Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole

In situ dressing based on a D-π-A structured aggregation-induced emission photosensitizer for healing infected wounds

Photodynamic antimicrobial therapy (aPDT) can effectively kill bacteria without promoting drug resistance. However, the phototoxicity of photosensitizers in aPDT against normal cells hinders their practical applications. In this work, we report the utilization of an aggregation-induced emission (AIE)-active photosensitizer, DTTPB, to develop antibacterial dressing for effective eradication of both Gram-positive and Gram-negative bacteria. The D-π-A structure of DTTPB facilitates efficient ROS generation in the aggregate state, addressing the limitations of a traditional photosensitizer. Notably, DTTPB demonstrates good biocompatibility towards normal cells, which minimizes its phototoxicity to normal tissues. To demonstrate its practical implications, DTTPB is combined with Carbomer 940 to create an injectable hydrogel dressing (DTTPB@gel). DTTPB@gel not only adheres to wounds but also maintains the antimicrobial properties of DTTPB, which together contributes to its enhanced wound-healing performance. Biocompatibility and toxicity assessments confirm the safety of this novel material, highlighting its potential as a practical and effective treatment for bacterial infections in wounds. The results underscore the importance of innovative antimicrobial strategies in fighting against antibiotic resistance, paving the way for safer and more effective therapeutic options.

Aggregation-induced emission in novel multilayered 3D polymers: development of a fluorescent probe for selective metal ion detection

This study presents the characterization of a novel multilayered three-dimensional (3D) polymer exhibiting aggregation-induced emission (AIE) properties when excited at a low wavelength of 280 nm. Utilizing fluorescence spectroscopy, we demonstrate that the polymer displays a marked enhancement in luminescence upon aggregation, a characteristic behavior that distinguishes AIE-active materials from conventional fluorophores. Furthermore, we explore the potential application of this multilayered 3D polymer as a fluorescent probe for the selective detection of specified metal ions. By incorporating chelating functional groups into the polymer matrix, we facilitate specific interactions with target metal ions, leading to significant fluorescence intensity changes that correlate with ion concentration. According to their cyclic voltammetry characteristics, the polymers have potential applications in cutting-edge electrical and optoelectronic systems. Our findings indicate that this multilayered 3D polymer serves as an effective fluorescent sensor and offers tunable optical properties, paving the way for innovative applications in environmental monitoring and biomedical diagnostics. The results underscore the utility of AIE-active polymers in developing advanced materials for sensitive and selective detection of metal ions, contributing to the growing field of smart sensing technologies.

Multifunctional luminogens with synergy of aggregation-induced delayed fluorescence, two-photon absorption and photocurrent generation

In this study, we investigated the aggregation-induced delayed fluorescence (AIDF) properties of three luminogens - TN, TA, and TP. Our comprehensive theoretical analysis reveals a significant reduction in the ΔEST in their aggregated or solid-state, activating TADF, on a ∼μs time-scale. Additionally, these luminogens demonstrate two-photon excited anti-Stokes photoluminescence emission and improved photocurrent generation, attributed to their strong charge transfer characteristics and longer singlet exciton lifetimes.

Red/near-infrared (NIR) difluoroboron β-diketonate derivatives with reversible mechanochromism for cellular imaging

Near-infrared (NIR) fluorophores have promoted the development of materials for bioimaging, but traditional NIR dyes usually suffer from aggregation-caused quenching (ACQ), impeding their applications. Herein, we propose two difluoroboron β-diketonate complexes TBO and TBS, consisting a donor-acceptor (D-A) structure with triphenylamine (TPA) moiety as an electron donors and difluoroboron as well as furan or thiophene building block as an electron acceptor. The theoretical calculation and optical data shows that both of them have intramolecular charge transfer (ICT) characteristics. Such ICT characteristics endow them with both solvatochromism and dual-state emission (DSE) properties. In the solvent CH2Cl2, the emission wavelength of TBO ranges from 550 nm to 750 nm, with a low fluorescence quantum yield (Φ = 7.0 %). However, in the less polar solvent hexane, the emission wavelength blue-shifts, with an increased Φ reaching up to 18 %. Moreover, TBO and TBS exhibit mechanochromic characteristics and rare multi-channel fluorescence emission phenomena at solid-state. Their solid-state samples can emit fluorescence in four spectral bands with maximum emission wavelengths at 300 nm, 400 nm, 600 nm, and 770 nm under excitation at 240 nm. These unique optical properties are expected to be utilized for detecting polarity of system and deformation. Moreover, according to the results of cell imaging and flow cytometry, TBO molecular were easily internalized into Hela cells and distributed in the cytoplasm with strong red fluorescence. Therefore, this research inspires more insight into development of NIR luminogens for biomedical imaging.

High-Strength Anisotropic Fluorescent Hydrogel Based on Solvent Exchange for Patterning

Aggregation-induced emission (AIE)-active fluorescent hydrogel materials have found extensive applications in soft robotics, wearable electronics, information encryption, and biomedicine. Nevertheless, it continues to be difficult to create hydrogels that are both highly luminescent and possess strong mechanical capabilities. This study introduces a combined approach of prestretching and solvent exchange to create anisotropic luminous hydrogels made of poly(methacrylic acid-methacrylamide). This method restricts the intrachain rotation of AIE molecules and adjusts the orientation of the polymer network. The increased luminescence and mechanical qualities are determined to be caused by the clustering of AIE molecules, the creation of the associated hydrophobic phase and the asymmetrical polymer network. The fluorescent hydrogels exhibit exceptional mechanical characteristics, including a high fracture stress of 5.97 MPa, an outstanding elastic modulus of 93.97 MPa, and a fracture toughness of 7.21 MJ/m3. Furthermore, the AIE fluorescent hydrogels demonstrate outstanding water retention, antiswelling capabilities, and a writing function for solvent-regulated fluorescent information. This work presents a highly efficient technique for creating anisotropic hydrogels with changeable luminescence properties, which have the potential to be used in several applications, including information encryption, flexible sensors, and soft robots.

Calcium Carbonate as an Ionic Molecular Lock for Ultrastrong Fluorescence of Single Organic Molecules

Locking molecular conformation are widely applied in molecular engineering for improved performance. However, locking via organic functional groups often changes the original molecular properties. Following the rigidity and stability of ionic interaction in ionic compounds, we suggested the use of a molecular-scale ionic compound, calcium carbonate oligomer, as a robust molecular segment to functionalize organic molecules. The rigid structure of the ionic molecular segments locked the organic molecules, which could remarkably limit the intramolecular motion and intermolecular interactions. This ensured a stable and ultrastrong fluorescence of the single organic molecule while preserving its original maximum emission wavelength. The locking strategy was general and extendable to multiple organic molecules. Additionally, the ultrastrong single-molecular fluorescence can be maintained in inorganic solids with even higher quantum yields and almost unchanged maximum emission wavelength. The highest quantum yield of the investigated molecules reached 99.9 %, superior to all reported organic-inorganic fluorescent composite under air conditions. This work demonstrates a general strategy to restrict intramolecular motion and intermolecular interactions by using ionic oligomers as molecular locks, providing an alternative method for realizing ultraemissive molecules. This further demonstrates a fascinating example of molecular engineering in the presence of inorganic ionic molecules.

