Sugar-phosphole oxide conjugates as "turn-on" luminescent sensors for lectins

Detection of Lectin Protein Allergen of Kidney Beans (Phaseolus vulgaris L.) and Desensitization Food Processing Technology

With the increase of food allergy events related to not properly cooked kidney beans (Phaseolus vulgaris L.), more and more researchers are paying attention to the sensitization potential of lectin, one of the major storage and defensive proteins with the specific carbohydrate-binding activity. The immunoglobulin E (IgE), non-IgE, and mixed allergic reactions induced by the lectins were inducted in the current paper, and the detection methods of kidney bean lectin, including the purification strategies, hemagglutination activity, specific polysaccharide or glycoprotein interactions, antibody combinations, mass spectrometry methods, and allergomics strategies, were summarized, while various food processing aspects, such as the physical thermal processing, physical non-thermal processing, chemical modifications, and biological treatments, were reviewed in the potential of sensitization reduction. It might be the first comprehensive review on lectin allergen detection from kidney bean and the desensitization strategy in food processing and will provide a basis for food safety control.

Aggregation-Induced Emission and White Luminescence from a Combination of π-Conjugated Donor-Acceptor Organic Luminogens

Two new star-shaped phenyl- and triazine-core based donor-acceptor (D-A) type conjugated molecules bearing triphenylamine end-capped arms were synthesized and characterized as imminent organic optoelectronic materials. Photophysical properties of the compounds were explored systematically via spectroscopic and theoretical methods. Because of the presence of donor-acceptor interactions, these luminogens display multifunctional properties, for instance, high extinction coefficient, large stokes shift, and pronounced solvatochromic effect. The compounds also exhibited phenomenon known as aggregation-induced emission on formation of nano-aggregates in the tetrahydrofuran-water mixture. The aggregate formation was confirmed by transmission electron microscopy, scanning electron microscopy, and dynamic light scattering analyses. Moreover, by controlling the electron withdrawing ability of the acceptor, complementary emissive fluorophores (blue and yellow) were achieved. These two complementary colors together span the entire range of visible spectrum (400-800 nm) and therefore when mixed in a requisite proportion generate white light in solution phase. These findings have potential for the progress of new organic white light radiating materials for applications in lighting and display devices.

Progress and Trends in AIE-Based Bioprobes: A Brief Overview

Luminescent bioprobes are powerful analytical means for biosensing and optical imaging. Luminogens featured with aggregation-induced emission (AIE) attributes have emerged as ideal building blocks for high-performance bioprobes. Bioprobes constructed with AIE luminogens have been identified to be a novel class of FL light-up probing tools. In contrast to conventional bioprobes based on the luminophores with aggregation-caused quenching (ACQ) effect, the AIE-based bioprobes enjoy diverse superiorities, such as lower background, higher signal-to-noise ratio and sensitivity, better accuracy, and more outstanding resistance to photobleaching. AIE-based bioprobes have been tailored for a vast variety of purposes ranging from biospecies sensing to bioimaging to theranostics (i.e., image-guided therapies). In this review, recent five years' advances in AIE-based bioprobes are briefly overviewed in a perspective distinct from other reviews, focusing on the most appealing trends and progresses in this flourishing research field. There are altogether 11 trends outlined, which have been classified into four aspects: the probe composition and form (bioconjugtes, nanoprobes), the output signal of probe (far-red/near-infrared luminescence, two/three-photon excited fluorescence, phosphorescence), the modality and functionality of probing system (dual-modality, dual/multifunctionality), the probing object and application outlet (specific organelles, cancer cells, bacteria, real samples). Typical examples of each trend are presented and specifically demonstrated. Some important prospects and challenges are pointed out as well in the hope of intriguing more interests from researchers working in diverse areas into this exciting research field.

Glycodendron–rhenium complexes as luminescent probes for lectin sensing

Enhanced emission intensity of novel Re(i)-glycoprobes resulting from the specific recognition of carbohydrate-binding proteins as a potential tool in bioimaging applications.

