Selective Fluorescence Research Articles

Alkyl substituents control the Cd2+-selectivity of fluorescence enhancement in N,N’-bis(2-quinolylmethyl)ethylenediamine derivatives

The TriMeOBQDMEN (N,N’-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N’-dimethylethylenediamine) has been reported as a Cd2+-selective fluorescence sensor (IZn/ICd = 22 % in the presence of 1 equiv. of metal ion) in DMF-H2O (1:1). Replacing the N-methyl substituents of TriMeOBQDMEN with isopropyl, benzyl, and phenyl groups decreases the metal binding affinity of the compound. Among them, the isopropyl derivative, TriMeOBQDIEN (N,N’-bis(5,6,7-trimethoxy-2-quinolylmethyl)-N,N’-diisopropylethylenediamine), exhibits improved Cd2+-selectivity (IZn/ICd = 7 % and 4 % in the presence of 1 and 20 equiv. of metal ion, respectively), partly due to the Zn2+-specific fluorescence decrease in the presence of excess amount of Zn(ClO4)2. Such a fluorescence decrease was not seen in DMF-HEPES buffer (1:1), as well as employing Zn(NO3)2 or ZnCl2 in DMF-H2O. These experimental observations were explained by the generation of proton in the presence of excess Zn(ClO4)2.

From Intercalation to External Binding: Ru(II) Complexes with a Spiro Ligand for TAR RNA Selective Binding and HIV-1 Reverse Transcriptase Inhibition.

As a typical RNA virus, the genetic information on HIV-1 is entirely stored in RNA. The reverse transcription activity of HIV-1 reverse transcriptase (RT) plays a crucial role in the replication and transmission of the virus. Non-nucleoside RT inhibitors (NNRTIs) block the function of RT by binding to the RNA binding site on RT, with very few targeting viral RNA. In this study, by transforming planar conjugated ligands into a spiro structure, we convert classical Ru(II) DNA intercalators into a nonintercalator. This enables selective binding to HIV-1 transactivation response (TAR) RNA on the outer side of nucleic acids through dual interactions involving hydrogen bonds and electrostatic attraction, effectively inhibiting HIV-1 RT and serving as a selective fluorescence probe for TAR RNA.

Highly selective fluorescence turn-on sensor for·thiol compounds detection

As a kind of commonly-used synthetic materials for many pesticides, thiol compounds, once being leaked, can cause serious harm to the environment and humans. Therefore, the efficient detection of thiol compounds is essential. In this study developed a turn-on fluorescent probe (Cu@Zn-CP) for the highly sensitive fluorescence detection of thiol compounds. The probe was constructed based on a zinc coordination polymer (Zn-CP), whose fluorescence was quenched through the effective doping of Cu2+ ions. After the introduction of methyl thioglycolate (MTC), a rapid fluorescence turn-on response was generated within 90 s with a low detection limit of 23 ppb. Even after being reused for five cycles, the sensor maintains excellent detection performance and demonstrates good recyclability. It can also detect MTC in river water, with a spike recovery rate between 98–103 %. Furthermore, the designed Cu@Zn-CP exhibits good universality for detecting multifarious thiol compounds, including L-cysteine, glutathione, monothioglycerol, and 2-hydroxy-1-ethanethiol. This result provides a potential recyclable fluorescent sensor for thiol compounds.

A metal mediated specific poly(cyclotriphosphazene-co-curcumin) fluorescent micro-probe for tetracycline sensing

The extensive use of tetracycline antibiotics (TCs) renders their widespread in the environment that may cause bacterial resistance. Thus, detection of residual TCs and understanding of their broader roles and impacts in the environment and soil ecology are is of critical significance. This paper describes the investigation of a Mg (II)-specific fluorescent micro-probe (PCC–Mg) based on cyclotriphosphazene (Cpz) and curcumin for classical TC•HCl sensing with a low detection limit of 29 nM and a fast response time of less than 10 s. The sensing mechanism is presumably attributed to specific Mg2+ binding with TCs since the fluorescence enhancement is not observed in the absence of Mg2+ and not influenced by the presence of several metal ions and anions. The binding of Mg2+ to curcumin/TC and the formation of TC-metal-curcumin ternary complex can be concluded with NMR and mass spectrometry. Moreover, for the purpose of easy applications, test strips are made to render visual detection of TC with noticeable and selective fluorescence enhancement. The formation of the ternary complex between Cur from the popular herb Curcuma longa and TC from Streptomyces spp. mediated by metal ions also hints a potential role of microbiolochemical-phytochemical interactions in maintaining biodiversity and equilibria in soil microecology.

