AIE-active theranostic system: selective staining and killing of cancer cells

Visualized Enzyme-Activated Fluorescence Probe for Accurately Detecting β-Gal in Living Cells and BALB/c Nude Mice

Colorectal cancer was one of the major malignant tumors threatening human health and β-Gal was recognized as a principal biomarker for primary colorectal cancer. Thus, designing specific and efficient quantitative detection methods for measuring β-Gal enzyme activity was of great clinical test significance. Herein, an ultrasensitive detection method based on Turn-on fluorescence probe (CS-βGal) was reported for visualizing the detection of exogenous and endogenous β-galactosidase enzyme activity. The test method possessed a series of excellent performances, such as a significant fluorescence enhancement (about 11.3-fold), high selectivity as well as superior sensitivity. Furthermore, under the optimal experimental conditions, a relatively low limit of detection down to 0.024 U/mL was achieved for fluorescence titration experiment. It was thanks to the better biocompatibility and low cytotoxicity, CS-βGal had been triumphantly employed to visual detect endogenous and exogenous β-Gal concentration variations in living cells with noteworthy anti-interference performance. More biologically significant was the fact that the application of CS-βGal in BALB/c nude mice was also achieved successfully for monitoring endogenous β-Gal enzyme activity.

A near-infrared aggregation-induced emission photosensitizer targeting mitochondria for depleting Cu2+ to trigger light-activated cancer cells oncosis

Abnormally high levels of copper in tumors stimulate malignant proliferation and migration of cancer cells, which proposes a formidable challenge for the thorough therapy of malignant tumors. In this work, we developed a reliable, mitochondria-targeted near-infrared aggregation-induced emission fluorescent probe, TTQ-Th, whose thiourea moiety specifically could recognize mitochondria even both upon loss of mitochondrial membrane potential or in fixated cells, and can capture copper overexpressed by tumor cells, leading to severe copper deficiency. In parallel, TTQ-Th can generate sufficient reactive oxygen species (ROS) upon photoexcitation, while copper deficiency inhibits expression of related copper-based enzymes, resulting in a decline in ATP production. Such energy deficiency, combined with reduced MMP and elevated oxidative stress can lead to critical cell oncosis. Both in vitro and intracellular experiments can illustrate that the elevated ROS has remarkable damage to tumor cells and contributes to the elimination of the primary tumor, while copper deficiency further hinder tumor cell migration and induces G0/G1 cell cycle arrest in a dose-dependent manner, which is an efficacious strategy for the treatment of malignant tumors.

Cancer-cell-specific Self-Reporting Photosensitizer for Precise Identification and Ablation of Cancer Cells

Cancer-cell-specific fluorescent photosensitizers (PSs) are highly desired molecular tools for cancer ablation with minimal damage to normal cells. However, such PSs that can achieve cancer specification and ablation and a self-reporting manner concurrently are rarely reported and still an extremely challenging task. Herein, we have proposed a feasible strategy and conceived a series of fluorescent PSs based on simple chemical structures for identifying and killing cancer cells as well as monitoring the photodynamic therapy (PDT) process by visualizing the change of subcellular localization. All of the constructed cationic molecules could stain mitochondria in cancer cells, identify cancer cells specifically, and monitor cancer cell viability. Among these, IVP-Br has the strongest ability to produce ROS, which serves as a potent PS for specific recognition and killing of cancer cells. IVP-Br could translocate from mitochondria to the nucleolus during PDT, self-reporting the entire therapeutic process. Mechanism study confirms that IVP-Br with light irradiation causes cancer cell ablation via inducing cell cycle arrest, cell apoptosis, and autophagy. The efficient ablation of tumor through PDT induced by IVP-Br has been confirmed in the 3D tumor spheroid chip. Particularly, IVP-Br could discriminate cancer cells from white blood cells (WBCs), exhibiting great potential to identify circulating tumor cells (CTCs).

Construction of aggregation-induced emission photosensitizers through host-guest interactions for photooxidation reaction and light-harvesting

In the present work, we have designed and synthesized a triphenylamine modified cyanophenylenevinylene derivative (TPCI), which can self-assembly with cucurbit[6]uril (CB[6]) and cucurbit[8]uril (CB[8]) through host-guest interactions to form supramolecular complexes (TPCI-CB[6]) and supramolecular polymers (TPCI-CB[8]) in the aqueous solution. The supramolecular assemblies of TPCI-CB[6] and TPCI-CB[8] not only exhibited high singlet oxygen (1O2) production efficiency as photosensitizers, but also realized the application in the construction of artificial light-harvesting systems due to the excellent fluorescence properties in the aqueous solution. The production efficiency of 1O2 has been effectively improved after the addition of CB[6] and CB[8] for TPCI, which were applied as efficient photosensitizers in the photooxidation reactions of thioanisole and its derivatives with the highest yield of 98% in the aqueous solution. The excellent fluorescence properties of TPCI-CB[6] and TPCI-CB[8] can be used as energy donors in artificial light-harvesting systems with energy acceptors sulforhodamine 101 (SR101) and cyanine dye 5 (Cy5), in which one-step energy transfer processes of TPCI-CB[6]+SR101 and TPCI-CB[8]+Cy5, and a two-step sequential energy transfer process of TPCI-CB[6]+SR101+Cy5 were constructed to simulate the natural photosynthesis system.

Integrating Anion-π+ Interaction and Crowded Conformation to Develop Multifunctional NIR AIEgen for Effective Tumor Theranostics via Hippo-YAP Pathway

The technology of aggregation-induced emission (AIE) presents a promising avenue for fluorescence imaging-guided photodynamic cancer therapy. However, existing near-infrared AIE photosensitizers (PSs) frequently encounter limitations, including tedious synthesis, poor tumor retention, and a limited understanding of the underlying molecular biology mechanism. Herein, an effective molecular design paradigm of anion-π+ interaction combined with the inherently crowded conformation that could enhance fluorescence efficacy and reactive oxygen species generation was proposed through a concise synthetic method. Mechanistically, upon photosensitization, the Hippo signaling pathway contributes to the death of melanoma cells and promotes the nuclear location of its downstream factor, yes-associated protein, which regulates the transcription and expression of apoptosis-related genes. The finding in this study would trigger the development of high-performance and versatile AIE PSs for precision cancer therapy based on a definite regulatory mechanism.

