Disappearance Of Fluorescence Research Articles

Bright ESIPT emission from 2,6-di(thiazol/oxazol/imidazol-2-yl)phenol derivatives in solution, aggregation and solid states

Most luminophores often suffer from the problem of aggregation-caused quenching (ACQ) or fluorescence disappearance in dilute solution. It is significant to bridge the gap between ACQ and AIE. In this work, a facile but effective strategy was proposed for the fabrication of always-on luminophores based on the excited state intramolecular proton transfer (ESIPT) mechanism, and six luminophores emitting bright fluorescence in solution, aggregation and solid states were synthesized from 5-tert-butyl-2-hydroxyisophthalaldehyde. All these ESIPT systems show only keto emission owing to their congested structures which block the breakage of intramolecular hydrogen bond (O–H⋯N) by solvation, and subsequently make enol emission impossible. Three of these luminophores are prone to convert into the corresponding phenolate anions emitting blue-shifted emission, which enable them to sense pH variation in the weakly basic range. Furthermore, white-light emission was achieved by combining two of them which show complementary-color fluorescence, and one of them was utilized for bioimaging of living Hela cells and the high-resolution image was obtained.

Omics-based approaches for discovering active ingredients and regulating gut microbiota of Actinidia arguta exosome-like nanoparticles.

Exosome-like nanoparticles (ELNs) are novel naturally occurring plant ultrastructures and contain unique bioactive components. However, the potential applications and biological functions of plant ELNs, especially in the context of health promotion and disease prevention, remain largely unexplored. This study aimed to explore the biological activities and functional mechanisms of Actinidia arguta-derived exosome-like nanoparticles (AAELNs). We reported the development of AAELNs, which possess particle sizes of 157.8 nm and a negative surface charge of -23.07 mV, uptaking by RAW264.7 cells, and reduction of oxidative stress by decreasing the activity of GSH-Px and T-SOD and increasing the content of MDA. Through the use of high-throughput sequencing technology, 12 known miRNA families and 23 additional miRNAs were identified in AAELNs, GO and KEGG term enrichment analysis revealed the potential of AAELNs-miRNAs in modulating neural-relevant behaviors. Additionally, LC-MS/MS analysis detected a total of 32 major lipid classes, 430 lipid subclasses, and 1345 proteins in AAELNs. Furthermore, in vivo fluorescence disappearance and in vitro fermentation experiments demonstrated that AAELNs were able to enter the colon and improve the microbial structure. These findings suggest that AAELNs could serve as nanoshuttles in food, potentially offering health-enhancing properties.

Ligilactobacillus acidipiscis YJ5 modulates the gut microbiota and produces beneficial metabolites to relieve constipation by enhancing the mucosal barrier.

Constipation is a prevalent gastrointestinal (GI) problem affecting a large number of individuals. This study aimed to investigate peristalsis-promoting potential characteristics of Ligilactobacillus acidipiscis YJ5 and the underlying molecular mechanism. The study demonstrated the relieving effect of L. acidipiscis YJ5 on constipation in both zebrafish and mouse models. L. acidipiscis YJ5 intervention significantly increased intestinal peristalsis by reducing the peak time and increasing the fluorescence disappearance rate in the zebrafish model. In the mouse model, the symptoms of constipation relief induced by L. acidipiscis YJ5 included a shortened first black stool time, an increased number of defecation particles, an accelerated propulsion rate of the small intestine, and an increase in fecal water content. L. acidipiscis YJ5 was found to reduce the expression of colonic aquaporins to normalize the colonic water transport system of constipated mice. Additionally, L. acidipiscis YJ5 reversed loperamide-induced morphological damage in the ileum and colon and increased the colonic mucosal barrier. The results of the 16S rRNA gene analysis indicated that L. acidipiscis YJ5 could reverse the structure of gut microbiota to a near-normal group, including levels of β-diversity, phylum, family, and genus. Furthermore, the fermentation supernatant of L. acidipiscis YJ5 was shown to relieve constipation, and metabolomics analysis revealed that these positive effects were related to its metabolites like malic acid and heliangin.

