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Five novel dual-state emissive imidazo[1,2- α ]pyridine-based luminogens IP1-5 were rationally designed and prepared by varying the conjugation length and the nature of donor-acceptor (D-A) units. These D-A chromophores displayed cyan, green, yellow, and red fluorescence in the solid state, with full-color emission achieved for the first time through modification of imidazo[1,2- α ]pyridine core. Interestingly, IP1 and IP5 in the solid state exhibited an abnormal remarkable blue-shift emission compared with those in THF, probably due to the highly twisted molecular conformations and solvent effect by theoretical calculations as well as crystal structure analyses. Importantly, IP1-5 revealed remarkable reversible acid-induced acidichromism, accompanied with dual change of colorimetric and fluorometric determination. Viscosity-dependent fluorescence was next conducted, indicting IP1-3 can be utilized for local viscosity detection. Moreover, IP1-5 served as promising candidates for multicolor bioimaging with low cell toxicity and good biocompatibility. Five asymmetric donor-acceptor dual-state emissive imidazo[1,2- ɑ ]pyridines have been synthesized with full color emission acidichromism, viscosity-dependent fluorescence, and biological imaging. [Display omitted] • Five DSE fluorophores IP1-5 based on carbonyl-substituted imidazo[1,2- α ]pyridine have been synthesized and characterized. • IP1-5 exhibited full color solid emission through manipulation of D-A electronic structures and conjugation length. • IP1-5 displayed reversible acidochromism and bioimaging applications with excellent biocompatibility and cell permeability. • IP1-3 showed viscosity-dependent fluorescence with application as potential viscosity sensors. [ABSTRACT FROM AUTHOR]

A novel cancer cell and lysosome dual-targeted photosensitizer (PS) termed by BMP was developed for fluorescence imaging and photodynamic therapy (PDT). BMP consists of a porphyrin(Zn) core with appropriate singlet-triplet state distribution enables it to function as an imaging agent as well as a PS, a biotin moiety that can target cancer cells, and a morpholine group specific to lysosomes. Intracellular experiments demonstrated that the dual-targeted photosensitizer BMP could preferably accumulate in cancer cells and subsequently locate within lysosome organelles. Upon irradiation, BMP could generate red fluorescence emission (Φ em = 6.3%) and singlet oxygen (1O 2 , Φ Δ = 55%) for the dual functionality of cell imaging and PDT, respectively. Notably, BMP exhibited much higher photocytotoxicity toward cancer cells (A549 cells) compared to normal cells (BEAS-2B cells). Importantly, 1O 2 produced by BMP induced oxidative damage of lysosomes, and subsequently triggered cell death of A549 cells, as evidenced by the loss of morphological integrity and cell rupture. A cancer cell and lysosome dual-targeted photosensitizer BMP was designed to generate red emission and singlet oxygen (1O 2) simultaneously, which were utilized successfully for dual-targeted fluorescence imaging and photodynamic therapy. [Display omitted] • A dual-targeted photosensitizer was designed and synthesized by modularization. • Biotin acted as a targeting ligand for cancer cells, and morpholine was selected as the lysosome-specific group. • Red fluorescence and singlet oxygen generation were achieved for fluorescence imaging and PDT of cancer cells simultaneously. [ABSTRACT FROM AUTHOR]

A series of hydroxy thiophene-conjugated benzothiazole derivatives (HTB s) was prepared to investigate their fluorescence emission behaviors and capability to selectively stain subcellular organelles for fluorescence imaging. The HTB derivatives exhibited excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) behaviors, according to their molecular structure. Subtle changes in the molecular structure of the HTB influenced its response to changes in the surrounding environment, such as the solvent polarity and/or pH. In vitro cellular imaging experiments revealed that HTB A (5-(benzo[d]thiazol-2-yl)-[2,2′-bithiophen]-4-ol) could selectively stain mitochondria. In contrast, HTB B -CO 2 Et (ethyl 5'-(benzo[d]thiazol-2-yl)-3′-hydroxy-[2,2′-bithiophene]-5-carboxylate), which contains a regioisomeric hydroxy thiophene unit with an electron-withdrawing ethyl ester group, showed the capability to stain lipid droplets (LDs) in living cells. When the hydroxyl group in HTB B -CO 2 Et was protected with a benzyl group, effective staining of LDs in live cells was achieved. Thus, we successfully obtained an effective fluorescent probe. Collectively, the results indicated that small structural changes resulted in substantial changes in the intracellular localization and in vitro imaging ability of the prepared compounds. [Display omitted] • Hydroxy thiophene-conjugated benzothiazole derivatives (HTB s) were synthesized. • HTB s exhibited polarity-dependent bright emission due to ESIPT and ICT. • The structural change of HTB s enabled selective staining of mitochondria and lipid droplets. [ABSTRACT FROM AUTHOR]

