A multimodal fluorescent probe for portable colorimetric detection of pH and it's application in mitochondrial bioimaging.

Mitochondria, as vital energy supplying organelles, play important roles in cellular metabolism, which are closely related with mitochondrial pH (∼8.0). In this work, a novel multimodal fluorescent probe was employed for ratiometric and colorimetric detection of pH. The probe is designed to work by controlling benzothiazole phenol-hemicyanine system as the interaction site and hemicyanine connected by conjugate bonds as the mitochondrial targeting, which also could make the fluorescence of probe red-shifted. This system results in a perfect ratiometric fluorescent response, whose emission changed from red to blue under pH 2.0-10.0, having a broad linear range (pH = 3.0-10.0). And the marked colour change (light yellow to deep purple via naked eye under pH 2.0-11.0) could be used to construct the test strip colorimetry and smartphone APP detection method, realizing the fast, portable, and accurate detection of pH in vitro and environment. Besides, the probe owns the characteristics of easy loading, high selectivity and staining ability of mitochondria, and low cytotoxicity, thereby allowing imaging of pH values and real-time monitor the subcellular mitochondria pH changes caused by drugs in living cells. It thus could be used to monitor the organ-specific dynamics related to transitions between pathological and physiological states.

A two-photon multi-emissive fluorescent probe for discrimination of Cys and Hcy/GSH via an aromatic substitution-rearrangement.

Cys (Cysteine), Hcy (homocysteine), and GSH (glutathione) are three important kinds of biothiols, playing crucial roles in the variety of pathological and physiological processes. It is greater challenges to simultaneously identify different biothiols due to their similar molecular structures and chemical characteristics. In this work, we employed a multi-emissive fluorescent probe by sulfonyl benzoxadiazole (SBD) with halogen chloride unit as the interaction site based on aromatic substitution-rearrangement strategy to discriminate Cys and Hcy/GSH. The response of probe 1 to Cys would generate FRET and cause a red-shift of fluorescence emission, while Hcy/GSH only lead to different degrees of fluorescence enhancement owing to PET. The probe showed good selectivity, high sensitivity, and low detection limits to three biothiols (Cys: 0.86 µM, Hcy: 0.48 µM and GSH: 0.54 µM). Such capability of the probe could be demonstrated to successfully quantitatively detect the concentrations of Cys/Hcy/GSH in human plasmas. In addition, the probe was also successfully applied for imaging biothiols in lysosomes and real-time monitoring GSH changes in living cells through two-photon fluorescence microscopy.

Molecular engineering of a colorimetric two-photon fluorescent probe for visualizing H2S level in lysosome and tumor.

As a multifunctional signaling molecule, hydrogen sulfide (H2S) plays an essential role in diverse physiological and pathological processes. The two-photon fluorescence probes detecting H2S selectively in vivo could be useful tools to better study the mechanism of diseases. Then, an efficient two-photon lysosome-specific probe 1 has been developed to detect endogenous H2S in living cells and mice. Probe 1 displays excellent properties with 28-fold fluorescence enhancement, marked color changes in naked-eye and fluorescence, high selectivity and sensitivity, and low detection limit (0.22 µM) to H2S. These remarkable properties of probe 1 enable its practical applications in detecting H2S in environment (wastewater) and food (beer). Moreover, as a two-photon probe under near infrared excitation at 790 nm, probe 1 can monitor the level changes of endogenous H2S of lysosome and tumor in living system with good membrane permeability and high imaging resolution. Specially, the probe detecting H2S distribution in lysosome could provide more evidences to explain the association of target-organelle and H2S.

Three-dimensional Cu/C porous composite: Facile fabrication and efficient catalytic reduction of 4-nitrophenol.

Developing a facile method to fabricate new heterogeneous Metal-Organic Framework (MOFs) based catalysts with high catalytic activity and stability has drawn significant attention. Herein, we demonstrate a simple in-situ pyrolysis reduction strategy to fabricate a novel three-dimensional (3D) Cu-based catalyst, which displays an outstanding performance for the decomposition of 4-nitrophenol (4-NP). Detailed characterization including SEM, FTIR, XPS, ICP-OES, HRTEM, SAED, XRD and BET confirmed the formation of the Cu/C porous composites (Cu/C-PC). Taking advantage of enormous Cu particles in the composite as well as ultrahigh surface area (196.7 m2/g) of carbon support, Cu/C-PC presents prominent catalytic activity for the hydrogenation reduction 4-NP to 4-aminophenol (4-AP) with apparent rate constant (Kapp) of 0.0267 s-1 (the ratio of Kapp to the catalyst amount is 119 s-1 g-1), which is dramatically higher than that previous reports. On the contrary, after being washed successively (Cu/C-PC-AW) by FeCl3, HCl aqueous solution and deionized water, the Cu/C porous composite materials exhibit fairly weak catalytic activity. The catalytic performance of Cu/C-PC is better than Cu, Cu2O and CuO nanoparticles as well as other catalysts in previous reports. Furthermore, Cu/C-PC shows excellent reusability, indicating its potential applications in treatment of water pollution.

