AIEgens for biological process monitoring and disease theranostics

Controlling Size and Fluorescence of Dye-Loaded Polymer Nanoparticles through Polymer Design

Nanoprecipitation is a straightforward yet powerful technique to synthesize polymer nanoparticles loaded with various biologically active compounds or contrast agents. Particle formation in this approach is kinetically controlled, and various assembly parameters have been used to control the size distribution and properties of the formed nanoparticles. Here, the influence of the nature of the polymer on the formation of nanoparticles in nanoprecipitation is studied systematically by varying its hydrophobicity and charge over a broad range. For this, methacrylate copolymers with different types and fractions of hydrophobic, hydrophilic, and charged side groups are synthesized. Nanoprecipitation of these polymers shows that particle size increases with increasing global hydrophobicity of the polymers. At the same time, both hydrophilic and charged groups reduce particle size. In this way, we achieve control over particle size from ∼10 to 200 nm. Furthermore, the effect of the polymer nature on the photophysical properties of nanoparticles loaded with a fluorescent dye, a rhodamine B derivative with a bulky hydrophobic counterion (fluorinated tetraphenylborate), is studied. It is found that the hydrophobic/hydrophilic balance of the polymer modulates to a large extent the spectral properties and fluorescence quantum yield of the dye encapsulated at high concentration, which reflects changes in the dye aggregation within the polymer matrix. Thus, we show how polymer chemistry can tune kinetically controlled formation of nanoparticles and encapsulation of the load. The concepts introduced here should be valuable tools for the design of nanoparticles for imaging and drug-delivery applications.

Use of Nanoparticles in Tissue Engineering and Regenerative Medicine

Advances in nanoparticle (NP) production and demand for control over nanoscale systems have had significant impact on tissue engineering and regenerative medicine (TERM). NPs with low toxicity, contrasting agent properties, tailorable characteristics, targeted/stimuli-response delivery potential, and precise control over behavior (via external stimuli such as magnetic fields) have made it possible their use for improving engineered tissues and overcoming obstacles in TERM. Functional tissue and organ replacements require a high degree of spatial and temporal control over the biological events and also their real-time monitoring. Presentation and local delivery of bioactive (growth factors, chemokines, inhibitors, cytokines, genes etc.) and contrast agents in a controlled manner are important implements to exert control over and monitor the engineered tissues. This need resulted in utilization of NP based systems in tissue engineering scaffolds for delivery of multiple growth factors, for providing contrast for imaging and also for controlling properties of the scaffolds. Depending on the application, materials, as polymers, metals, ceramics and their different composites can be utilized for production of NPs. In this review, we will cover the use of NP systems in TERM and also provide an outlook for future potential use of such systems.

Color-Tunable and Stimulus-Responsive Luminescent Liquid Crystalline Polymers Fabricated by Hydrogen Bonding

Luminescent liquid crystalline polymers (LLCPs) show extensive application potentials, such as liquid crystal displays and circularly polarized luminescence. In this work, we employ a hydrogen-bonding strategy different from the traditional covalent-bonding method to fabricate LLCPs. First, the acceptor and donor of hydrogen bonding, (4,4'-dibutanoxy tetraphenylethylene)-1-pyridine (PTPEC₄) and poly(2-vinyl terephthalic acid) (PPA), respectively, are successfully synthesized. Then, mixtures with different molar ratios ( x's) of PTPEC₄ to PPA are used to prepare a series of LLCPs [denoted as PPA(PTPEC₄) _x]. The resultant LLCPs show a smectic A phase ( x ≥ 0.8), a columnar nematic phase (0.6 ≤ x ≤ 0.05), and an amorphous state ( x = 0.025), depending on the x value. Meanwhile, all polymers exhibit typical aggregation-induced emission behavior. More interestingly, with the variation of the PTPEC₄ content, the series of LLCPs show different colors, that is, the emission peak red shifts from 510 nm ( x = 1.0) to 551 nm ( x = 0.025). Furthermore, because of the reversible protonation effect of the N atom of pyridine in PTPEC₄ by the strong proton acid, PPA(PTPEC₄) _x shows reversible color transformation. This work provides a new method to construct LLCPs with different emission colors and reversible color transformation.