Developing fluoran dyes for fluorescent material is significant but challenging because they are notorious for terrible luminescent efficiency. In this manuscript, two fluoran dyes (F3 and F4) were synthesized by the introduction of thiazole and indazole into the fluoran skeleton, which showed colored and fluorescent spirolactone opening form in a wide pH range (F3 : 1–10, F4 : 1–13). In addition, the absorption and emission spectra of methyl esterification products F3Me and F4Me showed large Stokes shifts (over 75 nm) in water and achieved an improved fluorescence quantum yield of 30.1% in CHCl 3. Based on the dye F4Me, a new fluorescent probe F4HP was developed, which showed high selectivity and high sensitivity (LOD of 2.0 nM) to copper ions in H 2 O/CH 3 CN (v/v, 3/2) system. Moreover, the sensing experiment was allowed in the pH range of 4.0–7.5. Furthermore, the F4HP exhibits suitable cell cytotoxicity and can be applied for imaging intracellular copper ions by confocal fluorescence imaging technology. Thiazole and indazole functionalized fluoran dyes were prepared with improved fluorescence and application in the construction of a novel copper-selective and sensitive fluorescent probe. [Display omitted] • Two modified fluoran dyes were prepared with stable fluorescence in water. • F4Me achieved a fluorescence quantum yield of 30.1% in CHCl 3. • A novel probe F4HP for Cu2+ was prepared with high selectivity and sensitivity. • F4HP could be employed as a tool for imaging intracellular Cu2+. [ABSTRACT FROM AUTHOR]

In this study, a pH-sensitive fluorescent probe was created through the host-guest assembly of an amphiphilic hydroxyphenyl benzotriazole derivative (HBT-11) and cucurbit[7]uril (CB7). The fluorescence of HBT-11 is highly dependent on the molar ratio (r) of CB7 to HBT-11. If r < 1, the peak positions remain unchanged while the intensity increases with r. If r > 1, the emission peaks shift to longer wavelengths. The complexation also results in a shift in the p K a of HBT-11. The 1:1 mixture of CB7 and HBT-11 has a p K a close to neutral pH. The supramolecular probe allows for discrimination of malignant A549 and benign HEK 293T cells owing to a pronounced 8-fold light-up effect in malignant A549 cells attributed to the pH-responsive fluorescence. Given that the selective light-up mechanism is based on the pH-sensitive fluorescence of the supramolecular probe, this approach is expected to be applicable to other cancer cells. [Display omitted] • A pH-sensitive supramolecular fluorescence probe was constructed. • The fluorescent intensity of the probe was greatly enhanced as pH < p K a. • The probe was applied to discriminate malignant and benign cells. [ABSTRACT FROM AUTHOR]

Fluorescent probes sensitive to microenvironments have constantly been attractive, due to their significant benefits in monitoring changes in the pathophysiological microenvironment and their use in the early detection of associated disorders. In this work, we explored three new molecular rotors that could be potential candidates for detecting lipid droplets (LDs) in cancer cells based on coumarin derivatives connected with electron-donating polycyclic units including, tetraphenylethylene (LD-TPE), pyrene (LD-PYR), and 4,5-diphenylimidazole (LD-DIP). Gratifyingly, LD-PYR showed exceptional polarity and viscosity sensitivity and demonstrated bright fluorescence in highly viscous environments due to the suppression of the twisted intramolecular charge transfer (TICT) phenomenon and intramolecular rotation. Moreover, microenvironment-guided specific LD bioimaging by LD-PYR exhibited a reasonable ability to distinguish between cancer and noncancer cells. These data suggested that LD-PYR has interesting clinical diagnostic and microenvironment-related biological applications. [Display omitted] • Highly polarity and viscosity-sensitive fluorescence probes have been introduced. • LD-PYR probe shows bright fluorescence in a lipophilic environment due to TICT suppression. • LD-PYR demonstrates good biocompatibility in both cancer cell and normal cell lines. • LD-PYR can selectively image lipid droplet in cancer cells. [ABSTRACT FROM AUTHOR]

A new amphiphilic polynorbornene-based copolymer P1 was designed and synthesized successfully by ring-opening metathesis polymerization (ROMP) of polyethylene glycol (PEG) containing monomer NB-PEG and ferreocene-anchored monomer NB-Fc. The copolymer P1 can bind with anionic uranine dye (UD) through multiple interactions to form no fluorescent P1 / UD nano-structure ensemble in aqueous solution. The P1 / UD ensemble can be used as indicator displacement assay (IDA) for ATP detection with a high sensitivity and selectivity. Upon the addition of ATP, the fluorescence is significant enhanced for displacement of UD from P1 / UD ensemble. The LOD value of P1 / UD ensemble toward ATP is as low as 35.9 nM. The P1 / UD ensemble exhibits an excellent photo-stability and biocompatibility, and has been successfully used for imaging ATP in living cells. [Display omitted] • A new amphiphilic polynorbornene-based copolymer P1 was designed and synthesized. • P1 can bind with UD to form P1 / UD nano-structure ensemble in aqueous solution. • P1 / UD ensemble can detect ATP with a high sensitivity and selectivity by IDA. • P1 / UD ensemble exhibits an excellent photo-stability and biocompatibility. • P1 / UD ensemble has been successfully used for imaging ATP in living cells. [ABSTRACT FROM AUTHOR]

