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Near-infrared (NIR) aggregation induced-emission luminogens (AIEgens) circumvent the noisome aggregation-caused quenching (ACQ) effect in physiological milieu, thus holding high promise for real-time and sensitive imaging of biomarkers in vivo. β-Galactosidase (β-Gal) is a biomarker for primary ovarian carcinoma, but current AIEgens for β-Gal sensing display emissions in the visible region and have not been applied in vivo. We herein propose an NIR AIEgen QM-TPA-Gal and applied it for imaging β-Gal activity in vitro and in ovarian tumor model. After being internalized by ovarian cancer cells (e.g. , SKOV3), the hydrophilic nonfluorescent QM-TPA-Gal undergoes hydrolyzation by β-Gal to yield hydrophobic QM-TPA-OH , which subsequently aggregates into nanoparticles to turn NIR fluorescence "on" through the AIE mechanism. In vitro experimental results indicate that QM-TPA-Gal has a sensitive and selective response to β-Gal with a limit of detection (LOD) of 0.21 U/mL. Molecular docking simulation confirms that QM-TPA-Gal has a good binding ability with β-Gal to allow efficient hydrolysis. Furthermore, QM-TPA-Gal is successfully applied for β-Gal imaging in SKOV3 cell and SKOV3-bearing living mouse models. It is anticipated that QM-TPA-Gal could be applied for early diagnosis of ovarian cancers or other β-Gal-associated diseases in near future. • A near-infrared AIEgen QM-TPA-Gal was designed and synthesized for the first time. • QM-TPA-Gal presented highly sensitive and selective response to β-Gal in vitro, with a limit of detection (LOD) of 0.21 U/mL. • QM-TPA-Gal was successfully applied for β-Gal imaging in vivo with superior sensitivity, specificity, and biosafety. [ABSTRACT FROM AUTHOR]

Nitroreductase (NTR) is overexpressed in hypoxic tumor cells, which is closely related to inflammation, tumorigenesis, tumor invasion and metastasis. Therefore, developing fluorescence probes for detecting intracellular NTR sensitivity has great significance for diagnosis and treatment of tumors. Therefore, we designed a novel fluorescent probe (Pro-CN) based on julolidine skeleton for the detection of NTR. The probe could discriminate rapidly NTR from other biological species like sulfhydryl compounds and some ions. Meanwhile, a fine linear relationship between fluorescence intensity of the probe and NTR consistence has been observed with a very low detection limit of 4.4 ng/mL. In addition, Pro-CN was successfully applied in imaging endogenous NTR in Hela cells and living zebrafish. The excellent performance of the probe makes it have great potential for monitoring NTR in complex biological systems, and it also provides the possibility of its application in human health, disease diagnosis and treatment. [Display omitted] • Probe Pro-CN exhibits a turn-on fluorescence for sensing NTR. • Pro-CN is highly sensitive to sense NTR with a very low detection limit of 4.4 ng/mL. • Pro-CN was successfully applied for imaging endogenous NTR in living Hela cells and zebrafish. [ABSTRACT FROM AUTHOR]

[Display omitted] • The new probes with AIE characteristic for cell imaging. • The probe has high sensitivity in the presence of solvent shielding effects. • The probe has good reversibility for environmental testing and could be recycled. A new fluorescent probe TPA-DAP with aggregation-induced emission (AIE) characteristic based on 2,6-pyridinedicarboxylic acid was synthesized for the detection of paramagnetic ions (Cu2+, Co2+, Ni2+). In the DMF/PBS (5:95, v/v, pH = 7.40) solvent mixture, the fluorescence intensity exhibited a notable enhancement of over 3-fold when compared to DMF alone. Concurrently, fluorescence quenching phenomena were observed in the presence of Cu2+, Co2+, and Ni2+, with corresponding detection limits measured at 56.4 nM, 22.4 nM, and 26.5 nM, respectively. These detection limits were found to be lower than the prescribed thresholds for Cu2+ in Class I groundwater and Co2+, Ni2+ in Class III groundwater, multi-functional detection was possible. The coordination constants were 9.07 × 105, 3.63 × 105 and 5.69 × 105, respectively. However, in the DMSO system, the probe will be highly selective in the presence of solvent shielding effects. The probe showed more than 10-fold enhancement of fluorescence intensity in DMSO/Tris-HCl (5:95, v/v, pH = 7.00) compared to DMSO and specific detection of Cu2+ with a detection limit of 36.7 nM and a coordination constant of 4.35 × 105, and was cyclically detectable in the presence of EDTA. TPA-DAP was applied for the detection of Cu2+ in actual water samples and showed good biocompatibility and recyclability, making it suitable for water testing and test paper experiments, and also for a wide range of applications in the identification of Cu2+, Co2+, Ni2+ and other bioassays in cells and zebrafish. Solvents could be selected according to actual test requirements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two rhodamine derivatives (L-Et and L-Pr) were developed without imine bond to avoid hydrolysis for Al3+ sensing with high selectivity. • There were significant increments in fluorescence at 555 nm and absorbance at 530 nm of with Al3+. • LOD values for Al3+ were determined ∼1.0 nM. • Both of these probes were used to image the cation in C6 cells. To address limitations like susceptibility to hydrolysis of an imine bond and low selectivity of rhodamine based chemosensors, we report here two rhodamine dyes, namely, L-Et i.e. 3′,6′-bis(ethylamino)-2′,7′-dimethyl-2-(2-morpholinoethyl)spiro[ isoindoline -1,9′- xanthen ]-3-one and L-Pr i.e. 3′,6′-bis(ethylamino)-2′,7′-dimethyl-2-(3-morpholinopropyl)spiro[ isoindoline -1,9′- xanthen ]-3-one for detection of Al3+ in 10 mM HEPES buffer in H 2 O/EtOH = 1:9 (v/v) (pH 7.4). Both the probes detect exclusively Al3+ among 16 different metal ions. The sensing ability has been achieved by noting color change (colorless to pink), increment in absorption intensity at 530 nm and fluorescence intensity at 555 nm. Opening of spirolactam ring of the chemosensors followed by complexation with Al3+ is responsible for such changes. A 1:1 complex is formed by both the probes with high association constant (1.14 × 105 M−1 for L-Et and 1.17 × 105 M−1 for L-Pr). The limit of detection values of L-Et and L-Pr towards Al3+ have been determined as 1.7 nM and 1.1 nM, respectively signifying very high sensitivity. These have been successfully applied in cell imaging studies in C6 cells. Introduction of a methylene group does not influence spectral properties vividly. As both the probes do not contain any imine bond, the possibility of hydrolysis in the presence of Al3+ has been avoided. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel NIR chemosensor BDDH based on isophorone was synthesized and characterized. • BDDH showed selectivity and sensitivity responses to Al3+ with fluorescence enhancement and color change. • The limit of detection (LOD) for Al3+ was reached the level of 10−8 M. • BDDH was applicated in identification of Al3+ in the different water samples. • BDDH was applicated in cell imaging in alive MCF-7 cells and plant imaging in soybean roots. In this paper, an isophorone-based NIR fluorescent and colormetric probe BDDH for Al3+ was synthesized and characterized, it showed highly selectivity and sensitivity through significant fluorescence enhancement and visible color change towards Al3+. The job plot confirmed that the binding ratio of BDDH with Al3+ was 1:1. Furthermore, the limit of detection (LOD) of Al3+ was determined to be 4.01 × 10−8 M. Moreover, BDDH was successfully applicated in identification of Al3+ in the different water samples, cell imaging in alive MCF-7 cells and plant imaging in soybean roots. [ABSTRACT FROM AUTHOR]

