Aggregation-Induced Emission Photosensitizers: From Molecular Design to Photodynamic Therapy

Aggregation assisted enhancement of singlet oxygen generation by 4-ethynylphenyl substituted porphyrin photosensitizer for photodynamic therapy

Modulating the photophysical properties of photosensitizers is an effective approach to enhance singlet oxygen generation for photodynamic therapy. Porphyrins are the most widely used photosensitizers due to their biocompatible nature. Aggregation-induced emission (AIE) characteristics of photosensitizers are one of the advantageous features that will enhance fluorescence, intersystem crossing, and efficient triplet state generation. Herein, we demonstrate two glycosylated porphyrin photosensitizers, ZnGEPOH (with two ethynyl groups) and ZnGPOH (without two ethynyl groups), which exhibit AIE. Detailed studies revealed that ZnGEPOH exhibited a two-fold increase in singlet oxygen production than ZnGPOH due to AIE. The photo-cytotoxicity of ZnGPOH and ZnGEPOH were evaluated using cancer cell lines A549 and AGS. ZnGEPOH shows superior photo-cytotoxicity with cell viability of 21% and 19% for A549 and AGS, respectively, at 250 μg/mL concentration in 48 h. Moreover, ZnGEPOH exhibits minimal photo-cytotoxicity towards the control cell line HEK 293.

Evaluation of the alkyl chain length and photocatalytic antibacterial performance of cation g-C3N4

Several cation graphite carbon nitrides (g-C3N4-(CH2)n-ImI+) were synthesized by chemically attaching imidazolium appended alkane chains with different lengths (n = 2, 4, 8, 12 and 16) to g-C3N4. The introduction of a cation segment potentially improved the interaction between the carbon material and Gram negative (MDR-A. baumannii) and Gram positive (S. aureus) bacteria as characterized by ζ potential measurement. Short alkane chain (carbon numbers of 2, 4 and 8) carbon materials displayed relatively stronger bacterial interactions compared to long alkane chain bearing ones (n = 12 and 16). In addition, short chain carbon materials (g-C3N4-(CH2)4-ImI+) displayed relatively higher photocatalytic reactive oxygen species (1O2, ˙O2- and ˙OH) production efficiency. Bacterial interaction and ROS production efficiency synergistically contribute to photocatalytic antibacterial performance. The current data revealed that g-C3N4 with short flexible cations attached exhibited bacterial interaction and ROS production. Among these synthesized materials, g-C3N4-(CH2)4-ImI+ exhibited the most pronounced photocatalytic antibacterial efficiency (>99%).

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

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

An AIE fungal vacuole membrane probe toward species differentiation, vacuole formation visualization, and targeted photodynamic therapy

Vacuoles are unique organelles of fungi. The development of probes targeting the vacuoles membrane will enable visualization of physiological processes and precise diagnosis and therapy. Herein, a zwitterionic molecule, MXF-R, comprising of an aggregation-induced emission (AIE) photosensitizing unit and an antibiotic moxifloxacin, was found capable of specifically imaging vacuole membrane and using for targeted antifungal therapy. MXF-R demonstrated a higher signal-to-noise ratio, stronger targeting capability, and better biocompatibility than the commercial probe FM4-64. By using MXF-R, real-time visualization of vacuole formation during Candida albicans (C. albicans) proliferation was achieved. More importantly, owing to its varying staining ability towards different fungus, MXF-R could be used to quickly identify C. albicans in mixed strains by fluorescence imaging. Moreover, MXF-R exhibits a remarkable ability to generate reactive oxygen species under white light, effectively eradicating C. albicans by disrupting membrane structure. This antifungal therapy of membrane damage is more effective than clinical drug fluconazole. Therefore, this work not only presents the initial discovery of a probe targeting vacuolar membrane, but also provides a way to develop novel materials to realize integrated diagnosis and therapy.

Efficient Delivering of a Photodynamic Therapy Drug into Cellular Membranes Rationalized by Molecular Dynamics

Photodynamic therapy (PDT) represents a most attractive therapeutic strategy to reduce side-effects of chemotherapy and improve the global quality of life of patients. Yet, many PDT drugs suffer from poor bioavailability and cellular intake, and thus, drug-delivering strategies are mandatory. In this article, we rationalize the behavior of a temoporfin-based PDT drug, commercialized under the name of Foscan, complexed by two β-cyclodextrin units, acting as drug carriers, in the presence of a lipid bilayer. Our all-atom simulations have unequivocally shown the internalization of the drug-delivering complex and suggest its possible spontaneous dissociation in the lipid bilayer core. The factors favoring penetration and dissociation have also been analyzed, together with membrane perturbation due to the interaction with the drug carrier complex. Our results confirm the suitability of this encapsulation strategy for PDT and rationalize the experimental results concerning its efficacy.

Tracking Microenvironmental Response on Self-Assembled Phthalocyanine Systems - Adaptive and Non-Adaptive Antibacterial Photosensitization

Self-assembly has proven to be one of the effective methods for the formation of nanoscale therapeutics without the need to use nanodelivery systems. Such minimal models of supramolecular systems formed from amphiphilic photosensitizers (PS) have recently emerged as a new class of photoactive systems, providing unique and in some cases superior activities. Although the mechanism of photogenerated reactive oxygen species (ROS) in such systems is studied and to a certain extent understood, there are very limited studies investigating the influence of intricate environmental factors, including those occurring in the cellular environment, on the self-assembly and thus the activity of the system. Understanding the optimal conditions for the formation of active PS aggregates is an important area of research in the field of photodynamic therapy (PDT), as it is directly linked to the optimal treatment dose. In this study, we describe the synthesis, self-assembly properties, photophysical characterization, and photobiological efficacy of structurally closely related low-symmetry phthalocyanine derivatives. Studying the decay behavior of the PS fluorescence lifetime in the presence of molecular crowders and different bacterial strains, we found that certain derivatives exhibited adaptive behavior and change in activity, while others demonstrated non-adaptive characteristics.

Mussel-like polydopamine-assisted aggregation-induced emission nanodot for enhanced broad-spectrum antimicrobial activity: In vitro and in vivo validation

Emerging luminogens with aggregation-induced emission properties, namely AIEgens, demonstrated excellent anti-bacteria activity potential. However, their application still limited by the low antibacterial activity caused by the poor binding with bacteria. Polydopamine (PDA), an important biological macromolecule, possesses superior adhesion ability toward various material surface, including bacteria. In this study, the novel mussel-like PDA-assisted AIE Nanodot was proposed, achieving with robust bacterial binding ability and enhanced broad-spectrum antibacterial activity. Binding ability inherited from the PDA enables the constructed PDA-assisted AIE Nanodot to adhere efficiently to the bacterial membrane surface. Meanwhile, the AIE properties endowed them with monitoring capability, allowing for tracking their interaction with bacteria through facile fluorescence imaging in real time. More importantly, excellent killing of both Gram-positive and Gram-negative bacteria were successfully achieved in vitro antibacterial tests with excellent biocompatibility. Furthermore, in the treatment of Methicillin-resistant S. aureus (MRSA)-infected mouse-wound model, the mice exhibited accelerated wound healing with low bacterial load. This novel integrated strategy introduced a simple but effectively design to enhance the binding and antibacterial ability of AIEgens and would diversify the existing pool of antibacterial agents.

