Highly efficient singlet oxygen generation, two-photon photodynamic therapy and melanoma ablation by rationally designed mitochondria-specific near-infrared AIEgens

In situ forming AIEgen-alginate hydrogel for remodeling tumor microenvironment to boost FLASH immunoradiotherapy

FLASH radiotherapy, which involves the delivery of an ultra-high radiation dose rate exceeding 40 Gy/s, has emerged as a promising tumor ablation strategy. While this approach generally spares normal tissues, the incomplete killing of tumors may sometimes lead to recurrence due to the immunosuppressive tumor microenvironment (TME). Herein, an aggregation-induced-emission luminogen (AIEgen)-alginate hydrogel was used to sensitize colon cancer via photodynamic therapy (PDT). Flower-like calcium carbonate nanoparticles, doped with an AIEgen termed CQu, were designed and applied as a cocktail with sodium alginate. When exposed to the acidic TME, Ca2+ is released from this structure, resulting in sodium alginate termed FA forming a hydrogel in situ within the TME. This hydrogel also captures high concentrations of CQu in the local TME. Under laser irradiation, the CQu can generate sustained reactive oxygen species (ROS) production, thereby facilitating Ca2+ influx and causing mitochondrial damage. Through a single injection of established FA hydrogel, followed by PDT and FLASH radiotherapy, immunogenic tumor cell death was induced which promoted antitumor immunity, thereby protecting against tumor recurrence while realizing abscopal effect. The results highlight the potential to improve the sensitivity of tumor cells to FLASH radiotherapy through sustained ROS production and Ca2+ overload, thereby yielding optimal immunotherapy outcomes.

Cationic AIEgens with large rigid π-planes: Specific bacterial imaging and treatment of drug-resistant bacterial infections

In this study, four D-π-A type cationic photosensitisers with aggregation-induced emission (AIE) properties were developed based on the electron-donating group triphenylamine and pyrene molecules acting as auxiliary electron donors and main π-bridges, as well as pyridinium salts of different charge numbers acting as electron acceptors: TPP1, MeOTPP1, TPP2 and MeOTPP2. The introduction of pyrene endowed the AIE photosensitizers with a high solid fluorescence quantum yield and long fluorescence lifetime. All four photosensitizer molecules were able to efficiently generate type I (·OH) and type II (1O2) under white light irradiation, achieving efficient inactivation of methicillin-resistant Staphylococcus aureus (MRSA) at low concentrations, and TPP1 and TPP2 successfully promoted wound healing in MRSA-infected mice. The introduction of a methoxy group effectively enhanced the intramolecular charge transfer effect, achieved longer wavelength absorption and fluorescence emission redshift, and effectively reduced ΔEst thereby promoting ROS (Reactive Oxygen Species) generation. However, after the introduction of the methoxy group, the CAC (Critical Aggregate Concentration) of MeOTPP1 and MeOTPP2 became smaller and the hydrophobicity was enhanced, which affected the interaction with bacteria. In fact, the photodynamic antimicrobial activity and imaging ability against bacteria were reduced. TPP2 achieves efficient killing of MRSA and MDR E.coli (Multidrug-resistant Escherichia coli) by disrupting the bacterial cell membrane due to its high photosensitization efficiency, two positive charges and very high CAC value. Under light (40 mW·cm-2), only 1 μM of TPP2 inactivated 87 % of MRSA, followed by TPP1, which inactivated 59 %, while MeOTPP1 and MeOTPP2 showed no significant antibacterial activity at this concentration. At a concentration of 10 μM, TPP2 deactivated more than 95 % of MDR E.coli, TPP1 deactivated about 41 %, and MeOTPP1 and MeOTPP2 had no antimicrobial activity against MDR E.coli at this concentration. In addition, TPP1, MeOTPP1 and TPP2 were able to rapidly identify MRSA and MDR E.coli under the irradiation of 365 nm UV light, which provides a visual method for the rapid identification of MRSA and MDR E.coli.

Review of Non-Invasive Imaging Technologies for Cutaneous Melanoma

Imaging technologies are constantly being developed to improve not only melanoma diagnosis, but also staging, treatment planning, and disease progression. We start with a description of how melanoma is characterized using histology, and then continue by discussing nearly two dozen different technologies, including systems currently used in medical practice and those in development. For each technology, we describe its method of operation, how it is or would be projected to be most commonly used in diagnosing and managing melanoma, and for systems in current use, we identify at least one current manufacturer. We also provide a table including the biomarkers identified by and main limitations associated with each technology and conclude by offering suggestions on specific characteristics that might best enhance a technology's potential for widespread clinical adoption.

NIR-II imaging guided on-site size variable clustered nanosystem to potentiate sonodynamic therapy in deep-seated tumors

The insufficient enrichment and penetration of sonosensitizers in the tumor site hamper the antitumor efficiency of sonodynamic therapy (SDT). Herein, tumor-acidity and photothermal controlled nanosystems (NTTD), which coloaded a new type of sonosensitizers, Na3TiF6 NPs and second near-infrared (NIR-II) emissive AIEgen (T1), have been developed to achieve highly efficient SDT/photothermal therapy (PTT) in deep-seated tumors. On one hand, NTTD includes ultrasmall Na3TiF6 NPs with increased oxygen vacancies, narrow bandgap (2.82 eV) and preferrable absorption capability of H2O and O2 molecules, guaranteeing powerful generation of reactive oxygen species (ROS) under US stimulation. On the other hand, with the assistance of the acidic/photothermal responses and deep penetrated NIR-II fluorescence imaging (up to 7 mm), NTTD undergo in situ "two-step" size transformation to achieve enhanced retention and penetration of sonosensitizers in tumor area with high spatiotemporal controllability. In 4T1 tumor model, compared to passive targeting participated NTT group, NTTD elongated the tumor retention time to 60 h and revealed enhanced imaging signal (∼2.4 fold). Further photoirradiation of NTTD assisted ∼4.5-fold enhancement of penetration ability. SDT/PTT synergies have evoked significant ROS generation and tumor inhibition rate of 75.2 % in vivo. This study presents an innovative strategy to exploit novel nano-sonosensitizers with precisely improved tumor accumulation and penetration.