The Midas Touch by Iridium: A Second Near-Infrared Aggregation-Induced Emission-Active Metallo-Agent for Exceptional Phototheranostics of Breast Cancer

Developing small organic molecular phototheranostic agents with second near-infrared (NIR-II) aggregation-induced emission (AIE) is paramount for the phototriggered diagnostic imaging and synchronous in situ therapy of cancer via an excellent balance of the excited states energy dissipations. In this study, a multifunctional iridium(III) complex is exploited by the coordination of an AIE-active N^N ancillary ligand with a trivalent iridium ion. The resultant complex DPTPzIr significantly outperforms its parent ligand in terms of absorption/emission wavelengths, reactive oxygen species (ROS) production, and photothermal conversion, which simultaneously endow DPTPzIr nanoparticles with matched absorption peak to commercial 808 nm laser, the longest NIR-II emission peak (above 1100 nm) among those previously reported AIE iridium(III) complexes, potentiated type-I ROS generation, and as high as 60.5% of photothermal conversion efficiency. Consequently, DPTPzIr nanoparticles perform well in multimodal image-guided photodynamic therapy-photothermal therapy for breast cancer in tumor-bearing mice, enabling precise tumor diagnosis and complete ablation with high biocompatibility. Our present work provides a simple, feasible, and effective paradigm for the development of advanced phototheranostic agents.

Optimal Method to Realize Quantitative Detection of 1D and 2D Nanoassemblies Based on AIE-Active Bolaamphiphilic Molecules

Controllable transformation between the bolaamphiphilic molecule assemblies with different morphological nanostructures represents an exciting new direction for materials. However, there are still significant challenges for the quantitative detection and real-time monitoring of a controllable nanoself-assembly process due to insufficient measuring methods. Herein, we propose a new and effective fluorescence technology for realizing quantitative detection of a controllable conversion process of one-dimensional (1D)/two-dimensional (2D) nanoassemblies by introducing AIEgens as the fluorescence signal part. First, an aggregation-induced emission (AIE)-active bolaamphiphilic molecule (TPE-C8-Br) was designed and synthesized by incorporating tetraphenylethene (TPE) as the chromophore into the cationic amphiphile. Subsequently, the 1D nanofibrous morphology of TPE-C8-Br was successfully converted into the 2D rectangular and circular sheet of tosylate (TPE-C8-Ts) and sodium 1-hexanesulfonate (TPE-C8-HS) with the same molecular skeleton by the simple counterion change, respectively. Interestingly, all 2D nanoassemblies exhibited a stronger fluorescence sensitization effect than that of the 1D nanoassembly at the concentration above the critical micelle concentration (CMC) due to the higher degree of aggregation; thus, the rotation of the AIE-active TPE moiety is more restricted in TPE-C8-Ts and TPE-C8-HS. More meaningfully, a rather good linear correlation (FI = 3174.86 + 5282.29MP, R2 = 0.999) and a quadratic correlation (FI = 2113.71 + 5163.56MP - 2966.07MP2) were obtained between the molar percentage (MP) of the 2D nanoassembly and the fluorescence intensity (FI). The two proposed methods respond very well with regard to dependability, which can be used for the quantitative calculation of the molar ratio of 1D and 2D components in the controllable nanoself-assembly process. Therefore, this work offers an efficient and practical method for realizing the dynamic monitoring and quantitative detection of mutual conversion between different nanoassemblies.

Aggregation-Induced Emission Luminogens Realizing High-Contrast Bioimaging

A revolutionary transformation in biomedical imaging is unfolding with the advent of aggregation-induced emission luminogens (AIEgens). These cutting-edge molecules not only overcome the limitations of traditional fluorescent probes but also improve the boundaries of high-contrast imaging. Unlike conventional fluorophores suffering from aggregation-caused quenching, AIEgens exhibit enhanced luminescence when aggregated, enabling superior imaging performance. This review delves into the molecular mechanisms of aggregation-induced emission (AIE), demonstrating how strategic molecular design unlocks exceptional luminescence and superior imaging contrast, which is crucial for distinguishing healthy and diseased tissues. This review also highlights key applications of AIEgens, such as time-resolved imaging, second near-infrared window (NIR-II), and the advancement of AIEgens in sensitivity to physical and biochemical cue-responsive imaging. The development of AIE technology promises to transform healthcare from early disease detection to targeted therapies, potentially reshaping personalized medicine. This paradigm shift in biophotonics offers efficient tools to decode the complexities of biological systems at the molecular level, bringing us closer to a future where the invisible becomes visible and the incurable becomes treatable.

Contribution of radiative rate constants to crystallization-induced emission enhancement in boron-fused azobenzene complexes

Analysis of emission enhancement in an aggregated state has been developed by focusing on the suppression of nonradiative processes by intermolecular interactions. On the other hand, it is difficult to evaluate the contribution of radiative processes despite its significant role in improving emission. Herein, the contribution of radiative processes to crystallization-induced emission enhancement (CIEE) is evaluated. By comparing optical properties between isolated and crystalline states at 77 K to minimize the structural relaxation, acceleration phenomena of the radiative process originating from the intermolecular interactions in crystal are clarified. Consequently, it is experimentally proved that a large refractive index in an organic crystal mainly promotes the radiative processes in CIEE even without significant intermolecular electronic interactions.

Self-Assembled Nanohelixes Driven by Host-Guest Interactions and Metal Coordination

Helical nanostructures fabricated via the self-assembly of artificial motifs have been a captivating subject because of their structural aesthetics and multiple functionalities. Herein, we report the facile construction of a self-assembled nanohelix (NH) by leveraging an achiral aggregation-induced emission (AIE) luminogen (G) and pillar[5]arene (H), driven by host-guest interactions and metal coordination. Inspired by the "sergeants and soldiers" effect and "majority rule" principle, the host-guest complexation between G and H is employed to fixate the twisted conformation of G for the generation of "contortion sites", which further induced the emergence of helicity as the 1D assemblies are formed via Ag(I) coordination and hexagonally packed into nano-sized fibers. The strategy has proved feasible in both homogeneous and heterogeneous syntheses. Along with the formation of NH, boosted luminescence and enhanced productivity of reactive oxygen species (ROS) are afforded because of the efficient restriction on G, indicating the concurrent regulation of NH's morphology and photophysical properties by supramolecular assembly. In addition, NH also exhibits the capacity for bacteria imaging and photodynamic antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Time-Encoded Information Encryption with pH Clock Guided Broad-Spectrum Emission by Dynamic Assemblies

With growing threats from counterfeiting-based security breaches, multi-level and specific stimuli-responsive anti-counterfeiting devices and message encryption methods have attracted immense research interest. Fluorescence-based encryption from aggregation-induced emission (AIE)-based materials solves the problems to a considerable extent. However, the development of smarter patterns with hierarchical security levels alongside dynamic display is still challenging. To screen out this complication, we bring forward a pH-switchable fluorescent assembly of an AIEgen and an aliphatic acid. We later temporally direct the molecular assembly with the aid of a chemical trigger-regulated pH clock, generating a transitory multicolor emission, including transient white light generation. The pH-dependent emissions were further implemented in constructing smart multi-input fluorescent chemical AND gates. Subsequently, we integrate the time-gated emissive system to develop an advanced multi-dimensionally secure data encryption strategy. This novel approach enhances anti-counterfeiting measures by introducing an additional layer of security based on temporal characteristics.