The abnormal expression of cytochrome P450 2J2 (CYP2J2) is closely related to the proliferation of human cancer cells. In this study, a red-emitting probe with an aggregation-induced emission (AIE) effect for the quantification of CYP2J2 was developed by modifying the typical AIE fluorescent group tetraphenylethylene (TPE) through two-step synthesis. Upon addition of CYP2J2, the probe underwent O-demethylation and spontaneously 1,6-elimination reactions of p-hydroxybenzyl that allowed it to alter its photophysical properties, thus realizing light-up detection of CYP2J2 with extremely large Stokes shift (236 nm), excellent sensitivity and selectivity, low detection limit (1.09 nM). Moreover, this new AIE-active probe with good biocompatibility was admirably employed to tracking endogenous CYP2J2 in living cells. • An AIE-based fluorescent probe (TPE-Bn) was designed to detect CYP2J2. • This probe showed significant Stokes shift (236 nm), good photostability, excellent sensitivity and selectivity, and low cytotoxicity. • This probe can be used to visualize endogenous CYP2J2 in living cells and tissues. [ABSTRACT FROM AUTHOR]

GSH is an important biological thiol which involves many biological processes, and also an biomarker for cancer. So it's urgent to develop fluorescent probes with excellent sensitivity and high selectivity for GSH detection. Herein, we develop a new GSH-responsive fluorescent probe TPP-Naph-SS-Fc based on PET (photoinduced electron transfer) mechanism. TPP-Naph-SS-Fc contains naphthalimide fluorephore, the ferrocene quencher, the disulfide cleavage bond and the triphenylphosphine mitochondrial localizer. It shows a fluorescence turn-on response toward GSH for cleavage the disulfide bond, which result in the blocking of PET process. Especially, this probe can localize in mitochondria and make real-time imaging of GSH, also demonstrate the ability to distinguish between cancerous and normal cells. A naphthalimide-based fluorescent probe with mitochondria targeting for GSH sensing and cancer cell recognition based on PET mechanism have been reported. [Display omitted] • A novel naphthalimide-based fluorescent probe TPP-Naph-SS-Fc was prepared based on PET mechanism. • The probe shows fluorescence turn-on response toward GSH. • It has the excellent mitochondria targeting ability. • It has been applied in cellular GSH imaging and cancer cells recognition. [ABSTRACT FROM AUTHOR]

The novel V-shaped donor-π-acceptor-π-donor compounds bearing an aldehyde group (1Pip , 2EtO , and 3TEG) were designed, synthesized, and evaluated as the two-photon excited fluorescence probes for the selective detection of cysteine (Cys). Their structures were fully characterized by 1H NMR, 13C NMR, FT-IR, and HRMS. The optical properties of the target compounds in various solvents were studied in details and the time-dependent density functional theory calculations were performed to shed light on their electronic structures. It is found that all of them exhibit large Stokes shifts (6331-10047 cm−1). 1Pip and 3TEG are capable of detecting Cys with high selectivity, good anti-interference ability, and favorable two-photon absorption performance. The limits of detection were determined to be equal to 0.15 μM for 1Pip and 0.73 μM for 3TEG. The possible recognition mechanism was also validated by 1H NMR and HRMS. One- and two-photon fluorescence imaging experiments indicate that 3TEG shows more satisfactory cellular membrane permeability than 1Pip , and it can successfully visualize the endogenous and exogenous Cys in living cells. These results imply that 3TEG has potential as a two-photon fluorescence probe for detecting Cys in biological samples. [Display omitted] • Three novel D-π-A-π-D type two-photon absorption compounds were developed to detect Cys. • 3TEG shows high selectivity to Cys, favorable two-photon absorption property, large Stokes shifts, and good biocompatibility. • 3TEG has been successfully utilized to image endogenous and exogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H -type aggregation to J- type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments. [Display omitted] • New boron complexed fluorophore (BOSPY) has been developed from various arylboric acids. • Molecular chirality of these dyes after boron complexation was confirmed by X-ray structures. • These dyes exhibit strong aggregation-induced emission (AIE). • These AIE dyes are suitable for fluorescence imaging and two dyes can specifically localize in lipid droplets of cells. [ABSTRACT FROM AUTHOR]

In this work, a colormetric fluorescent probe named NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed based on 2-hydrazinobenzothiazole and 6-methoxy-2-acetonaphthone for sensing hypochlorous acid (HClO) with high selectivity and sensitivity (detection limit: 1.7 nM). Also, NMH had a strong anti-interference effect and a fluorescence color change in the solution which can be seen by the"naked eye". Moreover, NMH could be applied to detect ClO− in tap water and test paper. In addition, cell imaging experiments showed that probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. In this work, probe NMH, which exhibited aggregation-induced emission (AIE) characteristic in water/EtOH binary solvent was developed and could be applied to detect ClO− with colormetric response in tap water, test paper and living cells. [Display omitted] • A selective fluorescent probe NMH with aggregation-induced emission characteristic was developed by one step reaction. • The probe NMH could be widely used as a "naked eye" probe for detecting ClO− by the color changes from purple to blue. • The probe NMH could detect endogenous and exogenous ClO− in A549 cells successfully. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