Chitosan-based self-healing hydrogel dressing for wound healing

Skin has strong self-regenerative capacity, while severe skin defects do not heal without appropriate treatment. Therefore, in order to cover the wound sites and hasten the healing process, wound dressings are required. Hydrogels have emerged as one of the most promising candidates for wound dressings because of their hydrated and porous molecular structure. Chitosan (CS) with biocompatibility, oxygen permeability, hemostatic and antimicrobial properties is beneficial for wound treatment and it can generate self-healing hydrogels through reversible crosslinks, from dynamic covalent bonding, such as Schiff base bonds, boronate esters, and acylhydrazone bonds, to physical interactions like hydrogen bonding, electrostatic interaction, ionic bonding, metal-coordination, host-guest interactions, and hydrophobic interaction. Therefore, various chitosan-based self-healing hydrogel dressings have been prepared in recent years to cope with increasingly complex wound conditions. This review's objective is to provide comprehensive information on the self-healing mechanism of chitosan-based hydrogel wound dressings, discuss their advanced functions including antibacterial, conductive, anti-inflammatory, anti-oxidant, stimulus-responsive, hemostatic/adhesive and controlled release properties, further introduce their applications in the promotion of wound healing in two categories: acute and chronic (infected, burn and diabetic) wounds, and finally discuss the future perspective of chitosan-based self-healing hydrogel dressings for wound healing.

Advances in biomimetic AIE nanoparticles for diagnosis and phototherapy

This minireview provides an overview of the recent advancements in the development of biomimetic Aggregation-Induced Emission (AIE) nanoparticles and their applications in disease diagnosis, phototherapy, and photoimmunotherapy. AIE nanoparticles can be engineered to enable efficient image-guided photodynamic and photothermal therapies, however, challenges related to immune defense and target specificity persist. To overcome these, coating biomimetic materials on the surface of AIE nanoparticles, which mimic the features and functions of native cells, have emerged as a promising solution. This minireview will highlight the synthesis strategies and discuss the biomedical application of biomimetic AIE nanoparticles.

A structure-guided strategy to design Golgi apparatus-targeted type-I/II aggregation-induced emission photosensitizers for efficient photodynamic therapy

The Golgi apparatus (GA) is a vital target for anticancer therapy due to its sensitivity against reactive oxygen species (ROS)-induced oxidative stress that could lead to cell death. In this study, we designed a series of aggregation-induced emission (AIE)-based photosensitizers (TPAPyTZ, TPAPyTC, TPAPyTM, and TPAPyTI) carrying different ROS with selective GA-targeted ability. The in vitro study showed that TPAPyTZ and TPAPyTC displayed strong AIE characteristics, robust type-I/II ROS production capabilities, specific GA-targeted, high photostability, and high imaging quality. The cell-uptake of TPAPyTZ was found primarily through an energy-dependent caveolae/raft-mediated endocytosis pathway. Remarkably, TPAPyTZ induced GA-oxidative stress, leading to GA fragmentation, downregulation of GM130 expression, and activation of mitochondria caspase-related apoptosis during photodynamic therapy (PDT). In vivo experiments revealed that TPAPyTZ significantly inhibited tumor proliferation under lower-intensity white light irradiation with minimal side effects. Overall, our work presents a promising strategy for designing AIEgens for fluorescence imaging-guided PDT. Additionally, it enriched the collection of GA-targeted leads for the development of cancer theranostics capable of visualizing dynamic changes in the GA during cancer cell apoptosis, which could potentially enable early diagnosis applications in the future. STATEMENT OF SIGNIFICANCE: AIE luminogens (AIEgens) are potent phototheranostic agents that can exhibit strong fluorescence emission and enhance ROS production in the aggregate states. In this study, through the precise design of photosensitizers with four different electron-acceptors, we constructed a series of potent AIEgens (TPAPyTZ, TPAPyTC, TPAPyTM, and TPAPyTI) with strong fluorescence intensity and ROS generation capacity. Among them, TPAPyTZ with an extended π-conjugation displayed the strongest ROS generation ability and anti-tumor activity, resulting in an 88 % reduction in tumor weight. Our studies revealed that the enhanced activity of TPAPyTZ may be due to its unique Golgi apparatus (GA)-targeted ability, which causes GA oxidative stress followed by effective cancer cell apoptosis. This unique GA-targeted feature of TPAPyTZ remains rare in the reported AIEgens, which mainly target organelles such as lysosome, mitochondria, and cell membrane. The successful design of a GA-targeted and potent AIEgen could enrich the collection of GA-targeted luminogens, providing a lead theranostic for the further development of fluorescence imaging-guided PDT, and serving as a tool to explore the potential mechanism and discover new GA-specific drug targets.

Metal organic framework-based variable-size nanoparticles for tumor microenvironment-responsive drug delivery

Nanoparticles (NPs) have been designed for the treatment of tumors increasingly. However, the drawbacks of single-size NPs are still worth noting, as their circulation and metabolism in the blood are negatively correlated with their accumulation at the tumor site. If the size of single-size NPs is too small, it will be quickly cleared in the blood circulation, while, the size is too large, the distribution of NPs in the tumor site will be reduced, and the widespread distribution of NPs throughout the body will cause systemic toxicity. Therefore, a class of variable-size NPs with metal organic frameworks (MOFs) as the main carrier, and size conversion in compliance with the characteristics of the tumor microenvironment (TME), was designed. MOF-based variable-size NPs can simultaneously extend the time of blood circulation and metabolism, then enhance the targeting ability of the tumor site. In this review, MOF NPs are categorized and exemplified from a new perspective of NP size variation; the advantages, mechanisms, and significance of MOF-based variable-size NPs were summarized, and the potential and challenges in delivering anti-tumor drugs and multimodal combination therapy were discussed.

Cinnamyl Chalcone Based AIE Fluorescent Probes for Sensitive Detection of Hydrazine and its Application in Living Cells

Widely utilized in the chemical industry and agriculture, hydrazine is easily absorbed by living things and can cause physical harm when in touch for an extended period of time. As a result, a novel cinnamaldehyde chalcone C5 was produced by Friedel Crafts process and aldol condensation reaction. Triphenylamine was used as the raw material for hydrazine determination in both reactions. Chalcone C5 exhibits significant AIE behavior in a mixed mixture of ethanol and water in addition to having great selectivity and a low detection limit (0.119 nm) for hydrazine. The solvent effect test revealed a linear relationship between the Stokes shift of C5 in the solvent and the rise in solvent orientation polarization. It is important to note that C5 is not harmful to MCF-7 cells, mouse kidney cells, or pig kidney cells. Furthermore, research on cell imaging has demonstrated that probe C5 may be utilized to image the fluorescence of hydrazine in active MCF-7 cells.

