Et4NCl-Promoted Electrochemical Atherton-Todd Type Reaction to Construct P(O)-F Bonds.

An electrochemical synthetic strategy to construct P(O)-F bonds was developed via the Atherton-Todd reaction. Promoted by Et4NCl, a series of biologically active phosphoric fluorides were synthesized by use of commercially available P(O)-H feedstocks and Et3N·3HF as the F-source. With this protocol, some potentially functional P(O)-OR and P(O)-SR motifs could also be smoothly forged. This sustainable fluorination approach features step-economy, is chemical-oxidant- and metal-catalyst-free, and offers low cost and mild conditions. Additionally, cyclic voltammetry and control experiments were conducted to propose a reasonable mechanism.

A novel 1,8-naphthalimide-based fluorescent chemosensor for the detection of HSA in living cells.

Human serum albumin (HSA) is an essential protein for maintaining human health. Accurate detection and quantification of HSA are of great significance for disease diagnosis and biochemical research. Here, a new HSA fluorescent probe BNPE based on the 1,8-naphthalimide fluorophore was designed and synthesized. The probe could recognize HSA through a twisted intramolecular charge transfer mechanism, effectively avoid the interference of most substances, and realize HSA fluorescence imaging in living cells.

A novel fluorescent probe with large Stokes shift for the detection of viscosity changes and its imaging in living cells.

As an important cellular microenvironmental parameter, viscosity could reflect the status of living cells. Small molecular fluorescent probes are a vital tool to measure the change of viscosity in living cells. A novel fluorescence probe ZL-1 with a large Stokes shift (in methanol it reached to 153 nm and in glycerol it reached to 125 nm) and excellent sensitivity toward viscosity was developed. The sharp enhancement of the emission intensity for the probe ZL-1 from low viscous methanol to high viscous glycerol indicated that the probe ZL-1 could respond to the viscosity variations. Moreover, the probe ZL-1 has been successfully utilized to detect of the viscosity variations in living cells.

Carrier-free nanoparticles of camptothecin prodrug for chemo-photothermal therapy: the making, in vitro and in vivo testing.

BACKGROUND: Nanoscale drug delivery systems have emerged as broadly applicable approach for chemo-photothermal therapy. However, these nanoscale drug delivery systems suffer from carrier-induced toxicity, uncontrolled drug release and low drug carrying capacity issues. Thus, to develop carrier-free nanoparticles self-assembled from amphiphilic drug molecules, containing photothermal agent and anticancer drug, are very attractive. RESULTS: In this study, we conjugated camptothecin (CPT) with a photothermal agent new indocyanine green (IR820) via a redox-responsive disulfide linker. The resulting amphiphilic drug-drug conjugate (IR820-SS-CPT) can self-assemble into nanoparticles (IR820-SS-CPT NPs) in aqueous solution, thus remarkably improving the membrane permeability of IR820 and the aqueous solubility of CPT. The disulfide bond in the IR820-SS-CPT NPs could be cleaved in GSH rich tumor microenvironment, leading to the on demand release of the conjugated drug. Importantly, the IR820-SS-CPT NPs displayed an extremely high therapeutic agent loading efficiency (approaching 100%). Besides, in vitro experimental results indicated that IR820-SS-CPT NPs displayed remarkable tumor cell killing efficiency. Especially, the IR820-SS-CPT NPs exhibited excellent anti-tumor effects in vivo. Both in vitro and in vivo experiments were conducted, which have indicated that the design of IR820-SS-CPT NPs can provide an efficient nanotherapeutics for chemo-photothermal therapy. CONCLUSION: A novel activatable amphiphilic small molecular prodrug IR820-SS-CPT has been developed in this study, which integrated multiple advantages of GSH-triggered drug release, high therapeutic agent content, and combined chemo-photothermal therapy into one drug delivery system.

[Exploration of active components and mechanism of Scutellariae Radix-Phellodendri Chinensis Cortex drug pair in treatment of psoriasis based on network pharmacology and molecular docking].