Triphenylphosphonium (TPP) cations endow fluorophores with improved hydrophilicities and mitochondria targeting abilities. Evidently, the number of cationic moieties can influence the behavior of fluorophores in different environments. Two water-soluble BODIPY fluorophores, 3TPP and 5TPP , were constructed with three and five TPP groups, respectively, in their structure. Both showed maximum absorption and emission at 640–700 nm wavelengths; however, 5TPP showed a fluorescence quantum yield 10 times higher than that of 3TPP in an aqueous medium, highlighting the beneficial effect of two additional TPP groups on the photophysical properties. While both fluorophores showed excellent stabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells, 5TPP permeated into the mitochondria better than 3TPP. Interestingly, 5TPP demonstrated a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) in relation to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). Notably, the fluorescence intensity of 5TPP increased with increasing BSA concentration. The present work is the first report on BODIPY sensors with multiple bulky cationic moieties and provides insights on the applicability of 5TPP as a novel biomaterial for mitochondrion tracking and light-up fluorescence protein sensing. • BODIPY-based fluorophores, 3TPP and 5TPP , were conjugated with three and five (triphenylphosphonium) TPP groups, respectively. • Both fluorophores showed excellent photostabilities and mitochondrial imaging abilities with low cytotoxicities in HeLa and MCF-7 cells. • 5TPP exhibited a 90-fold increase in "turn-on" fluorescence in the presence of bovine serum albumin (BSA) with respect to that of four other proteins (i.e., lysozyme, esterase, transferrin, and fibrinogen). [ABSTRACT FROM AUTHOR]

HClO is recognized as an indicator for phagocytosis and inflammatory response. Excess HClO ruptures lysosomes and leads to cell apoptosis, which has been proposed as a cure for cancer treatment. As a consequence, the real-time and in situ cell imaging for HClO is highly appealed in the field of anticancer pharmacy. In this work, a series of silane-modified rhodamine fluorescers with various functional groups were designed, hoping to find a fluorescer with near IR emission for bio-imaging in live cells, along with unique sensing response towards ClO− over competing species. These silane-modified rhodamine fluorescers were carefully characterized, their photophysical parameters and responses towards ClO− and competing species were compared systematically. An optimal probe showed emission quantum yield of 0.26 with emission wavelength at 681 nm. Emission "turn-on" effect was observed, with calibration equation of F = 0.720*[ClO−]2+40.047*[ClO−]+54.982, R2 = 0.999, and the limit of detection (LOD) was calculated as 0.03 μM. Corresponding sensing mechanism was revealed as an HClO-mediated cyclization reaction. Fluorescence imaging for Hela cells and A549 lung cancer cells was performed. The lysosome-targetable feature was confirmed. • A series of silane-modified rhodamine fluorescers with near IR emission for bio-imaging in live cells were reported. • An optimal probe showed emission quantum yield of 0.26 with emission wavelength at 681 nm. • Sensing calibration equation was a non-linear one and the limit of detection (LOD) was calculated as 0.03 μM. • Sensing mechanism was revealed as an HClO-mediated cyclization reaction. [ABSTRACT FROM AUTHOR]

In this paper, oxazolepyridine and coumarin units were combined to prepare cell membrane fluorescent probe (PM-A) through aldol condensation reaction. PM-A had long wavelength emission (665–739 nm), high molar extinction coefficient (around 3.14 × 104 M−1cm−1) and large Stokes shift (150–219 nm). The photo-stability test showed that PM-A had a high relative residual absorption (93%) after 6 h of continuous illumination. In addition, the supramolecular interaction between PM-A and β-cyclodextrin was evaluated and applied to cell imaging. Probe PM-A had no fluorescence in water, but had obvious fluorescence signal in β-cyclodextrin solution. With the addition of β-cyclodextrin (0–800 eq), the fluorescence quantum yield of PM-A increased from 0% to 45%. Laser confocal experiments showed that when only PM-A was added, the probe concentration needed to be 15 μM to image the cell membrane obviously. In sharp contrast, with the help of β-cyclodextrin solution, the concentration of probe PM-A only needed 0.5 μM to quick and high specificity image cell membranes. Moreover, PM-A had high photo-bleaching resistance and long retention time after adding β-cyclodextrin. These excellent properties of PM-A were of great significance to the study of cell membrane. [Display omitted] • A near-infrared fluorescent probe (PM-A) with oxazolepyridine and coumarin units was prepared for the imaging of cell membrane at 15 μM. • The supramolecular interaction between probe PM-A and β-cyclodextrin was evaluated. • Probe PM-A showed rapid and high specificity of cell membrane imaging at the concentration of 0.5 μM with the help of β-cyclodextrin. [ABSTRACT FROM AUTHOR]

