A dual-reaction sites fluorescent probe for accurate detection of benzoyl peroxide in food

Benzoyl peroxide (BPO) is widely used as a whitening agent in flour, but excessive intake of BPO will severely endanger human health. To quickly and accurately detect BPO on-site, we have rationally designed a novel fluorescent probe PTPY-BE with dual-reaction sites. PTPY-BE underwent a specific cascade reaction with BPO to achieve high-contrast fluorescence turn-on response along with significant achromic reaction. The probe has high sensitivity, excellent selectivity, strong anti-interference ability and low detection limit (LOD = 0.83 mg·kg-1) for BPO. Furthermore, a portable detection platform was fabricated, which offers the portability and color visualization of traditional test strips and the color recognition of a smart device, enabling on-site visualization and quantitative detection of BPO. This platform has been successfully used to determine BPO in real food samples with good recoveries (93.59% - 107.13%). Therefore, this platform possessed great prospect and potential application for the determination of BPO in food.

Innovative indenone-derivative colorimetric fluorescent probe: A approach for copper ion detection in water

Copper (Cu2+) is a metal chemical element closely related to human life and is widely used in many fields. However, with the discharge of copper wastewater, the water quality will be seriously affected, leading to excessive intake of Cu2+ and a variety of diseases. Hence, there is a pressing need for an effective detection method for Cu2+ in aqueous environments. Leveraging the remarkable attributes of GFP chromophores and indenone derivatives, we have created a novel colorimetric fluorescent probe P-Cu2+, tailored for efficient copper ion detection. The addition of Cu2+ causes the solution to visibly change from colorless to a pronounced yellow, enabling naked-eye detection and offering promise for real sample analysis.

Evaluation of a novel pyridinium cation-linked styryl-based boronate probe for the detection of selected inflammation-related oxidants

Reactive oxygen and nitrogen species (RONS) are a range of chemical individuals produced by living cells that contribute to the proper functioning of organisms. Cells under oxidative and nitrative stress show excessive production of RONS (including hydrogen peroxide, H2O2, hypochlorous acid, HOCl, and peroxynitrite, ONOO-) which may result in a damage proteins, lipids, and genetic material. Thus, the development of probes for in vivo detection of such oxidants is an active area of research, focusing on molecular redox sensors, including boronate-caged fluorophores. Here, we report a boronate-based styryl probe with a cationic pyridinium moiety (BANEP+) for the fluorescent detection of selected biological oxidants in vitro and in vivo. We compare the chemical reactivity of the BANEP+ probe toward H2O2, HOCl, and ONOO- and examine the influence of the major intracellular non-enzymatic antioxidant molecule, glutathione (GSH). We demonstrate that, at the physiologically relevant GSH concentration, the BANEP+ probe is efficiently oxidized by peroxynitrite, forming its phenolic derivative HNEP+. GSH does not affect the fluorescence properties of the BANEP+ and HNEP+ dyes. Finally, we report the identification of a novel type of molecular marker, with the boronate moiety replaced by the iodine atom, formed from the probe in the presence of HOCl and iodide anion. We conclude that the reported chemical reactivity and structural features of the BANEP+ probe may be a basis for the development of new red fluorescent probes for in vitro and in vivo detection of ONOO-.

3A novel carbazole-based AIE-active fluorescent sensor for fast and ultrasensitive detection of Cu2+ and Co2+ in normal saline system

A novel phenyl-carbazole-based fluorescent sensor (PCBP) has been synthesized and investigated to selectively detect Cu²⁺ or Co²⁺. The PCBP molecule exhibits the excellent fluorescent property with the aggregation-induced emission (AIE) effect. In given THF/normal saline (f_w = 95%) system, the PCBP sensor shows turn-off fluorescence performance at 462 nm with Cu²⁺ or Co²⁺. It reveals excellent characteristics of good selectivity, and ultra-high sensitivity, strong anti-interference ability, wide pH applicable range, as well as ultra-fast detection response. The limit of detection (LOD) of the sensor reaches 1.1 × 10^-9 mol·L^-1 and 1.1 × 10^-8 mol·L^-1 for Cu²⁺ and Co²⁺ in turn. The formation mechanism of AIE fluorescence of PCBP molecules is attributed to the synergistic effect of intramolecular & intermolecular charge transfer (I&ICT). Meanwhile, the PCBP sensor has good repeatability for the detection of Cu²⁺, and performs excellent stability and sensitivity for the detection of Cu²⁺ in real water sample. The PCBP-based fluorescent test strips present reliable capacity for the detection of Cu²⁺ and Co²⁺⁺ in aqueous solution.