Wavelength Division Multiplexing-Based High-Sensitivity Surface Plasmon Resonance Imaging Biosensor for High-Throughput Real-Time Molecular Interaction Analysis

In this study, we report the successful development of a novel high-sensitivity intensity-based Surface Plasmon Resonance imaging (SPRi) biosensor and its application for detecting molecular interactions. By optimizing the excitation wavelength and employing a wavelength division multiplexing (WDM) algorithm, the system can determine the optimal excitation wavelength based on the initial refractive index of the sample without adjusting the incidence angle. The experimental results demonstrate that the refractive index resolution of the system reaches 1.77×10-6 RIU. Moreover, it can obtain the optimal excitation wavelength for samples with an initial refractive index in the range of 1.333 to 1.370 RIU and accurately monitor variations within the range of 0.0037 RIU without adjusting the incidence angle. Additionally, our new SPRi technique realized real-time detection of high-throughput biomolecular binding processes, enabling analysis of kinetic parameters. This research is expected to advance the development of more accurate SPRi technologies for molecular interaction analysis.

Bioconjugation and Reaction-Induced Tumor Therapy via Alkynamide-Based Thiol-Yne Click Reaction

Ferroptosis is associated with the occurrence and development of many diseases, which is the result of an imbalance in cellular metabolism and oxidation-reduction balance. Therefore, it is an effective therapeutic strategy that simultaneously regulating the intracellular oxidation-reduction system. Herein, a click reaction of alkynylamide with thiol groups in the presence of amine or in PBS (pH = 7.4) is developed, which can react efficiently with thiol substances, such as cysteine (Cys), glutathione (GSH), and bovine serum albumin (BSA). Notably, MBTB-PA, an aggregation-induced emission (AIE) photosensitizer with an alkynylamide unit, is synthesized and its intracellular behavior is visualized in situ by fluorescence imaging, demonstrating its excellent ability to target the endoplasmic reticulum. Furthermore, MBTB-PA reacted with proteins in tumor cells, consumed reducing substances, and triggered intracellular oxidative stress, resulting in cell death. Based on this reaction therapy strategy, click reaction is combined with photodynamic therapy to achieve effective killing of tumor cells by simultaneously raising the intracellular oxidative state and reducing the reductive state. This work not only develops an application of click reaction of alkynamide with thiol in bioconjugation and anti-tumor therapy, but also provides feasible ideas for organic reactions in the exploration of organisms.

Anion-π+ AIEgens for Fluorescence Imaging and Photodynamic Therapy

Fluorescence imaging-guided photodynamic therapy (PDT) has attracted extensive attention due to its potential of real-time monitoring the lesion locations and visualizing the treatment process with high sensitivity and resolution. Aggregation-induced emission luminogens (AIEgens) show enhanced fluorescence and reactive oxygen species (ROS) generation after cellular uptake, giving them significant advantages in bioimaging and PDT applications. However, most AIEgens are unfavorable for the application in organisms due to their severe hydrophobicity. Anion-π+ type AIEgens carry intrinsic charges that can effectively alleviate their hydrophobicity and improve their binding capability to cells, which is expected to enhance the bioimaging quality and PDT performance. This concept summarizes the applications of anion-π+ type AIEgens in fluorescence imaging, fluorescence imaging-guided photodynamic anticancer and antimicrobial therapy in recent years, hoping to provide some new ideas for the construction of robust photosensitizers. Finally, the current problems and future challenges of anion-π+ AIEgens are discussed.

PEGylated AIEgens for dual sensing of ATP and H2S and cancer cells photodynamic therapy

Fluorescent sensors have been widely applied for biosensing, but probes for both multiple analytes sensing and photodynamic therapy (PDT) effect are less reported. In this article, we reported three AIE-based probes anchored with different mass-weight polyethylene glycol (PEG) tails, i.e., TPE-PEG160, TPE-PEG350, and TPE-PEG750, for both adenosine-5'-triphosphate (ATP) and hydrogen sulfide (H2S) detection and also cancer cells photodynamic therapy. TPE-PEGns (n = 160, 350 and 750) contain the tetraphenylethylene-based fluorophore core, the pyridinium and amide anion binding sites, the H2S cleavable disulfide bond, and the hydrophilic PEG chain. They exhibit a good amphiphilic property and can self-assemble nona-aggregation with a moderated red emission in an aqueous solution. Importantly, the size of aggregation, photophysical property, sensing ability and photosensitivity of these amphiphilic probes can be controlled by tuning the PEG chain length. Moreover, the selected probe TPE-PEG160 has been successfully used to detect environmental H2S and image ATP levels in living cells, and TPE-PEG750 has been used for photodynamic therapy of tumor cells under light irradiation.

Organo-Ptii Complexes for Potent Photodynamic Inactivation of Multi-Drug Resistant Bacteria and the Influence of Configuration

PtII based organometallic photosensitizers (PSs) have emerged as novel potent photodynamic inactivation (PDI) reagents through their enhanced intersystem crossing (ISC) processes. Currently, few PtII PSs have been investigated as antibacterial materials, with relatively poor performances reported and with structure-activity relationships not well described. Herein, a pair of configurational isomers are reported of Bis-BODIPY (4,4-difluoro-boradizaindacene) embedded PtII PSs. The cis-isomer (cis-BBP) displayed enhanced 1O2 generation and better bacterial membrane anchoring capability as compared to the trans-isomer (trans-BBP). The effective PDI concentrations (efficiency > 99.9%) for cis-BBP in Acinetobacter baumannii (multi-drug resistant (MDR)) and Staphylococcus aureus are 400 nM (12 J cm-2) and 100 nM (18 J cm-2), respectively; corresponding concentrations and light doses for trans-BBP in the two bacteria are 2.50 µM (30 J cm-2) and 1.50 µM (18 J cm-2), respectively. The 50% and 90% minimum inhibitory concentration (MIC50 and MIC90) ratio of trans-BBP to cis-BBP is 22.22 and 24.02 in A. baumannii (MDR); 21.29 and 22.36 in methicillin resistant S. aureus (MRSA), respectively. Furthermore, cis-BBP displays superior in vivo antibacterial performance, with acceptable dark and photoinduced cytotoxicity. These results demonstrate cis-BBP is a robust light-assisted antibacterial reagent at sub-micromolecular concentrations. More importantly, configuration of PtII PSs should be an important issue to be considered in further PDI reagents design.

Mitochondria-targeted pentacyclic triterpene NIR-AIE derivatives for enhanced chemotherapeutic and chemo-photodynamic combined therapy