• Two thiazole-fused fluoran-based fluorescent probes for copper ions have been prepared. • The two probes show high selectivity and sensitivity for copper ions. • MTFH achieves red emission (632 nm) towards copper ions due to the methyl functionalization. • The two probes can be utilized for tracing intracellular copper ions. In this work, two thiazole-fused fluoran-based fluorescent probes 8′-(diethylamino)-2-((2-hydroxyethyl) amino)spiro[isoindoline-1,11′-xantheno[2, 1- d ]thiazol]-3-one (TFH) and (8′-(diethylamino)-2-((2-hydroxyethyl)amino)-3′-methyl-3-oxospiro[isoindoline-1,11′-xantheno[2,1- d ]thiazol]-3′-ium).BF 4 (MTFH) have been prepared for copper ions. It should be noted that MTFH achieves red emission (632 nm) compared with TFH in the presence of copper ion, which mainly can be attributed to the methylation of molecule MTFH that induced more stronger ICT effect. The two probes show selective fluorescence off-on signal changes towards copper ions with detection limits of 8.8 and 60.8 nM. Copper ion detection can be conducted in a wide pH range including the physiological pH environment. Both TFH and MTFH exhibit suitable cytotoxicity and have been used for copper ion tracing in living cells. However, no other significant improvements of MTFH in sensing performance can be observed when compared with TFH. Two thiazole-fused fluoran-based fluorescent probes have been prepared for selectively and sensitively sensing copper ions, in particular, the methyl functionalization probe achieves red emission mainly due to a stronger ICT effect. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent chemosensor (SDAF) was developed for Al3+. • The SDAF has an ultralow detection limit (28 nM) and fast response time. • DFT studies were strongly confirmed the spectroscopy results. • The SDAF was successfully used to detect Al3+ in water samples, test-kits and living cells. A new fluorescent chemoprobe (SDAF) was successfully synthesized and utilized as a sensor for the recognition of Al3+ in EtOH:HEPES (3:2, v:v, pH: 7.0) media. The SDAF depicted a selective "turn–on" response at λ em = 467 nm to Al3+ over competitive cations, and the SDAF– Al3+ complex had a reversible response with F−. The limit of detection (LOD) was found about at nano–molar level (28.0 nM), demonstrating the sensitivity of the chemoprobe toward Al3+. The binding stoichiometry of SDAF –Al3+ was investigated by TOF–MS, Job's plot, 1H NMR and 13C NMR methods and found as 1:1. The recognition mechanisms of SDAF for the detection of Al3+ were the –C = N isomerization and photoinduced electron transfer (PET) mechanisms, and they were confirmed by density functional theory (DFT) computation. Furthermore, the SDAF was successfully employed in living–cell bioimaging and cytotoxicity, it was also utilized in Smartphone, test–kit and natural spring water (recovery values; 89.01 %– 96.33 %)applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A phenothiazine coumarin based fluorescent probe (WX-Lyso) for the detection of ClO– was synthesized. • WX-Lyso displayed a low LOD (0.99 µm) and rapid responsive time to ClO– (<5 s). • WX-Lyso was proved successfully has good lysosomal-targeting and imaging abilities to ClO– in Hela cells. A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems. [ABSTRACT FROM AUTHOR]

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt 2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N′ -diethylaminocoumarin (CM(NEt 2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt 2) with β-hexosaminidase promoted generation of Rhod-CM(NEt 2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt 2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with k cat and K m values of 17 sec−1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt 2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt 2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme. [Display omitted] • Development of the sensitive and selective fluorescent probe for β-hexosaminidase. • Determination of levels of β-hexosaminidase activities in several types of cells. • Evaluation of effect of glucose concentrations in media on β-hexosaminidase activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide-based fluorescent probe DNC for sequential detection of Hg2+ and S2− was synthesized. • The detection limits of Hg2+ (8.4 nM) and S2− (5.5 nM) were significantly low. • DNC were successfully applied for sequential detection of Hg2+ and S2− in living cells and zebrafish. • DNC achieved selective and sensitive sensing toward Hg2+ and S2− on test strips. • Smartphone with RGB Color Picker was employed to analyze the different Hg2+ and S2− concentrations. Mercury ions (Hg2+) and sulfur ions (S2−), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2− is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on–off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH 2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC- Hg2+) through 2:1 binding mode. Notably, DNC- Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2− through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2− with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2− detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2− in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2− without the need for complicated device. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe DYH was fabricated and characterized. • In CH 3 CN/HEPES (7/3, v/v, HEPES 100 mM pH = 7.3), the probe DYH can continuously detect Cu2+ and S2−. • DYH has a wide linear range and low detection limit for Cu2+ (0.56 μM) and S2− (0.67 μM). • DYH was found useful for imaging of Cu2+ and S2− in living cells. In this paper, a fluorescent probe methyl(E)-2-(3-(benzo[ d ]thiazol-2-yl)-2‑hydroxy -5-methylbenzylidene) hydrazine-1-carboxylate (DYH) based on benzothiazole was designed and synthesized. The characterization involved NMR, HRMS, and crystal structure analysis. In case of the existence of other competing cations, the probe DYH showed high-affinity for Cu2+, and the resultant DYH Cu2+ showed exceptional capacity to recognize S2− in CH 3 CN/HEPES (7/3, v/v, HEPES 0.1 M, pH = 7.3). The detection limits of DYH for Cu2+ and DYH Cu2+ for S2− were 0.56 μM and 0.67 μM, respectively. It was determined that the binding stoichiometry between the DYH and Cu2+, as well as DYH Cu2+ and S2−, was 1:1 according to the job's curve. The pH of the probe and complex was stable between 4 and 10. Colorimetric experiments of the probe DYH were conducted using test paper as a carrier. Additionally, DYH was used for fluorescence imaging of Cu2+ and S2− in Hela cells with poor cellular toxicity and good cell permeability. [Display omitted] [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]

A novel NIR probe based on oxazolonaphthoimidazo[1,2- a ]pyridine-malononitrile (ONIM) conjugate linked by vinyl linkage was designed and synthesized for the detection of cyanide ion. [Display omitted] • An orange emitting sensor ONIM (712 nm) with D-π-A framework is synthesized. • The ONIM emission is retained in the solid state. • ONIM could sense cyanide ion without interference of other anions. • Sensing mechanism of cyanide sensing was confirmed by 1H NMR and DFT calculations. • Live cell imaging in human breast cancer cell MDA-MB 231 and as solid state sensor was achieved. Cyanide is undoubtedly dangerous and fast acting chemical employed in various industrial applications with toxic side effects, which raises urgent need for its monitoring. In this context, oxazolonaphthoimidazo[1,2- a ]pyridine-malononitrile (ONIM) conjugate linked by vinyl linkage was designed, synthesized and characterised by FT-IR, NMR and mass spectrometry. The developed probe has been evaluated for the colorimetric and fluorometric detection of cyanide ion. An obvious color change with unique rapid " turn-off " fluorometric response was observed within 5 s upon addition of CN– thus reflecting its better acuteness and sensitivity over other competing anions. The developed probe exhibits a detection limit of 9.54 nM which is very low in comparison to maximum permitable amount of cyanide in drinking water (1.9 µM). The probe is stable within the p H range of 2–9 and suitable for the recognition of CN– in the p H range of 7 to 10, specially at neutral p H conditions. The chemodosimetric approach based detection mechanism was authenticated by 1H NMR titration and DFT calculations. The solid state applications were established by utilising ONIM impregnated TLC plates and filter paper in cyanide recognition. The solid state emissive behaviour of ONIM offers on-spot detection of the cyanide anion. Additionally, the practicability of ONIM has been extended in live cell imaging of CN– in human breast cancer cell (MDA-MB-231), which revealed a " turn-off " fluorescence response for the probe in the presence of CN– ion. [ABSTRACT FROM AUTHOR]

