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Water-soluble Mn2+ doped CsPbCl 3 nanocrystals coating by 6-aminocaproic acid (ACA) ligand were prepared by a simple ligand assisted reprecipitation method at room temperature. The CsPbCl 3 :Mn2+/ACA nanocrystals were almost cubic phase and had mean size of about 10 nm. Due to the coating and passivation of ACA, the CsPbCl 3 :Mn2+/ACA nanocrystals retained the initial fluorescence intensity of 20% after being dispersed in deionized water for 20 days. The orange LED device based on CsPbCl 3 :Mn2+/ACA nanocrystals were prepared with excellent luminescence properties. In the cytotoxicity test, even if the MCF-7 cells were cultured for 24 h at the concentration of CsPbCl 3 :Mn2+/ACA nanocrystals as high as 160 μg·ml−1, the cell survival rate was still 70%. Confocal fluorescent cell imaging results showed that the nanocrystals had remarkable fluorescent cell imaging effect even after 24 h. The synthesized CsPbCl 3 :Mn2+/ACA nanocrystals have nice water solubility, good water stability, low cytotoxicity and highly luminescence properties, and have great application potential in the field of orange LED and fluorescent probes. [ABSTRACT FROM AUTHOR]

Native broken-rice starch was used to create starch nanoparticles (StNPs) with particle sizes ranging from 100 nm to 800 nm. The fluorescent isothiocyanate poly- l -lysine StNPs (FITC-PLL-StNPs) were created in two steps. First, the StNPs were electrostatically modified by poly- l -lysine (PLL) molecules rich in amino acids. Second, fluorescein isothiocyanate reacted with some amino groups on PLL molecules (FITC). Fluorescence spectrophotometry was used to determine the degree of substitution (DS) and fluorescent properties of fluorescent starches. The study found that FITC-PLL-StNP-200 has higher fluorescence stability, more phagocytic cells, and a better and clearer fluorescence detecting effect than FITC-PLL-St, FITC-PLL-StNP-100, FITC-PLL-StNP-400, and FITC-PLL-StNP-800. The biological evaluation results showed that FITC-PLL-StNP-200 did not affect the viability of HeLa cells at the lysosome labeling concentration. These findings suggest that FITC-PLL-StNP-200 has strong and stable fluorescence, indicating that FITC-PLL-StNP-200 can be used as a fluorescent probe and lysosome marker in a variety of applications, particularly in biomedicine. [Display omitted] • Fluorecent starch nanoparticles (StNP) were synthesized. • FITC-PLL-StNP-200 has clearer fluorescence detecting effect. • FITC-PLL-StNP-200 has higher phagocytic amount of Hela cells. • FITC-PLL-StNP-200 is safe and possesses excellent biocompatibility. [ABSTRACT FROM AUTHOR]

Mitochondrial viscosity and mitochondrial membrane potential (MMP) are vital parameters for reflecting mitochondrial conditions and they are closely correlative in various biological events. Accordingly, simultaneous detection of mitochondrial viscosity and MMP is imperative for elucidating their interactions, further exploring the mechanism of diseases, and investigating numerous pathological procedures. However, such profound research remains a big challenge due to the lack of high-performing single fluorescent probes capable of simultaneously visualizing of these two parameters. In this study, we developed a new kind of fluorescent carbon dots (CDs) that can successfully realize simultaneous monitoring of mitochondrial viscosity and MMP in living cells. The fluorescence of CDs can be specifically turned on as the viscosity of solvents increases from 0.89 to 945 cP. Meanwhile, the CDs accumulate in mitochondria under normal MMP conditions, switch to exist in both mitochondria and nucleoli under reduced MMP, and present only in nucleoli with the vanishment of MMP. Thus, various MMP situations can be easily differentiated through the changed spatial distributions of CDs. More importantly, based on the developed CDs, an increased mitochondrial viscosity accompanying a decreased MMP was simultaneously tracked in drug-stimulated cells. We envision that the developed CDs has a great potential to be utilized as a promising fluorescent probe for mitochondrion-related biology studies. The carbon dots were elaborately designed for simultaneous determination of mitochondrial viscosity and membrane potential through their fluorescence variation and location migration from mitochondria to nucleoli. [Display omitted] • The fluorescence of Carbon Dots (CDs) was specifically turned on as the viscosity of solvents increased. • Fluctuation of mitochondrial membrane potential was visualized through migration of CDs from mitochondria to nucleoli. • An increased mitochondrial viscosity accompanying a decreased membrane potential was simultaneously monitored in cells. [ABSTRACT FROM AUTHOR]

• In this paper, we report a 1,8-naphthalimide/ triphenylamine-based fluorescent probe (TPA-NI-NO 2) for the specific detection of 4‑methoxy-thiophenol (MTP) with good selectivity among the thiophenols. • The probe can "turn on" detect MTP with the limit of detection (LOD) of 80 nM and no obvious response to relevant analytes and homologues. • The sensing mechanism was explored by HPLC experiment and the PET process was determined by density functional theory (DFT) calculations. • The Gibbs free energy (DG) analysis for the reaction between the probe and different thiophenols were obtained by the theoretical calculations to study the specificity of the probe. • The probe was successfully applied to monitor the MTP in Hela cells. Thiophenols as a series of industrial products are widely used and high toxicity to the organisms and the environment. The fluorescent probe technique offers important insights into thiophenols convenient sensing. Herein, we report a 1,8-naphthalimide/ triphenylamine-based fluorescent probe (TPA-NI-NO 2) for the specific detection of 4‑methoxy-thiophenol (MTP). The probe can "turn on" specific detect MTP with the limit of detection (LOD) of 80 nM among various relevant analytes and homologues (p -Cl-C 6 H 4 SH, p -NO 2 - C 6 H 4 SH, C 6 H 5 SH and o -CH 3 - C 6 H 5 SH). The sensing mechanism was explored by the HPLC experiment and the PET process was determined by density functional theory (DFT) calculations. In addition, the specificity of the probe was also studied by the Gibbs free energy (ΔG) analysis of the reaction between the probe and different thiophenols. The reaction between probe and MTP gives the minimum of the ΔG value (∼ -9.7280 kcal/mol) and that of other thiophenols-mediated is -2.5283 to -5.8911 kcal/mol, which proves the thermodynamic chemical equilibrium can optimize the design of reaction-based fluorescent probes with excellent specificity. At last, TPA-NI-NO 2 was successfully applied to Hela cells imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