Complexes formed by combining pentacyclic triterpenes (PTs) with Aggregation-Induced Emission luminogens (AIEgens), termed pentacyclic triterpene-aggregation induced emission (PT-AIEgen) complexes, merge the chemotherapeutic properties of PTs with the photocytotoxicity of AIEgens. In this study, we synthesized derivatives by connecting three types of triphenylamine (TPA) pyridinium derivatives with three common pentacyclic triterpenes. Altering the connecting group between the electron donor TPA and the electron acceptor pyridinium resulted in increased production of reactive oxygen species (ROS) by PT-AIEgens and a red-shift in their fluorescence emission spectra. Importantly, the fluorescence emission spectra of BA-3, OA-3, and UA-3 extended into the near-infrared (NIR) range, enabling NIR-AIE imaging of the sites where the derivatives aggregated. The incorporation of the pyridinium structure improved the mitochondrial targeting of PT-AIEgens, enhancing mitochondrial pathway-mediated cell apoptosis and improving the efficiency of chemotherapy (CT) and chemo-photodynamic combined therapy (CPCT) both in vivo and in vitro. Cellular fluorescence imaging demonstrated rapid cellular uptake and mitochondrial accumulation of BA-1 (-2, -3). Cell viability experiments revealed that BA-1 (-2), OA-1 (-2), and UA-1 (-2) exhibited superior CT cytotoxicity compared to their parent drugs, with BA-1 showing the most potent inhibitory effect on HeLa cells (IC50 = 1.19 μM). Furthermore, HeLa cells treated with BA-1 (1 μM), BA-2 (1.25 μM), and BA-3 (1 μM) exhibited survival rates of 2.99 % ± 0.05 % μM, 5.92 % ± 2.04 % μM, and 2.53 % ± 0.73 % μM, respectively, under white light irradiation. Mechanistic experiments revealed that derivatives induced cell apoptosis via the mitochondrial apoptosis pathway during both CT and CPCT. Remarkably, BA-1 and BA-3 in CPCT inhibited cancer cell proliferation in an in vivo melanoma mouse xenograft model. These results collectively encourage further research of PT-AIEgens as potential anticancer agents.

A dual donor-acceptor fluorescent probe with viscosity response and lipid droplets targeting to initiate oxidative stress for tumor elimination

A dual donor-acceptor photosensitizer TCN-2 prepared based on single donor-acceptor could fulfil lipid droplets targeting to trigger apoptosis and tumor growth arrest. Meanwhile, all of experiments both in phosphate buffer solution and intracellular surroundings have demonstrated that TCN-2 catalyzed the production of type I as well as type II reactive oxygen species, forming a hybrid reactive oxygen species pattern, indicating that TCN-2 could be applied to initiate a series of biological responses triggered by oxidative stress within most high-viscosity solid tumors. In addition, TCN-2 also has the capability of fluorescence imaging, which could perfectly combine therapeutic imaging to achieve therapeutic effects while identifying cancerous lesions. Due to the structural design of double electron-absorbing groups, TCN-2 retained excellent lipophilicity while enhancing solubility in the biological environment. Terrific biocompatibility, minimal phototoxic damage to normal cells and tissues, and specific driving to prescriptive organelles to maximize therapeutic effects were used to enhance the therapeutic effect of photodynamic therapy to cease disease progression.

Reviewing the evolutive ACQ-to-AIE transformation of photosensitizers for phototheranostics

Photodynamic therapy (PDT) represents an emerging noninvasive treatment technique for cancers and various nonmalignant diseases, including infections. During the process of PDT, the physical and chemical properties of photosensitizers (PSs) critically determine the effectiveness of PDT. Traditional PSs have made great progress in clinical applications. One of the challenges is that traditional PSs suffer from aggregation-caused quenching (ACQ) due to their discotic structures. Recently, aggregation-induced emission PSs (AIE-PSs) with a twisted propeller-shaped conformation have been widely concerned because of high reactive oxygen species (ROS) generation efficiency, strong fluorescence efficiency, and resistance to photobleaching. However, AIE-PSs also have some disadvantages, such as short absorption wavelengths and insufficient molar absorption coefficient. When the advantages and disadvantages of AIE-PSs and ACQ-PSs are complementary, combining ACQ-PSs and AIE-PSs is a "win-to-win" strategy. As far as we know, the conversion of traditional representative ACQ-PSs to AIE-PSs for phototheranostics has not been reviewed. In the review, we summarize the recent progress on the ACQ-to-AIE transformation of PSs and the strategies to achieve desirable theranostic applications. The review would be helpful to design more efficient ACQ-AIE-PSs in the future and to accelerate the development and clinical application of PDT.

Bioorthogonal Guided Activation of cGAS-STING by AIE Photosensitizer Nanoparticles for Targeted Tumor Therapy and Imaging

Photodynamic therapy (PDT) and photothermal therapy (PTT) leverage reactive oxygen species (ROS) and control local hyperthermia by photosensitizer to perturb intracellular redox equilibrium, inducing DNA damage in both mitochondria and nucleus, activating the cGAS-STING pathway, ultimately eliciting antitumor immune responses. However, current photosensitizers are encumbered by limitations such as suboptimal tumor targeting, aggregation-caused quenching (ACQ), and restricted excitation and emission wavelengths. Here, this work designs novel nanoparticles based on aggregation-induced emission (AIE) photosensitizer (BODTPE) for targeted tumor therapy and near-infrared II fluorescence imaging (NIR-II FLI) with enhanced PDT/PTT effects. BODTPE is employed as a monomer, dibenzocyclooctyne (DBCO)-PEG2k -amine serving as an end-capping polymer, to synthesize a BODTPE-containing polymer (DBD). Further, through self-assembly, DBD and mPEG-DSPE2k combined to form nanoparticles (NP-DBD). Notably, the DBCO on the surface of NP-DBD can react with azide groups on cancer cells pretreated with Ac4 ManNAz through a copper-free click reaction. This innovative formulation led to targeted accumulation of NP-DBD within tumor sites, a phenomenon convincingly demonstrated in murine tumor models subjected to N-azidoacetylmannosamine-tetraacylated (Ac4 ManNAz) pretreatment. Significantly, NP-DBD exhibits a multifaceted effect encompassing PDT/PTT/NIR-II FLI upon 808 nm laser irradiation, thereby better activating the cGAS-STING pathway, culminating in a compelling tumor inhibition effect augmented by robust immune modulation.

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.

Small molecules and conjugates as theranostic agents

Theranostics, the integration of therapy and diagnostics into a single entity for the purpose of monitoring disease progression and treatment response. Diagnostics involves identifying specific characteristics of a disease, while therapeutics refers to the treatment of the disease based on this identification. Advancements in medicinal chemistry and technology have led to the development of drug modalities that provide targeted therapeutic effects while also providing real-time updates on disease progression and treatment. The inclusion of imaging in therapy has significantly improved the prognosis of devastating diseases such as cancer and neurodegeneration. Currently, theranostic treatment approaches are based on nuclear medicine, while nanomedicine and a wide diversity of macromolecular systems such as gels, polymers, aptamers, and dendrimer-based agents are being developed for the purpose. Theranostic agents have significant roles to play in both early-stage drug development and clinical-stage therapeutic-containing drug candidates. This review will briefly outline the pros and cons of existing and evolving theranostic approaches before comprehensively discussing the role of small molecules and their conjugates.

A Mitochondria-Targeted NIR-II AIEgen Induced Pyroptosis for Enhanced Tumor Immunotherapy

Cancer immunotherapy is a favorable strategy for facilitating anti-tumor immunity, but it shows limited benefits in clinical practice owing to the immunosuppressive tumor microenvironment. Pyroptosis shows great immunostimulatory effect on tumor, whereas the lack of pyroptotic inducer with imaging property has restricted its progress in tumor theranostics. Herein, a mitochondria-targeted aggregation-induced emission (AIE) luminogen (TPA-2TIN) with NIR-II emission is designed for highly efficient induction of tumor cell pyroptosis. The fabricated TPA-2TIN nanoparticles can be efficiently taken up by tumor cells and selectively accumulated in tumor for a long term observed by NIR-II fluorescence imaging. More importantly, the TPA-2TIN nanoparticles can effectively stimulate immune responses both in vitro and in vivo mediated by the mitochondrial dysfunctions and the subsequent activation of the pyroptotic pathway. Ultimately, the reversal of the immunosuppressive tumor microenvironment significantly enhances the immune checkpoint therapy. This study paves a new avenue for adjuvant immunotherapy of cancer.