A multifunctional two-photon fluorescent probe for detecting H2S in wastewater and GSH in vivo.

A novel turn-on fluorescent probe, which coumarin-fused coumarin was used as fluorophore to link with 2, 4- dinitrodiphenyl ether moiety that has high selectivity and sensitivity for H2S and thiols, was designed and synthesized. Our probe YB can sensitively react with H2S and GSH to release free fluorophore with strong fluorescence signals. The probe YB could use as a significant molecular imaging tool to study the endogenous GSH in living cell and a practical detector for H2S in the papermaking wastewater.

A resumable two-photon fluorescent probe for Cu2+ and S2- based on magnetic silica core-shell Fe3O4@SiO2 nanoparticles and its application in bioimaging.

A two-photon fluorescent probe for Cu2+ and S2- has been strategically prepared with naphthalimide derivative platform (NPE) covalently grafted onto the surface of magnetic core-shell Fe3O4@SiO2 nanoparticles. The probe (NPE-Fe3O4@SiO2) exhibits selective response to Cu2+ with enhanced fluorescence and efficient separation of Cu2+ with external magnetic field. The consequent product NPE-Fe3O4@SiO2-Cu of NPE-Fe3O4@SiO2 and Cu2+ can work as an excellent sensor for S2- by removing Cu2+ from the complex with fluorescence decreased, recovering the fluorescence of the probe. Therefore, the constituted Off-On-Off type fluorescence monitoring system means the probe is resumable. Moreover, the probe has been used to quantitatively detect Cu2+ and S2- with low detection limits, which are 0.28 µM and 0.12 µM, respectively. Furthermore, the probe shows low cytotoxicity and excellent membrane permeability, which has been successfully applied for monitoring Cu2+ and S2- in living cells and imaging Cu2+ in deep-tissue with two-photon excited fluorescence.

A two-photon ratiometric ESIPT probe for fast detection and bioimaging of palladium species.

A novel ratiometric ESIPT fluorescent probe, which is specific for palladium species of all the typical oxidation states (0, +2, and +4), has been designed. Notably, based on the excited state intramolecular proton transfer (ESIPT) process, the probe exhibits a ratiometric fluorescent response to palladium species with a low detection limit (9.0 nM, 0.96 ppb) in about 1.5 min at room temperature. Moreover, it has been successfully used as a two-photon ratiometric fluorescent palladium probe for in vivo and three-dimensional imaging with low cytotoxicity and autofluorescence. Compared with other reported palladium probes, the probe displays a shorter ratiometric response time and lower detection limit in milder test conditions. All of the results indicate that the probe may be favorable for environmental and biological applications.

A reversible ratiometric two-photon lysosome-targeted probe for real-time monitoring of pH changes in living cells.

Lysosome pH is known to be acidic (4.5-5.5) and has emerged as a critical physiological factor for lysosome activities and functions. Herein, we designed a novel ratiometric lysosome-targeted fluorescence resonance energy transfer (FRET) pH probe, which was fabricated by integrating the coumarin moiety (donor) with the naphthalimide moiety (acceptor). The sensing mechanism was essentially an integration of ICT and FRET processes, leading to the simultaneous intensity enhancement of coumarin and naphthalimide with a pH increase. Furthermore, morpholine was introduced as a lysosome-targeted group. Moreover, the probe could respond to pH in a proportional relationship at very broad range from pH 4.5 to 11.0 and showed remarkable advantages, including rapid response, high sensitivity and selectivity, suitable pKa of 5.62, and good reversibility. Furthermore, the probe was successfully used as a ratiometric TP lysosome-targeted fluorescence probe, not only for imaging of lysosomal pH, but also for visualizing chloroquine-induced changes of intracellular pH in real time in living cells with low cytotoxicity and autofluorescence. These proof-of concept studies demonstrate the practical application of the probe in biological systems.

A water-soluble colorimetric two-photon probe for discrimination of different palladium species and its application in bioimaging.

A novel water-soluble colorimetric and fluorescent palladium probe with excellent selectivity and sensitivity has been designed. Notably, based on a palladium triggered terminal allyl ether cleavage reaction, the probe could detect and discriminate Pd(0) and Pd(2+)/Pd(4+) in about 2.5 min at room temperature with a low detection limit (0.29 ppb) and significant colour change (from light yellow to pink). The probe could serve as an excellent "naked-eye" colorimetric probe for selective and quantitative determination of palladium in aqueous solutions. Moreover, it could be used as a two-photon palladium probe for in vitro/vivo and three-dimensional imaging with low cytotoxicity and autofluorescence.

A two-photon ratiometric ESIPT probe for the discrimination of different palladium species and its application in bioimaging.

A highly selective ratiometric ESIPT fluorescent probe has been designed for the detection of palladium species of all the typical oxidation states (0, +2, +4). The probe exhibits a ratiometric fluorescence response towards the palladium species in about 20 min at room temperature based on the excited state intramolecular proton transfer (ESIPT) process. Moreover, the probe can discriminate different palladium species (Pd0, Pd2+, Pd4+) under different detection conditions. Furthermore, the probe can be used to quantitatively detect palladium in drinking water with a low detection limit (15.6 nM, 1.66 ppb). Additionally, it could be used as a two-photon palladium probe for bioimaging with low cytotoxicity and autofluorescence.