A novel reversible fluorescent probe for sequential detection of Al3+ and HPO42− based on caffeic acid and its applicability in cell imaging

In this work, we focused on synthesizing a new fluorescent probe HBA based on caffeic acid for detecting Al3+/HPO42− by the mode of “off-on-off”. HBA alone exhibited a weak fluorescence emission in aqueous solution. When Al3+ was added into the HBA solution, a significant green fluorescence was found at 498 nm. However, the introduction of HPO42− to the solution of [HBA-Al3+] complex induced the disappearance of green fluorescence. The detection limit of HBA was calculated as low as 41.7 nM for Al3+ and 62.1 nM for HPO42−, respectively. Probe HBA exhibited good cell-membrane penetrability and had the potential to trace Al3+/HPO42− in biological systems.

Fast Visualized Conformational Transition of Polyphenylacetylenes with Stepwise Tunable Circularly Polarized Luminescence.

Two novel poly(3,5-diamide substituted phenylacetylene)s bearing L- or D-alanine residues with a long alkyl chain were synthesized. In low polar or apolar solvents, the polymers adopted contracted cis-cisoid helix showing strong yellow fluorescence, which was transferred to stretched cis-transoid helix by adding polar solvents or decreasing temperature, accompanied with the disappearance of fluorescence. The critical conformational transition temperature could be readily tuned in a wide range by altering the content of polar solvent, and the conformational variation at molecular level could be directly read out via the change in fluorescent property. The synergistical participation of amide and ester groups in the formation of intramolecular hydrogen bonds accelerated the conformational transition rate, resulting in remarkable reduction of hysteresis. Moreover, the polymers displayed switchable CPL performance and the luminescent dissymmetry factor could be stepwise amplified by forming chiral aggregates or liquid crystalline structure. This study may open a new avenue for the development of controllable helical structure-based smart CPL materials.

A 3D multistage information encryption platform with self-erasure function based on a synergistically shape-deformable and AIE fluorescence-tunable hydrogel.

The traditional stored information is statically shown on single 2D planes, which leads to low information storage capacity and secondary information leakage without the proper handling of decrypted information. Developing a 3D multistage information encryption platform with self-erasure function is highly desirable. Here, a novel bilayer hydrogel with synergistic deformation and fluorescence color (SDFC) change is designed for 3D multistage information encryption. The bilayer hydrogel consisting of a shape-deformable hydrogel layer and a fluorescence hydrogel layer with aggregation-induced emission (AIE) properties can exhibit pH-responsive SDFC change. Fluorescence information can be ionoprinted on the fluorescent hydrogel layer based on electrostatic interactions and dynamic covalent bonds. The 2D bilayer hydrogel encoded with information can synergistically produce predesigned 3D shape configuration and enhanced background fluorescence to wrap information, which is only readable after sequential shape recovery with the disappearance of background fluorescence. Furthermore, multistage information can be further obtained by stepwise decryption due to information with differential fluorescence fading rates. The displayed information is automatically self-erased in the end, avoiding the information secondary leakage. This study paves an avenue for broadening conventional 2D single-level information encryption platforms to 3D multistage counterparts with self-erasure and multi-decryption capabilities based on SDFC change of the bilayer hydrogel.

A Versatile Tetraphenylethene Derivative Bearing Excitation Wavelength Dependent Emission, Multistate Mechanochromism, Reversible Photochromism, and Circularly Polarized Luminescence and Its Applications in Multimodal Anticounterfeiting

A Versatile Tetraphenylethene Derivative Bearing Excitation Wavelength Dependent Emission, Multistate Mechanochromism, Reversible Photochromism, and Circularly Polarized Luminescence and Its Applications in Multimodal Anticounterfeiting

An unconventional nano-AIEgen originating from a natural plant polyphenol for multicolor bioimaging