One-pot fabrication of aluminium ion anchoring boric acid-carbon dots hybrid system and its highly selective fluorescence sensing for fluorine ion in water environment

Fluorine is one of the essential trace elements for human body, which is essential for calcification process in living organisms. In the paper, a “off–on” fluorescence sensor for fluorine ion based on aluminium ion and boric acid codoped carbon dots was synthesized and characterized. According to fluorescence analysis, the water-soluble sensor exhibited highly selective and sensitive for fluorine ion. In sensing process, F- could bind to Al3+ after the addition of fluorine ion, which resulted in the decomposition of Al-BA-CDs system, then intense yellow fluorescence signal appeared. Moreover, the fluorescence sensor exhibited low detecting limit (5.0 nanomolar level) by fluorescence titration spectrum. In addition, according to evaluate the fluorescence sensing properties of F- in HepG2 cell and zebra fish, this job greatly extended the use of F- sensor from aluminium ion and boric acid codoped carbon dots in organism. The work also provided an interesting idea for fabricating water-soluble fluorescence sensor for F-.

A Benzothiadiazole-Based Zn(II) Metal–Organic Framework with Visual Turn-On Sensing for Anthrax Biomarker and Theoretical Calculation

2,6-pyridine dicarboxylic acid (DPA) is an exceptional biomarker of notorious anthrax spores. Therefore, the rapid, sensitive, and selective quantitative detection of DPA is extremely significant and urgent. This paper reports a Zn(II) metal–organic framework with the formula of {[Zn6(NDA)6(DPBT)3] 2H2O·3DMF}n (MOF-1), which consists of 2,6-naphthalenedicarboxylic acid (2,6-NDA), 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole (DPBT), and Zn(II) ions. Structural analysis indicated that MOF-1 is a three-dimensional (3D) network which crystallized in the monoclinic system with the C2/c space group, revealing high pH, solvent, and thermal stability. Luminescence sensing studies demonstrated that MOF-1 had the potential to be a highly selective, sensitive, and recyclable fluorescence sensor for the identification of DPA. Furthermore, fluorescent test paper was made to detect DPA promptly with color changes. The enhancement mechanism was established by the hydrogen-bonding interaction and photoinduced electron transfer transition between MOF-1 and DPA molecules.

Regulation effects on naphthalimide self-assembly system by terminal pyridine isomers and the coordination of metal ions

Three novel naphthalimide-based gelators (NAPP, NAMP and NAOP) linked three different amines: 4-(aminomethyl)pyridine, 3-(aminomethyl)pyridine, or 2-(aminomethyl)pyridine were designed and synthesized. NAPP, NAMP and NAOP could self-assemble into fluorescent gels in some solvents and formed a variety of morphologies. The self-assembly behaviors of three gelators in DMSO/H2O (10/1, v/v) were characterized by UV–vis absorption, fluorescence, Fourier transform infrared (FTIR), X-ray diffractions (XRD) and water contact angle experiment, and the effect of different N sites in pyridine in this self-assembly system was investigated. On the base of coordination ability of pyridine groups to metal ions, the self-assembly process could be regulated by the addition of metal ions. NAPP, NAMP and NAOP solutions had highly selective and ultrafast fluorescence detection capabilities for Fe3+ with a low limit of detection. The self-assembly structure and surface wettability of the gel self-assembly system could be adjusted by adding metal ions. The hydrophobic surface of xerogels NAPP and NAMP is transformed into a hydrophilic surface at the present of Fe3+. And the hydrophilic and hydrophobic surfaces of NAPP and NAMP could realize the transformation of hydrophilic and hydrophobic surfaces by the coordination of metal ions. This study provided a way for regulating the self-assembly process by the distance between the N site on pyridine and the amide segment and metal coordination.