The first difunctional probe H-1 for detecting ONOO− and Zn2+ at the same time showed high selectivity, good anti-interference capability, lower detect limit and short response time to them. [Display omitted] • · A new difuctional probe H-1 for ONOO− and Zn2+ detection at the same time was obtained firstly. • ·H-1 showed good selectivity and strong anti-interference ability for detecting ONOO− and Zn2+. • ·H-1 could fast response to ONOO− and Zn2+ in 15 s. • ·H-1 was used to monitor the ONOO− and Zn2+ level in living cells. Peroxynitrite (ONOO−) is one of the most significant reactive oxygen species (ROS) in living cells. Zn2+ in living cells plays an essential part in different physiological processes. The abnormal concentration of ONOO− and Zn2+ in living cells are related to many kinds of diseases, such as anemia, epilepsy, diarrhea, Alzheimer's disease, and so on. The relationship of ONOO− and Zn2+ in living cells when the relative disease occurs remains unknown. So we develop the first probe H-1 for detecting ONOO− and Zn2+ at the same time. The probe H-1 shows high selectivity, good anti-interference capability, low detection limit and short response time to ONOO− and Zn2+. When the probe was applied to detect ONOO− and Zn2+ in HeLa cells, we could observe the fluorescence changing in the green and blue channels separately without interference in real time. It has the potential to employ the relation of ONOO− and Zn2+ in some disease mechanism research. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel biotin-tagged fluorescent probe Nap-biotin-glu for in situ imaging of GGT on cell surface was developed. • The construction of the Nap-biotin-glu probe required only three steps with a simple and convenient method. • The probe shows obvious fluorescence change with high sensitivity and selectivity toward GGT. • The probe was applied to distinguish tumor tissues from normal tissues. γ-Glutamyl transpeptidase (GGT), a cell-surface enzyme, is strongly implicated in mammalian malignancy growth and migration processes including human hepatocarcinogens. However, simply and conveniently detect of GGT on the cell membrane remains highly challenging. In this study, a biotin-tagged fluorescent probe Nap-biotin-glu was developed using glutamic acid, naphthalimide, and biotin as the reaction site, fluorescent reporter, and membrane-targeting group, which required only three steps. Colocalization fluorescence imaging and immunofluorescence analysis indicated that probe Nap-biotin-glu was successfully realized in situ visualizing of GGT on the cell membrane.Owing to the significant over-expressed GGT level in tumor, the probe was successfully applied to distinguish cancer tissues from adjacent normal tissues. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ratiometric peptide-based fluorescent probe DKA with large Stokes shift (230 nm) was developed. • DKA demonstrated absorbance ratiometric and fluorescent "off-on" sensing for Hg2+ with low LOD of 13.4 nM. • DKA -Hg2+ complex was applied to sequential detect S2− with good selectivity and excellent sensitivity.. • DKA performed well in sequential detecting the distribution of Hg2+ and S2− in living cells. • DKA was used to visually and semi-quantitatively recognize Hg2+ and S2− by smartphone-assisted detection platform. In this work, a new ratiometric fluorescent probe DKA was synthesized based on the double sides of lysine backbone conjugated with alanine and dansyl groups. DKA exhibited fluorescence ratiometric response for Hg2+ with high sensitivity (13.4 nM), specific selectivity (only Hg2+), strong anti-interference ability (no interference), fast recognition (within 60 s) and wide pH range (5–10). The stoichiometry of binding of DKA and Hg2+ was determined to be 1:1 via Job's plot, ESI-HRMS and 1HNMR titration analysis. Subsequently, the in situ formation of DKA -Hg2+ complex was used for highly selective detection of S2− as a novel fluorescence "on–off" probe, and the lowest detection limit for S2− was 12.9 nM. In addition, DKA possessed excellent cells permeation and low toxicity, and fluorescence imaging of Hg2+ and S2− was performed in living Hacat cells. Most importantly, the digital imaging using a smartphone color recognition APP indicated that DKA could semi-quantitatively and visually detected Hg2+ and S2− without expensive equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A first dual-response probe for norepinephrine and viscosity is synthesized. • The crosstalk between the two channels is negligible. • Reducing viscosity accelerates the release of norepinephrine in depression cells. Depression is a serious mental disease that causes grievous harm to human health and quality of life. The vesicular exocytosis of noradrenaline (NE), rather than its intrinsic intracellular concentration, is more associated with depression. Based on the reports on exocytosis of NE, it is reasonable to assume that the viscosity of cells has an important effect on the release of NE. Herein, a dual-response fluorescent probe (RHO-DCO-NE) for detecting NE and viscosity was designed and synthesized. The probe can simultaneously detect NE concentration and viscosity level with negligible crosstalk between the two channels. We utilized the probe to study the effect of viscosity changes on the NE release of PC12 and the corticosterone-induced PC12 cells. The experiment data revealed that the decrease in viscosity level can accelerate the release of NE of depression cell models. The finding provides new insight into the study of the pathological mechanisms of depression. [ABSTRACT FROM AUTHOR]

A phenolato-thiazole based small molecule is synthesized and structurally characterized for the naked-eye detection of carbonate anion (LOD, 0.18 µM) in physiological conditions. The new colorimetric probe shows selective reversible chemosensory activity through the formation of a stable adduct (L∙CO 3 2). The cell uptake of the probe is mainly in the cytoplasm. [Display omitted] • A novel "turn-on" chemosensor fluorescent probe (L) for aqueous CO 3 2– anion is reported with crystal structure. • The 1:1 adduct L∙CO 3 2– (Binding constant, K = 1.6 x 10–7 M−1) in the quinonoid form is established by DFT/TDDFT. • The goodness of sensor activity concerns the selectivity, reversibility, and regeneration. • Selectivity with LOD (0.18 µM) in the pH range of 4 to 8. • MTT assay and cell uptakes and degradation of the probe through image study. A new phenolate-thiazole derivative (L) has been synthesized and structurally characterized. The chemo-sensing activity of L is detected by the naked eye for the aqueous carbonate anion in the pH range of 4 to 8. The selective 'turn-on' fluorescence occurs through the formation of a stable intermediate L∙CO 3 2–(1) following the PET mechanism. The limit of detection (LOD) is found 0.18 µM based on the absorbance-based assay. The quinonoid form of bromophenol unit binds strongly with CO 3 2– through thiazole nitrogen and hydrazinic nitrogen. Further, the selective holding of CO 3 2– anion over other planar tetranuclear anions (e.g., SO 3 2–, NO 3 –) happens with several intra and intermolecular hydrogen bonds as envisaged by the DFT/TDFT study. The formation mechanism of L∙CO 3 2– is proposed based on experimental and theoretical studies. The biological experiments (MTT and cell imaging) reveal the non-cytotoxicity nature of L and the biocompatible uptake of L mostly in the cytoplasm at physiological pH. [ABSTRACT FROM AUTHOR]

[Display omitted] • The review explores the versatile capabilities of fluorocolorimetric probes developed in Dr S Velmathi's lab at NIT Trichy for analyte detection, imaging, and real-time applications. • They exhibit distinctive visual signals when interacting with specific targets, marking a significant advancement in molecular interaction analysis. • The probes cover a broad spectrum of analytes, including metal ions, anions, biomolecules, ROS, RSS, toxic agents, and nanoparticles. • The review emphasizes the profound impact of fluorocolorimetric probes on developing analytical potential. • These probes contribute to innovative imaging techniques and expand the possibilities of real-time applications. Fluorescent and colorimetric probes are gaining interest in analyte detection, imaging, and real-time applications. However, it faces several challenges in achieving high sensitivity and selectivity, maintaining a strong signal-to-noise ratio, detecting analytes at extremely low concentrations, ensuring stability under different conditions and addressing issues related to cost, accessibility and instrumentation. Additionally, ensuring biological compatibility and enabling real-time monitoring are also challenges that need to overcome. We have investigated the sensing application of probe molecules towards various analytes like metal ions, anions, biomolecules, reactive oxygen species (ROS), reactive sulphur species (RSS), toxic agents and nanoparticles performed by our group together with critically comparing with the existing reports. This featured article provides the impact of fluorescent and colorimetric probes in advancing analytical techniques, imaging and real-time applications that transcend traditional boundaries. [ABSTRACT FROM AUTHOR]

