Aggregation-induced Emission Phenomenon Research Articles

Multi-component synthesis and enhanced photophysical study of novel azolo[1,5-a]pyrimidine based dyes

A series of novel fluorophores were obtained based on azolo[1,5-a]pyrimidines (APs) through multicomponent and oxidation reactions, starting from aminoazoles, morpholineacrylonitrile, and 4-(dimethylamino)benzaldehyde. Photophysical studies, as well as DFT calculations have been performed for the obtained APs. Aggregation-induced emission (AIE) phenomenon was demonstrated for fluorophores containing an aromatic substituent at the C-2 position of the azolo[1,5-a]pyrimidine core. It was observed that fluorophore 6d exhibited reversible mechanochromic luminescence. Two-photon absorption cross-section was measured for all obtained APs. In addition, cell staining resulted in identical intracellular distribution under excitation at 405 nm, 488 nm and 561 nm.

Aggregation-induced emission-based competitive immunoassays for “signal-on” detection of proteins with multifunctional metal–organic frameworks as signal tags

An aggregation-induced emission (AIE)-based strategy was proposed for fluorescence immunoassays of protein biomarkers using Cu-based metal–organic frameworks (Cu-MOFs) to load recombinant targets and enzymes for dual signal amplification. The immunosensing platform was built based on the sequestration and consumption of the substrates of pyrophosphate (PPi) ions by Cu-MOFs and enzymatic catalysis. The negatively charged PPi could trigger the aggregation of positively charged tetraphenylethene (TPE)-substituted pyridinium salt nanoparticles (TPE-Py NPs) by electrostatic interactions, lighting up the fluorescence due to the AIE phenomenon. The consumption of PPi by the captured Cu-MOFs through the Cu2+-PPi chelation interaction and ALP–enzymatic hydrolysis depressed the aggregation of TPE-Py NPs. Capture of the tested targets in samples by the antibodies on the plate surface could prevent the attachment of target/ALP-loaded Cu-MOFs due to the competitive immunoreactions. The “signal-on” competitive immunoassay was applied for the detection of procalcitonin (PCT) as the model analyte with a linear range of 0.01–10 pg/mL and a detection limit down to 8 pg/mL. The conceptual integration of AIE with enzymatic and MOFs–based dual signal amplification endowed fluorescence immunoassays with high sensitivity and selectivity. The surface modification of Cu-MOFs with hexahistine (His6)-tagged recombinant proteins through metal coordination interactions should be evaluable for the design of novel biosensors.

Amide/urea-based simple fluorometric receptors for iodide and Hg2+ ions in aqueous medium: Aggregation induced emission and DFT studies

Herein, we report pyrene-tagged amide and urea-basedsugar derivatives 1and2in a simple synthetic pathway to recognize I− and Hg2+ ions. Both molecules showed absorbance and fluorescence selectivity towards iodide ions in THF/H2O (7/3, v/v) medium. The selectivity and sensitivity of2 for iodide ions are superior to 1due to more H-bond donors in2. Interestingly, fluorometric receptor2exhibited aggregation-induced emission (AIE) at higher pH with a remarkable fluorometric color change. The AIE phenomenon might be explained by the self-association of2 after forming imine functionality in the alkali medium. The Stern-Volmer plot showed the fluorescence quenching constant of each receptor with an iodide ion and indicated the quenching pathway. The LODs of 1and2for iodide ions were evaluated as 0.84 and 0.17 µM, respectively. The 1:1 binding stoichiometry of1or2 with iodide was found from the Job plot and verified by measuring the complex mass.Further, the complexes of each receptor with I− ions can detect Hg2+ ions selectively by fluorescence turn-on method with low sensitivities (LODs: 0.008 µM for 1 and 0.01 µM for 2). DFT results were used to understand the binding mode of receptors 1 and 2 with iodide ions and the quenching process in the aqueous THF medium. The real application of the receptors was established for the recovery of iodide and Hg2+ ions from natural water samples.