Aggregation-Induced Emission Probe for Specific Turn-On Quantification of Soluble Transferrin Receptor: An Important Disease Marker for Iron Deficiency Anemia and Kidney Diseases

Transferrin receptor (TfR) is overexpressed on the surface of many cancer cells due to its vital roles in iron circulation and cellular respiration. Soluble transferrin receptor (sTfR), a truncated extracellular form of TfR in serum, is an important marker of iron deficiency anemia (IDA) and bone marrow failure in cancer patients. More recently, sTfR level in urine has been related to a specific kidney disease of Henoch-Schönlein purpura nephritis (HSPN). Despite the universal significance of sTfR, there is still a lack of a simple and sensitive method for the quantification of sTfR. Furthermore, it is desirable to have a probe that can detect both TfR and sTfR for further comparison study. In this work, we developed a water-soluble AIE-peptide conjugate with aggregation-induced emission (AIE) characteristics. Taking advantage of the negligible emission from molecularly dissolved tetraphenylethene (TPE), probe TPE-2T7 was used for the light-up detection of sTfR. The probe itself is nonemissive in aqueous solution, but it turns on its fluorescence upon interaction with sTfR to yield a detection limit of 0.27 μg/mL, which is much lower than the sTfR level in IDA patients. Furthermore, a proof-of-concept experiment validates the potential of the probe for diagnosis of HSPN by urine test.

Wettability with Aggregation-Induced Emission Luminogens

Aggregation-induced emission luminogens (AIEgens) have become an emerging field since the concept of AIE was proposed in 2001. Recently, AIEgens have attracted considerable attention due to their abnormal non-emissive fluorescent behavior in solution but strongly emissive behavior in the aggregate state. By utilizing the inherent hydrophobicity, AIEgens can be used to monitor the crystal formation and dewetting behavior in the self-assembly process. More importantly, some stimuli-responsive AIE-active surfaces have been successfully fabricated. In this perspective review, we outline the advances of surface wettability of AIEgens and its applications.

A novel aggregation-induced emission platform from 2,3-diphenylbenzo[b]thiophene S,S-dioxide

The steric hindrance and electronic push–pull effect greatly influence the aggregation-induced emission (AIE) properties of 2,3-diphenylbenzo[b]thiophene S,S-dioxide.

Agglutination of bacteria using polyvalent nanoparticles of aggregation-induced emissive thiophthalonitrile dyes

A novel class of aggregation-induced emissive bis(phenylthio)phthalonitrile dyes were synthesized. These dyes assembled into nanoparticles that were equipped with mannose units. The nanoparticles underwent selective interactions with lectins and bacteria. The bright fluorescent aggregates aid in the visualization of the agglutination of bacteria.

pH-Regulated Reversible Transition Between Polyion Complexes (PIC) and Hydrogen-Bonding Complexes (HBC) with Tunable Aggregation-Induced Emission

The mimicking of biological supramolecular interactions and their mutual transitions to fabricate intelligent artificial systems has been of increasing interest. Herein, we report the fabrication of supramolecular micellar nanoparticles consisting of quaternized poly(ethylene oxide)-b-poly(2-dimethylaminoethyl methacrylate) (PEO-b-PQDMA) and tetrakis(4-carboxylmethoxyphenyl)ethene (TPE-4COOH), which was capable of reversible transition between polyion complexes (PIC) and hydrogen bonding complexes (HBC) with tunable aggregation-induced emission (AIE) mediated by solution pH. At pH 8, TPE-4COOH chromophores can be directly dissolved in aqueous milieu without evident fluorescence emission. However, upon mixing with PEO-b-PQDMA, polyion complexes were formed by taking advantage of electrostatic interaction between carboxylate anions and quaternary ammonium cations and the most compact PIC micelles were achieved at the isoelectric point (i.e., [QDMA(+)]/[COO(-)] = 1), as confirmed by dynamic light scattering (DLS) measurement. Simultaneously, fluorescence spectroscopy revealed an evident emission turn-on and the maximum fluorescence intensity was observed near the isoelectric point due to the restriction of intramolecular rotation of TPE moieties within the PIC cores. The kinetic study supported a micelle fusion/fission mechanism on the formation of PIC micelles at varying charge ratios, exhibiting a quick time constant (τ1) relating to the formation of quasi-equilibrium micelles and a slow time constant (τ2) corresponding to the formation of final equilibrium micelles. Upon deceasing the pH of PIC micelles from 8 to 2 at the [QDMA(+)]/[COO(-)] molar ratio of 1, TPE-4COOH chromophores became gradually protonated and hydrophobic. The size of micellar nanoparticles underwent a remarkable decrease, whereas the fluorescence intensity exhibited a further increase by approximately 7.35-fold, presumably because of the formation of HBC micelles comprising cationic PQDMA coronas and PEO/TPE-4COOH hydrogen-bonded cores, an inverted micellar structures compared to initial PIC micelles. Moreover, the pH-mediated schizophrenic micellar transition from PIC to HBC with tunable AIE characteristic was reversible.