Development in Fluorescent OFF-ON Probes Based on Cu2+ Promoted Hydrolysis Reaction of the Picolinate Moiety

Anions and cations have a key role in our normal life. Cu²⁺ ion is a crucial trace element accountable for the part of several cellular enzymes and proteins, including cytochrome c oxidase, dopamine monooxygenase, Cu/Zn superoxide dismutase, and ceruloplasmin. WHO has found the extreme acceptable level of Cu²⁺ ions in drinking water is up to 2.0 ppm. Excess use of Cu²⁺ ions is associated with various human genetic disorders. Thus, the visualization of Cu²⁺ ions to avoid its toxic effects in chemical and biological systems is significant. In this review we have summarized sensors based on catalytic hydrolysis of picolinate to detect Cu²⁺ ions. The sensors based on hydrolysis of picolinate are very selective as compared to the other sensors for Cu²⁺ ions detection. We have focused on describing the structure, spectral properties, detection limits, and bioimaging model of the sensors.

Development of a method for the detection of Cu2+ in the environment and live cells using a synthesized spider web-like fluorescent probe

A macrocyclic Schiff base fluorescent probe [1,2-phenylenediamine-2,6-pyridinedialdehyde macrocyclic Schiff base] (BP-MSB) based on 2,6-pyridinedialdehyde was synthesized for use in the detection of Cu²⁺ in environmental water samples and live cells imaging by the method of specific recognition. The free fluorescent probe BP-MSB shows strong fluorescence in DMSO/H₂O. The probe shows high sensitivity and selectivity for Cu²⁺ through "turn-off" fluorescence response in DMSO/H₂O buffer solution (pH = 6.5), with a detection limit of 0.83 nM, which is far below the maximum allowable drinking water content of 20.0 μM specified by the US Environmental Protection Agency. The BP-MSB fluorescence quenching method was used for the determination of Cu²⁺ in Xiang Jiang water samples and tap-water. Furthermore, addition of the same number of moles of ethylene diamine tetraacetic acid (EDTA) can realize the reversible recognition of Cu²⁺ by the probe BP-MSB. Most importantly, the fluorescence imaging of live cells after incubation of BP-MSB with GM12878 cells showed good imaging performance, confirming the sensitivity of the fluorescent probe BP-MSB in vivo. The probe was also used to form an analog logic gate. This probe has the advantages of good stability, simple operation and high selectivity, which provides a broad prospect for environmental monitoring, intracellular detection and practical application of POCT.

A novel highly sensitive dual-channel chemical sensor for sequential recognition of Cu2+ and CN− in aqueous media and its bioimaging applications in living cells

A simple and unique dual-channel chemical probe (DH) was designed and synthesized, which not only realized sequential recognition of Cu2+ and CN− by colorimetric and fluorometric methods, but also realized fluorescence detection of CN−.

Fluorescent Carbon Quantum Dots-Synthesis,Functionalization and Sensing Application in FoodAnalysis

Carbon quantum dots (CQDs) with stable physicochemical properties are one of theemerging carbon nanomaterials that have been studied in recent years. In addition to the excellentoptical properties such as photoluminescence, photobleaching resistance and light stability, thismaterial also has favorable advantages of good biocompatibility and easy functionalization, whichmake it an ideal raw material for constructing sensing equipment. In addition, CQDs can combinedwith other kinds of materials to form the nanostructured composites with unique properties, whichprovides new insights and ideas for the research of many fields. In the field of food analysis,emerging CQDs have been deeply studied in food composition analysis, detection and monitoringtrace harmful substances and made remarkable research progress. This article introduces andcompares the various methods for CQDs preparation and reviews its related sensing applicationsas a new material in food components analysis and food safety inspection in recent years. It isexpected to provide a significant guidance for the further study of CQDs in the field of foodanalysis and detection. CQDs; synthesis; fluorescent sensing; food analysis.

A 4,5-quinolimide-based fluorescent sensor for sequential detection of Cu2+ and cysteine in water and living cells with application in a memorized device

In this study, a new 4,5-quinolimide-based fluorescent sensor BNC was synthesized and characterized. BNC showed single selectivity for Cu²⁺via the "turn-off" fluorescence among various common metal ions. After forming a 1:1 stoichiometric complex with Cu²⁺, the detection limit (LOD) of BNC for Cu²⁺ was measured to be 0.44 μM. Subsequently, the in situ generated BNC-Cu²⁺ complex had been used for sensing Cys with the LOD of 1.5 μM through the displacement strategy, resulting in the revivable emission of BNC. According to the "off-on-off" fluorescence cycle of BNC generated by the alternate addition of Cu²⁺ and Cys, a reversible memorized device with "read-write-read-erase" behavior was constructed at the molecular level. Furthermore, the recoveries of Cu²⁺ in lake water with BNC were in the range of 95.0-105%. And sequential fluorescence imagings of BNC for Cu²⁺ and Cys were successfully applied in living yeast cells.