Highly photostable two-photon NIR AIEgens with tunable organelle specificity and deep tissue penetration

Photostability is a particularly important parameter for fluorescence imaging especially long-term dynamic tracking in live samples. However, many organic fluorophores show poor photostability under one-photon and two-photon continuous irradiation. In addition, these traditional fluorophores also suffer from aggregation-caused quenching (ACQ) in aggregate state in insolvable water environment. Therefore, it remains challenging to develop photostable and ACQ-free fluorophores for biological imaging. In this work, we developed two highly photostable aggregation-induced emission luminogens (AIEgens) based on the cyanostilbene core for in vitro and ex vivo bioimaging. These AIEgens named CS-Py⁺SO₃^- and CS-Py⁺ exhibit near-infrared solid-state emission, large Stokes shift (>180 nm), high fluorescence quantum yield (12.8%-13.7%) and good two-photon absorption cross section (up to 88 GM). CS-Py⁺SO₃^- and CS-Py⁺ show specific organelle staining with high biocompatibility in membrane and mitochondria in live cells, respectively. In addition, selective two-photon mitochondria visualization in live rat skeletal muscle tissues with deep-tissue penetration (about 100 μm) is successfully realized by using CS-Py⁺. Furthermore, these AIEgens especially CS-Py⁺ exhibit remarkably high resistance to photobleaching under one-photon and two-photon continuous irradiation. These highly photostable AIEgens could be potentially utilized in visualizing and tracking specific organelle-associated dynamic changes in live systems.

Near-Infrared Organic Fluorescent Nanoparticles for Long-term Monitoring and Photodynamic Therapy of Cancer

Photodynamic therapy (PDT), which utilizes reactive oxygen species to ablate tumor, has attracted much attention in recent years. Photosensitizers with near-infrared (NIR) fluorescence as well as efficient ROS generation ability have been used for precise diagnosis and simultaneous treatment of cancer. However, photosensitizers frequently suffer from low ROS generation ability and NIR fluorescence quenching in aqueous media due to the aggregation.

Methods: We prepare an effective AIE active NIR emissive photosensitizer containing rhodanine as electron acceptor and triphenylvinylthiophene as electron donor is prepared, and encapsulate the corresponding photosensitizer into Pluronic F127 to fabricate NIR organic fluorescent nanoparticles. We then evaluate the NIR fluorescence bioimaging and photodynamic therapy ability of TPVTR dots in vitro and in vivo.

Results: The yielded organic fluorescent nanoparticles exhibit effective ROS generation ability, bright NIR emission, high photostability, and good biocompatibility. Both in vitro and in vivo experiments confirm that NIR organic fluorescent nanoparticles demonstrate good performances in long-term tracing and photodynamic ablation of tumor.

Conclusion: In summary, the synthesized organic fluorescent nanoparticles, TPVTR dots, showed great potentials in long-term cell tracing and photodynamic therapy of tumor. Our study highlights the efficient strategy for developing promising near-infrared organic fluorescent nanoparticles in advancing the field of bioimaging and further image-guide clinical applications.

Facile synthesis of AIEgens with wide color tunability for cellular imaging and therapy

Luminogens with aggregation-induced emission (AIE) characteristics are nowadays undergoing explosive development in the fields of imaging, process visualization, diagnosis and therapy. However, exploration of an AIE luminogen (AIEgen) system allowing for extremely wide color tunability remains challenging. In this contribution, the facile synthesis of triphenylamine (TPA)-thiophene building block-based AIEgens having tunable maximum emission wavelengths covering violet, blue, green, yellow, orange, red, deep red and NIR regions is reported. The obtained AIEgens can be utilized as extraordinary fluorescent probes for lipid droplet (LD)-specific cell imaging and cell fusion assessment, showing excellent image contrast to the cell background and high photostability, as well as satisfactory visualization outcomes. Interestingly, quantitative evaluation of the phototherapy effect demonstrates that one of these presented AIEgens, namely TTNIR, performs well as a photosensitizer for photodynamic ablation of cancer cells upon white light irradiation. This study thus provides useful insights into rational design of fluorescence systems for widely tuning emission colors with high brightness, and remarkably extends the applications of AIEgens.