Stimuli-responsive chromism in organophosphorus chemistry

The last five years have seen a huge advance in organophosphorus chemistry with respect to compounds with strong chromic responses to external stimuli. This Frontier article briefly summarizes these trends in order to especially highlight the broad versatility of phosphole-based scaffolds in chromic materials.

Carbohydrates in Supramolecular Chemistry

Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed.

Aggregation-induced emission of siloles

Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure-property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.

Modulation of aggregation-induced emission and electroluminescence of silole derivatives by a covalent bonding pattern

The deciphering of structure-property relationships is of high importance to rational design of functional molecules and to explore their potential applications. In this work, a series of silole derivatives substituted with benzo[b]thiophene (BT) at the 2,5-positions of the silole ring are synthesized and characterized. The experimental investigation reveals that the covalent bonding through the 2-position of BT (2-BT) with silole ring allows a better conjugation of the backbone than that achieved though the 5-position of BT (5-BT), and results in totally different emission behaviors. The silole derivatives with 5-BT groups are weakly fluorescent in solutions, but are induced to emit intensely in aggregates, presenting excellent aggregation-induced emission (AIE) characteristics. Those with 2-BT groups can fluoresce more strongly in solutions, but no obvious emission enhancements are found in aggregates, suggesting they are not AIE-active. Theoretical calculations disclose that the good conjugation lowers the rotational motions of BT groups, which enables the molecules to emit more efficiently in solutions. But the well-conjugated planar backbone is prone to form strong intermoelcular interactions in aggregates, which decreases the emission efficiency. Non-doped organic light-emitting diodes (OLEDs) are fabricated by using these siloles as emitters. AIE-active silole derivatives show much better elecroluminescence properties than those without the AIE characterisic, demonstrating the advantage of AIE-active emitters in OLED applications.

Amphiphilic benzothiadiazole–triphenylamine-based aggregates that emit red light in water

An amphiphilic donor–acceptor dye can provide red light emission in water in an aggregate state.

2,5-difluorenyl-substituted siloles for the fabrication of high-performance yellow organic light-emitting diodes

2,3,4,5-Tetraarylsiloles are a class of important luminogenic materials with efficient solid-state emission and excellent electron-transport capacity. However, those exhibiting outstanding electroluminescence properties are still rare. In this work, bulky 9,9-dimethylfluorenyl, 9,9-diphenylfluorenyl, and 9,9'-spirobifluorenyl substituents were introduced into the 2,5-positions of silole rings. The resulting 2,5-difluorenyl-substituted siloles are thermally stable and have low-lying LUMO energy levels. Crystallographic analysis revealed that intramolecular π-π interactions are prone to form between 9,9'-spirobifluorene units and phenyl rings at the 3,4-positions of the silole ring. In the solution state, these new siloles show weak blue and green emission bands, arising from the fluorenyl groups and silole rings with a certain extension of π conjugation, respectively. With increasing substituent volume, intramolecular rotation is decreased, and thus the emissions of the present siloles gradually improved and they showed higher fluorescence quantum yields (Φ(F) =2.5-5.4%) than 2,3,4,5-tetraphenylsiloles. They are highly emissive in solid films, with dominant green to yellow emissions and good solid-state Φ(F) values (75-88%). Efficient organic light-emitting diodes were fabricated by adopting them as host emitters and gave high luminance, current efficiency, and power efficiency of up to 44,100 cd m(-2), 18.3 cd A(-1), and 15.7 lm W(-1), respectively. Notably, a maximum external quantum efficiency of 5.5% was achieved in an optimized device.

Enhancing the visualization of latent fingerprints by aggregation induced emission of siloles

Aggregation-induced emission was explored for the visual enhancement of latent fingerprints deposited on wet non-porous surfaces.