Aza-dicyclopenta[a,g]naphthalenes: controllable seesaw-like emissive behavior and narrowband AIEgens

Molecular motions significantly influence the emissive behavior and properties of organic fluorescent molecules. However, achieving controllable emission remains a major challenge for fluorophores. In the case of aggregation-induced emission luminogens (AIEgens), the desired properties of aggregated emission and narrowband spectrum demand molecular motion patterns that inherently oppose each other. A nitrogen-containing dicyclopenta[a,g]naphthalene scaffold was discovered as a controllable luminogenic structure through a highly efficient one-step intermolecular cascade reaction. By carefully balancing molecular motions and introducing additional nitrogen atoms into the skeleton, pyrrole-conjugated dicyclopenta[a,g]naphthalenes with aggregation-caused quenching (ACQ) could be transformed into dual-state emission luminogens (DSEgens). This transformation was achieved by incorporating an additional weak H-bond "lock." Furthermore, the DSEgens could be converted into AIEgens with an exciting narrow full-width-at-half-maximum (FWHM, <50 nm) by methylation. This unprecedented discovery is attributed to the contribution of the weak H-bond "lock," which overcomes the limitations of broad band emission in AIEgens caused by restrictions of intramolecular motion. Specific organelle probes were developed by replacing the methyl group of the onium product with different positioning groups. This study emphasizes the delicate balance of molecular motions in controlling luminescence and demonstrates a successful approach to designing organic luminogens with controllable emission and narrowband AIEgens.

The Role of Structural Hydrophobicity on Cationic Amphiphilic Aggregation-Induced Emission Photosensitizer-Bacterial Interaction and Photodynamic Efficiency

The aggregation-induced emission photosensitizer (AIE PS) has stood out as an alternative and competent candidate in bacterial theranostics, particularly with the use of cationic AIE PS in bacterial discrimination and elimination. Most reported work emphasizes the role of electrostatic interaction between cationic AIE PS and negatively charged bacterial surfaces, enabling broad applications from bacterial discrimination to bacterial killing. However, the underlying targeting mechanism and the design rationale of the cationic AIE PS for effective bacterial labeling remain poorly investigated. In this Article, we designed and synthesized a series of cationic amphiphilic AIE PSs with different calculated log P values. Then, we systemically studied the relationship between the hydrophobicity variation of AIE PS and bacterial targeting outcomes, the dose of AIE PS needed to label various species of bacteria, and their photodynamic antibacterial efficiency. The findings in this work provide a better understanding of the unclear AIE PS-bacterial interaction mechanism and some insights into the structural design strategies of cationic amphiphilic AIE PS for better development in bacterial theranostics.

The synthesis of novel water-soluble zinc (II) phthalocyanine based photosensitizers and exploring of photodynamic therapy activities on the PC3 cancer cell line

In this study, Schiff base substituted phthalocyanine complexes (Zn1c, Zn2c) and their quaternized derivatives (Q-Zn1c, Q-Zn2c) were synthesized for the first time. Their structures have been characterized by FT-IR, 1H-NMR, UV-Vis, mass spectrometry and elemental analysis as well as. The photophysicochemical properties (fluorescence, singlet oxygen and photodegradation quantum yield) of these novel complexes were investigated in dimethylsulfoxide (DMSO) for both non-ionic and quaternized cationic phthalocyanine complexes and in aqueous solution for quaternized cationic phthalocyanine complexes. Water soluble cationic phthalocyanine compounds gave good singlet oxygen quantum yield (0.65 for Q-Zn1c, 0.66 for Q-Zn2c in DMSO; 0.65 for Q-Zn2c in aqueous solution). The binding of Q-Zn1c and Q-Zn2c to BSA/DNA was studied by using UV-Vis and fluorescence spectroscopy and these. Studies indicate that the mechanism of BSA quenching by quaternized zinc(II) phthalocyanines was static quenching. Quaternized zinc(II) phthalocyanines interacted with ct-DNA by intercalation. Quaternized zinc(II) phthalocyanines caused a decrease in cell viability and triggered apoptotic cell death after PDT was applied at a concentration that did not have a toxic effect on their own. Q-Zn1c and Q-Zn2c mediated PDT reduced the activity of SOD, CAT, GSH while increased MDA level in the prostate cancer cells. Furthermore, expression of apoptotic proteins after PDT was examined. The results revealed that the synthesized water soluble quaternized zinc(II) phthalocyanine complexes (Q-Zn1c and Q-Zn2c) are promising potential photosensitizers for PDT.

Type I Photosensitization with Strong Hydroxyl Radical Generation in NIR Dye Boosted by Vigorous Intramolecular Motions for Synergistic Therapy

Development of type I photosensitizers (PSs) with strong hydroxyl radical (· OH) formation is particularly important in the anaerobic tumor treatment. On the other hand, it is challenging to obtain an efficient solid-state intramolecular motion to promote the development of molecular machine and molecular motor. However, the relationship between them is never revealed. In this work, a pyrazine-based near-infrared type I PS with remarkable donor-acceptor effect is developed. Notably, the intramolecular motions are almost maximized by the combination of intramolecular and intermolecular engineering to simultaneously introduce the unlimited bond stretching vibration and boost the group rotation. The photothermal conversion caused by the intramolecular motions is realized with efficiency as high as 86.8%. The D-A conformation of PS can also induce a very small singlet-triplet splitting of 0.07 eV, which is crucial to promote the intersystem crossing for the triplet sensitization. Interestingly, its photosensitization is closely related to the intramolecular motions, and a vigorous motion may give rise to a strong · OH generation. In view of its excellent photosensitization and photothermal behavior, the biocompatible PS exhibits a superior imaging-guided cancer synergistic therapy. This work stimulates the development of advanced PS for the biomedical application and solid-state intramolecular motions.

A lysosomes and mitochondria dual-targeting AIE-active NIR photosensitizer: Constructing amphiphilic structure for enhanced antitumor activity and two-photon imaging

Development of lysosomes and mitochondria dual-targeting photosensitizer with the virtues of near-infrared (NIR) emission, highly efficient reactive oxygen generation, good phototoxicity and biocompatibility is highly desirable in the field of imaging-guided photodynamic therapy (PDT) for cancer. Herein, a new positively charged amphiphilic organic compound (2-(2-(5-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)vinyl)-3-methylbenzo[d]thiazol-3-ium iodide) (ADB) based on a D-A-π-A structure is designed and comprehensively investigated. ADB demonstrates special lysosomes and mitochondria dual-organelles targeting, bright NIR aggregation-induced emission (AIE) at 736 ​nm, high singlet oxygen (¹O₂) quantum yield (0.442), as well as good biocompatibility and photostability. In addition, ADB can act as a two-photon imaging agent for the elaborate observation of living cells and blood vessel networks of tissues. Upon light irradiation, obvious decrease of mitochondrial membrane potential (MMP), abnormal mitochondria morphology, as well as phagocytotic vesicles and lysosomal disruption in cells are observed, which further induce cell apoptosis and resulting in enhanced antitumor activity for cancer treatment. In vivo experiments reveal that ADB can inhibit tumor growth efficiently upon light exposure. These findings demonstrate that this dual-organelles targeted ADB has great potential for clinical imaging-guided photodynamic therapy, and this work provides a new avenue for the development of multi-organelles targeted photosensitizers for highly efficient cancer treatment.

