A novel AIRE-based fluorescent ratiometric probe with endoplasmic reticulum-targeting ability for detection of hypochlorite and bioimaging

A novel AIEgen fluorescent probe based on quinoline-malononitrile for monitoring and imaging ClO- and viscosity in biosystem

Hypochlorite (ClO-) and viscosity play a pivotal role in biological immune defense systems, it has been demonstrated that alterations in ClO- may link to the modifications in intracellular viscosity. Consequently, it is crucial to develop a tool that can accurately assess these changes of ClO- and viscosity concurrently. In this work, a dual-responsive fluorescent probe QM-WV based on the ICT effect for simultaneous detection of ClO- and viscosity was constructed. QM-WV exhibited a signally turn-on fluorescence signal at 552 nm for ClO- with favorable selectivity. Meanwhile, QM-WV displayed an exceptional 'off-on' fluorescence response at 650 nm to viscosity changes in glycerol-ethanol system. More importantly, QM-WV is capable of visually detecting ClO- by using smartphone as a portable signal processing device. Based on its low cytotoxicity and stability under physiological conditions, QM-WV further enabled the detection and imaging of ClO- and viscosity in HeLa cells and zebrafish.

A double-ionic macrocycle based on cyanostilbene: First organic fluorescence sensor based small molecular system for detecting cholesterol

Cholesterol is an essential nutrient and an important biomarker for many diseases. While several analytical methods based on large-scale instruments and organic-inorganic hybrid quantum dots had been developed on examining cholesterol, the organic fluorescence sensor for rapid, simple and in-situ examining cholesterol have not been reported to date. In this work, a novel double-ionic macrocycle (DIM) based on cyanostilbene was designed and synthesized as the first organic fluorescence sensor based small molecular system for detecting cholesterol. A distinct fluorescence color change from green-yellow to green-blue was observed upon cholesterol detection. This method exhibited high selectivity among 22 biomolecules and 16 ions. The detection limit was as low as 1.03 × 10-8 M, indicating exceptional sensitivity. The sensing mechanism, involving cholesterol inclusion whthin the cavity of DIM, was elucidated by Job's curve, 1H NMR spectroscopy, MS spectroscopy, XRD analysis, POM investigation, CD spectroscopy, CPL investigation and density functional theory calculations. The practical utility of DIM was demonstrated in various applications including test paper, real egg yolk samples, and simulated water samples. These experiments confirmed its capability for both qualitative and quantitative in-situ cholesterol detection in real-world environments and daily applications, offering rapid and simple operation.

High-performance ratiometric fluorescent probe for rapid, visual and ultrasensitive monitoring/bioimaging of hypochlorite in real-life samples and living systems

Hypochlorite (ClO-) is a highly reactive chemical extensively used in households, public areas, and various industries due to its multiple functions of disinfection, bleaching, and sterilization. However, overuse of ClO- may contaminate the water, soil, air and food, leading to negative impacts on the environments, ecosystems and food safety. Meanwhile, excessive ClO- in human body can also cause severe damage to the immune system. Thus, the development of effective and precise detection tools for ClO- is of great significance to better understand its complicated roles in environments and biosystems. Herein, a new high-performance ratiometric fluorescent probe 2-amino-3-((10-propyl-10H-phenothiazin-3-yl)methylene)-amino)maleonitrile (PD) was developed for effective detection of ClO- in various bio/environmental and food samples. Probe PD exhibits highly-specific "ratiometric" fluorescent response to ClO- with rapid response (< 1 min), excellent sensitivity (detection limit, 47.4 nM), wide applicable pH range (4 -12), and excellent versatility in practical applications. In practical applications, PD enables the sensitive and quantitative detection of ClO- levels in various water samples, bio-fluids, dairy products, fruits and vegetables with high-precision (recoveries, 97.00 -104.40 %), as well as the successful application for visual tracking ClO- in fresh fruits and vegetables. Furthermore, test strips containing PD offer a visual and convenient tool for quick identification of ClO- in aqueous media by the naked eye. Importantly, the good biocompatibility of PD enables its practical applications in real-time bioimaging of endogenous/exogenous ClO- levels in living cells, bacteria, onion cells, Arabidopsis, as well as zebrafish. This study provided an effective method for visual monitoring and bioimaging of ClO- levels in various environments, foods and living biosystems.

