Bifunctional Fluorescent Calix[4]arene Chemosensor for Both a Cation and an Anion

Importance of BODIPY-based Chemosensors for Cations and Anions in Bio-imaging Applications

Background:

Chemosensor compounds are useful for sensitive selective detection of cations and anions with fluorophore groups in an attempt to develop the effective selectivity of the sensors. Although familiar fluorescent sensors utilizing inter-molecular interactions with the cations and anions, an extraordinary endeavor was executed the preparation of fluorescent-based sensor compounds. 4,4-difluoro-4- bora-3a,4a-diaza-s-indacene (Bodipy) and its derivatives were firstly used as an agent in the imaging of biomolecules due to their interesting structures, complexation, and fluorogenic properties. Among the fluorescent chemosensors used for cations and anions, Bodipy-based probes stand out owing to the excellent properties such as sharp emission profile, high stability, etc. In this review, we emphasize the Bodipy-based chemosensor compounds, which have been used to image cations and anions in living cells, because of as well as the biocompatibility and spectroscopic properties.

Methods:

Research and online content related to chemosensor online activity is reviewed. The advances, sensing mechanisms and design strategies of the fluorophore exploiting selective detection of some cation and anions with Bodipy-based chemosensors are explained. It could be claimed that the using of Bodipy-based chemosensors is very important for cations and anions in bio-imaging applications.

Results:

Molecular sensors or chemosensors are molecules that show a change can be detected when affected by the analyte. They are capable of producing a measurable signal when they are selective for a particular molecule. Molecular and ion recognition that it is important in biological systems such as enzymes, genes, environment, and chemical fields. Due to the toxic properties of many heavy metal ions, it is of great importance to identify these metals due to their harmful effects on living metabolism and the pollution they create in the environment. This process can be performed with analytical methods based on atomic absorption and emission. The fluorescence methods among chemosensor systems have many advantages such as sensitivity, selectivity, low price, simplicity of using the instrument and direct determination in solutions. The fluorescence studies can be applied at nanomolar concentrations.

Conclusion:

During a few decades, a lot of Bodipy-based chemosensors for the detection of cations & anions have been investigated in bio-imaging applications. For the Bodipy-based fluorescent chemosensors, the Bodipy derivatives were prepared by different ligand groups for the illumination of the photophysical and photochemical properties. The synthesized Bodipy-based chemosensors have remarkable photophysical properties, such as a high quantum yield, strong molar absorption coefficient etc. Moreover, these chemosensors were successfully implemented on living organisms for the detection of analytes.

Dual-channel recognition of Al3+ and Cu2+ ions using a chiral pyrene-based fluorescent sensor

Specific recognition between Al3+ and Cu2+ has been achieved based on the new mechanism of Cu2+ detection by pyrene dimerization.

Synthesis of new anthracene-substituted calix[4]triazacrown-5 as highly sensitive fluorescent chemosensor and extractant against hazardous dichromate anion

A new fluorogenic anthracene functionalized calix[4]triazacrown-5 (Ant-AzClx) was successfully synthesized using a simple Schiff's base reaction. The ¹ H-NMR, ¹³ C-NMR, ESI-MS, and elemental analysis techniques were performed to characterize its structure. Excited at 370 nm, Ant-AzClx reveals excimer emission at 418 nm. Therefore, its anion binding properties were investigated against F^- , HCO₃ ^- , H₂ PO₄ ^- , NO₃ ^- , Cr₂ O₇ ^2- , and SO₄ ^2- ions. When hazardous dichromate anion was introduced into medium, the fluorescence intensity of Ant-AzClx was markedly quenched. The binding constant, stoichiometry, the detection limits and Stern-Volmer equation for the complex formed between Ant-AzClx and Cr₂ O₇ ^2- ion were determined. Furthermore, the ¹ H-NMR technique was also performed to assess the mechanism of the complex (Ant-AzClx@Cr₂ O₇ ^2- ). Apart from its excellent fluorescent chemosensor properties for selective and sensitive recognition of Cr₂ O₇ ^2- ion, Ant-AzClx was used as an efficient extractant towards dichromate anion. The extraction results indicated that Ant-AzClx exhibited high extraction capability, leading to it being a promising extractant for the removal of dichromate anions from water.

