through a wash-free procedure. Moreover, probe L2 was membrane potential-independent, and it was capable of permeating the cell membrane within a short time (≤30 s). Importantly, L2 was workable in fresh tissues with a favorable penetration depth of 33.89 µm. All these excellent performances endow probe L2 promising capability to investigate the correlation between mitochondrial viscosity and related diseases. [ABSTRACT FROM AUTHOR]

We herein designed and synthesized a light-up fluorescent probe L1 for Hg 2+ species, which is based on indole derivative and Rhodamine fluorophore. The new probe can show a linear response to Hg 2+ with high sensitivity and selectivity. As the Hg 2+ concentration changed from 0 to 450 μM, the fluorescence intensity of L1 at 575 nm changed from 50 to 6181 (∼120-fold). The detection limit of the probe was 5.0 × 10 −8 M. Besides, we have successfully applied L1 to monitor Hg 2+ species in living MCF-7 cells by way of fluorescence imaging. [ABSTRACT FROM AUTHOR]

We presented the design, synthesis and preliminary evaluation of the 2,4-dinitrobenzenesulfonate (DNBS) of imidazo[1,5- α ]pyridine derivative, NIPY-DNBS , as a turn-on fluorescent probe for the detection of thiols in aqueous solution. The reaction mechanism was confirmed by means of fluorescence, absorption and HRMS. The large Stokes shift (201 nm), high sensitivity (the detection limit for Cys was calculated to be as low as 0.17 μM) and fast response (10 min) of NIPY-DNBS make it a practical and reliable method for fluorescence imaging. Furthermore, application of NIPY-DNBS for the selective detection of intracellular thiols has been successfully demonstrated in living A549 cells. [ABSTRACT FROM AUTHOR]

Development of an excited-state intramolecular proton transfer (ESIPT)-based fluorescent probe ( BIHM ) for selective recognition to homocysteine (Hcy) over glutathione (GSH), cysteine (Cys) and other amino acids is described. The distinctive fluorescence response of BIHM to Hcy over Cys is interpreted by density functional theory calculations. Bioimaging experiments of intracellular Hcy detection manifest the great potential utility of the probe. [ABSTRACT FROM AUTHOR]

A fluorescent probe, 1,4-diethyl-7-(3-pyridin-2-yl-acroyloyl)-1,2,3,4-tetrahydro-5-oxa-1,4-diazaanthracen-6-one (probe 1 ), with an emission in near-infrared region was developed for sensitive and selective detection of biothiols. Probe 1 is essentially non-fluorescent due to the strong intramolecular charge transfer (ICT) from the electron-donating tetrahydroquinoxaline moiety to the electron-withdrawing pyridine group. Upon the treatment with biothiols, the conjugation system was broken via Michael addition reaction between biothiols and α,β-unsaturated ketone, which inhibited the ICT process and resulted in a remarkable fluorescence enhancement with an emission maximum at 660 nm. Moreover, probe 1 was successfully applied to image intracellular thiols in living cells. [ABSTRACT FROM AUTHOR]

Abstract: This study reports a benzothiazole-based fluorescent probe with simple structure for thiols. This probe exhibited high on/off signal ratios and good selectivity toward thiols over other analytes, and was successfully applied to the imaging of thiols in living cells. [Copyright &y& Elsevier]

• A novel fluorescent probe 1 for rapid detection of Zn2+ was developed. • The structure and the synthetic route of probe 1 were simple. • Probe 1 can discriminate Zn2+ from Cd2+ and other cations. • Probe 1 can be used for determination of Zn2+ ion in living cells. A simple novel and an easy-to-synthesize fluorescent probe 1 for detection of Zn2+ based on 1-(4-amino-2-hydroxyphenyl)ethan-1-one was developed. Probe 1 exhibited an effectively selective and sensitive recognition towards Zn2+ over Cd2+ and other cations. The Job's plot and HRMS experiments reveal the formation of 1:1 binding stoichiometry between probe 1 and Zn2+. The association constant (K) of probe 1 with Zn2+ was calculated to be 7.998 × 104 M−1. The detection limit of probe 1 towards Zn2+ was calculated at very low concentration up to 46 nM. The perfect reversibility of probe 1 for sensing Zn2+ was also demonstrated. Detection mechanism of Zn2+ ion by probe 1 was suggested through the analytical tools like UV–vis, FESEM, TEM, 1H NMR titration and the DFT calculations experiments. More importantly, the fluorescence imaging in C6 cells suggested that simple sensor had great potential in the application of biological imaging. [ABSTRACT FROM AUTHOR]

• A naphthyl-coumarin-based fluorescent probe is developed as a racemic mixture. • Selectively detecting Cys and GSH by using the probe at two excitation wavelengths. • A thiazolidine product is proposed for the reaction of the probe with Cys. • The reaction of the probe with GSH might generate a macrocyclic aldimine product. • The probe can detect Cys and GSH in live cells by using two emission channels. Selective detection of Cys and GSH by using one fluorescent probe with two different excitation wavelengths is developed based on a naphthyl-coumarin aldehyde probe. Mechanistic studies indicate that the distinctively different fluorescent responses of the probe toward Cys and GSH at the two excitation wavelengths are due to two different reaction pathways that generate different products. The probe has been used to detect Cys and GSH in HeLa cells by using two emission channels. [ABSTRACT FROM AUTHOR]