A near-infrared ratiometric fluorescent probe for simultaneous detection of hydrazine and hypochlorous acid in biological systems and its portable detection in environmental samples using a smartphone

Hydrazine (N2H4) and hypochlorous acid (HClO) are significant chemicals that gain widespread applications in industrial fields. Excessive N2H4 and HClO can cause severe environmental pollution and have toxic effects on living organisms. In this study, a near-infrared (NIR) dual-responsive fluorescent probe PTZ-BA was designed for the ratiometric detection of N2H4 and HClO. PTZ-BA exhibited a remarkable near-infrared signal at 680 nm with a large Stokes shift of 275 nm, and it can simultaneously detect N2H4 and HClO through different fluorescence channels without signal crosstalk. PTZ-BA possessed good selectivity, low detection limits, dramatic emission wavelength shift, short response time for the detection of N2H4 and HClO. PTZ-BA could be employed for the quantitative analysis of N2H4 and HClO in environmental soil and water samples, respectively. Furthermore, the functionalized nanofiber membranes and hydrogels were readily fabricated using this probe, enabling the portable on-site detection of gaseous N2H4 and HClO with the help of smartphone. PTZ-BA could achieve the real-time tracking of N2H4 and HClO in HeLa cells, onion cells and zebrafish. This research offers a versatile fluorescence detection platform for N2H4 and HClO, holding a significant potential for environmental analysis and public health monitoring.

A new oligothiophene-derivatized fluorescent sensor for detecting and imaging of Hg2+ in water/soil/urine/tea/seafood samples and living plants

Considering the high toxicity of Hg2+ to living organisms, accurately and sensitively detecting Hg2+ in environments, biology and food systems is of the utmost importance. Herein, we present a new fast-responsive oligothiophene-derivatized fluorescent sensor TTB for Hg2+ detection in real water/soil/urine/food samples. Sensor TTB shows a quick response, ultrahigh specificity, strong anti-disturbance, high-sensitivity with a satisfactory detection limit of 0.23 µM and good reversibility towards Hg2+. The response mechanism was well examined through Job's plot, FTIR spectra and DFT calculations. To examine naked-eye recognition of Hg2+, a visualization method by the TTB-coated test paper and cotton swabs was used for quickly detecting Hg2+. Additionally, sensor TTB shows good application flexibility and proves the capability for quantitative and accurate monitoring of Hg2+ levels in various water, soil, human urine, tea and seafood samples with an excellent efficiency. Moreover, fluorescence imaging experiments demonstrated that the TTB showed good cell-permeability and was utilized to detect/image Hg2+ in living plants. This study provides a powerful tool for accurately and reliably detecting Hg2+ in bio/environmental and food systems.

COX-2-targeted fluorescent probe for ClO- monitoring in precise cancer detection

Hypochlorite anion (ClO-) is closely associated with cancer development and progression, necessitating precise monitoring of ClO- in tumor sites, and Cyclooxygenase-2 (COX-2 is highly expressed in tumor cells. So we rationally designed two ClO--specific responsive fluorescent probes COX2-ClO1 and COX2-ClO2, using indomethacin (IMC) as the COX-2 targeting moiety and methylene blue as fluorophore unit. Both probes exhibited high selectivity and sensitivity towards ClO- in the in vitro solution assays and possess excellent biocompatibility in cellular experiments. Compared to COX2-ClO1, COX2-ClO2 exhibited superior targeting specificity for COX-2, enabling precise differentiation between tumor cells and normal cells and allowing imaging of both exogenous and endogenous ClO- in the in vivo experiments. Moreover, COX2-ClO2 could accurately target the tumor site in xenograft mice and is likely metabolized by the kidneys.