This paper aims to explore active components and mechanism of Scutellariae Radix(SR)-Phellodendri Chinensis Cortex(PCC) drug pair in treatment of psoriasis by network pharmacology and molecular docking. Specifically, the chemical components of SR and PCC were retrieved from literature and TCMSP, as well as targets of these components from PharmMapper and UniProt, and the targets related to psoriasis from OMIM, TTD, PharmGkb, and DrugBank. Then the chemical component-medicinal target, protein-protein interaction(PPI), and chemical component-psoriasis target networks were constructed by Cytoscape. Gene ontology(GO) term enrichment analysis and Kyoto encyclopedia of genes and genomes(KEGG) pathway enrichment analysis were performed based on Metascape. Finally, molecular docking of the chemical components(high degree) with core therapeutic targets was carried out by AutoDock vina. The results showed 88 compounds of SR and PCC(including baicalin, wogonoside, berberine and phellodendrine) and 30 targets of the pair in the treatment of psoriasis. The 30 targets mainly involved the biological processes such as neutrophil mediated immunity(GO: 0002446) and T cell activation(GO: 0042110), and the signaling pathways such as metabolism of xenobiotics by cytochrome P450(hsa00980), apoptosis(hsa04210), and PI3 K-Akt signaling pathway(hsa04151). The results of molecular docking demonstrated that the main active components can spontaneously bind to the targets and the binding energy of 46 components with epidermal growth factor receptor(EGFR) was less than-8 kcal·mol~(-1). According to the PPI analysis, EGFR may be a key target for the treatment of psoriasis. Active components such as baicalin and berberine had high binding affinity with EGFR. This study preliminarily revealed the multi-component, multi-target and multi-pathway mechanism of SR-PCC drug pair in the treatment of psoriasis, which provided theoretical basis for the research on the mechanism of the drug pair in the treatment of psoriasis.

Strategies for designing organic fluorescent probes for biological imaging of reactive carbonyl species.

Reactive carbonyl species (RCS) are involved not only in diverse physiological pathways but also in various pathological processes, including Alzheimer's disease, diabetes, cardiovascular disease, and other malignant diseases. Therefore, it is essential to develop a simple and sensitive technology which can be employed to selectively monitor RCS in living biological samples, such as living cells, tissues, and animals. The subtle changes in the concentration of RCS in organisms can be detected by this technique. In this review, the design strategies of the typical examples of RCS fluorescent probes are highlighted and discussed. These advanced RCS probes may set the foundation for biomedical research on dynamic real-time monitoring of RCS in living systems.

Rational Design of a Reversible Fluorescent Probe for Sensing Sulfur Dioxide/Formaldehyde in Living Cells, Zebrafish, and Living Mice.

Living systems contain a diverse array of molecules and ions undergoing dynamic changes by a web of interacting chemical reactions. Sulfur dioxide (SO2) and formaldehyde (FA) can be generated endogenously in living organisms to maintain their homeostasis, but aberrant production of these species is implicated with some critical diseases. The dynamic interaction between SO2 and FA on the overall health and disease of living organisms remains challenging to elucidate owing to a dearth of methods for monitoring dynamic fluctuation of these transient species. Herein, we present the rational design, synthesis, and photophysical property studies of the probe (CaP), the first reversible fluorescent probe for investigating the dynamics changes of SO2 and FA. Importantly, the highly desirable attributes of the robust probe CaP (such as ultrafast response to SO2 in less than 5 s, swift restoration by FA in less than 1 min) make it possible to reversibly monitor the dynamic fluctuation of endogenous SO2 and FA in real-time in living cells for the first time. Moreover, we demonstrate the utility of this unique probe to detect the fluctuations of SO2 and FA in living zebrafish and murine species. This work provides a powerful chemical tool for monitoring the dynamic interaction of endogenous SO2 and FA, which will pave an avenue for interrogating the intersecting correlation between SO2 and FA in health and disease states.

Development of a Highly Selective Two-Photon Probe for Methylglyoxal and its Applications in Living Cells, Tissues, and Zebrafish.

Methylglyoxal (MGO) is one of the most important active carbonyl compounds in living organisms. It is a metabolic by product of glycolysis. MGO participates in glycosylation of proteins and nucleic acids to trigger carbonyl stress, inducing pathological status and even exacerbateing the development of chronic degenerative diseases. In order to study the diseases caused by MGO, it is meaningful for us to develop methods that could efficiently detect MGO. In our work, a new two-photon fluorescent turn-on probe which named NP has been designed which was made up of naphthalimides dye as the two-photon fluorescent platform and the o-phenylenediamine as recognition site. When reacted with MGO, NP showed excellent sensitivity and selectivity. Based on the two-photon fluorescence imaging technology, NP has firstly successful application in living cells, tissues and zebrafish to detecting MGO.

