Red Aggregation-induced Emission Research Articles

Modulation of AIE and Intramolecular Charge Transfer of a Pyrene-Based Probe for Discriminatory Detection and Imaging of Oligomers and Amyloid Fibrils.

Oligomers and amyloid fibrils formed at different stages of protein aggregation are important biomarkers for a variety of neurodegenerative diseases including Alzheimer's and Parkinson's diseases. The development of probes for the sensitive detection of oligomeric species is important for early stage diagnosis of amyloidogenic diseases. Many small molecular dyes have been developed to probe the dynamic growth of amyloid fibrils. However, there is a lack of discriminatory detection strategies to monitor the dynamics of both oligomers and amyloid fibrils based on the differential modulation of the photophysical properties of a single dye. Here we report a pyrene-based intramolecular charge transfer (ICT) dye with large Stokes shifted red-emitting aggregation induced emission (AIE) for monitoring the dynamic populations of both oligomers and fibrils during the aggregation of hen egg white lysozyme (HEWL) protein. At the early stage of protein aggregation, the accumulation of HEWL oligomers results in a rapid and substantial increase in the red AIE intensity at 660 nm. Later, as the oligomers transform into mature fibrils, the dye exhibits a distinct photophysical change. Binding of the dye to HEWL fibrils strongly suppresses the red AIE and enhances ICT emission. This is evidenced by a gradual decrease in the AIE intensity (∼660 nm) and an increase in LE (∼490 nm) and ICT (∼540 nm) emission intensities during the later stages of protein aggregation. Thus, the dye provides simultaneous measurements of the population dynamics of both HEWL oligomers and fibrils during protein aggregation based on the discriminatory modulation of AIE and ICT of the dye. The dye also enables imaging of both HEWL oligomers and fibrils simultaneously using different emission channels in super-resolution confocal fluorescence microscopy.

Molecular Engineering of Red Aggregation-Induced Emission Luminogens with Small Conjugated Structures

Molecular Engineering of Red Aggregation-Induced Emission Luminogens with Small Conjugated Structures

Novel solution and solid-state emissive long-wavelength carbon dots for water sensing and white LED applications

Carbon dots (CDs) are among the most popular nanomaterials due to their remarkable fluorescent and electronic properties, as well as their good biocompatibility and low cytotoxicity. Currently, CDs with aggregation-induced emission (AIE) are relatively rare and have become a significant research hotspot. This is because most conventional CDs suffer from severe quenching in a solid state. Herein, novel CDs with both solution and solid-state emissions were obtained using a facile one-step hydrothermal synthesis. Specifically, the CDs exhibit yellow solvent-dependent fluorescence in solution state (λem = 580 nm) and red AIE emission in solid state (λem = 640 nm). CDs powder is utilized as a red phosphor for light-emitting diode (LED). The resulting fabricated white LEDs (WLEDs) demonstrate good performance metrics, including a Color Rendering Index (CRI) of 89.5, Correlated Color Temperature (CCT) of 3876 K, and commission Internationale d’Éclairage (CIE) coordinates of (0.350, 0.331). Furthermore, the solvent-dependent phenomenon observed in AIE-CDs can be exploited to apply their solution as a highly sensitive fluorescence sensor for quantitatively detecting amounts of water in various organic solvents. The method offers both high accuracy and sensitivity, with R2 values varying from 0.853 to 0.994 and a low detection limit ranging from 0.296 to 3.23 % across a wide linear range. This inherent versatility makes the CDs suitable for a wide range of applications, including sensing and LED devices.

Ratiometric red aggregation-induced emission luminogens for hydrazine hydrate detection

Based on a deprotection reaction and intramolecular charge transfer (ICT) mechanism induced by hydrazine hydrate, a fluorescent probe for the rapid recognition of hydrazine hydrate (N2H4·H2O) was designed. A simple one-step condensation reaction was employed to synthesize a series of novel aggregation-induced emission fluorescent probes with good sensitivity and selectivity for N2H4·H2O. The detection limits for N2H4·H2O using 1 to 3 were 1.51, 0.544 and 2.61 μM, respectively, at a probe concentration of 20.0 μM. Furthermore, probes 1–3 were able to detect N2H4·H2O in living cells and it was found that probes 1–3 could interact with N2H4·H2O to provide an effective tool for on-line monitoring. Moreover, probe 1 is capable of the imaging and tracing of N2H4·H2O in zebrafish.