Precise visualization and ROS-dependent photodynamic therapy of colorectal cancer with a novel mitochondrial viscosity photosensitive fluorescent probe

BACKGROUND

Colorectal cancer (CRC) is a prominent global cancer with high mortality rates among human beings. Efficient diagnosis and treatment have always been a challenge for CRC management. Fluorescence guided cancer therapy, which combines diagnosis with therapy into one platform, has brought a new chance for achieving precise cancer theranostics. Among this, photosensitizers, applied in photodynamic therapy (PDT), given the integration of real-time imaging capacity and efficacious treatment feasibility, show great potential to serve as remarkable tools. Although much effort has been put into constructing photosensitizers for locating and destroying CRC cells, it is still in high need to develop novel photosensitizers to attain specific detection and fulfil effective therapy.

METHODS

Probe HTI was rational synthesized for the diagnosis and treatment of CRC. Spectrometric determination was carried out first, followed by the 1O2 generation ability test. Then, HTI was displayed in distinguishing CRC cells from normal cells Further, the PDT effect of the photosensitizer was studied in vitro. Additionally, HTI was used in CRC BALB/c nude mice model to validate its viscosity labelling and tumor suppression characteristics.

RESULTS

We successfully fabricated a mitochondrial targeting probe, HTI, together with remarkable viscosity sensitivity, ultralow background interference, and excellent 1O2 generation capacity. HTI was favorably applied to the viscosity detection, displaying a 11-fold fluorescent intensity enhancement in solvents from 1.57 cp to 2043 cp. Then, it was demonstrated that HTI could distinguish CRC cells from normal cells upon the difference in mitochondrial viscosity. Moreover, HTI was qualified for producing 1O2 with high efficiency in cells, supported by the sparkling signals of DCFH after incubation with HTI under light irradiation. More importantly, the viscosity labelling and tumor suppression performance in CRC CDX model was determined, enriching the multifunctional validation of HTI in vivo.

CONCLUSIONS

In this study, HTI was demonstrated to show a sensitive response to mitochondrial viscosity and possess a high 1O2 generation capacity. Both in vitro cell imaging and in vivo tumor treatment trials proved that HTI was effectively served as a robust scaffold for tumor labeling and CRC cells clearance. This breakthrough discovery held immense potential for advancing the early diagnosis and management of CRC through PDT. By leveraging HTI's properties, medical professionals could benefit from improved diagnostic accuracy and targeted treatment in CRC management, ultimately leading to enhanced patient outcomes.

Diaroyl-S,N-ketene Acetals: Red-Shifted Solid-State and Aggregation-Induced Emitters from a One-Pot Synthesis

Symmetric and unsymmetric diaroyl-S,N-ketene acetals can be readily accessed in consecutive syntheses in good to excellent yields by exploiting the inherent nucleophilic character of the methine position. Different aroyl-S,N-ketene acetals as well as acid chlorides yield a library of 19 diaroyl compounds with substitution and linker pattern-tunable emission properties, leading to a significant red-shift of emission in the solid and aggregated state, which was thoroughly investigated. Additionally, the stability of the luminescent aggregates is highly increased. In a follow-up one-pot procedure, pyrazolo-S,N-ketene acetals can easily be accessed employing a nucleophilic cyclocondensation.

Tandem C-H Annulation Reaction of Benzaldehydes and Aminobenzoic Acids with Two Equivalents of Alkyne toward Isocoumarin-Conjugated Isoquinolinium Salts: A Family of Organic Luminophores

A novel rhodium-catalyzed tandem C-H annulation of commercially available benzaldehydes and aminobenzoic acids with 2 equiv of alkyne is reported for the construction of isocoumarin-conjugated isoquinolinium salts that demonstrate diverse outstanding photoactivity. Depending on the substituents in the isoquinolinium moiety, they display either highly efficient fluorescence (up to 99% of quantum yield) or strong fluorescence quenching, which is provided by the transfer of the HOMO from the isoquinolinium to the isocoumarin moiety. Importantly, the functional groups in the benzaldehyde coupling partner also strongly affect the reaction selectivity, shifting the pathway to the formation of the photoinactive isocoumarin-substituted indenone imines and indenyl amines. Selective formation of the latter can be achieved by using a reduced amount of the oxidizing additive.

Photosensitizer-based small molecule theranostic agents for tumor-targeted monitoring and phototherapy

Small molecule theranostic agents for tumor treatment exhibited triadic properties in tumor targeting, imaging, and therapy, which have attracted increasing attention as a potential complement for, or improved to, classical small molecule antitumor drugs. Photosensitizer have dual functions of imaging and phototherapy, and have been widely used in the construction of small molecule theranostic agents over the last decade. In this review, we summarized representative agents that have been studied in the field of small molecule theranostic agents based on photosensitizer in the last decade, and highlighted their characteristics and application in tumor-targeted monitoring and phototherapy. The challenges and future perspectives of photosensitizers in building small molecule theranostic agents for diagnosis and therapy of tumors were also discussed.

Mitochondria Targeted AIE Probes for Cancer Phototherapy

In recent years, mitochondrion (powerhouse of the cells) gained lots of interest as one of the unorthodox targets for futuristic cancer therapy. As a result, novel small molecules were developed to damage and image mitochondria in cancer models. In this context, aggregation-induced emission probes (AIEgens) received immense attention due to their applications in mitochondria-targeted biosensing, imaging, and biomedical theranostics. On the other hand, phototherapy (photodynamic and photothermal) has emerged as a powerful alternative to manage cancer due to its less invasive nature. However, merging these two areas to engineer mitochondria-targeted phototherapeutic probes for cancer diagnosis and treatment has remained a major challenge. In this mini-review, we will outline the development of novel mitochondria-targeted small molecule AIEgens as imaging agents and photosensitizers for photodynamic therapy along with dual photodymanic-phototheramal therapy and chemo-photodynamic therapy. We will also highlight the current challenges in developing mitochondria-targeted photothermal therapy probes for future biomedical theranostic applications to manage cancer.