Discriminating Live and Dead Cells in Dual-Color Mode with a Two-Photon Fluorescent Probe Based on ESIPT Mechanism.

Discrimination of live and dead cells is an important task in biological, pathological, medical, and pharmaceutical studies. In this work, we have developed a novel fluorescent probe DACA that can discriminate live and dead cells in a dual-color mode for the first time. DACA can stain dead cells with blue fluorescence peaked at 440 nm, while it can also label live cells with orange emission peaked at 570 nm. Compared with one-color fluorescent probes, such a dual-color probe can efficiently avoid false positive results from cellular autofluorescence and misleading signals brought by inhomogeneous staining, and thus can supply more accurate information in biological applications. By means of DACA, the health status of tumor cells pretreated by H2O2 and ultraviolet radiation has been successfully detected and imaged. Moreover, DACA and the hydrolyzed product exhibit excellent two-photon properties. Live and dead cells, as well as the zebrafishes, have been discriminated with dual emission colors under one- and two-photon microscope. These results demonstrate that DACA is a powerful tool for dual-color distinguishing live and dead cells in vitro and in vivo.

A Unique "Integration" Strategy for the Rational Design of Optically Tunable Near-Infrared Fluorophores.

Fluorescence imaging is a rapidly growing technique for noninvasive imaging of biological molecules and processes with high spatial and temporal resolution. For effective biological imaging, it is essential and important to develop robust fluorescent dyes, in particular, near-infrared (NIR) fluorescent dyes with favorable optical properties. Compared with the visible light emitting dyes, NIR dyes have relatively longer emission wavelengths (650-900 nm) with lower energy and are advantageous as imaging agents owing to the minimum photodamage of NIR light to biological samples, deep penetration into tissues, and low interference from autofluorescence of biomolecules. Although great efforts have been devoted to engineer NIR fluorophores, it is still very challenging to regulate their photophysical properties as they often lack optically tunable mechanisms, and this shortcoming considerably restricts the realization of their full potential. Consequently, the rational design of small-molecule optically tunable NIR fluorophores is of high priority and great value. In general, two key characteristics are indispensable for designing excellent optically tunable NIR fluorescent dyes. First, NIR fluorescent dyes should display the maximal absorption and emission located in the NIR region and also have the prominent properties including excellent fluorescence quantum yields, large Stokes shifts, good chemical stability and photostability, low cytotoxicity, and desirable compatibility with biological systems. Second, in principle, functional NIR dyes should also possess optically tunable groups, which can be easily modified to afford responsive sites for the targets of interest. With these considerations in mind, in this Account, we described a unique "integration" strategy for judicious design of the optically tunable NIR fluorophores, which are an intuitive combination of the traditional NIR dyes and the optically tunable mechanisms in the visible light emissive dyes. Thus, the versatile strategy may allow not only retention of the NIR emission properties of NIR dyes but also inheritance of the optically tunable mechanisms from the visible light emissive dyes. By the unique integration strategy, a built-in optically tunable group is strategically installed into the traditional NIR fluorescent dyes to directly tune their optical properties. Herein, we present a concise review of the rational design strategy and biological applications of small-molecule optically tunable NIR fluorescent dyes via the unique integration strategy, and we focused mainly on our work and some representative examples from other groups based on our NIR platforms. This Account includes the detailed integration strategy of each class of the NIR fluorescent dyes, the development of their derivatives, and their imaging applications in living systems.

Two-Photon and Deep-Red Emission Ratiometric Fluorescent Probe with a Large Emission Shift and Signal Ratios for Sulfur Dioxide: Ultrafast Response and Applications in Living Cells, Brain Tissues, and Zebrafishes.

Sulfur dioxide (SO2) is a dangerous environmental pollutant. Excessive intake of it may cause some respiratory diseases and even lung cancer. The development of effective methods for detection of SO2 is of great importance for the environment and physiology. Herein, we have designed and synthesized a novel two-photon (TP) and deep-red emission ratiometric fluorescent probe (CP) for detection of SO2. Notably, the novel probe CP exhibited ultrafast response to SO2 in less than 5 s and displayed a great emission shift (195 nm) and a large emission signal ratio variation (enhancement from 0.1347 to 100.14). In addition, the unique probe was successfully employed for imaging SO2 not only in the mitochondria of living cells but also in brain tissues and zebrafishes.

