Synthesis and application of highly sensitive fluorescent probe for Hg 2+ regulated by sulfur

A rhodamine NIR probe for naked eye detection of mercury ions and its application

Fluorescence imaging technology has developed rapidly with its advantages, and near-infrared probes are worthy of attention because of their less background interference, low light damage, and infinite potential. Rhodamine and its derivatives have the unique structure of lactam helices, which is an ideal platform for the construction of on-off fluorescent sensors. In this paper, a novel near-infrared fluorescent probe (RBLS) based on rhodamine derivatives was synthesized for the transient detection of mercury ions. The closed-on structure can realize reversible sensor recovery by adding S2-. The superior imaging capability in living cells and in vivo in zebrafish holds promise for biological applications. In addition, the naked eye test strips prepared with RBLS probes can be used to detect and screen Hg2+ in the environment and show good gradient change performance.

A fluorescent probe for bioimaging of GSH in cancer cells

A fluorescent probe CTP2-IMC was designed for bioimaging of glutathione (GSH) in cancer cells with indomethacin (IMC), coumarin and bromide as the targeting group, fluorophore and receptor, respectively. Due to the π-π interaction between coumarin and IMC, CTP2-IMC mainly exists in the form of folded state in aqueous solution. The non-radiative transitions caused by the photo-induced electron transfer (PET) process from IMC to the fluorophore as well as the heavy-atom effect led to non-fluorescent of CTP2-IMC. The substitution of Br by GSH and unfolded conformation induced by IMC acceptor on cancer cells resulted in significant fluorescence enhancement, which enabled CTP2-IMC to bioimage GSH in cancer cells rather than in normal one.

A Novel Rhodamine Probe Acting as Chemosensor for Selective Recognition of Cu2+ and Hg2+ Ions: An Experimental and First Principle Studies

Copper and Mercury ions have vital role to play in biological world as their excess or deficiency can cause different type of diseases in human being as well as biological species including plants and animals. Therefore, their detection at trace level becomes very important in term of biological. The current studies embody the fabrication, structural characterization and recognition behavior of a novel rhodamine B hydrazone formed when hydrazide of rhodamine B was condensed with 5-Allyl-3-methoxy salicylaldehyde (RBMA). RBMA was found to be responsive towards the very trace level of Cu2+ and Hg2+ among other tested cations so far. The sensing procedure is based on the classical opening of the spiroatom ring of rhodamine. The limit of detection (LOD) and binding constant is 5.35 ppm, 2.06 × 104 M-1 and 5.16 ppm, 1.26 × 104 M-1 for Cu2+ and Hg2+ ions respectively. The probable mechanism correlates the specific binding of RBMA with Cu2+ and Hg2+ ions. The 1:1 stoichiometry of RBMA with Cu2+ and Hg2+ ions have been supported by HRMS, FT-IR data, Job's plot, and binding constant data. Reversibility is well exhibited by RBMA by the involvement of CO32- ions via demetallation process. The real time application is well demonstrated by the use of paper strip test. The DFT study also carried out which agrees well with the experimental findings. The results displayed the novelty of this current work towards the trace level analysis of the Cu2+ and Hg2+ of the cations which are play the crucial role in industry.

A naphthalimide functionalized fluoran with AIE effect for ratiometric sensing Hg2+ and cell imaging application

The pollution caused by mercury ions (Hg²⁺) poses a potential threat to public health. Therefore, monitoring Hg²⁺ concentration in the environment is necessary and significant. In this work, a naphthalimide functionalized fluoran dye NAF has been prepared, which shows a new red-shift in emission at 550 nm with the maximum intensity in a mixture of water-CH₃CN (v/v = 7/3) due to aggregating induced emission (AIE) effect. Meanwhile, NAF can be employed as a Hg²⁺ ions sensor, which displays a selective and sensitive response to Hg²⁺ ions by the reduced fluorescence of naphthalimide fluorophore and increased fluorescence of fluoran group, respectively, showing ratiometric fluorescence signal changes with more than 65-fold emission intensity ratio increase and naked eyes visible color change. In addition, the response time is fast (within 1 min) and the sensing can be conducted in a wide pH range (4.0-9.0). Moreover, the detection limit has been evaluated to be 5.5 nM. The sensing mechanism may be attributed to the formation of a π-extended conjugated system due to the Hg²⁺ ions-induced conversion of spironolactone to the ring-opened form, partially accompanied by the fluorescence resonance energy transfer (FRET) process. Significantly, NAF exhibits suitable cytotoxicity to living HeLa cells, which allows it to be utilized for ratiometric imaging of Hg²⁺ ions assisted by confocal fluorescence imaging.