Aggregation-induced emission of a bis(imino)acenaphthene zinc complex with tetraphenylethene units

Using bis(imino)acenaphthene (BIAN) zinc(II) and palladium(II) complexes with tetraphenylethene (TPE) units as bulky aryl groups, Zn-2 and Pd-2 have been designed and developed, and their photophysical properties in solution and in the solid state have been investigated. Both in solution and in the solid state Zn-2 and Pd-2 show two photoabsorption bands in the ranges of 300 nm to 350 nm and 450 nm to 600 nm, which are assigned to the π-π* transition originating from both the TPE units and naphthalene units and the intraligand charge transfer (ILCT) between the TPE units and the BIAN unit, respectively. Density functional theory (DFT) calculations demonstrated that for Zn-2 the highest occupied molecular orbitals (HOMO) are localized on the TPE units, while the lowest unoccupied molecular orbitals (LUMO) are localized on the BIAN unit, leading to the appearance of a photoabsorption band on the ILCT. The emission from Zn-2 was quenched in solution, but appeared as phosphorescence at around 600 nm by photoexcitation at the ILCT band in the solid state as well as in the aggregated state, which was formed by the addition of n-hexane as a poor solvent to the dichloromethane (DCM) solution. The aggregate formation of Zn-2 in the DCM/n-hexane (10 wt%/90 wt%) solution was confirmed by the Tyndall scattering and scanning electron microscopy (SEM) measurements, demonstrating the aggregation-induced emission (AIE) characteristics of Zn-2. On the other hand, Pd-2 was non-emissive in the solid state and in the aggregated state as well as in solution. Moreover, the DCM-inclusion complexes of Zn-2 and Pd-2 were obtained and their photophysical properties were investigated. It was found that the photoluminescence quantum yield (Φ_PL-solid) values of Zn-2 and Zn-2-DCM in the solid state are less than 1%. Single-crystal X-ray structural analysis of Zn-2-DCM revealed the absence of intermolecular π-π interactions. Consequently, it was suggested that the low Φ_PL-solid value of Zn-2 is mainly due to the radiationless relaxation of the excitons by dynamic rotation of the phenyl groups of the TPE units, even in the solid state and in the aggregation state.

A novel fluorescent probe with ACQ-AIE conversion by alkyl chain engineering for simultaneous visualization of lipid droplets and lysosomes

The AIE bio-probes have attracted extensive attention because of their good brightness, long-term in situ retention ability, photostability and low cytotoxicity. Recently, the transformation of ACQ to AIE has become very popular, which is very important for the further development of AIE probes. Herein, a series of novel dyes (NR-Lyso-Ⅰ, NR-Lyso-Ⅱ, NR-Lyso-III, NR-Lyso-IV) were designed and synthesized. It was found that alkylation of 4-aminonaphthalimide could achieve the transformation of the dye from ACQ to AIE effect due to the growth of carbon chain. Moreover, the AIE probe NR-Lyso-IV exhibited dual-state emission (DSE) and large Stokes shift (＞100 nm), excellent selectivity, photostability, and low cytotoxicity, which was able to simultaneous visualize the lipid droplets (LDs) and lysosomes of HeLa cells and zebrafish.

"Smart" drug delivery: A window to future of translational medicine

Chemotherapy is the mainstay of cancer treatment today. Chemotherapeutic drugs are non-selective and can harm both cancer and healthy cells, causing a variety of adverse effects such as lack of specificity, cytotoxicity, short half-life, poor solubility, multidrug resistance, and acquiring cancer stem-like characteristics. There is a paradigm shift in drug delivery systems (DDS) with the advent of smarter ways of targeted cancer treatment. Smart Drug Delivery Systems (SDDSs) are stimuli responsive and can be modified in chemical structure in response to light, pH, redox, magnetic fields, and enzyme degradation can be future of translational medicine. Therefore, SDDSs have the potential to be used as a viable cancer treatment alternative to traditional chemotherapy. This review focuses mostly on stimuli responsive drug delivery, inorganic nanocarriers (Carbon nanotubes, gold nanoparticles, Meso-porous silica nanoparticles, quantum dots etc.), organic nanocarriers (Dendrimers, liposomes, micelles), antibody-drug conjugates (ADC) and small molecule drug conjugates (SMDC) based SDDSs for targeted cancer therapy and strategies of targeted drug delivery systems in cancer cells.

Highly Efficient Photodynamic Therapy with Mitochondria-Targeting Aggregation-Induced Emission Photosensitizer for Retinoblastoma

Retinoblastoma (RB) is an aggressive eye cancer in infancy and childhood, lethal by metastasis if left untreated. Currently, the survival rate and the chance of saving vision depend on the severity of the disease. In this work, a highly efficient photodynamic ophthalmic therapy for RB is reported by employing an isoquinolinium-based aggregation-induced-emission (AIE) photosensitizer (PS) TPE-IQ-2O for photodynamic inactivation (PDI). TPE-IQ-2O is an efficient mitochondria-targeting photosensitizer as an efficient guided photodynamic therapy (PDT) agent against cancer cells. Maximizing cancer-selectively damage to tumors with minimized side effects on normal tissue is essential for effective anticancer PDT and provides long-lasting protection against metastasis. In addition, TPE-IQ-2O can effectively reduce the degree of tissue inflammation by inhibiting the expression of related inflammatory factors. TPE-IQ-2O also exhibits excellent biocompatibility with a neglectable hemolysis effect on mouse red blood cells and almost no killing effect on mammalian cells, which enables its potential applications in the treatment of RB.

Visualization of Mitochondria During Embryogenesis in Zebrafish by Aggregation-Induced Emission Molecules

PURPOSE

Aggregation-induced emission (AIE) molecules have been widely utilized for fluorescence imaging in many biomedical applications, benefited from large Stokes shift, high quantum yield, good biocompatibility, and resistance to photobleaching. And visualization of mitochondria is almost investigated in vitro and ex vivo, but in vivo study of mitochondria is more essential for systematic biological research, especially during embryogenesis. Therefore, suitable and time-saving alternatives with simple operation based on AIE molecules are urgently needed compared with traditional transgenic approach.