Herein, a highly selective and sensitive squaraine dye (F-0) for Cu2+ detection was developed. Upon addition of Cu2+, F-0 could greatly decrease absorption peak accompanying with fluorescent quenching about 170 folds. The detection limit can reach as low as 7.2 nmol/L. F-0 showed excellent water solubility and achieved naked eye detection of Cu2+. A paper strip pre-stained with F-0 solution was fabricated and showed color changed from blue to colorless upon addition of Cu2+. F-0 exhibited highly specific to Cu2+ over other metal ions. Furthermore, on the basic of low cell cytotoxicity, F-0 could be utilized to monitor Cu2+ in living cell and mice via fluorescence imaging. These results showed that F-0 has great potential for a more complex applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), as one of the important reactive oxygen/nitrogen species, is associated with many physiological and pathological activities. Therefore, effective detection methods with high sensitivity and rapid response time are essential to reveal its functions. A novel Rhodol-based fluorescent probe RN is constructed and synthesized by introducing of 1,1-dimethylhydrazone as a recognition group. Due to the oxidative breakage of the C N bond by ONOO−, the probe has significant fluorescence enhancement change with excellent detection properties such as rapid response time, high sensitivity and selectivity. Moreover, probe RN show low cytotoxicity and is successfully capable of imaging endogenous and endogenous ONOO− in living cells. These properties indicate that RN has great application potential for imaging of ONOO− in biological systems. [Display omitted] • New Rhodol derivative is designed as fluorescent probe (RN) for monitoring of ONOO−. • Probe RN exhibits turn-on fluorescent change toward ONOO− with high sensitivity and rapid response time (<60s). • Probe RN can be used for monitoring endogenous ONOO− changes in cells. [ABSTRACT FROM AUTHOR]

Organic fluorescent materials have been widely used in various fields including visualization of latent fingerprints and imaging of lysosomes. High-performance organic fluorescent molecules based on simple molecular structures are still limited and highly demanded for high-definition and high-contrast imaging of latent fingerprints and lysosomes. In this work, two organic fluorescent molecules (DANPAN and DANBEN) were developed based on dimethylamino naphthalenyl phenylethene structure. These two molecules have quite different fluorescent properties, and the position of cyano group significantly affects the optical properties of these dimethylamino naphthalenyl phenylethene derivatives. Compound DANPAN shows strong yellow emission in solid state, while compound DANBEN has strong fluorescent emission in organic solutions. In addition to these differences, both compounds have large Stokes shifts and positive solvatochromic properties. Further studies showed that these compounds could be used to display latent fingerprints on various substrate surfaces. The obtained fingerprint images have excellent contrast and high resolution. It is also found that these molecules could specifically stain lysosomes in living cell within short incubation time. This work provides a series of new high-performance organic fluorescent materials with diverse applications. Highly emissive dimethylamino naphthalenyl phenylethene derivatives have been synthesized, which show large Stokes shifts and positive solvatochromic properties. These compounds could be applied for visualization of latent fingerprints and specific localization of lysosomes in living cell imaging. [Display omitted] • Two dimethylamino naphthalenyl phenylethene derivatives are synthesized. • These molecules show large Stokes shifts and positive solvatochromic properties. • These compounds could be applied for visualization of latent fingerprints on various substrate surfaces. • These molecules could be used for specific localization of lysosomes in living cell imaging. [ABSTRACT FROM AUTHOR]

Fluorescence probes have shown great potential in lipid droplets (LDs) imaging, whereas the imaging performance of the present commercial dyes is far from ideal. In addition, there still is lack of an effective strategy for designing LDs specific probes with satisfactory imaging performance. In this work, we have provided a novel method and probes based on donor (D)-acceptor (A) structure with nitrobenzoxadiazole (NBD) as the A unit and benzene derivatives as the D units, which are expected to show strong emission in lipid environment. Four probes (N–B , N–MeB , N–MeOB and N–Me 2 NB) with increasing electron-donating ability were prepared, whose fluorescence-emission changed from aggregation-induced emission (AIE) (N–B and N–MeB) to aggregation-caused quenching (ACQ) (N–MeOB and N–Me 2 NB). Intriguingly, the emission of these probes in oil changed from blue region to red (652 nm) with the increase of electron-donating ability from N–B to N–Me 2 NB , indicating the great emission regulable ability of this strategy. Moreover, these probes could specifically stain the intracellular and tissular LDs, which had shown considerable performance in the studying of LDs spatial distributions in mice and human atherosclerosis plaques. Impressively, N–Me 2 NB with the strongest electron-donating group of N-dimethylaniline showed negligible emission in aqueous solution but remarkable enhanced emission in oil, which could still efficiently stain the intracellular LDs at 200 nM. This novel construction strategy would provide new ideas for preparation of LDs specific probes. • A novel strategy for designing lipid droplets (LDs) specific probe was provided. • The fluorescence emission of N–MeOB and N–Me 2 NB were significantly enhanced in lipid environment. • N–MeOB and N–Me 2 NB showed great LDs imaging performance in cells. • N–MeOB and N–Me 2 NB can detect the LDs distribution in mice and human atherosclerosis plaques. [ABSTRACT FROM AUTHOR]

