Search

Nitroxyl (HNO), the reduced and protonated form of nitric oxide (NO), has recently been identified as an interesting and important signaling molecule in biological systems. However, research on its biosynthesis and bioactivities are hampered by the lack of versatile HNO detection methods applicable to living cells. In this report, two new near-infrared (NIR) probes were designed and synthesized for HNO imaging in living cells. One of the probes was found to display high sensitivity towards HNO, with up to 67-fold of fluorescence increment after reaction with HNO. The detection limit was determined to be as low as 0.043 μM. The probe displayed high selectivity towards HNO over other biologically related species including metal ions, reactive oxygen species, reactive nitrogen species and reactive sulfur species. Furthermore, the probe was shown to be suitable for imaging of exogenous and endogenous HNO in living cells. Interestingly, the probe was found to be mainly localized in lysosomes. We envision that the new NIR probe described here will serve as a useful tool for further elucidation of the intricate roles of HNO in living cells.

This study explored FL-H2S, a novel fluorescein-based H2S donor, as an anti-inflammatory agent. The results demonstrated the efficient release of H2S by FL-H2S, along with its biocompatibility, real-time intracellular H2S release and imaging capability. In vivo experiments using a rat model confirmed the anti-inflammatory effects of FL-H2S, evidenced by reduced foot swelling. We also successfully elucidated the anti-inflammatory mechanism through ELISA and WB analysis. [ABSTRACT FROM AUTHOR]

The unique properties of graphene oxide (GO), such as good water solubility, non‐toxicity, biocompatibility and cell permeability, make GO well suited for a number of biological applications. In this study, we explore the application of GO as an efficient fluorescent quencher for a highly fluorescent organic dye, resorufin (RF). The quenching effect of GO on resorufin is studied by noncovalent and covalent bonding of resorufin, respectively. The fluorescence is completely quenched when resorufin is covalently linked to GO; while resorufin's fluorescence could be still observed through noncovalent bonding to GO sheet. Interestingly, addition of hydrazine into RF‐GO complex causes the fluorescence recovered, providing a potential "OFF‐ON" fluorescence responsive probe for detecting hydrazine in vitro and in living cells. [ABSTRACT FROM AUTHOR]

Fluorescent stapled peptides are important chemical tools for detecting intracellular distribution, protein–protein interactions, and localization of target proteins. These peptides are usually labeled with bulky sized fluorophores through reactive functional groups, which may alter the physical properties and biological activities of peptides. Herein, a unique strategy is developed for synthesizing new stapled peptides with built‐in fluorescence. The stapled peptides were prepared through Rh‐catalyzed C(sp2)−H olefination in tryptophan (Trp) residues by using pyridine/pyrimidine as the directing groups under mild conditions. This method displays good regioselectivity and high efficiency. Furthermore, as a proof of concept for its biological applications, stapled peptides without additional fluorophore 9 a and 9 b were constructed for a cell imaging study. These peptides displayed strong binding affinity toward integrin αvβ3 in A549 cells by cell imaging experiments. Notably they demonstrated even better anticancer activity than commercial antagonist cyclic (RGDfK). The method will provide robust tools for the peptide macrocyclization field. [ABSTRACT FROM AUTHOR]

Herein, a new fluorescent probe, AE-Phos, is reported for detecting the ALP activity with the combined advantages of aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT). Further detailed fluorescence experiments demonstrated that AE-Phos exhibited excellent selectivity and sensitivity, a large Stokes shift, and a fast response towards ALP. Furthermore, AE-Phos was applied to imaging the ALP activity in different cell lines quantitatively. [ABSTRACT FROM AUTHOR]

A rotor-based probe MRMP-1 was designed and synthesized. MRMP-1 can bind to plasma membranes very quickly and stably with remarkable fluorescence enhancement. It can be used to monitor the dynamic changes in cell membranes in real-time under stimuli conditions. Importantly, MRMP-1 is the first rotor-based fluorescent sensor to label exosomes in living cells. [ABSTRACT FROM AUTHOR]

Light‐up bioorthogonal probes have attracted increasing attention recently due to their capability to directly image diverse biomolecules in living cells without washing steps. The development of bioorthogonal probes with excellent fluorescent properties suitable for in vivo imaging, such as long excitation/emission wavelength, high fluorescence turn‐on ratio, and deep penetration, has been rarely reported. Herein, a series of azide‐based light‐up bioorthogonal probes with tunable colors based on a weak fluorescent 8‐aminoquinoline (AQ) scaffold were designed and synthesized. The azido quinoline derivatives are able to induce large fluorescence enhancement (up to 1352‐fold) after click reaction with alkynes. In addition, the probes could be engineered to exhibit excellent two‐photon properties (δ=542 GM at 780 nm) after further introducing different styryl groups into the AQ scaffold. Subsequent detailed bioimaging experiments demonstrated that these versatile probes can be successfully used for live cell/zebrafish imaging without washing steps. Further in vivo two‐photon imaging experiments demonstrated that these light‐up biorthogonal probe outperformed conventional fluorophores, for example, high signal‐to‐noise ratio and deep tissue penetration. The design strategy reported in this study is a useful approach to realize diverse high‐performance biorthogonal light‐up probes for in vivo studying. [ABSTRACT FROM AUTHOR]