Colorimetric and fluorimetric chemosensor based on upper rim-functionalized calix[4]arene for selective detection of fluoride ion

A new colorimetric and fluorescent chemosensor for fluoride anion based on calix [4]arene bearing four sulfonamide-fluorenone subunits on the upper rim was conveniently synthesized. It showed a remarkable color change as well as the fluorescence quenching upon addition of F^- even in the presence of a wide range of anions in DMSO. The binding property of L with F^- was studied by a combination of various spectroscopic techniques, such as absorption and emission titration, Job's plot and ¹H NMR titration. It is anticipated that this design with functional group attached to upper rim of calix[4]arene platform can provide a new approach for the development of F^- chemosensor.

Fluorescent molecular rotors as sensors for the detection of thymidine phosphorylase

Three new fluorescent molecular rotors were synthesized with the aim of using them as sensors to dose thymidine phosphorylase, one of the target enzymes of 5-fluorouracil, a potent chemotherapic drug largely used in the treatment of many solid tumors, that acts by hindering the metabolism of pyrimidines. 5-Fluorouracil has a very narrowtherapeutic window, in fact, its optimal dosage is strictly related to the level of its target enzymes that vary significantly among patients, and it would be of the utmost importance to have an easy and fast method to detect and quantify them. The three molecular rotors developed as TP sensors differ in the length of the alkylic spacer joining the ligand unit, a thymine moiety, and the fluorescent molecular rotor, a [4-(1-dimethylamino)phenyl]-pyridinium bromide. Their ability to trigger an optical signal upon the interaction with thymidine phosphorylase was investigated by fluorescent measurements.

A solid-state colorimetric fluorescence Pb2+-sensing scheme: mechanically-driven CsPbBr3 nanocrystallization in glass

Highly toxic Pb2+ poses a great threat to the health of human beings and ecosystems, urgently calling for an efficient Pb2+ detection method. Herein, we demonstrated a brand-new solid-state fluorescence Pb2+-sensing scheme based on a type of Pb2+-responsive borate glass powder that is able to precipitate CsPbBr3 nanocrystals on the glass surface upon grinding with Pb2+ sources, following a mechanically driven glass crystallization mechanism. Pb2+ sensing is achieved via the Pb2+ concentration-dependent green emission of CsPbBr3 as an indicator signal and independent red emission of Eu3+ as a reference signal. Under UV light irradiation, the obvious emissive color variation from red to green as Pb2+ concentration varies enables the intuitive Pb2+-sensing by naked eyes. With the aid of a spectrometer and smartphone, Pb2+ concentration can be quantitatively determined with the detection limit as low as ∼70 ppm and ∼400 ppm, respectively. The semi-quantitative Pb2+ detection is also possible by comparing the emissive color with the calibrated color card. Hopefully, the proposed solid-state fluorescence Pb2+-sensing strategy with high selectivity can be used for portable and quick Pb2+ analysis in daily life.

Stimulus-Responsive Supramolecular Host-Guest Assembly of a Cationic Pyrene Derivative with Sulfated β-Cyclodextrin