Regio-isomerization Optimization Strategy for Photosensitizers: Achieving Ultrahigh Type I Reactive Oxygen Species Generation to Enhance Cancer Photoimmunotherapy

Phototherapy, renowned for its noninvasiveness, is widely employed in tumor treatment. However, the tumor microenvironment is usually hypoxic, with insufficient reactive oxygen species (ROS) production, severely limiting its application. Herein, we introduce a regio-isomerization optimization strategy and have synthesized four regio-isomeric photosensitizers featuring a donor-acceptor (D-A) configuration by tactically varying the linkage sites between D and A. Among them, TAF-3 with excellent photostability has an ultrahigh type I ROS production efficiency (4.79 times that of methylene blue) and a photothermal conversion efficiency of 41.7%. TAF-3 improves the conjugation degree; produces an appropriate intramolecular charge transfer effect, which enhances its optical properties and phototherapeutic efficiency; and promotes a stronger immune cell death effect, reducing postoperative melanoma recurrence by 60%. Overall, the optical attributes of D-A type photosensitizers can be tailored through the precision modulation of regio-isomerization, offering a promising avenue for the advancement of clinical photosensitizers suitable for phototherapy.

Mechanistic study of tumor fluorescence response signals based on a near-infrared viscosity-sensitive probe

Viscosity is an important physiological parameter closely associated with various cellular processes and diseases. Several fluorescence probes responsive to viscosity have been developed, demonstrating high sensitivity specifically towards tumor tissues. However, the underlying core mechanism of this highly potential responsive signal has been a subject of debate, as highly sensitive probes encounter excessive environmental interferences in complex tumor tissues. Therefore, we have developed a viscosity-responsive fluorescence probe based on the classical TICT mechanism (twisted intramolecular charge transfer) as a research tool. This probe features an ultra-wide emission range of 700-1200 nm in the near-infrared spectrum, strong photostability, and simultaneous targeting of mitochondria and lysosomes. Through in-depth analysis, we have revealed the intrinsic mechanisms underlying its functionality, demonstrating that the major contributor to the fluorescence change of responsive probes during imaging is the inherent state of cells rather than the tumor microenvironment or the cell type. Our findings provide a theoretical foundation for the continued exploration and application of viscosity-responsive probes.

Roadmap for Designing Donor-π-Acceptor Fluorophores in UV-Vis and NIR Regions: Synthesis, Optical Properties and Applications

Donor acceptor (D-π-A) fluorophores containing a donor unit and an acceptor moiety at each end connected by a conjugated linker gained attention in the last decade due to their conjugated system and ease of tunability. These features make them good candidates for various applications such as bioimaging, photovoltaic devices and nonlinear optical materials. Upon excitation of the D-π-A fluorophore, intramolecular charge transfer (ICT) occurs, and it polarizes the molecule resulting in the 'push-pull' system. The emission wavelengths of fluorophores can be altered from UV-vis to NIR region by modifying the donor unit, acceptor moiety and the π linker between them. The NIR emitting fluorophores with restricted molecular rotations are used in aggregation-induced emission (AIE). D-π-A fluorophores with carboxylic acid and cyano groups are preferred in photovoltaic applications, and fluorophores with large surface area are used for two photon absorbing applications. Herein, we report the synthesis, optical properties, and applications of various D-π-A fluorophores in UV-vis and NIR region.

Targeting tumor microenvironment with photodynamic nanomedicine

Photodynamic therapy (PDT) is approved for the treatment of certain cancers and precancer lesions. While early Photosensitizers (PS) have found their way to the clinic, research in the last two decades has led to the development of third-generation PS, including photodynamic nanomedicine for improved tumor delivery and minimal systemic or phototoxicity. In terms of nanoparticle design for PDT, we are witnessing a shift from passive to active delivery for improved outcomes with reduced PS dosage. Tumor microenvironment (TME) comprises of a complex and dynamic landscape with myriad potential targets for photodynamic nanocarriers that are surface-modified with ligands. Herein, we review ways to improvise PDT by actively targeting nanoparticles (NPs) to intracellular organelles such as mitochondria or lysosomes and so forth, overcoming the limitations caused by PDT-induced hypoxia, disrupting the blood vascular networks in tumor tissues-vascular targeted PDT (VTP) and targeting immune cells for photoimmunotherapy. We propose that a synergistic outlook will help to address challenges such as deep-seated tumors, metastasis, or relapse and would lead to robust PDT response in patients.

Antitumor Cream: Transdermal Hydrogel Containing Liposome-Encapsulated Ruthenium Complex for Infrared-Controlled Multimodal Synergistic Therapy

A transdermal drug delivery cream, which is non-invasive and painless, containing a liposome-encapsulated Ru(II) complex (LipoRu) is created for the treatment of skin cancer. This formulation capitalizes on the synergistic antitumor effects of two-photon excited photodynamic therapy (PDT), photothermal therapy (PTT), and chemotherapy. LipoRu exhibits effective tumor accumulation, efficient cellular uptake, pH-sensitive and infrared-accelerated release, and dual localization to the nucleus and mitochondria. The released Ru(II) complexes within cells exert multiple antitumor mechanisms, such as DNA topoisomerase and RNA polymerase inhibition, Type I and II PDT, PTT, DNA photodamage, and apoptosis and ferroptosis induction. The biodistribution and therapeutic efficacy of LipoRu in vivo are systematically compared via three distinct administration routes: intratumoral injection, intravenous injection, and transdermal delivery through topical cream application. The positive therapeutic effects of the LipoRu cream fabricated here in subcutaneous tumor-bearing mice offer optimistic potential for the painless and non-invasive treatment of both early-stage and advanced skin cancers, as well as superficially located solid tumors.

Energy-storing DNA-based hydrogel remodels tumor microenvironments for laser-free photodynamic immunotherapy

Photodynamic therapy (PDT) is a promising modality for cancer treatment. However, limited tissue penetration of external radiation and complicated tumor microenvironments (TMEs) restrict the antitumor efficiency of PDT. Herein, we report an energy-storing DNA-based hydrogel, which enables tumor-selective PDT without external radiation and regulates TMEs to achieve boosted PDT-mediated tumor immunotherapy. The system is constructed with two ultralong single-stranded DNA chains, which programmed partial complementary sequences and repeated G-quadruplex forming AS1411 aptamer for photosensitizer loading via hydrophobic interactions and π-π stacking. Then, energy-storing persistent luminescent nanoparticles are incorporated to sensitize PDT selectively at tumor site without external irradiation, generating tumor antigen to agitate antitumor immune response. The system catalytically generates O2 to alleviate hypoxia and releases inhibitors to reverse the IDO-related immunosuppression, synergistically remodeling the TMEs. In the mouse model of breast cancer, this hydrogel shows a remarkable tumor suppression rate of 78.3 %. Our study represents a new paradigm of photodynamic immunotherapy against cancer by combining laser-free fashion and TMEs remodeling.

