Activated aggregation‐induced emission therapeutics agents for triggering regulated cell death

The induction of regulated cell death (RCD) through photo/ultrasound sensitization therapeutic agents has gained significant attention as a vital approach to combat drug resistance in tumors. Aggregation‐induced emission (AIE) therapeutic agents generate reactive oxygen species through photo/ultrasound activation, which can synergize with RCD inducers or directly induce RCD, ultimately resulting in the death of tumor cells. The presented comprehensive review delves into recent advancements in AIE therapeutic agents designed to trigger RCD or synergize with RCD inducers, encompassing apoptosis, necroptosis, pyroptosis, immunogenic cell death, autophagy, ferroptosis, and cuproptosis. Additionally, the intricate regulatory mechanisms through which activatory‐AIE therapeutics influence distinct RCD pathways are examined. A forward‐looking perspective on future developments and pertinent challenges within this exciting realm is presented, anticipating the continued evolution of activatable AIE therapeutics as a transformative approach to enhance tumor therapy.

triggers the transition of electrons from the ground state to the excited state.As the electrons return to the ground state from this excited state, they release energy.[7][8] These photoluminescence phenomena are primarily applied to tumor labeling and detection. [9,10]In contrast, the phototherapy process mainly involves the release of excited-state energy through nonradiative relaxation processes.[16][17] However, the effectiveness of phototherapy in the treatment of deep-seated tumors is limited due to the constrained penetration of excitation light into deep tissues.[20][21] The fundamental concept behind SDT closely mirrors that of PDT.After the absorption of energy from the ultrasound by the sonosensitizer (SS), an electron and energy transfer process occurs, similar to the photodynamic process, ultimately leading to the generation of reactive oxygen species (ROS) and the subsequent elimination of deep-seated tumor cells within the tissue. [22,23]onetheless, the efficacy of phototherapy or SDT faces a significant hurdle known as the aggregation-caused quenching (ACQ) phenomenon. [24,25]This challenge arises from the extensive planar conjugate structure and pronounced hydrophobic properties of PS/SSs.Fortunately, in 2001, Ben Zhong Tang made a significant breakthrough, introducing the concept of aggregation-induced emission (AIE) while investigating unique fluorescence phenomena. [26][29][30] This pivotal discovery allowed for the possibility of phototherapy or SDT, offering new avenues for improved treatment.
The resistance of tumors to chemotherapeutic drugs constitutes a significant issue in the area of cancer treatment. [31,32]ithin this context, it is plausible that the presence of deficiencies within the tumor cell's pathway for drug-induced apoptosis serves as an important factor. [33,34]Notably, apoptosis initiated by ROS may circumvent the pathway for drug-induced apoptosis, thereby eluding the mechanisms of drug resistance exhibited by tumor cells. [35,36]Concurrently, the evolving comprehension of cell death processes has highlighted an alternative strategy for instigating tumor cell demise through non-apoptotic RCD pathways. [37,38]These include autophagy, [39,40] pyroptosis, [41,42] necroptosis, [43][44][45] immunogenic cell death (ICD), [46][47][48] ferroptosis, [49,50] and the recently unearthed cuproptosis. [51,52][55][56][57][58][59][60][61][62][63][64][65][66][67] This multifaceted approach serves to circumvent the conventional drug resistance mechanisms harbored by tumors, thereby substantially enhancing the efficacy of tumor treatment. [68,69]romisingly, photosensitizers or sonosensitizers designed in accordance with the attributes of AIE have emerged as robust contenders for the role of next-generation therapeutic agents that synergize with RCD inducers or directly induce RCD.[72] Therefore, this article comprehensively reviews the latest advancements in the fields of light and sound-activated AIE-based therapeutic agents as inducers of RCD or synergized with RCD inducers within the past 2 years.In addition to shedding light on the current state of research, this discourse also delineates potential developments along with the challenges that this domain may face in the future.

TRIGGERING APOPTOSIS WITH AIE THERAPEUTIC AGENTS
In 1972, Kerr, Wyllie, and Currie coined the term "apoptosis" within a pioneering paper, which describes a distinct cellular demise. [73]Apoptosis is a process wherein a cell relinquishes its growth and division, embracing an intricate sequence that ultimately orchestrates the cell's demise, averting any leakage of its contents into the surrounding milieu.
Governing this process depends on three signaling pathways.First, caspase-8 becomes activated by external death ligands, such as inflammatory factors.Subsequently, caspase-8 triggers the activation of caspase-3, culminating in apoptosis.The second pathway involves intracellular mitochondrial stress, which initiates the activation of caspase-9.Caspase-9, in turn, triggers the activation of caspase-3, ultimately leading to apoptosis.The third pathway centers on intracellular endoplasmic reticulum (ER) stress, which prompts the activation of caspase-12.Caspase-12 then initiates the activation of caspase-3, eventually resulting in apoptosis (Figure 2A).

2.1
Triggering apoptosis with AIE-based molecular probes

Triggering apoptosis through the mitochondrial stress
The apoptosis induced by AIEgens is usually through the activation of ROS produced by AIEgens, which leads to mitochondrial or endoplasmic reticulum oxidative stress and eventually induces caspase-3 activation through different signaling pathways.This eventually leads to cell apoptosis.For example, in 2023, Zhu group presented an electron-rich anion-π + AIEgen named Pys-QM-TT, capable of robustly generating both type I and type II ROS activates via the apoptosis pathway through mitochondrial oxidative stress (Figure 2B). [74]Pys-QM-TT's design strategy incorporated key elements.These included a robust electron-donating triphenylamine unit, a π-bridge with thiophene, and an electron-withdrawing pyridinium unit.The intricate D-π-A effect effectively minimized the energy gap (∆E ST ) and facilitated intersystem crossing (ISC) processes, ultimately enhancing the production of ROS.The incorporation of a negatively charged anion within the pyridinium group created an electron-rich milieu, facilitating electron transfer and promoting type I ROS generation.
These intricate design principles empowered Pys-QM-TT to generate type I and type II ROS.The findings highlighted Pys-QM-TT's potential to simultaneously generate type I and type II ROS with reduced reliance on specific environmental conditions, such as hypoxia.More in-depth investigations into the mechanism revealed that, under photoactivation, Pys-QM-TT instigated cell apoptosis.This was marked by the increased expression of the pro-apoptotic protein Bax and the decreased expression of anti-apoptotic proteins, notably Bcl-2.It was found that this apoptotic process was mediated through the mitochondrial pathway.Moreover, its multifaceted attributes were highlighted, encompassing its ability to combat bacterial infections, ablate tumor tissue, and exhibit anti-angiogenic effects.
Simultaneously, Yu et al. unveiled a compelling approach to initiate apoptosis in cancer cells through the mitochondrial pathway. [75]This innovative technique involved the seamless integration of synthetic AIEgens with living organelles and mitochondria, yielding a synergistic framework for cancer treatment (Figure 2C).Earlier research has highlighted the potential of replacing dysfunctional mitochondria with functional ones from healthy cells. [76]This process involved the substitution of Bcl-2 overexpression in dysfunctional mitochondria with fully functioning ones, resulting in an F I G U R E 1 (A) A brief history of the regulated cell death research.Reproduced under the terms of the Creative Commons Attribution 4.0 International License. [53]Copyright 2019, Springer Nature, Published by the Authors.augmented apoptotic response of tumor cells to ROS. [77][78][79] The non-covalent interaction of a mitochondrial-targeted AIEgen (DCPy) with healthy and vibrant mitochondria was named Mito@DCPy and exhibited notable qualities.Notably, Mito@DCPy not only generated ROS upon exposure to microwave irradiation but also triggered apoptosis within deep tissue cancer cells.This gave rise to a captivating prospect-the potential to recalibrate the metabolic pathways of cancer cells, transitioning from glycolysis to oxidative phosphorylation (OXPHOS) (Figure 2D). [80,81]This has the potential to bolster the efficacy of nonthermal microwave therapy.The convergence of synthetic AIE technology and natural organelles introduced a novel dimension in the pursuit of effective strategies for cancer treatment.
