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[Display omitted] • Developed a novel near-infrared fluorescent probe, NRO-βgal, for detecting endogenous β-galactosidase. • The probe demonstrated high selectivity and sensitivity towards β-galactosidase with a low detection limit (LOD = 0.2 U/L) and rapid response time (within 10 min). • NRO-βgal enables effective imaging of β-galactosidase levels in ovarian cancer mouse models, contributing to advancements in tumor detection and surgical interventions. The advancement of biological imaging techniques critically depends on the development of novel near-infrared (NIR) fluorescent probes. In this study, we introduce a designed NIR fluorescent probe, NRO-βgal, which exhibits a unique off–on response mechanism to β-galactosidase (β-gal). Emitting a fluorescence peak at a wavelength of 670 nm, NRO-βgal showcases a significant Stokes shift of 85 nm, which is indicative of its efficient energy transfer and minimized background interference. The probe achieves a remarkably low in vitro detection limit of 0.2 U/L and demonstrates a rapid response within 10 min, thereby underscoring its exceptional sensitivity, selectivity, and operational swiftness. Such superior analytical performance broadens the horizon for its application in intricate biological imaging studies. To validate the practical utility of NRO-βgal in bio-imaging, we employed ovarian cancer cell and mouse models, where the probe's efficacy in accurately delineating tumor cells was examined. The results affirm NRO-βgal's capability to provide sharp, high-contrast images of tumor regions, thereby significantly enhancing the precision of surgical tumor resection. Furthermore, the probe's potential for real-time monitoring of enzymatic activity in living tissues underscores its utility as a powerful tool for diagnostics in oncology and beyond. [ABSTRACT FROM AUTHOR]

Carboxylesterase 2 (CES2) plays a critical role in the metabolism of ester- and amide-containing drugs and thus has an impact on drug efficacy and toxicity. This study introduces QVJ-CES2, a near-infrared fluorescent probe designed to enhance thyroid cancer diagnosis through CES2 enzyme activity and distinct cellular viscosity of thyroid cells. The probe's dual-response mechanism significantly amplified fluorescence in high-viscosity environments, thus had high sensitivity. Our findings revealed that QVJ-CES2 could detect CES2 activity with a limit of detection as low as 1.9 ng/mL. In vitro experiments confirmed the rapid and selective response of QVJ-CES2 to CES2 and the ability to distinguish cancer cells from their normal cells with high specificity. Most importantly, the fluorescence intensity difference between cancerous and normal cells after incubation with the probe was as high as 7-fold, attributable to the synergistic enzyme and viscosity cascade response. Further, in vivo studies demonstrated that the probe was effective in accurately identifying thyroid cancer tissues, showing that it is a promising tool for early cancer detection and precise surgical interventions. • Dual-response mechanism boosts fluorescence in viscous settings, enhancing sensitivity. • QVJ-CES2 showcases exceptional detection capabilities for CES2, with a sensitivity threshold as low as 1.9 ng/m. • Fluorescence difference between cancerous and normal cells is 7-fold due to enzyme-viscosity response. • In vivo studies show the probe accurately identifies thyroid cancer tissues. [ABSTRACT FROM AUTHOR]

A novel water-soluble and reversible fluorescent probe was designed and synthesized based on a rhodamine B derivative. It was used for detection of Cu 2 + in drinking water and in living cells with high sensitivity and excellent selectivity. The tested concentration range and the limit of detection (LOD) of the probe were 0–15.00 μmol L − 1 and 0.085 μmol L − 1 , respectively. In addition, the mode of binding and mechanism of interaction between the probe and Cu 2 + were analyzed by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Based on fluorescein, a novel water-soluble and reversible fluorescent probe (Flu-Py) was designed and synthesized for the sequentially “ON–OFF–ON” fluorescent detection of Al 3+ and F − in concentration range of 0–10 μmol L −1 and 0–30 μmol L −1 , respectively, with high sensitivity and excellent selectivity. The detection limits for Al 3+ and F − were 0.092 μmol L −1 and 0.112 μmol L −1 , respectively. The binding mode and sensing mechanism of Flu-Py with Al 3+ was verified by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculation. The “ON-OFF–ON” fluorescent property of Flu-Py upon the addition of Al 3+ and F − was utilized for the imaging of living cells. [ABSTRACT FROM AUTHOR]