Highly selective fluorescent probe for detecting mercury ions in water

Mercury ion (Hg²⁺) is a well-known toxic heavy metal. It has become one of the most significant environmental pollutants in the world because of its serious physiological toxicity, persistence, easy migration, and high bioconcentration. Thus, the development of methods for monitoring Hg²⁺ is indispensable. Herein, we have designed and synthesized a new fluorescent probe, TPH, for the detection of Hg²⁺ in the water environment. The TPH probe could quantitatively detect Hg²⁺ between 0 and 5 μM (LOD = 16 nM), with a linear range of 0-2.5 μM. In addition, the TPH probe was used to monitor Hg²⁺ in water samples successfully. Thus, this probe is suitable for monitoring Hg²⁺ in the actual water environment.

Colorimetric detection of mercury (Hg2+) using UV-vis spectroscopy and digital image analysis based on gold nanoparticles functionalized with bromelain enzyme

A very sensitive and selective colorimetric biosensor for the measurement of mercury ion (Hg2+) in environmental samples has been developed using functionalized gold nanoparticles with bromelain enzyme (brn-AuNPs). This work has shown that Hg2+ measurement based on spectrophotometer and digital image analysis is a very innovative and successful method for providing an effective preliminary system and has promise for the future of water quality biomonitoring. Response Surface Methodology (RSM), a Box-Behnken design-based technique, was used to identify the optimum levels of functionalization of bromelain to AuNPs. The created model's validity was confirmed, and statistical analysis revealed that the ideal functionalize conditions were 1 mM of AuNPs, functionalize with 0.59 mM bromelain concentration on 14 ℃ temperature and 72 h incubation time. The lowest colorimetric detection concentration (LOD) of brn-AuNPs of Hg2+ was 0.0092 ppm and 0.011 ppm for spectrophotometer and digital image analysis. As shown, digital image analysis had advantages based on the LOD result comparable to UV-VIS spectrophotometer. The practical application of the brn-AuNPs sensing was proven with mercury determination in water samples. The present study developed a robust sensor, which successfully implemented in a compact portable sensor kit, turning this sensor into a very potent tool for the development water quality biomonitoring system of Hg2+ application.

A pyridyl functionalized rhodamine chemodosimeter for selective fluorescent detection of mercury ions and cell imaging

Rhodamines gain sustained attention owing to their great potential for probe design applications. Herein, the facile preparation of a new pyridyl functionalized rhodamine dye PR is reported, which has stable fluorescence signal in water with maximum emission peak at 594 nm and Stokes shift of 81 nm. Based on dye PR, a new fluorescent probe PRHg has been developed by modifying the spirolactone of PR with hydrazine hydrate so as to produce spirolactam recognizing group for sensing of Hg²⁺. PRHg exhibits high selectivity and sensitivity towards Hg²⁺ in water/ethanol (v/v = 4/1, pH = 7.0) by a specific Hg²⁺-binding promoted spirolactam ring opening and hydrolyzing process. And, the detection limit for Hg²⁺ is evaluated to be 8.5 nM. Besides, the probe can respond to Hg²⁺ within 40 min and over a wide pH range from 4.0 to 10.0. Moreover, PRHg (40 µM) performs low cytotoxicity to HeLa cells (over 91.0 % cell survival rate), which allows the probe to be employed for tracing intracellular Hg²⁺ by fluorescence imaging.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-visible absorption

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu²⁺ and Hg²⁺ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu²⁺ and Hg²⁺ in CH₃CN-H₂O (4:1, v/v) with off-on fluorescence and ratiometric ultraviolet-visible (UV-Vis) absorption changes. Additionally, Cu²⁺ is identified by opening a rhodamine spirocycle with a UV-Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg²⁺ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV-Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu²⁺ and Hg²⁺ by off-on fluorescence and ratiometric UV-Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu²⁺ and Hg²⁺ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.