Discovery of a novel marine bacterial AIEgen that lights up specific G-quadruplexes

The emergence of aggregation-induced emission (AIE) phenomenon two decades ago marked a significant advancement in chemical science. It has fostered the development of versatile AIE luminogens (AIEgens) applicable in bioimaging, optoelectronics, and biochemical sensing. However, the application potential of synthetic AIEgens is limited owing to their constrained chemical space, environmental concerns, and uncertain biocompatibility. Consequently, the pursuit of naturally derived AIEgens (BioAIEgens) is considered a promising solution to developing next-generation AIEgens. Here, we report the discovery of 2-(2-hydroxy-6-methoxy-3-propionylphenyl)quinazolin-4(3H)-one (HMPQ) from marine bacterial metabolite as AIEgen for the first time. HMPQ shows its unique fluorescence mechanism through excited-state intramolecular proton transfer. Comprehensive photophysical assessments unveiled that HMPQ varied emissions in diverse solvents and solid-state polymorphic forms. Notably, HMPQ exhibited specific binding affinity to G-quadruplexes (G4s), illuminating these non-canonical nucleic acid structures without altering their conformation. Its remarkable safety profile and precise cellular visualization of G4 structures imply HMPQ’s potential in biological applications, opening new avenues for utilizing BioAIEgens as G4 probes.

Ethanol and Gd3+ activated aggregation induced delayed fluorescence in copper nanoclusters for detection of Cr(VI)

In recent years, significant emphasis has been dedicated towards investigating aggregation-induced emission (AIE) phenomena, and a notable addition to this emerging field is aggregation-induced delayed fluorescence (AIDF). Here, we proposed two different strategies to produce AIDF-based luminescent materials at room temperature from glutathione-capped CuNCs (GSH-CuNCs) by (1) simply modifying the solvent environment and (2) introducing gadolinium (Gd3+) ions. The synthesized GSH-CuNCs displayed weak fluorescence (Fl) emission in aqueous solution with a short delayed lifetime of 3.2 μs and quantum yield (QY) of only 1.42 %. However, introducing GSH-CuNCs to an ethanol medium promptly led to enhanced delayed Fl emission with a significantly delayed lifetime of 21.8 μs and a high QY of 89.2 %. Moreover, introducing Gd3+ ions to the aqueous GSH-CuNC solution also enhances delayed Fl emission with a delayed lifetime of 13.6 μs and a high QY of 79.5 %. Analysis of transmission electron microscopy and dynamic light scattering data showed that both the ethanol medium and Gd3+ addition endows controlled aggregation of GSH-CuNCs, enabling successful harvesting of triplet states and ultimately leading to the AIDF phenomenon. Moreover, the AIDF harnessed from GSH-CuNCs by Gd3+ was successfully employed to detect Cr6+ ions in an aqueous solution with excellent selectivity.

Advances in the study of AIE polymers

Aggregation-induced emission (AIE) can exhibit different properties in different situations, such as non-emission and highly fluorescent in the dissolved state of the molecule and in the aggregate or solid state, respectively. This property of AIE is distinguished from aggregation-induced quenching (ACQ) or even the opposite. Combining the AIE phenomenon with different polymers yields different polymers with corresponding AIE properties. In this paper, the mechanism, synthesis, branching and application of AIE in the fields of optoelectronic functional materials, sensors, biology, and environment are reviewed. It is hoped that this review will stimulate more research on molecular aggregates and promote further cross-fertilisation and greater development in the disciplines of materials, chemistry and biomedicine.

Near Infrared Aggregation Induced Electrogenerated Chemiluminescence Studies of Xanthene Dye