Conformation-Confined Organic Butterfly-Molecule with High Photoluminescence Efficiency, Deep-Blue Amplified Spontaneous Emission, and Unique Piezochromic Luminescence

Organic fluorophores with tunable π-conjugated paths have attracted considerable attention owing to their diverse properties and promising applications. Herein, we present a tailored butterfly-like molecule, 2,2'-(2,5-bis (2,2-diphenylvinyl)-1,4-phenylene)dinaphthalene (BDVPN), which exhibits diverse photophysical features in its two polymorphs. The BP phase crystal, with its "aligned wings" conformation, possesses emissive characteristics that are nearly identical to those in dilute solutions. In contrast, the BN phase crystal, which adopts an "orthogonal wings" conformation, exhibits an unusual hypsochromic-shifted emission compared to its dilute solution counterparts. This intriguing hypsochromic-shifted emission originates from the reduction in the effective conjugated length of the molecular skeleton. Notably, BN phase crystals also exhibit exceptional optical performance, featuring high-efficiency emission (76.6 %), low-loss optical waveguides (0.571 dB mm-1), deep-blue amplified spontaneous emission (ASE) with narrow full width at half maximum (FWHM: 6.4 nm), and a unique 200 nm bathochromic shift of piezochromic luminescence.

Tetra-benzimidazoles flanking divinyl-phenothiazine: AIEgens as aza-Michael acceptors in concentration-tuned responses to biogenic amine vapors

Tetra-benzimidazole rotors flanking a divinyl-phenothiazine stator are realized as red AIEgens and newly identified as efficient aza-Michael acceptors for the identification of biogenic amine vapors. Weakly red-emissive solids display a blue-shifted turn-on emission by rapid aza-Michael addition and simultaneous reverse Knoevenagel reactions. Concentration variation imposes better crystallinity and facilitates radiative decay, offering distinct emissions.

Heteroaryl-Fused Triazapentalenes: Synthesis and Aggregation-Induced Emission

A pyridine-fused triazapentalene shows weak fluorescence in solution and is readily accessible via nitrene-mediated cyclization. In this study, a modified Cadogan reaction was used to synthesize HetATAP 1. Palladium-catalyzed reactions have been used as post-functionalization methods. Interestingly, modified Suzuki cross-couplings with various boronic acids resulted in poor to moderate yields of HetATAPs 2-5 which were arylated at the azole moiety. Direct CH arylation of HetATAP 1 gave the products with the same regiochemistry in satisfactory yields. The structures of HetATAPs 2-5 were confirmed using NMR analysis. In addition, the photophysical properties of HetATAPs 1-5 were studied under various conditions. Particularly, the emission of HetATAPs 2-5 is enhanced in the solid and aggregate state.

Charge-transfer mediated J-aggregation in red emitting ultra-small-single-benzenic meta-fluorophore crystals

Red emission in crystals has been observed with an ultra-small-single-benzenic meta-fluorophore (MF) with a molecular weight (MW) of only 197 Da, bettering the literature report of fluorophores with the lowest MW = 252 Da. Supramolecular extensive hydrogen-bonding and J-aggregate type centrosymmetric discrete-dimers or a 1D chain of MFs led to red emission (λ max em = 610-636 nm) in MF crystals. Unlike in the solution phase showing one absorption band, in thin films and in crystals the transition from the S0 state to both the S1 - state and S1 + state becomes feasible. The angle between the transition dipole moments has been obtained to be 66.99° and the exciton splitting energy has been obtained to be (-) 55.7 meV. Significant overlap have been observed and the extent of overlaps integrals between the HOMOs and the LUMOs were assessed to be 0.0068 and (-) 0.00024, respectively. Planar molecules are shown to be involved in anti-parallel stacking with a slip-angle of 44.05° and an inter-planar longitudinal distance of 3.40 Å. A large magnitude of ΔE ES (energy difference between the S1 - state and S1 + state) (0.83 eV) has been obtained. A much higher magnitude of the CT coupling constant (-0.708 for MF2) has been noted in comparison to the coulombic coupling constant (0.016 for MF2). The excited-state-lifetime has been shown to increase from 5.98 ns (in hexane) to 30.90 ns in the crystal. All these extra-ordinary optical properties point to the existence of a charge-transfer mediated J-aggregation phenomenon in these MF crystals. Based on these fascinating observations, highly stable, bright and colour pure white LEDs could be generated.

Trigger inducible tertiary lymphoid structure formation using covalent organic frameworks for cancer immunotherapy

The discovery of tertiary lymphoid structures (TLS) within tumor tissues provides a promising avenue to promote the efficacy of cancer immunotherapy. Yet, the lack of effective strategies to induce TLS formation poses a substantial obstacle. Thus, the exploration of potential inducers for TLS formation is of great interest but remains challenging. Here, inspired by the mechanism of artificially cultivated pearls, a covalent organic framework (COF) is employed to induce TLS formation. Single-cell sequencing analysis reveals that this is achieved by promotion of cytokine hypersecretion, which facilitates the maturation, proliferation, and migration of T and B cells, critical for triggering TLS formation. Furthermore, the efficacy of COF-mediated phototherapy in inducing TLS formation is validated in both the MC38 and 4MOSC1 female tumor models. Notably, a strong synergistic effect between COF-mediated phototherapy and αCTLA-4 is observed, resulting in the effective eradication of both primary and distant tumors, while also inhibiting tumor recurrence.

Nonconventional Fluorescent Non-Isocyanate Polyurethane Foams for Multipurpose Sensing Applications

Fluorescent foams with interconnected pores are attractive for the detection and quantification of various products. However, many fluorescent probes are suffering from aggregation-caused fluorescence quenching in their solid/aggregated state, are costly, and/or not straightforward to incorporate in foams, limiting their utility for this application. Herein, non-isocyanate polyurethane foams, prepared by the simple water-induced self-blowing process, present a nonconventional fluorescence behaviour, i.e. they are intrinsically fluorescent with a multicolor emission without requiring ex situ traditional fluorescent probes. These foams demonstrate utility for capturing-sensing gaseous formaldehyde (an emblematic indoor air pollutant), as well as for detecting and quantifying various metal ions (Fe2+, Cu2+, Fe3+, Hg2+). They are also able to selectively sense tetracycline antibiotic in a ratiometric way with a high sensitivity. By exploiting the unique multicolor photoluminescent foam properties, a smartphone-compatible device is used for the facile antibiotic quantification. This nonconventional fluorescence behaviour is discussed experimentally and theoretically, and is mainly based on clusteroluminescence originating from multiple hydrogen bonding and hetero-atomic sub-luminophores, thus from aggregation-induced emission luminogens that are naturally present in the foams. This work illustrates that easily accessible non-conventional fluorescent NIPU foams characterized by a modular emission wavelength have an enormous potential for multiple substrates detection and quantification.

An AIE-based ratiometric fluorescent probe for highly selective detection of H2S in plant stress responses

Hydrogen sulfide (H2S) has emerged as a crucial signaling molecule in plant stress responses, playing a significant role in regulating various physiological and biochemical processes. In this study, we report an aggregation-induced emission (AIE)-based ratiometric fluorescent probe TPN-H2S for the highly selective detection of H2S in plant tissues. The probe exhibited excellent sensitivity and selectivity towards H2S over other analytes, enabling real-time monitoring of H2S dynamics in living cell. Furthermore, the AIE-based ratiometric probe TPN-H2S allowed for accurate quantification of H2S levels, providing valuable insights into the spatiotemporal distribution of Cys metabolism produces H2S. Importantly, the physiological pathways and signaling mechanisms of H2S production of was investigated in plant tissues under Cr and nano-plastics stress. Utilizing a high-throughput screening approach, we identified exogenous substances such as calcium chloride (CaCl2) and abscisic acid (ABA) that could induce higher level of H2S production during the stress response in plants. Overall, those findings demonstrate the potential of the AIE-based ratiometric fluorescent probe TPN-H2S as a powerful tool for unraveling the role of H2S in plant stress responses and pave the way for further exploration of H2S-mediated signaling pathways in plants.