Butyrylcholinesterase (BChE) is associated with many neurodegenerative diseases, especially Alzheimer's disease (AD). Developing specific imaging tools for BChE is now highly pursued because BChE has substantially similar biochemical properties to acetylcholinesterase (AChE) but distinct roles in AD. Inspired by the BChE-catalyzed hydrolysis of specific substrates (benzoylcholine, tetracaine, and cocaine) containing benzoyl group in physiological condition, a bioinspired probe PM1 with high specificity towards BChE was designed. The docking models indicated that PM1 could easily access the active center of BChE rather than AChE, showing the significance of benzoyl group in specific recognition of BChE. The control probes PM2–5 with smaller recognition groups displayed lower specificity to BChE than PM1 , showing the high efficiency of the bioinspired design strategy. The living cells experiments showed that PM1 signals were weakened by BChE inhibitor but not influenced by AChE inhibitor, which was in contrast to the performance of probe PM2–5 , showing the specific recognition of PM1 for BChE in biological system. Moreover, PM1 has been used to study the positive correlation between BChE level and cell apoptosis for the first time, and the further study showed that Aβ deposition could induce the increase in BChE level and accompany the occurrence of cell apoptosis. Notably, PM1 was successfully traced the enhancement of BChE activity in the brain slice of AD mouse model. Such a rational approach may provide a solid basis for designing specific probes with different properties to study BChE in biosystems. [Display omitted] • Inspired by the BChE-catalyzed hydrolysis of specific substrates, a bioinspired probe towards BChE was designed. • Screening probes with different recognition groups and the docking models showed rationality of our probe. • Probe PM1 has been used to study the positive correlation between BChE level and cell apoptosis for the first time. • The study showed that Aβ could induce the increase in BChE level and accompany the occurrence of cell apoptosis. • PM1 was successfully traced the enhancement of BChE activity in the brain slice of AD mouse model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrazone based dual mode fluorescence sensor for Zn2+ ("turn-on") and Hg2+ ("turn off"). • Probe C1 selectively sense Zn2+and Hg2+ ions with their lowest detection limits 0.042 μM and 0.081 μM respectively. • The designed probe C1 was studied latent fingerprint analysis in various surfaces. • Live cell imaging studies was performed for probe C1 in presence and absence of Zn2+, Hg2+ ions. A facile Schiff base probe C1 has been developed and evaluated using 1H, 13C NMR, and mass spectroscopy. Fluorescence investigations were conducted to determine probe-sensing behavior. Probe C1 demonstrated sensitive, and selective recognition of Zn2+ and Hg2+ ions by using two distinct processes (i.e., chelation enhanced fluorescence effect and fluorescence quenching) over other cations in ACN-H 2 O (8:2, v/v). The Zn2+ and Hg2+ detection limits of 0.042 and 0.081 μM are achieved with the probe C1. C1 has a binding constant of 3.33 × 103 M−1 for Zn2+ and an emission quenching constant of 1.22 × 104 M−1 for Hg2+. A Jobs plot was used to determine the binding stoichiometry of C1 and Zn2+/Hg2+ ions ratio is 1:1. By using Zn2+/Hg2+ and EDTA additions alternately, the probe's reusability was investigated. Moreover, the probe was found to be highly cytocompatibility using an MTT assay in a mouse fibroblast cell line (NIH3T3). Further, the probe was found to visualize Zn2+ and Hg2+ ions inside the cells, indicating the potential application of the probe as an intracellular probe to detect Zn2+ and Hg2+ ions. The probe shows very good solid-state emission behavior, this motivates us to develop latent fingerprint detection and anticounterfeiting applications. [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]

Fluorescent probes have revolutionized biological imaging by enabling the real-time visualization of cellular processes under physiological conditions. However, their size and potential perturbative nature can pose challenges in retaining the integrity of biological functions. This manuscript highlights recent advancements in the development of small fluorescent probes for optical imaging studies. Single benzene-based fluorophores offer versatility with minimal disruption, exhibiting diverse properties like aggregation-induced emission and pH responsiveness. Fluorescent nucleobases enable precise labeling of nucleic acids without compromising function, offering high sensitivity and compatibility with biochemistry studies. Bright yet small fluorescent amino acids provide an interesting alternative to bulky fusion proteins, facilitating non-invasive imaging of cellular events with high precision. These miniaturized fluorophores promise enhanced capabilities for studying biological systems in a non-invasive manner, fostering further innovations in molecular imaging. [ABSTRACT FROM AUTHOR]

Emerging studies demonstrates that mitochondrial G-quadruplex (G4) may be a prospective diagnostic and therapeutic target for cancer. Fluorescent probes targeting mitochondrial G4 are crucial for in-depth research on G4 function and mechanism and developing new diagnostic techniques. Here, we report a benzothiazole derivative named ThT-E, which can be prepared with high yield through only one step of reaction. ThT-E exhibits superior detection sensitivity compared to existing probes, and also demonstrates reliable performance for in situ characterization of mitochondrial G4 in living cells. Interestingly, ThT-E has been used to differentiate tumor cells from normal cells by quantifying the formation of mitochondrial G4s, implicating that ThT-E may have wide applications in tumor diagnosis. • A benzothiazole derivative for monitoring mitochondrial G-quadruplexes. • More pronounced fluorescence enhancement in tumor cells than normal cells. • More G-quadruplex formation in tumor mitochondria. • Mitochondrial G-quadruplex as a potential cancer biomarker. • New probe tool for tumor diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Herein we constructed and synthesized turn-on fluorescent probe NSP based on simple condensation reaction. • Probe on incubating with triphosgene in presence of 1 % Triethylamine (TEA) show maximum emission at 586 nm within ≤3 s. • The probe displayed both colorimetric and fluorescence response with phosgene (0.01 ppm). • The probe-loaded paper strips, allowed for the direct visualization of phosgene vapour from household bleaching powder. • The probe detect phosgene in living cells. Phosgene is a vital industrial gas that might substantially imperil public safety in the case of an accident or terrorist attack due to its extreme toxicity and history of use as a chemical warfare agent. Herein we built a simple photoinduced electron transfer-intramolecular charge transfer based turn-on fluorescent probe for ultrafast detection of phosgene within ≤ 3 s. The probe provides low detection limit (0.01 ppm) with distinct colour and fluorescence changes only in the presence of phosgene. With the help of a readily available colour smartphone app, the probe-loaded paper strips allowed for the direct visualization and quantitative measurement of phosgene vapour. Using the probe-coated strips to detect phosgene that evolved from common household bleach. Finally, the probe was utilized to detect phosgene in living cells. [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] • The high sensitivity of the probe with a detection limit of 58 nM. • Successful detection of endogenous and exogenous CO in living cells. • Capable of detecting CO in zebrafish. • NIR probe with a high signal-to-noise ratio for imaging CO in biological samples. Carbon monoxide (CO) is a highly emitted atmospheric pollutant that can pose a serious health risk when its concentration is too high. However, endogenous CO plays an important role in maintaining human health. The development of tools capable of detecting CO in environmental samples and biological samples is therefore essential. Although CO fluorescent probes have been reported, their further applications are limited by factors such as low sensitivity and emission wavelength. Here, we have constructed a CO probe with simple structure, high sensitivity, good selectivity and near-infrared (NIR) emission characteristics. The probe uses the dicyanoisophorone derivative as fluorophore and connects allyl moiety as the reaction site. After the response, the intramolecular charge transfer (ICT) process turns on and releases strong near-infrared fluorescence at 675 nm. The linear range of fluorescence intensity of the probe for CO concentration is 1–10 μM and the detection limit is as low as 58 nM. The high sensitivity and NIR emission give the probe excellent imaging of cellular exogenous and endogenous CO. Moreover, the probe can also be used to image CO in zebrafish. There is reason to believe that the probe can be a powerful tool for detecting CO concentrations in environmental samples and for analyzing the biological role of CO in organisms. [ABSTRACT FROM AUTHOR]