The liver plays a crucial role in several important processes in the human body, including metabolism, detoxification, and immune function. When the liver experiences acute injury, it can cause significant harm and requires prompt detection. Traditional biomarkers lack specificity and cannot detect changes in real-time, making them unsuitable for monitoring pathological processes. Recent studies have shown that acute liver injury (ALI) is closely related to oxidative stress, with peroxynitrite (ONOO−) being a vital byproduct of liver metabolism and become a critical biomarker for detecting liver damage. As a result, this research developed an activatable near-infrared fluorescent probe W-3a that can be used to detect endogenous ONOO− in a mouse model of ALI induced by lipopolysaccharides (LPS). The probe has high selectivity and anti-interference ability, with a reaction time <10 min and a detection limit of 85 nM. It was successfully utilized in detecting endogenous ONOO− in cells and live imaging of ALI mice. This research developed an activatable near-infrared fluorescent probe W-3a that can be used to detect endogenous ONOO− in a mouse model of ALI induced by lipopolysaccharides (LPS). The probe has high selectivity and anti-interference ability, with a reaction time <10 min and a detection limit of 85 nM. It was successfully utilized in detecting endogenous ONOO− in cells and live imaging of ALI mice. [Display omitted] • Development of a near-infrared fluorescent probe W-3a. • W-3a has high sensitivity and selectivity for ONOO−. • Realized in vivo imaging of cells and liver-injured mice. [ABSTRACT FROM AUTHOR]

Hypochlorite/hypochlorous acid (ClO−/HOCl) is a biologically crucial reactive oxygen species (ROS), produced in living organisms and has a critical role as an antimicrobial agent in the natural defense system. However, when ClO− is produced excessively, it can lead to the oxidative damage of biomolecules, resulting in organ damage and various diseases. Therefore, it is imperative to have a straightforward, quick and reliable method for over watching the minimum amount of ClO− in different environments. Herein, a new probe TTM , containing thienothiophene and malononitrile units, was developed for exceptionally selective and sensitive hypochlorite (ClO−) detection. TTM demonstrated a rapid "turn-on" fluorescence response (<30 s), naked-eye detection (colorimetric), voltammetric read-out with anodic scan, low detection limit (LOD = 0.58 μM and 1.43 μM for optical and electrochemical methods, respectively) and applicability in detecting ClO− in real water samples and living cells. This study represents one of the rare examples of a small thienothiophene-based molecule for both optical and electrochemical detections of ClO− in an aqueous medium. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A new probe NPNB with AIE performance for dual-detection SO 2 and viscosity with two cross-talk-free emissions was developed. • NPNB shows good mitochondrial localization effect and has been applied to study the changes in SO 2 and viscosity during mitochondrial dysfunction. • NPNB has been used to detect SO 2 in food and water. Sulfur dioxide (SO 2) and viscosity play important physiological roles in organisms, and real-time detection of their content changes is critical for organisms and human health. Herein, we developed a fluorescence probe NPNB with aggregation-induced emission (AIE) performance and mitochondrial localization effect for simultaneous detection of viscosity and SO 2. NPNB can realize the efficient and specific detection of SO 2 and viscosity at different emission wavelengths with a cross-talk-free effect, respectively. NPNB showed good sensing performance against SO 2 , including fast response (<7 min), and low detection limit (8.4 nM). Bioimaging experiments indicated that NPNB has good mitochondrial targeting and can achieve cellular imaging of both exogenous and endogenous SO 2 and viscosity. Importantly, NPNB enables real-time imaging of changes in SO 2 and viscosity during mitochondrial dysfunction. Moreover, the resulting probe has been applied to detect SO 2 in food and water samples with a satisfactory recovery (84.46–105.57 %), further demonstrating its compatibility and practicality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and characterization of fluorescence receptors N1, N2 -bis(2-piperazine-1-yl) ethyl) oxalamide [OX(PIP) 2 ] and Di-(benzoyloxalohydrazide) [OX(BH) 2 ] for detecting Sn2+ and Fe3+ ions. • Absorbance and fluorescence spectral activity of the OX(PIP) 2 & OX(BH) 2 receptors for Sn2+/Fe3+ ions. • Gelation ability of receptor with various solvent. • CT-DNA binding studies with fluorescence receptors with their Sn2+/Fe3+ ions. • Investigate the antibacterial activity, anticancer activity and cell imaging properties. The development of colorimetric and fluorescence receptors N1, N2 -bis(2-piperazine-1-yl)ethyl)oxalamide [OX(PIP) 2 ] and Di-(benzoyloxalohydrazide) [OX(BH) 2 ] for the accurate and easily identified Sn2+ & Fe3+ ions respectively in DMSO/HEPES buffer (1:9, v/v, 20 μM, pH 7.3) was a success. The process of sensing entails the complexation of OX(PIP) 2 receptors with Sn2+ addition, which sets off the fluorescence 'Turn-On' mode and OX(BH) 2 displays 'Turn-Off' mode after the inclusion of Fe3+ ions. An improved linear correlation between fluorescence intensity and Sn2+/Fe3+ concentration was attained in the range of 0–20 μM, with a detection limit (LOD) of 0.6 μM & 0.013 μM respectively. The average fluorescence lifespan measurements of OX(PIP) 2 and OX(BH) 2 were determined to be 2.77 and 2.22 ns, and the average life time of 4.49 ns for OX(PIP) 2 + Sn2+ and 2.18 ns for OX(BH) 2 + Fe3+ were observed. The binding mechanisms of OX(PIP) 2 + Sn2+ and OX(BH) 2 + Fe3+ were confirmed by Fourier transform infrared analysis, NMR spectral titrations, and mass (ESI) spectral analysis. The chemosensing of OX(PIP) 2 and OX(BH) 2 has also been examined in bioimaging experiments as useful fluorescent markers for finding the source of Sn2+/Fe3+ in living cells. Significantly, receptors OX(PIP) 2 and OX(BH) 2 could distinguish Sn2+/Fe3+ ions in live cells and Sn2+/Fe3+ in human cancer cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel ratiometric peptide-based fluorescent probe DWPH was developed. • DWPH showed highly selective ratiometric response to Hg2+ and S2− in 100 % aqueous solutions. • Low detection limits for Hg2+ (24.6 nM) and S2− (23.3 nM) were obtained. • DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish. • Smartphone-assisted detection platform could achieve visual assay of different Hg2+ and S2− concentrations. A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH 2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7–11). Additionally, the complex DWPH -Hg2+ as a relay response probe could also be applied to S2− according to displacement approach. Notably, the detection limit for S2− was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg2+ and S2− were combined with the smartphone APP to obtain red–green–blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2− without expensive instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Al3+ Schiff base probe JHK was designed and synthesized. • JHK has high selectivity, high fluorescence quantum yield and low detection limit for Al3+. • JHK was successfully applied to living cells and zebrafish. A novel fluorescent probe N'-(2-hydroxybenzylidene)-indole-3-formylhydrazine (JHK) was designed and synthesized based on the condensation reaction of indole-3-formylhydrazine and salicylaldehyde. The probe JHK solution could highly selectively recognize Al3+ by the obvious fluorescence enhancement (288-fold) after adding Al3+. And the probe solution with Al3+ had a very high fluorescence quantum yield (89.29 %). The detection limit was calculated to be 1.135 nM, which was significantly lower than many reported detection limits, indicating that the probe JHK had pretty good sensitivity. The ratio of JHK to Al3+ (1:1) and the sensing mechanism were determined by Job's plot, 1H NMR spectra, FTIR spectra, ESI-MS and Gaussian calculation. The probe solution and medium-speed filter paper were successfully used to make test papers for more convenient detection of Al3+. Furthermore, the probe JHK had been successfully applied to the detection of Al3+ in real water, zebrafish and living cells. [ABSTRACT FROM AUTHOR]

