A Turn-on Fluorescent Probe for the Discrimination of Cys/Hcy and GSH With Dual Emission Signals

A turn-off xanthene-based fluorescent probe for detection of cysteine and its practical application in bioimaging and food samples

BACKGROUND

Cys, as an essential amino acid that can be ingested from daily food, plays an important role in maintaining the oxidative balance in cells. Abnormal Cys levels in organisms will lead to various diseases. Therefore, it is of great significance to construct a fluorescent probe that can detect Cys levels in food and biological systems.

RESULTS

Here, a turn-off type probe TA had been successfully synthesized, which attached diethylamine as the strong electron donor, acrylate as the weak electron donor, and xanthene as the π-bridge. TA showed wonderful selectivity, low detection limit, good photostability and well live-cell compatibility for Cys by reducing acrylate group to hydroxyl group of TAOH. The reaction mechanism was demonstrated by 1H NMR, ESI-MS spectra, pH-dependent response experiments, and DFT calculations. Importantly, the reason why TAOH exhibited no fluorescence was the disappearance of the ICT effect in the molecule due to the dominant existence of spirocyclic state of TAOH. In addition, the probe can be used not only for the imaging detection of Cys in A549 cells and zebrafish, but also for the detection of Cys levels in food samples.

SIGNIFICANCE

This work provides a new idea for the design of Cys fluorescent probe, which may be beneficial to the comprehension of the potential mechanism of novel fluorescent probe.

Discovery of the cysteine dynamics during the development and treatment of diabetic process by fluorescent imaging

Herein, a novel fluorescent probe RhoDCM was developed for monitoring the cysteine (Cys) dynamics. For the first time, the Cys-triggered implement was applied in relatively complete diabetic mice models. The response of RhoDCM towards Cys suggested advantages including practical sensitivity, high selectivity, rapid reaction, and steadiness in various pH and temperature conditions. RhoDCM could basically monitor the intracellular Cys level, both exogenous and endogenous. It could further monitor the glucose level via detecting consumed Cys. Furthermore, the diabetic mice models including the no diabetic control group, the induced model groups by streptozocin (STZ) or alloxan, and the treatment groups induced by STZ and treated with vildagliptin (Vil), dapagliflozin (DA), or metformin (Metf) were constructed. The models were checked by oral glucose tolerance test and significant liver-related serum indexes. Based on the models, the in vivo imaging and penetrating depth fluorescence imaging both indicated that RhoDCM could characterize the status of the development and treatment in the diabetic process via monitoring the Cys dynamics. Consequently, RhoDCM seemed beneficial for inferring the order of severity in the diabetic process and evaluating the potency of therapeutic schedules, which might be informatic for correlated investigations.

Development of an Endoplasmic Reticulum-targeting Fluorescent Probe for the Imaging of Superoxide Anion in Living Cells

Superoxide anion (O₂^•-) is an important reactive oxygen species (ROS), and plays critical roles in biological systems. ER stress has close relation with many metabolic diseases, and could lead to the abnormal production of ROS including O₂^•-. Herein, we present an ER-targeting probe (ER-Tf) for the detection of O₂^•- in living cells. The probe ER-Tf used triflate as the response site for O₂^•-, and employed p-methylbenzenesulfonamide as ER-targeting moiety. In response to O₂^•-, the triflate of the probe ER-Tf converted to hydroxyl group, providing strong blue emission under the excitation of ultraviolet light. The probe ER-Tf exhibited high sensitivity and selectivity to O₂^•-. Bioimaging experiments showed that the probe ER-Tf can be applied to detect O₂^•- at ER, and also demonstrated that rotenone could increase the generation of O₂^•- in living cells, while the O₂^•- level at ER showed no remarkable change during ferroptosis.

A novel cysteine fluorescent probe with large stokes shift for imaging in living cells, zebrafish and living mice

The small molecule biological thiols, such as Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play crucial roles in maintaining various cellular vital activities. In the organism, abnormal levels of small-molecule biological thiols have been associated with a variety of diseases. Therefore, quantitative determination of biological thiols, especially Cys, is significant for understanding their functions in various biological processes. Thus, in this work we designed a new fluorescent probe Ty-Cys1 with a large Stokes shift of 207 nm to monitor Cysteine. The maximum absorption wavelength of Ty-Cys1 was 418 nm, and the maximum emission wavelength was 625 nm. Significantly, the novel probe Ty-Cys1 was effectively in detecting of Cys changes in living cells, zebrafishes, and living mice.

Recent Research Progress of Red-Emitting/Near-Infrared Fluorescent Probes for Biothiols

Small-molecule biological thiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), occupy a vital position in physiological and pathological activities. Abnormal fluctuations of their concentrations are often closely connected with...

A ratiometric fluorescent probe based on two-isophorone fluorophore for detecting cysteine

The key biological thiol, cysteine (Cys), which can participate in many physiological and pathological processes in the human body, has also been proofed to have considerable effects on redox homeostasis...

A novel ratiometric AIE-based fluorescent probe for specific detection of Hcy/Cys and imaging of living cells in vivo

The sensing mechanism toward Hcy/Cys is realized based on the condensation reaction, which breaks CN to form a thiazolidine adduct.