A Near-infrared Fluorescent Probe of Dicyanoisophorone Derivatives for Selective Detection and Fluorescence Cellular Imaging of Palladium

Palladium (Pd) has been acknowledged to be a rare inner transition metal, which plays a pivotal role in many fields. This article focuses on developing a safe and effective near-infrared fluorescent probe, MW-PD, which would make a great contribution to the detection of palladium residue in drugs, especially trace residues. The fluorescent probe was rationally designed by combining the dicyanoisophorone fluorophore with an allyloxycarbonyl group. Based on the Tsuji-Trost reaction, the probe exhibited high selectivity and sensitivity toward Pd (0) over other common metal ions with a low detection limit (8.0 nM). Moreover, MW-PD showed biocompatibility and was successfully applied to imaging Pd (0) in Hela cells.

A colorimetric fluorescent probe for rapid and specific detection of nitrite

The method of fluorescent probes has been an important technique for detection of nitrite (NO₂ ^- ). As an important inorganic salt, excessive nitrite would threaten humans and the environment. In this paper, a colorimetric fluorescent probe P-N (1,2-diaminoanthraquinone) with rapid response and high selectivity, which could detect NO₂ ^- by visual colour changes and fluorescence spectroscopy is presented. The probe P-N solution (pH 1) changed from pink to colourless with the addition of NO₂ ^- and fluorescence intensity at 639 nm clearly decreased. Good linear exists between fluorescence intensities and NO₂ ^- concentrations for the range 0-16 μM, and the detection limit was 54 nM (based on a 3σ/slope). Moreover, probe P-N could also detect NO₂ ^- in real water samples, and results were all satisfactory. Probe P-N shows great practical application value for detecting NO₂ ^- in the environment.

Diaminomaleonitrile-based Fluorophores as Highly Selective Sensing Platform for Cu2

A colorimetric and turn-on fluorescent chemodosimeter 1 based on diaminomaleonitrile was synthesized for Cu²⁺ detection. It showed high selectivity and sensitivity towards Cu²⁺ over the other tested metal ions. Probe 1 in acetonitrile exhibited a strong absorption band at 530 nm and weak fluorescence emission when excited at 480 nm, while the addition of Cu²⁺ could lead to a 30-nm blue shift of the absorption band and a remarkable fluorescence enhancement. Moreover, the detection limit of probe 1 for Cu²⁺ was calculated to be 28 nM. Quite different from the reported mechanism based on a metal-complexation induced fluorescence enhancement, the sensing mechanism was proved to be based on the Cu²⁺-promoted hydrolysis reaction, which was confirmed by ¹H NMR, ¹³C NMR and mass spectrum analysis. Studies on probe 2 were carried out to verify the universality of this sensing mechanism.

Simply Structured Conjugated Compounds with Cyanoacrylate or Acrylonitrile Groups for Sensing of p-Toluenethiol

Simply structured conjugated compounds with cyanoacrylate (CA 1 - 4) and acrylonitrile (AN 1 - 4) terminal groups were synthesized by a Knoevenagel condensation reaction in one step and investigated for their recognition properties to p-toluenethiol by UV-vis, fluorescence spectra, and FT-IR measurements. When p-toluenethiol was added to CA 1, the FT-IR spectra revealed a cleavage of alkene caused by the addition reaction between p-toluenethiol and CA 1. An increase in p-toluenethiol concentration, a blue-shifted absorption band, and a decrease in the fluorescence intensity of CA 1 were observed because of the decrease in its effective conjugated length. Therefore, the most simply structured CA 1 was found to be the most effective and the most sensitive chemical sensor for p-toluenethiol.

Design and characterization of a 2-(2′-hydroxyphenyl)benzimidazole-based Sr2+-selective fluorescent probe in organic and micellar solution systems

Fluorescence detection of Sr(ii) by Sr(ii)-selective fluorescent probe BIC and its complex formed in solution.

A Highly Selective and Sensitive Colorimetric Probe for Cu2+ Determination in Aqueous Media Based on Derivative of Tryptanthrin

A new colorimetric probe, based on tryptanthrin derivative (TR-A), has been successfully synthesized. The probe shows good selectivity and sensitivity for Cu²⁺ over 12 competing metal ions in a 10 mM Tris-HCl buffer solution (pH 5.5). A significant peak at 623nm appears in the UV-Vis absorption of TR-A-Cu²⁺, and a noteworthy color change is observed with the naked eye from aquamarine blue to light orange. The interaction of TR-A and Cu²⁺ are proven to form a 1:1 binding stoichiometry; this identifying is expected to be completed within 1 min. The probe with a limit of detection (16 nM, R² = 0.9934) shows excellent potential to determine Cu²⁺ in analysis systems.

Sensitivity limits of biosensors used for the detection of metals in drinking water

Even when present in very low concentrations, certain metal ions can have significant health impacts depending on their concentration when present in drinking water. In an effort to detect and identify trace amounts of such metals, environmental monitoring has created a demand for new and improved methods that have ever-increasing sensitivities and selectivity. This paper reviews the sensitivities of over 100 recently published biosensors using various analytical techniques such as fluorescence, voltammetry, inductively coupled plasma techniques, spectrophotometry and visual colorimetric detection that display selectivity for copper, cadmium, lead, mercury and/or aluminium in aqueous solutions.