Fluorescent sensing of fluoride in cellular system

Development of an innovative turn-on fluorescent probe for targeted in-vivo detection of nitric oxide in rat brain extracts as a biomarker for migraine disease

Nitric oxide (NO) is one of the reactive nitrogen species (RNS) that has been proposed to be a key signaling molecule in migraine. Migraine is a neurological disorder that is linked to irregular NO levels, which necessitates precise NO quantification for effective diagnosis and treatment. This work introduces a novel fluorescent probe, 2,3-diaminonaphthelene-1,4-dione (DAND), which was designed and synthesized to selectively detect NO in-vitro and in-vivo as a migraine biomarker. DAND boasts high aqueous solubility, biocompatibility, and facile synthesis, which enable highly selective and sensitive detection of NO under physiological conditions. NO reacts with diamine moieties (recognition sites) of DAND, results in the formation of a highly fluorescent product (DAND-NO) known as 1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione at λem 450 nm. The fluorescence turn-on sensing mechanism operates through an intramolecular charge transfer (ICT) mechanism. To maximize fluorescence signal intensity, parameters including DAND concentration, reaction temperature, reaction time and pH were systematically optimized for sensitive and precise NO determination. The enhanced detection capability (LOD = 0.08 μmol L-1) and high selectivity of the probe make it a promising tool for NO detection in brain tissue homogenates. This demonstrates the potential diagnostic value of the probe for individuals suffering from migraine. Furthermore, this study sheds light on the potential role of zolmitriptan (ZOLM), an antimigraine medication, in modulating NO levels in the brain of rats with nitroglycerin-induced migraine, emphasizing its significant impact on reducing NO levels. The obtained results could have significant implications for understanding how ZOLM affects NO levels and may aid in the development of more targeted and effective migraine treatment strategies.

Small Molecule Optical Probes for Detection of H2S in Water Samples: A Review

Hydrogen sulfide (H2S) is closely linked to not only environmental hazards, but also it affects human health due to its toxic nature and the exposure risks associated with several occupational settings. Therefore, detection of this pollutant in water sources has garnered immense importance in the analytical research arena. Several research groups have devoted great efforts to explore the selective as well as sensitive methods to detect H2S concentrations in water. Recent studies describe different strategies for sensing this ubiquitous gas in real-life water samples. Though many of the designed and developed H2S detection approaches based on the use of organic small molecules facilitate qualitative/quantitative detection of the toxic contaminant in water, optical detection has been acknowledged as one of the best, attributed to the simple, highly sensitive, selective, and good repeatability features of the technique. Therefore, this review is an attempt to offer a general perspective of easy-to-use and fast response optical detection techniques for H2S, fluorimetry and colorimetry, over a wide variety of other instrumental platforms. The review affords a concise summary of the various design strategies adopted by various researchers in constructing small organic molecules as H2S sensors and offers insight into their mechanistic pathways. Moreover, it collates the salient aspects of optical detection techniques and highlights the future scope for prospective exploration in this field based on the limitations of the existing H2S probes.

Dual-Responsive Near-Infrared BODIPY-Based Fluorescent Probe for the Detection of F- and HClO in Organisms

Fluoride anions (F-) play a crucial role in human physiological processes. However, excessive intake of F- would affect oxygen metabolism and promote the generation of oxygen-free radicals. Hence, it is essential to develop a precise and efficient fluorescent probe for visualizing F--induced oxidative stress. In this work, we developed the first bifunctional BODIPY-based fluorescent probe dfBDP with p-tert-butyldimethylsilanolate benzyl thioether as the sensing site for the detection of F- and HClO via two distinct reactions, the self-immolative removal and the thioether oxidation, which generate the sensing products with two nonoverlap fluorescence bands: 800-1200 and 500-750 nm, respectively. The probe dfBDP displays rapid response, high specificity, and sensitivity for the detection of F- (LOD, 316.2 nM) and HClO (LOD, 33.9 nM) in vitro. Cellular imaging reveals a correlation between F--induced oxidative stress and the upregulation of HClO. Finally, probe dfBDP was employed to detect F- and HClO in mice under the stimulation of F-. The experimental results display that the level of HClO elevates in the liver of mice.

