A ratiometric fluorescent probe with a large Stokes shift for the detection of Hg2+ and its applications in environmental sample and living system analysis.

Toxic mercury ions (Hg2+) can cause serious environmental pollution and accumulate in living organisms via the food chain. Therefore, monitoring Hg2+ is crucial in ensuring the safety of ecosystems and organisms. In this work, a novel ratiometric fluorescent probe CMT (5-(4-(diphenylamino)phenyl)-1-(7-hydroxy-coumarin-3-yl)-4-pentene-1,3-dione) based on coumarin was developed for detecting Hg2+, which displayed obvious fluorescence changes, a low detection limit (2.24 × 10-7 M), good selectivity, and a large Stokes shift (255 nm). The CMT probe could detect Hg2+ in real environmental soil and water samples. Furthermore, the CMT probe enabled the naked-eye detection of Hg2+ using test paper experiments. CMT was also applied for fluorescence imaging in living zebrafish and plants. This work provides a highly efficient tool for monitoring Hg2+ in environmental samples and biological systems.

An ultrasensitive cellulose-based fluorescent sensor for Al3+ detection and its applications in plant tissue and food samples.

Fluorescent sensors available for metal ions detection have been extensively developed in recent years. However, developing an ultrasensitive fluorescent sensor for highly selectively detecting Al3+ based on cellulose remains a challenge. In this study, an ethylcellulose-based flavonol fluorescent sensor named EC-BHA was synthesized by the esterification of ethylcellulose (EC) with a new flavonol derivative 4-(2-(2,3-bis(ethoxymeothy)phenyl)-3-hydroxy-4-oxo-4-H-chromen-7-yl) benzoic acid (BHA). The fluorescence intensity of EC-BHA exhibited a 180-fold increase at 490 nm after binding with Al3+ and provided an ultralow detection limit of 13.0 nM. The sensor showed some exceptional sensing properties including a broad pH range (4-10), large Stokes shifts (190 nm), and a short response time (3 min). This sensor was successfully applied for determining trace Al3+ in food samples as well as in plant tissue. Moreover, the electrostatic spun film EBP was fabricated by blending EC-BHA with PS (polystyrene) via electrostatic spinning technique and utilized for selective detection of Al3+ as soon as possible.

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.

An efficient chitosan-naphthalimide fluorescent probe for simultaneous detection and adsorption of Hg2+ and its application in seafood, water and soil environments.

As a virulent heavy metal ion, Hg2+ will lead to a serious threat to ecosystem and human health. In this work, we reported a chitosan-naphthalimide fluorescent probe CS-NA-ITC for specific recognition and efficient adsorption of Hg2+. CS-NA-ITC showed no fluorescence in solution state, while the fluorescence intensity increased obviously at the presence of Hg2+, accompanied by the fluorescence color becomes from colorless to bright yellow. It displayed favorable properties like low detection limit (73 nM), extensive pH detection range (5-10) and excellent anti-interference ability. The binding pattern of CS-NA-ITC to Hg2+ was verified by Job's plot, XPS analysis and FT-IR test. In addition, CS-NA-ITC was utilized to recognition of Hg2+ in actual water and soil samples and seafood products. Furthermore, the CS-NA-ITC hydrogel could be employed as an efficient Hg2+ adsorbent with good reusability, which adsorption ability was enhanced compared to chitosan hydrogel.

A naphthalimide functionalized chitosan-based fluorescent probe for specific detection and efficient adsorption of Cu2.

As one of the most abundant metal ions, Cu2+ has turned into a great threat to human health and the natural environment due to its widely utilized in various industries. In this paper, a chitosan-based fluorescent probe CTS-NA-HY for detection and adsorption of Cu2+ was rationally prepared. CTS-NA-HY exhibited a specific "turn off" fluorescence response to Cu2+ and the fluorescence color changed from bright yellow to colorless. It possessed satisfactory detection performance to Cu2+ including good selectivity and anti-interference, low detection limit (29 nM) and wide pH range (4-9). The detection mechanism was confirmed by Job's plot, X-ray photoelectron spectroscopy, FT-IR and 1H NMR analysis. Additionally, the probe CTS-NA-HY was capacity of determining Cu2+ in environmental water and soil samples. Besides, CTS-NA-HY-based hydrogel could also remove Cu2+ in aqueous solution effectively, which the ability of adsorption was greatly improved compared with original chitosan hydrogel.

A NIR BODIPY-based ratiometric fluorescent probe for HClO detection with high selectivity and sensitivity in real water samples and living zebrafish.

Hypochlorous acid (HClO) plays an important role in many physiological and pathological activities. In this work, a novel BODIPY-based Near-infrared (NIR) ratiometric fluorescent probe BODIPY-Hyp was designed for the rapid detection of HClO. The probe BODIPY-Hyp was highly selective and sensitive for HClO with a low detection limit of 16.74 nM and short response time of less than 60 s. The probe BODIPY-Hyp in response to HClO exhibited a significant blue-shifted fluorescence emission from 700 nm to 530 nm, and its fluorescence intensity ratio (I530 nm/I700 nm) increased about 1200 times before and after adding HClO. Moreover, the reaction mechanism of BODIPY-Hyp with HClO was verified by HRMS analysis, 1H NMR titration and DFT calculations. Furthermore, BODIPY-Hyp was successfully processed into a portable test strip-based device for the detection of HClO. In addition, the probe BODIPY-Hyp could be used in real time to monitor the levels of HClO in living zebrafish larvae. In conclusion, BODIPY-Hyp has great application potential in the life and environmental sciences.