Ammonia is a common toxic gas in industrial and agricultural production, which will cause harm to the environment and human health in certain extent. Here, a novel fluorescent probe (R)- 1 based on 1,1′-binaphthol (BINOL) was synthesized for real-time, on-site and quantitative detection of ammonia. The mechanism study shows that the functional groups of –CHO and –OH on (R)- 1 interact with ammonia, which changes the electronic state of the probe molecule and excites strong fluorescence. A test strip for rapid detection of ammonia was developed, which changed from light yellow to reddish brown under natural light after interacting with ammonia, thus realizing the rapid detection and easy visualization of ammonia. Meanwhile, bioimaging experiments shows that probe (R)- 1 can detect exogenous ammonia in cells. [Display omitted] • Specific selective fluorescence recognition of ammonia. • Fast response time (300 s) and high sensitivity (0.96 ppm). • A test strip for real-time and visual detection of ammonia. • Exogenous ammonia fluorescence imaging of cells. [ABSTRACT FROM AUTHOR]

Scheme 1 Illustration of the synthetic procedure of Br-CDs-AM and the application in sensing HClO in food matrices and lysosomal imaging. [Display omitted] • Br-CDs with excellent photostability were synthesized by self-doping strategy. • Br-CDs-AM as a probe was made of Br-CD and N -aminomorpholine by substitution reaction. • HClO in milk, yogurt and meat samples were detected accurately (96.5 %–108 %). • • Br-CDs-AM can be used to locate lysosome and visualize HClO in live cells. Hypochlorous acid (HClO) is used in food preservation. However, excessive HClO can deteriorate nutritional composition of food, compromise its quality, and potentially induce various diseases. Consequently, the development of multifunctional fluorescent probes for the sensitive and selective detection of HClO is highly anticipated for food safety. In this work, we designed a nanoprobe using N -aminomorpholine (AM)-functionalized bromine-doped carbon dots (Br-CDs-AM) for sensing HClO. This nanoprobe exhibits pH stability, strong resistance to photobleaching, superior long-term photostability (12 weeks), high sensitivity (19.3 nM), and an ultrarapid response (8 s) for detecting HClO residues in food matrices with percentage recovery (96.5 %–108 %) and RSDs less than 5.34 %. In addition, extremely low cytotoxicity and outstanding biocompatibility enable the nanoprobe to be used primarily for lysosome tracking and rapidly visualizing HClO in live cells. Thus, this study provides a new pathway to design unconventional nanoprobes for food safety assessment and subcellular organelle-specific imaging HClO. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2) is a significant gas signaling molecule in organisms, and viscosity is a crucial parameter of the cellular microenvironment. They are both involved in regulating many physiological processes in the human body. However, abnormalities in SO 2 and viscosity levels are associated with various diseases, such as cardiovascular disease, lung cancer, respiratory diseases, neurological disorders, diabetes and Alzheimer's disease. Hence, it is essential to explore novel and efficient fluorescent probes for simultaneously monitoring SO 2 and viscosity in organisms. We selected quinolinium salt with good stability, high fluorescence intensity, good solubility and low cytotoxicity as the fluorophore and developed a highly sensitive ratiometric probe QQD to identify SO 2 and viscosity changes based on Förster resonance energy transfer/twisted intramolecular charge transfer (FRET/TICT) mechanism. Excitingly, compared with other probes for SO 2 detection, QQD not only identified HSO 3 −/SO 3 2− with a large Stokes shift (218 nm), low detection limit (1.87 μM), good selectivity, high energy transfer efficiency (92 %) and wide recognition range (1.87–200 μM), but also identified viscosity with a 26-fold fluorescence enhancement and good linearity. Crucially, QQD was applied to detect HSO 3 −/SO 3 2− and viscosity in actual water and food samples. In addition, QQD had low toxicity and good photostability for imaging HSO 3 −/SO 3 2− and viscosity in cells. These results confirmed the feasibility and reliability of QQD for HSO 3 −/SO 3 2− and viscosity imaging and environmental detection. We reported a unique ratiometric probe QQD for detecting HSO 3 −/SO 3 2− and viscosity based on the quinolinium skeleton. In addition to detecting HSO 3 −/SO 3 2− and viscosity change in actual water and food samples, QQD could also monitor the variations of HSO 3 −/SO 3 2− and viscosity in cells, which provided an experimental basis for further exploration of the role of SO 2 derivatives and viscosity in biological systems. [Display omitted] • A dual-function fluorescent probe was designed for detecting SO 2 and viscosity. • QQD had large Stokes shift of 218 nm and wide detection rang of 1.87–200 μM. • QQD showed high sensitivity and selectivity. • QQD achieved the dual colorimetric and ratiometric fluorescent strategy. • QQD achieved the application of foods, water samples and living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] As essential subcellular organelles, lipid droplets (LDs) are involved in various the pathophysiological processes of metabolic diseases, including fatty liver and diabetes. Therefore, detecting LDs is conducive for studying the pathogeny and the early diagnosis of associated diseases. In this work, a series of fluorescent probes L1 - L3 based on triphenylamine derivatives were designed and synthesized for tracking LDs in living cells. Due to the different terminal moieties of the three probes, L1 and L3 are aggregation-induced emission (AIE)-active, while L2 is a dual-state emission (DSE) molecule. In addition, confocal cell imaging experiments showed that probes L1 - L3 specifically target intracellular LDs sites without the post washing. Importantly, probe L3 allows real-time monitoring of the dynamic processes and changes in the number of LDs. In summary, probe L3 is an ideal probe for studying LDs-related pathophysiological processes, and this work provides more ideas for the future design and synthesis of high-performance fluorescent probes for targeting LDs. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is one of the most widespread pollutants that pose serious threats to public health and the environment. People are inevitably exposed to Hg via different routes, such as respiration, dermal contact, drinking or diet. Hg poisoning could cause gingivitis, inflammation, vomiting and diarrhea, respiratory distress or even death. Especially during the developmental stage, there is considerable harm to the brain development of young children, causing serious symptoms such as intellectual disability and motor impairments, and delayed neural development. Therefore, it's of great significance to develop a specific, quick, practical and labor-saving assay for monitoring Hg2+. Herein, a mitochondria-targeted dual (excitation 700 nm and emission 728 nm) near-infrared (NIR) fluorescent probe JZ-1 was synthesized to detect Hg2+, which is a turn-on fluorescent probe designed based on the rhodamine fluorophore thiolactone, with advantages of swift response, great selectivity, and robust anti-interference capability. Cell fluorescence imaging results showed that JZ-1 could selectively target mitochondria in HeLa cells and monitor exogenous Hg2+. More importantly, JZ-1 has been successfully used to monitor gastrointestinal damage of acute mercury poisoning in a drug-induced mouse model, which provided a great method for sensing Hg species in living subjects, as well as for prenatal diagnosis. [Display omitted] • An activated probe JZ-1 for fluorescent detecion of Hg2+ was devised. • JZ-1 has dual NIR excitation and emission analysis wavelengths (both > 700 nm). • JZ-1 has a rapid response time and outstanding detection limit. • It was successfully used to in a drug-induced mouse of acute mercury poisoning. [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]