Molecular Accessibility and Diffusion of Resorufin in Zeolite Crystals

We have used confocal laser scanning microscopy on the small, fluorescent resorufin dye molecule to visualize molecular accessibility and diffusion in the hierarchical, anisotropic pore structure of large (~10 μm-sized) zeolite-β crystals. The resorufin dye is widely used in life and materials science, but only in its deprotonated form because the protonated molecule is barely fluorescent in aqueous solution. In this work, we show that protonated resorufin is in fact strongly fluorescent when confined within zeolite micropores, thus enabling fluorescence microimaging experiments. We find that J-aggregation guest-guest interactions lead to a decrease in the measured fluorescence intensity that can be prevented by using non-fluorescent spacer molecules. We characterized the pore space by introducing resorufin from the outside solution and following its diffusion into zeolite-β crystals. The eventual homogeneous distribution of resorufin molecules throughout the zeolite indicates a fully accessible pore network. This enables the quantification of the diffusion coefficient in the straight pores of zeolite-β without the need for complex analysis, and we found a value of 3×10-15  m2  s-1 . Furthermore, we saw that diffusion through the straight pores of zeolite-β is impeded when crossing the boundaries between zeolite subunits.

Photo- and Sono-Active Food Colorants Inactivating Bacteria

Food colorants are commonly used as excipients in pharmaceutical and nutraceutical fields, but they have a wide range of other potential applications, for instance, as cytotoxic drugs or mediators of physical antimicrobial treatments. The photodynamic antibacterial activity of several edible food colorants is reported here, including E127, E129, E124, E122, E133, and E150a, alongside Rhein, a natural lipophilic antibacterial and anticancer compound found in medicinal plants. Minimal inhibitory concentration (MIC) values for S. aureus and E. coli showed that E127 and Rhein were effective against both bacteria, while other colorants exhibited low activity against E. coli. In some cases, dark pre-incubation of the colorants with Gram-positive S. aureus increased their photodynamic activity. Adding Rhein to E127 increased the photodynamic activity of the latter in a supportive mode. Optional sensing mechanism pathways of combined E127/Rhein action were suggested. The antibacterial activity of the studied colorants can be ranged as follows: E127/Rhein >> E127 >> E150a > E122 > E124 >> E129 ≈ E133. E127 was also found to exhibit photodynamic properties. Short ultrasonic treatment before illumination caused intensification of E127 photodynamic activity against E. coli when applied alone and especially in combination with Rhein. Food colorants exhibiting photo- and sonodynamic properties may have good potential in food preservation.

Interaction of Ions in Organic and Aqueous Media with an Ion-Pair Sensor Equipped with a BODIPY Reporter: An ON1-OFF-ON2-ON3 Fluorescent Assay

Here, we present a ditopic ion-pair sensor, B1, containing the BODIPY reporter unit in its structure, which is shown to be able-thanks to the presence of two heterogeneous binding domains-to interact with anions in an enhanced manner in the presence of cations. This enables it to interact with salts even in 99% aqueous solutions, making B1 a good candidate in terms of visual salt detection in the aquatic environment. Receptor B1's ability to extract and release salt was applied in the transport of potassium chloride through a bulk liquid membrane. Working with a concentration of B1 in the organic phase and with the presence of a specific salt in an aqueous solution, an inverted transport experiment was also demonstrated. By varying the type and the amount of the anions added to B1, we were able to develop diverse optical responses, including a unique four-step ON1-OFF-ON2-ON3 output.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

FluorMango, an RNA-Based Fluorogenic Biosensor for the Direct and Specific Detection of Fluoride