Novel 2-Benzo[d]thiazolyl-4-quinolinylphenol Skeleton-Based Turn-on Fluorescent Probe for H2S Detection and its Multiple Applications in Water Environment, Foodstuffs, and Living Organisms.

Hydrogen sulfide (H2S) has comprehensive contributions to maintaining the normal operation and stability of organisms, and it also occurs in the wastewater environment and is related to the deterioration of foodstuffs. Therefore, developing high-sensitive detection techniques for tracing H2S is promising and meaningful. Inspired by this, a novel nopinone-based fluorescent probe NPS for the recognition of H2S was designed and synthesized with excellent sensitivity, low limit of detection (79 nM), good selectivity, and wide pH range (5-9). NPS could emit strong yellow fluorescence and its emission intensity showed a remarkable augmentation at 520 nm upon the supplement of H2S. Furthermore, the recognition mechanism of NPS for H2S was verified by the HRMS analysis, 1H NMR spectra titration, and DFT computation. What is more, NPS also had broad applications in the monitoring of real water samples, red wine, beer, and eggs samples, which showed its development prospect and value in environmental pollution, foodstuffs quality analysis fields. NPS also was applied to monitor trace exogenous H2S and bioimaging in living cells and zebrafish.

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.

Rational design of a facile camphor-based fluorescence turn-on probe for real-time tracking of hypochlorous acid in vivo and in vitro.

A simple yet highly effective camphor-derived fluorescent probe named 3-(anthracen-9-ylmethylene)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one oxime (ATHO) was developed based on an oxime recognition receptor and anthracene fluorophore. The probe ATHO exhibited a remarkably enhanced fluorescence response to HClO (∼7.2 fold). Meanwhile, this probe exhibited a low detection limit (0.118 µM), ultrafast response time (within seconds), excellent photostability (>260 min), wide linear range (0-180 µM), low probe concentration (2 µM), and high selectivity toward HClO over various interfering species. The sensing mechanism of the probe ATHO for HClO was supported by HRMS analysis and theoretical calculations. Furthermore, the probe ATHO was utilized to quantitatively determine HClO levels in environmental water samples. Additionally, the biological imaging of the probe ATHO for exogenous and endogenous HClO was successfully demonstrated in vitro and in vivo.

Novel Bis-Camphor-Derived Colorimetric and Fluorescent Probe for Rapid and Visual Detection of Cysteine and Its Versatile Applications in Food Analysis and Biological Imaging.

A new colorimetric and fluorescent turn-on probe named 2,4-bis(camphor-3-methylene)phenylacrylate (BCP-Cys) was designed for highly sensitive and specific monitoring of cysteine (Cys). The probe BCP-Cys was strategically constructed by employing a new bis-camphor-derived scaffold (BCP-OH) as the fluorophore and an acrylate group as the recognition site and fluorescence quencher. The acrylate group of BCP-Cys could be exclusively cleaved by Cys and release the fluorophore BCP-OH, thereby causing a significantly enhanced red fluorescence and a naked-eye colorimetric change from colorless to yellow. The probe BCP-Cys exhibited promising sensing performances for Cys including large Stokes shift (184 nm), fast response time (<1 min), wide linear range (0-100 nM), and low detection limit (0.0728 µM). Moreover, the probe BCP-Cys could be utilized as a powerful tool for real-time determination of Cys levels within different food samples, such as onion, cabbage, broccoli, garlic, cauliflower, and bamboo sprout. In addition, this probe was also capable of imaging endogenous and exogenous Cys in living cells.

A Novel Schiff Base-Modified Dialdehyde Cellulose-Based Fluorescent Probe for Al3+ and Its Application in Environmental Analysis.

Cellulose is the most abundant natural polymer with good biodegradability and biocompatibility. In this paper, a novel fluorescent probe DAC-SD-NA for aluminum (Al3+ ) detection is successfully synthesized based on dialdehyde cellulose (DAC). DAC-SD-NA exhibited a remarkable "turn-on" fluorescence response to Al3+ in a wide pH range, and the fluorescence color of DAC-SD-NA solution turned from colorless to bright blue at the presence of Al3+ . The detection limit for Al3+ is computed to be 6.06×10-7 m. The reaction mechanism of DAC-SD-NA towards Al3+ is confirmed by Job's plot, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations. In view of DAC-SD-NA exhibited good sensitivity and selectivity, it is applied to detect Al3+ in real water. What's more, DAC-SD-NA-loaded fluorescent hydrogel can serve as a convenient tool for the detection of Al3+ .

A highly effective "turn-on" camphor-based fluorescent probe for rapid and sensitive detection and its biological imaging of Fe2.

In this work, a novel fluorescent probe CBO was synthesized for detecting Fe2+ using the natural monoterpenketone camphor as the starting material. The probe CBO displayed turn-on fluorescence to Fe2+ accompanied by the solution change from colorless to green. As expected, there was an excellent linear relationship between the fluorescence intensity of probe CBO and the concentration of Fe2+ (0-20 µM), and the detection limit was as low as 1.56×10-8 M. In particular, CBO could selectively sense Fe2+ more than other analytes (Fe3+ included) through the N-oxide strategy, and quickly responded to Fe2+ (60 s) over a wide pH (4-14) range. Additionally, based on the rapid fluorescence response of CBO to Fe2+, a simple test strip-based detector was designed for boosting practical applicability. The probe CBO had been successfully applied to the fluorescence imaging of Fe2+ in onion cells and living zebrafish. The probe CBO was a powerful tool of detecting Fe2+ level in organisms, which was of significance to understand the role of Fe2+ in Fe2+-related physical processes and diseases.