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

The design of optical nanosensors based on carbon nanozymes has gained considerable interest in analyte detection. In this study, a simple and rapid fluorescence/colorimetry probe, NH 2 GQDs/o-phenylenediamine (OPD), was constructed by combining amino-functionalized graphene quantum dots (NH 2 GQDs) and o-phenylenediamine. In the presence of NH 2 GQDs/H 2 O 2 , OPD was oxidized to 2,3-diaminophenazine (DAP), giving fluorescent and colorimetric signals, which can be used to quantitatively measure H 2 O 2. Furthermore, NH 2 GQDs/OPD/ H 2 O 2 exhibited high selectivity and sensitivity for detecting ascorbic acid (AA) with a detection limit of 0.062 μM using the fluorescent method. Its selectivity for AA was ascribed to the formation of the condensation compound of DAP with dehydroascorbic acid rather than the quinoxaline path for dopamine and glucose. The colorimetric sensing system NH 2 GQDs/OPD displayed yellow in the presence of H 2 O 2 , while it changed to green upon adding AA. This sensing system was successfully applied for imaging H 2 O 2 and AA in human cervical cancer cells and onion tissues. Additionally, the flexible sensing system can be used to fabricate the logic gate "AND." The results provide a valuable method for its potential application in the biosensing, clinical medicine, and food industries. [Display omitted] • A dual optical sensing system was constructed by combining amino-functionalized graphene quantum dots and o-phenylenediamine. • The amino-functionalized graphene quantum dots exhibit high peroxidase activities. • The sensing system was used to cascade detection of H 2 O 2 and ascorbic acid in living cells. • The fluorescent mechanism is based on IFE and the formation of new fluorescent species. [ABSTRACT FROM AUTHOR]

Herein, a series of water-soluble supramolecular inclusion complexes (ICs) probes were prepared using cyclodextrins (CDs) and fraxetin (FRA) to detect nicotine (NT) with high selectivity in vitro and in vivo. The FRA/CD ICs prepared through the saturated solution method exhibited excellent water solubility, stability, and biocompatibility. A clear host-guest inclusion model was provided by the theoretical calculations. The investigation revealed that NT was able to enter into the cavities of FRA/β-CD IC and FRA/γ-CD IC, and further formed charge transfer complexes with FRA in the CD cavities, resulting in a rapid and highly selective fluorescence-enhanced response with the lowest detection limits of 1.9 × 10−6 M and 9.7 × 10−7 M, and the linear response ranged from 0.02 to 0.3 mM and 0.01–0.05 mM, respectively. The IC probes showed good anti-interference performance to common interferents or different pH environments, with satisfactory reproducibility and repeatability of response to NT. Furthermore, the potentiality of the probes was confirmed through fluorescence imaging experiments using human lung cancer cells and the lung tissue of mice. This study offers a fresh perspective for detecting NT in environmental and biomedical analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

The tertiary structures of HSA and BSA show a 76 % similarity, and the abnormal levels of HSA in body fluids can cause many diseases. Therefore, accurate quantification of HSA and effectively distinguishing HSA from BSA have significant application value in various fields. In this paper, a deep-red fluorescent probe, NITH , based on 1,8-naphthalimide, is demonstrated as a potential tool for accurately quantifying HSA and distinguishing HSA from BSA. The probe not only exhibits large stokes shift (100 nm) and low detection limit (4.61 μg/L, 0.0692 nM), but also effectively detects HSA by entering its hydrophobic cavity and emitting red fluorescence. Furthermore, NITH is capable of tracking the distribution levels of HSA within the cells through endogenous and exogenous cellular imaging. The application of NITH spans various environments such as cells, zebrafish, urine, and test strips, solidifying it as an effective tool for HSA detection. [Display omitted] • NITH has been synthesized by introducing benzothiazole sulfonate at the 3-position of 1,8-naphthalimide. • NITH can effectively distinguish HSA from BSA. • NITH can quickly identify, detect and track HSA in bioimaging. • NITH can be successfully applied in test strips, urine, cells and zebrafish imaging. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • A mitochondria-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the mitochondria of living cells. Cysteine (Cys) is of great significance in biological systems and in the process of mitochondrial function. Highly selective and specificity recognizable probes for mitochondrial Cys are still in demand. In this work, a new fluorescent probe for detecting mitochondrial Cys was developed based on a rhodamine derivative. In this probe, acrylate unit was selected as group of Cys recognition and quaternized pyridinium moiety was utilized as mitochondrial targeting group. The probe showed colorless in daylight and extremely weak fluorescence in 365 nm due to its spirolactone structure when Cys did not exist. In the presence of Cys, the probe exhibited orange in daylight and produced intensely green fluorescence in 365 nm owing to the formation of the conjugated xanthene structure. The probe exhibited specific recognition for Cys. There was an excellent linear relationship between fluorescence intensity at 540 nm of the probe and the Cys concentration from 4.0 × 10-8 to 1.0 × 10-5 mol⋅L-1. And the detection limit was estimated to be 1.57 × 10-8 mol/L. Moreover, the probe was almost non-cytotoxic, possessed targeting-mitochondria ability and could sense Cys at the cellular level. The good bioimaging ability makes the probe a potential tool for studying mitochondrial Cys in biological samples. [ABSTRACT FROM AUTHOR]