Synthesis of biscarbazole derivative, detection of the “on-off” sensor property of Cu2+ by fluorimetry, and anti-cancer evaluation

Biscarbazole derivative probe (6) (Z)-2-(3-(((9-heptyl-9H-carbazol-3-yl)methylene)amino)-9H-carbazol-9-yl)ethan-1-ol containing an imine group, which is a sensitive and selective fluorescence chemosensor, was designed and synthesized for the effective evaluation of Cu2+ metal ion levels. The synthesized compounds were characterized using 1H NMR, 13C NMR, FT-IR, and MALDI-TOF MS (for compound 6) spectroscopic data. The interaction model between probe 6 and Cu2+ was determined by combining fluorescence methods, 1H NMR titration, Job’s plot, and theoretical calculations. For probe 6, the fluorogenic recognition of Cu2+ was investigated by fluorescence spectroscopy, and the optical changes caused by Cu2+ ions were carried out in ACN/H2O (50:50) solution at pH 7.0. Fluorescence probe 6 was found to “turn-off” its fluorescence in the presence of paramagnetic Cu2+ ions. Probe 6 was determined to have a rapid response within 40s and showed a fluorescence response to Cu2+ with a low detection limit of 0.16 μM. Additionally, in vitro anticancer activity and cell imaging studies of probe 6 against the prostate cell line (PC-3) were performed.

A highly efficient, selective, reversible and ultra-sensitive fluorescence “Turn-ON” chemosensor for aluminium ions by a novel Schiff base

The synthesis of a Schiff base-based chemosensor, denoted as H6L, was accomplished through the condensation reaction of Isophthalohydrazide and 2,6-dihydroxybenzaldehyde in an ethanol solvent. The resulting compound was further characterized using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, as well as high-resolution mass spectrometry (HRMS). Extensive research has been conducted on several facets of metal sensing phenomena, revealing that the Schiff base H6L demonstrates discerning and expeditious fluorescence sensing characteristics specifically towards Al (III) in acetonitrile. The purported method detects Al (III) can be ascribed to the suppression of photo-induced electron transfer (PET) and the enhanced chelation-induced fluorescence (CHEF). The stoichiometry of metal–ligand complexes (2:1) was determined using Job’s plots titrations, HRMS and subsequently confirmed using NMR titration studies. The H6L sensors demonstrated remarkable fluorescence sensing capabilities in acetonitrile, with a low detection limit (LOD) of 0.44 μM. This LOD is suitably low for the detection of Al3+, which is commonly found in many environmental and biological systems. Fluorescence lifetime measurement provides additional evidence of complexation of H6L with Al (III). The reversibility of the sensor was demonstrated through the introduction of pyrophosphate (PPi), which forms a complex with aluminium ions, thereby releasing the chemo sensor for subsequent utilization. The findings suggest that H6L has the potential to serve as a viable probe for the detection and identification of Al3+ ions.

Copper complex@Paclitaxel: A new dual-functional fluorescent-responsive composite material and treatment on esophageal cancer cells

Esophageal cancer (EC) is a common and fatal malignant tumor of the digestive tract, characterized by high morbidity and mortality. Despite advances in surgery, radiotherapy, and anti-cancer drugs, the five-year survival rate remains low. Therefore, exploring effective therapeutic agents to inhibit the proliferation and invasion of EC is crucial. In this study, a novel coordination polymer CP1 was synthesized by reacting the bifunctional ligand 2,5-bis(1H-1,2,4-triazol-1-yl)terephthalic acid (H2dttpa) containing carboxylic acid and triazolyl groups with Cu(NO3)2·3H2O in a mixed solvent of water and N,N-dimethylformamide. Structural analysis revealed that CP1 adopts a two-dimensional layered network with a trinodal (3,4,4)-connected topology. Furthermore, CP1 exhibits excellent fluorescent properties due to charge transfer from the ligand to the metal, making it suitable for selective and sensitive fluorescence sensing of Fe3+ with a quenching efficiency of up to 90.5 %. This indicates the potential application of CP1 as a fluorescent sensor for Fe3+ detection. Moreover, paclitaxel was selected as a model drug to form a prodrug (CP1@Paclitaxel) with hydrogen bonding enhancing the interaction between the prodrug and CP1. The photothermal properties of CP1@Paclitaxel were investigated, showing an increase of 13 °C and 25 °C, respectively, in a concentration-dependent manner. The therapeutic activity of the newly synthesized system against EC cancer was evaluated, and its specific mechanism of action was investigated. This design provides a novel approach to address drug delivery issues in EC and offers a flexible strategy for expanding the biomedical applications of metal–organic frameworks (MOFs).