Nucleic acids are not only essential actors of cell life but also extremely appealing molecular objects in the development of synthetic molecules for biotechnological application, such as biosensors to report on the presence and concentration of a target ligand by emission of a measurable signal. In this work, FluorMango, a fluorogenic ribonucleic acid (RNA)-based biosensor specific for fluoride is introduced. The molecule consists of two RNA aptamer modules, a fluoride-specific sensor derived from the crcB riboswitch which changes its structure upon interaction with the target ion, and the light-up RNA Mango-III that emits fluorescence when complexed with a fluorogen. The two modules are connected by an optimized communication module identified by ultrahigh-throughput screening, which results in extremely high fluorescence of FluorMango in the presence of fluoride, and background fluorescence in its absence. The value and efficiency of this biosensor by direct monitoring of defluorinase activity in living bacterial cells is illustrated, and the use of this new tool in future screening campaigns aiming at discovering new defluorinase activities is discussed.

Development of carbazole-based fluorescent probe for highly sensitive application in fluoride ion detection

Fluorine is a necessary element for human, which is closely related to life activities, such as metabolism of teeth and bone tissue. A small amount of fluoride ions can promote the strengthen of our body. However, a large amount of fluoride ions will damage the human immune system to produce organ diseases. Sensitive and rapid detection of fluoride ions has attracted great interests for researchers. In this work, a reactive fluorescent probe SCP for detection of fluoride ions with high quantum yield was designed and synthesized based on the carbazole ring. Subsequently, the photophysical properties of the probe SCP were carefully studied. At last, SCP performed 62.8% quantum yield in physiological condition, excellent ability of quantitative analysis, well selectivity, and distinguishing features for HepG2 cell imaging.

Turn-on fluorescent capsule for selective fluoride detection and water purification

It has been a long-standing challenge to develop organic molecular capsules for selective anion binding in water. Here, selective recognition of aqueous fluoride was achieved through triple protonation of a hemicryptophane (L), which is composed of a fluorescent cyclotriveratrylene (CTV) cap and tris(2-aminoethyl)amine (tren) as the anion binding site. Fluoride encapsulation by [3H-L]³⁺ was evidenced by ¹H NMR, ¹⁹F NMR, LC-MS, and X-ray crystallography. In addition, [3H-L]³⁺ exhibited a 'turn-on' fluorescence signal (λ _em = 324 nm) upon fluoride addition. An apparent association constant K _A = (7.5 ± 0.4) × 10⁴ M^-1 and a detection limit of 570 nM fluoride were extracted from the fluorescence titration experiments in citrate buffer at pH 4.1. To the best of our knowledge, [3H-L]³⁺ is the first example of a metal-free molecular capsule that reports on fluoride binding in purely aqueous solutions with a fluorescence response. Finally, the protonated capsule was supported on silica gel, which enabled adsorptive removal of stoichiometric fluoride from water and highlights real-world applications of this organic host-guest chemistry.

Progress in the Development of Imidazopyridine-Based Fluorescent Probes for Diverse Applications

Different classes of Imidazopyridine i.e., Imidazo[1,2-a]pyridine, Imidazo[1,5-a] pyridine, Imidazo[4,5-b]pyridine, have shown versatile applications in various fields. In this review, we have concisely presented the usefulness of the fluorescent property of imidazopyridine in different fields such as imaging tools, optoelectronics, metal ion detection, etc. Fluorescence mechanisms such as excited state intramolecular proton transfer, photoinduced electron transfer, fluorescence resonance energy transfer, intramolecular charge transfer, etc. are incorporated in the designed fluorophore to make it for fluorescent applications. It has been widely employed for metal ion detection, where selective metal ion detection is possible with triazole-attached imidazopyridine, β-carboline imidazopyridine hybrid, quinoline conjugated imidazopyridine, and many more. Also, other popular applications involve organic light emitting diodes and cell imaging. This review shed a light on recent development in this area especially focusing on the optical properties of the molecules with their usage which would be helpful in designing application-based new imidazopyridine derivatives.