A GSH-Se nanozyme, which simultaneously possesses fluorescent and glutathione peroxidase-like activities, was prepared using a one-pot hydrothermal method. This nanozyme can be used for fluorescence-enhanced detection or imaging of CTC in food and cells. [Display omitted] • Novel GSH-Se nanozyme shows dual fluorescence and peroxidase-like activities. • Enhanced GSH-Se fluorescence detects chlortetracycline (CTC) sensitively and selectivity. • Low toxicity, GSH-Se enables real-time CTC monitoring in cells. Developing rapid monitoring methods to detect antibiotic residues in food plays an important role in safeguarding human health. This study presents the development of a novel fluorescence-enhanced detection method for chlortetracycline (CTC) using a GSH-Se nanozyme. A GSH-Se nanozyme prepared using a one-pot hydrothermal method not only possesses excellent fluorescent properties but also exhibits good glutathione peroxidase-like activity. The results show that the addition of CTC leads to a significant enhancement in the fluorescence intensity of GSH-Se, and this increase exhibits a good linear relationship with the concentration of CTC. The linear range of this method is 0.02–1 µM, and the limit of detection (LOD) for CTC was 0.02 µM. Moreover, the cell toxicity of GSH-Se is low and can be used for monitoring and imaging of CTC in cells, and satisfactory results have been obtained in the analysis of actual food samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near-infrared fluorescence probe based on dicyanomethylene-4H-pyrans was designed and synthesized. • The probe exhibited high sensitivity and selectivity to Hg2+ in ultrafast response time. • The probe can visualize Hg2+ in living HepG2 cells. Mercury ions (Hg2+) are a class of heavy metal ions that can cause serious harm to the human body due to their toxicity, fluidity, and bioaccumulation. Direct contact with Hg2+ can cause adverse effects on the human body. In addition, long-term exposure to Hg2+ can lead to extreme toxicity of enzymes and proteins in the body, disrupting the cell cycle and thus endangering human life. It is becoming increasingly important to develop a method that is reliable, stable, and sensitive for detecting Hg2+. In this study, a near-infrared "turn-on" fluorescent probe based on dicyanomethylene-4 H -pyran, DCM-Hg, was designed and synthesized to determine Hg2+ over other metal ions. Probe DCM-Hg had a detection limit (LOD) of 3.35 μM when used to detect Hg2+. The Hg2+ concentrations and the fluorescence intensities at 695 nm showed a good linear correlation. Additionally, Hg2+ in HepG2 cells was successfully visualized using the current probe. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe NBPI, utilizing cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD), was developed for selective detection of Cys-SO 2 components. • The phenothiazine structure increased the bond energy of sulfonamide, thus the probe NBPI achieved a selective response to Cys. • The probe NBPI was successfully employed for the imaging of endogenous and exogenous Cys and SO 2 in HepG2 cells. A fluorescent probe has been designed using cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD) for selective detection of Cys-SO 2 components. The probe utilizes the NBD structure to achieve specificity towards Cys and employs a reaction mechanism between the double bond of cyanine and phenothiazine with SO 3 2− to achieve selectivity towards SO 2. Importantly, the NBPI phenothiazine structure incorporates a large C-O bond energy attached to NBD, effectively eliminating interference from Hcy and ensuring highly selective response to Cys. The optimized design of the probe enables excellent linearity and extremely low detection limits for Cys-SO 2 components in vitro experiments. The probe NBPI allows separate detection of Cys-SO 2 in the presence of both components. Furthermore, the probe NBPI demonstrated successful imaging of endogenous and exogenous Cys and SO 2 in cell studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • A naphthalimide-based fluorescent probe for relay recognition of Cu2+ and S2− has been designed and synthesized. • The sensor has lower detection limit for Cu2+ and S2−. • Fluorescence behavior in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. • Intracellular fluorescence imaging in living cells were developed. A fluorescent chemosensor based on naphthalimide derivative (HL) was prepared and characterized. HL exhibited strong fluorescence emission at 528 nm, which was attributed to naphthalimide moiety, while the addition of Cu2+ almost completely quenched the fluorescence emission. However, with the addition of S2−, the fluorescence at 528 nm reoccurred remarkably. The detection limits for Cu2+ and S2− were measured to be 1.72 × 10−7 M and 2.66 × 10−7 M, respectively. As determined, the fluorescence behavior of HL in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. Moreover, confocal fluorescence imaging in HepG2 cells indicated that the HL could act as a useful fluorescent probe for intracellular Cu2+ and S2− detection with negligible cytotoxicity. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe TZ-NBD was designed and synthesized for detection of Glutathione (GSH). • The probe TZ-NBD was rapid and sensitive for GSH. • The detection limit was 0.207 μM. • The probe TZ-NBD was demonstrated imaging of GSH in HepG2 cells. Biothiols are significant biomarkers for many diseases. The selective identification of biothiols is very crucial. Herein, we combined phenothiazine and 7-nitrobenzofurazan to form a new fluorescent probe TZ-NBD, due to the difference in response of reactive sulfur species to two fluorophores for distinguishing biothiols specifically. The specificity of TZ-NBD towards biothiols was high and sensitive. Moreover, its detection limit was 0.207 μM for Glutathione (GSH). Finally, TZ-NBD was successfully applied to GSH imaging in HepG2 cells. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two novel near-infrared emissive probes were designed and synthesized for mercury ions detection. • CyHg-Cl probe exhibited high photostability, low background fluorescence and biotoxicity. • Mercury ions in living cells and real water samples were successfully monitored. Mercury sensing and imaging in the bio-system is essential for comprehending its toxicity and therapies. Based on the merocyanine scaffold, we designed and synthesized two novel near-infrared (NIR) fluorescent probes for detecting Hg2+. The release of chloro-substituted merocyanine structure on the probe CyHg-Cl enables fluorescence enhancement rapidly by introducing Hg2+. In addition, the probe CyHg-Cl exhibits NIR emission and a low detection limit of 0.59 µM. Finally, the probe CyHg-Cl was used to detect Hg2+ in live cells and real water samples. [ABSTRACT FROM AUTHOR]

A new hemicyanine-based near-infrared "off-on" recognition Cu2+ fluorescent probe NRh-NP was designed and successfully synthesized. The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. NRh-NP has high sensitivity, selectivity and a low limit of detection (33 nM as fluorescence sensor and 35 nM as UV sensor) to Cu2+. According to Job's plot and ESI-HRMS, the coordination ratio of NRh-NP to Cu2+ was 1:1. DFT theoretical calculations proved that the sensor mechanism was photo-induced electron transfer (PET). More importantly, NRh-NP has excellent membrane permeability and low cytotoxicity, which could be used not only for the detection of Cu2+ in human breast cancer cells (MCF-7), but also for imaging Cu2+ in living mice. [Display omitted] • The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. • The responses of NRh-NP toward Cu2+ were fully proved by Job's plot, ESI-HRMS and DFT theoretical calculations. • NRh-NP has high sensitivity and selectivity with detection limit as low as 33 nM. • NRh-NP can be used for Cu2+ imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