Donor-Acceptor Modulating of Ionic AIE Photosensitizers for Enhanced ROS Generation and NIR-II Emission

Photosensitizers (PSs) with aggregation-induced emission (AIE) characteristics are competitive candidates for bioimaging and therapeutic applications. However, their short emission wavelength and nonspecific organelle targeting hinder their therapeutic effectiveness. Herein, a donor-acceptor modulation approach is reported to construct a series of ionic AIE photosensitizers with enhanced photodynamic therapy (PDT) outcomes and fluorescent emission in the second near-infrared (NIR-II) window. By employing dithieno[3,2-b:2',3'-d]pyrrole (DTP) and indolium (In) as the strong donor and acceptor, respectively, the compound DTP-In exhibits a substantial redshift in absorption and fluorescent emission reach to NIR-II region. The reduced energy gap between singlet and triplet states in DTP-In also increases the reactive oxygen species (ROS) generation rate. Further, DTP-In can self-assemble in aqueous solutions, forming positively charged nanoaggregates, which are superior to conventional encapsulated nanoparticles in cellular uptake and mitochondrial targeting. Consequently, DTP-In aggregates show efficient photodynamic ablation of 4T1 cancer cells and outstanding tumor theranostic in vivo under 660 nm laser irradiation. This work highlights the potential of molecular engineering of donor-acceptor AIE PSs with multiple functionalities, thereby facilitating the development of more effective strategies for cancer therapy.

A Membrane-Targeting Aggregation-Induced Emission Probe for Monitoring Lipid Droplet Dynamics in Ischemia/Reperfusion-Induced Cardiomyocyte Ferroptosis

Myocardial ischemia/reperfusion injury (MIRI) is the leading cause of irreversible myocardial damage. A pivotal pathogenic factor is ischemia/reperfusion (I/R)-induced cardiomyocyte ferroptosis, marked by iron overload and lipid peroxidation. However, the impact of lipid droplet (LD) changes on I/R-induced cardiomyocyte ferroptosis is unclear. In this study, an aggregation-induced emission probe, TPABTBP is developed that is used for imaging dynamic changes in LD during myocardial I/R-induced ferroptosis. TPABTBP exhibits excellent LD-specificity, superior capability for monitoring lipophagy, and remarkable photostability. Molecular dynamics (MD) simulation and super-resolution fluorescence imaging demonstrate that the TPABTBP is specifically localized to the phospholipid monolayer membrane of LDs. Imaging LDs in cardiomyocytes and myocardial tissue in model mice with MIRI reveals that the LD accumulation level increase in the early reperfusion stage (0-9 h) but decrease in the late reperfusion stage (>24 h) via lipophagy. The inhibition of LD breakdown significantly reduces the lipid peroxidation level in cardiomyocytes. Furthermore, it is demonstrated that chloroquine (CQ), an FDA-approved autophagy modulator, can inhibit ferroptosis, thereby attenuating MIRI in mice. This study describes the dynamic changes in LD during myocardial ischemia injury and suggests a potential therapeutic target for early MIRI intervention.

Multimodal phototherapy agents target lipid droplets for near-infrared imaging-guided type I photodynamic/photothermal therapy

The construction and optimization of a single phototherapeutic agent with photoluminescence, type I photodynamic therapy (PDT), and photothermal therapy (PTT) functions remain challenging. In this study, we aimed to design and synthesize four donor-acceptor (D-A) type aggregation-induced emission molecules: PSI, TPSI, PSSI, and TPSSI. We employed phenothiazine as an electron donor and 1,3-bis(dicyanomethylidene)indan as a strong electron acceptor in the synthesis process. Among them, TPSSI exhibited efficient type I reactive oxygen species generation, high photothermal conversion efficiency (45.44 %), and near-infrared emission. These observations can be attributed to the introduction of a triphenylamine electron donor group and a thiophene unit, which resulted in increased D-A strengths, a reduced singlet-triplet energy gap, and increased free intramolecular motion. TPSSI was loaded into bovine serum albumin to prepare biocompatible TPSSI nanoparticles (NPs). Our results have indicated that TPSSI NPs can target lipid droplets with negligible dark toxicity and can efficiently generate O2•- in hypoxic tumor environments. Moreover, TPSSI NPs selectively targeted 4T1 tumor tissues and exhibited a good PDT-PTT synergistic effect in vitro and in vivo. We believe that the successful preparation of multifunctional phototherapeutic agents will promote the development of efficient tumor diagnosis and treatment technologies. STATEMENT OF SIGNIFICANCE: The construction of a single phototherapeutic agent with photoluminescence, type I photodynamic therapy, and photothermal therapy functions, and its optimization remain challenging. In this study, we construct four donor-acceptor aggregation-induced emission molecules using phenothiazine as an electron donor and 1,3-Bis(dicyanomethylidene)indan as a strong electron acceptor. By optimizing the molecular structure, an integrated phototherapy agent with fluorescence imaging ability and high photodynamic / photothermal therapy performance was prepared. We believe that the successful preparation of multifunctional phototherapeutic agents will promote the development of efficient tumor diagnosis and treatment technology.

Bisbiguanide analogs induce mitochondrial stress to inhibit lung cancer cell invasion

Targeting cancer metabolism to limit cellular energy and metabolite production is an attractive therapeutic approach. Here, we developed analogs of the bisbiguanide, alexidine, to target lung cancer cell metabolism and assess a structure-activity relationship (SAR). The SAR led to the identification of two analogs, AX-4 and AX-7, that limit cell growth via G1/G0 cell-cycle arrest and are tolerated in vivo with favorable pharmacokinetics. Mechanistic evaluation revealed that AX-4 and AX-7 induce potent mitochondrial defects; mitochondrial cristae were deformed and the mitochondrial membrane potential was depolarized. Additionally, cell metabolism was rewired, as indicated by reduced oxygen consumption and mitochondrial ATP production, with an increase in extracellular lactate. Importantly, AX-4 and AX-7 impacted overall cell behavior, as these compounds reduced collective cell invasion. Taken together, our study establishes a class of bisbiguanides as effective mitochondria and cell invasion disrupters, and proposes bisbiguanides as promising approaches to limiting cancer metastasis.