Detection and imaging of Cysteine (Cys) and Homocysteine (Hcy) in living systems have drawn extensive attention over the years due to their significant biological role. However, few fluorescence probes have been reported to distinguish Cys and Hcy in near-infrared (NIR) range. In this paper, an original NIR Cys and Hcy fluorescent probe, namely DTRN , was synthesized. DTRN was constructed by using an acryloyl ester group as a trigger and dicyanoisophorone-derived as the fluorophore unit, it was found to emit NIR fluorescence with a 718 nm emission and have large stokes shift (∼176 nm). DTRN hold excellent performances such as ultrasensitivity (LOD = 0.09 μM), high specificity and fast response (<2 min) for Cys. Distinctly, after Hcy was introduced, the emission intensity of DTRN at 718 nm must take 20 min to reach a plateau and the LOD was found to be 0.12 μM. The sensing mechanism for Cys and Hcy in C 2 H 5 OH/PBS (4/6, v/v, pH = 7.4) was studied by 1H NMR spectroscopy and HRMS. Most importantly, the ability of DTRN to detect Cys in HeLa cells had also been achieved. A NIR fluorescent probe (DTRN) was synthesized by using acryloyl ester group as a trigger and dicyanoisophorone-derived as the fluorophore unit, it can detect Cys and Hcy emit NIR fluorescence at 718 nm and have large stokes shift (∼176 nm). [Display omitted] • A NIR fluorescent probe (DTRN) with large stokes shift (∼176 nm) was synthesized. • DTRN could distinguish Cys and Hcy by time-dependent fluorescence signals. • The LOD for Cys and Hcy was calculated to be 0.09 μM and 0.12 μM. • DTRN was successfully exploited for detecting Cys in HeLa cells. [ABSTRACT FROM AUTHOR]

In this paper, a cationic amphiphile (denoted by DPP-10) with diketopyrrolopyrrole decorated with methoxylated tetraphenylethylene via a phenyl bridge was designed, synthesized, and applied as a turn-on fluorescence probe for bovine serum albumin (BSA) detection and selective cell imaging. DPP-10 showed very weak fluorescence emission when dispersed in the solution, while its emission was drastically enhanced upon the addition of BSA, which should be attributed to the electrostatic interaction-driven assembly between DPP-10 and BSA. The limit of detection was as low as 0.08 μmol/L, which is lower than that reported for most probes. The fluorescence probe shows good selectivity for BSA among the tested proteins, high photostability, and immunity to the disturbance of ions. DPP-10 with excellent cytocompatibility was applied to HeLa cell imaging, where only the BSA-rich cells showed a strong signal-to-background contrast. A turn-on fluorescence probe was built for the detection of BSA via electrostatic interaction-driven assembly. The BSA-responsive feature was successfully applied in selective cell imaging. [Display omitted] • A turn-on fluorescence probe was designed and synthesized for the detection of BSA. • The probe has a low detection limit, high selectivity and excellent biocompatibility. • The probe was successfully applied to selectively light up BSA-rich HeLa cells. [ABSTRACT FROM AUTHOR]

G-quadruplexes (G4s), DNA or RNA structures formed by guanine-rich sequences, play indispensable regulatory roles in numerous biological processes. Here we develop a Near Infrared (NIR) fluorescence G4 indicator (TAQ) which enables activatable imaging of G4s in live cells. The indicator TAQ is merely emissive in aqueous solution and its fluorescence at 677 nm is remarkably enhanced in the presence of a typical hybrid G4 structure. TAQ broadly interacts with different G4 structures, exhibiting high selectivity toward G4s over single- or double-stranded nucleic acids. It is demonstrated that TAQ affords dynamic fluorescence response to G4 concentrations in the range of 5.0–600 nM with an estimated limit of detection of 0.51 nM. Live cell studies demonstrate that TAQ delivers intense fluorescence signals upon specific interaction with G4 structures. We further employ TAQ to track the dynamics of RNA/DNA G4s in live cells. This NIR fluorescence indicator could provide a valuable tool for interrogating the dynamics of G4 structures in live cells. [Display omitted] • A near infrared (NIR) fluorescence G4 indicator (TAQ) is reported for activatable imaging of G4s in live cells. • The NIR fluorescence probe exhibits high sensitivity and high selectivity toward G4s over other nucleic acids. • The NIR fluorescence probe is successfully introduced to track the dynamic changes of G4s in live cells. [ABSTRACT FROM AUTHOR]

Organic materials with strong solid-state fluorescence and sensitive stimuli responsiveness are highly desired for both fundamental research and practical applications. We report herein an azabenz-annulated perylenediimide (AzaBPDI)-based dye, AzaBP-TPE, which contains tetraphenylethene units in the planar aromatic structure. AzaBP-TPE undergoes typical intramolecular charge transfer, aggregation-induced emission, and mechanochromic fluorescence. In the solid state, AzaBP-TPE emits bright-yellow light with a photoluminescence quantum yield of 27%, and this emission becomes red fluorescence when MCF is induced, by using mechanical force to collapse the crystalline structure. Moreover, bright-yellow fluorescence can be recovered by exposing AzaBP-TPE powder to chloroform vapor. Notably, AzaBP-TPE nanoparticles can penetrate live cells and emit red light and, therefore, can be applied as a functional dye in bio-imaging. [Display omitted] • A novel azabenz-annulated perylenediimide-based dye, AzaBP-TPE was developed. • AzaBP-TPE exhibits typical AIE and reversible MCF in the solid state. • Good biocompatibility indicates AzaBP-TPE a potential functional dye for cell-imaging. [ABSTRACT FROM AUTHOR]