A colorimetric fluorescent probe for reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO- and its application in food and bioimaging

In view of the significant role of reactive sulfur species (RSS) and reactive oxygen species (ROS) in maintaining the redox homeostasis of organisms, we proposed a colorimetric fluorescent probe (HTN) for reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO-. C = C is the active site for the Michael addition of HSO3- and the oxidation of ClO-. When HTN interacts with HSO3- and ClO-, it exhibits fluorescence quenching. The addition of oxidizing H2O2 to the system can restore the conjugate structure of the addition product of HSO3- (HTN-HSO3-) and the fluorescence recovery, but it cannot restore the structure of the oxidation product of ClO- (HTN-ClO-). By studying the change of the reversibility/non-reversibility of the probe structure with the addition of H2O2, the purpose of reversible detection of HSO3-/H2O2 and distinguishing HSO3-/ClO- is achieved. In addition, HTN can not only be used as a fluorescent ink to detect HSO3- on the test paper, but also has excellent detection effect on HSO3- and ClO- in real food samples and water samples. Meantime, HTN has good biocompatibility and can target mitochondria to achieve reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO- in living cells. Therefore, HTN has great potential as a molecular tool for studying redox homeostasis in the interaction network of complex living systems.

Mitochondria-targeted fluorescent probes based on coumarin-hemicyanine for viscosity changes and their applications in cells and mice

As an important parameter of the cellular microenvironment, the changes in mitochondrial viscosity are closely related to various life activities. Therefore, the development of fluorescent probes for test the changes of mitochondrial viscosity has great significance. In this study, we developed two fluorescent probes for the detection of the mitochondrial viscosity changes. The probes exhibited different fluorescence intensities at different viscosity based on the twisted intramolecular charge transfer process. The characteristics of high anti-interference performance, wide pH applicability, low cytotoxicity and excellent mitochondrial targeting performance made the probes successfully used to distinguish normal cells from cancer cells, achieving visualization of viscosity changes. Furthermore, probes P1 and P2 can also be used as early diagnosis of tumors in mice and reveal the pathology of tumor development. The probes could be serve as a promising viscosity detection tool for discriminating normal cells and cancer cells in biology-related research.

A FRET/TICT based multifunctional fluorescent probe for the monitoring of SO2 derivatives and viscosity in living cells and real samples

SO2 derivatives and viscosity are important intracellular indicators, which are closely associated with various physiological metabolisms in organisms. The unregulated contents of SO2 derivatives and viscosity in vivo commonly related to some disorders. In this work, probe JFT was developed relying on FRET and TICT mechanisms for the simultaneous detection of SO2 derivatives and viscosity. JFT can rapidly detect viscosity levels with continuously enhanced fluorescence signals at 582 nm basing on the increasing of viscosity. Moreover, JFT was also sensitive to the changes of SO2 derivatives level with a low detection limit (61.5 nM), rapid responding time (with 16 min), excellent selectivity and anti-interference capacity. JFT could detect bisulfite in real water, wine and food samples with high accuracy and recovery rate. Cell imaging indicated that JFT could monitor the endogenous SO2 derivatives and viscosity in mitochondria. Importantly, JFT could recognize the cancer cells basing on the cell imaging difference of JFT in AGS and GES-1 cells.

A dual sensitive fluorescence probe for the simultaneous visualization of hypochlorite and viscosity in living cells and zebrafish

As vital microenvironmental indicators, hypochlorite and viscosity levels can be applied to diagnose diseases. Thus, real time and in situ monitoring of hypochlorite and viscosity has gained increasing attentions. A fluorescence probe named JDK was developed by using a novel acceptor of 2-(2-(5-(dimethylamino)thiophen-2-yl)vinyl)-1,3,3-trimethyl-3H-indol-1-ium fluorophore basing on FRET and TICT system. JDK possessed large Stokes shift, broad emission peak gap, prominent photostability and biocompatibility. JDK could track hypochlorite with rapid response time (within 1 min) and low detection limit (28.5 nM). Meaningfully, JDK was favor to append on mitochondria where physiological processes can be disrupted deriving from the abnormal concentrations of hypochlorite and viscosity. Successfully, JDK could visualize endogenous hypochlorite and viscosity in living cells and zebrafish.

