Theoretical Investigation of a Coumarin Fluorescent Probe for Distinguishing the Detection of Small-Molecule Biothiols

Monitoring the level of biothiols in organisms would be beneficial for health inspections. Recently, 3-(2'-nitro vinyl)-4-phenylselenyl coumarin as a fluorescent probe for distinguishing the detection of the small-molecule biothiols cysteine/homocysteine (Cys/Hcy) and glutathione (GSH) was developed. By introducing 4-phenyselenium as the active site, the probe CouSeNO2/CouSNO2 was capable of detecting Cys/Hcy and GSH in dual fluorescence channels. Theoretical insights into the fluorescence sensing mechanism of the probe were provided in this work. The details of the electron excitation process in the probe and sensing products under optical excitation and the fluorescent character were analyzed using the quantum mechanical method. All these theoretical results would provide insight and pave the way for the molecular design of fluorescent probes for the detection of biothiols.

Dual Response Site Fluorescent Probe for Highly Sensitive Detection of Cys/Hcy and GSH In Vivo through Two Different Emission Channels

Much research has demonstrated that metabolic imbalances of biothiols are closely associated with the emergence of different types of disease. In view of the significant effect of biothiols, quantitative evaluation and discrimination of intracellular Cys/Hcy and GSH in complex biological environments is very important. In this study, probe CDS-NBD, synthesized by attaching 2,4-dinitrobenzenesulfonate (DNBS, site 1) and nitrobenzoxadiazole (NBD, site 2) as the highly sensitive and selective dual response site for thiols onto the coumarin derivative 7-hydroxycoumarin-4-acetic acid, exhibited large separation of the emission wavelengths, fast response, notable fluorescence enhancement, excellent sensitivity and selectivity to Cys/Hcy and GSH over other biological species. Additionally, CDS-NBD could make a distinction between two different fluorescent signals, GSH (an obvious blue fluorescence) and Cys/Hcy (a mixed blue-green fluorescence). Further study on imaging of Cys/Hcy and GSH in vivo by employing probe CDS-NBD could also be successfully achieved.

Simultaneous Discrimination of Cys/Hcy and GSH With Simple Fluorescent Probe Under a Single-Wavelength Excitation and its Application in Living Cells, Tumor Tissues, and Zebrafish

Owing to the important physiological sits of biothiols (Cys, Hcy, and GSH), developing accurate detection methods capable of qualitative and quantitative analysis of biothiols in living systems is needed for understanding the biological profile of biothiols. In this work, we have designed and synthesized a 4′-hydroxy-[1,1′-biphenyl]-4-carbonitrile modified with NBD group-based fluorescent probe, BPN-NBD, for sensitive detection of Cys/Hcy and GSH by dual emission signals via a single-wavelength excitation. BPN-NBD exhibited an obvious blue fluorescence (λmaxem = 475 nm) upon the treatment with GSH and reacted with Cys/Hcy to give a mixed blue-green fluorescence (λmaxem = 475 and 545 nm). Meanwhile, BPN-NDB performed sufficient selectivity, rapid detection (150 s), high sensitivity (0.011 µM for Cys, 0.015 µM for Hcy, and 0.003 µM for GSH) and could work via a single-wavelength excitation to analytes and had the ability to image Cys/Hcy from GSH in living MCF-7 cells, tumor tissues, and zebrafish by exhibiting different fluorescence signals. Overall, this work provided a powerful tool for thiols visualization in biological and medical applications.

A novel quinoline-based fluorescent probe for real-time monitoring of Cys in glioma

The highly selective fluorescent probe ZS-C1 for imaging Cys in living cells and 3D tumor cell sphere.