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.

A Reaction-Based Fluorescent Probe for Imaging of Native Hypochlorous Acid.

Hypochlorous acid (HOCl), one of the reactive oxygen species (ROS), is highly reactive and short-lived. It is a challenge to dynamic monitor HOCl activity in living systems. Hence, we synthesized a new fluoresce nt probe RF1 based on protection of the hydroxyl group by N,N-dimethylthiocarbamate recognition group, which reached a low fluorescence background signal and highly sensitive property. On account of the electrophilic addition of Cl+ to the sulfide of thiocarbamate moiety, probe RF1 was converted to resorufin and triggered emitting bright. RF1 showed not only the highly sensitive and selective response to HOCl in vitro, but also can be applied in environmental water samples and detected HOCl by test strips. Besides, the ability of RF1 monitoring HOCl in HeLa cells by exogenous simulation and tracing native HOCl in macrophages cells were also explored.

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.

Fluorescence detection of intracellular pH changes in the mitochondria-associated process of mitophagy using a hemicyanine-based fluorescent probe.

Intracellular pH behaves as a vital parameter in the physiological and pathological processes. Novel small molecule probes for precise and dynamic monitoring of pH fluctuations in cellular physiological processes are still highly required. Herein, we present a hemicyanine-based probe (HcPH) detection of the pH changes during the intracellular process of mitochondria-associated autophagy. HcP-H exhibits highly reversible and ratiometric fluorescence detection of pH variation due to the deprotonation/protonation process, showing orange fluorescence (λem = 557 nm) in basic media (pH 8.0) and green fluorescence (λem = 530 nm) in acidic media (pH 6.2), respectively. Organelle localization experiment in HeLa cells demonstrates that this probe could selectively accumulate in mitochondria, showing almost overlap with that of Mito-Tracker Green FM. More importantly, Fluorescence imaging of HcP-H in HeLa cells subjected to the nutrient deprivation has demonstrated that this probe could monitor the intracellular pH changes in the mitochondria-associated process of mitophagy. It is clearly confirmed that HcP-H would serve as a promising fluorescent probe for tracing mitophagy in living cells.