In the pursuit of enabling deep tissue imaging of biological structures and activities, Chen et al. developed a novel AIE active photosensitizer, named TTTP, featuring a pyridinium group for precise mitochondrial targeting (Figure 3A). [82]The design of TTTP yielded interesting photophysical characteristics, impressive biocompatibility, and the unique ability to generate ROS for anticancer efficacy and two-photon imaging.Notably, TTTP demonstrated remarkable cellular uptake and selective accumulation within the mitochondria.Upon exposure to light irradiation, substantial enhancement in ROS generation was observed, actively triggering apoptosis.In in vivo experiments for tumor PDT, TTTP demonstrated substantial inhibition of tumor growth.Additionally, understanding the mechanisms behind TTTP's The primary pathways of ROS-induced apoptosis are illustrated in the schematic diagram.(B) Apoptosis is induced by AIE PSs, namely Pys-QM-TT, Pys-QM-T, and Pys-QM-N, as depicted in the chemical structures.(C) Pys-QM-TT is shown to stimulate the expression of apoptosisrelated proteins.Reproduced with permission. [74]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (D) The chemical structure of DCPy and the preparation schematic diagram for Mito@DCPy are presented.(E) Microwave activation of Mito@DCPy in tumor cells induces apoptosis, as illustrated in the schematic diagram.Reproduced with permission. [75]Copyright 2023, Wiley-VCH Verlag GmbH & Co.
tumor-suppressive effects revealed an increase in the apoptosis agonist Bax and a corresponding decrease in the antagonist Bcl-xL (Figure 3B).Consequently, TTTP gained recognition as a vital agent in the induction of cell apoptosis through the mitochondrial stress pathway.This research not only presented a promising mitochondrial-targeted phototherapeutic entity but also emphasized its efficacy for therapy and its applicability in two-photon fluorescence imaging.
In 2022, Xue et al. made noteworthy strides by devising a series of near-infrared (NIR) AIEgens (DTTVQ-OH) that specifically targeted mitochondria (Figure 3C). [83]This accomplishment was realized through the control of the donor-acceptor (D-A) intensity assembly in molecular engineering.Specifically, by introducing a π-bridge between the electron donor and acceptor, providing better charge transfer efficiency, and simultaneously increasing the conjugation of the electron acceptor to obtain near-infrared fluorescence emission.This compound exhibited remarkable traits such as robust photostability, biocompatibility, and precise targeting of mitochondria.Its ability to generate singlet oxygen ( 1 O 2 ) was particularly striking, surpassing that of Rose Bengal by a factor of 4.9.Beyond this, conducting apoptosis assays through flow cytometry corroborated the efficacy of DTTVQ-OH in restraining cell proliferation while expediting cancer cell death (Figure 3D).
Similarly, in 2023, Wu et al. utilized the concept of enhanced ICT to conceive and synthesize a new set of nearinfrared (NIR) AIEPSs. [84]The compounds were constructed around the thieno [3,2-c] pyridinium framework and were deliberately engineered to effectively target mitochondria (Figure 3E).The produced strong ICT effect yielded several characteristics for LIQ-TPA-DTZ, including NIR emission, AIE performance, high quantum yield (QY), and efficient generation of singlet oxygen ( 1 O 2 ) and hydroxyl radicals The chemical structure of TTTP is presented.(B) TTTP is shown to induce the expression of apoptosis-related proteins.Reproduced with permission. [82]Copyright 2023, Elsevier.(C) The chemical structure of DTTVQ-OH is displayed.(D) Flow cytometry analysis is conducted after culture with PSs.Reproduced with permission. [83]Copyright 2022, Elsevier.(E) The chemical structure of LIQ-TPA-DTZ is outlined.(F) Flow cytometry analysis is performed after culture with PSs.Reproduced with permission. [84]Copyright 2023, Elsevier.(G) The chemical structures of TPA-DHPy and TPA-Py are delineated.(H) Annexin V-633 kit analysis is carried out after culture with PSs.Reproduced with permission. [89]Copyright 2022, Elsevier.(I) The chemical structure of p-CN-DPAs is presented.(J) p-CN-DPAs are demonstrated to induce the expression of apoptosis-related proteins.Reproduced with permission. [87]opyright 2022, Elsevier.(K) The chemical structures of MTTB-OH and MTOQS are illustrated.(L) PSs induce the expression of apoptosis-related proteins.Reproduced with permission. [88]Copyright 2023, Elsevier.(M) The chemical structure of TAB-4-Gal is depicted.(N) AV-647 kit analysis is conducted after culture with PSs.Reproduced with permission. [93]Copyright 2022, Elsevier.
(•OH).Notably, AIEPSs displayed the ability to sensitively detect changes in mitochondrial polarity induced by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) in live cells within 10 min.Furthermore, it successfully initiated the mitochondrial apoptosis pathway, resulting in the PDT eradication of cancer cells and the hindrance of tumor growth in vivo (Figure 3F).
A further illustration of tumor cell apoptosis activation through the mitochondrial pathway was provided by the novel H 2 O 2 -activated photosensitizer, DPP-BPYS (Figure 4A). [85]his innovative compound, constructed using diketotolopyrrole (DPP), was reported by Li et al.Hydrogen peroxide (H 2 O 2 ), a common biomarker overexpressed in tumor tissue, serves as an optimal activator, selectively rekindling the photosensitivity of photosensitizers. [86]Upon activation, DPP-BPYS demonstrated typical AIE characteristics, a strong fluorescence quantum yield (5.4%), and a large Stokes shift (180 nm).Notably, upon activation, DPP-BPYS selectively targeted lipid droplets (LDs) within tumor cells, leading to aggregate formation, and effectively generating ROS ( 1 O 2 ) under white light irradiation.This process induces apoptosis through the mitochondrial pathway in tumor cells.As a result, this research presented a distinctive molecular instrument for H 2 O 2 -activated PDT anticancer therapy, opening new possibilities in the field.

2.1.2
Triggering apoptosis through the endoplasmic reticulum stress Similar to mitochondria, the ER assumes a vital role in apoptosis processes.This highlights the pressing need for the development of ER-targeting theranostic agents to facilitate precision treatments.Presently, the effective and dependable strategies for constructing ER-targeting probes are regrettably constrained.In addressing this issue, the Tang group made significant progress by successfully conceiving a series of ER-targeting AIEgens that initiated cancer cell apoptosis through ER stress (Figure 3I). [87]These compounds were all based on the keto-salicylaldehyde parent and regulated the luminescence properties via the introduction of different electron-withdrawing groups and the subcellular localization properties by varying the numbers and sites of phenolic hydroxyl groups.Among these probes, p-CN-DPAs displayed the highest fluorescence quantum yield and excellent ER targeting ability.Noteworthy, since the The chemical structures of DPP-BPYS and DPP-BPY are outlined.(B) Schematic representation of the chemical structure of CCNU980 and its self-assembly into nanoparticles.Reproduced with permission. [112]Copyright 2022, Wiley-VCH Verlag GmbH & Co. (C) Schematic representation of the chemical structure of DHTDP and its self-assembly into nanoparticles.Reproduced with permission. [101]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (D) Schematic representation of the chemical structure of NMB and its self-assembly into nanoparticles.Reproduced with permission. [102]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (E) Schematic representation of the chemical structure of DHTDP and its self-assembly into nanoparticles.Reproduced with permission. [103]Copyright 2022, Royal Society of Chemistry.(F) Schematic representation of the chemical structure of TBDCR and its self-assembly into nanoparticles.Reproduced under the terms of the Creative Commons Attribution 4.0 International License. [114]Copyright 2023, Wiley-VCH Verlag GmbH & Co, Published by the Author(s).generated ROS from p-CN-DPAs adeptly induced ER stress, it initiated cancer cell apoptosis and effectively hampered tumor cell proliferation both in vitro and in vivo (Figure 3J).Hence, this work provided concepts for the development and design of future endoplasmic reticulum-targeted apoptosis inducers.
In a different case study concerning AIEgen-induced apoptosis, Yang et al. presented a potent AIE-type molecule targeted at the ER known as MTOQS (Figure 3K). [88]otably, MTOQS showed exceptional efficacy in generating ROS both in vitro and in vivo.The observed ROS production played a pivotal role in the reduction of elevated levels of GSH and MDA within cancer cells by facilitating intracellular ROS accumulation.Comprehensive analysis, involving diverse markers such as ATP, L-lactic acid, the anti-apoptotic factor Bcl-2, and the apoptotic protein caspase-3, unveiled the profound impact of oxidative stress on dual organelles induced by MTOQS.This stress mechanism orchestrated a decline in OXPHOS and glycolysis levels within cancer cells.Additionally, it incited a transformation in the cancer cell culture environment and induced stress through multiorganelle oxidative damage to the ER and mitochondria.The culmination of this multiorganelle oxidative stress cascade prompted the activation of the apoptosis pathway, resulting in cancer cell apoptosis (Figure 3L).The reported contribution emphasized the importance of accounting for the repercussions of PDT on secondary organelles.