Electrogenerated chemiluminescence (ECL) serves as a versatile electrochemical-spectroscopic tool for rapid sample analysis, offering high sensitivity, good selectivity, and a low detection limit. During electrochemical redox reactions of luminophores and often ECL co-reactants, excited state luminophore species are formed through high energetic electron transfer between oxidized and reduced luminophore radicals or between the radical cation or anion and co-reactant intermediates. This process emits photons, generating ECL. Near infrared (NIR) luminophores represent an emerging class of materials in ECL studies. However, greater vibronic coupling between the ground and excited state in NIR luminophores with a lower band gap promotes nonradiative decay. The aggregation-induced emission (AIE) phenomenon overcomes these challenges, demonstrating enhanced radiative emission. We conducted a study on the photophysical, electrochemical, and ECL behavior of XanthCR-880 dye, which comprises a thienylpiperidine donor and a xanthene core as an acceptor. The central xanthene core provides extended conjugated length and increased charge transfer, resulting in NIR absorption at 880 nm and fluorescence emission at 960 nm, with a stroke shift of 80 nm. Cyclic voltammetry performed at a Pt electrode in MeCN with a scan rate of 50 mVs-1 revealed two oxidation waves and two reduction waves at 0.35 V, 0.70 V, -0.70 V, and -1.55 V vs Ag/Ag+, respectively. Due to the limited potential window of the Pt electrode in MeCN (not exceeding -2.5 V, a boron-doped diamond (BDD) electrode was employed at more negative potentials, uncovering an additional reduction wave at -2.62 V vs Ag/Ag+. The cathodic and anodic ECL behavior of XanthCR-880 dye was investigated using benzoyl peroxide and 2-(dibutylamino)ethanol as cathodic and anodic co-reactants, respectively. For cathodic ECL, XanthCR-880 dye produced two ECL waves at the BDD electrode, with peak potentials of -2.06 V and -2.36 V, respectively. In anodic ECL, relatively weak emission was observed at 1.05 V. ECL spectra were generated using the cathodic ECL pathway and interference filters as wavelength selectors, revealing a maximum emission at ~975 nm. The proposed ECL mechanism, as well as AIE studies, will also be discussed.

Enhanced aggregation induced emission by H-bond between the barbiturate molecules containing hydroxyl group

Barbiturates had been widely studied as a molecule with aggregation induced emission (AIE) phenomenon, but barbiturates as a group with multiple hydrogen bond donor and acceptor sites, the relationship between intermolecular hydrogen bond and AIE phenomenon has not been mainly studied. In this paper, a new barbiturate fluorescence molecule BNOH with hydroxyl group was designed and synthesized in order to analyze the relationship between hydrogen bond and molecular AIE phenomenon by increasing the functional group (–OH) that was easy to form hydrogen bond. By spectroscopic analysis, BNOH had structural torsion in aqueous mixed solution, which led to fluorescence decrease, while in aprotic mixed solvent, there was strong AIE phenomenon. DFT and TD-DFT calculations at the B3LYP/6-31G (d) were performed for a deeper understanding of optical transitions. In addition, in order to investigate the difference of its fluorescence phenomenon, two other barbiturate derivatives were synthesized and their spectra were compared with BNOH. The relationship between hydrogen bond and AIE phenomenon of barbiturates was proved, and the fluorescence mechanism of BNOH in organic solvent was proposed and determined. We believe that this study will not only increase the understanding of barbiturate AIE compounds, but also contribute to the study of the important role of hydrogen bonds in the fluorescence phenomenon of barbiturate AIE compounds.

Tetraphenylethene-based mononuclear aggregation-induced emission (AIE)-active mechanofluorochromism gold(I) complexes with different auxiliary ligands

In this study, a series of tetraphenylethene-containing gold(I) complexes with different auxiliary ligands have been synthesized. These complexes were characterized using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Their aggregation-induced emission (AIE) behaviors were investigated through ultraviolet/visible and photoluminescence spectrum analyses, and dynamic light scattering measurements. Meanwhile, their mechanofluorochromic properties were also studied via solid-state photoluminescence spectroscopy. Intriguingly, all these mononuclear gold(I) molecules functionalized by tetraphenylethene group demonstrated AIE phenomena. Furthermore, five gold(I) complexes possessing diverse auxiliary ligands exhibited distinct fluorescence changes in response to mechanical grinding. For luminogens 2–5, their solids showed reversible mechanofluorochromic behaviors triggered by the mutual transformation of crystalline and amorphous states, while for luminogen 1, blue-green-cyan three-color solid fluorescence conversion was realized by sequential mechanical grinding and solvent fumigation. Based on this stimuli-responsive tricolored fluorescence feature of 1, an information encryption system was successfully constructed.