Temperature-responsive polymeric sensors based on triphenylamine linked naphthalimide with red aggregation-induced emission

Temperature-responsive fluorescence sensors have attracted great attention in recent years. Herein, we designed a series of AIE-based polymer sensors for monitoring the temperature in the physiological environment. In these polymers, a triphenylamine-naphthalimide chromophore (TPANIP) was used as the signal unit which can output the red emission in aggregated state. Different ratios of the temperature-responsive unit (NIPMAM) and the water-soluble unit (N-(2-(2-hydroxyethoxy)ethyl)methacrylamide, HEOEMA) were introduced to adjust the responsibility of the polymers in suitable temperature region and sensitivity. The structural and optical properties of all polymers were investigated by GPC, 1H NMR, FTIR, fluorescence spectroscopy and SEM. Among them, the polymer P1 (TPANIP/NIPMAM = 1/10) without the water-soluble unit shows the best sensing property. It performs a linear response to the temperature at the region of 15–50 °C in its aqueous solution with low concentration (0.5 mg/mL). By optimizing the work medium, polymer P1 can outputs the turn on signals with the increase of temperature. The enhanced emission mode is more suitable for the fluorescent detection that the turn off one.

Bio-inspired pigment particles with dual-variation modes of structural colors and fluorescence

Colorful pigments have demonstrated values in constructing dynamic patterns for different applications. Attempts in this field tend to develop pigments with multiple modes for color variation. Herein, inspired by the color variation mechanism of chameleons, we propose a novel kind of pigments with dual color variations (PDCVs) by integrating hydrophobic carbon dots (HCDs) within photonic crystal (PhC) particles. The HCDs with blue dispersion emission and red aggregation-induced emission are generated via one-pot solvothermal treatment. The PDCVs are generated by using HCDs-tagged responsive hydrogel to replicate the nanostructure of silica nanoparticles assembled spherical PhC particles. As the dispersion/aggregation of HCDs and hydrogel lattice of the PhC are depending on their surrounding solvent, the resultant PDCVs can perform dual color variations, including fluorescence and structure color, by changing their solvent. Based on this feature, we have demonstrated that the PDCVs can be employed as elements to construct various dynamic colorful patterns with wide viewing angle and allow for eminent information encryption. There results indicate that the proposed PDCVs are promising to have practical applications in the fields of information encryption, displaying, anti-counterfeiting, and so on.

A novel red AIE fluorescent probe for ratiometric detection of carbon monoxide in vitro and in vivo.

As a significant signaling gas molecule, carbon monoxide (CO) has a crucial impact on various physiological and pathological processes in organisms, particularly in oxidative stress processes. Hence, designing and synthesizing a fluorescent probe that can effectively image CO in vivo holds immense significance. In this work, under the guidance of density functional theory (DFT) and time-dependent density functional theory (TDDFT), we designed and synthesized a red aggregation-induced emission (AIE) fluorescent probe THBTA-CO for CO detection and imaging. The fluorescent probe displayed green fluorescence emission at 535 nm before the CO response. However, upon CO response, with the involvement of Pd2+, the probe emitted red fluorescence at 630 nm. Furthermore, we successfully demonstrated the potential of THBTA-CO in visualizing both exogenous and endogenous CO in living cells. Significantly, THBTA-CO was effectively employed to image CO in lipopolysaccharide (LPS)-induced oxidative stress in mice. These findings convincingly establish THBTA-CO as a promising fluorescent probe for CO sensing and imaging, thereby facilitating a better understanding of CO's role in biomedical research.

Facile Preparation Strategy of Novel Carbon Dots with Aggregation‐Induced Emission and Room‐Temperature Phosphorescence Characteristics

AbstractAs one of the most promising fluorescent nanomaterials, carbon dots (CDs) are extensively studied. Nevertheless, one‐pot synthesis methods for CDs with both dual emission aggregation‐induced emission (AIE) and room‐temperature phosphorescence (RTP) could lead to significant breakthrough in extensive application fields. Herein, a new class of CDs (E‐CCDs) with reversible luminescence (blue dissolved fluorescence and red AIE) and RTP behavior is obtained with an eco‐friendly, low‐cost one‐pot solvothermal method. E‐CCDs exhibit dual fluorescence emission at 460 (Em‐1) and 600 nm (Em‐2), which is related to different emission centers. The addition of cyanic acid enhances the RTP behavior with a lifetime of 1.17 s, which lasts for ≈9 s to the naked eye. Based on the unique fluorescence and phosphorescence characteristics of CDs, E‐CCDs can be potentially used for fingerprint detection and information encryption.