Contemporaneously, the monitoring of critical organelles during oxidative stress and the implementation of therapeutics based on oxidative stress were of paramount importance but remained a challenging task.Therefore, Tang group presented a photoactivatable fluorescent probe, TPA-DHPy, which possessed a 1,4-dihydropyridine moiety with an AIE tendency (Figure 3G). [89]Undergoing photo-oxidative dehydrogenation, TPA-DHPy swiftly converts to its pyridine counterpart, TPA-Py.TPA-DHPy and TPA-Py function as photosensitizers in type I/type II PDT, efficiently producing ROS that induce in situ oxidative stress when exposed to white light irradiation.Cancer cells effectively internalized TPA-DHPy, allowing for dynamic visualization of LDs and ER.This allowed for real-time monitoring of differences and alterations in the microenvironment of LDs and ER under oxidative stress through multi-color fluorescence imaging.Additionally, the TPA-Py generated in situ disrupted LDs and ER functions, induced cell apoptosis, and effectively suppressed tumor growth with white light irradiation (Figure 3H).
[92] In 2020, Liu et al. designed and synthesized three fluorescent probes to be activated by β-galactosidase, based on triarylboron (TAB) (Figure 3M). [93]Notably, TAB-4-Gal exhibited the most outstanding features, completing the activation process within 4 min and producing the fluorescence signal.By introducing a piperazine group, TAB-4-Gal gains specificity and accumulates in lysosomes.Furthermore, under low-intensity visible light irradiation (1.5 mW/cm 2 ), TAB-4-Gal exhibited high photosensitivity, facilitating the selective induction of apoptosis in ovarian cancer cells (Figure 3N).This promising feature contributed to its potential as an effective therapeutic agent for ovarian cancer treatment.

Triggering apoptosis with AIE nanoparticles
Usually, small-molecule AIEgens, employed as photo/ sonosensitizers, frequently exhibit pronounced hydrophobic traits, which can impede their therapeutic effectiveness.100] Furthermore, it contributed to the mitigation of toxic side effects.Building upon these principles, the Tang group introduced a versatile molecule named DHTDP. [101]This molecule possessed attributes of AIE and facilitated both efficient photothermal conversion and second near-infrared (NIR-II) fluorescence emission.Through meticulous structural adjustments, DHTDP NPs were cloaked with cancer cell membranes, yielding biomimetic NPs that exhibited heightened delivery efficiency and homologous targeting prowess (Figure 4C).These biomimetic NPs enabled precise imaging guidance and maximized therapeutic outcomes through photoacoustic imaging (PAI), photothermal imaging (PTI), and NIR-II fluorescence imaging (FLI) trimodal imagingguided PTT.Under light irradiation, DHTDP NPs were observed to effectively induce apoptosis.Importantly, the xenograft tumor model demonstrated that the DHTDP NPs accomplished near-complete tumor ablation when they were subjected to light irradiation.The study presented the initial instance of biomimetic multimodal phototheranostics containing with homogeneity-targeting cell membranes.
In a similar report, Zhang et al. presented the rational development of tunable NPs utilizing AIE heaters. [102]his system combined the benefits of producing photothermal effects from nonspecific triggers and triggering carbon radical release.The NPs (NMB@NPs) encapsulated with NMDPA-MT-BBTD (NMB) underwent splitting under 808 nm laser irradiation due to the photothermal effect of NMB (Figure 4D).This leads to the decomposition of azo bonds within the nanoparticle matrix, which in turn generates carbon radicals.Additionally, the NMB emitted fluorescence within the NIR-II window (λ em = 1090 nm).Flow cytometry analysis revealed that the NMB@NPs efficiently facilitated cell apoptosis upon light activation.The combination of fluorescence image-guided thermodynamic therapy (TDT) and PTT, allowed the NMB@NPs to effectively inhibit the growth of oral cancer.This synergistic photothermal-thermodynamic strategy based on AIEgens provides novel perspectives for designing highly versatile fluorescent nanoparticles for precise biomedical applications.
In contrast to the conventional self-assembly approach using surfactants, Li et al. pursued a different strategy.Their method involved the integration of an AIE photosensitizer, hyaluronic acid (HA), and the photothermal material AuNSs to create a hybrid nanocomposite tailored for PTT and PDT synergistic therapy (Figure 4E). [103]To achieve their goal, a series of berberine dimers and a tetramer were synthesized via the conjugation of berberine subunits.Among them, BD3 displayed the highest ability to generate singlet oxygen ( 1 O 2 ).BD3 was combined with the photothermal material AuNSs to form a hybrid nanocomposite called AuNSs-BD3.This composite was subsequently coated with HA to specifically target cancer cells via the CD44 receptor on their surface.Upon cellular entry via CD44-mediated endocytosis, the internal hyaluronidase (HAase) enzyme digested the coated HA, releasing the AuNSs-BD3 nanosystem.The resultant AuNSs-BD3@HA configuration offered a threefold capability, encompassing PDT from BD3, PTT from AuNSs, and targeted delivery through HA.The synergistic effects of enhanced PTT and PDT resulted in superior apoptosis/necrosis of cancer cells in vitro and demonstrated potent anti-breast cancer activity in vivo.The reported findings from both in vitro and in vivo experiments substantiate the favorable therapeutic potential of this system.
[109][110][111] These shortcomings hinder the precise application of fluorescence imaging-guided SDT in vivo.Addressing the challenges posed by SDT, Zhang et al. developed CCNU980 NPs. [112]The NPs exhibited extended-wavelength emissions and were designed to specifically target mitochondria as organic nanosonosensitizers (Figure 4B).CCNU980 NPs exhibited high photostability, low phototoxicity, deep-tissue optical penetration (up to 6 mm), and depth-activated ROS production (up to 8 cm).In vitro studies confirmed the selective enrichment of CCNU980 NPs in cancer cells, showcasing the capability to target mitochondria and induce mitochondria-mediated apoptosis by generating abundant 1 O 2 under ultrasound (US) irradiation.Significantly, CCNU980 NPs enabled accurate in vivo NIR-II fluorescence imaging-guided SDT, effectively suppressing bilateral 4T1 tumor growth.This study inspired the formulation of a universal strategy for crafting organic nanosonosensitizers that exhibit long-wavelength emission.
X-ray-induced photodynamic therapy (X-PDT) addressed the limited penetration depth of conventional PDT while minimizing the generation of radio-resistance. [113]However, the conventional approach to X-PDT typically involved the use of inorganic scintillators as energy transducers to stimulate adjacent PSs and induce ROS production.In this particular context, the Tang group pioneered the development of a pure organic AIE nanoscintillator, known as TBDCR NPs (Figure 4F). [114]This nanoscintillator demonstrated the ability to robustly generate both type I and type II ROS upon direct X-ray irradiation, offering a solution for hypoxiatolerant X-PDT.To enhance X-ray harvesting and ROS generation, heteroatoms were introduced, and the AIE-active TBDCR exhibited aggregation-enhanced ROS production, particularly in the less oxygen-dependent hydroxyl radical (HO• − , type I) generation.TBDCR NPs, featuring a unique PEG crystalline shell that provided a rigid intraparticle microenvironment, exhibited further augmented ROS generation.Intriguingly, TBDCR NPs displayed bright near-infrared fluorescence and substantial singlet oxygen and HO• − generation under direct X-ray irradiation.This showcased excellent antitumor X-PDT performance both in vitro and in vivo.Notably, this marked the first instance of a pure organic PS capable of generating both 1 O 2 and radicals (HO• − ) in response to direct X-ray irradiation, offering valuable insights for designing organic scintillators with superior X-ray harvesting and predominant free radical generation for efficient X-PDT.