Bioelectrocatalytic Activity of One-Dimensional Porous Pt Nanoribbons for Efficient Inhibition of Tumor Growth and Metastasis.

Designing and synthesizing one-dimensional porous Pt nanocrystals with unique optical, electrocatalytic, and theranostic properties are gaining lots of attention, especially to overcome the challenges of tumor recurrence and resistance to platinum-based chemotherapy. Herein, we represented an interesting report of a one-step and facile strategy for synthesizing multifunctional one-dimensional (1D) porous Pt nanoribbons (PtNRBs) with highly efficient therapeutic effects on cancer cells based on inherent electrocatalytic activity. The critical point in the formation of luminescent porous PtNRBs was the use of human hemoglobin (Hb) as a shape-regulating, stabilizing, and reducing agent with facet-specific domains on which fluorescent platinum nanoclusters at first are aggregated by aggregation-induced emission phenomena (AIE) and then crystallized into contact and penetration twins, as intermediate products, followed by shaping of the final luminescent porous ribbon nanomaterials, owing to oriented attachment association via the Ostwald ripening mechanism. From a medical point of view, the key strategy for effective cancer therapy occured via using low-dosage ethanol in the presence of electroactive porous PtNRBs based on intracellular ethanol oxidation-mediated reactive oxygen species (ROS) generation. The role of heme groups of Hb, as electrocatalytically active centers, was successfully demonstrated in both kinetically controlled anisotropic growth of NRBs for slowing down the reduction of Pt(II) followed by oligomerization of Pt(II)-Hb complexes via platinophilic interactions as well as electrocatalytic ethanol oxidation for therapy. Interestingly, hyaluronic acid-targeted (HA) Hb-PtNRB in the presence of low-dose ethanol caused extraordinary arrest of tumor growth and metastasis with no recurrence even after the treatment course stopped, which caused elongation of tumor-bearing mice survival. HA/Hb-PtNRB was completely biocompatible and exhibited high tumor-targeting efficacy for fluorescent imaging of breast tumors. Therefore, the synergistic electrocatalytic activity of PtNRBs is presented as an efficient and safe cancer theranostic method for the first time.

Tailoring Emission Color Shifts in Mechanofluorochromic-Active AIE Systems of Carbazole-Based D-π-A Conjugates: Impact of π Spacer Unit Variants.

The expanding field of organic electronics has led to the emergence of donor-π-acceptor (D-π-A) systems as promising candidates for various optoelectronic applications. Recent advancements in the design of organic fluorophores allow precise modulation of their optical properties in the solution and solid states, broadening their utility. Here, we synthesize and characterize two series of D-π-A systems based on carbazole-cyanostilbene compounds (3a-c and 4a-c), which feature differences in π-spacer groups and substitution on the acceptor cyanostilbene units. These compounds exhibit intramolecular charge transfer (ICT) characteristics, with 3c possessing a phenyl spacer and -CF3 substitution displaying notable solvatochromism and polarity-enhanced emission (PEE). Additionally, both series show aggregation-induced emission (AIE), with emission color shifts controlled by spacer groups. These compounds demonstrate diverse emissive behaviors, including locally excited (LE), twisted intramolecular charge transfer (TICT), and π-π stacked aggregated states, contributing to the AIE phenomenon. Compounds with phenyl spacers (3a-c) exhibit higher solid-state quantum yields than those of thiophene (4a-c). Furthermore, the impact of spacer groups and acceptor substitutions on the solid-state emissive properties and mechanofluorochromism (MFC) are highlighted. Compounds with phenyl spacers and substitution (3a, 3c) show a blue-shifted MFC, while those with thiophene (4a, 4c) display a red-shifted MFC. These findings offer insights into the development of advanced materials with tunable emission properties and high thermal stability for optoelectronic applications.

Two-Photon-Responsive "TICT + AIE" Active Naphthyridine-BF2 Photoremovable Protecting Group: Application for Specific Staining and Killing of Cancer Cells.