Recent advances of aggregation‐induced emission in body surface organs

The surface organs mainly comprise the superficial layers of various parts of the mammalian body, including the skin, eyes, and ears, which provide solid protection against various threats to the entire body. Damage to surface organs could lead to many serious diseases or even death. Currently, despite significant advancements in this field, there remain numerous enigmas that necessitate expeditious resolution, particularly pertaining to diagnostic and therapeutic objectives. The advancements in nanomedicine have provided a significant impetus for the development of novel approaches in the diagnosis, bioimaging, and therapy of superficial organs. The aggregation‐induced emission (AIE) phenomenon, initially observed by Prof. Ben Zhong Tang, stands out due to its contrasting behavior to the aggregation‐caused quenching effect. This discovery has significantly revolutionized the field of nanomedicine for surface organs owing to its remarkable advantages. In this review of literature, we aim to provide a comprehensive summary of recent advances of AIE lumenogen (AIEgen)‐based nanoplatforms in the fields of detection, diagnosis, imaging, and therapeutics of surface organ‐related diseases and discuss their prospects in the domain. It is hoped that this review will help attract researchers’ attention toward the utilization of this field for the exploration of a wider range of biomedical and clinical applications.

De Novo Synthesis of Acridone-Based Zn-Metal-Organic Framework (Zn-MOF) as a Photocatalyst: Application for Visible Light-Mediated Oxidation of Sulfides and Enaminones

Acridone, a cyclic analogue of benzophenone that undergoes efficient intersystem crossing (ISC) to the triplet-excited state with near-unity quantum yield, was elaborated as a 3-connecting triacid linker, i.e., H3AcTA, to develop a photocatalytic metal-organic framework (MOF) for energy transfer applications; the triacid linker inherently features concave shapes, an attribute that is important for the construction of MOFs with significant porosity. Metal ion (Zn2+)-assisted self-assembly of the triacid yielded a Zn-MOF, i.e., Zn-AcTA, with a solvent-accessible volume of ca. 31%. The protection of the acridone chromophore in the MOF in conjunction with a wider cross-section of its absorption in the visible region renders the MOF an excellent heterogeneous photosensitizer for singlet oxygen (1O2) generation by energy transfer to the ground-state triplet oxygen (3O2). It is shown that the Zn-MOF can be applied as a photosensitizing catalyst for visible light-mediated oxidation of various sulfides to sulfoxides and enaminones to amino-esters via 1,2-acyl migration. It is further demonstrated that the photocatalyst can be easily recycled without any loss of catalytic activity and structural integrity. Based on mechanistic investigations, 1O2 is established as the reactive oxygen species in photocatalytic oxidation reactions. The results constitute the first demonstration of rational development of a photocatalytic MOF based on acridone for heterogeneous oxidations mediated by 1O2.

NIR ditriphenylamine Indole-BODIPY photosensitizer: synthesis, photodynamic therapy in A549 cells and two-photon fluorescence imaging in zebrafish

In this study, the ditriphenylamine Indole-BODIPY photosensitizer T2BDP-lyso was synthesized for near-infrared photodynamic therapy and two-photon fluorescence imaging. The photosensitizer T2BDP-lyso exhibits absorption above 700 nm and emission above 800 nm, respectively. Theoretical calculations show the energy gap from the excited state S1 to the excited state T2 is 0.14 eV, which indicated that the photosensitizer T2BDP-lyso could reach the triplet state by intersystem crossing from the singlet state. Under NIR light, the singlet oxygen yield of photosensitizer T2BDP-lyso was calculated to be 0.64 in CH2Cl2. The photosensitizer T2BDP-lyso can effectively produce reactive oxygen species in A549 cells and zebrafish under 660 nm light for 5 min. The photosensitizer T2BDP-lyso exhibited lower dark toxicity and higher phototoxicity (IC50 = 1.49 μM), as well as lysosomal targeting ability (Pearson coefficient = 0.89). In the AO/EB double staining assay simulating photodynamic therapy at the cellular level, 3 μM of T2BDP-lyso light for 10 min was effective in killing cancer cells. Moreover, the photosensitizer T2BDP-lyso has a large two-photon absorption cross section at 1050 nm, which was calculated to be 138.7 GM in THF by Z-scan method, and two-photon fluorescence imaging was performed in zebrafish. The above results indicate the potential application of the photosensitizer T2BDP-lyso in near-infrared photodynamic therapy and two-photon fluorescence imaging.

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Near-infrared metal agents assisting precision medicine: from strategic design to bioimaging and therapeutic applications

Metal agents have made incredible strides in preclinical research and clinical applications in recent years, but their short emission/absorption wavelengths continue to be a barrier to their distribution, therapeutic action, visual tracking, and efficacy evaluation. Nowadays, the near-infrared window (NIR, 650-1700 nm) provides a more accurate imaging and treatment option. Thus, there has been ongoing research focusing on developing multifunctional NIR metal agents for imaging and therapy that have deeper tissue penetration. The design, characteristics, bioimaging, and therapy of NIR metal agents are covered in this overview of papers and reports published to date. To start with, we focus on describing the structure, design strategies, and photophysical properties of metal agents from the NIR-I (650-1000 nm) to NIR-II (1000-1700 nm) region, in order of molecular metal complexes (MMCs), metal-organic complexes (MOCs), and metal-organic frameworks (MOFs). Next, the biomedical applications brought by these superior photophysical and chemical properties for more accurate imaging and therapy are discussed. Finally, we explore the challenges and prospects of each type of NIR metal agent for future biomedical research and clinical translation.

Tunable Nanoparticles with Aggregation-Induced Emission Heater for Precise Synergistic Photothermal and Thermodynamic Oral Cancer Therapy of Patient-Derived Tumor Xenograft

The fluorophores in the second near-infrared (NIR-II) biological window (1000 - 1700 nm) show great application prospects in the fields of biology and optical communications. However, both excellent radiative transition and nonradiative transition cannot be achieved simultaneously for the majority of traditional fluorophores. Herein, tunable nanoparticles formulated with aggregation-induced emission (AIE) heater are developed rationally. The system can be implemented via the development of an ideal synergistic system that can not only produce photothermal from nonspecific triggers but also trigger carbon radical release. Once accumulating in tumors and subsequently being irradiated with 808 nm laser, the nanoparticles (NMB@NPs) encapsulated with NMDPA-MT-BBTD (NMB) are splitted due to the photothermal effect of NMB, leading to the decomposition of azo bonds in the nanoparticle matrix to generate carbon radical. Accompanied by second near-infrared (NIR-II) window emission from the NMB, fluorescence image-guided thermodynamic therapy (TDT) and photothermal therapy (PTT) which significantly inhibited the growth of oral cancer and negligible systemic toxicity is achieved synergistically. Taken together, this AIE luminogens-based synergistic photothermal-thermodynamic strategy brings a new insight into the design of superior versatile fluorescent NPs for precise biomedical applications and holds great promise to enhance the therapeutic efficacy of cancer therapy.