PROCEDURES

Five tetraphenylethylene isoquinolinium (TPE-IQ)-based molecules with AIE characteristics and their ability of mitochondrial visualization in vitro and in vivo and mitochondrial tracking during embryogenesis on zebrafish model were investigated. The biosafety of these AIE molecules was also evaluated systematically in vitro and in vivo.

RESULTS

All these five AIE molecules could image mitochondria in vitro with good biocompatibility. In them, TPE-IQ1 exhibited excellent imaging quality for in vivo visualization and tracking of mitochondria during the 4-day embryogenesis in zebrafish, in comparison with the conventional transgenic fluorescent protein. Furthermore, TPE-IQ1 could visualize mitochondrial damage induced by chemicals in real time on 24-h post fertilization (hpf) embryos.

CONCLUSIONS

This study indicated TPE-IQ-based AIE molecules had the potential for mitochondrial imaging and tracking during embryogenesis and mitochondrial damage visualization in vivo.

Structure and functions of Aggregation-Induced Emission-Photosensitizers in anticancer and antimicrobial theranostics

Photosensitizers with Aggregation-Induced Emission (AIE) can allow the efficient light-mediated generation of Reactive Oxygen Species (ROS) based on their complex molecular structure, while interacting with living cells. They achieve better tissue targeting and allow penetration of different wavelengths of Ultraviolet-Visible-Infrared irradiation. Not surprisingly, they are useful for fluorescence image-guided Photodynamic Therapy (PDT) against cancers of diverse origin. AIE-photosensitizers can also function as broad spectrum antimicrobials, capable of destroying the outer wall of microbes such as bacteria or fungi without the issues of drug resistance, and can also bind to viruses and deactivate them. Often, they exhibit poor solubility and cellular toxicity, which compromise their theranostic efficacy. This could be circumvented by using suitable nanomaterials for improved biological compatibility and cellular targeting. Such dual-function AIE-photosensitizers nanoparticles show unparalleled precision for image-guided detection of tumors as well as generation of ROS for targeted PDT in living systems, even while using low power visible light. In short, the development of AIE-photosensitizer nanoparticles could be a better solution for light-mediated destruction of unwanted eukaryotic cells and selective elimination of prokaryotic pathogens, although, there is a dearth of pre-clinical and clinical data in the literature.

Upconversion Nanostructures Applied in Theranostic Systems

Upconversion (UC) nanostructures, which can upconvert near-infrared (NIR) light with low energy to visible or UV light with higher energy, are investigated for theranostic applications. The surface of lanthanide (Ln)-doped UC nanostructures can be modified with different functional groups and bioconjugated with biomolecules for therapeutic systems. On the other hand, organic molecular-based UC nanostructures, by using the triplet-triplet annihilation (TTA) UC mechanism, have high UC quantum yields and do not require high excitation power. In this review, the major UC mechanisms in different nanostructures have been introduced, including the Ln-doped UC mechanism and the TTA UC mechanism. The design and fabrication of Ln-doped UC nanostructures and TTA UC-based UC nanostructures for theranostic applications have been reviewed and discussed. In addition, the current progress in the application of UC nanostructures for diagnosis and therapy has been summarized, including tumor-targeted bioimaging and chemotherapy, image-guided diagnosis and phototherapy, NIR-triggered controlled drug releasing and bioimaging. We also provide insight into the development of emerging UC nanostructures in the field of theranostics.

Recent advances in nanotechnology mediated mitochondria-targeted imaging

Mitochondria play a critical role in cell growth and metabolism. And mitochondrial dysfunction is closely related to various diseases, such as cancers, and neurodegenerative and cardiovascular diseases. Therefore, it is of vital importance to monitor mitochondrial dynamics and function. One of the most widely used methods is to use nanotechnology-mediated mitochondria targeting and imaging. It has gained increasing attention in the past few years because of the flexibility, versatility and effectiveness of nanotechnology. In the past few years, researchers have implemented various types of design and construction of the mitochondrial structure dependent nanoprobes following assorted nanotechnology pathways. This review presents an overview on the recent development of mitochondrial structure dependent target imaging probes and classifies it into two main sections: mitochondrial membrane targeting and mitochondrial microenvironment targeting. Also, the significant impact of previous research as well as the application and perspectives will be demonstrated.

A Dual-Labeling Probe for Super-Resolution Imaging to Detect Mitochondrial Reactive Sulfur Species in Live Cells

Background: Mitochondria are the main sites of reactive sulfur species (RSS) production in living cells. RSS in mitochondria play an important role in physiological and pathological processes of life. In this study, a dual-labeling probe that could simultaneously label the mitochondrial membrane and matrix was designed to quantitatively detect RSS of mitochondria in living cells using nano-level super-resolution imaging.

Methods: A fluorescent probe CPE was designed and synthesized. The cytotoxicity of CPE was determined and co-localization of CPE with a commercial mitochondrial probe was analyzed in HeLa cells. Then, the uptake patterns of CPE in HeLa cells at different temperatures and endocytosis levels were investigated. The staining characteristics of CPE under different conditions were imaged and quantitated under structured illumination microscopy.

Results: A fluorescence probe CPE reacting to RSS was developed, which could simultaneously label the mitochondrial membrane with green fluorescence and the mitochondrial matrix with red fluorescence. CPE was able to demonstrate the mitochondrial morphology and detect the changes of RSS in mitochondria. With the increase of mitochondrial RSS concentration, the light of the red matrix will be quenched.

Conclusion: CPE provides a strategy for the design of probes and an attractive tool for accurate examination to changes of mitochondrial morphology and RSS in mitochondria in living cells at the nanoscale.