The combined effects of twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) phenomena have demonstrated a significant influence on excited-state chemistry. These combined TICT and AIE features have been extensively utilized to enhance photodynamic and photothermal therapy. Herein, we demonstrated the synergistic capabilities of TICT and AIE phenomena in the design of the photoremovable protecting group (PRPG), namely, NMe2-Napy-BF2. This innovative PRPG incorporates TICT and AIE characteristics, resulting in four remarkable properties: (i) red-shifted absorption wavelength, (ii) strong near-infrared (NIR) emission, (iii) viscosity-sensitive emission property, and (iv) accelerated photorelease rate. Inspired by these intriguing attributes, we developed a nanodrug delivery system (nano-DDS) using our PRPG for cancer treatment. In vitro studies showed that our nano-DDS manifested effective cellular internalization, specific staining of cancer cells, high-resolution confocal imaging of cancerous cells in the NIR region, and controlled release of the anticancer drug chlorambucil upon exposure to light, leading to cancer cell eradication. Most notably, our nano-DDS exhibited a substantially increased two-photon (TP) absorption cross section (435 GM), exhibiting its potential for in vivo applications. This development holds promise for significant advancements in cancer treatment strategies.

A 3D nanoscale optical disk memory with petabit capacity.

High-capacity storage technologies are needed to meet our ever-growing data demands1,2. However, data centres based on major storage technologies such as semiconductor flash devices and hard disk drives have high energy burdens, high operation costs and short lifespans2,3. Optical data storage (ODS) presents a promising solution for cost-effective long-term archival data storage. Nonetheless, ODS has been limited by its low capacity and the challenge of increasing its areal density4,5. Here, to address these issues, we increase the capacity of ODS to the petabit level by extending the planar recording architecture to three dimensions with hundreds of layers, meanwhile breaking the optical diffraction limit barrier of the recorded spots. We develop an optical recording medium based on a photoresist film doped with aggregation-induced emission dye, which can be optically stimulated by femtosecond laser beams. This film is highly transparent and uniform, and the aggregation-induced emission phenomenon provides the storage mechanism. It can also be inhibited by another deactivating beam, resulting in a recording spot with a super-resolution scale. This technology makes it possible to achieve exabit-level storage by stacking nanoscale disks into arrays, which is essential in big data centres with limited space.

Understanding the AIE phenomenon of nonconjugated rhodamine derivatives via aggregation-induced molecular conformation change

The bottom-up molecular science research paradigm has greatly propelled the advancement of materials science. However, some organic molecules can exhibit markedly different properties upon aggregation. Understanding the emergence of these properties and structure-property relationship has become a new research hotspot. In this work, by taking the unique closed-form rhodamines-based aggregation-induced emission (AIE) system as model compounds, we investigated their luminescent properties and the underlying mechanism deeply from a top-down viewpoint. Interestingly, the closed-form rhodamine-based AIE system did not display the expected emission behavior under high-viscosity or low-temperature conditions. Alternatively, we finally found that the molecular conformation change upon aggregation induced intramolecular charge transfer emission and played a significant role for the AIE phenomenon of these closed-form rhodamine derivatives. The application of these closed-form rhodamine-based AIE probe in food spoilage detection was also explored.

Aggregation‐Induced Emission (AIE) of Au(I)‐GSH Complexes is Activated by Optical Manipulation and Exhibits Surprising 780 nm Emission

AbstractAn optical manipulation method to activate the aggregation‐induced emission (AIE) of Au(I)‐glutathione (Au(I)‐GSH) complexes is presented. First, the well‐known AIE‐type Au(I)‐GSH complexes with a solid emission wavelength of 570 nm are synthesized. At the beginning of the focusing a 1064 nm continuous‐wave (CW) laser at the interface of Au(I)‐GSH complexes solution, its luminescence is hardly detectable. However, with the extension of the laser irradiation time, aggregate appears and rapidly grows, and strong luminescence is shown, indicating the activation of AIE of Au(I)‐GSH complexes through optical manipulation. Surprisingly, the emission peak is at 780 nm and no blue‐shift is observed with the emission intensity increases. The activated AIE emission wavelength by optical manipulation is longer than reported previously, which means that optical manipulation activates AIE in a unique manner. The switching on/off of the activation of AIE is arbitrarily controlled by changing the laser power. In this paper, the luminescence phenomenon and mechanism of AIE are discussed from the perspective of the movement limitation of Au(I)‐GSH complexes under optical manipulation. It is of significant importance for further insights into the luminescence of Au(I)‐GSH complexes and their future development.