Lipid Droplet-Specific Red Aggregation-Induced Emission Luminogens: Fast Light-Up of Gram-Positive Pathogens for Identification of Bacteria

Lipid Droplet-Specific Red Aggregation-Induced Emission Luminogens: Fast Light-Up of Gram-Positive Pathogens for Identification of Bacteria

Aggregation-induced fluorescence ‘turn on’ imaging for fingerprints by an amphiphilic probe: Synthesis and performance

Fingerprints are important biological details and play an important role in identifying personal information. To assist the identification of latent fingerprints (LFPs) which are the frequently-met cases in practical application, LFPs are usually made visible/detectable by development (imaging) techniques. In this work, an amphiphilic probe (denoted as HNP) was designed and synthesized. Its amphiphilic nature was confirmed by its single crystal structure and lipid-water partition coefficient (P = 1.38). It showed good solubility in water and bright red AIE (aggregation-induced emission) emission upon visible light excitation (∼410 nm), which satisfied the requirements for LFPs development/imaging. Photophysical parameters (absorption spectrum, emission spectrum, and emission quantum yield), LFPs imaging performance and bio-safety of probe HNP were discussed and reported. It was found that HNP showed efficient AIE effect in aggregated state. After meeting the lipids in LFPs, HNP AIE effect was activated, showing emission “turn-on” phenomenon and LFPs pattern. This mechanism was confirmed by micromorphology analysis. Corresponding dynamics were discussed as well. Good stability and durability were observed for HNP development/imaging. Details down to level 3 were successfully retrieved with high contrast.

Leveraging bacterial survival mechanism for targeting and photodynamic inactivation of bacterial biofilms with red natural AIEgen

Different from bacterial individuals, bacteria that live in a multicellular lifestyle with biofilm protection exert more severe and harmful attacks on human health. Such bacterial communities are hard to tackle with external agents, including antibiotics and bactericides. Therefore, developing versatile agents to detect and prevent bacterial biofilm is a simultaneously urgent yet challenging task. Herein, we report a naturally occurring red aggregation-induced emission luminogen (AIEgen), Tanshinone IIA, which is capable of specifically targeting bacterial biofilms, remarkably promoting bacterial aggregation, as well as effectively eliminating biofilm bacteria by means of photodynamic therapy. By conveying the concept of utilizing natural resources to battle environmental bacterial problems, this work demonstrates the ability of natural red-emissive AIEgen as a simple, cost-effective, bacterial biofilm-targeting and -erasing dual-functional agent, as well as providing a blueprint for a new direction of innovating environmental bactericides. • A naturally occurring red-emitting aggregation-induced emission luminogen is exploited • Targeting specificity to bacterial biofilm and promotion of bacterial aggregation • Effective elimination of biofilm bacteria by photodynamic therapy • New concept of natural resources as a simple and efficient biofilm inactivation agent Exploring versatile materials for simultaneous bacterial biofilm detection and inactivation is challenging. Lee et al. report a red-emissive natural AIEgen called Tanshinone IIA and its applications in biofilm staining, bacterial aggregation, and photodynamic bacterial inactivation. The study provides insights for fluorescent nano-aggregates and bacteria interaction.

Aggregation‐Induced Emissive Carbon Dots Gels for Octopus‐Inspired Shape/Color Synergistically Adjustable Actuators

AbstractSome living organisms such as the octopus have fantastic abilities to simultaneously swim away and alter body color/morphology for disguise and self‐protection, especially when there is a threat perception. However, it is still quite challenging to construct artificial soft actuators with octopus‐like synergistic shape/color change and directional locomotion behaviors, but such systems could enhance the functions of soft robotics dramatically. Herein, we proposed to utilize unique hydrophobic carbon dots (CDs) with rotatable surficial groups to construct the aggregation‐induced emission (AIE) active glycol CDs polymer gel, which could be further employed to be interfacially bonded to an elastomer to produce anisotropic bilayer soft actuator. When putting the actuator on a water surface, glycol spontaneously diffused out from the gel layer to allow water intake, resulting in a color change from a blue dispersion fluorescence to red AIE and a shape deformation, as well as a large surface tension gradient that can promote its autonomous locomotion. Based on these findings, artificial soft swimming robots with octopus‐like synergistic shape/color change and directional swimming motion were demonstrated. This study provides an elegant strategy to develop advanced multi‐functional bio‐inspired intelligent soft robotics.