Femtosecond laser activation of the photochemistry of bismuth and associated three-dimensional sub-micron fluorescence patterning

Localized sub-micrometer-scale visible and near-IR fluorescence structures have been achieved in three-dimension (3D) thanks to femtosecond laser-activated photochemistry of Bismuth in a Bismuth-doped phosphate glass. These structures exhibit high fluorescence contrast with good spatial resolution with spectral emission in the red and near-IR ranges. These fluorescence properties arise from femtosecond laser-induced multi-photon absorption and the creation of free electrons, which activates local redox reactions of Bi3+ that allow for the dose-dependent formation of low valence Bismuth ions such as Bi2+ and Bi+. These new species promote not only new selective fluorescence emission properties in the VIS and near-IR spectral range but also co-localized positive refractive index changes. The thermal treatment of 3D patterns evidences the possibility of Bismuth cluster formation with good thermal stability up to the glass temperature transition. These observations open the way for laser-inscribed photonic integrated circuits for potential laser amplification devices in the second telecommunication windows around 1.3 μm.

Selective fluorescence quenching for volatile benzaldehyde on Zn-based coordination polymers

Benzaldehyde (BZH) is a hazardous substance that can cause respiratory irritation and acute poisoning if it leaks excessively into the environment. Fluorescence detection of BZH is common in liquid phase, but still rare in gas phase. In this study, we synthesized a new complex, [Zn(bpe)(SO4)(H2O)]·2H2O (Zn-bpe), with two-dimensional layered structure. Interestingly, it exhibited good fluorescence quenching behavior not only for BZH dissolved in ethanol, but also for volatile BZH which is detected on thin films prepared by combining complexes with polyvinyl alcohol (Zn-bpe@PVA). Moreover, the limit of detection (LOD = 19.6 mg·L-1) of the latter is firstly calculated through the linear fitting of emission intensities. The quenching mechanism was attributed to the energy transfer from the complex to BZH molecules, which was confirmed by in situ IR spectra and DFT calculations.

A fluorescein conjugate as colorimetric and red-emissive fluorescence chemosensor for selective recognition Cu2+ ions

A derivative of fluorescein was designed, synthesized, and characterized by FT-IR, 1H, 13C NMR, mass spectrometry, and quantum chemical calculations. When applied to the set of solutions containing different cations, it has shown a selective colorimetric and fluorescence response for Cu2+. A visible color change from colorless to purple and from non-fluorescent to red fluorescence was observed. A linear relationship between Cu2+ concentration and absorbance or fluorescence intensity was demonstrated with low detection limits (0.64 and 0.24 μM, respectively) in the acetonitrile/water mixture. Test strips are made by impregnating filter paper with acetonitrile chemosensor 1 solution and used to detect Cu2+ in water. The strips noticeably change their color from colorless to purple.

Spectrofluorometric determination of futibatinib in human plasma and pharmaceutical formulations

Futibatinib is a powerful inhibitor of fibroblast growth factor receptors that impedes its phosphorylation and subsequently leading to a reduction in in cell viability across various cell lines. Futibatinib was approved for initial use as an effective treatment for several diseases, including non-small cell lung cancer and breast cancer. Herein, a novel selective fluorescence probe was created for futibatinib quantification in various matrices, including pharmaceutical formulation and human plasma. The technique primarily depends on futibatinib’s chemical conversion into a fluorescent product through a reaction with trimethylamine and bromoacetyl bromide. The created fluorescent probe exhibits maximum emission peak at 338 nm upon excitation at 248 nm. The method provided a low detection limit of 0.120 ng/mL and maintained a linear concentration-dependent relationship across the range of 1–200 ng/mL. High sensitivity, accuracy and precision were demonstrated for futibatinib quantification in pharmaceutical formulation and spiked plasma matrix by the method, which was validated in accordance with ICH requirements.

