A novel water-soluble flavonol-based fluorescent probe for highly specific and sensitive detection of Al3+ and its application in onion and zebrafish

A ratiometric fluorescent probe with a large Stokes shift for rapid and sensitive detection of Hg2+ in environmental water samples and its applications in living cells and zebrafish

Detection of highly toxic mercury ions (Hg2+) in actual environmental and biological samples is of significant importance for protecting environment and human health. In this paper, a new ratiometric fluorescent probe BTIA was designed and synthesized from 3-pinone based on Internal Charge Transfer (ICT) mechanism. BTIA could selectively recognize Hg2+ over other competitive analytes with short reaction time (5 s), distinct ratiometric response, strong anti-interference ability, large Stokes shift (200 nm), and low detection limit (2.36 × 10-7 M). Furthermore, BTIA was applicable for detecting Hg2+ in actual water samples and it also performed an excellent imaging capability in living RAW264.7 cells, zebrafish and onion tissue.

A highly effective curcumin-based fluorescent probe with single-wavelength excitation for simultaneous detection and bioimaging of Cys, Hcy and GSH

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) act as significant roles in many physiological processes, and their abnormal proliferation will cause multiple diseases including Alzheimer's disease, Parkinson's disease, Cardiovascular disease, atherosclerosis, and soft tissue damage. However, It is challenging work to develop a efficient method for differentiating and detecting GSH, Cys and Hcy because of their significant similarity in structures and functions. In this work, a smart fluorescent probe FBCN based on curcumin was rationally devised and developed by etherifying the phenol hydroxyl group on FBC with NBD-Cl, which emitted strong green at 516 nm. FBCN distinguished Hcy from Cys/GSH with naked eyes based on the color variation of probe solution in sunlight. Meanwhile, GSH induced the powerful fluorescence quenching of probe solution, but the fluorescence color of FBCN solution transformed from green to luminous yellow accompanied with emission wavelength redshifted from 516 nm to 540 nm or 553 nm in the existence of Hcy and Cys, respectively. Probe FBCN had outstanding sensitivity and anti-interference, low detection limit (56.5 nM, 77.7 nM, and 288 nM corresponded to Cys, Hcy, and GSH, respectively), short response time (the response time of FBCN to Cys, Hcy and GSH was 1 min, 2 min and 5 min, respectively). The DFT calculation and HRMS had verified the sensing mechanism of FBCN to biothiols. In addition, the probe was successfully utilized to detect three biothiols levels in living cell and zebrafish.

In-situ evaluation the fluctuation of hypochlorous acid in acute liver injury mice models with a mitochondria-targeted NIR ratiometric fluorescent probe

Acute liver injury (ALI) is a frequent and devastating liver disease that has been made more prevalent by the excessive use of chemicals, drugs, and alcohol in modern life. Hypochlorous acid (HClO), an important biomarker of oxidative stress originating mainly from the mitochondria, has been shown to be intimately connected to the development and course of ALI. Herein, a novel BODIPY-based NIR ratiometric fluorescent probe Mito-BS was constructed for the specific recognition of mitochondrial HClO. The probe Mito-BS can rapidly respond to HClO within 20 s with a ratiometric fluorescence response (from 680 nm to 645 nm), 24-fold fluorescence intensity ratio enhancement (I645/I680), a wide pH adaptation range (5-9) and the low detection limit (31 nM). The probe Mito-BS has been effectively applied to visualize endogenous and exogenous HClO fluctuations in living zebrafish and cells based on its low cytotoxicity and prominent mitochondria-targeting ability. Furthermore, the fluorescent probe Mito-BS makes it possible to achieve the non-invasive in-situ diagnosis of ALI through in mice, and provides a feasible strategy for early diagnosis and drug therapy of ALI and its complications.

Natural flavonols as probes for direct determination of borax: From conventional fluorescence analysis to paper-based smartphone sensing