Supramolecular cuboctahedra with aggregation-induced emission enhancement and external binding ability

Beyond the AIE (aggregation-induced emission) phenomenon in small molecules, supramolecules with AIE properties have evolved in the AIE family and accelerated the growth of supramolecular application diversity. Inspired by its mechanism, particularly the RIV (restriction of intramolecular vibrations) process, a feasible strategy of constructing an AIE-supramolecular cage based on the oxidation of sulfur atoms and coordination of metals is presented. In contrast to previous strategies that used molecular stacking to limit molecular vibrations, we achieved the desired goal using the synergistic effects of coordination-driven self-assembly and oxidation. Upon assembling with zinc ions, S1 was endowed with a distinct AIE property compared with its ligand L1, while S2 exhibited a remarkable fluorescence enhancement compared to L2. Also, the single cage-sized nanowire structure of supramolecules was obtained via directional electrostatic interactions with multiple anions and rigid-shaped cationic cages. Moreover, the adducts of zinc porphyrin and supramolecules were investigated and characterized by 2D DOSY, ESI-MS, TWIM-MS, UV-vis, and fluorescence spectroscopy. The protocol described here enriches the ongoing research on tunable fluorescence materials and paves the way towards constructing stimuli-responsive luminescent supramolecular cages.

Beyond the AIE (aggregation-induced emission) phenomenon in small molecules, supramolecules with AIE properties have evolved in the AIE family and accelerated the growth of supramolecular application diversity.

Synthesis of tetraphenylethene-based D-A conjugated molecules with near-infrared AIE features, and their application in photodynamic therapy

Herein, five aggregation-induced emission (AIE) photosensitizers (PSs) with D-π-A structures are smoothly designed and synthesized through donor and acceptor engineering. The photophysical properties and theoretical calculation results show that the synergistic effect of methoxy substituted tetraphenylethene (MTPE), 3,4-ethylenedioxythiophene can enhance the intramolecular charge transfer effect (ICT), and promote the intersystem crossing (ISC) process of the whole molecule. In these AIE-PSs, the best-performing AIE-PS (MTPE-DT-Py) has bright NIR (740 nm) emission, the highest ¹O₂ generation efficiency (5.9-fold that of Rose Bengal) and efficient mitochondrial targeting ability. Subsequently, PDT anti-cancer and anti-bacterial experiments indicate that MTPE-DT-Py could obviously target mitochondria and kill breast cancer cells (MCF-7), and selectively inactivate S. aureus (G(+)) under white light irradiation. This work mainly proposes a practical design strategy for high effect AIE-PSs and provides more excellent candidates for fluorescence imaging-guided photodynamic therapy.

The fast-growing field of photo-driven theranostics based on aggregation-induced emission

Photo-driven theranostics, also known as phototheranostics, relying on the diverse excited-state energy conversions of theranostic agents upon photoexcitation represents a significant branch of theranostics, which ingeniously integrate diagnostic imaging and therapeutic interventions into a single formulation. The combined merits of photoexcitation and theranostics endow photo-driven theranostics with numerous superior features. The applications of aggregation-induced emission luminogens (AIEgens), a particular category of fluorophores, in the field of photo-driven theranostics have been intensively studied by virtue of their versatile advantageous merits of favorable biocompatibility, tuneable photophysical properties, unique aggregation-enhanced theranostic (AET) features, ideal AET-favored on-site activation ability and ready construction of one-for-all multimodal theranostics. This review summarised the significant achievements of photo-driven theranostics based on AIEgens, which were detailedly elaborated and classified by their diverse theranostic modalities into three groups: fluorescence imaging-guided photodynamic therapy, photoacoustic imaging-guided photothermal therapy, and multi-modality theranostics. Particularly, the tremendous advantages and individual design strategies of AIEgens in pursuit of high-performance photosensitizing output, high photothermal conversion and multimodal function capability by adjusting the excited-state energy dissipation pathways are emphasized in each section. In addition to highlighting AIEgens as promising templates for modulating energy dissipation in the application of photo-driven theranostics, current challenges and opportunities in this field are also discussed.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

Tetraphenylethene–anthracene-based fluorescence emission sensor for detection of water with photo-induced electron transfer and aggregation-induced emission characteristics

As a fluorescent sensor for water over a wide range from low to high water content regions in organic solvents, we have designed and developed a PET (photo-induced electron transfer)/AIE...

A novel AIEgen photosensitizer with an elevated intersystem crossing rate for tumor precise imaging and therapy

An ultraefficient AIEgen photosensitizer (TPE-4QL+) was synthesized based on an alternative elevated intersystem crossing rate for the precise imaging and therapy of tumors.

Practicable Applications of Aggregation-Induced Emission with Biomedical Perspective

Considerable efforts have been made into developing aggregation-induced emission fluorogens (AIEgens)-containing nano-therapeutic systems due to the excellent properties of AIEgens. Compared to other fluorescent molecules, AIEgens have advantages including low background, high signal-to-noise ratio, good sensitivity, and resistance to photobleaching, in addition to being exempt from concentration quenching or aggregation-caused quenching effects. The present review outlines the major developments in the biomedical applications of AIEgens-containing systems. From a literature survey, the recent AIE works are reviewed and the reasons why AIEgens are chosen in various biomedical applications are highlighted. The research activities on AIEgens-containing systems are increasing rapidly, therefore, the present review is timely.

Aggregation-induced emission luminogens for image-guided surgery in non-human primates

During the past two decades, aggregation-induced emission luminogens (AIEgens) have been intensively exploited for biological and biomedical applications. Although a series of investigations have been performed in non-primate animal models, there is few pilot studies in non-human primate animal models, strongly hindering the clinical translation of AIE luminogens (AIEgens). Herein, we present a systemic and multifaceted demonstration of an optical imaging-guided surgical operation via AIEgens from small animals (e.g., mice and rabbits) to rhesus macaque, the typical non-human primate animal model. Specifically, the folic conjugated-AIE luminogen (folic-AIEgen) generates strong and stable fluorescence for the detection and surgical excision of sentinel lymph nodes (SLNs). Moreover, with the superior tumor/normal tissue ratio and rapid tumor accumulation, folic-AIEgen successfully images and guides the precise resection of invisible cancerous metastases. Taken together, the presented strategies of folic-AIEgen based fluorescence intraoperative imaging and visualization-guided surgery show potential for clinical applications.