Mitochondria targeted dual-fluorescent probe for bio-imaging viscosity and F- with different fluorescence signals

The F^- ion and viscosity both affect the physiological state of mitochondria and to the best of our knowledge no fluorescent probe is reported for the dual detection of mitochondrial viscosity and F^- ion through different signals. DMAS-Si is weakly red fluorescent due to free intramolecular rotation between dimethylaminophenyl and pyridinium moieties and PET from silyloxy to the pyridinium moiety. In viscous medium (glycerol 90 %), the rotation is restricted and 18-fold increase in red-fluorescence (λ_em 637 nm) is observed. On reaction with F^- ion, the desilylations followed by release of quinone-methide from DMAS-Si gives intense green fluorescence (λ_em 515 nm) due to formation of DMAS. DMAS-Si can detect as low as 50 nM F^-. DMAS-Si shows good permeability to HeLa cells and preferably targets mitochondria. It has been used for imaging of increased viscosity in mitochondria of HeLa cells in the presence of nystatin through red fluorescence and exogenous F^- ion by appearance of green fluorescence.

Optical Chemical Sensing of Iodide Ions: A Comprehensive Review for the Synthetic Strategies of Iodide Sensing Probes, Challenges, and Future Aspects

Among several anions, iodide (I^- ) ions play a crucial role in human biological activities. In it's molecular form (I₂ ), iodine is utilized for several industrial applications such as syntheses of medicines, fabric dyes, food additives, solar cell electrolytes, catalysts, and agrochemicals. The excess or deficiency of I^- ions in the human body and environmental samples have certain consequences. Therefore, the selective and sensitive detection of I^- ions in the human body and environment is vital for monitoring their overall profile. Amongst various analytical techniques for the estimation of I^- ions, optical-chemical sensing possesses the merits of high sensitivity, selectivity, and utilizing the least amount of sensing materials. The distinctive aims of this manuscript are (i) To comprehensively review the development of optical chemical sensors (fluorescent & colorimetric) reported between 2001-2021 using organic fluorescent molecules, supramolecular materials, conjugated polymers, and metal-organic frameworks (MOFs). (ii) To illustrate the design and synthetic strategies to create specific binding and high affinity of I^- ions which could help minimize negative consequences associated with its large size and high polarizability. (iii) The challenges associated with sensitivity and selectivity of I^- ions in aqueous and real samples. The probable future aspects concerning the optical chemical detection of I^- ions have also been discussed in detail.

Fabrication of In(III)-alizarin red S complex trap for efficient detection of fluoride ion in aqueous environs

The work discusses about the synthesis of indium-alizarin red S complex followed by its application toward the sensing of F¯ ion. At first, the interaction between indium and alizarin red S dye was studied at three different pH medium, pH 4, 7 and 9, of which pH 7 gave the best result. The indium-alizarin red S complex so obtained was then utilized for the ratiometric sensing of fluoride ion using absorption spectroscopy with variation of temperature. The lowest limit of detection (0.040 mM) was obtained at 313 K. The mechanism for the sensing of F¯ ion was then investigated using isothermal titration calorimetry. The endothermic nature of the interaction between F¯ ion with indium-alizarin red S complex shows temperature dependence on the sensing experiment. At the end, the utility of the technique toward natural sample was also examined. The present work reports a simple, rapid and efficient detection of fluoride anion in environmental water samples.

Supramolecular self-assembly of a nitro-incorporating quinoxaline framework: insights into the origin of fluorescence turn-on response towards the benzene group of VOCs

Hazardous volatile organic compounds (VOCs) can significantly impact human health and the environment. Hence, the detection of VOCs is of foremost importance. A quinoxaline-based fluorimetric probe (1) unveils a notable "turn-on" fluorescence response towards mesitylene in the presence of other VOCs and common interfering ions in aqueous media. The sensing phenomenon involves specific 1 : 1 stoichiometric binding of the probe with mesitylene with a ∼2.66 ppm detection limit. Furthermore, the probe experiences morphological transformations from a fibril-network to a stone-shaped hetero-structure upon treatment with mesitylene, indicating mesitylene induced self-assembly. The detection induced self-assembly of the probe was further corroborated by dynamic-light-scattering (DLS) and fluorescence microscopy study. Importantly, this proposed approach is applicable to detect mesitylene in natural water sources and in the vapor phase using portable, low-cost filter paper strips.