Borax is strictly regulated in the food processing and pharmaceutical industry due to its physiological toxicity, and the development of a direct analytical method is essential for effectively monitoring the borax abuse. In this work, the fluorescence properties of flavonoids, including flavones, isoflavones and flavonols, were systematically investigated from aqueous to borax solutions, and it was found that the weak intrinsic fluorescence of flavonols could be pervasively sensitized by borax. A natural flavonol, morin, was subsequently chosen as a representative probe to develop a turn-on fluorescence sensing method for borax analysis, which achieved a linear response spanning four orders of magnitude with a detection limit of 1.07 μM (0.22 μg mL-1 in terms of Na2B4O7 content). Furthermore, a smartphone-assisted paper-based test device was designed and constructed by 3D printing technology. Using morin-impregnated test strips as the carrier, the borax could be visually detected by the RGB signals of the captured images, with a detection limit of 0.13 mM (27.05 μg mL-1 for Na2B4O7). Combining ion exchange treatment for food samples and sodium periodate oxidation for drug samples, the developed methods were successfully applied for the direct analysis of borax in various products with the recoveries of 86.9-106.3% for traditional fluorescence analysis and 82.7-108.8% for smartphone-assisted fluorescence sensing. The fluorescence property of the morin-borax system was studied using time-dependent density functional theory, and the sensing mechanism was discussed in conjunction with experimental research.

Portable paper-based probe for on-site ratiometric fluorescence determination of total flavonol glycosides in plant extract using smartphone imaging

A smartphone-assisted, paper-based ratio fluorescence probe is presented for the rapid, low-cost and on-site quantification of total flavonol glycosides in Ginkgo biloba extracts (GBE). The Al3+/Eu-MOF/paper-based probe utilizes lanthanide metal-organic framework (Ln-MOF) nanoparticles immobilized on Whatman filter paper along with Al3+ for detecting flavonols, which are the hydrolyzed products of flavonol glycosides. The color change of the paper-based fluorescence image from red to orange depends on the concentration of the target analyte in the sample solution. The smartphone equipped with a red, green, blue (RGB) color detector measured the fluorescence signal intensity on the paper substrate after adding flavonol. The analytical variables affecting the performance of the probe, including the addition sequence of the aluminum nitrate solution, its concentration, that of the Ln-MOF solution, the drying time of the paper probe, the reaction time and the sensitivity parameters of the mobile phone camera (ISO), were optimized. Under optimal conditions, the Al3+/Eu-MOF/paper-based probe has good linear response in the concentration range 7 ~ 80 µg mL- 1 and a lower detection limit of 2.07 µg mL- 1. The results obtained with the paper-based ratio fluorescence probe and smartphone combination were validated by comparing them with high-performance liquid chromatography (HPLC) measurements. This study provides a potential strategy for fabricating Al3+/Eu-MOF/paper-based probe used for total flavonol glycosides determination.

A simple 'turn-on' fluorescence chemosensor for Al(iii) detection in aqueous solution and solid matrix

A simple fluorescence chemosensor of FHS-OH based on salicylaldehyde Schiff base was developed via a one-step reaction, which achieved a fast and highly selective response for Al(iii). Mechanism studies showed that when FHS-OH was exposed to Al(iii) with 1 : 2 binding stoichiometry in an aqueous solution at neutral pH, C[double bond, length as m-dash]N isomerization and PET processes were limited, resulting in a 'turn-on' fluorescence response with a low detection limit of 63 nmol L-1 and a satisfying linear range of 0.0-20.0 μmol L-1. Compared to traditional detection methods for Al(iii), fluorometry using FHS-OH has several advantages, including simplicity, quick response, and capability of real-time detection. More importantly, the detection of Al(iii) on a solid matrix (test paper) was successfully achieved. After the addition of Al(iii), a significant emission colour change from green to bright blue was observed by the naked eye owing to the intrinsic aggregation-induced emission (AIE) characteristic of FHS-OH.

A highly specific chalcone derivative grafted ethylcellulose fluorescent probe for rapid and sensitive detection of Al3+ in actual environmental and food samples

Al3+ is commonly utilized in daily life, however, the excessive accumulation of Al3+ within organisms can result in severe health problems. Herein, a highly efficient fluorescent probe EC-HTC for Al3+ was synthesized through chemical modification of ethyl cellulose. This probe exhibited a significant fluorescence enhancement response to Al3+, and it interestingly also possessed an obvious aggregation-induced emission (AIE) effect. The detection limit of probe EC-HTC for Al3+ was as low as 0.23 μM, and its pH usage range was as wide as 5-10. The complexation ratio of EC-HTC with Al3+ was determined to be 1:1 based on Job's plot, which was further confirmed by 1H NMR titration and HRMS analysis. Moreover, the probe EC-HTC was successfully employed for the determination of Al3+ in environmental and food samples. In addition, the probe EC-HTC compositing PS (polystyrene) electrostatic spun fiber membranes EHP with high specific surface area were prepared to achieve the rapid and portable detection of Al3+.