A facile fluorescent probe (NBD-DOP) has been developed to detect hypochlorous acid (HOCl) in this study. The probe consists of a NBD fluorophore and a dopamine moiety that reacts with HOCl specifically. The dopamine group quenches the fluorescence of NBD efficiently through a photoinduced electron transfer (PET) effect. Experimental data showed that NBD-DOP could detect HOCl with ultrafast response, high sensitivity and high selectivity in a wide pH range. The probe could also be used to detect the myeloperoxidase enzyme that produces HOCl. Moreover, NBD-DOP has been applied in the imaging of exogenous and endogenous HOCl in living cells by confocal fluorescence microscopy. [ABSTRACT FROM AUTHOR]

Fluorophores with near-infrared emissions play a crucial role in numerous bioimaging and biosensing applications, owing to their deep penetration depths, low auto-fluorescence, and minimal tissue damages. Herein, the rational development of a new class of near-infrared fluorophores with bright one-photon and two-photon emissions at ≈740 nm, large Stokes shifts (≈80 nm), significant two-photon action absorption cross-section (≈185 GM at 820 nm), excellent water solubility, outstanding photostability, and low toxicity is reported. Their biological applications in mitochondrial labelling, deep tissue imaging, and H2S detection in live cells and mice are also demonstrated. In addition, a rational design strategy for enlarging the Stokes shifts and enhancing two-photon emissions of these fluorophores is presented. These fluorophores will serve as a useful platform for developing novel imaging and sensing agents, and the design methodologies will inspire the molecular engineering of abundant high-performance near-infrared fluorophores. [ABSTRACT FROM AUTHOR]

Resazurin (RZ) is a low-toxic redox-sensitive indicator that is weakly fluorescent but becomes strongly fluorescent after reducing to resorufin (RS). The focal point attracting the attention of researchers to this indicator is connected to its excellent sensitivity to a wide range of physical and chemical reaction properties. The sensitive reduction of RZ causing the colour/fluorescence change could be readily triggered by i) biochemical agents or enzymes found in the mitochondria of both the prokaryotic and eukaryotic cells ii) chemical agents like the electrochemical redox species or reductants, single molecule catalytic species, and iii) some physical properties like UV radiation, pH, etc. Interestingly, these redox reaction activators are a segment of most biochemical, electrochemical, photochemical, and microbial reaction processes. Hence, they have been exploited to develop quite several analytical assays for analyzing photo-catalysts, food, drugs, nanoparticles catalyzed reactions, single-molecule detection, and the metabolic activity of a wide range of micro-organisms. • Resazurin sensitive redox reactions find applications in cell viability. • The sensitivity to cytoplasmic enzymes provides swift food testing and drug screening. • The photosensitivity of resazurin affords quick assessment of photo-catalysts. • The staining tendency useful in fluorescent labels-assisted single molecule detection. [ABSTRACT FROM AUTHOR]

Copper (II) is one of the most of important cofactors for numerous enzymes and has captured broad attention due to its role as a neurotransmitters for physiological and pathological functions. In this article, we present a reaction-based fluorescent sensor for Cu 2+ detection ( NIR-Cu ) with near-infrared excitation and emission, including probe design, structure characterization, optical property test and biological imaging application. NIR-Cu is equipped with a functional group, 2-picolinic ester, which hydrolyzes in the presence of Cu 2+ with high selectivity over completed cations. With the experimental conditions optimized, NIR-Cu ( 5 μM ) exhibits linear response for Cu 2+ range from 0.1 to 5 μM, with a detection limit of 29 nM. NIR-Cu also shows excellent water solubility and are highly responsive, both desirable properties for Cu 2+ detection in water samples. In addition, due to its near-infrared excitation and emission properties, NIR-Cu demonstrates outstanding fluorescent imaging in living cells and tissues. [ABSTRACT FROM AUTHOR]

• A robust strategy for probe design with dual-quenching groups in one probe. • The strategy has been applied for designing HOCl fluorescent probe successfully. • The strategy can both enhance the probe's sensitivity and selectivity significantly. • The detection limit for HOCl is as low as 3.5 nM. • Two-photon probe has been used to detect HOCl in living cells and kidney tissues. We report herein fluorescent probes equipped with dual-quenching groups exhibiting superior sensitivity than probes with mono-quenching groups. Importantly, with this strategy, the probe with dual-quenching groups react with HOCl through two distinct reaction mechanisms, which reduce the plausible side reactions with other competing analytes and enhance the probe's selectivity. As a proof-of-concept study, we designed and synthesized a probe with dual-quenching groups DQ-HOCl to detect HOCl, which is one of the most important ROS and linked with a number of diseases. In addition, two control probes with mono-quenching groups, MQ-HOCl-1 and MQ-HOCl-2 , were also synthesized for comparison purpose. Fluorescent assays demonstrated that DQ-HOCl indeed shows ultra-high sensitivity and selectivity compared with probes with mono-quenching groups. Furthermore, the probe has been successfully utilized to imaging exogenous/endogenous HOCl in living cells. Moreover, DQ-HOCl was applied to visualize HOCl in kidney tissues from rat due to the increased penetration depth and lower tissue autofluorescence from the nature of two-photon probes. [ABSTRACT FROM AUTHOR]

Based on thiolysis of the NBD amine, a H 2 S-triggered prodrug has been designed and synthesized for localized production of ciprofloxacin under micromolar H 2 S. Activation of the prodrug can be monitored through fluorescence in real-time. We envision that thiolysis of the NBD amine could be readily used for development of other H 2 S-triggered prodrugs in the future. [ABSTRACT FROM AUTHOR]