Fluorescent thermochromic wood-based composite phase change materials based on aggregation-induced emission carbon dots for visual solar-thermal energy conversion and storage

Efficient solar-thermal energy conversion and storage is significant to overcome current energy shortage problems. Monitoring solar-thermal energy storage process by an evident and convenient display is conducive to improving energy utilization. Herein, fluorescent thermochromic wood-based composite phase change materials (WPCMs) were constructed for visual solar-thermal energy conversion and storage. It was fabricated by encapsulating polyethylene glycol (PEG) and aggregation-induced emission carbon dots (AIE-CDs) showing blue dispersed emission and red aggregation-induced emission into delignified wood (DW). The DW well-preserved the distinctive anisotropic porous structure and prevented the leakage problem of PEG. The WPCMs possessed great solar-thermal conversion capacity benefitting from strong and broad solar light absorption behaviors of AIE-CDs. Additionally, WPCMs showed real-time and visual fluorescent thermochromic property, it exhibited red AIE, and the fluorescence (FL) decreased and shifted into the blue emission band under solar radiation. The solar-thermal energy conversion and storage led to solid–liquid transformation of WPCMs, which promoted AIE-CDs’ dispersion, thereby changing the FL. It also exhibited a high latent heat of fusion (160.8 J·g−1), favorable stability over 150 heating–cooling cycles, thermal stability below 210 °C and good shape stability. The WPCMs can be extended to applications in energy-saving buildings and optical lighting materials with visual thermal regulation capability.

Facile fabrication of a red AIE luminogen with simple structure and bright emissions for cell imaging

Fluorescence imaging in red region is of great interest in both practical applicantion and fundamental research. However, the complicated synthetic approaches and low emission efficiency of the fluorescence materials are still implement their bilolgical applications. Herein, a facile synthesis method for a red luminogen with aggregation-induced emission (AIE) is reported. The AIE probe possesses simple structure and high red brightness, favoring its applications toward in vitro and vivo imaging. This study offers an ideal architecture for the construction of red AIEgens with a simple structure.

Red AIE Luminogens with Tunable Organelle Specific Anchoring for Live Cell Dynamic Super Resolution Imaging

AbstractLysosomes and mitochondria play an important role in maintaining cell homeostasis. Visualizing the long‐term activities of lysosomes and mitochondria on the nanometer scale in live cells is essential for further understanding their functions but remains challenging due to the limitations of existing fluorescent probes, such as aggregation‐caused quenching (ACQ) effect, limited signal‐to‐noise ratio from fluorescence “always on” in the process of targeting organelle and poor photobleaching resistance. Herein, two efficient red‐emitting aggregation‐induced emission (AIE) luminogens are reported, which showed “off‐on” fluorescence characteristic and specific lysosomes as well as mitochondria targeting capability. Owing to their AIE characteristics, a Stokes’ shift larger than 100 nm, good biocompatibility, and excellent photostability, the AIE luminogens have been successfully utilized for high fidelity imaging of lysosomes and mitochondria. By virtue of these two probes, stimulated emission depletion (STED) images of dynamic lysosomal fusion and mitochondrial fission with a high resolution of 65.6 nm are obtained. Furthermore, the interactions between lysosomes and mitochondria in the process of mitophagy are recorded. This study also provides practical guidance for designing specific organelle targeting probes to support live cell dynamic super‐resolution imaging.

Cleancap-Regulated Aggregation-Induced Emission Strategy for Highly Specific Analysis of Enzyme.

In this work, a cleancap-regulated aggregation-induced emission (AIE) strategy based on copper nanoclusters (CuNCs) was developed with stepwise recognition for highly specific analysis of the enzyme. The dissolved CuNCs with AIE characteristics in alkaline solution were prepared by using p-mercaptophenylboronic acid as the reducing agent and the stabilizing ligand. The prepared CuNCs can specifically conjugate with glucose (Glu) to connect with each other via the rapid boronate esters formation between boronic acids of CuNCs and a pair of cis-diols on Glu. The cleancap-regulated AIE strategy was further identified by modification of CuNCs with d-glucose 6-phosphate (P-Glu) as the capper and substrate. Introduction of alkaline phosphatase to the P-Glu/CuNCs complex can induce the cleavage of phosphate group to activate the 5,6-diol of Glu on the CuNCs. The decapped complexes could be aggregated through further conjugation between 5,6-diol and boronic acid of two CuNCs, resulting in strong red AIE luminescence. The dual recognitions of enzymatic cleavage and cis-diols/boronic acid conjugation endow the designed method with highly specific detection and cell imaging of enzymatic activity. The cleancap-regulated AIE strategy provides a universal tool for regulation of AIE phenomenon in trace analysis.