Highly Selective AIEgen-Based "Turn On" Fluorescent Imaging for Inflammation Detection

Hypochlorous acid (HClO) is released by immune cells in the immune system, and it helps the body fight off infections and inflammation by killing bacteria, viruses, and other pathogens. However, tissue damage or apoptosis may also be induced by excess HClO. On this basis, we designed the probe TPE-NS by choosing tetraphenylethylene (TPE) as the luminescent unit and dimethylthiocarbamoyl chloride as the recognition site. By Gaussian's transition state calculations, HClO will cut off the photoinduced electron transfer (PET) effect of TPE-NS by hydrolysis reaction, thus emitting strong fluorescence. TPE-NS has rapid recognition and excellent specificity for HClO, and the limit of detection is 7.27 μM. Finally, TPE-NS was successfully used for the visualization of endogenous and exogenous HClO in cell experiments.

Photophysical behavior of meso-N-butylcarbazole-substituted BODIPY in different nano-scale organized media

The present work focuses on the photophysical behavior of meso-N-butylcarbazole-substituted BODIPY (CBZ-BDP) in different organized media towards exploring the possible use of the dye as a molecular sensor and imaging agent. The molecule shows an appreciable change in absorption and emission spectra at 75% water-acetonitrile mixture compared to pure acetonitrile. In water-acetonitrile mixture, it displays aggregate-induced emission (AIE) bands. New emission peaks are observed at 560 nm and 630 nm, corresponding to LE (locally excited) and ICT (intramolecular charge transfer) states of CBZ-BDP aggregates. The fluorescence anisotropy studies of CBZ-BDP in glycerol medium show its better sensitivity towards the microenvironment. CBZ-BDP was used to probe various microheterogeneous systems like bile salts, pluronics, and lipid bilayer systems in aqueous medium. The dye displays sensitive variation in emission intensity and fluorescence anisotropy in sodium cholate (NaC) bile salt in aqueous medium as a function of the bile salt concentration. The molecule detects the temperature-induced phase transitions in pluronic P123 and F127, as well as 1,2-dimyristoylphosphatidylcholine (DMPC) and 1,2-dipalmitoylphosphatidylcholine (DPPC) lipid bilayer systems in aqueous medium. These studies strongly suggest that CBZ-BDP can be used as an efficient fluorescent probe in sensing the micro-environmental changes in bile salts, pluronics, and lipid bilayers in aqueous medium. The imaging studies of CBZ-BDP-embedded Giant Unilamellar Vesicles (GUVs) were carried out. The molecule stains the lipid bilayers and displays bright-green fluorescent images, suggesting its potential in lipid bilayer imaging.

Aggregate Science: from Molecules, beyond Molecules

Over the past centuries, molecular science has played a dominant role in the advancement of physical science by exploring the structure-property relationships at a single molecular level. However, when molecules form aggregates, a dilemma arises as the structures and properties often differ significantly from those of molecular constituents. To address this, the concept of aggregate science emphasizes a holistic approach to understanding the structures-properties relationship of substances. Despite the recognition of holism in aggregate research, there are still challenges in investigating the complex operations and interplays, particularly in understanding the newly emergent structures and properties in the macroscopic world. Therefore, there is a need to further advance the concept and methodology. In this regard, this perspective highlights three types of influences that aggregation exerts on substance properties: activation, transformation, and emergence. Furthermore, examples from aggregation-induced emission research and related fields are provided to illustrate how aggregate science can be studied. This perspective emphasizes that the molecule is of significance and the structures and properties are also dramatically influenced by aggregation. Additionally, potential research methodologies, such as focusing on intra- and intermolecular interactions, adjusting aggregates morphology, and regulating the constituents, along with directions, and implications are offered for future studies.

Intracellularly manipulable aggregation of the aggregation-induced emission luminogens

Biophotonics has seen significant advancements with the development of optical imaging techniques facilitating the noninvasive detection of biologically relevant species. Aggregation-induced emission (AIE) materials have emerged as a novel class of luminogens exhibiting enhanced luminescence or photodynamic efficiency in the aggregated state, making them ideal for biomedical applications. The intracellularly controlled aggregation of aggregate-induced emission luminogens (AIEgens) enables high-resolution imaging of intracellular targets and diagnosis of related diseases, and enables disease therapy by exploiting the novel properties of aggregates. This review provides an in-depth analysis of the strategies employed to modulate the aggregation of AIEgens, focusing on the importance of molecular modifications to improve hydrophilicity and achieve precise control over the intercellular aggregation of AIEgens. Furthermore, the representative applications of AIEgens in bioimaging, such as enzyme activity monitoring, protein tracking, organelle function monitoring, and in vivo tumor-specific therapeutics, are reviewed. Additionally, we outline the challenges and future opportunities for AIE research, emphasizing the importance of the strategies for realizing the precisely controllable aggregation of AIEgens inside cells and the need for extending AIEgens' absorption and emission wavelengths. This review aims to elucidate the rational development of responsive AIEgens for advanced biomedical applications.

Amplifying Radiotherapy by Evoking Mitochondrial Oxidative Stress using a High-performance Aggregation-induced Emission Sonosensitizer

INTRODUCTION

Developing effective methods to enhance tumor radiosensitivity is crucial for improving the therapeutic efficacy of radiotherapy (RT). Due to its deep tissue penetration, excellent safety profile, and precise controllability, sonosensitizer-based sonodynamic therapy (SDT) has recently garnered significant attention as a promising combined approach with RT.

METHODS

However, the limited reactive oxygen species (ROS) generation ability in the aggregated state and the absence of specific organelle targeting in sonosensitizers hinder their potential to augment RT. This study introduces a fundamental principle guiding the design of high-performance sonosensitizers employed in the aggregated state. Building upon these principles, we develop a mitochondria-targeted sonosensitizer molecule (TCSVP) with aggregation- induced emission (AIE) characteristics by organic synthesis. Then, we demonstrate the abilities of TCSVP to target mitochondria and produce ROS under ultrasound in H460 cancer cells using confocal laser scanning microscopy (CLSM) and fluorescence microscopy. Subsequently, we examine the effectiveness of enhancing tumor radiosensitivity by utilizing TCSVP and ultrasound in both H460 cells and H460 and 4T1 tumor-bearing mice.

RESULTS

The results indicate that evoking non-lethal mitochondrial oxidative stress in tumors by TCSVP under ultrasound stimulation can significantly improve tumor radiosensitivity (p <0.05). Additionally, the in vivo safety profile of TCSVP is thoroughly confirmed by histopathological analysis.

CONCLUSION

This work proposes strategies for designing efficient sonosensitizers and underscores that evoking non-lethal mitochondrial oxidative stress is an effective method to enhance tumor radiosensitivity.