A new rhodamine derivative (RhS) with a recognition capability for Cu 2+ was synthesized and employed as a reversible fluorescent probe for Cu 2+ in drinking water and living cells. The spirolactam ring-opening of probe RhS induced by Cu 2+ lead to a highly selective fluorescence “turn-on” response toward Cu 2+ over other metal ions with micromolar sensitivity. The 1:1 stoichiometric structure between RhS and Cu 2+ were supported by Job's plot, MS and DFT theoretical calculations. The analytical results obtained by UV–vis and fluorescence spectrophotometry show that the linear range and the limit of detection (LOD) of the present probe for Cu 2+ are 0.50–20.00 and 0.11 μmol L −1 , respectively. The present probe was applied to the detection of Cu 2+ in drinking water with the recoveries ranging from 100.4 to 101.2%, and the fluorescence imaging for living HeLa cells. [ABSTRACT FROM AUTHOR]

A trivalent chromium (Cr 3 + ) fluorescence probe (RhC) was designed and synthesized via Schiff base reaction based on rhodamine–crown ether conjugate. This probe displayed a favorable selectivity for Cr 3 + over a range of other common metal ions in DMF/H 2 O (3:7, v / v ; PBS buffer 50 mmol L − 1 ; pH = 6.8) solution, leading to prominent fluorescence “OFF–ON” switching of the rhodamine fluorophore. The limit of detection was calculated to be 1.5 μmol L − 1 (S/N = 3). The binding ratio of RhC–Cr 3 + complex was determined to be 1:2 according to the Job's plot and HR-MS. The probe was successfully applied to examination of Cr 3 + in drinking water spiked samples. The average recoveries ranged from 104.9% to 106.9% at spiked concentration level of 10.00 μmol L − 1 , and the obtained results were consistent with those obtained using atomic absorption spectrometry (AAS). Moreover, bioimaging experiments showed that RhC can sense the Cr 3 + in living cells with a fluorescence enhancement signal. [ABSTRACT FROM AUTHOR]

In this article, a novel fluorescent probe (NRBE) for detecting H 2 O 2 was developed using benzyl boronic ester as the H 2 O 2 -recognized group and Nile red as the matrix. The probe has several advantages, such as good selectivity, high sensitivity (LOD = 75 nM), good water solubility and emission in the near-infrared region (ex/em:585/670 nm). With the NRBE probe, the endogenous H 2 O 2 in human hepatocellular carcinoma cells BEL-7402, was detected, and the H 2 O 2 generated during the ischemia-reperfusion of the cells was imaged. These results show that NRBE can be applied for real-time detection of H 2 O 2 in biological systems. Unlabelled Image • A novel Nile red-based fluorescent probe NRBE was designed and synthesized for H 2 O 2 detection. • The probe has good selectivity, high sensitivity, good water solubility and emission in the near-infrared region. • The probe can be applied for real-time detection of H 2 O 2 in biological systems. [ABSTRACT FROM AUTHOR]

Strongly blue fluorescent N-doped carbon dots (CDs) were synthesized by using citric acid (CA) as the carbon source and diethylenetriamine (DETA) as the nitrogen source using a one-step hydrothermal method. Several synthetic parameters, including the molar ratios of initial starting materials, the temperature and time of hydrothermal reaction, were investigated and optimized. The range and average value of the diameters of the resultant CDs were 1.2-4.0 nm and 2.3 nm, respectively. The synthesized CDs display fluorescence with excitation/emission maxima of 391/438 nm and a quantum yield of 58%. Fluorescence is quenched by Co(II) ions, and this effect was exploited to design a method for determination of Co(II) in water and to image it in living HeLa (cervical carcinoma) cells. The limit of detection and linear range of Co using the synthesized CDs as fluorescence probe are 0.4 μmol·L and 0-90 μmol·L, respectively. Due to the selective and sensitive response of Co, the CDs possess potential applications in biological labeling for the demands such as monitoring the distribution of vitamin B-12 or other cobalt-containing medicines in cells or organisms . [ABSTRACT FROM AUTHOR]