Biocompatible aggregation-induced emission (AIE) materials from natural resources are of great interest for a variety of potential applications. Here, we report the unconventional AIE nature of the green tea polyphenol epigallocatechin gallate (EGCG), which is investigated by observing the disappearance and reoccurrence of fluorescence when EGCG is dissolved and recrystallized in aqueous solutions. The intermolecular through-space conjugation and structural rigidification induced by multiple intermolecular H-bonds play critical roles in the AIE phenomenon. This inspires the development of a multicolored, monodisperse, photostable, and non-toxic nano-AIE luminogen (nano-AIEgen), which is simply prepared by polyphenol-amine-based crosslinking in aqueous solutions, demonstrating great potential for living cell bioimaging. Our strategy to develop nano-AIEgens using AIE-active hydrophilic natural products—e.g., plant polyphenols, such as tannic acid, that exhibit similar AIE characteristics—can help push the boundary of the exploration of various novel, large-scale, biocompatible, water-soluble, and degradable AIE materials from natural resources. • AIE phenomenon for EGCG in the solid state • The AIE activity results from through-space conjugation by intermolecular H-bonds • The EGCG nano-AIEgens may be successfully used to image living cells As a plant polyphenol, epigallocatechin gallate is highly soluble in water and non-toxic. Here, Lu et al. demonstrate an interesting AIE phenomenon in common natural products and propose strategies for screening and developing hydrophilic AIEgens from natural products.

Asymmetric distribution of extracellular matrix proteins in seed coat epidermal cells of Arabidopsis is determined by polar secretion.

Although asymmetric deposition of the plant extracellular matrix is critical for the normal functioning of many cell types, the molecular mechanisms establishing this asymmetry are not well understood. During differentiation, Arabidopsis seed coat epidermal cells deposit large amounts of pectin‐rich mucilage asymmetrically to form an extracellular pocket between the plasma membrane and the outer tangential primary cell wall. At maturity, the mucilage expands on contact with water, ruptures the primary cell wall, and extrudes to encapsulate the seed. In addition to polysaccharides, mucilage contains secreted proteins including the β‐galactosidase MUCILAGE MODIFIED 2 (MUM2). A functional chimeric protein where MUM2 was fused translationally with Citrine yellow fluorescent protein (Citrine) indicated that MUM2‐Citrine fluorescence preferentially accumulates in the mucilage pocket concomitant with mucilage deposition and rapidly disappears when mucilage synthesis ceases. A secreted form of Citrine, secCitrine, showed a similar pattern of localization when expressed in developing seed coat epidermal cells. This result suggested that both the asymmetric localization and rapid decrease of fluorescence is not unique to MUM2‐Citrine and may represent the default pathway for secreted proteins in this cell type. v‐SNARE proteins were localized only in the membrane adjacent to the mucilage pocket, supporting the hypothesis that the cellular secretory apparatus is redirected and targets secretion to the outer periclinal apoplast during mucilage synthesis. In addition, mutation of ECHIDNA, a gene encoding a TGN‐localized protein involved in vesicle targeting, causes misdirection of mucilage, MUM2 and v‐SNARE proteins from the apoplast/plasma membrane to the vacuole/tonoplast. Western blot analyses suggested that the disappearance of MUM2‐Citrine fluorescence at the end of mucilage synthesis is due to protein degradation and because several proteases have been identified in extruded seed mucilage. However, as mutation of these genes did not result in a substantial delay in MUM2‐Citrine degradation and the timing of their expression and/or their intracellular localization were not consistent with a role in MUM2‐Citrine disappearance, the mechanism underlying the abrupt decrease of MUM2‐Citrine remains unclear.

Cyanide detection using a highly selective fluorescent and colorimetrical double channel probe incorporating hybrid naphthopyran–benzothiazole in an aqueous solution

ABSTRACT A highly selective red-emitting fluorescent and colorimetric double-channel probe incorporating a conjugated benzopyran–benzothiazole system is proposed for the detection of cyanide (CN−) in water samples. Under the presence of CN−, the probe displays red fluorescence disappearance, having an immediate (<30 s) visible colour variation from red to colourless. Due to a blocking process where an intramolecular charge transfer occurs, the benzothiazole C = N bond of the probe is attacked by the CN− nucleophile; 1H NMR titration and DFT calculations for this occurrence varied. Results from this investigation enable feasible and simple test strips to be produced for detecting CN− in water samples.