A highly sensitive and selective fluoride sensor based on a riboswitch-regulated transcription coupled with CRISPR-Cas13a tandem reaction

Nucleic acid sensors have realized much success in detecting positively charged and neutral molecules, but have rarely been applied for measuring negatively charged molecules, such as fluoride, even though an effective sensor is needed to promote dental health while preventing osteofluorosis and other diseases. To address this issue, we herein report a quantitative fluoride sensor with a portable fluorometer readout based on fluoride riboswitch-regulated transcription coupled with CRISPR-Cas13-based signal amplification. This tandem sensor utilizes the fluoride riboswitch to regulate in vitro transcription and generate full-length transcribed RNA that can be recognized by CRISPR-Cas13a, triggering the collateral cleavage of the fluorophore-quencher labeled RNA probe and generating a fluorescence signal output. This tandem sensor can quantitatively detect fluoride at ambient temperature in aqueous solution with high sensitivity (limit of detection (LOD) ≈ 1.7 μM), high selectivity against other common anions, a wide dynamic range (0-800 μM) and a short sample-to-answer time (30 min). This work expands the application of nucleic acid sensors to negatively charged targets and demonstrates their potential for the on-site and real-time detection of fluoride in environmental monitoring and point-of-care diagnostics.

Carbon dots for cancer nanomedicine: a bright future

Cancer remains one of the main causes of death in the world. Early diagnosis and effective cancer therapies are required to treat this pathology. Traditional therapeutic approaches are limited by lack of specificity and systemic toxicity. In this scenario, nanomaterials could overcome many limitations of conventional approaches by reducing side effects, increasing tumor accumulation and improving the efficacy of drugs. In the past few decades, carbon nanomaterials (i.e., fullerenes, carbon nanotubes, and carbon dots) have attracted significant attention of researchers in various scientific fields including biomedicine due to their unique physical/chemical properties and biological compatibility and are among the most promising materials that have already changed and will keep changing human life. Recently, because of their functionalization and stability, carbon nanomaterials have been explored as a novel tool for the delivery of therapeutic cancer drugs. In this review, we present an overview of the development of carbon dot nanomaterials in the nanomedicine field by focusing on their synthesis, and structural and optical properties as well as their imaging, therapy and cargo delivery applications.

Sensing mechanism of a new fluorescent probe for hydrogen sulfide: photoinduced electron transfer and invalidity of excited-state intramolecular proton transfer

It is of great significance for biological research to develop efficient detection methods of hydrogen sulfide (H2S). When DFAN reacts with H2S, 2,4-dinitrophenyl ether group acting as an electron acceptor generates a hydroxyl-substituted 2,4-dinitrophenyl ether group, resulting in the disappearance of photoinduced electron transfer (PET), and the new formed DFAH can be observed, while being accompanied by a significant fluorescence. In the present study, the PET sensing mechanism of probe DFAN and the excited state intramolecular proton transfer (ESIPT) process of DFAH have been explored in detail based on the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Our theoretical results show that the fluorescence quenching of DFAN is caused by the PET mechanism, and the result of ESIPT mechanism is not due to the large Stokes shift fluorescence emission of DFAH. We also optimized the geometric structure of the transition state of DFAH. The frontier molecular orbitals and potential barrier show that the ESIPT process does not easy occur easily for DFAH. The enol structure of DFAH is more stable than that of the keto structure. The absence of the PET process resulted in the enol structure emitting strong fluorescence, which is consistent with the single fluorescence in the experiment. Above all, our calculations are sufficient to verify the sensing mechanism of H2S using DFAN.