Impact of Hydrogen Bonding on the Fluorescence of N-Amidinated Fluoroquinolones

The fluorescence properties of AIE-active N-amidinated fluoroquinolones, efficiently obtained by a perfluoroaryl azide-aldehyde-amine reaction, have been studied. The fluorophores were discovered to elicit a highly sensitive fluorescence quenching response towards guest molecules with hydrogen-bond-donating ability. This effect was evaluated in a range of protic/aprotic solvents with different H-bonding capabilities, and also in aqueous media. The influence of acid/base was furthermore addressed. The hydrogen-bonding interactions were studied by IR, NMR, UV/Vis and time-resolved fluorescence decay, revealing their roles in quenching of the fluorescence emission. Due to the pronounced quenching property of water, the N-amidinated fluoroquinolones could be utilized as fluorescent probes for quantifying trace amount of water in organic solvents.

DOX Loaded Aggregation-induced Emission Active Polymeric Nanoparticles as a Fluorescence Resonance Energy Transfer Traceable Drug Delivery System for Self-indicating Cancer Therapy

In this study, an AIE-active polymer (FTP) was successfully prepared and employed to load anti-cancer drug doxorubicin (DOX) for self-indicating cancer therapy via dual FRET process. Our results demonstrated that the FTP polymer could self-assemble into nanoparticles (NPs) in aqueous solutions to give strong fluorescence emission via intramolecular FRET process. The DOX loaded FTP NPs (drug loading content: 21.77%) were homogeneous particles with size around 50 nm and neutral surface charge, which showed preferable colloidal stability, hemolysis and selective drug release with comparable in vivo antitumor effects to DOX·HCl. In particular, the FRET process between FTP (donor) and DOX (acceptor) could serve as indicator for monitoring the in vitro and in vivo drug release profile, which might be a promising platform to realize real-time monitoring of drug localization and release during the delivery process. STATEMENT OF SIGNIFICANCE: 1. An amphiphilic polymer containing aggregation-induced emission segments and polyethylene glycol (PEG) chains (FTP) was firstly synthesized, which is capable of exerting strong fluorescence via intramolecular Förster resonance energy transfer (FRET) in the aggregate state. 2. The FTP polymer could self-assembled into homogeneous nanoparticles in aqueous environment with decent DOX loading capacity. 3. The DOX loaded FTP nanoparticles can afford FRET-traceable monitoring of the drug release both in vitro and in vivo.

Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers

The features of well-conjugated and planar aromatic structures make π-conjugated luminescent materials suffer from aggregation caused quenching (ACQ) effect when used in solid or aggregated states, which greatly impedes their applications in optoelectronic devices and biological applications. Herein, we reduce the ACQ effect by demonstrating a facile and low cost method to co-assemble polycyclic aromatic hydrocarbon (PAH) chromophores and octafluoronaphthalene together. Significantly, the solid photoluminescence quantum yield (PLQYs) for the as-resulted four micro/nanococrystals are enhanced by 254%, 235%, 474 and 582%, respectively. Protection from hydrophilic polymer chains (P123 (PEO₂₀-PPO₇₀-PEO₂₀)) endows the cocrystals with superb dispersibility in water. More importantly, profiting from the above-mentioned highly improved properties, nano-cocrystals present good biocompatibility and considerable cell imaging performance. This research provides a simple method to enhance the emission, biocompatibility and cellular permeability of common chromophores, which may open more avenues for the applications of originally non- or poor fluorescent PAHs.

Fluorescent BF2 complexes of pyridyl-isoindoline-1-ones: synthesis, characterization and their distinct response to mechanical force

Three boron-pyridyl-isoindoline-1-one based dyes (B1, B2, and B3) with varied side groups were synthesized and their mechanochromic fluorescence properties were studied.