Targeting Proteins in Nucleus through Dual-Regulatory Pathways Acting in Cytoplasm

Nuclear proteins have been regarded as attractive targets for exploiting therapeutic agents. However, those agents cannot efficiently pass through nuclear pores and it is also difficult to overcome the crowded nuclear environment to react with proteins. Herein, we propose a novel strategy acting in the cytoplasm to regulate nuclear proteins based on their signaling pathways, instead of directly entering into nuclei. A multifunctional complex PKK-TTP/hs carries human telomerase reverse transcriptase (hTERT) small interfering RNA (defined as hs) for gene silencing in the cytoplasm, which reduced the import of nuclear protein. At the same time, it could generate reactive oxygen species (ROS) under light irradiation, which raised the export of nuclear proteins by promoting proteins translocation. Through this dual-regulatory pathway, we successfully reduced nuclear protein (hTERT proteins) in vivo (42.3%). This work bypasses the challenge of directly entering into the nucleus and provides an effective strategy for regulating nuclear proteins.

Biomimetic Approach toward Kinetically Stable AIE-Gens under Physiological Conditions

Many AIE-gens suffer from excessive hydrophobicity, and their kinetic stability in aqueous condition is not warranted. Here, we introduce phosphorylcholine, a zwitterionic group ubiquitously found in biological membranes, onto the tetraphenylethene core structure to yield AIE nanoparticles stable in both PBS buffer and cell culture. We also find that the AIE efficiency is critically reliant on the delicate balance between the hydrophilic phosphorylcholine and hydrophobic moieties.

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.

Aggregation-induced emission biomaterials for anti-pathogen medical applications: detecting, imaging and killing

Microbial pathogens, including bacteria, fungi and viruses, greatly threaten the global public health. For pathogen infections, early diagnosis and precise treatment are essential to cut the mortality rate. The emergence of aggregation-induced emission (AIE) biomaterials provides an effective and promising tool for the theranostics of pathogen infections. In this review, the recent advances about AIE biomaterials for anti-pathogen theranostics are summarized. With the excellent sensitivity and photostability, AIE biomaterials have been widely applied for precise diagnosis of pathogens. Besides, different types of anti-pathogen methods based on AIE biomaterials will be presented in detail, including chemotherapy and phototherapy. Finally, the existing deficiencies and future development of AIE biomaterials for anti-pathogen applications will be discussed.

Microneedle Device Delivering Aggregation-Induced Emission Photosensitizers for Enhanced Metronomic Photodynamic Therapy of Cancer

Metronomic photodynamic therapy (mPDT), which induces cancer cell death by prolonged intermittent continuous irradiation at lower light power, has profoundly promising applications. However, the photobleaching sensitivity of the photosensitizer (PS) and the difficulty of delivery pose barriers to the clinical application of mPDT. Here, we constructed a microneedle-based device (Microneedles@AIE PSs) that combined with aggregation-induced emission (AIE) PSs to achieve enhanced mPDT for cancer. Due to the strong anti-photobleaching property of the AIE PS, it can maintain superior photosensitivity even after long-time light exposure. The delivery of the AIE PS to the tumor through a microneedle device allows for greater uniformity and depth. This Microneedles@AIE PSs-based mPDT (M-mPDT) offers better treatment outcomes and easier access, and combining M-mPDT with surgery or immunotherapy can also significantly improve the effectiveness of these clinical therapies. In conclusion, M-mPDT offers a promising strategy for the clinical application of PDT due to its better efficacy and convenience.

Photosensitizers with aggregation-induced far-red/near-infrared emission for versatile visualization and broad-spectrum photodynamic killing of pathogenic microbes

The exploration of photosensitizers with aggregation-induced emission (AIE PSs) for efficient visualization and broad-spectrum photodynamic killing of pathogenic microbes is a significant task. Herein, two far-red/near-infrared AIE-active PSs (TBTPy and TBTCy) were attained to show efficient Type I and Type II ROS generation, benefiting from the efficient ISC processes. The attained AIE PSs, especially TBTPy with bright emission, showed advantages in discriminating G⁺ bacteria over G^- bacteria, and distinguishing dead E. coli from lived one. Both TBTPy and TBTCy have the capacity of broad-spectrum photodynamic killing of pathogenic microbes in vitro with considerable safety for mammalian cells. Antimicrobial mechanism is found to be changing osmotic pressure of cytoplasm in E. coli, causing cell deformation and destruction of S. aureus and C. albicans. In vivo anti-infection experiment demonstrated AIE PSs can accelerate the healing process of the burned wounds on rats infected by methicillin-resistant S. aureus (MRSA) or E. coli, indicating their potential to treat tertiary burns in clinical application. Therefore, the attained AIE PSs hold great promise as antimicrobial candidates in infective therapeutic application.

Platelet membrane camouflaged AIEgen-mediated photodynamic therapy improves the effectiveness of anti-PD-L1 immunotherapy in large-burden tumors

Although immunotherapy has achieved recent clinical success in antitumor therapy, it is less effective for solid tumors with large burdens. To overcome this challenge, herein, we report a new strategy based on platelet membrane-camouflaged aggregation-induced emission (AIE) luminogen (Plt-M@P) combined with the anti-programmed death ligand 1 (anti-PD-L1) for tumoral photodynamic-immunotherapy. Plt-M@P is prepared by using poly lactic-co-glycolic acid (PLGA)/PF3-PPh3 complex as a nanocore, and then by co-extrusion with platelet membranes. PF3-PPh3 is an AIE-active conjugated polyelectrolyte with photosensitizing capability for photodynamic therapy (PDT). Plt-M@P exhibits superior tumor targeting capacity in vivo. When applied in small tumor-bearing (~40 mm3) mice, Plt-M@P-mediated PDT significantly inhibits tumor growth. In tumor models with large burdens (~200 mm3), using Plt-M@P-mediated PDT or anti-PD-L1 alone is less effective, but the combination of both is effective in inhibiting tumor growth. Importantly, this combination therapy has good biocompatibility, as demonstrated by the absence of damage to the major organs, especially the reproductive system. In conclusion, we show that Plt-M@P-mediated PDT can improve anti-PD-L1 immunotherapy by enhancing antitumor effects, providing a promising strategy for the treatment of tumors with large burdens.

A chlorin e6 derivative-mediated photodynamic therapy inhibits cutaneous squamous cell carcinoma cell proliferation via Akt/mTOR signaling pathway

BACKGROUND AND OBJECTIVES

Although most cutaneous squamous cell carcinoma (cSCC) cases are generally nonlethal and manageable with surgical excision, there ares till significant hazards for patients who are ineligible for surgical resection. We sought to find a suitable and effective treatment for cSCC.

