A new "off-on" NIR fluorescence probe for determination and bio-imaging of mitochondrial hypochlorite in living cells and zebrafish.

Hypochlorite anion (ClO-) has been recognized as host defense destructing incursive bacteria and pathogens, a signal molecule inducing occurrence of apoptosis and a noxious agent when it is overproduced. It is significant to detect ClO- in mitochondria for getting meaningful physiological and pathological information. Compared with the fluorescence probes of emission wavelength in ultraviolet or visible region, those with near-infrared (NIR) fluorescence signal are advantageous due to the deeper tissue penetrability and less photo-bleaching effect. In this work, a new "off-on" NIR ClO--specific fluorescence probe (Mito-NClO) especially located in mitochondria was designed and synthesized by condensation of diaminomaleonitrile with a new fluorophore (Mito-NCHO). A marked "turn-on" NIR fluorescence signal was observed on account of the oxidation of the imine bond by NaClO. Moreover, in the range from 0 to 20 µM, this probe had the capability to quantitatively detect ClO- with a detection limit as low as 90.2 nM. Additionally, the probe exerted other excellent properties, including larger stokes shift (117 nm), better aqueous solubility, high selectivity toward ClO-, rapid response and selective mitochondrial location. Furthermore, the bio-imaging experiments clearly demonstrated that Mito-NClO facilitated the visualization of exogenous and endogenous ClO- in living HeLa cells and zebrafish model. Therefore, we speculate that the probe Mito-NClO can be served as an ideal tool for the monitoring of ClO- in biosystems.

A novel "turn-on" mitochondria-targeting near-infrared fluorescent probe for H2S detection and in living cells imaging.

Hydrogen sulfide (H2S) has been considered to be involved in cytoprotective processes and redox signaling. It is very meaningful to track and analyze it in mitochondria. Herein, we report a novel "turn-on" mitochondria-targeting near-infrared fluorescent probe (Mito-NIR-SH) for detection of H2S in living cells, which was designed and synthesized by introducing 2,4-dinitrophenyl as fluorescence quenching group and H2S response moiety into Changsha near-infrared fluorophore (CS-OH). The structure of the fluorophore and the probe were characterized by 1H NMR, 13C NMR and mass spectrometry. Meanwhile, Mito-NIR-SH could quantitatively detect H2S at concentrations ranging from 0 to 30 µM with a detection limit as low as 89.3 nM, showing good chemical stability, fast "turn-on" response, selectively mitochondrial location, as well as high sensitivity and selectivity toward H2S. Based on this, it was successfully applied to imaging exogenous and endogenous H2S in living HeLa cells via confocal fluorescence microscopy.

A novel "turn-on" mitochondria-targeting near-infrared fluorescent probe for determination and bioimaging cellular hydrogen sulfide.

Hydrogen sulfide (H2S) has been regarded as an important gas transmitter playing vital role in cytoprotective processes and redox signaling. It is very meaningful to monitor and analyze it in biosystem for obtaining important physiological and pathological information. Despite numerous fluorescent probes for cellular H2S have been reported in past decades, only a few have capability to detect mitochondrial H2S with near-infrared (NIR) emission. Therefore, a new mitochondria-targeting NIR fluorescent probe (Mito-NSH) for detection of cellular H2S was developed by introducing 2,4-dinitrophenyl ether into a novel dye (Mito-NOH). A large "turn-on" NIR fluorescence response was obtained due to thiolysis of ether to hydroxyl group when Mito-NSH was treated with NaHS. Moreover, Mito-NSH could quantitatively detect H2S at concentration ranging from 0 to 30 µM with a detection limit of 68.2 nM, and it exerts some superior optical properties, such as large stokes shift (107 nm), highly selectively mitochondria location, fast response and high selectivity to H2S. More impressively, it was successfully applied to imaging exogenous and endogenously generated H2S in living HeLa cells via confocal fluorescence microscopy.

Design, synthesis and biological evaluation of dual acetylcholinesterase and phosphodiesterase 5A inhibitors in treatment for Alzheimer's disease.

With the recent research advances in molecular biology and technology, multiple credible hypotheses about the progress of Alzheimer's disease (AD) have been proposed; multi-target drugs have emerged as an innovative therapeutic approach for AD. Current clinical therapy for AD patients is mainly palliative treatment targeting acetylcholinesterase (AChE). Inhibition of phosphodiesterase 5A (PDE5A) has recently been validated as a potentially novel therapeutic approach for Alzheimer's disease (AD). In this work, series of new compounds were designed, synthesized and evaluated as dual cholinesterase and PDE5A inhibitor. Biological results revealed that some of these compounds display good biological activities against AChE with IC50 values about 44.67-169.80nM (donepezil IC50 50.12nM). Notably, compound 12 presented potent activities against PDE5A with IC50 values about 50µM (sildenafil IC50 12.59µM), and some of these compounds showed low cell toxicity to A549 cells in vitro.

Multipotent AChE and BACE-1 inhibitors for the treatment of Alzheimer's disease: Design, synthesis and bio-analysis of 7-amino-1,4-dihydro-2H-isoquilin-3-one derivates.

In this paper, the preparation of a new class of multi-target-directed ligands (MTDLs) based on a 7-amino-1,4-dihydro-2H-isoquilin-3-one, whose lead (compound I) showed promising properties in acetylcholinesterase (AChE) inhibitory activity [1], is described. The results of in vitro activities and molecular docking demonstrated that the target molecule (compounds 10a-n) with three parts of aromatic moieties and appropriate structural length can interact with aromatic residues in catalytic active site (CAS), peripheral anionic site (PAS) and the channel of AChE. And the introduce of connecting amide bonds, enables the target molecules provide sufficient hydrogen bond donors and acceptors to interact with the catalytic site of BACE-1. Notably, compound 10d exerted excellent AChE inhibition (IC50 = 18.93 ± 1.02 pM, 181-fold more inhibitory effect compared with donepezil), BACE-1 inhibition (97.68 ± 8.01% at 20 µM), and good metal chelating property, which can be chosen as lead compound for further optimization of novel small ligand for the treatment of Alzheimer's disease.

A naphthalene-based two-photon fluorescent probe for selective and sensitive detection of endogenous hypochlorous acid.

An efficient naphthalene-based two-photon fluorescent probe for endogenous HClO has been reported in the present study, which consists of a 6-(2-benzothiazolyl)-2-naphthalenol fluorophore connected with a 4-aminophenol (the fluorescence quenching and response group). This probe exhibits a high selectivity and excellent sensitivity with a detection limit of 7.6nM over other reactive oxygen species and analyte species, and the fluorescence intensity enhanced 103-fold when responsed. Furthermore, it was successfully used for two-photon imaging of endogenous HClO in live cells with high-resolution.