Ultrafast labeling and high-fidelity imaging of mitochondria in cancer cells using an aggregation-enhanced emission fluorescent probe

An aggregation-enhanced emission probe was developed for ultrafast labeling and high-fidelity imaging of mitochondria in cancer cells with a high signal-to-noise ratio.

Near-infrared light-regulated cancer theranostic nanoplatform based on aggregation-induced emission luminogen encapsulated upconversion nanoparticles

Photodynamic therapy (PDT) has been widely applied in the clinic for the treatment of various types of cancer due to its precise controllability, minimally invasive approach and high spatiotemporal accuracy as compared with conventional chemotherapy. However, the porphyrin-based photosensitizers (PSs) used in clinics generally suffer from aggregation-caused reductions in the generation of reactive oxygen species (ROS) and limited tissue penetration because of visible light activation, which greatly hampers their applications for the treatment of deep-seated tumors. Methods: We present a facile strategy for constructing a NIR-regulated cancer theranostic nanoplatform by encapsulating upconversion nanoparticles (UCNPs) and a luminogen (2-(2,6-bis((E)-4-(phenyl(40-(1,2,2-triphenylvinyl)-[1,10-biphenyl]-4-yl)amino)styryl)-4H-pyran-4-ylidene)malononitrile, TTD) with aggregation-induced emission (AIEgen) characteristics using an amphiphilic polymer, and further conjugating cyclic arginine-glycine-aspartic acid (cRGD) peptide to yield UCNP@TTD-cRGD NPs. We then evaluated the bioimaging and anti-tumor capability of the UCNP@TTD-cRGD NPs under NIR light illumination in an in vitro three-dimensional (3D) cancer spheroid and in a murine tumor model, respectively. Results: With a close match between the UCNP emission and absorption of the AIEgen, the synthesized NPs could efficiently generate ROS, even under excitation through thick tissues. The NIR-regulated UCNP@TTD-cRGD NPs that were developed could selectively light up the targeted cancer cells and significantly inhibit tumor growth during the NIR-regulated PDT treatment as compared with the cells under white light excitation. Conclusion: In summary, the synthesized UCNP@TTD-cRGD NPs showed great potential in NIR light-regulated photodynamic therapy of deep-seated tumors. Our study will inspire further exploration of novel theranostic nanoplatforms that combine UCNPs and various AIEgen PSs for the advancement of deep-seated tumor treatments with potential clinical translations.

Aggregation-Induced Emission (AIE) Polymeric Micelles for Imaging-Guided Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a noninvasive treatment for selectively killing malignant tumor cells. The photosensitizer is a necessary component of photodynamic nanomedicine. Many efforts have been made to develop new photosensitizers for efficient cancer photodynamic therapy. In this work, we report a novel nano photosensitizer, polymeric micelles (AIE-M) with aggregation induced emission characteristic, for photodynamic cancer therapy. AIE-M with sub-20 nm particle size is prepared by the self-assembly of salicylaldazine-incorporated amphiphilic polymer (AIE-1), which can produce reactive oxygen species (ROS) with light irradiation in solution. After uptake by cancer cells, AIE-M can specially sojourn in plasma membranes of cancer cells at the early stage and predominantly accumulate in the mitochondria of cancer cell at the late stage. The phototoxicity of AIE-M, resulting from the generation of intracellular ROS with light irradiation, can efficiently cause cancer cells death by apoptosis and necrosis. The advantages of AIE-M as a nano photosensitizer include the small size, highly colloidal stability in the process of preparation and storage, and high cell penetration. The ultra-low Critical Micelle Concentration (CMC) of AIE-1, negligible dark toxicity and super phototoxicity of AIE-M suggest its promising potential for image-guided PDT.