• CM exhibit "Turn-On" blue fluorescence response for Ca2+ in solution, which is free from interference of co-existing cations. • "Tyndall Effect" can be observed during chelation, blue emissive nanowires induced by aggregation were investigated. • The molecular docking result reveals CM can bind with receptor 1A of melatonin via hydrogen bond. • CM and its Ca2+ complex shows good cell permeability and low cytotoxicity, their localization in organelle were studied. Due to a physiological significant role of calcium ion, it is essential to develop ways of detecting and monitor the level of Ca2+ ions in living cell. Herein, we rationally designed and synthesized a functional blue fluorescent compound CM based on amide condensation of coumarin and melatonin. Interestingly, it could exhibit an "On-OFF" fluorescence response for Ca2+ in an aqueous environment with 80-fold enhancement in bright blue emission, which is also free from interference of other co-existing cations of high concentration. A detection limit of 0.28 ppm was obtained, and the binding ratio of CM and Ca2+ is further investigated by Job's plot. After coordination of CM with calcium ion, a significant "Tyndall Effect" can be observed, and blue emissive nanowires induced by aggregation of complex of CM and Ca2+ were further investigated by Dynamic Light Scattering, analysis of Zeta potential, and confocal imaging. The molecular docking of CM with melatonin receptor 1A is also conducted. MTT assay reveals that CM ligand and the corresponding Ca2+ complex are non-cytotoxic. Moreover, CM shows good membrane permeability, and the relative cellular uptake mechanism is mainly dominated by an energy-dependent process. CM and its complex of Ca2+ can be further used as intracellular luminescent imaging probes and their localization in cell organelles is also revealed. [ABSTRACT FROM AUTHOR]

To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD. [Display omitted] [ABSTRACT FROM AUTHOR]

Mitophagy is a critical cellular self-protective mechanism involving the degradation and recycling of damaged or excessive mitochondria, which has been implicated in various diseases. In our study, we designed and synthesized two phenothiazine-based fluorescent probes, DPTZ and CMDP , specifically targeting mitochondria and lysosomes, respectively, to investigate mitophagy. H 2 S, a cell-protective agent, was chosen as the target molecule for both probes. Our findings demonstrate the selective localization of DPTZ to mitochondria and CMDP to lysosomes. Both probes exhibited rapid, selective, and highly sensitive recognition of H 2 S, enabling imaging of exogenous and endogenous H 2 S. By employing split-targeting and simultaneous detection, we were able to monitor changes in H 2 S levels in mitochondria and lysosomes, providing dynamic and visual imaging of the mitophagy processes. Upregulation of mitochondrial and lysosomal H 2 S was observed during mitochondrial autophagy. This work introduces valuable research methods and tools for investigating mitophagy, thereby enhancing our understanding of the molecular mechanisms underlying this process. [Display omitted] • Phenothiazine-based probes DPTZ and CMDP detect hydrogen sulfide. • DPTZ and CMDP target mitochondria and lysosomes for imaging in A549 cells. • Split-targeting and detection strategy reveals hydrogen sulfide fluctuations in autophagy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyanide exhibits a dual nature, serving as an industrial asset and causing an environmental threat. • The focus on cyanide detection increases as micromolar cyanide levels create fatal risks. • Colorimetric and fluorescent chemosensors offer quick, affordable, and portable detection of cyanide. • This review highlights colorimetric and fluorescent probes' significance in monitoring cyanide ions. • The survey was executed utilizing published reports from 2021 to 2023. Anions, specifically cyanide, occupy crucial roles in various biological, physiological, and industrial contexts. While cyanide is indispensable as a raw material in the synthesis of herbicides, resins, synthetic fibers, and the gold-extraction process, its widespread presence causes a significant threat to both environmental and social systems. Cyanide abundance in the environment arises not just from industrial effluents but also from the natural biological processes of fungi and algae. The dual nature of cyanide, serving both as a useful industrial component and a potential environmental hazard, highlights the importance of responsible management and regulation in its production and application. The detection of cyanide has become a matter of paramount importance due to its extreme toxicity and potential environmental contamination, where even micromolar levels can prove fatal to humans. In addressing this critical concern, researchers have focused on developing simple, inexpensive, and rapid detection methods, with chemosensors emerging as among the most promising solutions. These chemosensors rely on colorimetric and fluorometric responses, offering a synergistic combination that enhances the versatility of cyanide detection methodologies. Through novel design and synthesis, researchers have constructed a diverse range of chemosensors with tailored properties, such as high selectivity, low detection limits, and rapid response times. Especially, efforts have been directed towards making these detection systems portable and user-friendly, facilitating their practical implementation in real-world scenarios. This comprehensive review provides a focused examination of colorimetric and fluorescent probes designed for the specific and sensitive recognition of cyanide anions. Emphasizing their applicability in on-site portable strips and cellular imaging, the review aims to enhance readers' understanding of the critical need for monitoring cyanide ions in the context of human health and disease. The discussed probes are categorized into various classes, including small molecules, metal complexes, metal–organic frameworks (MOFs), macrocyclic compounds, nanomaterials, and polymer-based probes, each classified based on their structural properties and functional groups. Encompassing advancements made in the field from 2021 to 2023, the review underscores the progress achieved in developing these probes. Finally, the review addresses the potential future applications of colorimetric and fluorescent probes in detecting cyanide ions, pointing towards the evolving landscape of analytical techniques and their significance in advancing our ability to monitor cyanide levels effectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new pH-sensitive fluorescent probe 1 based on hemicyanine fluorophore is developed. • The probe can respond to pH with high selectivity and sensitivity. • The probe can solely illumine the lysosomes and detect the exogenous pH difference in live cells. • The probe can successfully monitor the pH changes during food spoilage. pH as an important parameter is closely related to many pathological processes and food freshness. In this paper, a new pH-sensitive fluorescent probe 1 based on hemicyanine dye was synthesized and used for the detection of pH in live cells and food spoilage. Under neutral and alkaline conditions, the phenolic hydroxyl group of the probe deprotonates, forming a closed spirocyclic structure and resulting in fluorescence quenching. Under acidic conditions, the probe maintains an open-loop structure and has intense fluorescence. The probe possessing good selectivity and stability can target lysosomes and visualize the exogenous pH in live cells. Furthermore, by using this probe, we successfully achieved the monitoring of pH in metamorphic process of shrimp and pork. This probe is expected to provide a good imaging tool for real-time detection of pH in live cells and food monitoring. [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]

[Display omitted] • Ratiometric fluorescent probe for detecting H 2 S. • NIR emission wavelength and high energy transfer efficiency. • Excellent sensitivity and selectivity. • Achieving the detection of exogenous and endogenous H 2 S in living cells. Hydrogen sulfide is an important signaling molecule which plays a vital role in many biological processes. In this work, a novel near-infrared FRET (fluorescence resonance energy transfer) fluorescent probe was developed based on the rhodol derivative to detect H 2 S. The ratio of fluorescent intensity with the concentration of H 2 S exhibited an excellent linear relationship when probe LT responded to H 2 S. Probe LT exhibited excellent selectivity, sensitivity and anti-interference. LT was applied to sense endogenous and exogenous H 2 S in cells with great performance. Moreover, LT had the ability to target endoplasmic reticulum (ER) in Hela cells. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorescent dual-responsive probe named Rb-SSC was designed and synthesized using Rhodamine B and tripeptide (SerSerCys-NH 2) as raw reactants. The selective recognition properties in detecting 17 metal ions were investigated by UV–Vis spectroscopy and fluorescence spectroscopy in DMF/water (4:6, v/v, 10.0 mM HEPES, pH = 7.4), and the results showed that Rb-SSC had high selectivity fluorescence response and clear colorimetric analysis for trivalent metal ions (Fe3+, Al3+ and Cr3+). These selectivity were attributed to protonation of Rb-SSC , and the K sp value of the trivalent ions promotes the formation of hydrolyzed H+. Additionally, the limit of detections (LODs) were found to be 27.4 nM for Fe3+, 28 nM for Al3+ and 62.3 nM for Cr3+, respectively. In addition, MTT assay and cells experiments showed that Rb-SSC has low toxicity and achieved fluorescence imaging of trivalent metal ions in living cells. What's more, the G/B ratio has a good linear relationship with the concentrations of Fe3+ based on the smartphone sensing platform (RGB values), and the limit of detection (LOD) was as low as 0.37 μM. [Display omitted] • A novel highly selective and sensitive peptide-based probe named Rb-SSC was firstly synthesized. • Rb-SSC was utilized as a multi-responsive probe for the detection of Fe3+, Al3+ and Cr3+ ions. • The detection limits for Fe3+, Al3+ and Cr3+ were calculated to be 27.4 nM, 28 nM and 62.3 nM, respectively. • Rb-SSC was successfully utilized to recognize Fe3+, Al3+ and Cr3+ in living cells. • Smartphone-assisted detection platform could achieve visual assay of different Fe3+ concentrations. [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]