A hydroxyl-rich covalent organic framework for the precisely selective fluorescence sensing of explosives with high sensitivity

Covalent organic Frameworks (COFs) have become a new platform for functional research and material design. A novel covalent organic skeleton (DHB-TFP COF) was synthesized from 2-hydroxybenzene-1,3,5-tricarbaldehyde and 3,3′-dihydroxybenzidine using Schiff base reaction. DHB-TFP COF is a highly stable porous crystalline material and exhibits exceptional thermal and chemical resistance. DHB-TFP COF exhibited a selective and sensitive “turn-off” fluorescence response to 4-NP in ethanol, and TNP not only significantly quenched the fluorescence of DHB-TFP COF but also caused the obvious red-shift. The fluorescence intensity of DHB-TFP COF exhibited a linear correlation with the concentration of 4-NP with a detection limit of 0.40 μM. Furthermore, the maximum fluorescence peak observed for DHB-TFP COF demonstrated a linear relationship with TNP concentration with a detection limit of 11.15 μM. DHB-TFP COF exhibited satisfactory recovery in the detection of 4-NP and TNP in actual water sample indicating its practical application potential. The O atoms of rich hydroxyl and N atoms of C = N present on the surface of DHB-TFP COF scaffold can establish strong hydrogen bonds with 4-NP and TNP, facilitating their mutual interaction. The spectra studies indicated that the fluorescence quenching mechanism can be attributed to the absorption competitive quenching (ACQ) and fluorescence resonance energy transfer (FRET) mechanism. This study not only proposed the approach for synthesizing novel structured organic frameworks, but also developed a highly selective and sensitive fluorescence chemical sensor for identifying and detecting 4-NP and TNP.

On-Site Quantitative Visualization of Singlet Oxygen in Crops via an Organic Small Molecule-Based Ratiometric Fluorescent Probe and a Mobile Fluorescence Analysis Device.

Singlet oxygen (1O2) plays imperative roles in a variety of biotic or abiotic stresses in crops. The change of its concentration within a crop is closely related to the crop growth and development. Accordingly, there is an urgent need to develop an efficient analytical method for on-site quantitative detection of 1O2 in crops. Here, we judiciously constructed a novel ratiometric fluorescent probe, SX-2, for the detection of 1O2 in crops. Upon treating with 1O2, probe SX-2 displayed highly selective ratiometric fluorescence response, which is favorable for the quantitative detection of 1O2. Concurrently, the fluorescence solution color of probe SX-2 was varied, obviously from blue to yellow, indicating that the probe is beneficial for on-site detection by the naked eye. Sensing reaction mechanism studies showed that the 2,3-diphenyl imidazole group in SX-2 could function as a new selective recognition group for 1O2. Probe SX-2 was utilized for the detection of photoirradiation-induced 1O2 and endogenous 1O2 in living cells. The changes in the 1O2 level in zebrafish were also tracked by fluorescence imaging. In addition, the production of 1O2 in crop leaves under a light source of different wavelengths was studied. The results demonstrated more 1O2 were produced under a light source of 365 nm. Furthermore, to achieve on-site quantitative detection, a mobile fluorescence analysis device has been made. Probe SX-2 and mobile fluorescence analysis device were capable of on-site quantitative detecting of 1O2 in crops. The method developed herein will be convenient for the on-site quantitative measurement of 1O2 in distinct crops.

A turn-off fluorescent sensor based on Schiff base incorporating diformyl phenol moiety for the detection of Cu2+ in aqueous solution at nanomolar level and its application in living cells

Given the critical role of trace copper ion in human health, its sensitive detection in environmental and biological samples is crucial. We, herein, designed and synthesized a diformyl phenol-based turn-off fluorescent sensor ((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis (methanylylidene)) bis (azanylylidene)) bis(4-hydroxy-2H-chromen-2-one) (MH-4)) for the spectrofluorometric detection of Cu2+ ion, which has sensitive and selective fluorescence quenching over other competitive metal ions. The efficiency and fast response of the sensor were confirmed by UV–Visible, fluorescence spectral changes, which may be due to the formation of coordination bond between MH-4 and Cu2+ ions. The binding stoichiometry of MH-4 with Cu2+ was examined with the help of UV–Vis and fluorescence titrations, and Job’s plot, which gives a 1:1 coordination stoichiometry; this is further confirmed through MS studies. The binding constant of the complex was found to be 9.4 x 107 M−1. Then, the absorbance and fluorescence-based detection limits were calculated to define the sensitivity range of the proposed sensor and were found to be 69.30 nM and 37.40 nM, respectively. Finally, a live cell image study of MH-4 in L929 (murine aneuploid fibrosarcoma) cells was also performed to test the cell permeability of MH-4 and its effectiveness for selective detection of Cu2+ in living cells.