4,4'-Sulfonyldianiline Derived Aggregation-Induced Emission Luminogen for the Detection of Ofloxacin

The excessive use of antibiotic ofloxacin (Oflx) can cause serious detrimental effects to human health. Therefore, the utmost research priority is required to develop facile methods to detect Oflx. Herein, a V-shaped aggregation-induced emission (AIE) active Schiff base SDANA was introduced for the fluorescent turn-on detection of Oflx. The Schiff base SDANA was synthesized by condensing 4,4'-sulfonyldianiline with two equivalents of 2-hydroxy-1-naphthaldehyde. The nearly non-fluorescent SDANA in DMSO showed strong orange emission with the increase in HEPES buffer (H2O, 10 mM, pH 7.4) fractions in DMSO from 70 %-95 % due to the combined effects of AIE and ESIPT. The DLS and SEM analyses were performed to complement the formation of self-aggregates of SDANA. With the addition of Oflx, the fluorescence emission of AIE luminogen (AIEgen) SDANA (λem=575 nm, λex=400 nm) was blue-shifted and enhanced at 530 nm. The interactions of Oflx over the surface of SDANA aggregates disrupted the intramolecular charge transfer and aggregation morphology of SDANA, which gave a distinct fluorescence response to detect Oflx. The detection limit for Oflx was estimated as 0.81 μM, and the developed probe AIEgen SDANA was applied for the quantification of Oflx in human blood serum.

Sensing the Small Change of Intermolecular Distance in Supramolecular Assembly by Using the Tunable Emission Wavelength of AIE-Active Luminogens

The distinct molecular states - single molecule, assembly, and aggregate - of two ionic macromolecules, TPPE-APOSS and TPE-APOSS, are easily distinguishable through their tunable fluorescence emission wavelengths, which reflect variations in intermolecular distances. Both ionic macromolecules contain aggregation-induced emission (AIE) active moieties whose emission wavelengths are directly correlated to their mutual distances in solution: far away from each other as individual molecules, maintaining a tunable and relatively long distance in electrostatic interactions-controlled blackberry-type assemblies (microphase separation), or approaching van der Waals close distance in aggregates (macrophase separation). Furthermore, within the blackberry assemblies, the emission wavelength decreases monotonically with increasing assembly size, indicative of shorter intermolecular distances at nanoscale. The emission changes of TPPE-APOSS blackberry assemblies can even be visually distinguishable by eyes when their sizes and intermolecular distances are tuned. Molecular dynamics simulations further revealed that macromolecules are confined in various conformations by controllable intermolecular distances within the blackberry structure, thereby resulting in fluorescence emission with tunable wavelength.

Recent advances of lipid droplet-targeted AIE-active materials for imaging, diagnosis and therapy

Lipid droplets (LDs) are cellular organelles specialized in the storage and regulating the release of lipids critical for energy metabolism. As investigation on LDs deepens, the complex biological functions of LDs are revealed and their relationships with various diseases such as atherosclerosis, fatty liver, obesity, and cancer are uncovered. Fluorescence-based techniques with simple operations, visible results and high non-invasiveness are ideal tools for investigating LD-related biological processes and diseases. Materials with aggregation-induced emission (AIE) characteristics have emerged as promising candidates for investigating LDs due to their high signal-to-noise ratio (S/N), strong photostability, and large Stokes shift. This review discusses the principles and advantages of LD-targeting AIE probes for imaging LDs, diagnosis of LD-associated diseases including atherosclerotic plaques, liver diseases, acute kidney diseases and cancer, therapies with LD-targeting AIE-active photosensitizers and other relevant fields in the past five years. Through typical examples, we illustrate the status of investigating LD-related imaging, diagnosis of diseases and therapy with AIE materials. This review is expected to attract attentions from scientists with different research backgrounds and contribute to the further development of LD-targeting AIE materials.

Anticancer behavior of cyclometallated iridium(III)-tributyltin(IV) carboxylate schiff base complexes with aggregation-induced emission

Cyclometallated iridium(III) and organotin(IV) carboxylate complexes have shown potential application value in the field of anticancer. However, the widespread aggregation-caused quenching (ACQ) effect of these complexes is not conducive to the exploration of their targeting and anticancer mechanism, and the idea of aggregation-induced emission (AIE) effect can effectively solve this problem. Then, AIE-activated cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes were designed and prepared in this study. Complexes exhibited AIE effect in highly concentrated solution or aggregative state, which facilitated the investigation of subcellular tissue targeting (mitochondria) and cell morphology. Compared with cyclometallated iridium(III) complex and tributyltin(IV) carboxylate monomers, these complexes showed the better in-vitro anti-proliferative activity toward A549 cells, confirming the favorable synergistic anticancer activity. Even for A549/DDP (cisplatin-resistance) cells, these complexes also exhibited the better activity. In addition, complexes showed a mitochondrial apoptotic pathway. Therefore, cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes can be used as the potential substitutes for platinum-based drugs and gain further application.

Reversible addition-fragmentation chain transfer enhanced aggregation signal-on fluorescence detection of alkaline phosphatase

The instability of the signal intensity of fluorescent biosensors and the false signals have been significant factors affecting the performance of biosensors. Herein, a novel signaling system is devised through the application of reversible addition-fragmentation chain transfer (RAFT) polymerization with monomers containing the tetraphenylethylene (TPE) groups. TPE exhibits an aggregation-induced emission (AIE) phenomenon in certain solvents, mainly due to the blockage of the rotation of its four benzene rings, which also exist in the aggregated state. With this property, a series of molecules are modified based on click chemistry for RAFT polymerization using Fe3O4 magnetic beads as the carriers, and stable aggregated luminescent TPE polymers are formed on the surface of magnetic beads to realize the transformation of fluorescence signal from "0" to "1". In addition, the fluorescence signal demonstrates a positive correlation with alkaline phosphatase (ALP) activity, which can be quantified by measuring the fluorescence intensity. The biosensor exhibits high sensitivity and good linearity in the range of 0.1-5 U/L, with a LOD of 0.079 U/L. Furthermore, the designed strategy demonstrated satisfactory performance in the quantitative determination of ALP activity in serum samples, indicating that the signaling system developed by combining RAFT polymerization and AIE molecules has an important application in the field of fluorescent biosensors.

Deciphering Design of Aggregation-Induced Emission Materials by Data Interpretation

This work presents a novel methodology for elucidating the characteristics of aggregation-induced emission (AIE) systems through the application of data science techniques. A new set of chemical fingerprints specifically tailored to the photophysics of AIE systems is developed. The fingerprints are readily interpretable and have demonstrated promising efficacy in addressing influences related to the photophysics of organic light-emitting materials, achieving high accuracy and precision in the regression of emission transition energy (mean absolute error (MAE) ∼ 0.13eV) and the classification of optical features and excited state dynamics mechanisms (F1score ∼ 0.94). Furthermore, a conditional variational autoencoder and integrated gradient analysis are employed to examine the trained neural network model, thereby gaining insights into the relationship between the structural features encapsulated in the fingerprints and the macroscopic photophysical properties. This methodology promotes a more profound and thorough comprehension of the characteristics of AIE and guides the development strategies for AIE systems. It offers a solid and overarching framework for the theoretical analysis involved in the design of AIE-generating compounds and elucidates the optical phenomena associated with these compounds.