In this work, two novel fluorescence probes, named as RBQ1 and RBQ2, were designed and synthesized based on rhodamine B lactam. RBQ1 was employed for sensitive fluorometric sensing of H + in the pH range of 2–4. Since RBQ1 exhibits color responses toward Cu 2+ , it was also employed for sensitive detection of Cu 2+ by photoelectric colorimetry. By using RBQ1 as the fluorescence probe, the detection limit of Cu 2+ obtained was 0.0365 μmol L −1 . RBQ2, with a similar chemical structure to RBQ1, also shows obvious fluorescence responses to H + , but no response to any metal ions. By using H + and Cu 2+ ions as chemical inputs and fluorescence or absorbance as outputs, a novel dual-mode molecular logic gate was constructed with RBQ1. [ABSTRACT FROM AUTHOR]

A water-soluble fluorescence probe (TF) derived from fluorescein has been developed. This probe can be used to detect ClO − and Cd 2+ under physiological condition based on oxidation and coordination reactions, exhibiting almost 64-fold and 4-fold fluorescence enhancement. The experimentally observed changes in the structure and electronic properties of the probe in the presence of ClO − and Cd 2+ were modeled by density functional theory (DFT) and time-dependent density functional theory (TDDFT) computational calculations. Moreover, the present probe was successfully applied to the fluorescence imaging of ClO − and Cd 2+ in living cells. [ABSTRACT FROM AUTHOR]

Thyroid cancer always appears insidiously with few noticeable clinical symptoms. Due to its limitations, conventional ultrasound imaging can lead to missed or misdiagnosed cases. Surgery is still the primary treatment method of thyroid cancer, but removal of surrounding healthy tissues to minimize recurrence leads to overtreatment and added patient suffering. To address this challenge, herein, a nitroreductase (NTR) fluorescent probe, Ox-NTR, has been developed for detecting thyroid cancer and tracking the surgical removal of thyroid tumors by fluorescence imaging. The conjugated structure of oxazine 1 was disrupted, significantly reducing the issue of high background signals, thus effectively achieving low background fluorescence. Under hypoxic conditions, the nitro group of Ox-NTR can be reduced to an amine and subsequently decomposed into oxazine 1, emitting intense red fluorescence. Ox-NTR has a low detection limit of 0.09 μg/mL for NTR with excellent photostability and selectivity. Cellular studies show that Ox-NTR can effectively detect NTR levels in hypoxic thyroid cancer cells. Moreover, the ability of Ox-NTR of rapid response to thyroid cancer in vivo is confirmed by fluorescence imaging in mice, distinguishing tumors from normal tissues due to its superior low background fluorescence. Utilizing this fluorescence imaging method during surgical resection can guide the removal of tumors, preventing both missed tumor tissues and accidental removal of healthy tissue. In summary, the novel Ox-NTR offers precise detection capabilities that provide significant advantages over traditional imaging methods for thyroid cancer diagnosis and treatment, making it a valuable tool to guide tumor removal in surgical procedures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, a novel phenoxazine-based fluorescent probe BPO - N 3 was developed to detect H 2 S. The results showed that the probe had high selectivity and sensitivity toward H 2 S, and its detection mechanism was based the ratio between green and red fluorescence signals; its detection limit was as low as 30 nM. The fluorescent imaging experiments further showed that the probe BPO - N 3 could successfully detect endogenous and exogenous H 2 S in living cells. This probe can be used as a powerful tool for in-depth study of H 2 S function in various physiological processes. Unlabelled Image • A novel phenoxazine-based fluorescent probe BPO-N 3 was developed to detect H 2 S. • Linear response (0.1 to 20 μM), high selectivity and sensitivity (LOD = 30 nM) were observed. • The probe BPO-N 3 could successfully detect endogenous and exogenous H 2 S in living cells. [ABSTRACT FROM AUTHOR]