Exogenous transforming growth factor-β1 prevents the inflow of fluoride to ameleoblasts through regulation of voltage-gated chloride channels 5 and 7

Dental fluorosis is a global issue. Although there are multiple causes of dental fluorosis, the precise mechanism remains controversial. Previous studies have demonstrated that extracellular fluoride may promote an accumulation of fluoride ions in ameloblasts, which may induce oxidative and endoplasmic reticulum stresses, leading to dental fluorosis. However, the exact process by which fluoride ions enter cells has not been determined. In the present study, intracellular fluoride concentration was determined using a newly developed specific fluorescent probe called probe 1. Under high extracellular fluoride concentrations, the fluorescence intensity of the ameloblasts increased, however, exogenous transforming growth factor-β1 (TGF-β1) was able to inhibit the increase. Furthermore, changes in the expression of the voltage-gated chloride channels 5 and 7 (ClC5 and ClC-7), which are responsible for the transport of fluoride were investigated. The results indicated that fluoride reduced the expression of endogenous TGF-β1 and increased the expression of ClC-5 and ClC-7. Additionally, exogenous TGF-β1 reduced the expression of ClC-5 and ClC-7. The results of the present study indicate that exogenous TGF-β1 may prevent accumulation of fluoride in ameloblasts through the regulation of ClC-5 and ClC-7 under high extracellular fluoride concentrations.

Ultrafast fluorescent probe with near-infrared analytical wavelength for fluoride ion detection in real samples

The first ultrafast fluorescence probe with response time in seconds (10 s) for fluoride ions (F^-) has been proposed by conjugating dimethylthiophosphoryl group as a recognition unit with the near-infrared fluorophore of hemicyanine. The response mechanism is the F^--induced cleavage of the dimethylthiophosphoryl group, along with the liberation of the fluorophore, which results in a distinctly enhanced fluorescence intensity at 730 nm (λ_ex = 680 nm). The fluorescence enhancement of the probe is directly proportional to the F^- concentration in the range of 10-300 µM with the detection limit of 4.28 µM. The probe has been successfully used to determine F^- concentration in real water and toothpaste samples as well as image F^- in living cells. The simplicity and quick response of this probe endow it with the ability of detecting F^- rapidly in real samples.

Highly selective fluorescent peptide-based chemosensors for aluminium ions in aqueous solution

Two novel fluorescent peptide-based chemosensors, including A (2-amino-benzoyl-Ser-Glu-Glu-NH₂) and B (2-amino-benzoyl-Ala-Glu-Pro-Glu-Ala-Glu-Pro-NH₂) were synthesized and characterized by nuclear magnetic resonance (NMR) spectra. These fluorescent probes exhibited excellent selective and sensitive responses to Al³⁺ ions over other metal ions in aqueous buffered solutions. The limits of detection for both chemosensors towards the Al³⁺ ions were in the order of ∼10^-7 M (A: 155 nM and B: 195 nM), which clearly indicates that these probes have significant potential for biological applications. They also displayed high binding affinity (1.3029 × 10⁴ M^-1 and 1.7586 × 10⁴ M^-1 relevant to A and B respectively). These two chemosensors are great analytical probes that produce turn-on responses upon binding to Al³⁺ ions through an intramolecular charge transfer (ICT) mechanism. In addition, the application of both chemosensors was examined over a wide range of pH. The fluorescent peptide-based probes and Al³⁺ form a 1:1 coordination complex according to the ESI-MS and Job's plot analysis. Notably, upon addition of Al³⁺ to these chemosensors, a fluorescence enhancement of approximately 8-fold was observed and the binding mode was determined using NMR titration and fluorescence emission data.