This work presented a FRET-ICT based fluorescent probe (named NTC) composed of coumarin-benzothiazole as the acceptor and 4-nitrobenzo[ c ][1,2,5] oxadiazole (NBD) as the donor for the detection of SO 2 derivatives in NIR. Probe NTC possessed superior performance including selectivity, quickly response toward SO 3 2−/HSO 3 − and high energy transfer efficiency (94 %). The test strips provided a simple and effective tool in detecting the presence of bisulfite. Besides, NTC was applied to test the sulfur dioxide derivatives in food samples and cells. [Display omitted] • A NIR ratiometric fluorescent probe NTC was developed to detect sulfur dioxide derivatives. • NTC had a large Stokes shift of 150 nm and 94 % energy transfer efficiency. • NTC possessed good selectivity and sensitivity toward sulfur dioxide derivatives. • NTC was applied to detect sulfur dioxide derivatives in test strips, food samples and cell imaging. [ABSTRACT FROM AUTHOR]

A novel series of pentacyclic-fused pyranoquinoliziniums bearing diverse substituents synthesized by one-pot and stepwise rhodium(III)-catalyzed C–H annulation reactions in a modular approach were disclosed. Excellent photophysical properties were obtained via tuning of donor and acceptor moieties allowing the selective bioimaging of mitochondria and lysosome. [Display omitted] • Modular synthetic strategies were rationally designed based on Rh(III) catalysis to build a new series of pentacyclic-fused pyranoquinoliziniums (4a-4i) with novel N and O atom arragnement. • In an one-pot reaction approach, reaction of 2-aryl-4-quinolones (1) with 1,2-diarylalkynes (2) generated two novel products including quinolinone-fused isoquinolines (3) and pyranoquinoliziniums (4). • The isolation of 3 allows the preparation of pyranoquinoliziniums (4) bearing diverse substituents through stepwise synthesis. • By installation of different substituents, these novel pyranoquinoliziniums (4) exhibited tunable absorption and emission properties, and fluorescence quamtum yields. • The newly synthesized pyranoquinoliziniums (4a-4g and 4i) were successfully applied to target mitochondria of living cells while 4h was specific to lysosome. On basis of their unique chemical and photophysical properties, and excellent biological activities, quinoliziniums have been widely used in various research fields. Herein, modular synthetic strategies for efficient synthesis of novel fluorescent quinoliziniums by using one-pot and stepwise rhodium(III)-catalyzed C–H annulations were developed. In the one-pot synthesis, the reaction between 2-aryl-4-quinolones (1) and 1,2-diarylalkynes (2) proceeded in a chemo- and regioselective manner to give quinolinone-fused isoquinolines (3) and pentacyclic-fused pyranoquinoliziniums (4). The structural diversity of pentacyclic-fused pyranoquinoliziniums (4) was expanded by the stepwise synthesis from 3 and 2 , allowing the strategic incorporation of electron-donating (OMe and OH) and electron-withdrawing (Cl) substituents on the top and bottom parts of the pyranoquinoliziniums (4). These newly synthesized pyranoquinoliziniums (4) exhibited tunable absorptions (455–532 nm), emissions (520–610 nm), fluorescence lifetime (0.3–5.6 ns), large Stokes shifts (up to 120 nm), and excellent fluorescence quantum yields (up to 0.73) upon adjusting the different substituents. The the unique arrangement of N and O atoms and extended π-conjugation of 4 could cause the relocation of HOMO comparing with our previous quinoliziniums. Importantly, pyranoquinoliziniums (4a-4g and 4i) targeted the mitochondria, while 4h was localized in lysosome. Due to the remarkable photophysical properties and the potential for organelle targeting of the novel class of quinoliziniums, they could be further applied for biological, chemical and material applications. [ABSTRACT FROM AUTHOR]

• The probe XCCC is a near infrared probe(λ em = 696 nm) with a large Stokes shift value (196 nm). • The probe XCCC is sensitive (LOD = 11.4 nM) and fast for HSO 3 − (within 30 s). • The probe XCCC has been successfully applied to detect HSO 3 − in natural environment and biological system. A colorimetric near-infrared fluorescent probe was designed and synthesized in this paper. The probe XCCC was obtained by simple condensation of 6-(diethylamino)-2,3-dihydro-1 H -xanthene-4-carbaldehyde and 3-cyanoacetyl indoles. XCCC detects HSO 3 − through 1, 4-nucleophilic addition reaction, with obvious near-infrared fluorescence quenching (λ em = 696 nm), and the solution color changes from pink to pale yellow under natural light to realize naked eye recognition. In addition, XCCC has a super large Stokes shift value (196 nm) by calculation. The sensitivity of XCCC and HSO 3 − in the concentration range of 0 ∼ 60 μM is excellent, and the LOD value is as low as 11.4 nM. It is very fast for XCCC to detect HSO 3 − in real time (30 s), and the reversible cycle of HSO 3 −- H 2 O 2 is realized (5 times). In practical application, XCCC successfully detected HSO 3 − qualitatively and quantitatively in actual water samples. Furthermore, we made XCCC into fluorescent test strips to qualitatively detect HSO 3 − in red wine. In particular, XCCC was used to realize exogenous cell imaging of HSO 3 − with different concentrations and reversible cell imaging of HSO 3 −-H 2 O 2 in A549 cells. It shows that probe XCCC has a potential application prospect in food samples and life systems. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A NIR fluorescent probe was synthesized with fluorescent emission at 695 nm and Stoke's shift as large as 260 nm. • 1,3,4-Thiadiazole is a wonderful unit for ESIPT and ICT process and a good identify group for mental ions. • Probe could identify Cu2+ over other analytes with high sensitivity, fast response within 30 s and low detection limit (0.026 μM). • Probe was suitable to assay the Cu2+ level in wine, fruits and herbs. Fluorescent probe L-I was synthesized to demonstrate that 1,3,4-thiadiazole is an attractive moiety and could be utilized as positive hydrogen bond acceptor for excited state intramolecular proton transfer (ESIPT) processes, guider of electrons movement for intramolecular charge transfer (ICT) process and identify group for mental ions. Furthermore, dicyanoisophorone framework was employed to improve the fluorescence characteristics and near-infrared (NIR) fluorescent emission at 695 nm accompanied by a Stoke's shift as large as 260 nm was obtained. L-I could selectively detect Cu2+ over other analytes taking advantages of high sensitivity, fast response within 30 s and low detection limit (0.026 μM). More important, L-I exhibited good performance for detection of Cu2+ in actual water samples, food products, traditional Chinese medicine and for cell imaging which demonstrates practical significance in the fields of environmental monitor, food safety and biotechnology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional fluorescent probe NT was developed to detect pH and viscosity. • The first ratiometric probe to detect pH and viscosity in NIR. • NT could respond to pH immediately, reversibly and accurately. • NT realized the accurate detection of pH in real water samples, human serum, and meat. • NT could be used to monitor pH and viscosity changes in cells. In this work, we developed a ratiometric fluorescent probe (NT) based on ICT framework in near-infrared (NIR) which could detect pH and viscosity simultaneously. Long emission wavelength in NIR could protect the probe from interference of background fluorescence and improve the accuracy of the test. Due to the presence of thiazole-salt, the probe possessed good water solubility and could respond immediately to pH in water system. The pH values measured by NT in the actual samples were not much different from that measured by the pH meter, therefore, NT could give excellent accuracy. NT realized the reversible detection of pH by protonation and deprotonation. NT was used successfully to detect the pH of actual water samples, human serum and meat, as well as the viscosity variation caused by thickeners. Additionally, NT could monitor the changes of pH and viscosity in living cells. Therefore, the novel probe exhibited potential application in the fields of the environment, human health and food safety evaluation. [ABSTRACT FROM AUTHOR]