AIE-based fluorescent probe designed with xanthone as a π-bridge for detecting of ClO- in pericarp and living cells

The role of ClO- in the physiological functioning of organisms is significant. In this paper, the four fluorescent probes HONx (HON1, HON2, HON3 and HON4) were prepared based on oxyanthracene through the introduction of different substituents, and their photophysical properties were investigated, among which the AIE effect of HON1 was the most significant, and therefore the fluorescent "turn-off" ClO- probe HON1-CN was chosen to be prepared by constructing the ClO- recognition site hydrazone bond at HON1. The ClO- recognises the hydrazone group in the probe HON1-CN, and when the hydrazone bond is broken, the aldehyde group is released, generating HON1 with yellow fluorescence. The probe HON1-CN is highly selective and stable for the detection of ClO- with a detection limit of 0.48 μM and a more than 10-fold increase in fluorescence intensity when the fluorescence is 'switched on', and to a lesser extent, the probe is also very good for the detection of hypochlorite ClO- in the pericarp. Finally, HON1-CN has also been used to detect the presence of ClO- in HeLa cells and zebrafish.

Fluorescence imaging of dopamine in living cells triggered by unique coupling reactions

BACKGROUND

Dopamine (DA) is a significant neurotransmitter and catecholamine molecule in the mammalian brain. It plays a crucial role in perception, cognition, central nervous system regulation, and hormone secretion. The detection of DA levels in living systems is a vital aspect of the research and early diagnosis of neurological disorders.

RESULTS

In this study, we achieved an effective fluorescence generation specific to DA under physiological pH conditions by coupling the DA detection reaction to the HClO oxidation reaction. This method has been used for the detection of DA in cells, as well as for the visualization of DA levels in cellular models of inflammation and depression.

SIGNIFICANCE

This is the first time that utilizes an organic fluorescent molecular probe to detect DA in living cells.

Visualizing ClO- fluctuations in drug-induced liver injury and bacterium via a robust ratiometric fluorescent probe

As a type of reactive oxygen species, hypochlorous acid (ClO-) plays an important role in sterilization, disinfection and protection in organisms. However, excessive production of ClO- is closely related to various diseases. In this work, we have designed a robust ratiometric fluorescent probe, RDB-ClO, using the excited-state intramolecular proton transfer (ESIPT) strategy. RDB-ClO was achieved by modifying 2-(2-(benzo[d]thiazol-2-yl)-6-(diethylamino)-3-oxo-3H-xanthen-9-yl) benzoic acid (RDB-OH) with a 1-naphthoyl chloride group, specifically for the sensitive detection of ClO-. In the presence of ClO-, RDB-ClO demonstrated relatively good performance, showing swift response time (35 s), low detection limit of 5.1 nM and high selectivity towards ClO-. Notably, the convenience and accessibility detection of ClO- has been implemented using test strip and agarose probe. RDB-ClO effectively tracked both endogenous and exogenous ClO- in HeLa cells, HepG2 cells and zebrafish. Additionally, it is successfully applied to detect changes of exogenous ClO- content in E. coli. and acetaminophen (APAP)-induced liver injury in mice. The development of RDB-ClO represents a promising molecular tool for studying the pathogenesis of DILI and biotransformation of ClO- in bacteria.

A cyanine based fluorescent probe for detecting hypochlorite in vitro and in vivo

Hypochlorite (ClO-) is recognized as a bioactive substance that plays a crucial role in various physiological and pathological processes. The increase of ClO- content in cells is a key factor in the early atherosclerosis lesions, which are closely linked to cardiovascular and cerebrovascular diseases. Therefore, the development of an efficient and sensitive method for detecting hypochlorite in tap water, serum, and living cells, including animal model in vivo is of paramount importance. In this study, a novel fluorescent probe (Cy-F) based on the cyanine group was designed for the specific detection of ClO-, demonstrating exceptional selectivity, high sensitivity, and rapid response. The probe successfully detected ClO- in tap water and serum with a limit of detection (LOD) of 2.93 × 10-7 M, showcasing excellent anti-interference capabilities. Notably, the probe exhibited good biocompatibility, low biological toxicity, and proved effective for detecting and analyzing ClO- in live cells and zebrafish. This newly developed probe offers a promising approach and valuable tool for detecting ClO- with biosafety considerations, paving the way for the design of functional probes tailored for future biomedical applications.