Aggregation-Induced Emission Luminogens: Union Is Strength, Gathering Illuminates Healthcare

The rapid development of healthcare techniques encourages the emergence of new molecular imaging agents and modalities. Fluorescence imaging that enables precise monitoring and detection of biological processes/diseases is extensively investigated as this imaging technique has strengths in terms of high sensitivity, excellent temporal resolution, low cost, and good safety. Aggregation-induced emission luminogens (AIEgens) have recently emerged as a new class of emitters that possess several notable features, such as high brightness, large Stokes shift, marked photostability, good biocompatibility, and so on. So far, AIEgens are widely explored and exhibit superb performance in the area of biomedicine and life sciences. Herein, this review summarizes and discusses the recent investigations of AIEgens for in vivo diagnosis and therapy including long-term tracking, 3D angiography, multimodality imaging, disease theranostics, and activatable sensing. Collectively, these results reveal that AIEgens are of great promise for in vivo biomedical applications. It is hoped that this review will lead to new insights into the development of advanced healthcare materials.

Theranostics based on AIEgens

The utilization of luminogens with aggregation-induced emission (AIE) characteristics has recently been developed at a tremendous pace in the area of theranostics, mainly because AIE luminogens (AIEgens) hold various distinct advantages, such as good biocompatibility, excellent fluorescence properties, simple preparation and modification, perfect size of nano-aggregation for enhanced permeability and retention effect, promoted efficiencies of photodynamic and photothermal therapies, efficient photoacoustic imaging, and ready constructions of multimodal imaging and therapy. Significant breakthroughs and developments of theranostics based on AIEgens have been achieved in the past few years, and great progress has been witnessed in many theranostic modalities, indicating that AIEgens remarkably complement conventional theranostic materials and promote the development of theranostics. This review provides theoretical insights into the advantages of AIEgens in theranostics, and systematically summarizes the basic concepts, seminal studies, recent trends and perspectives in theranostics based on AIEgens. We believe that AIEgens would be promising multifunctional theranostic platforms in clinical fields and facilitate significant advancements in this research-active area.

Nonconjugated Fluorescent Molecular Cages of Trinuclear Fluoroborate Complexes with Salicylaldehyde-Based Schiff Base Ligands

Fluorescent organic materials are commonly π-conjugated planar molecules. In the present work, however, we report a novel class of nonconjugated fluorescent molecular cages of trinuclear fluoroborate complexes (nine samples) with salicylaldehyde-based Schiff base ligands. Owing to the stress from lone pair electrons of N atom in the triethylamine bridge, these B(III) complexes exhibit unusual enantiomers with a tripodlike side-single-opening structure. They emit blue, green, and red emission with large Stokes shifts (up to 159 nm) and high fluorescence quantum yields in both solution (up to 0.24) and solid state (up to 0.25), which might contribute to their strong intramolecular hydrogen bonds and weak intermolecular and intramolecular π-π interactions. Combining their advantages of nonconjugation and biocompatibility, these flexible complexes have potential applications in living cell imaging and anion hosts. We have examined the inherent relationships between their chemical structures and emission properties and afforded a new stage for the design of nonconjugated fluorescent fluoroborate complexes.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure-Property Relationships and Applications

Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4-11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure-property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

General and Scalable Approach to Bright, Stable, and Functional AIE Fluorogen Colloidal Nanocrystals for in Vivo Imaging

Fluorescent nanoparticles built from aggregation-induced emission-active organic molecules (AIE-FONs) have emerged as powerful tools in life science research for in vivo bioimaging of organs, biosensing, and therapy. However, the practical use of such biotracers has been hindered owing to the difficulty of designing bright nanoparticles with controlled dimensions (typically below 200 nm), narrow size dispersity and long shelf stability. In this article, we present a very simple yet effective approach to produce monodisperse sub-200 nm AIE fluorescent organic solid dispersions with excellent redispersibility and colloidal stability in aqueous medium by combination of nanoprecipitation and freeze-drying procedures. By selecting polymer additives that simultaneously act as stabilizers, promoters of amorphous-crystalline transition, and functionalization/cross-linking platforms, we demonstrate a straightforward access to stable nanocrystalline FONs that exhibit significantly higher brightness than their amorphous precursors and constitute efficient probes for in vivo imaging of the normal and tumor vasculature. FONs design principles reported here are universal, applicable to a range of fluorophores with different chemical structures and crystallization abilities, and are suitable for high-throughput production and manufacturing of functional imaging probes.