TRIGGERING PYROPTOSIS WITH AIE THERAPEUTIC AGENTS
The term "pyroptosis" finds its origins in the Greek words "pyro", meaning fire, and "ptosis", signifying falling.This combination, pyroptosis, can be interpreted as "fiery falling", encapsulating the concept of inflammatory chemical signals erupting from the perishing cell. [115]This term was coined in 2001 by Molly Brennan and Dr. Brad T. Cookson. [116]Pyroptosis has emerged as a form of lytic RCD, incited by inflammasomes that trigger caspase-1 activation, leading to the cleavage of gasdermin-D (GSDMD).The cleaved GSDMD then liberates gasdermin-N domains (N-GSDMD), which subsequently migrate to the cell membrane.This migration results in the creation of membrane pores, designated as GSDMD pores, ultimately propelling processes such as cell swelling, membrane rupture, and cell demise. [117,118]In comparison to apoptosis, pyroptosis is a more promising avenue for cancer therapy.This arises from its ability to induce anti-tumor immune responses through the release of cellular components, including lactate dehydrogenase (LDH), as well as inflammatory cytokines such as interleukin-1beta (IL-1β) and interleukin-18 (IL-18).(Figure 5A). [119]The recent revelation of pyroptosis as a distinctive variant of RCD has gained substantial interest for its potential application in cancer treatment. [120,121]t is worth noting that pyroptosis is frequently induced by chemotherapeutic drugs. [122]Nevertheless, the activation of this process via chemotherapeutic drugs frequently constrains its anti-tumor applications, attributed to both drug resistance and the occurrence of severe side effects.In 2021, Liu's research group introduced a groundbreaking approach involving membrane-targeting photosensitizers capable of inducing pyroptosis for the noninvasive and minimally sideeffect-driven ablation of cancer cells. [123]They developed a series of membrane anchoring photosensitizers, denoted as TBD (Figure 5B), characterized by AIE.This was achieved through the conjugation of TBD with phenyl rings containing cationic chains.Under light irradiation, in situ generation of cytotoxic ROS occurred, resulting in direct membrane damage and highly efficient ablation of cancer cells.A detailed investigation revealed that with the enhanced cell membrane targeting ability of the PS, it was more likely to induce pyroptosis.This work revealed that a cell membrane-targeted PS could be used as a potential inducer to directly trigger pyroptosis.
Subsequently, the Liu group utilized the membranetargeted PS TBD-3C to trigger pyroptosis-induced cancer immunotherapy through PDT. [124]The findings suggested that TBD-3C-induced pyroptotic cells could initiate M1polarization in macrophages, boost maturation of dendritic cells (DC), and activate CD 8+ cytotoxic T-lymphocytes (CTLs).The immunological responses triggered by pyroptosis transformed the immunosuppressive "cold" tumor microenvironment (TME) into an immunogenic "hot" TME.This transformation resulted in not only the suppression of primary pancreatic cancer growth but also the targeting of distant tumors.The reported research established a highly biocompatible platform for light-regulated antitumor immunity and solid tumor immunotherapy initiated through cell pyroptosis.
Although activation of pyroptosis by AIEgens has become a fairly promising therapeutic strategy, the absence of a pyroptotic inducer with imaging capabilities has impeded the advancement of theranostics in tumors.In a separate work reported in 2023, Yu et al. developed a mitochondria-targeted AIEgens called TPA-2TIN, which emitted near-infrared (NIR-II) light to efficiently induce pyroptosis in tumor cells (Figure 5C). [125]The TPA-2TIN water-soluble NPs (encased within the amphiphilic polymer DSPE-PEG2k.) were engineered to be effectively taken up by tumor cells and selectively accumulate in the tumor for prolonged periods, as observed through NIR-II fluorescence imaging.Importantly, the NPs showed the ability to stimulate immune responses both in vitro and in vivo by triggering mitochondrial dysfunctions and activating the pyroptotic pathway.As a result, the reversed immunosuppressive tumor microenvironment significantly enhanced the effectiveness of immune checkpoint therapy.
In 2023, Tang et al. discovered a tumor cell membranetargeted AIE photosensitive dimer (D1) (Figure 5D) capable of achieving highly efficient ICD through a synergistic effect of photodynamic and photothermal therapy. [126]The D1 effectively generated type-I ROS via PDT in hypoxic tumor tissue and induced pyroptosis through direct cell membrane damage, which was further enhanced by its photothermal effect.Moreover, the enhanced ICD effect achieved by the D1 demonstrated remarkable results in the treatment of 4T1 tumor mouse models with poor immunogenicity.It was found that on the seventh day of treatment, the primary tumor was completely eliminated, and the therapy also boosted systemic antitumor immunity by generating immune memory.Consequently, this approach exhibited superior therapeutic effects against both solid tumors and metastatic tumors.
The activation of the cyclic GMP-AMP synthaseinterferon gene stimulator (cGAS-STING) pathway stands as a potent approach for anti-tumor immunotherapy.The combination of the activation of cGAS-STING with pyroptosis induction offered viable means to further amplify the anti-tumor immune response.This concept was the foundation for Ling et al. work, where two Pt II complexes, named Pt1 and Pt2 (Figure 5E), were devised capable of dual activation of the cGAS-STING pathway and pyroptosis. [127]nder light irradiation, Pt1 and Pt2 sequentially impaired mitochondrial DNA (mtDNA), the nuclear envelope, and nuclear DNA (ncDNA), which comprises G-quadruplex (G4) DNA and double-stranded DNA (dsDNA).This cascade of damage culminated in the activation of the cGAS-STING pathway.Notably, following light irradiation, Pt1 and Pt2 also induced pyroptosis, thereby augmenting the immune response (Figure 5F).In vivo experiments further demonstrated that Pt1 and Pt2 effectively curbed tumor growth, promoting the release of cGAMP and proinflammatory cytokines.These complexes also elevated the proportions of CD 8+ and CD 4+ T cells while facilitating DC maturation.In essence, this study introduced the first example of small Reproduced with permission. [125]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (D) The chemical structure of D1 is presented, and its capacity to induce the expression of pyroptosis-related proteins is highlighted.Reproduced with permission. [126]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (E) Chemical structures of Pt1 and Pt2 are displayed.(F) Illustrative depiction of cell morphological changes induced by phototherapy.(G) Pt1 and Pt2 are demonstrated to induce the expression of pyroptosis-related proteins.Reproduced with permission. [127]Copyright 2022, Wiley-VCH Verlag GmbH & Co. (H) The chemical structures of NI-TA are depicted.(I) NI-TA is revealed to induce the expression of pyroptosis-related proteins.Reproduced with permission. [128]opyright 2022, American Chemical Society.(J) Schematic representation of the chemical structure of TPRA-SS-DAC and its self-assembly into nanoparticles is provided.(K) TSD@LSN-D induces pyroptosis-related protein expression and demonstrates tumor suppression in vivo.Reproduced with permission. [133]opyright 2023, Wiley-VCH Verlag GmbH & Co.In 2022, our group designed and synthesized NI-TA, a photocatalytic superoxide radical (O 2 •− ) generator capable of initiating pyroptosis in cancer cell (Figure 5H). [128]NI-TA employed an intramolecular modulation approach to split the triplet-ground state energy.Detailed investigations revealed that NI-TA induced pyroptosis in cancer cells through the caspase-3/gasdermin E (GSDME) pathway, deviating from the canonical process involving caspase-1/gasdermin-D (GSDMD) (Figure 5I).Notably, NI-TA operated through a partial-O 2 -recycling mechanism, enabling effective cell pyroptosis and cancer cell ablation, even under hypoxic conditions (≤2% O 2 ).In 3D multicellular spheroids of T47D, NI-TA showed excellent antitumor efficiency and inhibited stemness.
[131][132] In 2023, Wang et al. showed that the administration of lower doses of the epigenetic drug decitabine could elevate GSDME expression in prostate cancer (PCa) RM-1 cells. [133]This led to the successful transition from apoptosis to pyroptosis following PDT.Subsequently, the researchers engineered a dual-responsive nano-drug named TSD@LSN-D, which was comprised of a PD-L1 blocking peptide (DPPA), a covalent conjugate of AIE photosensitizer, and decitabine (Figure 5J).In experiments using an RM-1 PCa model characterized by poor immunogenicity, the administration of TSD@LSN-D promoted a robust antitumor immune response.This response not only effectively curtailed the growth of the primary tumor but also established a lasting immune memory that served to prevent the recurrence and metastasis of PCa.The study introduced the groundbreaking concept of promoting the transition from apoptosis to pyroptosis after tumor PDT through the modulation of epigenetic factors.Furthermore, the potent synergy between immunogenic pyroptosis and ICB offered a novel platform for the advancement of PCa immunotherapy.