Sensing mechanism of fluorogenic urea with fluoride in solvent media: A new fluorescence quenching mechanism

The interaction of 1-Phenyl-3-(pyren-1-yl) urea (LH) and fluoride anion (F^-) with a unique ON¹-OFF-ON² fluorescent response has been investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The hydrogen-bonding dynamics and photophysical properties of the complex LH-F, as well as its isolated receptor LH and anion form L-H₁, have been studied in detail. We demonstrate that the intermolecular hydrogen bond (N-H…F) of the complex LH-F is greatly enhanced in the electronically excited state. The nonradiative deactivation via electron transfer and internal conversion rather than excited-state intramolecular proton transfer (ESIPT) can be facilitated by the excited state hydrogen bond strengthening. The results have been cross-validated by molecular structure, electronic spectra, frontier molecular orbitals, and infrared spectra as well as hydrogen bond binding energy. These results indicate that the current calculations completely reproduce the experimental results and provide compelling evidence for the sensing mechanism of LH for F^-.

Studies of cyanomethylcarbamoyl-bridged anthracene and pyrene fluorophores

Cyanomethylcarbamoyl-bridged anthracene and pyrene derivatives were prepared as functional fluorophores with diverse structural, electronic, and fluorescence properties.

Ratiometric sensing of fluoride ions using Raman spectroscopy

Ratiometric Raman spectroscopy represents a novel sensing approach for the detection of fluoride anions based on alkyne desilylation chemistry. This method enables rapid, anion selective and highly sensitive detection of fluoride in a simple paper-based assay format using a portable Raman spectrometer.

Cyanide Sensing in Water Using a Copper Metallogel through "Turn-on" Fluorescence

The development of fluorescent probes for selective detection of cyanide has gained considerable attention over the past two decades due to benefits like high selectivity as well as sensitivity, fast response, visual output, accurate quantification, and a simplified sample preparation procedure. However, the propensity of supramolecular gels toward fluorescence sensing of cyanide in aqueous medium is not well explored until now. Herein, we report the design and synthesis of a novel copper based metallogel capable of sensing cyanide in water by fluorescence "turn on". Toward this, a terpyridine attached poly(aryl ether) dendrone derivative (G1) is synthesized which forms gel and exhibits Aggregation Induced Emission (AIE). The addition and diffusion of copper ions to the gel resulted in the formation of a nonluminescent copper metallogel (CuG). The copper metallogel could selectively sense cyanide in water by a fluorescence "turn-on" signal due to the regeneration of the AIE active gel. The mechanistic pathways of the sensing have been studied, and the detection limit for sensing was found to be as low as 1.09 μM. A thin film of CuG was prepared by casting the gel and used as a test strip for the visual detection of cyanide in water.

The Spectrophotometric Characteristic of Immunoglobulin Conjugates for Diagnostics of Causative Agents of Especially Dangerous Infections

The possibility of characterizing fluorescent immunoglobulins using spectrophotometric analysis as a testing method is considered. The comparative analysis of optical properties of fluorescent immunoglobulin preparations and their components-immunoglobulins and fluorochrome-is carried out. The obtained results testify that the proposed methodological approach of optical detection of labeled immunoglobulin molecules can be promising for tests on obtaining conjugates used in immunological tests on revealing specific antigens of causative agents of especially dangerous infections.

Fluorescence "Turn On-Off" Sensing of Copper (II) Ions Utilizing Coumarin-Based Chemosensor: Experimental Study, Theoretical Calculation, Mineral and Drinking Water Analysis

Herein, we report the preparation of a fluorescent sensor based on coumarin derivative for copper (II) ion sensing in CH₃CN/HEPES media. 6,7-dihydroxy-3-(4-(trifluoro)methylphenyl)coumarin (HMAC) sensor was fabricated and analyzed by spectroscopic techniques. The sensor demonstrates "turn on-off" fluorescence quenching in the presence of copper (II) ions at 458 nm. A clear complex between the chemosensor HMAC and copper (II) ions was characterized by ESI-MS as well as the Job's method. Also, the limit of detection (LOD, 3σ/k) value was determined as 24.5 nM in CH₃CN/HEPES (95/5, v/v) buffer media (pH = 7.0). This value is lower than the admissible level of copper (II) ions in drinking water (maximum 31.5 μM) reported by EU Water Framework Directive (WFD) and World Health Organization (WHO) guidelines. The theoretical calculations (density functional theory, DFT) have been performed for the geometric optimized structures. As a final stage, real sample analyses have successfully been performed by using HMAC, as well as ICP-OES method. The relative standard deviation for copper (II) in mineral and drinking water samples has been determined to be below 0.15% and recovery values are in the range of 95.48-109.20%.