A Facile Approach towards Fluorescent Nanogels with AIE-Active Spacers

A facile and efficient approach for design and synthesis of organic fluorescent nanogels has been developed by using a pre-synthesized polymeric precursor. This strategy is achieved by two key steps: (i) precise synthesis of core⁻shell star-shaped block copolymers with crosslinkable AIEgen-precursor (AIEgen: aggregation induced emission luminogen) as pending groups on the inner blocks; (ii) gelation of the inner blocks by coupling the AIEgen-precursor moieties to generate AIE-active spacers, and thus, fluorescent nanogel. By using this strategy, a series of star-shaped block copolymers with benzophenone groups pending on the inner blocks were synthesized by grafting from a hexafunctional initiator through atom transfer radical copolymerization (ATRP) of 4-benzoylphenyl methacrylate (BPMA) or 2-(4-benzoylphenoxy)ethyl methacrylate (BPOEMA) with methyl methacrylate (MMA) and tert-butyldimethylsilyl-protected 2-hydroxyethyl methacrylate (ProHEMA) followed by a sequential ATRP to grow PMMA or PProHEMA. The pendent benzophenone groups were coupled by McMurry reaction to generate tetraphenylethylene (TPE) groups which served as AIE-active spacers, affording a fluorescent nanogel. The nanogel showed strong emission not only at aggregated state but also in dilute solution due to the strongly restricted inter- and intramolecular movement of TPE moiety in the crosslinked polymeric network. The nanogel has been used as a fluorescent macromolecular additive to fabricate fluorescent film.

Corannulene-Incorporated AIE Nanodots with Highly Suppressed Nonradiative Decay for Boosted Cancer Phototheranostics In Vivo

Fluorescent nanoparticles (NPs) based on luminogens with aggregation-induced emission characteristic (AIEgens), namely AIE dots, have received wide attention because of their antiquenching attitude in emission and reactive oxygen species (ROS) generation when aggregated. However, few reports are available on how to control and optimize their fluorescence and ROS generation ability. Herein, it is reported that enhancing the intraparticle confined microenvironment is an effective approach to advanced AIE dots, permitting boosted cancer phototheranostics in vivo. Formulation of a "rotor-rich" and inherently charged near-infrared (NIR) AIEgen with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] and corannulene-decorated PEG affords DSPE-AIE dots and Cor-AIE dots, respectively. Compared to DSPE-AIE dots, Cor-AIE dots show 4.0-fold amplified fluorescence quantum yield and 5.4-fold enhanced ROS production, because corannulene provides intraparticle rigidity and strong interactions with the AIEgen to restrict the intramolecular rotation of AIEgen to strongly suppress the nonradiative decay and significantly facilitate the fluorescence pathway and intersystem crossing. Thus, it tremendously promotes phototheranostic efficacies in terms of NIR image-guided cancer surgery and photodynamic therapy using a peritoneal carcinomatosis-bearing mouse model. Collectively, it not only provides a novel strategy to advanced AIE dots for cancer phototheranostics, but also brings new insights into the design of superior fluorescent NPs for biomedical applications.

Organic Dye Based Nanoparticles for Cancer Phototheranostics

Phototheranostics, which simultaneously combines photodynamic and/or photothermal therapy with deep-tissue diagnostic imaging, is a promising strategy for the diagnosis and treatment of cancers. Organic dyes with the merits of strong near-infrared absorbance, high photo-to-radical and/or photothermal conversion efficiency, great biocompatibility, ready chemical structure fine-tuning capability, and easy metabolism, have been demonstrated as attractive candidates for clinical phototheranostics. These organic dyes can be further designed and fabricated into nanoparticles (NPs) using various strategies. Compared to free molecules, these NPs can be equipped with multiple synergistic functions and show longer lifetime in blood circulation and passive tumor-targeting property via the enhanced permeability and retention effect. In this article, the recent progress of organic dye-based NPs for cancer phototheranostic applications is summarized, which extends the anticancer arsenal and holds promise for clinical uses in the near future.