Most applications of aggregation-induced emission luminogens (AIEgens) have been limited in small animal models. Here, the authors show the versatility of AIEgens-based imaging-guided surgical operation from small animals to rhesus macaque, in support of the clinical translation of AIEgens.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Vision redemption: Self-reporting AIEgens for combined treatment of bacterial keratitis

Bacterial keratitis (BK) is one of the most commonly leading causes of visual impairment and blindness worldwide, and suffers the risk of drug-resistant infections due to the abuse of antibiotics. Herein, we report a cationic diphenyl luminogen with aggregation-induced emission called IQ-Cm containing isoquinolinium and coumarin units for theranostic study of BK. IQ-Cm has no obvious cytotoxicity to mammalian cells below a certain concentration, and could preferentially bind to bacteria over mammalian cells. IQ-Cm can be used as a sensitive self-reporting probe to rapidly discriminate live and dead bacteria by the visual emission colors. The intrinsic dark toxicity to bacteria and generation of reactive oxygen species under light irradiation endow IQ-Cm with excellent antibacterial activity in vitro and in BK rabbit models infected with S. aureus. The present study provides a sensitive and efficient theranostic strategy for rapid discrimination of various bacterial states and the combined treatment of BK based on the intrinsic dark antibacterial activity and photodynamic therapy effect.

Real-time imaging mitochondrial viscosity dynamic during mitophagy mediated by photodynamic therapy

Photodynamic therapy has been generally developed and approved as a promising theranostic technique in recent years, which requires photosensitizers to bear high efficiency of reactive oxygen species production, precisely targeting ability and excellent biocompatibility. The real-time monitoring the microenvironments such as viscosity dynamic involved in mitophagy mediated by photodynamic therapy is significantly important to understand therapeutic process but barely reported. In this work, a pyridinium-functionalized triphenylamine derivative, (E)-4-(2-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)vinyl)-1-methylpyridin-1-ium iodide (Mito-I), was exploited as photosensitizer for mitochondria-targeted photodynamic therapy and as fluorescent probe for imaging the mitochondrial viscosity dynamic during mitophagy simultaneously. The results indicated that the additional phenyl ring in Mito-I was beneficial to promote its efficiency of singlet oxygen production. The excellent capability of targeting mitochondria and singlet oxygen generation allowed Mito-I for the specifically mitochondria-targeted photodynamic therapy. Moreover, Mito-I displayed off-on fluorescence response to viscosity with high selectivity and sensitivity. The observed enhancement in fluorescence intensity of Mito-I revealed the increasingly mitochondrial viscosity during mitophagy mediated by the photodynamic therapy of Mito-I. As a result, this work presents a rare example to realize the mitochondria-targeting photodynamic therapy as well as the real-time monitoring viscosity dynamic during mitophagy, which is of great importance for the basic medical research involved in photodynamic therapy.

Low Polarity-Triggered Basic Hydrolysis of Coumarin as an AND Logic Gate for Broad-Spectrum Cancer Diagnosis

The ability to accurately diagnose cancer is the cornerstone of early cancer treatment. The mitochondria in cancer cells maintain a higher pH and lower polarity relative to that in normal cells. A probe that reports signals only when both conditions are met may provide a reliable method for cancer detection with reduced false positives. Here, we construct an AND logic gate fluorescent probe using mitochondrial microenvironments as inputs. Utilizing the hydrolysis of a coumarin scaffold, the probe generates fluorescence signals ("ON") only when high pH (>7.0) and low polarity conditions exist simultaneously. Additionally, the higher mitochondrial membrane potential in cancer cells provides an additional level of selectivity because probe has increased affinity for cancer cell mitochondria. These capabilities endow the probe with a high contrast fluorescence diagnosis ability of cancer at cellular and tissue levels (as high as 51.9 fold), which is far exceeding the clinic threshold of 2.0 fold.

Activation of apoptosis by rationally constructing NIR amphiphilic AIEgens: surmounting the shackle of mitochondrial membrane potential for amplified tumor ablation

In recent years, the use of aggregation-induced emission luminogens (AIEgens) for biological imaging and phototherapy has become an area of intense research. However, most traditional AIEgens suffer from undesired aggregation in aqueous media with "always on" fluorescence, or their targeting effects cannot be maintained accurately in live cells with the microenvironment changes. These drawbacks seriously impede their application in the fields of bio-imaging and antitumor therapy, which require a high signal-to-noise ratio. Herein, we propose a molecular design strategy to tune the dispersity of AIEgens in both lipophilic and hydrophilic systems to obtain the novel near-infrared (NIR, ∼737 nm) amphiphilic AIE photosensitizer (named TPA-S-TPP) with two positive charges as well as a triplet lifetime of 11.43 μs. The synergistic effects of lipophilicity, electrostatic interaction, and structure-anchoring enable the wider dynamic range of AIEgen TPA-S-TPP for mitochondrial targeting with tolerance to the changes of mitochondrial membrane potential (ΔΨ m). Intriguingly, TPA-S-TPP was difficult for normal cells to be taken up, indicative of low inherent toxicity for normal cells and tissues. Deeper insight into the changes of mitochondrial membrane potential and cleaved caspase 3 levels further revealed the mechanism of tumor cell apoptosis activated by AIEgen TPA-S-TPP under light irradiation. With its advantages of low dark toxicity and good biocompatibility, acting as an efficient theranostic agent, TPA-S-TPP was successfully applied to kill cancer cells and to efficiently inhibit tumor growth in mice. This study will provide a new avenue for researchers to design more ideal amphiphilic AIE photosensitizers with NIR fluorescence.

PEGylated AIEgen molecular probe for hypoxia-mediated tumor imaging and photodynamic therapy

We report a novel PEGylated aggregation-induced emission luminogen (AIEgen) molecular probe for hypoxia-mediated tumor imaging and photodynamic therapy by linking a PEG chain to the AIE-active photosensitizer via a hypoxia-sensitive azo group.