METHODS

We modified chlorin e6 by adding a hydrogen chain with a six-carbon ring to the benzene ring and named this new photosensitizer as STBF. We first investigated the fluorescence characteristics, cellular uptake of STBF and subcellular localization. Next, cell viability was detected by CCK-8 assay and the TUNEL staining was performed. Akt/mTOR-related proteins were examined by western blot.

RESULTS

STBF-photodynamic therapy (PDT) inhibits cSCC cells viability in a light dose dependent manner. The antitumor mechanism of STBF-PDT might be due to the suppression of the Akt/mTOR signaling pathway. Further animal investigation determined that STBF-PDT led to a marked reduction in tumor growth.

CONCLUSIONS

Our results suggest that STBF-PDT exerts significant therapeutic effects in cSCC. Thus, STBF-PDT is expected to be a promising method for the treatment of cSCC and the photosensitizer STBF may be destined for a wider range of applications in photodynamic therapy.

Enabling Photo-Crosslinking and Photo-Sensitizing Properties for Synthetic Fluorescent Protein Chromophores

Synthetic fluorescent protein chromophores have been reported for their singlet state fluorescence properties and applications in bioimaging, but rarely for the triplet state chemistries. Herein, we enabled their photo-sensitizing and photo-crosslinking properties through rational modulations. Extension of molecular conjugation and introduction of heavy atoms promoted the generation of reactive oxygen species. Unlike other photosensitizers, these chromophores selectively photo-crosslinked aggregated proteins and uncovered the interactome profiles. We also exemplified their general applications in chromophore-assisted light inactivation, photodynamic therapy and photo induced polymerization. Theoretical calculation, pathway analysis and transient absorption spectroscopy provided mechanistic insights for this triplet state chemistry. Overall, this work expands the function and application of synthetic fluorescent protein chromophores by enabling their triplet excited state properties.

Efficient antibacterial AIEgens induced ROS for selective photodynamic treatment of bacterial keratitis

Bacterial keratitis (BK) is an acute infection of the cornea, accompanied by uneven epithelium boundaries with stromal ulceration, potentially resulting in vision loss. Topical antibiotic is the regular treatment for BK. However, the incidence rate of multidrug-resistant bacteria limits the application of traditional antibiotics. Therefore, a cationic aggregation-induced emission luminogens (AIEgens) named TTVP is utilized for the treatment of BK. TTVP showed no obvious cytotoxicity in maintaining the normal cell morphology and viability under a limited concentration, and revealed the ability to selectively combine with bacteria in normal ocular environment. After light irradiation, TTVP produced reactive oxygen species (ROS), thus exerting efficient antibacterial ability in vitro. What's more, in rat models of Staphylococcus aureus (S. aureus) infection, the therapeutic intervention of TTVP lessens the degree of corneal opacity and inflammatory infiltration, limiting the spread of inflammation. Besides, TTVP manifested superior antibacterial efficacy than levofloxacin in acute BK, endowing its better vision salvage ability than conventional method. This research demonstrates the efficacy and advantages of TTVP as a photodynamic drug in the treatment of BK and represents its promise in clinical application of ocular infections.

Short-Wavelength Aggregation-Induced Emission Photosensitizers for Solid Tumor Therapy: Enhanced with White-Light Fiber Optic

Background

White-light photodynamic therapy (wPDT) has been used in the treatment of cancer due to its convenience, effectiveness and less painful. However, the limited penetration of white-light into the tissues leads to a reduced effectiveness of solid tumor treatment.

Methods

Two short-wavelength aggregation-induced emission (AIE) nanoparticles were prepared, PyTPA@PEG and TB@PEG, which have excitation wavelengths of 440 nm and 524 nm, respectively. They were characterized by UV, fluorescence, particle size and TEM. The ability of nanoparticles to produce reactive oxygen species (ROS) and kill cancer cells under different conditions was investigated in vitro, including white-light, after white-light penetrating the skin, laser. A white-light fiber for intra-tumor irradiation was customized. Finally, induced tumor elimination with fiber-mediated wPDT was confirmed in vivo.

Results

In vitro, both PyTPA@PEG and TB@PEG are more efficient in the production ROS when exposed to white-light compared to laser. However, wPDT also has a fatal flaw in that its level of ROS production after penetrating the skin is reduced to 20-40% of the original level. To this end, we have customized a white-light fiber for intra-tumor irradiation. In vivo, the fiber-mediated wPDT significantly induces tumor elimination with maximized therapeutic outcomes by irradiating the interior of the tumor. In addition, wPDT also has the advantage that its light source can be adapted to a wide range of photosensitizers (wavelength range 400-700 nm), whereas a laser of single wavelength can only target a specific photosensitizer.

Conclusion

This method of using optical fiber to increase the tissue penetration of white light can greatly improve the therapeutic effect of AIE photosensitizers, which is needed for the treatment of large/deep tumors and holds great promise in cancer treatment.

Erythrocyte Membrane-Camouflaged Aggregation-Induced Emission Nanoparticles for Fetal Intestinal Maturation Assessment

Assessment of fetal maturity is essential for timely termination of pregnancy, especially in pregnant women with pregnancy complications. However, there is a lack of methods to assess the maturity of fetal intestinal function. Here, we constructed erythrocyte membrane-camouflaged aggregation-induced emission (AIE) nanoparticles. Nanocore is formed using a hollow mesoporous silicon nanobox (HMSN) of different particle sizes loaded with AIE luminogens -PyTPA (P), which are then co-extruded with erythrocyte membranes (M) to construct M@HMSN@P. The 100 nm M@HMSN@P has a more effective cellular uptake efficiency in vitro and in vivo. Swallowing and intestinal function in fetal mice mature with the increase in gestational age. After intrauterine injection of M@HMSN@P, they were swallowed and absorbed by fetal mice, and their swallowed and absorbed amount was positively correlated with the gestational age with a correlation coefficient of 0.9625. Using the M@HMSN@P (fluorescence intensity) in fetal mice, the gestational age can be imputed, and the difference between this imputed gestational age and the actual gestational age is less than 1 day. Importantly, M@HMSN@P has no side effect on the health status of pregnant and fetal mice, showing good biocompatibility. In conclusion, we constructed M@HMSN@P nanoparticles with different particle sizes and confirmed that the smaller size M@HMSN@P has more efficient absorption efficiency and it can assess fetal intestinal maturity by the intensity of the fluorescence signal.

Combining PD-L1 blockade with immunogenic cell death induced by AIE photosensitizer to improve antitumor immunity

Immunogenic cell death (ICD) is considered an effective death mode to trigger immune response. However, the currently available efficient ICD inducers are quite limited. Endoplasmic reticulum (ER) stress is known as the precursor of ICD, which can be directly triggered by reactive oxygen species in situ. Herein, a novel photosensitizer (α-Th-TPA-PIO) based on phosphindole oxide, featuring aggregation-induced emission (AIE) is designed and prepared, which possesses good ability of hydroxyl radicals (HO^•) generation. Besides, α-Th-TPA-PIO can selectively accumulate in ER and trigger ER stress under white light irradiation, further leading to effective ICD. Combining with anti-programmed death-ligand 1 (anti-PD-L1), the synergistic effect of photodynamic therapy (PDT) and immune checkpoint blockade can achieve a significantly enhanced inhibition effect on the growth of tumors and simultaneously provoke a systemic antitumor immune response. Notably, by adopting this therapeutic strategy to bilateral and metastatic tumor models, the growth of both primary and distant subcutaneous tumors can be successfully suppressed, and metastatic tumor can also be inhibited to some degree. Taken together, this work not only provides a novel ICD photoinducer based on PDT, but also brings about a useful immunomodulatory strategy to realize superior antitumor effect.