Dual Site-Controlled and Lysosome-Targeted Intramolecular Charge Transfer-Photoinduced Electron Transfer-Fluorescence Resonance Energy Transfer Fluorescent Probe for Monitoring pH Changes in Living Cells.

Acidic pH is a critical physiological factor for controlling the activities and functions of lysosome. Herein, we report a novel dual site-controlled and lysosome-targeted intramolecular charge transfer-photoinduced electron transfer-Fluorescence resonance energy transfer (ICT-PET-FRET) fluorescent probe (CN-pH), which was essentially the combination of a turn-on pH probe (CN-1) and a turn-off pH probe (CN-2) by a nonconjugated linker. Coumarin and naphthalimide fluorophores were selected as donor and acceptor to construct the FRET platform. Hydroxyl group and morpholine were simultaneously employed as the two pH sensing sites and controlled the fluorescence of coumarin and naphthalimide units by ICT and PET, respectively. The sensing mechanism of CN-pH to pH was essentially an integration of ICT, PET, and FRET processes. Meanwhile, the morpholine also can serve as a lysosome-targeted group. By combining the two data analysis approaches of the ratios of the two emission intensities (R) and the reverse ratio R' (R' = 1/R), the fluorescent ratio of CN-pH can show proportional relationship to pH values in a very broad range from pH 4.0 to 8.0 with high sensitivity. The probe has been successfully applied for the fluorescence imaging of the lysosomal pH values, as well as ratiometrically visualizing chloroquine-stimulated changes of intracellular pH in living cells. These features demonstrate that the probe can afford practical application in biological systems.

Lysosome-Targeted Turn-On Fluorescent Probe for Endogenous Formaldehyde in Living Cells.

As one of the simplest reactive carbonyl species, formaldehyde is implicated in nervous system diseases and cancer. Organelles play crucial roles in various physiological processes in living cells. Accordingly, the detection of endogenous formaldehyde at the subcellular level is of high interest. We herein describe the development of the first organelle-targeted fluorescent formaldehyde probe (Na-FA-Lyso). The new probe exhibits favorable features including a large fluorescence enhancement (about 350-fold) and a fast response to formaldehyde. Significantly, the novel probe Na-FA-Lyso was employed to visualize the endogenous formaldehyde in the lysosomes in living cells for the first time.

Development of fluorescent probes based on protection-deprotection of the key functional groups for biological imaging.

Recently, the strategy of protection-deprotection of functional groups has been widely employed to design fluorescent probes, as the protection-deprotection of functional groups often induces a marked change in electronic properties. Significant advances have been made in the development of analyte-responsive fluorescent probes based on the protection-deprotection strategy. In this tutorial review, we highlight the representative examples of small-molecule based fluorescent probes for bioimaging, which are operated via the protection-deprotection of key functional groups such as aldehyde, hydroxyl, and amino functional groups reported from 2010 to 2014. The discussion includes the general protection-deprotection methods for aldehyde, hydroxyl, or amino groups, as well as the design strategies, sensing mechanisms, and deprotection modes of the representative fluorescent imaging probes applied to bio-imaging.

Development of a Two-Photon Fluorescent Probe for Imaging of Endogenous Formaldehyde in Living Tissues.

Investigation of the physiological and pathological functions of formaldehyde (FA) are largely restricted by a lack of useful FA imaging agents, in particular, those that allow detection of FA in the context of living tissues. Herein, we present the rational design, synthesis, and photophysical property studies of the first two-photon fluorescent FA probe, Na-FA. Importantly, the highly desirable attributes of the probe Na-FA (such as a very large turn-on signal (up to 900-fold), a low detection limit, and a very fast onset imparted by the unique design aspects of the probe), make it possible to monitor endogenous FA in living tissues for the first time. Furthermore, sodium bisulfite was identified as a simple and convenient inhibitor of FA within biological environments.

Construction of a Near-Infrared Fluorescent Turn-On Probe for Selenol and Its Bioimaging Application in Living Animals.

As selenocysteine (Sec) carries out the majority of the functions of the various Se-containing species in vivo, it is of high importance to develop reliable and rapid assays with biocompatibility to detect Sec. Herein, an NIR fluorescent turn-on probe for highly selective detection of selenol was designed and synthesized. The probe exhibits large turn-on signal upon treatment with selenocysteine (R-SeH), and it was further demonstrated that the new NIR fluorescent probe can be employed to image selenol in living animals.