• The probe exhibited high selectivity and good sensitivity towards Al3+ and Fe3+ metal ions. • The detection limits were 0.76 nM and 0.49 nM respectively. • Biological experiments have shown that the RP probe has good membrane permeability and has the potential to detect Al3+ and Fe3+ in living cells. Fluorescent probe molecules have the advantages of good selectivity, high sensitivity, and easy operation, which have attracted much attention. In this paper, a novel symmetric rhodamine fluorescent probe with structural rigidity was synthesized by a simple reaction using rhodamine 6G as raw material. And it was characterized by NMR and electrospray spray mass spectrometry. Single crystal was prepared by solvent evaporation method, which was the first single crystal of the compound reported domestically and internationally. Special spiral ring structures were observed inside the crystal. Among different competing cations, the probe exhibited high selectivity and good sensitivity towards Al3+ and Fe3+ metal ions. The limits of detection were 0.76 nM and 0.49 nM, respectively. In the presence of Al3+ and Fe3+, the solution changed from colorless to pink. At the same time, there was a significant shift in the UV– vis spectrum and fluorescence emission spectrum. The UV– vis absorption peak appeared at 530 nm, while the emission at 556 nm was turned on. In addition, biological experiments have shown that the RP probe has good membrane permeability and has the potential to detect Al3+ and Fe3+ in Hela cells. [Display omitted] [ABSTRACT FROM AUTHOR]

• Two site II-targeting probes were designed with full consideration of their binding to HSA. • TAB2/6 displayed favorable selective HSA sensitivity and strong HSA binding ability. • WP5-TAB2/6 complex inherited the responsiveness and binding ability of the probe. • WP5-TAB2/6 complex self-assembled into a vesicular supramolecular fluorescent probe. • The supramolecular probe could be used for HSA-mediated cell imaging and drug delivery. Two cationic probes (named TAB2 and TAB6) specifically for binding to site II in human serum albumin (HSA) were designed and synthesized. Both probes exhibited selective fluorescence "turn-on" responsiveness to site II in HSA, though minor differences in their cationic terminals resulted in notable variations in their albumin responsiveness. TAB2 and TAB6 also exhibited strong binding affinity toward HSA. The presence of phenylbutazone, ibuprofen, and lidocaine had minimal impact on the albumin responsiveness of these probes. Furthermore, the complex formed by TAB2/6 and water-soluble pillar[5]arene (WP5) showed enhanced HSA site II-targeting fluorescence responsiveness. More importantly, the WP5-TAB2/6 complex self-assembled into vesicular supramolecular probes in aqueous solution (pH=7.4). Those supramolecular probes were promising for HSA-mediated cell imaging and act as a pH-sensitive drug-delivery platform to enhance the anticancer efficiency of doxorubicin (DOX). [Display omitted] [ABSTRACT FROM AUTHOR]

• The two novel fluorescent probes Z 1 and Z 2 based have been designed and synthesized base on pyrazole derivative to recognize hydrazine • The probe Z 1-2 have ICT characteristics with large Stokes shifts. • The probe Z 1-2 could be made into test paper strips for detection of hydrazine. • The probe Z 1-2 can be used in detection of N 2 H 4 in environmental soil samples and cell imaging. Here, the two novel fluorescent probes Z 1 and Z 2 have been designed and synthesized based on pyrazole derivative to recognize hydrazine, and the molecular structure was determined by 1H NMR, 13C NMR, and ESI-MS. The obtained probe molecules have AIE and ICT characteristics. Nuclear magnetic resonance analysis (NMR) and theoretical calculations were used to confirm the identification mechanism. Probes Z 1 and Z 2 have good selectivity, low detection limits (0.197 µM and 0.185 µM, respectively), and high sensitivity. Probes Z 1 and Z 2 have large Stokes shifts of 198 nm and 211 nm, respectively. The probes also could be made into test paper strips for the detection of hydrazine. Furthermore, the probes can be used in the detection of N 2 H 4 in environmental soil samples and cell imaging. The results showed that the synthetic probe had good biocompatibility. Cell imaging experiments were performed to apply probes to the detection of hydrazine hydrate in HeLa cells. [Display omitted] [ABSTRACT FROM AUTHOR]

β-Galactosidase (β-gal), an enzyme related to cell wall degradation, plays an important role in regulating cell wall metabolism and reconstruction. However, activatable fluorescence probes for the detection and imaging of β-gal fluctuations in plants have been less exploited. Herein, we report an activatable fluorescent probe based on intramolecular charge transfer (ICT), benzothiazole coumarin-bearing β-galactoside (BC-βgal), to achieve distinct in situ imaging of β-gal in plant cells. It exhibits high sensitivity and selectivity to β-gal with a fast response (8 min). BC-βgal can be used to efficiently detect the alternations of intracellular β-gal levels in cabbage root cells with considerable imaging integrity and imaging contrast. Significantly, BC-βgal can assess β-gal activity in cabbage roots under heavy metal stress (Cd2+, Cu2+, and Pb2+), revealing that β-gal activity is negatively correlated with the severity of heavy metal stress. Our work thus facilitates the study of β-gal biological mechanisms. [Display omitted] • An activatable fluorescence probe (BC-βgal) for detecting β-galactosidase was designed. • BC-βgal was high sensitivity and selectivity towards β-gal with fast response (8 min). • BC-βgal imaged the β-gal fluctuation in situ in cabbage roots. • BC-βgal evaluated the β-gal activity under heavy metal stress for the first time. [ABSTRACT FROM AUTHOR]

A triphenylamine-benzofuran-derived fluorescent probe TBSF was developed for monitoring the sulfite level in Chinese medicinal materials and imaging in living cells. In the testing system, under 445 nm excitation, TBSF responded to sulfite steadily with a 540 nm fluorescence reporting signal. The testing system showed advantages including high sensitivity, rapid response, and high selectivity. In particular, TBSF achieved the sulfite detection in the water decoction of Chinese medicinal materials from both addition and excessive fumigation. It also realized the intracellular imaging of both exogenous and endogenous sulfite in living HepG2 cells. The imaging in water decoction-treated cells inferred the potential for the interdisciplinary detection. [Display omitted] • A triphenylamine-benzofuran-derived fluorescent probe developed for monitoring sulfite. • Sulfite level determined in Chinese medicinal materials and imaged in living cells. • Advantages including high sensitivity, rapid response, and high selectivity. • Testing water decoction of Chinese medicinal materials from both addition and excessive fumigation. In this work, a triphenylamine-benzofuran-derived fluorescent probe TBSF was developed for monitoring the sulfite level in Chinese medicinal materials and imaging in living cells. In the testing system, under 445 nm excitation, TBSF responded to sulfite steadily with a 540 nm fluorescence reporting signal. The testing system showed advantages including high sensitivity, rapid response, and high selectivity. In particular, TBSF achieved the sulfite detection in the water decoction of Chinese medicinal materials from both addition and excessive fumigation. It also realized the intracellular imaging of both exogenous and endogenous sulfite in living HepG2 cells. The imaging in water decoction-treated cells inferred the potential for the interdisciplinary detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide-based fluorescent probe DMDH was developed for sequential recognitions of Cu2+ and glyphosate. • Low detection limits for Cu2+ (40.6 nM) and glyphosate (10.6 nM) were obtained. • DMDH has potential prospect in real sample and living cells analysis. • Test strips of DMDH were made and used for naked eye detection of Cu2+ and glyphosate. • Smartphone with RGB Color Picker were employed to analyze the concentration of Cu2+ and glyphosate. A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+ via strong fluorescence quenching, and forming non-fluorescence DMDH -Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH -Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments. [ABSTRACT FROM AUTHOR]