Application of Boroisoquinoline Fluorophores as Chemodosimeters for Fluoride Ion and Pd (0)

The development of novel chemodosimeters is currently a prosperous field in organic chemistry. Recently, a new family of fluorophores, the boroisoquinolines, were introduced with satisfying photophysical properties. As a continuation of this research, the application of boroisoquinolines is presented as chemodosimeters for fluoride anion and Pd (0). The new tools showed good selectivity for the detection of the analytes. Moreover, the mechanism of action was investigated experimentally.

A novel bifunctional fluorescent and colorimetric probe for detection of mercury and fluoride ions

A fluorescent and colorimetric probe L1 based on a simple coumarin derivative for detection of Hg²⁺ and F^- ions was developed. Upon addition of Hg²⁺ and F^- ions, L1 underwent desulfurization and desilylation, respectively, to induce marked increase in the fluorescence intensity and sharp color change from light yellow to dark purple and light brown, respectively. Probe L1 could be used for sensing and for quantitative measurement of Hg²⁺ and F^- ions by both UV-vis and fluorescence spectra. The bifunctional probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range.

A novel hydroxyl-containing polyimide as a colorimetric and ratiometric chemosensor for the reversible detection of fluoride ions

A novel hydroxyl-containing polyimide film has been designed and fabricated as a chemosensor for the real-time visualization of F⁻ with high selectivity and sensitivity.

Synthesis of 3,5-Disubstituted BODIPYs Bearing N-Containing Five-Membered Heteroaryl Groups via Nucleophilic C-N Bond Formation

Aromatic substitution reactions were applied to the divergent synthesis of a series of symmetrically and unsymmetrically 3,5-disubstituted BODIPYs bearing N-heteroaryl groups. Furthermore, the effect of N-heteroaryl substituents at the 3- and 5-positions on the optical and photophysical properties of the BODIPY π-electron system was elucidated.

A Cu(ii) mediated approach for colorimetric detection of aqueous fluoride in ppm level with a Schiff base receptor

Inspired by the importance of fluoride detection in aqueous environment, a new methodology is demonstrated by employing the synergistic reaction of fluoride and Cu(ii) salts with a designed Schiff base receptor.

ESIPT-capable 2,6-di(1H-imidazol-2-yl)phenols with very strong fluorescent sensing signals towards Cr(iii), Zn(ii), and Cd(ii): molecular variation effects on turn-on efficiency

The derivatization influence was studied for twelve 2,6-di(1H-imidazol-2-yl)phenols, whereby a strong fluorescent sensitivity for Cr(iii) was reported, while Zn(ii)/Cd(ii) sensing potentials also appeared.

Green and Red Fluorescent Dyes for Translational Applications in Imaging and Sensing Analytes: A Dual-Color Flag

Red and green are two of the most-preferred colors from the entire chromatic spectrum, and red and green dyes are widely used in biochemistry, immunohistochemistry, immune-staining, and nanochemistry applications. Selective dyes with green and red excitable chromophores can be used in biological environments, such as tissues and cells, and can be irradiated with visible light without cell damage. This critical review, covering a period of five years, provides an overview of the most-relevant results on the use of red and green fluorescent dyes in the fields of bio-, chemo- and nanoscience. The review focuses on fluorescent dyes containing chromophores such as fluorescein, rhodamine, cyanine, boron-dipyrromethene (BODIPY), 7-nitobenz-2-oxa-1,3-diazole-4-yl, naphthalimide, acridine orange, perylene diimides, coumarins, rosamine, Nile red, naphthalene diimide, distyrylpyridinium, benzophosphole P-oxide, benzoresorufins, and tetrapyrrolic macrocycles. Metal complexes and nanomaterials with these dyes are also discussed.