In general, aggregation-prone organic molecules are prevented from self-aggregation in the presence of macrocyclic hosts like β-cyclodextrin because of their preference for the formation of inclusion complex with guest molecules. On the contrary, sulfate-laced β-cyclodextrin has been recently reported to induce the aggregation of some of the non-aggregation-prone organic dyes, which have been subsequently utilized for biosensing applications. In the present contribution, we report the interaction of a cationic organic probe molecule, 1-pyrene methyl amine (PMA), which belongs to one of the most useful families of organic fluorescent probes, that is, pyrene, with a sulfated β-cyclodextrin derivative (SCD). Interaction of a cationic probe with a β-cyclodextrin derivative was studied using a variety of photophysical methods such as ground-state absorption, steady-state emission, and time-resolved emission techniques. Detailed photophysical investigations have revealed that SCD induces the ground-state association of PMA molecules. This SCD-induced aggregation of PMA molecules has been attributed to the charge neutralization of the cationic probe by negatively charged sulfate groups, which subsequently lead to their association because of the close proximity on the rims of cyclodextrin. This monomer-dimer equilibrium of the PMA-SCD system is found to be extremely responsive to external chemical stimuli like temperature, pH, ionic strength of the medium, and organic solvent (dimethyl sulfoxide), which projects them as potential platforms for various sensing applications including bioanalytes. The supramolecular assembly has been demonstrated to sense arginine.

Substituent effect on colorimetric detection of biologically and environmentally relevant anions: Insight in real-life applications

A new set of chromogenic anion receptors R1-R4 have been synthesized with a different substituent, including electron withdrawing (nitro moiety in R1), conjugated group (naphthyl in R2), and electron donating (methyl in R3), respectively. The receptors R1-R4 exhibited very good sensitivity towards the F^- and AcO^- anions in the DMSO. In addition, R1 showed selectivity towards H₂PO₄^- ions over other tested anions. R1 especially acted as an effective sensor for sodium salts of F^-, AcO^-, AsO₂^-, and AsO₄^2- ions in an aqueous medium due to the presence of two electron-withdrawing nitro substituents, which showed hydrogen bond donor tendency and acidity of the OH proton. This result indicates that R1 is highly capable of competing with an aqueous medium to detect anions without counter Na⁺ ion interference. Interestingly, R1 displays solvatochromic property in the presence of AcO^- ions in different aprotic solvents. Additionally, the receptor R1 shows high binding affinity towards AcO^- ions in the buffer medium (DMSO: HEPES, 9:1 v/v), which displayed remarkable colour change from pale yellow to blue with a large ∆λ_{red shift} of 170 nm. The CV studies reveal the deprotonation of the -NH proton upon interaction with the AcO^- ions. The receptor R1 is subjected to practical application to sense F^- and AsO₂^- ions using the test strip. In addition, the receptor R1 proves itself as a potential applicant for the detection of F^- ions quantitatively in commercially available mouthwash.

Visual detection of fluoride ion based on ICT mechanism

A novel chemosensor (H₃NTS) has been designed for a fast and accurate detection of F^- in acetonitrile medium. The UV-Vis, ¹H, ¹³C NMR experiments and computational calculations demonstrate that H₃NTS probe offers a potential colorimetric sensor for discriminating F^- among other relevant anions. The detection limit is as low as 6 μM and a reversible colorimetric switch could be devised by sequential addition of F^-/Ca²⁺. The promising application of H₃NTS is also confirmed in real examples where the concentration of F^- is a critical parameter, e.g., commercial toothpaste, paper strip and gel form analysis of samples.

Simultaneous dual-colour tracking lipid droplets and lysosomes dynamics using a fluorescent probe

After entering a cell, most small molecule fluorescent probes are dispersed in the cytoplasm before they then accumulate in a specific organelle or subcellular zone. Molecules that can enter two or more organelles with high selectivity are all but unknown. In this work, we report a naphthalimide-based fluorescent probe, NIM-7, that allows lipid droplets and lysosomes to be labelled simultaneously and with high specificity. These subcellular entities can then be visualized readily through yellow and red fluorescence, using different excitation and detection channels. NIM-7 allows 3D imaging and quantitative visualizing of lipid droplets and lysosomes. It is also able to track simultaneously the movement of lipid droplets and lysosomes in real-time. We also report here that NIM-7 can be used to image both different cell lines and zebrafish embryos.

Cyanide Toxicity of Freshly Prepared Smoothies and Juices Frequently Consumed

AIMS

This study was conducted to detect the presence of cyanide in popular fruit and vegetable smoothies and juices marketed as raw and natural.