According to DFT calculations, the coordination ratio (1:1) and mechanism of action (PET) of NRh6G-FA with Cu2+ were further investigated and elucidated. NRh6G-FA has been successfully applied to the detection of Cu2+ in CHM samples, "naked eye" identification and bioimaging of Cu2+ in living MCF-7 cells. [Display omitted] • A near-infrared rhodamine-like probe NRh6G-FA responsive to Copper (II) ions was designed and synthesized. • The responses of NRh6G-FA to Cu2+ were thoroughly confirmed by Job's plot, ESI-HRMS and DFT calculations. • NRh6G-FA can be successfully applied to recovery experiments and "naked eye" detection of Cu2+ in Chinese herbal medicine. • NRh6G-FA has low cytotoxicity and can be used for the detection of Cu2+ in living cells. Copper is one of the common among the heavy metal pollution in Chinese herbal medicine (CHM). So, it is essential to develop rapid and accurate testing method to quantify the Cu2+ content in CHM. Herein, we prepared a coordination-based near-infrared fluorescent probe (NRh6G-FA) by introducing a hemicyanine dye in rhodamine 6G scaffold. NRh6G-FA had a high sensitivity, anti-interference performance, fast response (within 60 s), visualization (from light yellow to green) for Cu2+ and excellent sensing performance for the detection of Cu2+ at low concentrations (LOD = 0.225 μM). The most likely mechanism was verified on the basis of Job's plot, ESI-HRMS and DFT calculations. NRh6G-FA could be successfully applied for the detection and "naked eye" recognition of Cu2+ in CHM samples. Moreover, NRh6G-FA was used to visualize Cu2+ in living MCF-7 cells by confocal fluorescence imaging. [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]

Quantitative assays and the structural monitoring of human serum albumin (HSA) are essential for disease diagnosis, drug development, and physiological studies. Commonly used methods for quantifying HSA are based on the dye-HSA binding mechanism, which involves determining the absorption or fluorescence signal when the dye binds non-covalently to HSA. However, these methods generally suffer from poor selectivity and susceptibility to interference from co-existing species. Herein, an ultrasensitive and selective fluorescent probe, 2-(2-morpholinoethyl)-1,3-dioxo-2,3-dihydro-1 H-benzo[de]isoquinolin-6-yl cyclopropanecarboxylate (MDDH), was designed based on the pseudoesterase activity of HSA and used to monitor the acetylation modification, configuration transformation, and biological levels of HSA. Upon catalysis by HSA, the cyclopropanecarbonyl ester bound to MDDH undergoes hydrolysis, yielding a strong fluorescent signal. In contrast to conventional HSA-binding dyes, MDDH demonstrates superior sensitivity (with a 302-fold fluorescence enhancement), high selectivity for distinguishing between HSA and bovine serum albumin, and strong anti-interference against various coexisting species. By sensing HSA pseudoesterase activity, MDDH allows for the sensitive monitoring of structural changes in HSA, including aspirin-induced acetylation, guanidine hydrochloride-induced defolding and trypsin-induced cleavage. Moreover, MDDH exhibits strong stability, low cytotoxicity and good cell membrane permeability. It is suitable for the quantitative determination of HSA in the serum and urine, as well as for the fluorescence imaging of HSA in cells. Our work provides an efficient tool for monitoring the acetylation modifications, configuration changes, and biological content of HSA. • A novel fluorescent probe, MDDH, was designed based on HSA pseudoesterase activity. • MDDH is ultrasensitive and selective for HSA with minimal interference from co-existing species. • MDDH can monitor structural changes in HSA such as acetylation, defolding and cleavage. • MDDH is suitable for HSA quantification in serum and urine and HSA imaging in cells. [ABSTRACT FROM AUTHOR]

γ-Glutamyltranspeptidase (GGT) is a cell surface-associated enzyme, which has been proven to be closely related to many diseases. Thus, development of simple and effective GGT-activatable fluorescent probes for early diagnosis of diseases is of great significance. Herein, a series of simple isomeric pyridine-based GGT-activatable fluorescent probes has been successfully designed and synthesized. The preliminary experimental results indicate that Py-GGT-1 has a significant fluorescence response to GGT via a rare fluorescence-off approach. Further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, reveal that Py-GGT-1 has an excellent ability to monitor endogenous GGT activity. Mechanism studies through HRMS analysis, DFT calculations and molecular docking have theoretically verified the catalytic process between Py-GGT-1 and GGT. To develop its practical application, live-cell imaging and serum-sample analysis were carried out, demonstrating that Py-GGT-1 coud effectively track GGT within cells and organisms. Based its high selectivity and reasonable sensitivity, we expect that the probe will be applied in clinical diagnosis of GGT-related diseases in the future. • We have designed and synthesized a series of simple isomeric pyridine-based probes for GGT detection, which performed a good photophysical property and showed a rapid response to GGT. • Py-GGT-1 was selected as the optimal GGT-activatable probe based on further fluorescence response experiments, such as the time-/dose-dependent fluorescence change and the selectivity/specificity estimation, which revealed that Py-GGT-1 had an excellent ability to monitor endogenous GGT activity. • Mechanism studies through HRMS analysis, DFT calculations and molecular docking theoretically verified its catalytic process between Py-GGT-1 and GGT. • Compared with the reported GGT-activatable probes, our probe shows its simplicity, reliability and rapid response for in vitro monitoring GGT activity with high selectivity and reasonable sensitivity, which is expected to be applied in clinical diagnosis of GGT-related diseases in the future. [ABSTRACT FROM AUTHOR]

The monitoring of formaldehyde (FA) in biosystems and real foods is critical for ensuring human health and food safety. However, the development of effective and highly selective assays for sensing FA in organisms and real food samples remains challenging. Herein, a hydrophilic group-modified the probe (Nap-FA) was reported, which utilizes the specific chemical reaction between FA and hydrazino to trigger a "turn-on" fluorescence response. The probe Nap-FA displayed superior selectivity, high sensitivity, good photostability and a low detection limit in the reaction with FA. Notably, Nap-FA has been successfully used for imaging FA in cells, zebrafish, and plant root tissues. In addition, the rationally constructed probe Nap-FA could rapidly and visually detect FA in real food samples. This work provides a prospective approach for monitoring FA in complex biological systems and food fields. [Display omitted] • A novel probe Nap-FA achieved highly sensitive and selective detection of FA. • The probe Nap-FA has been successfully used for imaging FA in cells and zebrafish. • The probe Nap-FA could sense exogenous FA in live onion and sunflower root tissues. • Nap-FA was been implemented the visual detection of FA in real food samples. [ABSTRACT FROM AUTHOR]