A wireless fluorescent sensing device for on-site closed-loop detection of hydrazine levels in the environment

Given the extensive need for the detection of hydrazine (N2H4) in the biomedical and chemical-pharmaceutical sectors, there is a necessity to devise a fast, sensitive, specific, and portable technique for precisely quantifying hydrazine at environmental levels. In our work, an "OFF-ON" type fluorescent probe namely 2-(4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)isoindole-1,3-dione (NAP), which was inspired by the "Gabriel" reaction, was synthesized. The NAP fluorescent cellulose film successfully achieved the detection of hydrazine vapor with a LOD = 0.658 ppm. Compared to previous qualitative methods for detecting hydrazine, this study successfully achieved quantitative identification of hydrazine at low concentrations. In addition, a portable sensor device based on NAP cellulose film was successfully integrated, enabling ultra-sensitive, wireless, remote, and real-time detection of N2H4 vapor. It was determined that the probe (NAP) exhibited excellent detection performance when applied to various environmental samples including distilled water, tap water, creek water, soil and plants. This study introduces a potentially effective approach for detecting hydrazine in real-world settings.

A novel pathway for ratiometric hydrazine sensing in environmental samples and the detection of intracellular viscosity by a mitochondria-targeted fluorescent sensor

Mass and signal transfer, dispersion of reactive metabolites in living cells, and interactions between biomacromolecules are greatly affected by viscosity inside the cells. It is crucial to accurately determine viscosity for reliable results because of the complexities of live cells. Herein, we introduce a new fluorescence probe based on the cyanobiphenyl and benzothiazolium units. This probe not only responds to intracellular viscosity but also detects hydrazine, a widely used chemical that poses significant environmental and toxic risks to organisms. The proposed sensing mechanism provides a new pathway that includes intramolecular cyclization with hydrazine, which differs from other sensing mechanisms. A weak emission (at 590 nm) of the probe under excitation at 365 nm resulted in 25-fold higher emission at 488 nm after the addition of N2H4. The quantum yield of the probe (Φ = 0.089) increased to Φ = 0.199 with the addition of N2H4. In addition, the probe demonstrated 45-fold emission enhancement at 560 nm in viscous media, with a color change from non-fluorescence to yellow fluorescence. Good hydrazine sensing features with high adaptability, selectivity, sensitivity, ratiometric and fast response (90 s), low cytotoxicity (more than 90% of cell viability), low detection limit (86.0 nM), good linearity in the range of 0-35.0 μM, and high signal-to-noise ratio sensing capability were achieved. The hydrazine-sensing capability of the mitochondria-targetable probe in living cells makes it a strong candidate for various biological and environmental applications, including intracellular tracking and imaging. These results suggest that the present probe shows significant potential for the effective fluorescence detection of hydrazine.

A resorufin-based fluorescent probe for hydrazine detection and its application in environmental analysis and bioimaging

Hydrazine (N2H4) is an important industrial raw material that has been widely used in industrial production and agricultural interventions, but its widespread application also inevitably causes environmental pollution. In this study, based on resorufin, we constructed a novel "turn-on" fluorescent probe RFT for the selective detection of hydrazine under complex environmental conditions and in vivo. The probe RFT exhibited excellent stability and selectivity towards the detection of hydrazine with a low detection limit of 260 nM. In addition, RFT was successfully applied to the detection of hydrazine in environmental water samples and living cells. Most importantly, RFT could not only detect the exogenous hydrazine in zebrafish and mice, but also image and visualize the up-regulation of endogenous hydrazine induced by isoniazid in zebrafish.

A near-infrared ratiometric fluorescent probe for hydrazine and its application for gaseous sensing and cell imaging

Hydrazine (N₂H₄) is a widely used raw material in the chemical industry, but at the same time hydrazine has extremely high toxicity. Therefore, the development of efficient detection methods is crucial for monitoring hydrazine in the environment and evaluating the biological toxicity of hydrazine. This study reports a near-infrared ratiometric fluorescent probe (DCPBCl₂-Hz) for the detection of hydrazine by coupling a chlorine-substituted D-π-A fluorophore (DCPBCl₂) to the recognition group acetyl. Due to the halogen effect of chlorine substitution, the fluorophore has an elevated fluorescence efficiency and a lowered pKa value and is suitable for physiological pH conditions. Hydrazine can specifically react with the acetyl group of the fluorescent probe to release the fluorophore DCPBCl₂, so the fluorescence emission of the probe system significantly shifted from 490 nm to 660 nm. The fluorescent probe has many advantages, such as good selectivity, high sensitivity, large Stokes shift, and wide applicable pH range. The probe-loaded silica plates can realize convenient sensing gaseous hydrazine with content down to 1 ppm (mg/m³). Subsequently, DCPBCl₂-Hz was successfully applied to detect hydrazine in soils. In addition, the probe can also penetrate living cells and allow the visualization of intracellular hydrazine. It can be anticipated that probe DCPBCl₂-Hz will be a useful tool for sensing hydrazine in biological and environmental applications.