A sensitive method for the detection of β-glucuronidase was established using functionalized carbon dots (β-CD-SiCDs) as fluorescent probes. The β-CD-SiCDs were found to be obtained through in situ autopolymerization by mixing the solutions of methyldopa, mono-6-ethylenediamine-β-cyclodextrin and N -(β-aminoethyl)-γ-aminopropyltrimethoxysilane at room temperature. The method has the characteristics of low energy consumption, simple and rapid. β-CD-SiCDs exhibited green fluorescence at 515 nm emission with a quantum yield of 7.9 %. 4-nitrophenyl-β-D-glucuronide was introduced as a substrate for β-glucuronidase to generate p -nitrophenol. Subsequently, p -nitrophenol self-assembled with β-CD-SiCDs through host-guest recognition to form a stable inclusion complex, resulting in the fluorescence quenching of β-CD-SiCDs. The linear range of β-CD-SiCDs for detecting β-glucuronidase activity was 0.5–60 U L−1 with a detection limit of 0.14 U L−1. For on-site detection, gel reagents were prepared by a simple method and the images were visualized and quantified by taking advantage of smartphones, avoiding the use of large instrumentation. The constructed fluorescence sensing platform has the benefits of easy operation and time saving, and has been successfully used for the detection of β-glucuronidase activity in serum and cell imaging. [Display omitted] • Amination induced in situ self-polymerization formation of β-CD-SiCDs without external energy. • β-CD-SiCDs can selectively recognize p -nitrophenol through host-guest recognition. • Smartphone-integrated hydrogel sensing platform was used to detect β-glucuronidase on site. • The approach is suitable for detecting β-glucuronidase in serum and bioimaging in cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescence proe for Hg2+ was developed based on aggregation induced emission. • The probe exhibited a limit of detection of 22 nM and a fast response time. • The mechanism of the probe is based on the Hg2+ reaction induced solubility decrease, resulting in activated fluorescence due to aggregation induced emission. • The probe can be used for imaging of Hg2+ in live cells with fast response. Mercury ions (Hg2+), as one of heavy transition metals (HTM), is a highly toxic metal that is hazardous to human health. Here an aggregation-induced emission (AIE) fluorescent probe is designed for the highly sensitive and selective detection of Hg2+. The probe is engineered with a tetraphenylethene (TPE) derivative as the fluorophore and thiopropionic acid as the site of recognition for Hg2+. Due to the different solubilities of the probe AIE-COOH and its corresponding product after reaction with Hg2+. The probe demonstrates a maximum detection limit of 22 nM and a fast response time of ∼100 s. Simultaneously, AIE-COOH exhibits outstanding detectivity and hypersensitivity for the detection of Hg2+ in aqueous solutions. These characteristics demonstrate that AIE-COOH hold a great potential in environmental, food and biological systems. Moreover, we have also successfully applied it to Hg2+ fluorescence imaging in in living cells. [ABSTRACT FROM AUTHOR]

The article highlights a quinoline-based probe for the detection of Cd2+ over other metal ions with a nanomolar level detection limit. Both DFT and TD-DFT studies were carried out to explore the sensing mechanism as well as the theoretical electronic spectra. The utilization of the probe in real-life applications has been investigated in live cells. [Display omitted] • A quinoline-based probe for the detection of Cd2+ in near-aqueous medium. • Binding mode is confirmed by single crystal XRD analysis. • Nanomolar detection limits of Cd2+. • DFT and TD-DFT analysis of both ligand and its Cd2+ complex. • Positive response towards bioimaging in live RAW 264.7 cell line. The present investigation highlights a quinoline-based small molecule probe (DEQ) for the detection of Cd2+ among other metal ions in near-aqueous media. The probe DEQ and its Cd2+ complex (DEQ-Cd) have been synthesized and characterized by all possible spectroscopic methods. The weakly emissive DEQ showed its strong emission in the presence of Cd2+, which is attributed to the photoinduced electron transfer (PET) along with the chelation-enhanced fluorescence (CHEF) mechanism. The 1:1 binding mode between ligand and Cd2+ is confirmed by single crystal XRD analysis, which is further supported by Job's plot and HRMS. The detection limit of the probe to recognize Cd2+ was found to be as low as 89 nM. Furthermore, DEQ can act as a reversible fluorescence probe with the off-on-off mechanism by the alternative addition of Cd2+ and EDTA. DFT and TD-DFT studies exposed the proposed mechanism after Cd2+ insertion and the obtained results for electronic spectra are in line with the experimental results. The response towards pH was quite interesting and allowed us to study its application in live cell imaging. With all the positive results, the proposed ligand DEQ can be used as a potential probe for the detection of Cd2+ in real-life applications. [ABSTRACT FROM AUTHOR]

A protein structure-dependent probe (OTB) for human serum albumin (HSA) was designed. Molecular simulation were used to assist probe design. OTB exhibited favorable selective HSA sensitivity and strong HSA binding ability. As a cationic molecule, OTB could form a stable amphipathic complex with water-soluble pillar [5]arene (WP5). More interestingly, the WP5-OTB complex possessed better HSA responsiveness and stronger HSA binding ability than OTB. The detection limit (3σ/k) of WP5-OTB towards HSA was determined to be 0.33 μM. WP5-OTB complex possessed excellent anti-interference ability in the selective recognition of HSA. Common commercial drugs, fluorescent amino acids, and fatty acids had almost negligible effect on the HSA responsiveness of the complex. The WP5-OTB complex self-assembled into supramolecular fluorescent probe in aqueous solution, and the supramolecular probe possessed favorable HSA-induced bioimaging property, pH-sensitive drug delivery property, and photodynamic activity. [Display omitted] • A cationic ICT probe OTB was designed by fully considering its interaction with HSA. • OTB exhibited favorable serum albumin sensitivity and strong HSA binding ability. • The WP5-OTB complex possessed better HSA responsiveness and binding ability than OTB. • The WP5-OTB complex self-assembled into supramolecular fluorescent probe in solution. • The supramolecular probe had good bioimaging and chemo-photodynamic therapy properties. [ABSTRACT FROM AUTHOR]

Autocatalytic biocircuit are powerful tools for analysing intracellular biomarkers, but these tools are constrained by limitations in amplification capacity and intracellular delivery efficiency. In this work, we developed a DNAzyme-based dual-feedback autocatalytic exponential amplification biocircuit sustained by a honeycomb MnO 2 nanosponge (EDA2@hMNS) for live-cell imaging of intracellular low-abundance microRNAs (miRNA). The EDA2 biocircuit comprises a blocked DNAzyme (b -DNAzyme), a Fuel strand and a Substrate strand. In the EDA2 biocircuit, target miRNAs are recycled and feedback for rounds of DNAzymatic amplification, and the DNAzymatic reactions continuously generate target miRNA analogues for dual-feedback to achieve multiple parallel cascade DNAzymatic reactions that improve amplification capacity substantially. In addition, the hMNS ensures high loading and delivery efficiency of biocircuit probes into living cells and also provides sufficient Mn2+ DNAzyme cofactor from in situ decomposition by intracellular glutathione (GSH). The EDA2@hMNS realized a detection limit of 17 pM, which is 288-fold lower than the b -DNAzyme lacking the DNAzymatic amplification. These results demonstrate the great promise for this critical tool in analysing low-abundance biomarkers and cancer diagnostics. [ABSTRACT FROM AUTHOR]