A Native Drug-Free Macromolecular Therapeutic to Trigger Mutual Reinforcing of Endoplasmic Reticulum Stress and Mitochondrial Dysfunction for Cancer Treatment

Drug-free macromolecular therapeutics are promising alternatives to traditional drugs. Nanomedicines with multiple organelles targeting can potentially increase the efficacy. Herein, a drug-free macromolecular therapeutic was designed to formulate endoplasmic reticulum (ER) and mitochondria dual-targeting nanoparticles (EMT-NPs), which can synergistically elicit ER stress and mitochondrial dysfunction. In vitro experiments indicated that EMT-NPs could effectively enter ER and mitochondria at an approximate ratio of 2 to 3. Subsequently, EMT-NPs could upregulate ER stress-related protein expression (IRE1α, CHOP), boosting calcium ion (Ca²⁺) efflux and activating the caspase-12 signaling cascade in cancer cells. In addition, EMT-NPs induced direct oxidative stress in mitochondria; some mitochondrial-related apoptotic events such as decreased mitochondrial membrane potential (MMP), upregulation of Bax, cytochrome c release, and caspase-3 activation were also observed for tumor cells upon incubation with EMT-NPs. Furthermore, the leaked Ca²⁺ from ER could induce mitochondrial Ca²⁺ overloading to further augment cancer cell apoptosis. In brief, mitochondrial and ER signaling networks collaborated well to promote cancer cell death. Extended photoacoustic and fluorescence imaging served well for the treatment of in vivo patient-derived xenografts cancer model. This drug-free macromolecular strategy with multiple subcellular targeting provides a potential paradigm for cancer theranostics in precision nanomedicine.

A Versatile Theranostic Nanoplatform with Aggregation-Induced Emission Properties: Fluorescence Monitoring, Cellular Organelle Targeting, and Image-Guided Photodynamic Therapy

Photosensitizers (PSs) play a key role in the photodynamic therapy (PDT) of tumors. However, commonly used PSs are prone to intrinsic fluorescence aggregation-caused quenching and photobleaching; this drawback severely limits the clinical application of PDT, necessitating new phototheranostic agents. Herein, a multifunctional theranostic nanoplatform (named TTCBTA NP) is designed and constructed to achieve fluorescence monitoring, lysosome-specific targeting, and image-guided PDT. TTCBTA with a twisted conformation and D-A structure is encapsulated in amphiphilic Pluronic F127 to form nanoparticles (NPs) in ultrapure water. The NPs exhibit biocompatibility, high stability, strong near-infrared emission, and desirable reactive oxygen species (ROSs) production capacity. The TTCBTA NPs also show high-efficiency photo-damage, negligible dark toxicity, excellent fluorescent tracing, and high accumulation in lysosome for tumor cells. Furthermore, TTCBTA NPs are used to obtain fluorescence images with good resolution of MCF-7 tumors in xenografted BALB/c nude mice. Crucially, TTCBTA NPs present a strong tumor ablation ability and image-guided PDT effect by generating abundant ROSs upon laser irradiation. These results demonstrate that the TTCBTA NP theranostic nanoplatform may enable highly efficient near-infrared fluorescence image-guided PDT.

An Alkaline Phosphatase-Responsive Aggregation-Induced Emission Photosensitizer for Selective Imaging and Photodynamic Therapy of Cancer Cells

Fluorescence-guided photodynamic therapy (PDT) has been considered as an emerging strategy for precise cancer treatment by making use of photosensitizers (PSs) with reactive oxygen species (ROS) generation. Some efficient PSs have been reported in recent years, but multifunctional PSs that are responsive to cancer-specific biomarkers are rarely reported. In this study, we introduced a phosphate group as a cancer-specific biomarker of alkaline phosphatase (ALP) on a PS with the features of aggregation-induced emission (AIE) for cancer cell imaging and therapy. In cancer cells with high ALP expression, the phosphate group on the AIE probe is selectively hydrolyzed by ALP. Consequently, the hydrophobic probe residue is aggregated in aqueous media and gives a "turn on" fluorescent response. Moreover, fluorescence-guided PDT was realized by the aggregates of probe residue with strong ROS generation efficiency under white light irradiation. Overall, this work presents a strategy of applying ALP-responsive AIE PS for specific imaging cancer cells and succeeding with specific PDT upon the cancer biomarker stimulated responsive reactions.

How Exactly Do AIEgens Target Bacteria? Leveraging the Targeting Mechanism to Design Sensitive Fluorescent Immunosensors

Aggregation-induced emission luminogens (AIEgens) are promising candidates for bacterial imaging and detection because they can "Light-Up" pathogenic bacteria without complicated labeling or washing steps. However, there have been few in-depth analyses of the intrinsic mechanism underlying their utility as fluorescence probes for targeting bacteria. Therefore, using large-scale molecular dynamics simulations, we investigated the mechanism of their bacterial "Light-Up" behavior with N,N-diphenyl-4-(7-(pyridin-4-yl)benzo[c][1,2,5]thiadiazol-4-yl) aniline functionalized with 1-bromoethane (TBP-1). We propose that the triphenylamine motif of TBP-1, rather than the positively charged pyridine group, first contacts the cell membrane. After TBP-1 completely inserts into the cell membrane, the hydrophobic triphenylamine motif localizes in the hydrophobic core of the cell membrane, restricting the molecular variation of TBP-1, which induces the fluorescent "turn-on" and bacterial "Light-Up." On this basis, we established a heterogeneous lateral flow immunoassay (LFIA) for the detection of foodborne pathogens. The LFIA system showed improved sensitivity with a limit of detection as low as 10³ CFU mL^-1 and strong specificity. Our protocol opened an effective shortcut to the design of more efficient AIEgens and novel AIEgens-based immunoassays.