Two Ratiometric Fluorescent Probes Based on the Hydroxyl Coumarin Chalcone Unit with Large Fluorescent Peak Shift for the Detection of Hydrazine in Living Cells

Hydrazine is widely used in industrial and agricultural production, but excessive hydrazine possesses a serious threat to human health and environment. Here two new ratiometric fluorescence probes, DDP and DDC, with the hydroxyl coumarin chalcone unit as the sensing site are developed, which can achieve colorimetric and ratiometric recognition for hydrazine with good sensitivity, excellent selectivity, and anti-interference. The calculated fluorescence limits of detections are 0.26 μM (DDC) and 0.14 μM (DDP). The ratiometric fluorescence response to hydrazine is realized through the adjustment of donor and receptor units in coumarin conjugate structure terminals, accompanied by fluorescence peak shift about 200 nm (DDC, 188 nm; DDP, 229 nm). Stronger electropositivity in the carbon-carbon double bond is helpful to the first phase addition reaction between the probe and hydrazine. Higher phenol activity in the hydroxyl coumarin moiety will facilitate the following dihydro-pyrazole cyclization reaction. In addition, both of these probes realized the convenient detection of hydrazine vapor. The probes were also successfully applied to detect hydrazine in actual water samples, different soils, and living cells.

A dual-response fluorescent probe for N2H4 and viscosity in living cells and zebrafish to evaluate liver injury

Hydrazide drugs can cause severe drug-induced liver injury owing to the enzymatic release of N₂H₄ in the liver. Also, changes in cellular viscosity are associated with liver damage. Thus, simultaneous monitoring of changes in N₂H₄ levels and viscosity can be used to evaluate the side effects of hydrazide drugs. Herein, we firstly reported a near-infrared fluorescent probe (FNN), which contains 1,8-naphthalimide as the fluorophore and a chalcone moiety as the responsive receptor, for sensitively detecting intracellular viscosity and N₂H₄. FNN showed a fast 'turn-on' fluorescence response to N₂H₄ with excellent selectivity. Additionally, FNN could selectively track viscosity without interference from polarity, pH, and other active species. Furthermore, imaging experiments suggested that FNN could be successfully applied in living cells and zebrafish larvae and embryos, which is of great importance for effectively assessing the degree of liver injury.

Development of a ratiometric fluorescent probe with large Stokes shift and emission wavelength shift for real-time tracking of hydrazine and its multiple applications in environmental analysis and biological imaging

As a tremendously noxious and extensively utilized chemical reagent, hydrazine (N₂H₄) has become a serious threat to ecosystem and human health. Thus, it is desirable to exploit an efficient method for real-time tracking of hydrazine. Here, a novel ratiometric fluorescent probe PBQ-AB for hydrazine was rationally constructed from isolongifolanone. This probe displayed an extremely large Stokes shift of 230 nm and could selectively recognize hydrazine in the presence of other competitive species within an extremely short time ( 40 s). PBQ-AB also displayed some fascinating merits in the detection of hydrazine, including low detection limit (48 nM), wide pH range (5-12), excellent photostability (>240 min), and well-resolved emission wavelength shift (148 nm). Moreover, this probe was utilized to fabricate a ready-to-use electrospinning nanofibrous membrane for convenient detection of hydrazine vapor by virtue of smartphone. Furthermore, PBQ-AB was capable of determining hydrazine contaminant in environmental soil and water samples. Additionally, its favorable performance for detecting hydrazine was successfully demonstrated in live HeLa cells as well as in live Arabidopsis thaliana tissues, manifesting its promising application for labeling hydrazine in living systems. Therefore, we believed that this probe has great potential in environmental analysis and health supervision.