Esterase serves as a crucial biomarker for the diagnosis of tumors due to its overexpression in cancer cells. Ratiometric fluorescent probe has the advantage of having two distinct emission wavelengths, which allows for the elimination of the effects of light intensity and optical path length by using the fluorescence intensity ratio between the two emission wavelengths. In this work, a novel near-infrared (NIR) fluorescent probe P 1 for ratiometric monitor esterase activity was developed. Compared with ordinary ratiometric probes, both emission wavelengths of this probe are in the NIR region, which can effectively eliminate various fluctuations and blurriness in image contrast and achieve precise quantitative analysis. P 1 itself shows a fluorescence emission at 717 nm. After incubated with esterase, a new emission peak at 822 nm emerged due to esterase's catalysis, and the fluorescence intensity at 717 nm steadily decreased, which achieved the highly sensitive detection of esterase with a detection limit calculated as 0.25 mU/mL. What's more, P 1 showed high selectivity for esterase and was successfully applied for biological imaging in living cells and in vivo. [Display omitted] • A ratiometric fluorescent probe for the determination of esterase was developed. • Both of the two emissions before and after incubation with esterase were located in NIR region. • The probe shows fast response, high selectivity and high sensitivity for esterase. • The probe showed a linear relationship for esterase in 0–100 mU/mL with a LOD of 0.25 mU/mL. • The probe was successfully applied for biological imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel open-type NIR fluorescent probe was reported for the detection of PhSH. • The probe shows high sensitivity and selectivity to thiophenol. • Probe shows a large Stoke shift and significant fluorescence enhancement. • Probe has been applied to the detection of PhSH in living cells and water samples. In this study, a NIR fluorescent probe based on ICT principles was developed for the detection of phenylthiophenol. An excellent fluorescent mother nucleus is constructed with tricyano groups, and benzenesulfonate was introduced as a specific recognition site for thiophene, which can be used for rapid detection of thiophenol. The probe has a significant Stokes shift (220 nm). Meanwhile, it had rapid response to thiophene and high specificity. The fluorescence intensity of the probe at 700 nm showed a good linear relationship with thiophene concentration in the range of 0 to 100 μM, and the detection limit was as low as 45 nM. The probe had also been successfully applied to the detection of thiophene in real water samples. MTT assay showed low cytotoxicity and excellent fluorescence imaging in live cells. [ABSTRACT FROM AUTHOR]

SO 2 , the fourth endogenous gaseous signaling molecule, plays an important role in cells. Besides, SO 2 derivatives are used as preservatives in food and drinks. To understand the level of SO 2 derivatives in body and food, we developed a FRET-based fluorescent probe CPO. CPO had high energy transfer efficiency and high selectivity toward SO 2 derivatives. It could fast respond toward SO 2 derivatives in an aqueous solution (3 min) and possessed a low detection limit (68 nM). Furthermore, the SO 2 derivatives in tap water, sugar, vermicelli and cells were detected by probe CPO. In addition, probe CPO had a high colocalization coefficient (0.95) for lipid droplets. [Display omitted] • A novel FRET-based water-soluble fluorescent probe for fast response to HSO 3 − was reported. • The probe had good sensitivity and selectivity to HSO 3 −. • The probe was applied to detect HSO 3 − in tap water, food and cells. • The probe preferred to load on lipid droplets with a high Pearson's coefficient. [ABSTRACT FROM AUTHOR]

The abnormality of Cys concentration in organism could lead to a series of diseases, so its effective detection is of great importance in disease diagnosis. Here we developed a novel ESIPT fluorescent probe HBT-IDAc based on the classic ESIPT fluorophore 2-(2′-hydroxyphenyl)benzothiazole (HBT) and indanone, which could selectively and sensitively detect Cys with a large Stokes shift up to 210 nm and the detection limit to 0.89 μM. In addition, the probe exhibited good anti-interference and low cytotoxicity, and has been successfully applied to monitor Cys in cells. • A novel ESIPT fluorescent probe for selective and sensitive detection of Cys was developed. • The probe has the large stokes shift (210 nm) and good LOD (0.89 μM) in aqueous environment. • The probe exhibits low cytotoxicity and has been applied for imaging Cys in cells. [ABSTRACT FROM AUTHOR]

Mercury ion (Hg2+) is highly toxic to the environment and organisms, therefore, monitoring and quantitative detection of Hg2+ is of great significance. In this work, a new fluorescent probe TPEH that integrated tetraphenylethene (TPE) and 2-(2 ′ -hydroxyphenyl)benzothiazole was designed and synthesised. In EtOH/HEPES (2:8, v/v, pH = 7.2) solution, TPEH displays fluorescence turn on detection of Hg2+ with the advantages of swift response (<100 s), high selectivity and strong disturbance-resistant, a large Stokes shift (220 nm), and low limit of detection (81.7 nM). The sensing mechanism was proved to be Hg2+-triggered releasing of the aggregation-induced emission (AIE)-active precursor compound 2. TPEH has been successfully applied to detect Hg2+ in seafood and tea, and image Hg2+ in living cells. In addition, TPEH can be used to detect the content of Hg2+ in actual water samples with the aid of smartphone. [Display omitted] • A new AIE-based fluorescent probe TPEH for Hg2+ detection has been developed. • TPEH has the advantages of rapid response (<100 s), a large Stokes shift (220 nm), and a low detection limit (81.7 nM). • TPEH can detect Hg2+ in seafood and tea, and image Hg2+ in living cells. • TPEH can detect Hg2+ in actual water samples with the help of smartphone. [ABSTRACT FROM AUTHOR]

Herein, we designed a potent ClO− probe named ETMC , which exhibited aggregation-induced emission (AIE) characteristic in solid state and water/EtOH binary solvent. Probe ETMC exhibited an colormetric from yellow to blue and ratiometric response to ClO− with high selectivity and sensitivity, and a low detection limit of 3.66 × 10−7 M. Moreover, probe ETMC could be applied to visibly and quantitatively detect the different concentraction of ClO− in test paper. Importantly, probe ETMC could effectively detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. Also, the sensing mechanism of probe ETMC for ClO− was confirmed by FT-IR, 1H NMR, HRMS, DLS, TEM and DFT calculation. In this work, probe ETMC, which exhibited aggregation-induced emission (AIE) characteristic in solid state and water/EtOH binary solvent was developed and could effectively detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. Also, the probe ETMC has been successfully applied in visibly and quantitatively detection the different concentraction of ClO−. [Display omitted] • A fluorescent probe ETMC with AIE effect was developed, which exhibited an colormetric and ratiometric response to ClO−. • The probe ETMC could be applied to visibly and quantitatively detect the different concentraction of ClO− in test paper. • The probe ETMC could detect endogenous and exogenous ClO− in living A549 cells by an outstanding ratio signal change. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is an important endogenous gasotransmitter and has been implicated with a variety of biological processes. The development of an efficient method for monitor H 2 S fluctuations in biological systems is of great significance to understand its roles in physiological and pathological conditions. In this work, two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy for H 2 S detection with turn-on fluorescence signals were reported. Interestingly, SNARF-SeSPy exhibited excellent anti-interference via dual selenium-sulfur exchange reaction even in the presence of high concentrations of thiols, whereas SNARF-SSPy did not sense H 2 S in the same condition. Additionally, in the present of H 2 S, SNARF-SeSPy showed a rapid response and excellent sensitivity with a detection limit of 34 nM. Most importantly, SNARF-SeSPy featured low cytotoxicity and could be employed to detect and image exogenous/endogenous H 2 S in living cells and zebrafish. Image 1 • Two red-emitting fluorescent probes SNARF-SSPy and SNARF-SeSPy have been designed for efficient detection of H 2 S. • By comparing the two probes, only SNARF-SeSPy exhibited excellent anti-interference even in the presence of high concentration of thiols. • Results of imaging H 2 S in living cells and zebrafish demonstrated that SNARF-SeSPy could be employed to track exogenous and endogenous H 2 S in vitro and in vivo. [ABSTRACT FROM AUTHOR]