TRIGGERING IMMUNOGENIC CELL DEATH WITH AIE THERAPEUTIC AGENTS
ICD refers to any type of cell demise that triggers an immune response, and this concept forms the basis of immunotherapy. [134]When tumor cells succumb to external stimuli, the transition from being non-immunogenic to becoming immunogenic occurs. [134]ICD takes place within tumor cells, setting off the release of the signaling molecules referred to as damage-associated molecular patterns (DAMPs). [135]Among these, Calreticulin (CRT) is considered significant as it becomes exposed to the cell surface.Simultaneously, tumor cells secrete High Mobility Group Protein 1 (HMGB1) into the extracellular.In addition, ATP molecules are liberated from the cells, along with heat shock proteins (HSP70, HSP90), among other factors.The collection of DAMPs, liberated during the process of ICD, binds to pattern recognition receptors (PRRs) present on the surface of DC cells. [136]This interaction initiates a sequence of cellular responses, culminating in the activation of both innate and adaptive immune reactions (Figure 6). [137]

Triggering ICD with self-assembled AIE nanoparticles
AIEgens exhibit heightened sonosensitivity within nanocarriers compared to traditional organic sonosensitizers due to their intense fluorescence emission in aggregated states.However, the clinical application of current AIE nanosonosensitizers is severely limited due to issues such as premature drug leakage and inadequate tumor targeting. [138,139]In 2023, Deng et al. described a potent AIEgen-based sonosensitizer (AIE/BiotinM), which was achieved via the assembly of AIE-1 and amphiphilic polymers (DSPE-PEG-Biotin) targeting 4T1 tumors (Figure 7B). [140]This innovative approach facilitated the efficient delivery of salicylaldazine to 4T1 tumor tissues, aiming to enable immunogenic SDT.In vitro assessments demonstrated the exceptional stability and prolific generation of 1 O 2 upon US irradiation by AIE/Biotin-M.When  R837, where AIE@R837 NPs induce tumor suppression in vivo.Reproduced with permission. [146]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (H) Presentation of the chemical structures of (TPE-DPA) 2 -Py and B-AGL-HCPT.(I) Schematics of the chemical structure of TSSI, the structure of tvHMS, and schematics of H2S release and photodynamic mechanism, along with in vivo tumor suppressor structures.Reproduced under the terms of the Creative Commons Attribution 4.0 International License. [151]Copyright 2023, Springer Nature, Published by the Author(s).(J) Illustration of a schematic diagram depicting AIE therapeutic agents or their nanoparticles synergizing with immune checkpoint inhibitors.(K) Presentation of the chemical structure of α-Th-TPA-PIO and the schematics of αPD-L1.(L) Presentation of the chemical structure of TPE-BT-BBTD and its self-assembly into nanoparticles.Reproduced with permission. [156]Copyright 2022, Wiley-VCH Verlag GmbH & Co. (M) Presentation of the chemical structure of TPA-BT-DPTQ and the schematics of αPD-L1.
AIE/Biotin-M accumulated in tumors under US irradiation, not only did it induce cancer cell death through 1 O 2 production but also triggered an ICD, eliciting a systemic immune response.Beyond SDT mediation, AIE/Biotin-M chelated and reduced Fe 3+ , Cu 2+ , and Zn 2+ through salicylaldazine, which effectively inhibited neovascularization within tumor tissues.Ultimately, the AIE/BiotinM approach effectively curbed tumor growth and metastasis upon US irradiation.
Multifunctional phototheranostics, which integrate multiple diagnostic and therapeutic strategies into one platform, are significant for ICD.However, achieving optimized multimodality optical imaging and therapy properties in a single molecule proves challenging due to the fixed absorbed photoenergy.Hence, Gao et al. ingeniously crafted a versatile nanoagent (Figure 7C). [141]The described design relied on a dithienylethene-based molecule with two light-switchable forms.Each form of the molecule exhibited different photophysical properties, allowing selective activation based on external light stimuli.In its ring-closed form, the molecule predominantly dissipates absorbed energy via nonradiative thermal deactivation for photoacoustic (PA) imaging.However, the ring-open form exhibited apparent AIE features, with excellent fluorescence and PDT properties.In vivo experiments showed that preoperative PA and fluorescence imaging provided high-contrast tumor delineation, and intraoperative fluorescence imaging sensitively detected residual tumors.Additionally, the nanoagent (encased within the amphiphilic polymer DSPE-PEG 2000 ) induced ICD, elicited antitumor immunity, and effectively suppressed solid tumors.This study presented a versatile agent with photophysical energy transformation and phototheranostic properties.The adaptability of this agent can be optimized through a lightdriven structure switch, making it promising for diverse biomedical applications.
Leveraging endogenous biomacromolecules as carriers hold tremendous potential to significantly enhance the bioavailability of AIEgens. [142,143]In 2023, an innovative stride was taken by Liu et al., who developed a methodology to amplify immunotherapeutic efficacy (Figure 7D). [144]In this innovative approach, bovine serum albumin (BSA) NPs loaded with an AIE photosensitizer, referred to as BSA/TPA-Erdn, were utilized.These NPs were designed to activate T cells, convert the "cold" tumor into a "hot" one, and counteract T cell senescence.This strategy aimed to restore the immune microenvironment for the treatment of multiple myeloma (MM).To attain this objective, an AIE photosensitizer was incorporated into the hydrophobic domain of BSA proteins, markedly immobilizing the molecular geometry.As a result, there was a substantial increase in ROS generation, leading to an ICD immune response.The NPs successfully simulated human dendritic cell maturation, activated functional T lymphocytes, and enhanced additional polarization and differentiation signals, exhibiting promising performance in immunotherapy.Intriguingly, BSA/TPA-Erdn could effectively reverse T cell senescence, a significant challenge in MM treatment.Additionally, the reported NPs attracted more functional T lymphocytes into the MM tumor, further contributing to the restoration of the MM immune microenvironment.
Combining AIE photosensitizers with chemotherapy drugs and immune checkpoint inhibitors stood as a dependable approach to realizing potent photoactivated anti-tumor immunotherapy.Building upon this concept, in 2023, Wang et al. introduced a novel second near-infrared window (NIR-II) AIE molecule (termed TST) (Figure 7F). [145]This molecule possessed AIE attributes and PTT capabilities.To enhance its fluorescent yield and therapeutic potential, TST was co-assembled with a prodrug (CPT-S-PEG) and a novel immune checkpoint inhibitor, AZD4635, to form NPs for efficient drug delivery.The strong interaction between the prodrug and TST restricted the rotation of TST within intact NPs.This limitation curtailed non-radiative attenuation and boosted fluorescence generation.When the NPs were absorbed by cancer cells, the CPT-S-PEG underwent degradation, leading to the disintegration of the NPs.Simultaneously, the release of TST, no longer constrained by the NPs, allowed TST to release energy through the photothermal effect for photothermal therapy.Moreover, PTT promoted ICD and released ample ATP into the tumor microenvironment to attract immune cells.Nonetheless, the excess ATP was transformed into immunosuppressive adenosine through the CD39-CD73-A2AR pathway, which was effectively blocked by the timely release of AZD4635 resulting from the disintegration of NPs.This strategic intervention created a synergistic effect that seamlessly combined photothermal therapy, chemotherapy, and immunotherapy, thereby maximizing therapeutic outcomes.
In 2023, Xu et al. introduced an innovative approach to combine certain therapies for cancer treatment. [146]his approach integrated the immune activator R837 with the AIE phototherapeutic agent (T-TBBTD) within an NP (Figure 7G).T-TBBTD possessed a complex D-A-D structure, an enhanced distorted molecular conformation, extended into NIR-II emission (λ em = 1163 nm), and featured multimodal imaging capabilities.Upon exposure to AIE@R837 light, it generated substantial heat and released 1 O 2 .The observed dual effect of PDT combined with immune activation directly eradicated tumor cells and triggered an ICD, subsequently eliciting a systemic immune response.The proposed nanosystem played a pivotal role in enhancing the immune system against tumor cells, capable of engendering enduring protective anti-tumor immunity post the elimination of tumor tissues.The strategy underwent rigorous testing using a bilateral 4T1 tumor model, there the photoimmunotherapy not only eradicated the primary tumor but also exerted a pronounced inhibitory effect on the growth of distant tumors.These findings highlighted the potential utility of AIE@R837 NPs as a potent tool for cancer therapy.