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.

Novel aggregation-induced emission-photosensitizers with built-in capability of mitochondria targeting and glutathione depletion for efficient photodynamic therapy

Owing to its non-invasive feature and excellent therapeutic effect, photodynamic therapy has received considerable interest in cancer therapy. However, the therapeutic efficacy of photodynamic therapy is limited by some intrinsic drawbacks of photosensitizers such as aggregation-caused quenching and non-specificity towards cellular organelles. Moreover, the overexpressed glutathione in tumour cells which exhibits a potent scavenging effect on reactive oxygen species generated during the photodynamic therapy process also reduces the efficacy of photodynamic therapy. Therefore, the synthesis of aggregation-induced emission based photosensitizers with cellular organelle targeting and glutathione-depletion capability is highly desirable in photodynamic therapy. Here, two new aggregation-induced emission based photosensitizers namely tetraphenylethylene-1-phenyvinyl-pyridine-phenylboronic acid (TPEPy-BA) and tetraphenylethylene-1-phenyvinyl-pyridine-phenylboronic acid pinacol ester (TPEPy-BE) were synthesized which easily aggregated under aqueous conditions and showed bright emission in the near infra-red region. Furthermore, these photosensitizers were encapsulated into an amphiphilic block copolymer (DSPE-PEG) to improve the aqueous stability and cellular internalization of photosensitizers. The developed photosensitizer nanoparticles showed high reactive oxygen species generation efficacy, mitochondria-targeting and glutathione-depletion capability. The results showed that tetraphenylethylene-1-phenyvinyl-pyridine-phenylboronic acid pinacol ester nanoparticles exhibited a highly efficient photodynamic ablation of MCF-7 cells compared to tetraphenylethylene-1-phenyvinyl-pyridine-phenylboronic acid nanoparticles, upon white light irradiation, due to its high intracellular reactive oxygen species generation efficiency and mitochondria-dysfunction ability. Moreover, tetraphenylethylene-1-phenyvinyl-pyridine-phenylboronic acid pinacol ester nanoparticles produced a glutathione-depleting adjuvant, quinone methide, which greatly reduced the glutathione level in cancer cells, thus enhancing the efficacy of photodynamic therapy. This study provides a new strategy for the synthesis of aggregation-induced emission based photosensitizers with combined mitochondria-targeting and glutathione-depletion capability for efficacious photodynamic therapy.

Near-infrared light activated photosensitizer with specific imaging of lipid droplets enables two-photon excited photodynamic therapy

Two-photon excited phototherapy has attracted considerable attention due to its advantages such as deeper penetration depth and higher spatial resolution. The lack of a high-performance photosensitizer with large two-photon absorption cross-sections and specific targeting ability makes the efficacy of phototherapy in the treatment of cancer unsatisfactory. Here, a new BODIPY-derived photosensitizer 6DBF2 is designed with two-photon photosensitization for two-photon excited photodynamic therapy in vivo. 6DBF2 possesses good two-photon absorption and efficient ¹O₂ generation upon near-infrared laser excitation. Excellent targeting specificities to lipid droplets of 6DBF2 without any encapsulation or modification at a low working concentration of 0.1 μM is in favor of efficient photodynamic therapy. In vitro cancer cell ablation and in vivo tumor ablation inside mice models upon two-photon irradiation in NIR demonstrate the outstanding therapeutic performance of 6DBF2 in two-photon excited photodynamic therapy. This work thus discusses a rare example of lipid droplets targeting two-photon excited photodynamic therapy for deep cancer tissue imaging and treatment under near-infrared light irradiation.

Apoptotic extracellular vesicles are metabolized regulators nurturing the skin and hair

Over 300 billion of cells die every day in the human body, producing a large number of endogenous apoptotic extracellular vesicles (apoEVs). Also, allogenic stem cell transplantation, a commonly used therapeutic approach in current clinical practice, generates exogenous apoEVs. It is well known that phagocytic cells engulf and digest apoEVs to maintain the body's homeostasis. In this study, we show that a fraction of exogenous apoEVs is metabolized in the integumentary skin and hair follicles. Mechanistically, apoEVs activate the Wnt/β-catenin pathway to facilitate their metabolism in a wave-like pattern. The migration of apoEVs is enhanced by treadmill exercise and inhibited by tail suspension, which is associated with the mechanical force-regulated expression of DKK1 in circulation. Furthermore, we show that exogenous apoEVs promote wound healing and hair growth via activation of Wnt/β-catenin pathway in skin and hair follicle mesenchymal stem cells. This study reveals a previously unrecognized metabolic pathway of apoEVs and opens a new avenue for exploring apoEV-based therapy for skin and hair disorders.

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Exogenous infused apoEVs are partly metabolized from the integumentary skin and hair follicles.

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ApoEVs activate Wnt/β-catenin pathway to facilitate their elimination in a wave-like pattern.

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Exercise can enhance apoEV metabolism through Wnt/β-catenin pathway.

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MSC-derived apoEVs promote wound healing and hair growth.

Molecular engineering to red-shift the absorption band of AIE photosensitizers and improve their ROS generation ability

Increasing the number of acceptors and extending their π-conjugation will red-shift the absorption-emission band, increase the maximum molar extinction coefficient, and improve the ROS generation ability of AIE-photosensitizers.

Engineering inducible biomolecular assemblies for genome imaging and manipulation in living cells

Genome architecture and organization play critical roles in cell life. However, it remains largely unknown how genomic loci are dynamically coordinated to regulate gene expression and determine cell fate at the single cell level. We have developed an inducible system which allows Simultaneous Imaging and Manipulation of genomic loci by Biomolecular Assemblies (SIMBA) in living cells. In SIMBA, the human heterochromatin protein 1α (HP1α) is fused to mCherry and FRB, which can be induced to form biomolecular assemblies (BAs) with FKBP-scFv, guided to specific genomic loci by a nuclease-defective Cas9 (dCas9) or a transcriptional factor (TF) carrying tandem repeats of SunTag. The induced BAs can not only enhance the imaging signals at target genomic loci using a single sgRNA, either at repetitive or non-repetitive sequences, but also recruit epigenetic modulators such as histone methyltransferase SUV39H1 to locally repress transcription. As such, SIMBA can be applied to simultaneously visualize and manipulate, in principle, any genomic locus with controllable timing in living cells.