Sensing for hydrazine of a pyrene chalcone derivative with acryloyl terminal group

Hydrazine, as a toxic substance, seriously endangers human health and the environment. Based on the excellent luminescent properties and low biological toxicity of pyrene derivatives, combing with chalcone derivatives easily attacked by nucleophilic group, a pyrene derivative PCA decorated by acryloyl terminal group as fluorescent probe for hydrazine was developed. The compound shows fluorescent peak red shift and intensity enhancement with increasing solvent polarity from hexane (459 nm) to methanol (561 nm). Based on strong fluorescence emission in methanol, methanol-HEPES mixed solution was used as the solvent in the spectral recognition experiments. The probe exhibits fluorescent change from yellow fluorescence (576 nm) to blue fluorescence (393 nm) with 800-fold ratiometric fluorescence enhancement (I_393nm/I_576nm) after the reaction with hydrazine. The probe can recognize hydrazine in fast response rate with kinetic constant calculated being 2.7 × 10^-3 s^-1 and 15 min as response time. The probe also can monitor hydrazine in real water samples and various soils.

A benzocoumarin-based fluorescent probe for ultra-sensitive and fast detection of endogenous/exogenous hypochlorous acid and its applications

Hypochlorous acid (HOCl) is widely used in daily production and life because of its green and strongly oxidizing properties.

A bis-pyrene chalcone based fluorescent material for ratiometric sensing of hydrazine: An acid/base molecular switch and solid-state emitter

In this work, we have designed and synthesized a new fluorescent molecular probe, DPY comprising of pyrene-diacetylpyridine conjugate, which was found to be sensitive to hydrazine as well as protonation. DPY is characterised by a strong emission both in solution (λ_em = 530 nm) as well as in solid state (λ_em = 610 nm), attributed to intramolecular charge-transfer. The probe responds to hydrazine with a ratiometric fluorescence emission change from yellow to blue, due to chalcone cyclisation reaction of α, β-unsaturated carbonyl group resulting in the pyrazoline compound, DPY-Hy, imparting a strong greenish-blue emission in solution. Further, the strong fluorescence emission of DPY in powder and thin film was quenched upon exposure to TFA, and revived upon exposure to TEA. For developing on-site detection protocol, when DPY was drop-casted on nonfluorescent silica plate a vivid naked-eye colour change from orange-red to dark blue was realized. Interestingly, in the aggregated state, DPY exhibited a broad range emission from green to orange in a mixed solvent system of THF:H₂O. A plausible explanation of the photophysical events is substantiated with theoretical calculations.

Intraperitoneal Injection of Cyanine-Based Nanomicelles for Enhanced Near-Infrared Fluorescence Imaging and Surgical Navigation in Abdominal Tumors

Fluorescent surgical navigation can effectively aid tumor resection. As one of the most popular near-infrared (NIR) fluorophores, cyanine dye has the outstanding optical ability and the potential to act as a fluorescence probe for tumors. Herein, we report a polyethylene glycol-modified amphiphilic cyanine dye (Cy7-NPC) with an NIR luminescence performance, which can self-assemble to form uniform nanomicelles (Cy7-NPC-S) and which can be applied for the optical imaging of abdominal tumors and for fluorescence imaging-guided precision tumor resection. When applied to biological imaging, Cy7-NPC-S showed high biological safety, strong tissue penetration depth for optical imaging, and high optical imaging resolution. Intraperitoneal administration of Cy7-NPC-S produced remarkable imaging efficacy in abdominal tumors. Compared with intravenous injection, abdominal tumors took up intraperitoneal Cy7-NPC-S faster and in greater quantities, thus enabling Cy7-NPC-S to facilitate accurate recognition and extirpation of abdominal tumors in fluorescence-guided surgery. We believe that metabolizable Cy7-NPC-S with NIR luminescence has promising applications and value in the fields of in vivo imaging and fluorescent surgical navigation.

A novel coumarin-based colorimetric and fluorescent probe for detecting increasing concentrations of Hg2+ in vitro and in vivo

Mercury has complex biological toxicity and can cause a variety of physiological diseases and even death, so it is of great importance to develop novel strategies for detecting trace mercury in environmental and biological samples. In this work, we designed a new coumarin-based colorimetric and fluorescent probe CNS, which could be obtained from inexpensive starting materials with high overall yield in three steps. Probe CNS could selectively respond to Hg²⁺ with obvious color and fluorescence changes, and the presence of other metal ions had no effect on the fluorescence changes. Probe CNS also exhibited high sensitivity against Hg²⁺, with a detection limit as low as 2.78 × 10^-8 M. More importantly, the behavioral tracks of zebrafish had no obvious changes upon treatment with 10 μM probe CNS, thus indicating its low toxicity. The probe showed potential application value and was successfully used for detecting Hg²⁺ in a test strip, HeLa cells and living zebrafish larvae.