Despite the plethora of reported ICD-based systems, the development of near-infrared afterglow ICDs that can be activated is notably sparse.In 2022, Ding group introduced a novel self-reporting NIR afterglow theranostic prodrug that exhibited a unique ability to respond to the progression of ICD and the transformation of "cold-to-hot" tumor states (Figure 7H). [147]Constructed within a single nanoparticle (AIE/BAGL-HCPT NPs), the prodrug encapsulated the afterglow hydroxycamptothecin (HCPT) prodrug (B-AGL-HCPT) along with an AIE photosensitizer ((TPE-DPA) 2 -Py).The composition of B-AGL-HCPT involved HCPT and Schaap's adamantylidene-enol ether precursor, which was linked via a carbonate group and caged with a peroxynitrite (ONOO)-responsive phenylborate protecting group.Meanwhile, the unique three-dimensional twisted conformation and the presence of a cationic pyridine unit in (TPE-DPA) 2 -Py enhanced its brightness and efficiency in generating 1 O 2 in aggregated states.Upon exposure to light irradiation, AIE/B-AGL-HCPT NPs accumulated in the tumor tissue and generated 1 O 2 , thereby facilitating photodynamic cancer cell ablation while inducing ICD.However, the approach went beyond tracking HCPT release and intratumoral ONOO levels-it introduced the concept of HCPT amplification of photodynamic therapy-mediated ICD.In vivo experiments demonstrated that under the action of these multifunctional NPs, substantial maturation of dendritic cells, activation of T cells, and exceptional cancer theranostic performance occurred, effectively eliminating the existing tumors and preempting recurrence.
[150] In 2023, Wang et al. elucidated the remarkable immunoadjuvant potential of gas therapy in conjunction with cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation, which specifically enhanced AIEgen-based photoimmunotherapy (Figure 7I). [151]To achieve this goal, the researchers innovatively designed a virus-mimicking hollow mesoporous structure doped with tetrasulfide to encapsulate both AIEgen and manganese carbonyl, creating a unique gas nanoadjuvant.By exploiting the responsiveness of the tetra-sulfide bonds that bind to intratumoral glutathione, this gas nanoadjuvant exhibited targeted drug release within tumors.This, in turn, catalyzed photodynamic therapy and triggered the release of hydrogen sulfide (H 2 S).Under near-infrared laser irradiation, phototherapy mediated by AIEgen triggered a burst release of carbon monoxide (CO)/Mn 2+ .Notably, both H 2 S and CO disrupted mitochondrial integrity, resulting in the release of mitochondrial DNA into the cytoplasm. [152,153]These actions collectively served as gas-based immunoadjuvants, activating the cGAS-STING pathway.Furthermore, the presence of Mn 2+ enhanced cGAS sensitivity, amplifying STING-mediated type I interferon production.The cumulative effect of the gas nanoadjuvant strategy significantly potentiated photoimmunotherapy within poorly immunogenic breast tumors of the female mice.The described advancement showed the potential of gas therapy in combination with AIEgen-based approaches.
ER stress, a precursor of ICD, was directly triggered by ROS in situ. [154]In 2020, Tang group designed and prepared a new PS (α-Th-TPA-PIO), featuring AIE with excellent hydroxyl radicals (•OH) generation ability (Figure 7K). [155]emarkably, α-Th-TPA-PIO specifically accumulated in the ER and induced ER stress upon exposure to white light, leading to effective ICD.The combination of α-Th-TPA-PIO with anti-programmed death-ligand 1 (anti-PD-L1, to enhance the immune response by preventing immune evasion), resulted in a synergistic effect of PDT and ICB.This dual approach resulted in significantly improved suppression of tumor growth while concurrently eliciting a systemic antitumor immune response.Significantly, this therapeutic approach successfully restrained the growth of both primary and distant subcutaneous tumors and partially inhibited metastatic tumor progression.Hence, the reported study not only introduced a novel ICD photoinducer through PDT but also presented a valuable immunomodulatory strategy for achieving an enhanced antitumor effect.
To effectively tackle pressing challenges in the treatment of advanced deep-seated tumors, a novel solution has emerged-a 980 nm absorbing AIEgens PS, named TPE-BT-BBTD (Figure 7L). [156]Importantly, this AIEgen features the longest absorption wavelength among the observed reported AIE molecules.Its functionality aligned perfectly with NIR-II FLI and outstanding PCE, making it ideally suited for advanced pancreatic cancer treatment.Through the covalent attachment of the αPD-L1, αPD-L1@TPE-BT-BBTD NPs demonstrated precise tumor targeting and outstanding immunosuppression reversal.Local PTT triggered an immunogenic tumor vaccination, leading to the infiltration of CTLs.The reduction of FoxP3 + Treg cells and M2like macrophages, which was reversed by αPD-L1, further amplified CTL activity, resulting in enhanced granzyme B (GrB) production.Consequently, this indicated tumor apoptosis and effectively curtailed spontaneous metastases.Overall, αPD-L1@TPE-BT-BBTD NPs, guided by NIR-II FLI-mediated photo-immunotherapy, significantly advanced the primary tumor and metastasis control in advanced deep-seated tumors.
The concept of synergistic photothermal immunotherapy has garnered significant attention due to its ability to mutually enhance therapeutic outcomes for both primary tumors and abscopal tumors. [157]In 2022, Tang group introduced a versatile theranostic agent known as TPA-BT-DPTQ, designed and synthesized with the benzo[c]thiophene unit as a foundational component.(Figure 7M). [158]The prepared agent served a dual purpose, offering simultaneous functionalities for FLI within the NIR-II window.Additionally, it provided capabilities in PAI, PTI, and tumor thermal eradication.Experimental assessments substantiated the efficacy of PTT facilitated by TPA-BT-DPTQ NPs.Beyond merely eliminating the primary tumor, this therapy showcased the ability to enhance immunogenicity, subsequently inhibiting the growth of tumors located at distant sites.Significantly, the combination of PTT with a PD-L1 antibody acted as a strategic intervention.This synergistic approach not only thwarted cancer metastasis and recurrence but also potentiated the efficacy of immunotherapy, promising comprehensive therapeutic outcomes.

Triggering ICD with bioinspired AIE nanoparticles
NPs loaded with drugs can function as effective carriers, guided to specific targets using diverse surface moieties. [159][162] In recent years, the emergence of cell-mediated drug delivery systems as promising strategies has occurred. [163]By leveraging unique cell properties such as extended blood circulation, abundant surface ligands that potentially enable specific hitchhiking, targeted tumor cell interactions, and adaptable morphology that navigates biological barriers, these systems optimize therapeutic outcomes while minimizing side effects. [164]Cell membrane-coated NPs hold particular interest due to their emulation of cellular surface characteristics.The NPs not only alleviate immune responses against synthetic NPs in vivo but also surmount various limitations associated with monotherapy.
To enhance the targeting capability of AIEgen PS, Lin et al. prepared a tumor-associated macrophage (TAM)-specific peptide (CRV) into exosomes derived from lung cancer cells (Figure 8B). [165]This resulted in the creation of CRVengineered exosome membranes (CRV-EM) that camouflage AIEgen PS (BITT) NPs (CEB).The CRV-EM camouflage enhanced the surface function of BITT NPs, enabling effective cellular uptake in both lung cancer cells and TAMs.In vitro and in vivo experiments demonstrated that CEB induced  [179] Copyright 2022, American Chemical Society.(J) Illustration depicting a cell membrane-coated nanoparticle serving as carriers for AIE therapeutic agents.(K) Presentation of the chemical structure of TBP-2.(L) Display of representative Ki67 and CRT stained tumor sections from mice in the indicated treatment groups.Reproduced with permission. [180]Copyright 2022, Elsevier.
significant cell death when exposed to laser irradiation.Furthermore, CEB exhibited an extended circulation lifetime and accumulated efficiently in tumors, leading to efficient PDT and PTT.Additionally, CEB facilitated the remodeling of the tumor microenvironment by increasing the presence of CD 8+ and CD 4+ T cells while decreasing M2 TAM and Myeloidderived suppressor cells (MDSCs).This work introduced a novel bioinspired AIE aggregate style that effectively eliminates both lung cancer cells and TAMs, resulting in efficient lung cancer therapy.