A reusable ratiometric two-photon chemodosimeter for Hg2+ detection based on ESIPT and its application in bioimaging.

A novel ratiometric fluorescent chemodosimeter has been developed for reusable detection of Hg2+. The chemodosimeter responds to Hg2+ sensitively and selectively with a remarkable fluorescence change from green to blue through hampering the excited state intramolecular proton transfer (ESIPT) process. This recyclable chemodosimeter can remove Hg2+ from water by forming a unique mercury-containing compound, which could be reused in the presence of NaBH4. Moreover, the chemodosimeter exhibits a ratiometric fluorescence response to Hg2+ with a very low detection limit (1.0 ppb), and it can be used to detect Hg2+ in drinking water. Furthermore, the ratiometric chemodosimeter has been successfully used for imaging Hg2+ in living cells and tissues using two-photon fluorescence microscopy due to the remarkable emission change from green to blue. This provides a novel testing method for detecting Hg2+ in living cells and tissues with low cytotoxicity and autofluorescence.

Thermodynamic and kinetic characterization of hydrogen-deuterium exchange in beta-phase palladium.

A Sieverts' apparatus coupled with a residual gas analyzer (RGA) is an effective method to detect composition variations during isotopic exchange. This experimental setup provides a tool for the thermodynamic and kinetic characterization of H-D isotope exchange on Pd. The H or D concentrations in the gas and solid phases during the exchanges starting from (H(2) + Pd(x)D) and (D(2) + Pd(x)H) in beta-phase Pd were monitored over a temperature range from 173 to 298 K. The equilibrium properties, i.e., the H-D separation factors alpha and equilibrium constants K(HD), were obtained and found to be very close to those in the literature. The values of equilibrium constant reported here are the only experimental K(HD) data for H-D-Pd system. The H-D exchange rates on beta-Pd were measured for both exchange directions. A comprehensive kinetic model is proposed that correlates the exchange rate and the driving force composed of the reactant concentrations and the extent of deviation from equilibrium. The rate constants were obtained using this model for two exchange directions. The rates for the two exchange directions were found to be close to each other at 173 K, but they differ with temperature increase in such a way that the (D(2) + Pd(x)H) has a higher rate than (H(2) + Pd(x)D). The exchange activation energies obtained are 2.0 and 3.5 kJ/mol for the (H(2) + Pd(x)D) and (D(2) + Pd(x)H) directions, respectively. The difference in activation energies results from the difference in the energy states of (H(2) + Pd(x)D) and (D(2) + Pd(x)D). The calculated exchange profiles using this model agree with the experimental values reasonably well.

Equilibrium isotope effects in the preparation and isothermal decomposition of ternary hydrides Pd(HxD1-x)y (0 < x < 1 and y > 0.6).

A Sieverts' apparatus coupled with a residual gas analysis is used to measure the concentration variations of hydrogen isotopes in the gas and solid phases during exchange and isothermal decomposition of mixed hydrides. beta-phase palladium hydrides with known ratios of H:D, Pd(H x D 1- x ) y (0 < x < 1, y > 0.6), are prepared by H 2 with PdD y or D 2 with PdH y exchange, and their desorption isotherms are reported here at 323 K. A higher equilibrium pressure in isothermal desorption of mixed hydrides is associated with a higher ratio of D/H in the initial mixed hydrides in beta-phase. The composition of the gas desorbed from a mixed hydride varies; i.e., the ratio of D/H in gas decreases with the sum of (H + D) in Pd. The values of the separation factor alpha during desorption at 323 K and during H-D exchange at 248 K are discussed and compared with those in the literature. Desorption isotherms of mixed isotope hydrides are between those of the single isotope hydrides of H-Pd and D-Pd, however, plateaus slope more than those of pure isotope hydrides. The origin of the plateau sloping in the mixed hydrides can be attributed to the compositional variations during desorption, i.e., the equilibrium pressure is greater when D/H ratio in solid is greater. A simple model is proposed in this study that agrees well with experimental results.

Mechanistic investigations on the heterogeneous solid-state reaction of magnesium amides and lithium hydrides.

Isothermal and non-isothermal kinetic measurements on the chemical reaction between Mg(NH2)(2) and LiH, as well as the thermal decomposition of Mg(NH(2))(2), give apparent activation energies of 88.1 and 130 kJ/mol, respectively, which reveal that the thermal decomposition of Mg(NH2)(2) is unlikely to be an elementary step in the chemical reaction of Mg(NH2)(2) and 2LiH. The H-D exchange between H(delta+) in Mg(NH2)(2) and D(delta-) in LiD gives evidence for the coordinated interaction between amide and hydride. The observed linear and nonlinear kinetic growth in the reaction of Mg(NH2)(2)-2LiH indicates that the reaction rate is controlled by the interface reaction in the early stage of the reaction and by mass transport through the imide layer in the later stage. Both particle size and degree of mixing of the reacting species affect the overall kinetics of the reactions.