Long-term tracking of lysosomal dynamics with highly stable fluorescent probe

Monitoring lysosomal dynamics in real-time, especially in vivo, poses significant challenges due to the complex and dynamic nature of cellular environments. It is extremely important to construct fluorescent probes with high stability for imaging lysosomes to minimize interference from other cellular components, in order to ensure prolonged imaging. A fluorescent probe (PDB) has been proposed for targeting lysosomes, which was less affected to changes in the cellular microenvironment (such as pH, viscosity and polarity). PDB can be easily prepared by 4'-piperazinoacetophenone and 2-(4-diethylamino)-2-hydroxybenzoyl) benzoicacid, containing a piperazine group for labeling and imaging lysosomes and the high pKa value (∼9.35) allowed PDB to efficiently track lysosomes. The emission wavelength of PDB in aqueous solution was 634 nm (λex = 572 nm, Фf = 0.11). The dynamic process of lysosome induced by starvation and rapamycin was successfully explored by fluorescence imaging. Compared with the commercially available Lyso-Tracker green, the high photostability fluorescent probe can ensure 3D high-fidelity tracking and resist photobleaching. Therefore, PDB, unaffected by the cell microenvironment, successfully achieved long-term tracking of lysosomal movement, even enabling imaging in tumor-bearing mice over 11 days. The strong fluorescence signal, high stability, and long-term tracking capability indicate that PDB has tremendous potential in monitoring biological processes.

A novel AIE-based mitochondria-targeting fluorescent probe for monitoring of the fluctuation of endogenous hypochlorous acid in ferroptosis models

Ferroptosis is a way of cell death mainly due to the imbalance between the production and degradation of lipid reactive oxygen species, which is closely associated with various diseases. Endogenous hypochlorous acid (HOCl) mainly produced in mitochondria is regarded as an important signal molecule of ferroptosis. Therefore, monitoring the fluctuation of endogenous HOCl is beneficial to better understand and treat ferroptosis-related diseases. Inspired by the promising aggregation-induced emission (AIE) properties of tetraphenylethene (TPE), herein, we rationally constructed a novel AIE-based fluorescent probe, namely QTrPEP, for HOCl with nice mitochondria-targeting ability and high sensitivity and selectivity. Probe QTrPEP consisted of phenylborate ester and the AIE fluorophore of quinoline-conjugated triphenylethylene (QTrPE). HOCl can brighten the strong fluorescence through a specific HOCl-triggered cleavage of the phenylborate ester bond and release of QTrPE, which has been demonstrated by MS, HPLC, and DLS experiments. In addition, combining QTrPE-doped test strips with a smartphone-based measurement demonstrated the excellent performance of the probe to sense HOCl. The obtained favorable optical properties and negligible cytotoxicity allowed the use of this probe for tracking of HOCl in three different cells. In particular, this work represents the first AIE-based mitochondria-targeting fluorescent probe for monitoring the fluctuation of HOCl in ferroptosis.

Development of a polarity-sensitive ratiometric fluorescent probe based on the intramolecular reaction of spiro-oxazolidine and its applications for in situ visualizing the fluctuations of polarity during ER stress

Polarity is a vital element in endoplasmic reticulum (ER) microenvironment, and its variation is closely related to many physiological and pathological activities of ER, so it is necessary to trace fluctuations of polarity in ER. However, most of fluorescent probes for detecting polarity dependent on the changes of single emission, which could be affected by many factors and cause false signals. Ratiometric fluorescent probe with "built-in calibration" can effectively avoid detection errors. Here, we have designed a ratiometric fluorescent probe HM for monitoring the ER polarity based on the intramolecular reaction of spiro-oxazolidine. It forms ring open/closed isomers driven by polarity to afford ratiometric sensing. Probe HM have manifested its ratiometric responses to polarity in spectroscopic results, which could offer much more precise information for the changes of polarity in living cells with the internal built-in correction. It also showed large emission shift ( 133 nm), high selectivity and photo-stability. In biological imaging, HM could selectively accumulate in ER with high photo-stability. Importantly, HM has ability for in situ tracing the changes of ER polarity with ratiometric behavior during the ER stress process with the stimulation of tunicamycin, dithiothreitol and hypoxia, suggesting that HM is an effective molecule tool for monitoring the variations of ER polarity.