Herein, we have developed a new 4-substituted pyrene-based fluorescent probe 4-PYB with large Stokes shift and achieved highly sensitive detection of H 2 O 2 in aqueous solution. Furthermore, the probe 4-PYB is suitable for detecting exogenous H 2 O 2 in living RAW 264.7 cells. • Compound 4-PYB was designed and synthesized based on nonactive position-substituted pyrene. • Compound 4-PYB with large Stokes shift displays relatively outstanding sensitivity and selectivity for H 2 O 2. • Probe 4-PYB has been successful applied to identify H 2 O 2 in liver cells. A new 4-substituted pyrene derivative 4,4,5,5-tetramethyl-2-(4-((pyren-4- yloxy)methyl)phenyl)-1,3,2-dioxaborolane (4-PYB) has been designed and synthesized by introducing phenyl boronic ester to the precursor 4-hydroxylpyrene. Compound 4-PYB with large Stokes shift displays relatively outstanding sensitivity and selectivity for H 2 O 2 , which is successfully applied to detect H 2 O 2 in living cells. The fluorescent properties of probe 4-PYB displays significantly different properties from its derivative Py-Boe based on 1-hydroxylpyrene, further indicating the functionalization of pyrene on the different position is still an effective strategy to develop novel pyrene-based functional materials. [ABSTRACT FROM AUTHOR]

A ER-targetable probe R1 for HOCl was synthesized. R1 shows excellent selectivity and high sensitivity, excellent anti-interference, and can quickly reach the response platform. • A new ER-targetable ICT-based fluorescent probe R1 for HClO was developed. • Probe have rapid response (30 s), big Stock's shift and a wide range of pH(7–13). • The imaging in EC1 cells demonstrated its value of practical application. The endoplasmic reticulum is the largest organelle in the cell. Studies have shown that the concentration of HClO is related to many diseases. A new type of probe R1 has positioned to the endoplasmic reticulum. The probe shows good positioning effect, excellent selectivity and high sensitivity, excellent anti-interference, and can quickly reach the response platform. The obvious color change can be used for naked eye observation. Due to its low cytotoxicity, probe R1 was successfully used for EC1 cells imaging under a laser scanning confocal microscope. [ABSTRACT FROM AUTHOR]

• We developed a near-infrared fluorescence probe, TMN-NH 2 -Cys. • The probe exhibited a large stokes shift. • The selective detection of Cys was confirmed by a visible colour change. • The probe exhibited a low cytotoxicity. • It could be applied to the imaging of endogenous Cys with fluorescence enhancement. Cysteine (Cys) is a sulfur-containing nutritional amino acid that plays an important role in the physiological function of living systems. We developed a near-infrared fluorescence probe, TMN-NH 2 -Cys. Upon the treatment with Cys, TMN-NH 2 -Cys exhibited a large Stokes shift (180 nm) and a visible colour change. TMN-NH 2 -Cys can selective detect Cys over homocysteine and glutathione. The probe was synthesised by a simple and high yielding three-step reaction. In addition, the probe exhibited a low cytotoxicity, and could be applied to the imaging of endogenous Cys with fluorescence enhancement. [ABSTRACT FROM AUTHOR]

• A highly sensitive phenolphthalein Schiff-base turn-on fluorescent probe was reported. • A lowest detection limit of 9.79 × 10−9 M for Al3+ was achieved. • Highly sensitive sensing system for evaluation of Al3+ in living cells. An efficient fluorescent probe, 3, 3-bis(4-hydroxyphenyl)-2-benzofuran-1-one-isoquinoline-1-carbohydrazide hydrazine (L), has been prepared for the selective sensing of Al3+ in DMSO-H 2 O (90:10, v/v) solution. The 1:2 stoichiometry of L and Al3+ was determined from Job's plot experiments and ESI-MS. The binding constants was observed as 7.106 × 1010 M−2, and the detection limit is 9.79 × 10−9 M. Moreover, the as-prepared probe shows high sensitivity to Al3+ both in acidic and neutral conditions. In addition, the as-prepared probe with good biological compatibility shows effective imaging of Al3+ in living cells. [ABSTRACT FROM AUTHOR]

• Four chloroacetate based fluorescent probes were synthesized for a comparative study. • H4 displayed great ratiometric property and selectivity for cysteine. • H4 was applied for real-time cysteine imaging in HeLa cells. The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloroacetyl group was often used as a reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloroacetyl group based fluorescent probes (C1 , C2 , C3 , and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloroacetyl group turned into an advantage when connected with a ratiometric fluorophore. With the modification of chloroacetyl group, probe H4 displayed excellent ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for quantitative detection of Cys in fetal bovine serum and real-time imaging in living HeLa cells with low toxicity. [ABSTRACT FROM AUTHOR]