Recent Progress in Fluorescent Sensors for Drug-Induced Liver Injury Assessment

Drug-induced liver injury (DILI) is a persistent concern in drug discovery and clinical medicine. The current clinical methods to assay DILI by analyzing the enzymes in serum are still not optimal. Recent studies showed that fluorescent sensors would be efficient tools for detecting the concentration and distribution of DILI indicators with high sensitivity and specificity, in real-time, in situ, and with low damage to biosamples, as well as diagnosing DILI. This review focuses on the assessment of DILI, introduces the current mechanisms of DILI, and summarizes the design strategies of fluorescent sensors for DILI indicators, including ions, small molecules, and related enzymes. Some challenges for developing DILI diagnostic fluorescent sensors are put forward. We believe that these design strategies and challenges to evaluate DILI will inspire chemists and give them opportunities to further develop other fluorescent sensors for accurate diagnoses and therapies for other diseases.

A dual-channel chemosensor based on 8-hydroxyquinoline for fluorescent detection of Hg2+ and colorimetric recognition of Cu2

A novel dual-channel chemosensor, 7-allylquinolin-8-ol (AQ), was synthesized based on 8-hydroxyquinoline for selective fluorescence detection of Hg²⁺ and colorimetric recognition of Cu²⁺. The chemosensor reacted with Hg²⁺ and generated a new Hg-containing compound with significantly enhanced fluorescence, which turned from faint blue to strong green. Further experiments indicated that AQ could be used to quantitatively detect Hg²⁺ via fluorescence spectroscopy with a low detection limit (2.1 nM). The good reversibility of the synthesized chemosensor was also demonstrated using NaBH₄. Moreover, AQ was successfully used for the detection of Cu²⁺ through the formation of a stable coordination compound, which exhibited an ultraviolet-visible (UV-Vis) ratiometric change, while its color changed from colorless to pale yellow under natural light. Additional experiments using various Cu²⁺ concentrations showed that the developed chemosensor could be further employed for the quantitative ratiometric estimation of Cu²⁺ by UV-Vis.

Cyanine-based fluorescent indicator for mercury ion and bioimaging application in living cells

A commercial cyanine dye IR-780 and a thioether-containing dicarboxylic acid ligand were used to construct the near-infrared fluorescent probe, which was used as a near-infrared fluorescent indicator for the determination of mercury ions in water and in living cells. This indicator displayed high specificity towards Hg²⁺ without any interference from other detecting species. Especially, the emission at 790 nm dramatically increased more than 25 times after interacting with Hg²⁺. The binding experiment showed that the indicator formed 1:1 complex with Hg²⁺. More, this indicator could be applied in the visualization of Hg²⁺ in living cells and measuring the Hg²⁺ concentration of tap-water sample.

A novel pillar[5]arene-based emission enhanced supramolecular sensor for dual-channel selective detection and separation of Hg2+

We constructed a supramolecular sensor (APRA–G) via a host–guest inclusion interaction between a rhodamine hydrazide-functionalized pillar[5]arene (APRA) and a bipyridine salt guest (G), which formed a stable dimer.

A Novel Ratiometric Fluorescent Probe for Mercury (II) ions and Application in Bio-imaging

Since the accumulation of mercury (II) ions in the environment and ecosystem causes serious problems to environment and disease, the recognition of Hg2+ ions and its bio-imaging is of high importance. In sight of the advantages of fluorescence probes, a new probe (PMH) was facilely synthesized by incorporating phenylimidazole fluorophore and 3-methyl-2- benzothiazolinone hydrazone hydrochloride monohydrate. The PMH probe exhibited a ratiometric response for Hg2+ ions with fluorescence intensity increasing at 520 nm and decreasing at 445 nm simultaneously. The PMH probe interacted with Hg2+ ions in seconds with high optical stability and showed good selectivity over other metal ions. In addition, the probe has excellent biocompatibility and imaging performance in cells and zebrafish.

An efficient biosensor for monitoring Alzheimer's disease risk factors: modulation and disaggregation of the Aβ aggregation process

An efficient biosensor to monitor Alzheimer's disease risk factors and inhibit Alzheimer's disease by disaggregating Aβ aggregation.

A two-photon fluorescent probe for colorimetric and ratiometric monitoring of mercury in live cells and tissues

Owing to the extreme toxicity of mercury, methods for its selective and sensitive sensing in solutions, and in live cells and tissues are in great demand.