Theoretical Study of the Photocyclization Reaction-Induced Dual Aggregation-Induced Emission Phenomenon.

Photochromic molecules with aggregation-induced emission (AIE) effects are of great value and prospective in various practical applications. To explore its inherent mechanism, the open isomer ap-BBTE and the closed isomer c-BBTE were chosen to perform the theoretical calculation using the quantum mechanics/molecular mechanics model combined with thermal vibration correlation function formalism. The calculations show that the photocyclization (PC) reaction from ap-BBTE to c-BBTE facilitates an improvement in the AIE effect. It is found that the fluorescence quantum yield (ΦF) enhancement of ap-BBTE is attributed to the restriction of the low-frequency rotational motion of the benzothiophene moiety and the high-frequency stretching vibrations of the C-C bond between the benzothiophene and benzylbis(thiadiazole) vinyl groups after aggregation. For c-BBTE, the increase in ΦF upon aggregation is mainly due to the suppression of the high-frequency stretching vibration of the C-C bond between the benzothiophene and the benzobis(thiadiazole) vinyl groups. In addition, the AIE effect was also enhanced from ap-BBTE to c-BBTE, which is consistent with the experimental phenomenon. The corresponding emission spectrum red-shifted from ap-BBTE to c-BBTE in both dilute solution and the crystalline state due to the improved intramolecular conjugation of c-BBTE. Moreover, the PC reaction from ap-BBTE to c-BBTE easily occurs in an excited state with a low energy barrier transition state by forming a C-C bond between benzothiophene groups effectively in dilute solution. Our calculations provide theoretical guidance for the further rational design of efficient AIE luminogens.

Carbazole-modified dicyanoethylene derivatives exhibiting tert-butyl-regulated aggregation-induced emission and reversible high-contrast mechanofluorochromism

Dibenzothiophene, dicyanoethylene, and carbazole were used as building blocks in the synthesis of two novel donor-acceptor-type molecules, DBT-CE-C and DBT-CE-BC. These compounds exhibit typical intramolecular charge transfer (ICT) behavior. Importantly, DBT-CE-C and DBT-CE-BC exhibit strong reversible high-contrast mechanofluorochromism and aggregation-induced emission (AIE) due to the introduction of tert-butyl groups in the 3- and 6-positions of carbazole. In the solid state, DBT-CE-C and DBT-CE-BC exhibit robust emissions, with fluorescence efficiencies of 0.315 and 0.504, respectively. They also exhibit distinct AIE phenomena, with AIE factors of 63.0 and 26.5, respectively. Notably, during the grinding process, the initially green- and yellow-green-emitting solid powders of DBT-CE-C and DBT-CE-BC undergo a transition to yellow and orange-red emission, respectively. Simultaneously, their emission peaks shift from 511 to 532 nm to 574 and 603 nm, respectively. Experiments using powder X-ray diffraction on as-prepared, ground, and fumed solid samples of these compounds provide evidence that their mechanofluorochromic properties stem from a phase shift between crystalline and amorphous states under external stimuli. The reduction in bandgap due to the ICT effect, coupled with increased π–π interactions, exciton coupling, and orbital overlap between neighboring molecules, accounts for the observed red shift in the photoluminescence spectra when subjected to external stimulation.

Endowing an amphiphilic aggregation-induced emission molecule with turn-on fluorescence in both latent fingerprints development and antibiotics detection