Typically, the PTT process elevates the expression of heat shock proteins (HSPs) within tumor cells, reducing the sensitivity of these cells to heat.This has long been a significant obstacle limiting the effectiveness of PTT. [166]In response, Yang, et al. developed a specialized type of photothermal agents called DC@BPBBT dots (Figure 8C). [167]These dots possessed biomimetic AIE attributes and the capability to adhere to other cells.This was achieved by enveloping nanoaggregates of NIR AIE polymeric photothermal agents with membranes from DC. Importantly, the DC@BPBBT emitted strong NIR-II fluorescence with a high quantum yield of up to 3.47%.Additionally, it exhibited exceptional photothermal conversion performance, achieving a PCE of up to 30.5%.The cell membrane allowed the DC@BPBBT dots to adhere to endogenous T cells and significantly improved the efficiency of delivering these agents to tumors, increas-ing the delivery effectiveness by approximately 1.2 fold.Furthermore, the DC@BPBBT dots were able to activate and stimulate T cells within living organisms and release a cytokine called tumor necrosis factor α (TNF-α).This cytokine played a role in reducing the levels of HSP70, rendering the cells more responsive to heat.Essentially, this research described an innovative approach to inhibit heat shock proteins by utilizing interactions with immune cells.
The rapid metabolism of cancer cells results in a condition of low oxygen levels (hypoxia) and a shortage of vital nutrients within the microenvironment of the tumor. [168]hese factors impede the proper functioning of immune cells. [168]To address this, Tang group developed a specialized nanoplatform that mimics the characteristics of the immune system and cancer cell metabolism (Figure 8D). [169]he platform incorporated a type I photosensitizer that emitted light upon aggregation, in conjunction with a compound that blocked the uptake of glutamine (an essential nutrient for cancer cells).These components were enclosed within a membrane derived from cancer cells, facilitating targeted delivery within living organisms.The proposed innovative approach effectively supplied the necessary glucose and glutamine for optimal T cell function.Additionally, it not only relieved hypoxic conditions within the tumor environment but also led to the metabolic reprogramming of both tumor and immune cells.The observed reprogramming initiated a type of cell death that triggered ICD.It also contributed to DC maturation, a vital component of the immune system, effectively restraining tumor growth.Furthermore, it induced robust tumor-specific immune responses and countered the immune-suppressive conditions within the tumor microenvironment by reducing the number of immune-inhibitory cells.When combined with anti-PD-1 treatment, a form of immunotherapy, a pronounced "abscopal effect" occurred, which prevented the distant spread of the tumor (metastasis) and established enduring immune memory to protect against tumor recurrence over the long term.
The success of tumor immunotherapy demonstrates the feasibility of utilizing the immune system to combat cancer. [170]Vital to this effort was the activation of both native and fatigued T cells, a pivotal step in generating robust antitumor immunity. [171]This relies on the adept presentation of tumor antigens and costimulatory signals by antigen-presenting cells, coupled with the reversal of the immunosuppressive state. [172]Nonetheless, achieving effective antigen presentation and ameliorating the immunosuppressive microenvironment remain a challenge. [173]In 2023, a novel approach was introduced wherein AIE PSloaded nano-superartificial dendritic cells (saDC@Fs-NPs) were designed (Figure 8F). [174]This entailed encapsulating nanoaggregates of AIE-PS with superartificial dendritic cell membranes derived from genetically engineered 4T1 tumor cells.The outer cell membranes of saDC@Fs-NPs originated from 4T1 tumor cells infected with recombinant lentivirus, concurrently incorporating peptide-major histocompatibility complex class I, CD86, and anti-LAG3 antibody (Figure 8E).The inner AIE-active photosensitizers provoked immunogenic cell death, thus activating dendritic cells and augmenting T lymphocyte infiltration through photodynamic therapy.This transformative process converted "cold tumors" into "hot tumors", significantly enhancing the efficacy of immunotherapy.The significance of this work lies in the establishment of a robust, photoactive, and artificial antigen-presenting platform.Furthermore, it not only activates native and fatigued T cells but also propels tumor photodynamic immunotherapy forward.
DC-derived small extracellular vesicles (DEVs) have gained considerable attention as a promising alternative to DC vaccines. [175][178] In this context, Wang et al. presented an uncomplicated strategy wherein DCs act as cellular reactors to exocytose highly efficient DEV-mimicking NPs with AIE properties (DEV-AIE NPs) on a larger scale. [179]he exocytosed DEV-AIE NPs not only inherited immunemodulatory proteins from their parent DCs, facilitating T cell activation, but also encapsulated the AIE PS MBPN-TCyP (Figure 8H).This combination resulted in an enhanced form of ICD by preferentially accumulating within the mitochondria of tumor cells.Consequently, the DEV-AIE synergistic photodynamic immunotherapy triggered substantial immune responses and effectively eliminated primary tumors, distant tumors, and tumor metastases.Additionally, the immunefunctional DEV-AIE NPs significantly impeded cancer stem cells (CSCs) within solid tumors of 4T1 and CT26.This study introduced a straightforward approach for generating EV-biomimetic NPs at a cellular level.Furthermore, it emphasized the effectiveness of combining DEVs and AIE photosensitizers as a robust avenue for producing clinical anticancer nanovaccines.
The limited lifespan of various ROS diminishes PDT effectiveness in therapy.The challenge is the enhancement and sustainability of ROS production within tumor cells.In 2022, Huang et al. developed a novel system inspired by tumor exosomes, named the tumor exosome bionic SAZs/AIEgens cascade catalysis system (CCS), to enhance the generation of hydroxyl radicals (•OH) and improve tumor penetration (Figure 8K). [180]The approach involved the creation of a Cu single-atom nanozyme (Cu SAZs) with peroxidase activity, followed by enveloping it with AIEgens-absorbed exosomes derived from tumors (TDE) to establish the CCS.This system, administered intravenously, infiltrated tumor tissue.Inside the tumor, the TBP-2 compound initiated the generation of

Triggering ICD with peptide-conjugated AIE nanoparticles
Peptide-based supramolecular structures have demonstrated considerable promise in the advancement of biological materials. [181]Typically, these materials are composed of multiple specialized units, united through either covalent or noncovalent interactions.The noncovalent interactions encompass hydrophobic and hydrogen bonding, - stacking, and electrostatic attractions.The meticulously designed peptide-based supramolecular assemblies with distinct configurations are of particular importance.These assemblies not only enhance the stability of enclosed substances but also preserve the versatile functionalities of the peptides. [182]heir functionalities encompass a broad spectrum of capabilities, including the ability to precisely target specific attributes, respond to external stimuli, penetrate cellular structures, inhibit receptors, and achieve controlled structural modifications. [183]Consequently, the amalgamation of AIEgen photosensitizers or sonosensitizers with PD-L1 peptide antagonists in the construction of AIE NPs introduces a dual-pronged approach, combining photo/sonodynamic therapy with ICB.
In response to the constraints posed by antibody-based ICB techniques that target PD-1/PD-L1 in cancer treatment, Fu et al. described an innovative solution (Figure 9B). [184]his approach aimed to enhance receptor binding affinity and optimize therapeutic results through the utilization of a novel hybrid supramolecular structure termed peptide-AIE hybrid supramolecular TAP.The TAP was designed to selfassemble into nanofibers through non-covalent interactions such as hydrogen bonds, resulting in a specific affinity to PD-L1 both in vitro and in vivo.Additionally, when combined with near-infrared agents, the TAP could be utilized (H) In vivo tumor inhibition in mice with BP-containing nanoparticles.Reproduced with permission. [190]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (I) Illustration depicting peptide conjugation as carriers for AIE therapeutic agents.(J) Presentation of the chemical structures of DPA-TPE-SCP, TPA-2 ph-SCP, and TPA-ph-SCP alongside a schematic representation of the peptide.(K) In vivo tumor inhibition in mice with AIE-containing nanoparticles.Reproduced with permission. [191]Copyright 2022, CCS Chemistry.(L) Presentation of the chemical structures of SP1, SP2, and SP3 alongside a schematic representation of the peptide.(M) Tumor inhibition effect of SP3 nanoparticles in vivo.Reproduced with permission. [192]Copyright 2022, Wiley-VCH Verlag GmbH & Co.
for tumor imaging and PTT.This facilitated the photothermal ablation of cancer cells, resulting in the generation of tumor-associated antigens (TAAs) and the initiation of a cascade of immunological responses.The reported research illustrated that synthetic self-assembled peptide nanofibers provided a compelling foundation for proactive photothermal immunotherapies against cancer.Through the combined improvement in receptor binding affinity with photothermal therapy and the initiation of immunological responses, the TAP was a potentially effective strategy to address the limitations of conventional ICB approaches.The study showed a novel and promising pathway for cancer immunother-apy, capitalizing on the benefits of self-assembled peptide nanofibers to enhance treatment outcomes.