Mitochondria-Specific Aggregation-Induced Emission Luminogens for Selective Photodynamic Killing of Fungi and Efficacious Treatment of Keratitis

The development of effective antifungal agents remains a big challenge in view of the close evolutionary relationship between mammalian cells and fungi. Moreover, rapid mutations of fungal receptors at the molecular level result in the emergence of drug resistance. Here, with low tendency to develop drug-resistance, the subcellular organelle mitochondrion is exploited as an alternative target for efficient fungal killing by photodynamic therapy (PDT) of mitochondrial-targeting luminogens with aggregation-induced emission characteristics (AIEgens). With cationic isoquinolinium (IQ) moiety and proper hydrophobicity, three AIEgens, namely, IQ-TPE-2O, IQ-Cm, and IQ-TPA, can preferentially accumulate at the mitochondria of fungi over the mammalian cells. Upon white light irradiation, these AIEgens efficiently generate reactive ¹O₂, which causes irreversible damage to fungal mitochondria and further triggers the fungal death. Among them, IQ-TPA shows the highest PDT efficiency against fungi and negligible toxicity to mammalian cells, achieving the selective and highly efficient killing of fungi. Furthermore, we tested the clinical utility of this PDT strategy by treating fungal keratitis on a fungus-infected rabbit model. It was demonstrated that IQ-TPA presents obviously better therapeutic effects as compared with the clinically used rose bengal, suggesting the success of this PDT strategy and its great potential for clinical treatment of fungal infections.

Nanobody modified high-performance AIE photosensitizer nanoparticles for precise photodynamic oral cancer therapy of patient-derived tumor xenograft

Photodynamic therapy (PDT) is a promising noninvasive treatment option for patients suffering from superficial tumors, such as oral cancer. However, for photosensitizers (PSs), it remains a grand challenge to simultaneously excel in all the key performance indicators including effective singlet oxygen (¹O₂) generation under clinical laser, specific targeting function and stable far-red (FR)/near-infrared (NIR) emission with low dark toxicity. In addition, traditional PS nanoparticles (NPs) for clinical use suffer from quenched fluorescence and reduced ¹O₂ production caused by molecular aggregation. To address these issues, AIEPS5 with aggregation-induced FR/NIR emission and effective ¹O₂ generation under 532 nm laser irradiation is designed by precise optimization of the chemical structure. By attaching a polyethylene glycol (PEG) chain onto AIEPS5, the yielded amphiphilic AIEPS5-PEG2000 can spontaneously self-assemble into water dispersible NPs, which are further endowed with targeted delivery function via the decoration of anti-Her-2 nanobody (NB). The bespoke AIEPS5-NPs-NB exhibit effective ¹O₂ generation capability, bright FR/NIR emission centered at 680 nm, and negligible dark toxicity, which outperform Heimbofen, a clinically approved PS in PDT using a patient-derived tumor xenograft model.

Organelle-Targeted Photosensitizers for Precision Photodynamic Therapy

Subcellular organelles are the cornerstones of cells, and destroying them will cause cell dysfunction and even death. Therefore, realizing precise organelle targeting of photosensitizers (PSs) can help reduce PS dosage, minimize side effects, avoid drug resistance, and enhance therapeutic efficacy in photodynamic therapy (PDT). Organelle-targeted PSs provide a new paradigm for the construction of the next generation of PSs and may provide implementable strategies for future precision medicine. In this Review, the recent targeting strategies of different organelles and the corresponding design principles of molecular and nanostructured PSs are summarized and discussed. The current challenges and opportunities in organelle-targeted PDT are also presented.

Immunostimulatory AIE Dots for Live-Cell Imaging and Drug Delivery

The mechanical properties of nanoscale drug carriers play critical roles in regulating nano-bio interactions. For example, the superior deformability of the softer nanoparticles enables them to pass through the biofilters efficiently, facilitating their long blood circulation and better tumor penetration. However, as a novel nanocarrier system, the elimination efficiency of soft nanoparticles from cells is poorly investigated. Here, we report a facile strategy to prepare soft luminescent nanoparticles through self-assembly of amphiphilic aggregation-induced emission (AIE) fluorophores. The prepared soft AIE dots exhibit strong light emission (quantum yield, ∼27.1%) and can reveal the encapsulation and excretion process of NPs in real time. The cell results showed that soft NPs can greatly increase the transfer speed of nanomaterials into cells and accelerate their elimination from cells through the sacrifice of soft AIE dots. We also show that soft AIE dots loaded with cytosine-phosphate-guanine (CpG) oligodeoxynucleotides can induce strong immunostimulatory effects, producing a high level of various proinflammatory cytokines including tumor necrosis factor (TNF)-R, interleukin (IL)-6, and IL-12. This work demonstrates a new design strategy for synthesizing a soft nanocarrier system that can deliver drugs into cells efficiently and then be eliminated from cells quickly.

Recent advances of AIE light-up probes for photodynamic therapy

As a new non-invasive treatment method, photodynamic therapy (PDT) has attracted great attention in biomedical applications. The advantages of possessing fluorescence for photosensitizers have made it possible to combine imaging and diagnosis together with PDT. The unique features of aggregation-induced emission (AIE) fluorogens provide new opportunities for facile design of light-up probes with high signal-to-noise ratios and improved theranostic accuracy and efficacy for image-guided PDT. In this review, we summarize the recent advances of AIE light-up probes for PDT. The strategies and principles to design AIE photosensitizers and light-up probes are firstly introduced. The application of AIE light-up probes in photodynamic antitumor and antibacterial applications is further elaborated in detail, from binding/targeting-mediated, reaction-mediated, and external stimuli-mediated light-up aspects. The challenges and future perspectives of AIE light-up probes in the PDT field are also presented with the hope to encourage more promising developments of AIE materials for phototheranostic applications and translational research.