A multiple turn-on fluorophore (FHCS), combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule, was identified and developed based on density functional theoretical calculation. It was expected that FHCS could express exclusive fluorescent signals and improved Stokes shifts when chelating Al3+ or Zn2+. After it was synthesized and characterized in detail, it was noted that FHCS could turn-on fluorescently discriminate trace Al3+ and Zn2+ under the optimized conditions, i.e., from no-fluorescence to strong blue fluorescence for Al3+ and to green fluorescence for Zn2+ with low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. Owing to its low toxicity, FHCS was successfully applied for quantitative determination of Al3+ and Zn2+ in natural aqueous samples and toxicity evaluation of Al3+ and Zn2+ in living cells and bio-tissues with excellent linear relationships. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms in FHCS by both theoretic and experimental methods, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shifts. A multiple turn-on fluorophore, combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone into a molecule (FHCS), was identified and developed for turn-on fluorescently discriminate trace Al3+ and Zn2+ in natural aqueous, living cells and bio-tissue samples with quite low detection limits of 5.37 × 10−8 M and 7.90 × 10−8 M respectively. The action mechanisms for FHCS with Al3+ and Zn2+ were confirmed by both theoretic and experimental methods to form stable 5-member-co-6-member condensed rings between Al3+/Zn2+ and N/O atoms, which resulted in turn-on fluorescence with different dipolar moments and improved Stokes shift. Image 1 • A multiple turn-on fluorophore combining fluorescein, hydrazone, cyanuric chloride and salicylaldehyde chromone was developed. • It could turn-on fluorescently monitor Al3+ and Zn2+ in aqueous. • It was applied for cell imaging of Al3+ and Zn2+ in bio-samples. • The reaction mechanism was to form stable 5-member-co-6-member condensed rings with improved Stokes shift. [ABSTRACT FROM AUTHOR]

To explore how hypochlorous acid (HClO) affects human health, a highly sensitive, selective, and trace detection method for hypochlorite (ClO−) is crucial for determining its non-negligible function in both environment and living systems. Herein, a dicyanoisophorone-phenylboronic acid-based novel ratiometric near-infrared fluorescent probe (Probe 1) was designed for the rapid and specific detection of ClO− based on the intramolecular charge transfer (ICT) mechanism. Excess addition of HClO to the Probe 1 solution, 186-times ratio (I 652 / I 582) augment were gained. And this probe provided a colorimetric and ratiometric fluorescence response to ClO− with a high selectivity, a rapid response (within 30 s), and had an extremely low detection limit (15.7 nM). In addition, owing to the good sensing properties and low cytotoxicity of Probe 1 , it can be used to expediently visualize exogenous ClO− in HepG2 cells and endogenous ClO− in RAW264.7 macrophage cells. Furthermore, the probe was successfully used for the bioimaging of zebrafish with an acute inflammation. Thus, Probe 1 is a promising vehicle to identify the level of HClO in animals with associated diseases. A new ratiometric and colorimetric NIR fluorescent probe (Probe 1) for the specific detection of ClO− has been designed and synthesized on the basis of dicyanoisophorone-phenylboronic acid. And it was endowed with the following outstanding advantages: one-step synthesis, a long-wavelength emission, naked-eye assay, ratio fluorescent dual-channel detection, and feasibility in living cells and zebrafish. Image 1 • A new ratiometric dicyanoisophorone fluorescent Probe 1 was synthesized. • Probe 1 displays high selectivity and sensitivity to ClO− over other relevant ROS and common ions. • Probe 1 responses quickly to ClO− through distinct color change and ratiometric fluorescence variation. • Probe 1 has low cytotoxicity and is applicable for ClO− detection in living cells. • Probe 1 is successfully used for the detection of endogenous and exogenous ClO− in zebrafish. [ABSTRACT FROM AUTHOR]

Nanoscale metal-organic frameworks (NMOFs) have been widely employed in biological diagnosis and treatment system. In this work, glutathione stabilized gold nanoclusters (GSH-AuNCs) were successfully encapsulated in NMOFs and the as-obtained nanocomposites (named as AuNCs@NMOFs) showed nearly 10 times enhancement in fluorescence intensity and longer fluorescence lifetime relative to GSH-AuNCs. In addition, the fluorescence intensity of AuNCs@NMOFs was quenched by highly reactive oxygen species (hROS) due to their strong oxidation ability. Based on the fact, the nanocomposites were used for the detection of hROS with a linear range from 80 nM to 1.0 μM toward hypochlorite (as the representative of hROS). The limit of detection (LOD) was about 30 nM, which was about 30 times lower than that of GSH-AuNCs (LOD = 0.96 μM). With the features of good biocompatibility, excellent luminescence and efficient cellular uptake, AuNCs@NMOFs were successfully applied in fluorescence imaging of hROS in living cells. Au nanoclusters@NMOF nanocomposites were prepared and further applied for hROS detection with high sensitivity in living cells. Image 1 • Au nanoclusters@NMOF composites were prepared as nanoprobe for hROS through a facile in-situ growth method. • The nanoprobe was developed to detect hROS with a fast response time and nearly 30 times sensitive than AuNCs. • The nanoprobe had been successfully applied in the imaging of exogenous and endogenous hROS in living cells. [ABSTRACT FROM AUTHOR]

NAD(P)H: Quinone Oxidoreductase 1 (hNQO1) is a cytosolic flavin two-electron reductase involved in many physiological and pathological processes that is overexpressed in many cancers and recognized as a potential cancer biomarker. However, it is still challenging for highly sensitive and selective monitoring hNQO1 in living cells. Here, we developed a highly selective and ultrasensitive hemicyanine-based near-infrared (NIR) fluorescence probe (probe HCYSN) for the sensing of hNQO1 activity and discrimination of human cancer cells. The fluorescent sensing system with NIR emission is low phototoxic to normal cells but is highly selective and ultrasensitive to hNQO1 in a linear range from 0.03 μg/mL to 0.6 μg/mL with detection limit (LOD) of 4.9 ng/mL (0.49 mU/mL), which is better than most of other hNQO1 probes reported. In particular, the NIR fluorescent probe was successfully applied to distinguish various cancer cells through the different distribution of endogenous hNQO1. All the present results demonstrated that the probe HCYSN exhibited great potential for human hNQO1 assay and in vivo imaging for the early cancers diagnosis and pathological studies. Image 1 • A new hemicyanine-based near infrared fluorescence probe HCYSN was designed. • The probe exhibited low phototoxicity to normal cells due to its NIR emission. • The probe showed high selectivity and sensitivity for detecting hNQO1 with a LOD superior to that of other probes. • The sulfonic acid group of the probe greatly promoted the interaction between probe and enzyme. • The probe was successfully applied for the visual discrimination of human cancer cells. [ABSTRACT FROM AUTHOR]

Pyrene-phenylglycinol tangled ratiometric sensor (R)-1 was developed for the detection of Al3+ ion over other metal ions. Ratiometric behaviour of (R)-1 for Al3+ ion explained through monomer emission and excimer quenching leads to avoiding the π-π interactions of bis-pyrene rings. Pull-push to push-pull binding mechanism is successfully explained by DFT and sensing of Al3+-ions demonstrated in living cells. The LOD of (R)-1 for Al3+ downs to nanomolar concentrations which is lower than the allowed concentration of drinking water set by the (World Health Organization) WHO. Image 1 • Probe (R)-1 selectively detects Al3+-ion via ratiometric approach and detection limit upto nanomolar range. • Pull-push to push-pull binding mechanism is supported by fluorimetry and DFT studies. • Probe (R)-1 act as a reversible ratiometric sensor for Al3+ ion in the presence of EDTA. • Sensing behaviours (R)-1 to Al3+ ion successfully applied into living cell imaging studies. [ABSTRACT FROM AUTHOR]