A near-infrared-emission aza-BODIPY-based fluorescent probe for fast, selective, and “turn-on” detection of HClO/ClO−

A novel near-infrared-emitting aza-BODIPY-based fluorescent probe with two tellurium atoms at two upper benzyl rings has been prepared and explored for its fluorescent sensing properties towards hypochlorous acid/hypochorite (HClO/ClO−), which showed high selectivity and absolutely fluorescent “turn-on” phenomenon at 738 nm. The fluorescence of this probe was sufficiently quenched due to photoindued electron transfer by two tellurium atoms. Upon exposure to HClO/ClO−, a strong near-infrared emission at 738 nm appeared with fluorescence quantum yields changing from 0 to 0.11. This remarkable fluorescence change was ascribed to the oxidation of both electron-rich tellurium atoms. The detection limit of this probe towards HClO/ClO− was calculated to 0.09 μM in acetonitrile aqueous solution by the linear fluorescence change at 738 nm in the HClO/ClO−-concentration range of 0–30 μM. Interestingly, this probe was found to be applicable in a broad pH range (2–10). Meanwhile, the oxidized probe could be further responsive to biothiols with substantial fluorescence disappearance. The bioimaging experiments in RAW264.7 cells showed the appearance of intracellular near-infrared fluorescence after addition of HClO/ClO− and PMA, and the fluorescence could also be reversed to be silenced by further introduction of GSH, confirming its potential application for exogenous and endogenous detection of HClO/ClO− in living cells.

Simulating quantum interference effects in the fluorescence of a V-system with perpendicular dipole moments

We present a scheme that enables the observation of interference effects in the resonance fluorescence of a V-type atom with orthogonal dipole moments. Specifically, we consider the atomic configuration of a J g = 0 to J e = 1 transition driven by a single laser field. By employing polarization-sensitive detection in such a way that the light emitted on the two transitions become indistinguishable, we show that one can simulate the effect of vacuum-induced coherence on the resonance fluorescence of this system. In addition, we demonstrate the possibility of realizing atomic transitions with both parallel and antiparallel dipole moments and their effects on the fluorescence spectrum. The interference induced leads to interesting features in the fluorescence spectrum such as asymmetric spectral peaks, enhancement and suppression of the sidebands, and disappearance of fluorescence in the particular direction of detection. The numerical results are understood in the context of the dressed states of the combined atom–field system.

Hydrolysis of 2-Chloro-2-methylpropane—Demonstration Using the Quenching of Fluorescence from Fluorescein

2-Chloro-2-methylpropane slowly hydrolyzes in water, releasing hydrochloric acid. Therefore, the addition of 2-chloro-2-methylpropane to an aqueous solution of sodium hydroxide containing an acid–base indicator causes a color change when the solution becomes acidic. Here we report the use of fluorescein, a fluorescent dye, as an indicator for the completion of the above-mentioned reaction. Under blacklight radiation, completion of the reaction is marked by the disappearance of fluorescence. Compared with the other clock reactions, this fluorescent reaction is more advantageous because it requires inexpensive reagents and involves milder conditions, and it is expected to be utilized in chemistry outreach events. Furthermore, the demonstration can be easily understood by high school students since the reaction mechanism can be explained well by changing the pH, and it is suitable for practice in the classroom.

Synthesis of gelation-induced emissive, o-phenylazonaphthol-based organogel and its responsiveness to fluoride anion

Abstract Type your Abstract text here An organogelator based on o-phenylazonaphthol (o-AN) was synthesized to achieve gelation-induced emission using the resultant organogel. Although the o-AN-containing organogelator did not fluoresce in solution, its resulting organogel became red fluorescent. The fluorescence originated from the aggregation-induced emissive property of o-AN. The structural planarization, required for gelation was induced by the intramolecular hydrogen bond of the o-AN in the organogelator, leading to an intermolecular π-π interaction. The gelation was also facilitated by the non-covalent interaction of the van der Waals force. The gelation was investigated in terms of a molecular packing model and the organogel fluorescence. The organogel collapsed upon exposure to the fluoride anion, because the hydroxyl group of the o-AN was deprotonated, resulting in a weakened hydrogen bond and, finally, the disappearance of fluorescence. The organogel is potentially promising for applications such as ion sensing and stimuli-responsiveness-related fields.

