Novel cascade reaction-based fluorescent cyanine chemosensor for cysteine detection and bioimaging in living system.

Precise detection of intracellular Cys will be helpful to accurately assess the physiological functions in the physiological and pathological processes. Herein, a new probe Meoeth-Cy-OBz-oCl capable of Cys sensing with high selectivity over other mercaptoamino-acid molecules including Hcy and GSH was developed. The studies on sensing mechanism supported thiols-induced SNAr substitution-rearrangement cascade reaction which allowed discriminating Cys from Hcy/GSH. And its preferential fluorescence response of Meoeth-Cy-OBz-oCl to intracellular Cys was also achieved by means of fluorescence imaging in HeLa cells. Besides, Meoeth-Cy-OBz-oCl was confirmed possessing mitochondria-targeting ability in living cells. In addition, fluorescence imaging in BALB/c mice revealed that Meoeth-Cy-OBz-oCl could visually monitor the variation of Cys in vivo.

A Water-soluble Near-infrared Fluorescent Probe for Cysteine/Homocysteine and Its Application in Live Cells and Mice.

A near-infrared (NIR) and water-soluble probe was synthesized and studied for the detection of Cys/Hcy in aqueous solution, living cells and mice. The probe was composed of cyanine derivative as the NIR fluorescent reporting unit and pyrimidiny-thioether moiety as the Cys/Hcy responsive unit. Treatment with Cys/Hcy induced the formation of sulfur-substituted products, then intramolecular rearrangement reaction would occur to produce amino-substituted products and resulting in enhanced red fluorescence emissions. It could be applied to sense Cys/Hcy both in solution with the detection limit of 0.17 µM (or 0.32 µM) and in living cells. Cell imaging experiments proved that such a probe exhibited good cell penetration. In addition, the probe could detect Cys/Hcy in live mice with strong turn-on fluorescent response.

Synthesis and biological evaluation of quinoxaline derivatives as tubulin polymerization inhibitors that elevate intracellular ROS and triggers apoptosis via mitochondrial pathway.

A series of novel quinoxaline derivatives were synthesized and evaluated for their antiproliferative activity in three human cancer cell lines. Compound 12 exhibited the most potent antiproliferative activity with IC50 in the range of 0.19-0.51 µM. The compound inhibited tubulin polymerization and disrupted the microtubule network, leading to G2/M phase arrest. Furthermore, compound 12 induced ROS production and malfunction of mitochondrial membrane potential. Compound 12 led to cancer cells apoptosis in a dose-dependent manner. Western blot analysis showed that compound 12 induced up-regulation of p21 and affected the expression of cell cycle-related proteins. The binding mode was also probed by molecular docking.

A dual-selective fluorescent probe for discriminating glutathione and homocysteine simultaneously.

Homocysteine (Hcy) and glutathione (GSH) play important roles in a variety of physiological and pathological processes. Abnormal levels of Hcy and GSH are related to various diseases. Fluorescent probes for detecting them with sensitive and selective are highly desirable. However, efficient discrimination of Hcy and GSH is still a challenge for their similar molecular structures and chemical properties. Herein, we report a naphthalimide and sulfonyl benzoxadiazole (SBD) based dual-selective fluorescent probe for Hcy and GSH over other amino acids. The probe exhibited weak fluorescence (Φ = 0.075, in DMSO) at 490 nm and fluorescence enhancement upon addition of GSH (1-20 µM) with a detection limit of 0.8 µM. The probe also exhibited ratiometric fluorescence responses for Hcy (fluorescence at 490 nm decreased and fluorescence at 552 nm increased). The fluorescence intensity ratio (I552/I490) showed a good linear correlation with the Hcy concentrations in range of 3-20 µM and the detection limit was 0.1 µM. Moreover, this probe was successfully utilized for monitoring Hcy and GSH in living cells.

A novel NBD-based fluorescent turn-on probe for the detection of cysteine and homocysteine in living cells.

Biothiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), are involved in a number of biological processes and play crucial roles in biological systems. Thus, the detection of biothiols is highly important for early diagnosis of diseases and evaluation of disease progression. Herein, we developed a new turn-on fluorescent probe 1 based on 7-nitro-2,1,3-benzoxadiazole (NBD) with high selectivity and sensitivity for Cys/Hcy on account of nucleophilic substitution and Smiles rearrangement reaction. The probe could sense Cys/Hcy rapidly, the intensity of fluorescence increased immediately within 1min. Furthermore, the probe is low toxic and has been successfully applied to detect intracellular Cys/Hcy by cell fluorescence imaging in living normal and cancer cells.

Synthesis and biological evaluation of N-substituted 3-oxo-1,2,3,4-tetrahydro-quinoxaline-6-carboxylic acid derivatives as tubulin polymerization inhibitors.

A series of novel N-substituted 3-oxo-1,2,3,4-tetrahydro-quinoxaline-6-carboxy- lic acid derivatives were synthesized and evaluated for their biological activities. Among all synthesized target compounds, 13d exhibited the most potent antiproliferative activity against HeLa, SMMC-7721, K562 cell line (IC50 = 0.126 µM, 0.071 µM, 0.164 µM, respectively). Furthermore, compound 13d inhibited tubulin polymerization (IC50 = 3.97 µM), arrested cell cycle at the G2/M phase and induced apoptosis. The binding mode at the colchicine binding site was also probed. These studies provided a new molecular scaffold for the further development of antitumor agents that target tubulin.

A nontoxic, photostable and high signal-to-noise ratio mitochondrial probe with mitochondrial membrane potential and viscosity detectivity.

Herein, we reported a yellow emission probe 1-methyl-4-(6-morpholino-1, 3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) pyridin-1-ium iodide which could specifically stain mitochondria in living immortalized and normal cells. In comparison to the common mitochondria tracker (Mitotracker Deep Red, MTDR), this probe was nontoxic, photostable and ultrahigh signal-to-noise ratio, which could real-time monitor mitochondria for a long time. Moreover, this probe also showed high sensitivity towards mitochondrial membrane potential and intramitochondrial viscosity change. Consequently, this probe was used for imaging mitochondria, detecting changes in mitochondrial membrane potential and intramitochondrial viscosity in physiological and pathological processes.