A multifunctional luminogen with aggregation-induced emission characteristics for selective imaging and photodynamic killing of both cancer cells and Gram-positive bacteria

The increasing impact of bacteria on cancer progression and treatments has been witnessed in recent years. Insufficient attention to cancer-related bacteria may lead to distant metastasis, poor therapeutic efficiency and low survival rates for cancers. Exploiting new approaches that enable selective imaging and effective killing of cancer cells and bacteria are thus of great value for the battle against cancers. Herein, we report an aggregation-induced emission (AIE) luminogen, namely TPPCN, with intense emission and efficient reactive oxygen species production for fluorescence imaging and killing cancer cells and Gram-positive bacteria. This work not only demonstrates the potential of AIE luminogens in comprehensive cancer treatments but also stimulates the enthusiasm of scientists to design more multifunctional AIE systems for both cancer and bacteria theranostics.

Hydrotalcite monolayer toward high performance synergistic dual-modal imaging and cancer therapy

Recently, theranostic has drawn tremendous attention by virtue of the nanotechnology development and new material exploration. Herein, we reported a novel theranostic system by loading Au nanoclusters (AuNCs) and Chlorin e6 (photosensitizer, Ce6) onto the monolayer nanosheet surface of Gd-doped layered double hydroxide (Gd-LDH). The as-prepared Ce6&AuNCs/Gd-LDH exhibits a largely enhanced fluorescence quantum yield (QY) of 18.5% relative to pristine AuNCs (QY = 3.1%) as well as superior T₁ magnetic resonance imaging (MRI) performance (r₁ = 17.57 mM^-1s^-1) compared with commercial MRI contrast agent (Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Gd-DOTA): r₁ ≈ 3.4 mM^-1s^-1), resulting from a synergistic effect between AuNCs and Gd-LDH. In addition, both in vitro and in vivo therapeutic evaluations demonstrate an efficient dual-modality imaging guided anticancer performance, especially the synergetic enhanced magnetic resonance/fluorescence (MR/FL) visualization of tumor site. Therefore, this work demonstrates a successful paradigm for the design and preparation of LDHs monolayer-based theranostic material, which holds great promises in practical applications.

Self-assembled organic nanorods for dual chemo-photodynamic therapies

Photodynamic therapy (PDT) and chemotherapy have been extensively developed as effective approaches against cancer. Herein, we constructed organic nanorods by rational co-assembly of photosensitizer, di-iodinated borondipyrromethene (BDP-I2), and chemical anticancer drug, paclitaxel (PTX). The physico- and photochemical properties of the obtained nanorods were carefully investigated. BDP-I2 was selected for its high singlet oxygen (1O2) quantum yields. And the corresponding 1O2 generation ability and photodynamic effect were evaluated both in vitro and in vivo. The accelerated endosomal escape of the nanorods induced by the photodynamic effect enhanced the chemotherapeutic efficacy of PTX. We believe that this synergetic nanomedicine represents a new development for antitumor chemophotodynamic therapy.

A fluorescence and UV/vis absorption dual-signaling probe with aggregation-induced emission characteristics for specific detection of cysteine

Biological thiols with similar structures, such as glutathione (GSH), N-acetyl-l-cysteine (NAC), homocysteine (Hcy) and cysteine (Cys), play important roles in human physiology and are associated with different diseases. Thus, the discrimination of these thiols is a great necessity for various biochemical investigations and the diagnosis of related diseases. Herein, we present a new dual-signaling probe consisting of a typical aggregation induced emission fluorogen of a tetraphenylethylene group and 2,4-dinitrobenzenesulfonyl moiety. The probe can be used to selectively and quantitatively detect Cys over a variety of bio-species, including GSH, NAC and Hcy, from both UV/vis absorption and fluorescence channels. The mechanism study showed that the fluorescence and UV/vis absorption were turned on as the probe undergoes displacement of the 2,4-dinitrobenzenesulfonyl group with Cys, where the UV/vis and fluorescence signals originate from the dinitrophenyl-containing compounds and aggregates of TPE-OH, respectively. In addition, the discrimination of Cys was achieved by more rapid intramolecular displacement of sulfur with the amino group of Cys than NAC, Hcy and GSH. Moreover, the probe shows ignorable cytotoxicity against HepG2 cells, which demonstrates the great potential of the probe in selectively detecting Cys in vivo.