Comparing the abundance of HClO in cancer/normal cells and visualizing in vivo using a mitochondria-targeted ultra-fast fluorescent probe

Organisms are operating and evolving with a highly sophisticated and intelligent defense mechanism to resist bacterial and viral infections. This process involves a variety of reactive oxygen species (ROS), and they coordinate with each other to support different physiological activities. Due to its strong oxidizing properties, hypochlorous acid (HClO), a part of ROS, is a powerful antimicrobial agent in living organisms and exerts a crucial role in the immune system. However, the excessive production of HClO can cause cell damage and even cell death. Herein, we combined benzene-conjugated benzopyrylium as the fluorophore and dimethylthiocarbamoyl chloride as the recognition site to rationally design a probe (BBD). The fluorescence of the probe was quenched based on an effective PET molecular mechanism. Surprisingly, BBD exhibited a turn-on red fluorescence signal for HClO with ultra-fast response (5 s) and high selectivity. Moreover, BBD located mitochondria well and it was found that the abundance of HClO is higher in HeLa cells compared to that in normal cells. Finally, BBD was successfully applied to the visualization of HClO in zebrafish and nude mice.

Diethyl Malonate-Based Turn-On Chemical Probe for Detecting Hydrazine and Its Bio-Imaging and Environmental Applications With Large Stokes Shift

Diethyl malonate-based fluorescent probe NE-N₂H₄ was constructed for monitoring hydrazine (N₂H₄). The novel probe NE-N₂H₄ exhibits good properties, such as large Stokes shift (about 125 nm), good selectivity, and low cytotoxicity. This sensing probe NE-N₂H₄ can be operated to detect hydrazine in living HeLa cells. Especially after soaking in probe solution, the thin-layer chromatography (TLC) plate could detect the vapor of hydrazine. Therefore, the probe NE-N₂H₄ might be used to monitor hydrazine in biosamples and environmental problem.

Development of chalcone-based derivatives for sensing applications

The sensing of various analytes including metal ions and anions is at an incredible speed due to their widespread use in biological processes. Various small molecular species have been reported for the detection of various analytes, with the advantage of low cost and high sensitivity. Among various classes of organic molecules, chalcones are suitable candidates for the design of new chemosensors for targeted ions. In this review, using extensive examples of chalcone-based chemosensors, we explore the design, mechanism, and performance of various chemosensors for the detection of different ions. We believe that this review will provide new insight for researchers in related areas to develop chemosensors for various targeted ions.

A practical pH-compatible fluorescent sensor for hydrazine in soil, water and living cells

The excellent water solubility of hydrazine (N₂H₄) allows it to easily invade the human body through the skin and respiratory tract, thereby damaging human organs and the central nervous system. To realize the monitoring of N₂H₄ effectively, first, coumarin was used to construct an inner alicyclic ring as the reaction site, extending the conjugation and strengthening the rigidity of the probe Co-Hy to improve its luminescence performance and enhance its ability to resist acids and alkalis. Second, we introduced a carboxyl group at the ortho position of the inner alicyclic ring to improve the water solubility of Co-Hy, and its strong electron pulling effect increased the activity of the reaction site. Spectroscopy experiments showed that Co-Hy featured excellent water solubility, high pH resistance (pH 4-11), excellent selectivity, fast analysis speed (within 5 minutes), and a low detection limit toward N₂H₄ (69 nM, 2.2 ppb). In addition, test-strip, spray, and cell-imaging experiments confirmed the outstanding application potential of Co-Hy for convenient N₂H₄ analysis in a variety of environments.

Additive- and column-free synthesis of rigid bis-coumarins as fluorescent dyes for G-quadruplex sensing via disaggregation-induced emission

A novel and efficient method to synthesize rigid bis-coumarins based on the dimerization of coumarinyl aldehydes was developed. This procedure is additive- and column-free, providing a facile and environment-friendly way to prepare fluorophores. The prepared novel fluorescent bis-coumarins exhibit favorable photophysical properties with good sensitivity and selectivity towards G-quadruplexes (G4s).

Zirconium doping level modulation combined with chalconylthiourea organic frameworks induced enhancement of luminescence applied to cell imaging

Derivatives of a zirconium metal–organic framework as the center polymer material with a chalconylthiourea polymer (CT) were applied to cell imaging.

Independent bi-reversible reactions and regulable FRET efficiency achieving real-time visualization of Cys metabolizing into SO2

An independent bi-reversible reaction sensor BPC detected cysteine (Cys) and sulfur dioxide (SO₂) based on the regulable FRET efficiency, and achieved real-time process visualization of Cys metabolizing into SO₂ in subcellular organelles and tumors.