Aggregation-Induced Emission Luminogens for Enhanced Photodynamic Therapy: From Organelle Targeting to Tumor Targeting

Photodynamic therapy (PDT) has attracted much attention in the field of anticancer treatment. However, PDT has to face challenges, such as aggregation caused by quenching of reactive oxygen species (ROS), and short 1O2 lifetime, which lead to unsatisfactory therapeutic effect. Aggregation-induced emission luminogen (AIEgens)-based photosensitizers (PSs) showed enhanced ROS generation upon aggregation, which showed great potential for hypoxic tumor treatment with enhanced PDT effect. In this review, we summarized the design strategies and applications of AIEgen-based PSs with improved PDT efficacy since 2019. Firstly, we introduce the research background and some basic knowledge in the related field. Secondly, the recent approaches of AIEgen-based PSs for enhanced PDT are summarized in two categories: (1) organelle-targeting PSs that could cause direct damage to organelles to enhance PDT effects, and (2) PSs with tumor-targeting abilities to selectively suppress tumor growth and reduce side effects. Finally, current challenges and future opportunities are discussed. We hope this review can offer new insights and inspirations for the development of AIEgen-based PSs for better PDT effect.

Nonlinear optical properties and optimization strategies of D-π-A type phenylamine derivatives in the near-infrared region

Modifying simple molecular structures to significantly improve nonlinear optical (NLO) performance is a primary prerequisite for scientific research. Based on the four phenylamine derivatives reported in previous studies, we designed four organic nonlinear molecules by changing the acceptor group and π-linker. (Time-dependent) density functional theory (DFT/TD-DFT) was performed on molecular geometry optimization, the contribution of π electrons to the bond order, linear and two-photon absorption (TPA) spectra, the intra-molecular charge transfer matrix (CTM), and NLO coefficients. These aspects were considered to analyze in detail how the structural modification of acceptors and π-linkers affects NLO characteristics. The three modification methods were: adding a carbonyl group at the junction of the π-linker and the acceptor group, adding a carbonyl group and a nitrogen atom to the acceptor group, and replacing the quinolinone with a pyrenyl group as the π-linker. The latter two methods can significantly reduce the excitation energy and enhance the intensity of intra-molecular charge transfer during the two-photon transition. The maximum TPA cross-sections and wavelengths of the designed molecules are DPPM (84722.6 GM, 815.7 nm) and DDPM (21600.6 GM, 781.3 nm). These two molecules have large TPA cross-sections in the near-infrared region, which renders them as possible NLO materials with broad application prospects.

Surface modification of ZnIn2S4 layers to realize energy-transfer-mediated photocatalysis

Photocatalytic selective aerobic oxidation reactions are crucial in designing advanced organic intermediates, but suffer from low conversion efficiency. Hence, activating O2 to create suitable reactive oxygen species, such as singlet oxygen (1O2), can significantly increase the yield of desired products. Herein, using ZnIn2S4 nanosheets as a model system, we build a surface-modified theoretical structure, where a surface-covered non-conductive macromolecular chain, polyvinyl pyrrolidone (PVP), is bound to ZnIn2S4 and influences the O2 adsorption process. PVP on the surface significantly changes the electronic structure and suppresses electron conduction of ZnIn2S4 nanosheets. Therefore, abundantly photogenerated and long-lived species transfer their energy to physically absorbed O2 to efficiently generate 1O2, which can oxidize sulphides into their corresponding sulphoxides. For sulphoxidation of different sulphides, surface modification brings a 3-9-fold increase in conversion efficiency and high selectivities ≥98%. This study provides a feasible way of boosting 1O2-generation-related photocatalytic reactions.

Advances in Anti-Cancer Activities of Flavonoids in Scutellariae radix: Perspectives on Mechanism

Despite encouraging progresses in the development of novel therapies, cancer remains the dominant cause of disease-related mortality and has become a leading economic and healthcare burden worldwide. Scutellariae radix (SR, Huangqin in Chinese) is a common herb used in traditional Chinese medicine, with a long history in treating a series of symptoms resulting from cancer, like dysregulated immune response and metabolic abnormalities. As major bioactive ingredients extracted from SR, flavonoids, including baicalein, wogonin, along with their glycosides (baicalin and wogonoside), represent promising pharmacological and anti-tumor activities and deserve extensive research attention. Emerging evidence has made great strides in elucidating the multi-targeting therapeutic mechanisms and key signaling pathways underlying the efficacious potential of flavonoids derived from SR in the field of cancer treatment. In this current review, we aim to summarize the pharmacological actions of flavonoids against various cancers in vivo and in vitro. Moreover, we also make a brief summarization of the endeavor in developing a drug delivery system or structural modification to enhance the bioavailability and biological activities of flavonoid monomers. Taken together, flavonoid components in SR have great potential to be developed as adjuvant or even primary therapies for the clinical management of cancers and have a promising prospect.

Comprehensive Thione-Derived Perylene Diimides and Their Bio-Conjugation for Simultaneous Imaging, Tracking, and Targeted Photodynamic Therapy

In this study, the chromophore 3,4,9,10-perylenetetracarboxylic diimide (PDI) is anchored with phenyl substituents at the imide N site, followed by thionation, yielding a series of thione products 1S-PDI-D, 2S-cis-PDI-D, 2S-trans-PDI-D, 3S-PDI-D, and 4S-PDI-D, respectively, with n = 1, 2, 3, and 4 thione. The photophysical properties are dependent on the number of anchored thiones, where the observed prominent lower-lying absorption is assigned to the S₀ → S₂(ππ*) transition and is red-shifted upon increasing the number of thiones; the lowest-lying excited state is ascribed to a transition-forbidden S₁(nπ*) configuration. All nS-PDIs are non-emissive in solution but reveal an excellent two-photon absorption cross-section of >800 GM. Supported by the femtosecond transient absorption study, the S₁(nπ*) → T₁(ππ*) intersystem crossing (ISC) rate is > 10¹² s^-1, resulting in ∼100% triplet population. The lowest-lying T₁(ππ*) energy is calculated to be in the order of 1S-PDI-D > 2S-cis-PDI-D ∼ 2S-trans-PDI-D > 3S-PDI-D > 4S-PDI-D, where the T₁ energy of 1S-PDI-D (1.10 eV) is higher than that (0.97 eV) of the ¹O₂ ¹Δ_g state. 1S-PDI-D is further modified by either conjugation with peptide FC131 on the two terminal sides, forming 1S-FC131, or linkage with peptide FC131 and cyanine5 dye on each terminal, yielding Cy5-1S-FC131. In vitro experiments show power of 1S-FC131 and Cy5-1S-FC131 in recognizing A549 cells out of other three lung normal cells and effective photodynamic therapy. In vivo, both molecular composites demonstrate outstanding antitumor ability in A549 xenografted tumor mice, where Cy5-1S-FC131 shows superiority of simultaneous fluorescence tracking and targeted photodynamic therapy.