A dual-signaling of fluorescence and UV/vis absorption modes for selective and quantitative detection of cysteine over homocysteine, N-acetyl-l-cysteine and glutathione is developed on the basis of aggregation-induced emission (AIE) effect.

A tetraphenylethene and maltoheptaose conjugate with aggregation-induced emission (AIE) characteristic for temperature sensors

An amphiphilic maltoheptaose–tetraphenylethene conjugate exhibits an AIE effect in an aqueous medium and its fluorescence properties show temperature-dependent behavior.

Macrocycles and cages based on tetraphenylethylene with aggregation-induced emission effect

Syntheses, photophysical properties and applications of macrocycles and cages based on tetraphenylethylene with aggregation-induced emission (AIE) effect.

A unimolecular theranostic system with H2O2-specific response and AIE-activity for doxorubicin releasing and real-time tracking in living cells

A theranostic drug delivery system composed of tetraphenyl-ethene (AIEgen), benzyl boronic ester (trigger), and doxorubicin (drug) was designed and synthesized; its utilities for cell imaging, drug delivery tracking, and cancer cell cytociding were evaluated.

A theranostic drug delivery system composed of tetraphenylethene (AIE-gen), benzyl-boronic ester (trigger) and doxorubicin (drug) was synthesized and its functions in cell imaging, drug delivery tracking, and therapeutic effect were evaluated.

Conformation-induced light emission switching of N-acylhydrazone systems

Bis-N-acylhydrazones bearing different substituents were found to display different colour emissions, through ESIPT or AIE, as a result of conformation switching, triggered by physical stimuli.

Aptamer-Decorated Self-Assembled Aggregation-Induced Emission Organic Dots for Cancer Cell Targeting and Imaging

A facile and simple one-step method was developed to fabricate aptamer-decorated self-assembled organic dots with aggregation-induced emission (AIE) characteristics. With integration of the advantages of AIE aggregates with strong emission and the cell-targeting capability of aptamers, the as-prepared Apt-AIE organic nanodots can specifically target to cancer cells with good biocompatibility, high image constrast, and photostability. On the basis of this universal method, a variety of versatile organic fluorescent nanoprobes with high brightness, specific recognition, and clinical-transitional potential could be facilely constructed for biological sensing and imaging applications.

Ionization and Anion-π+ Interaction: A New Strategy for Structural Design of Aggregation-Induced Emission Luminogens

Recent years have witnessed the significant role of anion-π⁺ interactions in many areas, which potentially brings the opportunity for the development of aggregation-induced emission (AIE) systems. Here, a new strategy that utilized anion-π⁺ interactions to block detrimental π-π stacking was first proposed to develop inherent-charged AIE systems. Two AIE-active luminogens, namely, 1,2,3,4-tetraphenyloxazolium (TPO-P) and 2,3,5-triphenyloxazolium (TriPO-PN), were successfully synthesized. Comprehensive techniques such as single-crystal analysis, theoretical calculation, and conductivity measurement were used to illustrate the effects of anion-π⁺ interactions on the AIE feature. Their analogues tetraphenylfuran (TPF) and 2,4,5-triphenyloxazole (TriPO-C) without anion-π⁺ interactions suffered from the aggregation-caused emission quenching in the aggregate state, demonstrating the important role of anion-π⁺ interactions in suppressing π-π stacking. TriPO-PN was biocompatible and could specifically target lysosome in fluorescence turn-on and wash-free manners. This suggested that it was a promising contrast agent for bioimaging.