Detection and monitoring of the neuroprotective behavior of curcumin micelles based on an AIEgen probe

In recent years, the role of mitochondrial injury in the pathogenesis of Alzheimer's disease (AD) has attracted extensive attention. Studies have shown that curcumin (Cur) can protect nerve cells from beta-amyloid (Aβ)-induced mitochondrial damage. However, natural Cur encounters limited application due to its poor biocompatibility and bioavailability. To improve the solubility and biocompatibility of natural Cur, we prepared water-soluble curcumin micelles (CurM). Furthermore, the mitochondria-specific aggregation-induced emission (AIE) probe (TPE-Ph-In) was employed to observe the protective effect of CurM on the damage of mitochondrial morphology, distribution, and membrane potential caused by Aβ. Results showed that CurM had higher solubility, stronger stability and retention effect, and better cellular uptake than that of natural Cur. Furthermore, the inhibitory effects of CurM on mitochondrial morphology, distribution, and membrane potential damage induced by Aβ25-35 were observed utilizing TPE-Ph-In as an indicator of mitochondrial morphology and membrane potential. Thus, this method provides a useful strategy for experimental research and clinical treatment of AD with mitochondrial damage as the pathogenic mechanism.

Emerging trends in aggregation induced emissive luminogens as bacterial theranostics

The emergence and spread of pathogenic bacteria, particularly antibiotic-resistant strains pose grave global concerns worldwide, which demand for the rapid development of highly selective and sensitive strategies for specific bacterial detection, identification, imaging and therapy. The fascinating feature of aggregation-induced emissive molecules (AIEgens) to display fluorescence in aggregate form can be suitably coupled with nanotechnology for developing theranostic AIE dots that can offer convenient and customised functions such as sensing, imaging, detection, discrimination and cell kill of different bacterial types. The initial section of the article reveals the necessity for incorporating diagnostic imaging with antibacterial therapy, while the latter part delivers mechanistic insights on the benefits of AIE fluorophores in theranostic applications. Further, the review illustrates the recent advancements of AIEgens as theranostic nanolights in bacterial detection, identification and eradication. The review is organised according to the different classes of AIE-active bacterial theranostics such as carrier-free nanoprodrugs, nanomachines for synergistic imaging-guided cancer treatment and bacterial kill, AIE polymers, bioconjugates and nanoparticle carriers. By elucidating their design principles and applications, as well as highlighting the recent trends and perspectives that can be further explored, we hope to instill more research interest in AIE bacterial theranostics for future translational research.HighlightsCombination of aggregation induced emissive fluorophores and nanotechnology for developing bacterial theranostics.AIE theranostics with customised functions for bacterial imaging, detection, discrimination and cell kill.

Innovative Synthetic Procedures for Luminogens Showing Aggregation-Induced Emission

As a consequence of their intrinsic advantageous properties, luminogens that show aggregation-induced emission (AIEgens) have received increasing global interest for a wide range of applications. Whereas general synthetic methods towards AIEgens largely rely on tedious procedures and limited reaction types, various innovative synthetic methods have now emerged as complementary, and even alternative, strategies. In this Review, we systematically highlight advancements made in metal-catalyzed functionalization and metal-free-promoted pathways for the construction of AIEgens over the past five years, and briefly illustrate new perspectives in this area. The development of innovative synthetic procedures will enable the facile synthesis of AIEgens with great structural diversity for multifunctional applications.

Mitochondria-Specific Agents for Photodynamic Cancer Therapy: A Key Determinant to Boost the Efficacy

Mitochondria-targeted photodynamic therapy (Mt-PDT), which enables the photogenerated cytotoxic oxygen species with fatal oxidative damage to block mitochondrial functions, has been considered as a promising method to enhance the anticancer effectiveness. Aiming at the challenges of PDT, in the past few decades, numerous mitochondria-targeting molecular agents have been developed to boost the PDT efficacy via directly destroying the mitochondria or activating mitochondria-mediated cell death pathways. Herein, a review for recent advances of Mt-PDT is highlighted including: mitochondrial targeting design principles and strategies, therapeutic performance of mitochondria-targeted agents-mediated PDT as well as the agent-free Mt-PDT. In addition, it puts together the achievements of the combinatory mitochondria-anchoring PDT and other anticancer strategies, demonstrating the advantages provided by Mt-PDT. The existing challenges are discussed and future settlements for the development of mitochondria-specific agents are also forecasted.

Transporting mitochondrion-targeting photosensitizers into cancer cells by low-density lipoproteins for fluorescence-feedback photodynamic therapy

Low-density lipoproteins (LDLs) are an endogenous nanocarrier to transport lipids in vivo. Owing to their biocompatibility and biodegradability, reduced immunogenicity, and natural tumor-targeting capability, we, for the first time, report the reconstitution of native LDL particles with saturated fatty acids and a mitochondrion-targeting aggregation-induced emission (AIE) photosensitizer for fluorescence-feedback photodynamic therapy (PDT). In particular, a novel AIE photosensitizer (TPA-DPPy) with a donor-acceptor (D-A) structure and a pyridinium salt is designed and synthesized, which possesses typical AIE and twisted intramolecular charge transfer (TICT) characteristics as well as reactive oxygen species (ROS)-sensitizing capability. In view of its prominent photophysical and photochemical properties, TPA-DPPy is encapsulated into LDL particles for photodynamic killing of cancer cells that overexpress LDL receptors (LDLRs). The resultant LDL (rLDL) particles maintain a similar morphology and size distribution to native LDL particles, and are efficiently ingested by cancer cells via LDLR-mediated endocytosis, followed by the release of TPA-DPPy for mitochondrion-targeting. Upon light irradiation, the produced ROS surrounding mitochondria lead to efficient and irreversible cell apoptosis. Interestingly, this process can be fluorescently monitored in a real-time fashion, as reflected by the remarkably enhanced luminescence and blue-shifted emission, indicating the increased mechanical stress during apoptosis. Quantitative cell viability analysis suggests that TPA-DPPy exhibits an outstanding phototoxicity toward LDLR-overexpressing A549 cancer cells, with a killing efficiency of ca. 88%. The rLDL particles are a class of safe and multifunctional nanophototheranostic agents, holding great promise in high-quality PDT by providing real-time fluorescence feedback on the therapeutic outcome.