Electrogenerated poly(pyrrole-lactosyl) and poly(pyrrole-3'-sialyllactosyl) interfaces: toward the impedimetric detection of lectins

This paper reports on the impedimetric transduction of binding reaction between polymerized saccharides and target lectins. The controlled potential electro-oxidation of pyrrole-lactosyl and pyrrole-3'-sialyllactosyl at 0.95 V vs. Ag/AgCl, provides thin and reproducible poly(pyrrole-saccharide) films. The affinity binding of two lectins: Arachis hypogaea, (PNA) and Maackia amurensis (MAA) onto poly(pyrrole-lactosyl) and poly(pyrrole-3'-sialyllactosyl) electrodes, was demonstrated by cyclic voltammetry in presence of ruthenium hexamine and hydroquinone. In addition, rotating disk experiments were carried out to determine the permeability of both polypyrrole films and its evolution after incubating with lectin target. Finally, the possibility of using the poly(pyrrole-lactosyl) or poly(pyrrole-3'-siallyllactosyl) films for the impedimetric transduction of the lectin binding reaction, was investigated with hydroquinone (2 × 10(-3) mol L(-1)) as a redox probe in phosphate buffer. The resulting impedance spectra were interpreted and modeled as an equivalent circuit indicating that charge transfer resistance (R ct) and relaxation frequency (f°) parameters are sensitive to the lectin binding. R ct increases from 77 to 97 Ω cm(2) for PNA binding and from 93 to 131 Ω cm(2) for MAA binding. In parallel, f° decreases from 276 to 222 Hz for PNA binding and from 223 to 131 Hz for MAA binding. This evolution of both parameters reflects the steric hindrances generated by the immobilized lectins towards the permeation of the redox probe.

Multivalent glycoconjugate syntheses and applications using aromatic scaffolds

Glycan-protein interactions are of utmost importance in several biological phenomena. Although the variety of carbohydrate residues in mammalian cells is limited to less than a dozen different sugars, their spatial topographical presentation in what is now associated as the "glycocodes" provides the fundamental keys for specific and high affinity "lock-in" recognition events associated with a wide range of pathologies. Toward deciphering our understanding of these glycocodes, chemists have developed new creative tools that included dendrimer chemistry in order to provide monodisperse multivalent glycoconjugates. This review provides a survey of the numerous aromatic architectures generated for the multivalent presentation of relevant carbohydrates using covalent attachment or supramolecular self-assemblies. The basic concepts toward their controlled syntheses will be described using modern synthetic procedures with a particular emphasis on powerful organometallic methodologies. The large variety of dendritic aromatic scaffolds, together with a brief survey of their unique biophysical and biological properties will be critically reviewed. The distinctiveness of the resulting multivalent glycoarchitectures, encompassing glycoclusters, glycodendrimers and molecularly defined self-assemblies, in forming well organized cross-linked lattices with multivalent carbohydrate binding proteins (lectins) together with their photophysical, medical, and imaging properties will also be briefly highlighted. The topic will be presented in increasing order of aromatic backbone complexities and will end with fullerenes together with self-assembled nanostructures, thus complementing the various scaffolds described in this special thematic issue dedicated to multivalent glycoscience.

One-step preparation of fluorescent inorganic–organic hybrid material used for explosive sensing

As a fluorescent inorganic–organic hybrid polymer, TPE-CP is prepared through one-step polycondensation and used for explosive sensing.

Development of tetraphenylethylene-based fluorescent oligosaccharide probes for detection of influenza virus

Tetraphenylethylene (TPE) derivatives have strong fluorescence in aggregated state. We designed and synthesized a tetraphenylethylene derivative bearing alkyne groups which were used for combination by click chemistry. The new TPE compound bearing alkyne groups was used to synthesize fluorescence oligosaccharide probes which have lactosyl and 6′-sialyllactosyl moieties as ligands. We found that the TPE compounds bearing lactosyl and 6′-sialyllactosyl moieties were useful for detection of RCA120 and SSA lectins, respectively. Moreover, we have shown that TPE-based fluorescent oligosaccharide probe bearing 6′-sialyllactose moiety can be utilized as a “turn-on” fluorescent sensor for detection of influenza virus.