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.

Stimuli-Responsive Electrospun Fluorescent Fibers Augmented with Aggregation-Induced Emission (AIE) for Smart Applications

This review addresses the latest advancements in the integration of aggregation-induced emission (AIE) materials with polymer electrospinning, to accomplish fine-scale electrospun fibers with tunable photophysical and photochemical properties. Micro- and nanoscale fibers augmented with AIE dyes (termed AIEgens) are bespoke composite systems that can overcome the limitation posed by aggregation-caused quenching, a critical deficiency of conventional luminescent materials. This review comprises three parts. First, the reader is exposed to the basic concepts of AIE and the fundamental mechanisms underpinning the restriction of intermolecular motions. This is followed by an introduction to electrospinning techniques pertinent to AIE-based fibers, and the core parameters for controlling fiber architecture and resultant properties. Second, exemplars are drawn from latest research to demonstrate how electrospun nanofibers and porous films incorporating modified AIEgens (especially tetraphenylethylene and triphenylamine derivatives) can yield enhanced photostability, photothermal properties, photoefficiency (quantum yield), and improved device sensitivity. Advanced applications are drawn from several promising sectors, encompassing optoelectronics, drug delivery and biology, chemosensors and mechanochromic sensors, and innovative photothermal devices, among others. Finally, the outstanding challenges together with potential opportunities in the nascent field of electrospun AIE-active fibers are presented, for stimulating frontier research and explorations in this exciting field.

AIE-Active Antibiotic Photosensitizer with Enhanced Fluorescence in Bacteria Infected Cells and Better Therapy Effect toward Drug-Resistant Bacteria

It is well-known that bacterial infections will induce a variety of diseases in the clinic. In particular, the emergence of drug-resistant bacteria has increased the threat to human health. The development of multiple modes of therapy will effectively fight against drug-resistant bacterial infections. In this work, we covalently attached an AIE photosensitizer to the antibiotic of moxifloxacin hydrochloride (MXF-HCl) and synthesized an antibiotic derivative, MXF-R, with pharmacological activity and photodynamic activation. In infected cells, MXF-R showed enhanced fluorescence after it specifically binds to bacteria; thus, in situ visualization of the bacteria was realized. Notably, through chemo- and photodynamic therapy, MXF-R exhibited better antibacterial activity than its parent antibiotic in rapid sterilization, and it achieved effective killing for moxifloxacin resistant bacteria. In addition, MXF-R shows a broad-spectrum antibacterial effect and could be used in the recovery therapy of infected wounds in mice, demonstrative of a significant therapeutic effect and good biological safety. Thus, as a promising multifunctional antibacterial agent, MXF-R will have tremendous potential in in situ visualization study and killing of drug-resistant bacteria. This work provides an innovative strategy for solving critical disease through the combination of materials and biomedical sciences.

Type I Photosensitizers Based on Aggregation-Induced Emission: A Rising Star in Photodynamic Therapy

Photodynamic therapy (PDT), emerging as a minimally invasive therapeutic modality with precise controllability and high spatiotemporal accuracy, has earned significant advancements in the field of cancer and other non-cancerous diseases treatment. Thereinto, type I PDT represents an irreplaceable and meritorious part in contributing to these delightful achievements since its distinctive hypoxia tolerance can perfectly compensate for the high oxygen-dependent type II PDT, particularly in hypoxic tissues. Regarding the diverse type I photosensitizers (PSs) that light up type I PDT, aggregation-induced emission (AIE)-active type I PSs are currently arousing great research interest owing to their distinguished AIE and aggregation-induced generation of reactive oxygen species (AIE-ROS) features. In this review, we offer a comprehensive overview of the cutting-edge advances of novel AIE-active type I PSs by delineating the photophysical and photochemical mechanisms of the type I pathway, summarizing the current molecular design strategies for promoting the type I process, and showcasing current bioapplications, in succession. Notably, the strategies to construct highly efficient type I AIE PSs were elucidated in detail from the two aspects of introducing high electron affinity groups, and enhancing intramolecular charge transfer (ICT) intensity. Lastly, we present a brief conclusion, and a discussion on the current limitations and proposed opportunities.

Vision Defense: Efficient Antibacterial AIEgens Induced Early Immune Response for Bacterial Endophthalmitis

Bacterial endophthalmitis (BE) is an acute eye infection and potentially irreversible blinding ocular disease. The empirical intravitreous injection of antibiotic is the primary treatment once diagnosed as BE. However, the overuse of antibiotic contributes to the drug resistance of pathogens and the retinal toxicity of antibiotic limits its application in clinic. Herein, a cationic aggregation-induced emission luminogens named with triphenylamine thiophen pyridinium (TTPy) is reported for photodynamic treatment of BE. TTPy can selectively discriminate and kill bacteria efficiently over normal ocular cells. More importantly, TTPy shows excellent antibacterial ability in BE rat models infected by Staphylococcus aureus. Meanwhile, the bacterial killing behavior triggered by TTPy induces innate immune response at an early stage of infection, limiting subsequent robust inflammation and protecting retina from bacterial toxins and inflammation-induced bystander damage. In addition, TTPy performs better antibacterial ability than commercially used Rose Bengal, suggesting its excellent capability of vision salvage in acute BE. This study exhibits an efficient photodynamic antibacterial treatment to BE, which induces an early intraocular immune response and saves useful vision, endowing TTPy a promising potential for clinical application of ocular infections.

Antibacterial Theranostic Agents with Negligible Living Cell Invasiveness: AIE-Active Cationic Amphiphiles Regulated by Alkyl Chain Engineering

To address the threat of bacterial infection in the following post-antibiotic era, developing effective antibacterial approaches is of utmost urgency. Theranostic medicine integrating diagnosis and therapy is a promising protocol to fight against pathogenic bacteria. But numerous reported antibacterial theranostic materials are disclosed to be trapped in the excessive invasiveness to living mammal cells, leading to false positives and possible biosafety risks. Herein, a series of cationic pyridinium-substituted phosphindole oxide derivatives featuring aggregation-induced emission are designed, and alkyl chain engineering is conducted to finely tune their hydrophobicity and investigate their bioaffinity preference for living mammal cells and pathogenic bacteria. Most importantly, an efficient theranostic agent (PyBu-PIO) is acquired that is free from living cell invasiveness with negligible cytotoxicity and yet holds a good affinity for Gram-positive bacteria, including drug-resistant strains, with a superior inactivating effect. Externally applying PyBu-PIO onto Gram-positive bacteria-infected skin wounds can achieve creditable imaging effects and successfully accelerate the healing processes with reliable biosafety. This work proposes living cell invasiveness as a criterion for antibacterial theranostic materials and provides important enlightenment for the design of antibacterial theranostic materials.