Synthesis, anticancer activity and DNA-binding properties of novel 4-pyrazolyl-1,8-naphthalimide derivatives.

A novel series of 4-pyrazolyl-1,8-naphthalimide derivatives have been designed and facilely synthesized. For anticancer activity in vitro, most of the compounds were found to be more toxic against human mammary cancer cells (MCF-7) than human cervical carcinoma cells (Hela) and human lung cancer cells (A549). Compounds 4i, 4h, 4b and 4a showed improved cytotoxic activity against MCF-7 cells over amonafide, in particular compounds 4i and 4h, the IC50 values of which against cell lines of MCF-7 were 0.51 µM and 0.79 µM, respectively. The DNA-binding properties of 4i were investigated by UV-vis, fluorescence, and Circular Dichroism (CD) spectroscopies and thermal denaturation. The results indicated that compound 4i as the DNA-intercalating agent exhibited middle binding affinity with CT-DNA.

Ingenious fluorescent probes for biogenic amine and their applications in bioimaging and food spoilage detection.

Food safety issues have received much attention. Biogenic amines are considered important markers of food spoilage. Accurate detection of biogenic amines is important for food quality monitoring. Herein, we developed two coumarin-difluoroboron ß-diketonate hybrid probes, 1 and 2, for detection of amines. Both probes possess large conjugated structures and donor-acceptor-donor configuration, exhibiting solvatochromic effects due to intramolecular charge transfer mechanism. Upon reaction with amines, the boron atom in difluoroboron unit can interact with lone pair electrons of nitrogen atom, thus resulting in significant changes in absorption and fluorescence properties. These probes were successfully utilized to image amine in live cells and liver tissues. Moreover, by photographing probe-loaded food extract supernatant, we establish the relationship between color parameters and food storage time, which can easily indicate food spoilage process. This work and its findings hold promise for providing potential strategies for real-time and convenient detection of food freshness.

A colorimetric and fluorescent sensor for non-destructive screening of the freshness of shrimp and fish.

The freshness of fish and shrimp is closely associated with food safety, hence it is a wide concern to develop a facile and effective method for fast, non-destructive and visual screening the freshness of fish and shrimp. Herein, we developed a chromogenic and fluorogenic sensor (RFCC) based on resorufin for sensing of biogenic amines including cadaverine and putrescine. RFCC underwent aminolysis with cadaverine or putrescine, displaying a remarkable fluorescence turn on response at 593 nm along with obvious color change from colorless to pink. RFCC was fabricated into test strips to sense cadaverine vapor, and the RGB value of test strips showed a good linear relationship with the concentration of cadaverine (0.5 - 8.2 × 103 ppm). The RFCC tag was used to in situ screen the freshness of fish and shrimp according to obvious fluorescence change, and satisfactory results were achieved. Furthermore, this test strip was validated by total volatile base nitrogen (TVBN), providing a simple, low cost and portable tool to screen the freshness of fish and shrimp for consumers and suppliers without expensive instrumentation.

A new NIR emission mitochondrial targetable fluorescent probe and its application in detecting viscosity changes in mouse liver and kidney injury.

As important organs of the human body, the liver and kidneys ensure the stability of the internal environment of the body and allow the body to carry out normal metabolism. The lack of effective methods for early diagnosis of liver and kidneys diseases is an important reason for delaying the treatment of kidney diseases. Therefore, the development of a simple, non-invasive and effective test is essential for the early diagnosis of liver and kidneys disease. Herein, a new viscosity fluorescent probe, Mito-ND, is rationally designed and synthesized in order to solve the practical problem of realizing the diagnosis of liver and kidneys diseases. The constructed fluorescent probe Mito-ND has the advantages of near-infrared emission, mitochondrial localization, high chemical and photo-stable properties, and sensitive viscosity detection performance, etc. Using this fluorescent probe, besides in vitro cell viscosity fluorescence imaging, the viscosity fluorescence imaging of mouse liver and kidney injury are also achieved for the first time. Mito-ND provides more accurate tools for the non-invasive diagnosis of viscosity-related diseases such as liver injury and kidney injury. Therefore, Mito-ND provides more accurate detection techniques for the early diagnosis of liver and kidney diseases such as liver injury and kidney injury.