Various aggregation-induced emission luminogen (AIEgen) derivatives based on TPE (tetraphenylethylene) containing the electron-donating moiety (–NMe 2 , –OMe) and bromine (–Br) moiety were prepared, which are key intermediates for tuning the emission wavelength of TPE; Type 1: dimethylamine (NMe 2)-substituted derivatives, Type 2: methoxy (OMe)-substituted derivatives, Type 3: bromine (Br)-substituted derivatives, and Type 4: mixed formulation derivatives. We systematically analyzed the synthesis, AIE properties, photophysical properties, and biological applicability of 16 types of TPE-based AIEgen. We expect that our investigation, especially the donor-substitution effect of TPE, could serve as a guide to developing a new TPE-based AIEgen series as well as fluorescent probes. [Display omitted] • Donor-substitution effect of tetraphenylethylene (TPE) AIEgens was systematically identified. • Synthesis and photophysical property of 16 derivatives of TPE was disclosed. • CLSM imaging of cells using the TPE derivatives was demonstrated. [ABSTRACT FROM AUTHOR]

Butyrylcholinesterase (BChE) is an esterase expressed by the liver, which is released into the plasma immediately. The activity of BChE in the serum is a sensitive indicator for determining the protein synthesis function of liver cells. Therefore, the development of high-efficiency chemical tools for detecting BChE is in urgent need. In this work, based on the ingenious combination of specific BChE enzymatic reaction, a ratiometric fluorescence probe was established to easily achieve the determination of BChE with high sensitivity with LOD calculated as low as 0.077 μg/mL. This probe also possesses a superior selectivity to BChE without the interference of other biological species even acetylcholinesterase (AChE), which gives it great potential to work for sensing in biological samples. The accurate IC 50 (0.195 mM) of iso-OMPA, a specific inhibitor of BChE, could also be examined, indicating the excellent performance in elucidating inhibitory efficacy. In addition, the probe can be used for fluorescence imaging of BChE activity in living cells as well as animal tissues. These advantages indicate that the probe has important practical value for the monitoring of BChE activity. [Display omitted] • A ratiometric fluorescent probe W1 for the determination of BChE was constructed. • The probe provides high sensitivity for BChE with a LOD calculated as 0.077 μg/mL. • W1 possessed a superior selectivity to BChE without interference of other species. • The accurate IC 50 of iso-OMPA also indicated the excellent sensing performance. • The sensing scheme is workable in biological samples including serum and cells. [ABSTRACT FROM AUTHOR]

Here, a coumarin-based probe 4-chloro-3-formyl-2-oxo-2H-chromen-7-yl acrylate (named CFCA), which performed high efficient and specific recognition for cysteine (Cys), was successfully synthesized and characterized by NMR and MS. The CFCA probe showed colorimetric and "turn-on" fluorescent signals to Cys, and its color changes could be recognized by naked eyes. CFCA responded to Cys with the characteristics of rapid response time (less than 40 s), high selectivity, and excellent anti-interference. Among all kinds of samples, only Cys could significantly enhance the fluorescence intensity of the solution, which was not affected by the presence of other interferences. At the same time, within a certain concentration range, there was a good linear relationship between relative intensity of fluorescence and Cys concentration. The detection limit has been calculated to be as low as 0.33 μM. And the sensing mechanism of CFCA with Cys has been well confirmed by 1H NMR and HR-MS spectra. Moreover, the fluorescence probe CFCA was successfully used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. • A coumarin-based probe CFCA was successfully prepared, synthesized, and applied for Cys detection. • CFCA can perform high efficiency and specificity colorimetric and fluorescent double signal recognition for Cys. • CFCA has been used for imaging Cys in living cells and processed into test strips for on-site analysis and testing. [ABSTRACT FROM AUTHOR]

Intracellular redistribution of a photosensitizing fluorescent dye is concerned with its diagnostic and therapeutic features. To date such studies in this area are extremely scarce. Herein, a fluorescent photosensitizer PDI-1 with lysosome-targeting function has been prepared by functionalization of perylenediimide (PDI) with bis-tertiary amine groups. Fluorescence live cell imaging shows that PDI-1 can indeed target the lysosome, however, uncommon inter-organelle translocation was observed under continual visible light irradiation through a microscope. The cell nucleolus was subsequently lit up by PDI-1 in a photo-controllable manner. The imaging study using fixed cells confirmed that RNAs were the major target of PDI-1 in cell nucleolus. In addition, PDI-2 and PDI-3 were prepared by slightly modifying the structure of PDI-1. However, there is no obvious photo-induced redistribution observed on both PDI-2 and PDI-3. The result implies that even though tiny modification to the structure of a photosensitizer, the influence can be significant for its photobiological behavior. [Display omitted] • Inter-organelle translocation was observed upon imaging using PDI-1 a perylenediimide-tertiary amine photosensitizer (PS). • PDI-1 offers a promising fluorescence probe for nucleolus imaging through a photo-controllable manner. • Tiny modification to the structure of a PS can lead to great influence to its photobiological behaviors. [ABSTRACT FROM AUTHOR]