The water-soluble aggregation-induced emission (AIE) molecule is desirable as a turn-on fluorescence probe, but it is challenging because most AIE-based molecules are lipophilic and can emit strong fluorescence in water. To address the problem, tetraphenylethene (TPE) backbones are decorated with hydrophilic pyridine ethanol-related groups, and a series of novel amphiphilic TPE-based pyridinium salts (denoted as TPE-Py-OH, TPE-2Py-2OH and TPE-4Py-4OH) are synthesized. Encouragingly, TPE-2Py-2OH aqueous solution which is almost non-emissive can be used as a bifunctional turn-on fluorescent probe for developing latent fingerprints (LFPs) and detecting antibiotics. Level 3 details in LFPs are developed via soaking/ spraying method, owing to that AIE phenomenon is activated by the combination of lipophilic part in TPE-2Py-2OH and fatty acid residues in fingerprints. The method is worthy to promote, because it displays the advantages of water solubility, low working concentration, ease of operation, good stability, high safety, high contrast, high sensitivity, and high selectivity. It can also response to penicillin potassium (PNG) with a detection limit of 0.18 μM because the electrostatic interaction between TPE-2Py-2OH and PNG can mainly induce the enhanced fluorescence. This discovery provides a facile approach to design more promising amphiphilic AIE-based turn-on fluorescence probes.

A novel approach to supramolecular Aggregation-Induced emission using tetracationic tetraphenylethylene and sulfated β-Cyclodextrin

The combination of aggregation-induced emission-based luminogens (AIEgens) with supramolecular chemistry has gained significant attention due to its ability to produce intense emission even at low concentrations. In this study, we report a supramolecular arrangement characterized by aggregation-induced emission through the integration of tetracationic tetraphenylethylene with a macrocyclic polyanionic derivative of β-cyclodextrin. Despite the exploration of ionic derivatives of cyclodextrins in pharmaceutical and host–guest supramolecular chemistry, the phenomenon of supramolecular aggregation-induced emission based on non-covalent interactions between the ionic derivative of β-cyclodextrin and derivatives of tetraphenylethyelene, a class of AIEgens, has received limited investigation. Our work explores AIE shown by the allylimidazolium derivative of tetracationic tetraphenylethyelene (ALITPE) induced by complexation with polyanionic sulfated β-cyclodextrin (SCD). The effectiveness of the emission intensity of this supramolecular assembly based on AIE is confirmed by steady-state and time-resolved fluorescence measurements, which are supported by ground-state absorption measurements. We also investigate the effect of changes in external environment, such as temperature, pH, and ionic strength, on the supramolecular assembly. Moreover, the aggregation behavior of ALITPE with SCD is comparatively studied with neutral native β-cyclodextrin, highlighting the contribution of high negative charge density on the surface of SCD for efficient aggregation with ALITPE molecules. Additionally, Molecular Docking calculations are employed to provide insights into the aggregation behavior of ALITPE molecules induced by SCD. Overall, our findings demonstrate the potential applicability of the ALITPE/SCD supramolecular assembly as a potential fluorescent sensing probe for various biological applications.

Aggregation-induced emission for the detection of peptide ligases with improving ligation efficiency

BackgroundMonitoring peptide ligase activity is of great significance for biological research, medical diagnosis, and drug discovery. The current methods for the detection of peptide ligases suffer from the limitations of high background signal, elaborate design of substrate, and high reversibility of ligation reaction. In this work, we proposed a simple and sensitive method for ligase detection with reducing ligation reversibility on the basis of aggregation-induced emission (AIE) mechanism. ResultsThe peptide probes labeled with AIE luminogens (AIEgens) were water-soluble and emitted weak fluorescence. After ligation reaction, the enzymatic products with AIEgens showed high hydrophobicity and could readily assembly into aggregates, thus lighting up the fluorescence. More interestingly, the formation of aggregates pushed the equilibrium to the generation of the desired ligation products, thus improving the catalytic efficiency by driving the reaction towards completion. The ligation reaction conversion rate (>80 %) is significantly higher than that without blocking the reversibility with additional treatment. With sortase A (SrtA) as the analyte example, the detection limit of this method was found to be 0.01 nM with a linear range of 0–50 nM. The system was applied to evaluate the inhibition efficiency of berberine chloride and quercetin and determine the activity of SrtA in serum, lysate and Staphylococcus aureus with satisfactory results. SignificanceThis study indicated that the ligation efficiency and detection sensitivity can be improved by reducing ligation reversibility through AIE phenomenon. The proposed strategy could be used for the detection of other peptide ligases by adopting sequence-specific peptide substrates.