Hydrogen Bond-Mediated Self-Assembly of Carbon Dots Enabling Precise Tuning of Particle and Cluster Luminescence for Advanced Optoelectronic Applications

The effective control over the self-assembly process of carbon dots (CDs) and their cluster luminescence in the aggregated state is of paramount significance and challenge. This study, for the first time, systematically explores the photoluminescent behavior of CDs in their aggregated state, which is less understood compared to their discrete state. By investigating the effects of concentration and solvent environment, it's demonstrated that CDs could exhibit dual emission properties, shifting from blue particle emissions to red cluster emissions as they aggregate. The key to this tunable luminescence lies in hydrogen bonding, which drives the self-assembly of CDs and modulates their photo physical properties. These findings reveal that through precise control of aggregation, CDs can be engineered for advanced optoelectronic applications, including tunable light-emitting diodes (LEDs), secure information encryption, and fingerprint authentication. This report not only deepens the understanding of the underlying mechanisms governing CDs' cluster luminescence but also introduces a novel approach to exploiting their unique properties for technological innovation.

Fluorescent carbon quantum dots for heavy metal sensing

Many heavy metals pose significant threats to the environment and human health. Traditional methods for detecting heavy metals are often limited by complex procedures, high costs, and challenges in field monitoring. Carbon quantum dots (CQDs), a novel class of fluorescent carbon nanomaterials, have garnered significant interest due to their excellent biocompatibility, low cost, and minimal toxicity. This paper reviews the primary synthesis methods, luminescence mechanisms, and fluorescence quenching mechanisms of CQDs, as well as their recent applications in detecting heavy metals. In heavy metal sensing applications, the simplest hydrothermal method is commonly employed for the one-step synthesis and surface modification of CQDs. Various green reagents and biomass materials, such as citric acid, glutathione, orange peel, and bagasse, can be used for CQDs' preparation. Quantum confinement effects and surface defects give CQDs their distinctive luminescence properties, enabling the detection of heavy metals through fluorescence quenching or enhancement. Additionally, CQDs can be applied in biological imaging and smart detection, and when combined with adsorption materials, they can offer multifunctional capabilities. This review also discusses the future development prospects of CQDs.

Enhanced luminescence and stability of TFMDSA nanoparticles via polymer-induced aggregation for bioimaging

In recent years, fluorescence imaging has occupied a very important position in the life science and biomedical fields. However, achieving nanomaterials for bioimaging with both high fluorescence quantum efficiency and high stability remains a significant challenge. Herein, we synthesized mPEG5K-PCL10K@TFMDSA and mPEG5K-PLLA10K@TFMDSA nanoparticles using polymer-induced aggregation. This method significantly enhanced the luminescence efficiency of TFMDSA nanoparticles in solution, attributed to improved intermolecular interactions and restricted molecular vibrations. The resulting nanoparticles exhibited exceptional optical stability over a period of seven days and demonstrated low cytotoxicity towards HeLa cells, making them highly suitable for bioimaging applications. Cellular uptake studies indicated that these nanoparticles were more efficiently internalized by HeLa cells compared to their amorphous counterparts, likely due to their unique square morphology. Our findings highlight the potential of polymer-induced aggregation in enhancing the optical properties and stability of TFMDSA nanomaterials, suggesting their promise as biofluorescent probes for cancer diagnosis and other biomedical applications.

Development and Characterization of Biocompatible Cellulose-Tetraphenylethylene Hydrazone Self-Assembling Nanomicelles with Acidity-Triggered Release of Doxorubicin for Cancer Therapy

The development of anticancer diagnostic and therapeutic strategies is of crucial importance to improve efficacy and therapeutic specificity. Here, we describe the synthesis and characterization of fluorescent self-assembling nanomicelles (NMs) based on a biocompatible polysaccharide (cellulose, CE) functionalized with a tetraphenyl ethylene derivative (TPEHy) and loaded with Doxorubicin (DOX) with aggregation-induced emission (AIE) properties and pH-dependent drug release. We obtained CE-TPEHy-NMs with an average diameter of 60 ± 17 nm for unloaded NMs and 86 ± 25 nm for NMs loaded with DOX, respectively. Upon testing different conditions, we obtained an encapsulation efficiency of 86% and a loading capacity of 90%. A controlled dialysis experiment showed that the release of DOX after 48 h is minimal at pH 7.4 (11%), increasing at pH 6.5 (50%) and at its maximum at pH 4.5 (80%). The cytotoxicity of blank and loaded CE-TPEHy-NMs at increasing concentrations and different pH conditions was tested on a MG-63 human osteosarcoma cell line. Based on viability assays at pH 7.4, neither unloaded nor loaded CE-TPEHy-NMs exerted any inhibition on cell proliferation. At pH 6.5, proliferation inhibition significantly increased, confirming the pH-dependent release. We characterized and studied the performance of CE-based amphiphilic, biocompatible NMs for controlled drug release in acidic conditions, such as tumor microenvironments. Further studies are required to optimize their synthesis process and to validate their antitumoral properties in vivo.

Biomedical applications of the engineered AIEgen-lipid nanostructurein vitroandin vivo

Since the concept of aggregation-induced emission (AIE) was first coined by Tang and co-workers, AIE-active luminogens (AIEgens) have drawn widespread attention among chemists and biologists due to their unique advantages such as high fluorescence efficiency, large Stokes shift, good photostability, low background noise, and high biological visualization capabilities in the aggregated state, surpassing conventional fluorophores. A growing number of AIEgens have been engineered to possess multifunctional properties, including near-infrared emission, two-photon absorption, reactive oxygen species (ROS) generation and photothermal conversion, making them suitable for deep-tissue imaging and phototherapy. AIEgens show great potential in biomedical applicationsin vitroandin vivo. However, despite the favorable photophysical stability and ROS/heat generation capability in the aggregated state, limitations including uncontrolled size, low targeting efficiency, and unexpected dispersion in physiological environments have hindered their biomedical applications. The combination of AIEgens with lipids offers a simple, promising, and widely adopted solution to these challenges. This review article provides an overview of the synthesis methods of AIEgen-lipid nanostructures and their applications in the biomedical engineering field, aiming to serve as a guideline for developing these AIEgens-lipid nanostructures with promising biological applications.

Creation of Excitation-Driven Hypervalent Tin(IV) Compounds For Aggregation-Induced Emission and Application to Thermoresponsive Luminescent Films Below Freezing Point

Although many researchers have devoted their much effort to establish the strategy for developing a stimuli-responsive molecule and tuning of their properties according to the preprogrammed design, it is still challenging to create desired molecules from the scratch. We recently demonstrated that the molecules with a large structural difference between the theoretically optimized structures in the ground and excited states have a potential to exhibit stimuli-responsive luminescent properties. We defined these molecules as an excitation-driven molecule and have shown that they are a versatile platform for designing stimuli-responsive luminescent molecules. Herein, based on the concept of excitation-driven molecules, we show that the hypervalent tin-fused azomethine (TAm) compounds possessing aggregation-induced emission (AIE) properties can be obtained by simple chemical modification with a methyl group although conventional TAm derivatives are well known to be highly luminescent compounds in solution. Furthermore, by combining the solid-state luminescence property of AIE and the coordination number shifts of the hypervalent tin atom, the thermoresponsive films operating below the freezing point are fabricated with the polymer. In this study, we apply the concept of excitation-driven molecules to the hypervalent compounds and demonstrate to obtain the novel functional materials.

Full-color peptide-based fluorescent nanomaterials assembled under the control of amino acid doping

Peptide-based biofluorescents are of great interest due to their controllability and biocompatibility, as well as their potential applications in biomedical imaging and biosensing. Here, we present a simple approach to synthesizing full-color fluorescent nanomaterials with broad-spectrum fluorescence emissions, high optical stability, and long fluorescence lifetimes. By doping amino acids during the enzyme-catalyzed oxidative self-assembly of tyrosine-based peptides, we can precisely control the intermolecular interactions to obtain nanoparticles with fluorescence emission at different wavelengths. The synthesized peptide-based fluorescent nanomaterials with excellent biocompatibility and stable near-infrared fluorescence emission were shown to have potential for bioimaging applications. This research provides new ideas for the development of new bioluminescent materials that are cost-effective, environmentally friendly, and safe for biomedical use.