Red aggregation-induced emission luminogen and Gd3+ codoped mesoporous silica nanoparticles as dual-mode probes for fluorescent and magnetic resonance imaging

Fluorescence imaging and magnetic resonance imaging have been research hotspots for adjuvant therapy and diagnosis. However, traditional fluorescent probes or contrast agents possess insurmountable weaknesses. In this work, we reported the preparation of dual-mode probes based on mesoporous silica nanomaterials (MSNs), which were doped with an aggregation-induced emission (AIE) dye and Gd3+ through a direct sol-gel method. In this system, the obtained materials emitted strong red fluorescence, in which the maximum emission wavelength was located at 669 nm, and could be applied as effective fluorescence probes for fluorescence microscopy imaging. Furthermore, the introduction of Gd3+ made the nanoparticles effective contrast agents when applied in contrast-enhanced magnetic resonance (MR) imaging because they could improve the contrast of MR imaging. The excellent biocompatibility of these nanoparticles, as demonstrated via a typical CCK-8 assay, and their performance in fluorescence cell imaging and MR imaging shows their potential for applications in biomedical imaging.

Highly photostable ketopyrrolyl-BODIPYs with red aggregation-induced emission characteristics for ultrafast wash-free mitochondria-targeted bioimaging

Subcellular organelle-specific probes, including mitochondria-targeted fluorescent probes, have attracted enormous research interests because they can monitor or visualize the morphology or biological activities of specific organelles and play an indispensable role in disease diagnosis. To follow the process, highly specific and photostable fluorescent probes are in demand. However, commercially available mitochondria probes normally suffer from poor photostability under laser irradiation and aggregation caused quenching (ACQ) in the aggregate state. In this work, two simple aggregation-induced emission(AIE)-active meso-2-ketopyrrolyl BODIPYs were developed via a convenient one-pot synthetic procedure from 2-methylpyrrole and corresponding pyrrolyldiketone in the presence of BF3·OEt2. The two AIE luminogens (AIEgens) both show very weak fluorescence (maximum emission peaks at 545 and 559 nm, respectively) in DMSO and strong near-infrared solid-state emission. The fluorescence was dramatically intensified and redshifted to 635 and 643 nm, respectively, when water fraction was increased up to above 95% in the DMSO/water mixtures. Both AIEgens were found to specifically “light up” the cell mitochondria with high biocompatibility. Interestingly, the staining process can be shortened for less than a minute after the addition of the AIEgens and without the involvement of a washing procedure, indicating an ultrafast and easy-to-operate staining protocol. Furthermore, their fluorescent images in deep tissue penetration were captured with a satisfied signal-to-noise ratio at a depth of 20 and 30 μm along the direction of the z-axis. Importantly, both AIEgens exhibit high photostability under harsh continuous laser irradiation, demonstrating their potential application as in visualizing and tracking specific mitochondria-associated dynamic changes.

Bright red aggregation-induced emission nanoparticles for multifunctional applications in cancer therapy.

Developing multifunctional photosensitizers (PSs) is needed to effectively simplify cancer treatment, but it remains a big challenge. Here, two red-emitting AIE-active, donor–acceptor (D–A) PSs with small ΔEST and their AIE nanoparticles, are rationally designed and synthesized. The PS1 NPs exhibit bright red-emission with high quantum yield, appropriate 1O2 generation ability and good biocompatibility. More importantly, PS1 NPs can strongly light up the cytoplasm by gently shaking the cells for only 5 s at room temperature, indicating ultrafast staining and mild incubation conditions. In vitro and in vivo cell tracing demonstrate that PS1 NPs can track cells over 14 days, and effectively inhibit tumor growth upon irradiation. To the best of our knowledge, this work is the first example of a PS that integrates image-guided PDT, ultrafast staining and long-term tracing functions, demonstrating the “all-in-one” concept which offers great advantages for potential clinical applications.

Hydrophobic carbon dots with blue dispersed emission and red aggregation-induced emission

Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. However, CDs with red or solid-state fluorescence are rarely reported. Herein, through a one-pot solvothermal treatment, hydrophobic CDs (H-CDs) with blue dispersed emission and red aggregation-induced emission are obtained. When water is introduced, the hydrophobic interaction leads to aggregation of the H-CDs. The formation of H-CD clusters induces the turning off of the blue emission, as the carbonized cores suffer from π-π stacking interactions, and the turning on of the red fluorescence, due to restriction of the surfaces’ intramolecular rotation around disulfide bonds, which conforms to the aggregation-induced-emission phenomenon. This on-off fluorescence of the H-CDs is reversible when the H-CD powder is completely dissolved. Moreover, the H-CD solution dispersed in filter paper is nearly colorless. Finally, we develop a reversible two switch-mode luminescence ink for advanced anti-counterfeiting and dual-encryption.