A novel Psidium guajava and Cerium-MOF based dual-responsive bio-composite for the synchronous adsorptive removal and fluorescence detection of tetracycline antibiotics

The apprehensions about water contamination conduced by tetracycline antibiotics have raised serious concerns in scientific community worldwide. The researchers are intensively looking for materials that are sustainable and extend dual applicability in removal as well as detection of these contaminants. However, in this pursuit, fabrication of novel materials is still a great challenge. In this vein, inspired by the prodigious union of MOF and biobased materials, as enunciated by literature reports, present study unveils the fabrication of a novel dual responsive Psidium guajava and Cerium-MOF based bio-composite for simultaneous adsorption and fluorescence detection of tetracycline antibiotics. The fabricated Ce-MOF/0.5-GLP composite displayed excellent adsorption potential for removal of TCs within a very short initial time duration and rendered high adsorption capacities i.e. 81.30, 75.18 and 63.69 mg g−1 for DC, MC and TC, respectively. Conjointly, the fabricated bio-based Ce-MOF/0.5-GLP composite was engaged for selective fluorescence detection of TCs. The sensor exhibited exquisite selectivity and sensitivity for detection of TCs with low detection limit values i.e. 94.3 nM, 71.4 nM and 74.2 nM for DC, MC and TC, respectively. In light of the aforementioned findings, the developed composite illustrates a workable and realistic method for dealing with TCs via removal and detection.

A highly selective dual-signal response ratiometric fluorescence sensing strategy for malachite green in fish based on carbon dots/copper nanoclusters nanocomposite

Malachite green (MG), a widely used antiparasitic agent, poses health risks to human due to its genotoxic and carcinogenic properties. Herein, a stable dual-emission fluoroprobe of carbon dots/copper nanoclusters is prepared for highly selective detection of MG based on the inner filter effect. This probe exhibits characteristic emission bands at 435 and 625 nm when excited at 376 nm. After adding MG, the both emission signals were significantly quenched, and the ratio of fluorescence intensity (F435/F625) was linearly related to the concentration of MG in the range of 0.05–40 μmol L−1 with a limit of detection of 18.2 nmol L−1. Meanwhile, the two signals exhibit linear relationships with the concentration of MG, respectively, and the corresponding detection results were consistent. The fluoroprobe was successfully used for the detection of MG in fish samples with the recoveries ranging from 96.0% to 103.8% and a relative standard deviation of <3.3%.

Hydrazone-linked covalent organic framework functionalized with cysteine as a fluorescence sensor and Exploration of paper chip for p-nitrophenol detection

The large use and emission of p-nitrophenol (p-NP) seriously pollute the environment and endanger human health. In this work, a hydrazone-linked fluorescent covalent organic framework (BATHz-COF) was simply synthesized at room temperature and covalently linked N-acetyl-L-cysteine (NALC) via the "thiol-ene" click reaction, where carboxyl groups were introduced to improve dispersion and fluorescence intensity. As a rapid, good selectivity and reusability fluorescence sensor, the obtained COF-NALC has been used for quantitative analysis of p-NP predicated on the internal filtering effect (IFE). Under optimal conditions, COF-NALC enabled quantitative detection of p-NP with a linear range of 5–50 μM and the detection limit was 1.46 μM. The application of COF-NALC to the detection of p-NP in river water samples was successful, and the satisfactory recoveries were 98.0%–109.3%. Furthermore, the fluorescent COF paper chips constructed by in situ growth were combined with a smartphone to build a visual platform for the quick and real-time detection of p-NP, providing an excellent illustration for the development of intelligent fluorescence sensing in environmental analysis.