Molecularly engineered AIEgens with enhanced quantum and singlet-oxygen yield for mitochondria-targeted imaging and photodynamic therapy

Luminogens characteristic of aggregation-induced emission (AIEgens) have been extensively exploited for the development of imaging-guided photodynamic therapeutic (PDT) agents. However, intramolecular rotation of donor-acceptor (D-A) type AIEgens favors non-radiative decay of photonic energy which results in unsatisfactory fluorescence quantum and singlet oxygen yields. To address this issue, we developed several molecularly engineered AIEgens with partially "locked" molecular structures enhancing both fluorescence emission and the production of triplet excitons. A triphenylphosphine group was introduced to form a D-A conjugate, improving water solubility and the capacity for mitochondrial localization of the resulting probes. Experimental and theoretical analyses suggest that the much higher quantum and singlet oxygen yield of a structurally "significantly-locked" probe (LOCK-2) than its "partially locked" (LOCK-1) and "unlocked" equivalent (LOCK-0) is a result of suppressed AIE and twisted intramolecular charge transfer. LOCK-2 was also used for the mitochondrial-targeting, fluorescence image-guided PDT of liver cancer cells.

Aggregation-induced emission photosensitizer-based photodynamic therapy in cancer: from chemical to clinical

Cancer remains a serious threat to human health owing to the lack of effective treatments. Photodynamic therapy (PDT) has emerged as a promising non-invasive cancer treatment that consists of three main elements: photosensitizers (PSs), light and oxygen. However, some traditional PSs are prone to aggregation-caused quenching (ACQ), leading to reduced reactive oxygen species (ROS) generation capacity. Aggregation-induced emission (AIE)-PSs, due to their distorted structure, suppress the strong molecular interactions, making them more photosensitive in the aggregated state instead. Activated by light, they can efficiently produce ROS and induce cell death. PS is one of the core factors of efficient PDT, so proceeding from the design and preparation of AIE-PSs, including how to manipulate the electron donor (D) and receptor (A) in the PSs configuration, introduce heavy atoms or metal complexes, design of Type I AIE-PSs, polymerization-enhanced photosensitization and nano-engineering approaches. Then, the preclinical experiments of AIE-PSs in treating different types of tumors, such as ovarian cancer, cervical cancer, lung cancer, breast cancer, and its great potential clinical applications are discussed. In addition, some perspectives on the further development of AIE-PSs are presented. This review hopes to stimulate the interest of researchers in different fields such as chemistry, materials science, biology, and medicine, and promote the clinical translation of AIE-PSs.

Methyl Viologens of Bis-(4'-Pyridylethynyl)Arenes - Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology

A series of bis-(4'-pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis-N-methylpyridinium compound showed a larger two-photon absorption cross-section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds-DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene-analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi-faceted features, in combination with its two-photon absorption properties, suggest it to be a promising lead compound for development of novel light-activated theranostic agents.

Molecular to Supramolecular Self-Assembled Luminogens for Tracking the Intracellular Organelle Dynamics

Deciphering the dynamics of intracellular organelles has gained immense attention due to their subtle control over diverse, complex biological processes such as cellular metabolism, energy homeostasis, and autophagy. In this context, molecular materials, including small-organic fluorescent probes and their supramolecular self-assembled nano-/microarchitectures, have been employed to explore the diverse intracellular biological events. However, only a handful of fluorescent probes and self-assembled emissive structures have been successfully used to track different organelle's movements, circumventing the issues related to water solubility and long-term photostability. Thus, the water-soluble molecular fluorescent probes and the water-dispersible supramolecular self-assemblies have emerged as promising candidates to explore the trafficking of the organelles under diverse physiological conditions. In this review, we have delineated the recent progress of fluorescent probes and their supramolecular self-assemblies for the elucidation of the dynamics of diverse cellular organelles with a special emphasis on lysosomes, lipid droplets, and mitochondria. Recent advancement in fluorescence lifetime and super-resolution microscopy imaging has also been discussed to investigate the dynamics of organelles. In addition, the fabrication of the next-generation molecular to supramolecular self-assembled luminogens for probing the variation of microenvironments during the trafficking process has been outlined.

Unusual Electron Donor-Acceptor sequenced NIR AIEgen for Highly Efficient Mitochondria-Targeted Cancer Cell Photodynamic Therapy

Photodynamic therapy (PDT) is recognized to be a promising strategy for anticancer treatment. Considering the progressive application of PDT in clinical trials, highly efficient and photostable photosensitizers (PSs) are in strong demand. Aggregation-induced emission (AIE) based PSs are promising phototheranostic materials for tumor imaging and PDT due to their high fluorescence efficiency and photostability. Herein, a mitochondria-targeted PS, TPA-2TCP with AIE characteristics is developed by adopting an acceptor-π-donor-π-acceptor (A-π-D-π-A) structure. The untypical sequence of the electron donors and electron acceptors endows the derived AIE PS with evident redshift of the absorption and emission, and efficient generation of reactive oxygen species. With the positively charged pyridinium groups, nanoparticulated AIE PS (TPA-2TCP NPs) exhibits high cell binding efficiency towards 4T1 breast cancer cells, leading to the massive cell death via the apoptotic pathway under white light irradiation, demonstrating its potential application in cancer imaging and PDT.

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.

Improved Effect of Metal Coordination on Molecular Oxygen Activation for Selective Aerobic Photooxidation

A pyridinium-based complex with environment-friendly and earth-abundant Zn^II ion was synthesized and explored as a green catalyst applied in activating molecular oxygen for the simple and efficient photooxidation of alcohols into aldehydes under additive-free and mild conditions. The metal coordination was conducive to promoting the electron transfer efficiency and introducing the heavy-atom effect for the increased generation of ⋅O₂ ^- and ¹ O₂ . Accordingly, improved photocatalytic performance of this complex compared to its precursor, no matter activity or selectivity, was obtained, facilitating the transformation of alcohols into aldehydes in a sustainable way.