Disulfide-Bridged Cationic Dinuclear Ir(III) Complex with Aggregation-Induced Emission and Glutathione-Consumption Properties for Elevating Photodynamic Therapy

The ability of photosensitizers (PSs) to generate reactive oxygen species (ROS) is crucial for photodynamic therapy (PDT). However, many traditional PSs face the drawbacks that aggregation-caused quenching (ACQ) and highly expressed glutathione (GSH) in the tumor microenvironment seriously limit their ROS generation ability. Herein, we report two cationic dinuclear iridium complexes, Ir-C-C-Ir and Ir-S-S-Ir, which possess aggregation-induced emission (AIE). Ir-S-S-Ir was constructed for GSH consumption by introducing a disulfide linkage between the two auxiliary ligands with imine units. Quantum chemical calculations revealed that Ir-C-C-Ir and Ir-S-S-Ir possess many degenerate states, which provide more channels for singlet-to-triplet exciton transitions, and then the intersystem crossing rate is increased due to the heavy atom effect of the iridium and sulfur atoms. The ROS production experiments indicated that the singlet oxygen yield of Ir-S-S-Ir was 33 times more than that of the ACQ mononuclear iridium complex Ir-C. Most importantly, Ir-S-S-Ir consumed GSH through a thiol-disulfide exchange reaction, as demonstrated by mass spectrometry and high-performance liquid chromatography. Cell experiments testified that Ir-S-S-Ir consumes GSH in tumor cells, possesses good ROS production capacity, and exhibits an extraordinary PDT effect. This is the first report of an AIE dinuclear iridium complex with a GSH-consuming function.

Aggregation-induced emission: Application in diagnosis and therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious health issue due to its low early diagnosis rate, resistance to chemotherapy, and poor five-year survival rate. Therefore, it is crucial to explore novel diagnostic and therapeutic approaches tailored to the characteristics of HCC. Aggregation-induced emission (AIE) is a phenomenon where the luminescence of certain molecules, typically non-luminescent or weakly luminescent in solution, is significantly enhanced upon aggregation. AIE has been extensively applied in bioimaging, biosensors, and therapy. Fluorophore materials based on AIE (AIEgens) have a wide range of application scenarios and potential for clinical translation. This review focuses on recent advances in AIE-based strategies for diagnosing and treating HCC. First, the specific functional mechanism of AIE is described. Next, we summarize recent progress in the application of AIE for multimodal imaging, biosensor detection, and phototherapy. Finally, prospects and challenges for the AIE-based application in the diagnosis and therapy of HCC are discussed.

AIE-active large Stokes-shift BODIPY Functionalized with Carbazolyl for Lysosome-Targeted Imaging in Living Cells

A large number of studies have shown that lysosomal microcircumstances changes can affect many physiological and pathological processes at the cellular level. However, the visual detection of lysosomal microcircumstances is relatively difficult due to low pH (4.5-6.0) value in lysosomal that require the probe not only stable under acidic condition but also has a good localization effect to lysosomal. Obviously, novel fluorescent which possessed both acidic stability and lysosomal-target property together with lysosomal viscosity active is highly demanded. Herein, a novel BODIPY molecular CarBDP based on carbazole group was rationally designed and synthesized for the lysosomal imaging. CarBDP exhibited AIE feature with a large Stokes shift of up to 157 nm. More importantly, co-localization assay of the CarBDP-treated MCF-7 cells indicated that CarBDP has a good localization effect on lysosomal (Rr = 0.7109) due to the carbazole group while the normal BODIPY that without carbazole group (PhBDP) shows poor localization performance, this was the first time that a small molecule can locate lysosomes only based on carbazole group. CarBDP exhibits strong solid emission with long fluorescence decay lifetime (τ = 44.54 ns) and was stable under acid condition.The probe CarBDP assembled with carbazole group was successfully utilized for lysosomal localization and mapping lysosomal viscosity in live cells, which provides a novel candidate tool for the determination of lysosomal microcircumstances.

Construction of Heterogeneous Aggregation-Induced Emission Microspheres with Enhanced Multi-Mode Information Encryption

Traditional organic light-emitting materials hinder their anti-counterfeiting application in solid state due to their aggregation-caused quenching effect. A facile and straightforward method was reported to introduce AIE molecules into microspheres and manipulate different reaction parameters to prepare AIE microspheres with different morphologies. In this strategy, fluorescent microspheres with spherical, apple-shaped, and hemoglobin-like types were synthesized. Driven by the photocyclization and oxidation of tetraphenylethene, microspheres can be used as an aqueous fluorescence ink with erasable properties. The fluorescent patterns printed by microsphere ink on paper can be irreversibly erased by prolonged exposure to ultraviolet light (365 nm, 60 mw/cm2). Moreover, the multi-morphology microspheres can be further arranged for multiple-information encryption and anti-counterfeiting of barcodes and two-dimensional codes, in which double validation was carried out through fluorescence spectroscopy and laser confocal microscopy. This approach provides a new method for more reliable anti-counterfeiting and information encryption.

Single-Molecule Resolved Conformational and Orbital Symmetry Breaking in Tetraphenylethylene-Based Macrocycles

Tetraphenylethylene (TPE) is a prototype aggregate-induced emission molecule. TPE-based conjugated macrocycles exhibit unique optical properties due to their peculiar cyclic topology. Because the symmetry of macrocycles strongly affects their photophysical properties, here we report a single-molecule study of the structures and orbitals of two TPE-based macrocycles of (C26H18)4 and (C26H18)6. Using scanning tunneling microscopy and spectroscopy, we discover that both macrocycles undergo spontaneous symmetry breaking in their conformations and frontier orbitals. The computational analyses reveal that the symmetry breaking is driven by a subtle interplay of higher extended conjugation between phenyl and node carbon atoms and conformation flexibility of the macrocycles. The observed symmetry breaking in TPE-based macrocycles is expected to strongly alter their photophysical properties.

Porous organic cages as inhibitors of Aβ42 peptide aggregation: a simulation study

The aggregation of Aβ monomers into oligomers with β-sheet structures is an important cause of Alzheimer's disease (AD), while the Aβ42 peptide is more toxic and prone to aggregate. It is of great significance to study the inhibition mechanism of Aβ42 monomer aggregation and find excellent inhibitors for the treatment of AD. Research in recent years has focused on small molecule compounds and nanoparticles, but they all have certain limitations. As a new type of porous material, a porous organic cage (POC) has potential application feasibility in the biomedical field due to its unique physicochemical properties. In this work, molecular dynamics simulations were used for the first time to explore the interaction and conformational transformation of the Aβ42 peptide in CC3 crystals with different morphologies (planar and spherical). The results show that the adsorption of the Aβ42 peptide on different CC3 crystals is mainly achieved through strong van der Waals forces. During the simulations, the Aβ42 peptide undergoes various degrees of structural changes. Compared to that in water, this binding induces more irregular structures, such as turns and 3-helices, and inhibits the production of β-sheets, while enhancing the overall backbone rigidity of the Aβ42 peptide. The transformation analysis of peptide conformation is further complemented by free energy landscape and cluster analysis. These findings provide a strong basis for CC3 crystals as novel inhibitors to inhibit the toxicity and aggregation of the Aβ42 peptide.