STUDY DESIGN

Eleven (11) popular varieties of drinks were analyzed for total cyanide (TCN). Drinks contained raw vegetables and fruits, flax seeds, whole apples with seeds, raw almond milk, and pasteurized almond milk as ingredients.

PLACE AND STUDY DURATION

Samples were collected from health food eateries located within Las Vegas, Nevada (USA) during the summer of 2017.

METHODOLOGY

Fifty milliliters (mL) of a homogenized smoothie and juice drink and 1 gram of flax seeds were subjected to the above-referenced methods for sample preparation per USEPA Methods 9012B (digestion) followed by USEPA method 9014 (colorimetry).

RESULTS

The highest TCN was detected in drinks containing raw flax seed followed by unpasteurized raw almond milk, then fresh whole apple juice. No TCN was observed in drinks that contained none of the above mentioned items (e.g. flax seed, raw almond milk) or those utilizing pasteurized ingredients.

CONCLUSION

This study observed that TCN is present in smoothies and juices containing raw flax seeds, fresh whole apples, and/or unpasteurized almond milk. Concentrations were detected as high as 341 μg L-1 in commercially available smoothies containing vegetables, raw flax seeds, almond milk and fruits. Smoothies with vegetables, fruits, unpasteurized almond milk, and no flax seeds contained 41 ug L-1 TCN, while similar smoothies with pasteurized almond milk contained negligible to 9.6 ug L-1 CN-. Unpasteurized almond milk and raw flax seeds were the major sources of TCN in drinks. With the increased demand for raw and natural foods, there is a potential sublethal exposure of TCN by consumers.

A Cr(VI) selective probe based on a quinoline-amide calix[4]arene

A new quinoline-amide calix[4]arene 3-receptor for detection of hazardous anions and cations have been synthesized. The 3-receptor was examined for its sensing properties towards several different anions (Cr₂O₇^2-, SCN^-, F^-, Cl^-, NO₃^-) and metal ions (Hg²⁺, Cd²⁺, Ag⁺) by UV-vis and fluorescence spectroscopies. It was detected that the 3-receptor has only sensing ability for Cr₂O₇^2- and Hg²⁺ ions, resulting in the association constants higher for Cr₂O₇^2- than to the Hg²⁺ ions. High selectivity towards Cr₂O₇^2- were also observed by fluorescence measurement among other ions (F^-, Cl^-_, SCN^-, Hg²⁺, Cd²⁺, Ag⁺) with a low limit of detection (7.36×10^-6moldm^-3). Proton NMR anion-binding investigations revealed a strong interaction of Cr₂O₇^2- anion with NH and CH groups of the receptor, showing that the combination with hydrogen-bonds donor groups strengthened the anion receptor association. Furthermore, remarkable association constants for dichromate anion obtained by all techniques strongly suggest the 3-receptor as a selective Cr(VI) sensor.

Reaction-based ratiometric fluorescent probe for selective recognition of sulfide anions with a large Stokes shift through switching on ESIPT

Ratiometric fluorescent probe BNPT has been synthesized and characterized for S²⁻ sensing via ESIPT mechanism.

Chromogenic and fluorogenic multianalyte detection with a tuned receptor: refining selectivity for toxic anions and nerve agents

In the present study, a chemical probe was finely tuned for the highly selective and sensitive chromogenic and fluorogenic detection of toxic anions and a nerve agent.

A new dual fluorogenic and chromogenic "turn-on" chemosensor for Cu²⁺/F⁻ ions

Turn "off-on" chemosensor 2-(-2-((3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthen]-2-yl)imino)ethylidene)-N-phenylhydrazine-1-carbothioamide (RBS) was designed and synthesized. Using the naked eye, RBS showed favorable observation characteristics with both Cu(2+) and F(-) ions. The various modes of sensitivity shown by RBS toward the Cu(2+) and F(-) ions were investigated by spectral techniques, including UV-Vis, fluorescence and (1)H NMR spectroscopy. The Job's plot indicated the formation of 1:1 complex between RBS and Cu(2+)/F(-). The binding constant of the RBS-guest(-) complexes were found to be 1.3×10(4) and 6.2×10(3)M(-1) for the RBS-Cu(2+) and RBS-F(-), respectively.