A lysosome-targeted fluorescent probe for fluorescence imaging of hypochlorous acid in living cells and in vivo

Lysosomes, as crucial acidic organelles in cells, play a significant role in cellular functions. The levels and distribution of hypochlorous acid (HOCl) within lysosomes can profoundly impact their biological functionality. Hence, real-time monitoring of the concentration of HOCl in lysosomes holds paramount importance for further understanding various physiological and pathological processes associated with lysosomes. In this study, we developed a bodipy-based fluorescent probe derived from pyridine and phenyl selenide for the specific detection of HOCl in aqueous solutions. Leveraging the probe's sensitive photoinduced electron transfer effect from phenyl selenide to the fluorophore, the probe exhibited satisfactory high sensitivity (with a limit of detection of 5.2 nM and a response time of 15 s) to hypochlorous acid. Further biological experiments confirmed that the introduction of the pyridine moiety enabled the probe molecule to selectively target lysosomes. Moreover, the probe successfully facilitated real-time monitoring of HOCl in cell models stimulated by N-acetylcysteine (NAC) and lipopolysaccharide (LPS), as well as in a normal zebrafish model. This provides a universal method for dynamically sensing HOCl in lysosomes.

Targeted mitochondrial fluorescence probe with large stokes shift for detecting viscosity changes in vivo and in ferroptosis process

We created four fluorescent sensors in our work to determine the viscosity of mitochondria. Following screening, the probe Mito-3 was chosen because in contrast to the other three probes, it had a greater fluorescence enhancement, large Stokes shift (113 nm) and had a particular response to viscosity that was unaffected by polarity or biological species. As the viscosity increased from PBS to 90 % glycerol, the fluorescence intensity of probe at 586 nm increased 17-fold. Mito-3 has strong biocompatibility and is able to track changes in cell viscosity in response to nystatin and monensin stimulation. Furthermore, the probe has been successfully applied to detect changes in viscosity caused by nystatin and monensin in zebrafish. Above all, the probe can be applied to the increase in mitochondrial viscosity that accompanies the ferroptosis process. Mito-3 has the potential to help further study the relationship between viscosity and ferroptosis.

Cyanine based ratio fluorescent probe and its application in hypochlorite detection

Hypochlorite (ClO-), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO- or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO- is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO-, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO-, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 μM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

Dissecting lysosomal viscosity fluctuations in live cells and liver tissues with an ingenious NIR fluorescent probe

Viscosity is a pivotal component in the cell microenvironment, while lysosomal viscosity fluctuation is associated with various human diseases, such as tumors and liver diseases. Herein, a near-infrared fluorescent probe (BIMM) based on merocyanine dyes was designed and synthesized for detecting lysosomal viscosity in live cells and liver tissue. The increase in viscosity restricts the free rotation of single bonds, leading to enhanced fluorescence intensity. BIMM exhibits high sensitivity and good selectivity, and is applicable to a wide pH range. BIMM has near-infrared emission, and the fluorescent intensity shows an excellent linear relationship with viscosity. Furthermore, BIMM possessing excellent lysosomes-targeting ability, and can monitor viscosity changes in live cells stimulated by dexamethasone, lipopolysaccharide (LPS), and nigericin, and differentiate between cancer cells and normal cells. Noticeably, BIMM can accurately analyze viscosity changes in various liver disease models with HepG2 cells, and is successfully utilized to visualize variations in viscosity on APAP-induced liver injury. All the results demonstrated that BIMM is a powerful wash-free tool to monitor the viscosity fluctuations in living systems.

Visualized detection of water by modified metal organic framework-199 and its portable test paper with reversible color change

Herein, we fabricate a melamine modified metal organic framework-199 composite (MOF-199@melamine), of which the structure is affected by the dynamics of the guest H2O molecule with significant color change. It realizes the visualized quantitative detection of water in a variety of organic solvents within 30 s. Moreover, DMF restored the original structure by replacing H2O molecules, realizing the regeneration of the materials. On this basis, PTFE-MOF-199@melamine test paper is developed to portably detect water content in organic solvents (maximum 0 %-98 % (v/v) water content) and ambient relative humidity (11-85 %). The test paper can be recycled four times with a regeneration rate higher than 90 %. The results are expected to solve the problems of existed electrochemical or fluorescence strategy such as the complicated operation process and signal output/reading system.