An Unconventional Nano-Aiegen Originating from a Natural Plant Polyphenol for Multicolor Bioimaging

The unconventional aggregation-induced emission (AIE) nature of the green tea polyphenol epigallocatechin gallate (EGCG) was first discovered and investigated by observing the disappearance and reoccurrence of fluorescence (FL) when EGCG was dissolved and recrystallized in aqueous solution. The intermolecular through-space conjugation and structural rigidification induced by multiple intermolecular H-bonds play critical roles in the AIE phenomenon. This inspired the development of a multicolored, monodisperse, photostable and nontoxic nano-AIE luminogen (nano-AIEgen), which was simply prepared by polyphenol-amine-based crosslinking in aqueous solution, and has demonstrated great potential for living cell bioimaging. The strategy to develop nano-AIEgens by assembling overlooked AIE-active hydrophilic natural products (e.g., plant polyphenols, such as tannic acid (TA), which has similar AIE characteristics) rather than traditional hydrophobic AIEgens could help expand the exploration boundary of novel, large-scale, biocompatible, water-soluble, and degradable AIE materials from natural resources.

Novel D-A-D conjugated polymers based on tetraphenylethylene monomer for electrochromism

A monomer (E)-4′,4‴-(1,2-diphenylethene-1,2-diyl)bis([1,1′-biphenyl]-4-carbaldehyde) (DDBC) with AIE properties and two novel DDBC-basing polyazomethines (coded as P1 and P2) were prepared. They were gained in short time, low cost and mild reaction conditions by a straightforward synthetic path. Fluorescent testing shows that DDBC owns an intense aggregation-induced emission (AIE) characteristics. But unfortunately, the polymers based on DDBC do not have AIE effect. It may be attributed that the molecules in the excited state consume light energy in the form of electron transfer, reducing the proportion of energy outputted from light, thus causing the disappearance of macroscopic fluorescence. Another guess is that the tetraphenylethylene (TPE) unit takes part of the conjugated backbone of the polymer. However, P1 have high coloration efficiency (346.94 cm2 C−1) and P2 have short response time (the color switching time is 3.43 s and the bleaching time is 1.41 s at 470 nm). Moreover, P1 has electrochromic properties in the near-infrared field. Thus, these features demonstrate that these two novel polymers have great potential as electrochromic materials in optoelectronics applications.

Effect of increased groundwater viscosity on the remedial performance of surfactant-enhanced air sparging

The effect of groundwater viscosity control on the performance of surfactant-enhanced air sparging (SEAS) was investigated using 1- and 2-dimensional (1-D and 2-D) bench-scale physical models. The viscosity of groundwater was controlled by a thickener, sodium carboxymethylcellulose (SCMC), while an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), was used to control the surface tension of groundwater. When resident DI water was displaced with a SCMC solution (500 mg/L), a SDBS solution (200 mg/L), and a solution with both SCMC (500 mg/L) and SDBS (200 mg/L), the air saturation for sand-packed columns achieved by air sparging increased by 9.5%, 128%, and 154%, respectively, (compared to that of the DI water-saturated column). When the resident water contained SCMC, the minimum air pressure necessary for air sparging processes increased, which is considered to be responsible for the increased air saturation. The extent of the sparging influence zone achieved during the air sparging process using the 2-D model was also affected by viscosity control. Larger sparging influence zones (de-saturated zone due to air injection) were observed for the air sparging processes using the 2-D model initially saturated with high-viscosity solutions, than those without a thickener in the aqueous solution. The enhanced air saturations using SCMC for the 1-D air sparging experiment improved the degradative performance of gaseous oxidation agent (ozone) during air sparging, as measured by the disappearance of fluorescence (fluorescein sodium salt). Based on the experimental evidence generated in this study, the addition of a thickener in the aqueous solution prior to air sparging increased the degree of air saturation and the sparging influence zone, and enhanced the remedial potential of SEAS for contaminated aquifers.