An ultrafast molecular rotor based ternary complex in a nanocavity: a potential “turn on” fluorescence sensor for the hydrocarbon chain

Formation of a ternary complex by an ultrafast molecular rotor (UMR) with a macrocyclic cavitand has been investigated for the sensitive detection of the alkyl chain of a surfactant.

Fluorescent metal ion chemosensors via cation exchange reactions of complexes, quantum dots, and metal–organic frameworks

Overview of a new paradigm in the design of fluorescent chemosensors for detecting metal ions via cation exchange reactions of complexes, quantum dots, and metal–organic frameworks.

Calixarene-based chemosensors by means of click chemistry

Click chemistry, a new strategy for organic chemistry, has been widely used in the chemical modification of calixarenes because of its reliability, specificity, biocompatibility, and efficiency. Click-derived triazoles also play a critical role in sensing ions and molecules. This in-depth review provides an overview of calixarene-based chemosensors that incorporate click-derived triazoles, and their three characteristics (chromogenic, fluorescence, and wettability) are reviewed.

Optical sensor arrays for chemical sensing: the optoelectronic nose

A comprehensive review is presented on the development and state of the art of colorimetric and fluorometric sensor arrays. Optical arrays based on chemoresponsive colorants (dyes and nanoporous pigments) probe the chemical reactivity of analytes, rather than their physical properties. This provides a high dimensionality to chemical sensing that permits high sensitivity (often down to ppb levels), impressive discrimination among very similar analytes and exquisite fingerprinting of extremely similar mixtures over a wide range of analyte types, both in the gas and liquid phases.

Dual colorimetric sensing of mercury and iodide ions by steroidal 1,2,3-triazole-stabilized silver nanoparticles

Bile acid-based 1,2,3-triazole ligands have been synthesized, which show excellent ability to stabilize silver nanoparticles. These AgNPs have been found to exhibit highly selective dual colorimetric sensing of Hg²⁺ and I⁻ ions.

A study of allosteric binding behaviour of a 1,3-alternate thiacalix[4]arene-based receptor using fluorescence signal

The allosteric binding behaviour of a receptor L bearing a 1,3-alternate conformation based thiacalix[4]arene has been evaluated by fluorescence and ¹H NMR titration experiments.

A novel colorimetric and fluorescent sensor based on calix[4]arene possessing triphenylamine units

A novel colorimetric and fluorometric calix[4]arene probe (CTP) bearing triphenylamine units was synthesized in good yield and characterized by combination of (1)H, (13)C, APT, COSY, FTIR, HRMS, and UV-vis spectral data. Ion-binding studies of CTP were investigated in acetonitrile with a wide range of cations and anions and the recognition process was monitored by luminescence, UV-vis and (1)H NMR spectral changes. CTP exhibited naked eye detection for Hg(2+) ion. Also it showed a significant fluorescence quenching towards F(-) ion.

BINOL Macrocycle Derivatives: Synthesis of New Dinaphthyl Sulfide Aza Oxa Thia Crowns (Lariats)

In this research work, dinaphthyl sulfide diester was prepared from the reaction of 1,1′-thiobis (2-hydroxy naphthalene) and methylchloroacetate. Its aza-macrocyclic derivative was synthesized from the reaction of dinaphthyl sulfide diester and diethylenetriamine. Lariats were prepared from the reaction of chloroamides (four derivatives) and initial macrocycle. Chloroamides were synthesized from the reaction of amines (aniline, benzylamine, 8-amino quinoline and 4-amino azobenzene) and chloroacetyl chloride. All the materials were identified by IR,1H NMR,13C NMR, and mass spectroscopies, and elemental analysis.