Herein we report a new carbazole-benzo[e]indolium dye (CEBI) as a ratiometric fluorescent and chromogenic probe for sulfite (SO 3 2− ) detection based on intramolecular charge transfer (ICT) mechanism. Upon treatment with SO 3 2− , the probe CEBI displayed a remarkable fluorescence ratiometric response (∼560-fold fluorescenc enhancement) together with a color change from red to weak red and a large shift (135 nm) in emission wavelength. The experimentally observed changes in the spectral features of the probe upon addition of SO 3 2− were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI–MS), proton nuclear magnetic resonance ( 1 H NMR), and time-dependent density functional theory (TDDFT) calculations. We found a linear relationship between the ratio of fluorescence intensities at 465 nm and 600 nm ( F 465 /F 600 ) and SO 3 2− concentration over the range of 0–40 μM with a detection limit of 0.025 μM. Moreover, the novel probe demonstrated fluorescence imaging of SO 3 2− in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

Herein, we report a novel Schiff base “turn-on” fluorescent and chromogenic probe N′-(3-(benzo[d]thiazol-2-yl)-2-hydroxybenzylidene)-4-(dimethylamino)-benzohydrazide (BHDB) for CN − detection under physiological pH, based on nucleophilic reaction of imine ( CH N ) and CN − , exhibiting almost 66-fold fluorescence increase and a remarkable color change from colorless to yellow. The experimentally observed changes in the spectral properties of the probe upon addition of CN − were systematically studied using high resolution electrospray ionization mass spectrometry (HR-ESI-MS), proton nuclear magnetic resonance ( 1 H-NMR), and time-dependent density functional theory (TDDFT) calculations. Using the fluorescence spectra changes, we found a detection limit for CN − of 0.15 μmol L −1 , far lower than the maximum permissive level of CN − (1.9 μmol L −1 ) in drinking water recommended by World Health Organization (WHO). Moreover, the novel probe demonstrated fluorescence imaging of CN − in living cells and zebrafish, suggesting its potential in clinical diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • MnCo 2 O 4 /3DNG catalyst was prepared by hydrothermal method using 3DNG as support. • 3DNG with hierarchical porous structure possessed enrich the defects and expose more active sites. • MnCo 2 O 4 /3DNG with hierarchical porous structure contributed to improve mass transfer. • MnCo 2 O 4 /3DNG demonstrated excellent ORR activity and higher durability than 20% Pt/C. We designed and synthesized spinel MnCo 2 O 4 nanoparticles supported on three-dimensional nitrogen-doped graphene (NG) with interconnected hierarchical porous nanostructure, in which polymer (2, 5-benzimidazole) (ABPBI) was used as the nitrogen precursor and the carbon precursor. Unique properties of ABPBI including nitrogen-rich aromaticity and rigid plane molecule were conductive to form NG structures through the pyrolysis dehydrogenative and carbonization. The as-prepared MnCo 2 O 4 -3DNG with interconnected hierarchical porous graphene structure possessed enriched defects and more exposed active sites, accelerating mass transport and facilitating diffusion kinetics for better catalytic ORR performance. MnCo 2 O 4 -3DNG exhibited a higher half-wave potential (0.85 V vs RHE) than 20 wt% Pt/C (0.83 V vs RHE). Moreover, the accelerated durability test and i-t chronoamperometry of MnCo 2 O 4 -3DNG revealed more excellent durability than 20 wt% Pt/C. The electrochemical tests results demonstrated that MnCo 2 O 4 -3DNG was promising as a cost-effective non-noble metal catalyst for ORR in fuel cell technology. [ABSTRACT FROM AUTHOR]

Halogenated pyridin-2(1H)-ones are facile and efficiently synthesized via one-pot Vilsmeier cyclization of readily available ketene-N,S-acetal derivatives (IV). [ABSTRACT FROM AUTHOR]