An Acid-Resistant Lanthanide Metal-Organic Framework Based on Tetraphenylethylene as an Electrochemical Nitrite Sensor

Nitrite (NO2-) is attracting increasing attention due to its harmful effect on human health. Thus, it is highly desirable to construct effective electrochemical sensors to detect the presence of NO2-. The majority of electrochemical NO2- detection is focused on alkaline or neutral electrolyte solutions and is rarely reported under acidic conditions. In this work, a tetraphenylethylene (TPE)-based 2D lanthanide metal-organic framework (Ln-MOF), (Me2NH2)[HoIII(tcbpe-F)DMF]•DMF•H2O (1) (tcbpe-F = 4',4‴,4″‴,4″″‴-(ethene-1,1,2,2-tetrayl)tetrakis(3-fluoro-[1,1'-biphenyl]-4-carboxylic acid, DMF = N,N-dimethylformamide)), has been successfully fabricated on carbon paper (CP) by an in situ hydrothermal method. As a NO2- sensor, the fabricated 1 electrode exhibited excellent electrochemical performance in the H2SO4 electrolyte (pH = 1) and offers high sensitivities of 1453.2 and 591.5 μA mM-1 cm-2, with a wide linear detection range of 0.1 μM to 9 M, a low detection limit of 60 nM, excellent specificity even in the presence of various analytes (metal ions, anions, and organic molecules) and real water samples, satisfactory stability, and reproducibility. This is the first report of TPE-based Ln-MOF as a NO2- sensor, and furthermore, a plausible sensing mechanism is confirmed by experiments and theoretical computations.

Two AIE-active Schiff base fluorescent probes for highly selective recognition of Cu2+ ions

Two helical Schiff base compounds (H4TPA and H4TPE) containing a triphenylamine (TPA) or tetraphenylethylene (TPE) scaffold were successfully synthesized and characterized. Both H4TPA and H4TPE exhibited typical aggregation-induced emission characteristics in the mixed solvent of THF/H2O. The two compounds also showed high selectivity and sensitivity for the recognition of Cu2+ over other ions in THF/HEPES (1:4, V/V, pH = 7.4, 2.0 × 10-5 M), and could be used as turn-off fluorescent probes for Cu2+. The stoichiometric ratios and association constants were estimated via Job's plots and UV-vis spectra titration, and the detection limits of H4TPA and H4TPE toward Cu2+ were calculated to be 2.41 × 10-7 M and 1.38 × 10-7 M, respectively. Besides, the crystal structure of the complex obtained from the interaction of H4TPA with Cu2+ well illustrated the binding modes, which helped us understand the Cu2+ recognition mechanism of H4TPA and H4TPE. Moreover, the detection of Cu2+ and spiked recovery experiments were carried out, which indicated that the two probes can be applied to Cu2+ detection in real samples with satisfactory recoveries.

J-aggregates of strong electron-donating groups linked Aza-BODIPY adjusting by polypeptide for NIR-II phototheranostics

The commonly employed strategies for engineering second near-infrared (NIR-II) organic phototheranostic agents are based on expanding conjugated backbone length, strengthening donor (D)-acceptor (A) effect, or forming J-aggregates. We constructed the D-A-D' structure by incorporating strong electron-donating methoxy and tetraphenylethene (TPE) moieties on the electron-deficient Aza-BODIPY core, and simultaneously expanded the π-conjugation effect by introducing thiophene groups, to obtain a dye BDP-TPE. Next, the nanoparticles P-TPE were prepared via the assembly of BDP-TPE with amphiphilic polypeptides (mPEG2000-P(Asp)10), and successfully constructed the J-aggregates. The obtained P-TPE exhibited strong absorption and fluorescence with maxima at 808 and 1018 nm, respectively, with a conspicuous absolute quantum yield of 0.241 %. Moreover, P-TPE also showed excellent biocompatibility, and high photothermal conversion efficiency of 61.15 %, and excellent resistance to pH, long-term storage, and photobleaching. In vitro and in vivo experiments revealed that P-TPE exhibited good biocompatibility and effectively achieved NIR-II fluorescence imaging-guided PTT with complete tumor ablation under 808 nm laser irradiation. These results provided good evidence for the use of P-TPE as a NIR-II fluorescence imaging-guided PTT therapeutic agent in vivo.

Advanced Nanoplatform Mediated by CRISPR-Cas9 and Aggregation-Induced Emission Photosensitizers to Boost Cancer Theranostics

Immunotherapy combined with phototherapy is emerging as a promising strategy to treat omnipotent cancers. In this study, a clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system, aggregation-induced emission (AIE) photosensitizer (PS) and surface coating of polyethylene imine/hyaluronic acid were combined to construct a multifunctional nanoplatform, denoted as TCPH nanoparticles (NPs), for comprehensive cancer theranostics. TCPH NPs are featured by intrinsic functions including efficient reactive oxygen species (ROS) production, good photothermal conversion, programmed death-ligand 1 (PD-L1)-eliminating capability, and effective intracellular transport. The generated ROS and hyperthermia do not only achieve primary tumor elimination but also regulate the tumor immune microenvironment. Genomic disruption of PD-L1 conspicuously augments its therapeutic efficacy, especially in tumor metastasis and recurrence. Exceptional multimodal imaging navigation has also been developed. Excellent theranostics performance was substantiated in diverse tumor models, implying that this synergistic strategy of phototheranostics and immunotherapy provides a paradigm shift in emerging CRISPR-mediated nanomedicines.

Recent Progress of Photoswitchable Fluorescent Diarylethenes for Bioimaging

Photochromic diarylethene has attracted broad research interest in optical applications owing to its excellent fatigue resistance and unique bistability. Photoswitchable fluorescent diarylethene become a powerful molecular tool for fluorescence imaging recently. Herein, the recent progress on photoswitchable fluorescent diarylethenes in bioimaging is reviewed. We summarize the structures and properties of diarylethene fluorescence probes and emphatically introduce their applications in bioimaging as well as super-resolution imaging. Additionally, we highlight the current challenges in practical applications and provide the prospects of the future development directions of photoswitchable fluorescent diarylethene in the field of bioimaging. This comprehensive review aims to stimulate further research into higher-performance photoswitchable fluorescent molecules and advance their progress in biological application.

Role of Dark States and Stokes Shift Simulations for Tetraphenylpyrazine Compared to Other Donor-Acceptor Photosensitizers

An excellent agreement for simulated and measured absorption and emission spectra is found for four donor-acceptor aromatic molecules (tetraphenylpyrazine, tetraphenylethene, distirylanthracene and hexaphenylsilole) whose derivatives serve as solid state photosensitizers. After comparing several hybrid TDDFT functionals, EOM-CCSD, and experiments, the best agreement was found with TD-B3LYP and double zeta basis sets (6-31G** and def2-SVP) for one molecule in gas phase. A full characterisation of twelve to twenty electronic excited states was performed in every system. Symmetry-forbidden bands are found in the absorption spectra by sampling fifty to hundred geometries from a Wigner distribution. The density of states in the region 2-6 eV was also analysed, showing a very packed region of excited states and suggesting that dark electronic states may play a role in the dynamics of some of the photoexcited systems. Further calculations were done with QM/xTB at geometries extracted from previously published X-ray data to evaluate the influence of the environment on the excitations of the four aggregated molecular crystals.