Label-Free and Homogenous Detection of Caspase-3-Like Proteases by Disrupting Homodimerization-Directed Bipartite Tetracysteine Display

Caspase-3-like proteases (e.g., caspase-3 and caspase-7) constitute the core players of cell apoptosis, and their dysregulation has been linked to a number of human diseases, such as cancer and neurodegenerative disorders. However, the methods for measuring caspase-3-like proteases are often complex and time-consuming. Herein, we develop a label-free method to homogeneously detect caspase-3-like proteases in vitro and in complex cell lysate. This assay uses a modular peptide that contains a dimerization domain, a caspase-3/7 cleavage sequence, and a dicysteine motif as the activity sensor to detect caspase-3-like proteases. In the absence of caspase-3-like proteases, the homodimerization of modular peptide brings the dicysteine motif into close proximity and forms a particular configuration suitable for the binding to bisarsenical dye FlAsH-EDT2. The coordination of FlAsH-EDT2 to dimeric peptide forms a highly fluorescent FlAsH-peptide complex. In contrast, the cleavage of the modular peptide by caspase-3-like proteases removes the dicysteine motif from the peptide and abrogates the bipartite tetracysteine display, leading to the disappearance of fluorescence. As a result, the caspase-3-like proteases can be quantitatively evaluated by measuring the change in fluorescence. This assay may be carried out in a "mix-and-read" manner and is, thus, quite simple and convenient. Moreover, this assay is extremely specific and can measure caspase-3 protein down to 1.28 × 10-4 μg/mL. Importantly, the assay is compatible with complex biological samples and can measure both the activation and inhibition of intracellular caspase-3, thereby providing a new approach for the screening of caspase-targeted drugs and the diagnosis of apoptosis-associated diseases.

Alizarin Complexone Functionalized Mesoporous Silica Nanoparticles: A Smart System Integrating Glucose-Responsive Double-Drugs Release and Real-Time Monitoring Capabilities.

The outstanding progress of nanoparticles-based delivery systems capable of releasing hypoglycemic drugs in response to glucose has dramatically changed the outlook of diabetes management. However, the developed glucose-responsive systems have not offered real-time monitoring capabilities for accurate quantifying hypoglycemic drugs released. In this study, we present a multifunctional delivery system that integrates both delivery and monitoring issues using glucose-triggered competitive binding scheme on alizarin complexone (ALC) functionalized mesoporous silica nanoparticles (MSN). In this system, ALC is modified on the surface of MSN as the signal reporter. Gluconated insulin (G-Ins) is then introduced onto MSN-ALC via benzene-1,4-diboronic acid (BA) mediated esterification reaction, where G-Ins not only blocks drugs inside the mesopores but also works as a hypoglycemic drug. In the absence of glucose, the sandwich-type boronate ester structure formed by BA binding to the diols of ALC and G-Ins remains intact, resulting in an fluorescence emission peak at 570 nm and blockage of pores. Following a competitive binding, the presence of glucose cause the dissociation of boronate ester between ALC and BA, which lead to the pores opening and disappearance of fluorescence. As proof of concept, rosiglitazone maleate (RSM), an insulin-sensitizing agent, was doped into the MSN to form a multifunctional MSN (RSM@MSN-ALC-BA-Ins), integrating with double-drugs loading, glucose-responsive performance, and real-time monitoring capability. It has been demonstrated that the glucose-responsive release behaviors of insulin and RSM in buffer or in human serum can be quantified in real-time through evaluating the changes of fluorescence signal. We believe that this developed multifunctional system can shed light on the invention of a new generation of smart nanoformulations for optical diagnosis, individualized treatment, and noninvasive monitoring of diabetes management.

Ultrafast Chemical Dynamics in Time Domain Through Fluorescence Spectroscopy

While absorption and emission spectroscopy have always been used to detect and characterize molecules and molecular complexes, the availability of ultrashort laser pulses and associated computer-aided optical detection techniques allowed study of chemical processes directly in the time domain at unprecedented time scales, through appearance and disappearance of fluorescence from participating chemical species. Application of such techniques to chemical dynamics in liquids, where many processes occur with picosecond and femtosecond time scales lead to the discovery of a host of new phenomena that in turn led to the development of many new theories. Experiment and theory together provided new and valuable insight into many fundamental chemical processes, like isomerization dynamics, electron and proton transfer reactions, vibrational energy and phase relaxation, photosynthesis, to name just a few. In this article, we shall review a few of such discoveries in attempt to provide a glimpse of the fascinating research employing fluorescence spectroscopy that changed the field of chemical dynamics forever.