Fluorescent probe for sensitive discrimination of GSH and Hcy/Cys with single-wavelength excitation in biological systems via different emission.

Biothiols (GSH, Hcy, Cys) are important active sulfur substances in biological systems and widely participate in various physiological processes. The three kinds of biothiols have similar chemical structures, including the sulfhydryl group (-SH) and an amino group (-NH2), so distinguishing two or more of them simultaneously is an important challenge. Herein, a nopinone-based fluorescent probe 3-(3-((4-nitrobenzoxadiazole vinyl) nopinyl difluoride (NF-NBD) was designed to distinguish GSH and Hcy/Cys by generating different fluorescence channels with a single excitation wavelength. The nitrobenzodioxazole (NBD) was introduced in the fluorescent probe by ether bounds that can quench fluorescence and selectively discriminate GSH and Hcy/Cys. After reacting with GSH and Hcy/Cys, NF-NBD exhibited strong fluorescence (green for GSH and yellow for Hcy/Cys). NF-NBD displayed a wide linear range, low detection limit, a rapid response time, and superior selectivity for biothiols. Furthermore, NF-NBD was applied to image and distinguish different biothiols in living cells and zebrafish via different fluorescence signals at a single excitation wavelength.

A new ratiometric AIE fluorescent probe for detecting cysteine in food samples and imaging in the biological system.

l-Cysteine (Cys) plays a vital part in the food industry and biological processes. Herein, a novel ratiometric fluorescent probe NFA with aggregation-induced emission (AIE) property was developed to discriminate Cys from Hcy and GSH. The probe showed a ratiometric fluorescence response to Cys with the emission wavelength shifted from 450 nm to 495 nm. Probe NFA possessed good advantages in the detection of Cys including wide linear range (0-100 µM), low detection limit (0.21 µM), and rapid response time (within 2 min). Compared with previous reports, this is the first ratiometric probe that achieves the quantitative detection of Cys in different food samples in real-time (cabbage, bamboo shoots, lotus root, garlic, apple, pear, milk powder, and liquid milk). Moreover, NFA is successfully applied for ratiometric image endogenous and exogenous Cys in HeLa cells and zebrafish which demonstrated its practical biological application.

A novel AIE-active camphor-based fluorescent probe for simultaneous detection of Al3+ and Zn2+ at dual channels in living cells and zebrafish.

A novel dual-functional probe N'-(2-hydroxy-5-((4,7,7-trimethyl-3-oxobicyclo[2.2.1] heptan-2-ylidene)methyl) benzylidene)picolinohydrazide (PSH) was constructed from natural camphor. This probe showed strong yellow-green fluorescence at 535 nm due to its aggregation-induced emission (AIE) feature. Interestingly, the probe PSH displayed a significant turn-on fluorescence response towards Al3+ (green fluorescence at 500 nm) and Zn2+ (orange fluorescence at 555 nm) at two different emissive channels. The detection limits of PSH towards Al3+ and Zn2+ were found to be 12.1 nM and 14.2 nM, respectively. PSH exhibited excellent selectivity and anti-interference performance and could distinguish between Al3+/Zn2+ and identify whether Zn2+ exists in the PSH-Al3+ complex by adding ATP. The binding mechanisms between PSH and Al3+/Zn2+ ions were supported by 1H NMR, HRMS analysis, and density functional theory (DFT) calculations. Based on its outstanding sensing properties, the probe PSH was used to establish molecular logic function gates. Moreover, the probe PSH could be applied to detect Al3+ and Zn2+ in real environmental water, and fluorescence detection was well demonstrated by test strips. Furthermore, the probe PSH was employed for imaging Al3+ and Zn2+ in HeLa cells and zebrafish.