A novel fluorescent probe for cascade detection of hydrogen sulfide and hypochlorous acid and its application in bioimaging

Herein we developed a cascade detection mode for the detection of HS- and ClO- by the novel probe NM-Cl bearing a conjugating naphthalene-dicyanoisophorone unit. The probe displayed sensitive and remarkable fluorescent enhancement in response to HS-, but not to other analytes. The mixture of probe and HS- constructed a specific sensing system for ClO- by fluorescent quenching response. The mechanism studies indicated that the successive reacting of HS- substitution Cl atom in probe and then addition of ClO- facilitation a thiofuran ring-forming induced differentiated fluorescence emission. This study provides a novel mechanism for the detection of HS- and ClO-, the imaging of cell and living animal further indicating the good application prospects of the probe in biosensing and bioimaging.

A unique phenothiazine-based fluorescent probe using benzothiazolium as a reactivity regulator for the specific detection of hypochlorite in drinking water and living organisms

As a common disinfectant and an essential reactive oxygen species (ROS), hypochlorite (ClO-) plays vital roles in both water treatment and cell metabolism, but its abnormal level can cause serious harm to human health. Therefore, quantifying ClO- level in drinking water and living organisms is extremely significant. Herein, we decorated different cationic heterocycles on phenothiazine core to construct three fluorescent probes for ClO-. According to the results, only benzothiazolium moiety reasonably adjusted the electron cloud density at sulfur atom of phenothiazine core for the specific oxidation with ClO-, thus endowing the prepared probe PT-BT with a perfect selectivity for ClO-. Meanwhile, PT-BT exhibited a low detection limit (38 nM) and a fast response (within 20 s) toward ClO-. Furthermore, this probe was utilized to fabricate a ready-to-use test strip, which could quantitatively measure ClO- level in real water samples by a portable smartphone sensing platform. Notably, PT-BT targeted mitochondria efficiently, and successfully visualized endogenous ClO- in living cells and zebrafish larvae. Especially, PT-BT was able to monitor the dynamic change of ClO- level in inflammatory mice. These results strongly manifested that probe PT-BT was a promising tool for detecting ClO- in drinking water and living organisms.

The rational utilization of organelle microenvironment for imaging of lysosomal SO2 with high fidelity

Nowadays, more and more studies have linked the abnormal expression of active molecules in organelles with the occurrence of diseases, so there is an urgent need to develop tools for detecting active molecules in specific organelles. However, the recognition receptors of most organelle-targeting probes currently developed always remain active, which easily causes them to react with the analyte in the cytoplasm, thus misjudging the role of the analyte in the physiological and pathological processes. Therefore, it is of great significance to develop a new strategy for the design of probes capable of high-fidelity imaging of the analyte in specific organelles. Herein, we propose a new strategy that the activation of recognition receptors that can be triggered by the microenvironment of targeting organelles. Based on this strategy, we develop a novel lysosome-targeting fluorescent probe (Lyso-SO₂) for imaging of sulfur dioxide (SO₂) with high-fidelity in lysosomes. The inert probe is activated by the acidic environment in the lysosome and then responds quickly (<2 s) and sensitively (LOD = 0.34 μM) to SO₂. This paradigm by taking full advantage of the features of the organelle microenvironment provides a promising methodology for developing organelle-targeting probes for high-fidelity imaging.

A benzo BODIPY based fluorescent probe for selective visualization of hypochlorous acid in living cells and zebrafish

Hypochlorous acid (HOCl) is an essential endogenous reactive oxygen species in biological systems, playing a critical role in various physiological processes. Real-time monitoring of HOCl concentration in living organisms is essential for understanding its biological functions and pathological roles. In this study, we developed a novel fluorescent probe based on benzobodipy, BBDP, for rapid and sensitive detection of HOCl in aqueous solutions. The probe exhibited a significant fluorescence turn-on response to HOCl based on its specific oxidation reaction towards diphenylphosphine, with high selectivity, instantaneous response (less than 10 s), and low detection limit (21.6 nM). Furthermore, bioimaging results illustrated that the probe could be applied for real-time fluorescence imaging of HOCl in live cells and zebrafish. The development of BBDP may provide a new tool for exploring the biological functions of HOCl and its pathological roles in diseases.