A series of benzoxazole-pyridinium salt derivatives with two-photon excited fluorescence performance were synthesized and fully characterized. Among them, compounds 2 , 3 and 4 were the isomers with different positions of pyridine N, while compounds 4N , 4S , 4P , 4F and 4B were derived from compound 4 through anion exchanging reaction. Their photophysical properties had been systematically investigated, and the results indicated that the position of pyridine N and the type of anions had a significant influence on their optical properties and bio-imaging application. Transforming the position of pyridine N could affect their fluorescence quantum obviously; the maximum fluorescence quantum is 0.21 for compound 3 in DMF. Meanwhile, we found that the altering anions might be used to regulate their two-photon fluorescence performance, only compounds 4N , 4P and 4B possessed excellent two-photon excited fluorescence emissions, and the highest two-photon cross-section was 1868.69 GM for compound 4B in DMF. In addition, two-photon fluorescence cell imaging experiment demonstrated the potential bio-application of partial compounds with good photostability and low cytotoxicity. A series of water solubility of benzoxazole-pyridium salt derivatives including compounds 2 , 3 , 4 , 4N , 4F , 4P , 4S and 4B with excellent two-photon excited fluorescence performance were synthesized and applied in biological imaging. The structure-property relationship study showed that the position of pyridine N and the type of anions have a significant influence on their optical properties and bio-imaging application. [Display omitted] •The structure of target compounds was determined by HR MS with positive and negative ion model. •Counter anions had a influence on the two-photon excited fluorescence emissions. •The position isomerization of pyridine N affected their biological imaging performance. [ABSTRACT FROM AUTHOR]

Two imidazole decorated 4-dicyanomethylene-2,6-dimethyl-4H-pyran (DCM) derivatives, namely ImDCM-1 and ImDCM-2, have been designed and synthesized, which show aggregation-induced emission (AIE) features in THF-water mixture due to inhibition of intramolecular rotation (water fractions 80% and 70% for ImDCM-1 and ImDCM-2, respectively). The further increasing water leads to fluorescence bathochromic-shift and enhancement of ImDCM-1, probably arising from variation in size and solubility of aggregates. In contrast, ImDCM-2 exhibits a distinct red-shift and further enhancement in emission with water fraction increasing from 70% to 80%, then the further increment of water induces decrease in emission, which may be ascribed to formation of J-aggregates, followed by size and solubility changes of aggregates. In addition, selective and sensitive fluorescence responses of ImDCM-1 and ImDCM-2 towards viscosity can be observed. Significantly, the low cell cytotoxicity as well as wide pH-independence (4.0–10.0) fluorescent response towards viscosity allow them to be utilized for tracing monensin-stimulated viscosity increase in living cells. • Two imidazole decorated dyes with aggregation-induced emission behaviors have been reported. • Viscosity-selective and sensitive fluorescence response can be observed. • Tracing monensin-stimulated cellular viscosity increase by cell imaging can be realized. [ABSTRACT FROM AUTHOR]

It is necessary to measure lysosomal pH in living cells in order to maintain the normal performance of cell functions. Herein, a novel ratiometric fluorescence nanosensor based on carbon dots for lysosomal pH sensing was successfully developed via one-pot solvothermal means. The CDs have two pH-dependent emission wavelengths locating at 415 and 555 nm with distinct fluorescence color change switching between blue and yellow from pH 3.0 to 8.0. Due to its plentiful amino groups on the surface, the probe is lysosome-targeted. It is demonstrated that intensity ratios (F 555 /F 415) against pH = 3.0–8.0 are fitted with the Boltzmann equation with a pKa of 5.47 matched well with lysosomal pH. Because of the merits of great pH sensitivity, selectivity, biocompatibility and photostability, the probe was successfully applied for lysosomal pH detection during cells imaging. Besides, CDs were further used for acidic and neutral water pH sensing by a smartphone in a fast and expedient way. • CDs with two fluorescence emissions are successfully developed through one-pot solvothermal method. • CDs can ratiometricly monitor the fluctuation of pH in lysosome with an obvious fluorescence color alteration. • CDs can be applied for fast and expedient detection of water pH by a smartphone, too. [ABSTRACT FROM AUTHOR]

Two ratiometric fluorescence probes, RMC and RMD, were synthesized for detecting HSO 3 − in test tube and living cells. Probe RMC based on FRET mechanism exhibited excellent ratiometric signals, high sensitivity (1.08 nM), outstanding selectivity, fast response (within 22 s) to HSO 3 − in physiological pH. The satisfactory performance of RMC in cell imaging suggested that it could be applied to monitor endogenous and intracellular bisulfite with minimal cytotoxicity and excellent photostability. More importantly, probe RMC realized targeting for lipid droplets. In practice, probe RMC could be successfully applied to detect HSO 3 − in food sugar. Besides, cheap test strips were made and used handily for rapid and qualitative detection of HSO 3 − in water by naked eye as well. Therefore, probe RMC could be a potential biological tool to explore the roles of HSO 3 − under different physiological and pathological conditions. [Display omitted] • Two ratiometric fluorescence probe RMC and RMD based on FRET for bisulfite were developed. • Probe RMC could reveal a response in 22 s toward HSO 3 − with high selectivity and sensitivity. • Probe RMC could target lipid droplets in living cells. • Probe RMC could detect HSO 3 − in sugar solution. • The test strips could be made handily for rapid and qualitative detection. [ABSTRACT FROM AUTHOR]