The response rates of previous tumor immunotherapy strategies were relatively limited.Even in the case of the extensively examined ICB, the observed objective response rate (ORR) typically fell within the range from 10% to 30%. [185,186]To achieve a more promising response rate, Lou's research team designed a cascade amplification nanocomposite (Figure 9D). [187]The nanocomposite was constructed through the incorporation of two key components: the immune adjuvant polyinosinic:polycytidylic acid (Poly (I:C)) and a modular peptide modified with an AIEgen, referred to as PMRA.The PMRA composite consisted of distinct segments, each contributing to its overall functionality: the DPPA-1 peptide (P), which acted as an immune checkpoint inhibitor; the PLGLAG peptide (M), designed with a matrix metalloproteinase 2 (MMP-2) responsive sequence for the controlled release of DPPA-1; the RRRRRRRR peptide (R), functioning as a carrier for the Poly (I:C); and the PyTPA (A), a photosensitizer known for its AIE properties.Within the context of the cancer-immunity cycle, the PyTPA-initiated PDT played a pivotal role in inducing the liberation of TAAs, thereby priming T lymphocytes.The cytokines produced due to PDT and poly (I:C) administration further contributed to the activation of T lymphocytes.Meanwhile, the heightened presence of chemokines within the tumor microenvironment, when assisted by PDT, propelled the migration and infiltration of immune cells into the tumor site.At the culmination of this orchestrated sequence, the ICB featuring the DPPA-1 peptide enhanced the capacity of T lymphocytes to identify and eliminate tumor cells.It is worth noting that the induction of immunogenic cell death triggered the release of additional TAAs, thus perpetuating the cycle for subsequent rounds.By leveraging the entire cancer-immunity cycle, the cascade amplification nanocomposite achieved an impressive ORR of nearly 100% in vivo.This innovative approach, which utilized the full spectrum of the cancer-immunity cycle to enhance immunotherapy, represented a promising and novel direction for the advancement of tumor treatment.
Moreover, TNBC exhibits low susceptibility to targeted therapies due to the lack of viable molecular targets. [188]n encouraging approach for achieving optimal clinical outcomes entailed a strategy capable of inhibiting molecular signal transduction, boosting immunogenicity, and triggering the immune response.Therefore, in 2022, Ding's research group fabricated a self-assembling peptide fused with AIEgens, named TPA-FFG-LA (Figure 9E). [189]The main objective of this project was to develop a peptide with a specific affinity for the epidermal growth factor receptor (EGFR), a prominent characteristic of TNBC.TPA-FFG-LA peptides assembled into nanostructures on the surfaces of EGFR-positive TNBC cells and were subsequently internalized through endocytosis.This internalization not only interfered with EGFR signaling pathways but also triggered lysosomal membrane permeabilization (LMP).Upon exposure to light, the aggregated AIEgens generated a substantial amount of ROS, which further intensified LMP and initiated ICD.As a result, the process eliminated the remaining EGFR-negative tumor cells and established enduring antitumor effects.Validation through in vitro and in vivo experiments confirmed the effectiveness of TPA-FFG-LA nanoassemblies in curtailing tumor growth, activating immune cells and their infiltration into the tumor microenvironment, and promoting EGFR degradation and LMP.The reported findings indicated the potential of the combined strategy of supramolecular assemblyinduced molecular targeting with lysosome dysfunction, thus synergistically promoting ICD-induced immune activation.This comprehensive approach could effectively address the challenges presented by immunosuppressive TNBC.
To enhance the permeability and bioavailability of AIEgens for therapeutic applications, in 2023, Ren's research group synergized the principles of supramolecular chem-istry with the AIEgen bis-pyrene (BP), resulting in the development of a pioneering peptide-AIEgen hybrid nanosystem (PAHN) (Figure 9F). [190]When administered through intravenous injection, this versatile nanoplatform not only enhanced the hydrophilicity of BP but also enabled stratified targeting from the tumor to mitochondria, where it induced mitochondrial dysfunction and upregulated caspase-3.Subsequently, SDT was performed, showing high tissue penetrability to trigger the generation of ROS by BP.An essential feature of PAHN was the specific cleavage of caspase-3, which separated the hydrophilic shell from the nanosystem.This separation led to tight self-aggregation of PAHN residues in situ, allowing for greater utilization of the absorbed energy for ROS generation under ultrasound irradiation, thereby enhancing SDT efficacy.Moreover, the severe oxidative stress resulting from a ROS imbalance in the mitochondria initiated the immunogenic cell death process, inducing antitumor immunogenicity (Figure 9G).The developed PAHN has the potential for AIE-involved antitumor therapy and the design of peptide-AIEgen hybrids.This approach addresses the challenges of poor water solubility and limited treatment depth associated with AIEgens in PDT.
Simultaneously, another innovative approach, pioneered by Ding's research team in 2021, described the introduction of a novel AIE sonosensitizer featuring an intricately twisted molecular structure, an exceedingly small energy gap between singlet and triplet excited states (ΔE ST ), and a potent capability for ROS generation (Figure 9J). [191]The presented combination was a potent inducer of ICD for sonodynamic processes in the realm of cancer immunotherapy.In addition to the AIE sonosensitizer, the researchers constructed an AIE sonosensitizer-based nanosystem based on AIE sonosensitizer with surface modification using an anti-PD-L1 peptide to enhance antitumor immunotherapy.The nanosystem combined SDT, which converted a hypoimmunogenic cold tumor into a hot one, with ICB, involving the multivalent blocking of PD-L1 by anti-PD-L1 peptides.This advanced approach effectively initiated the activation of antitumoral immune reactions and modulated the immunosuppressive microenvironment, leading to systemic antitumor effects and the inhibition of distant tumor growth (Figure 9K).The study is a promising approach for cancer immunotherapy by utilizing AIE sonosensitizers and anti-PD-L1 peptide-based nanosystems.
Building upon the aforementioned research, Ding's research group achieved a breakthrough in 2023 by reporting a category of semiconducting polymer (SP) NPs known as SPSS NPs.(Figure 9L). [192]The SPs were synthesized to possess outstanding PDT properties through well-considered fluorination techniques, resulting in a significant induction of ICD.Furthermore, the addition of PD-L1 peptide antagonists led to their self-assembly into β-sheet protein secondary structures on the surface of the PDT NPs.These structures functioned as efficient lysosome-targeting chimeras (LYTACs), facilitating the degradation of PD-L1 in lysosomes.In vivo experiments demonstrated that SPSS NPs elicited strong antitumor immunity, effectively suppressing both primary and distant tumors.Furthermore, they induced long-term immunological memory against tumor rechallenge, indicating their potential for sustained effectiveness.The study highlighted a robust immunotherapy agent that  [204] Copyright 2023, American Chemical Society.(F) Presentation of the chemical structures of DP-PPh3 and TPE-PPh3.(G) Demonstration of tumor suppression in vivo by DP-PPh3 and TPE-PPh3.Reproduced under the terms of the Creative Commons Attribution 3.0 Generic License. [208]Copyright 2022, Royal Society of Chemistry.(H) Presentation of the chemical structures of TPAQ, TPAQ-H, TPAP, and TPAP-H.(I) Presentation of the chemical structure of TBVP.(J) Induction of autophagy-related protein expression by TBVP.(K) In vivo tumor inhibition in mice treated with TBVP.Reproduced with permission. [209]Copyright Elsevier.combined well-designed photosensitizer-based ICD induction with protein secondary structures-mediated LYTAC-like multivalence PD-L1 blockade.

TRIGGERING AUTOPHAGY WITH AIE THERAPEUTIC AGENTS
The term "autophagy" originated from the fusion of the Greek words "auto", meaning "self", and "phagein", denoting "to eat".[195] However, its true significance came to the forefront through pioneering investigations conducted by Japanese scientist Yoshinori Ohsumi during the 1990s, [196] ultimately earning him the prestigious 2016 Nobel Prize for his breakthroughs in unraveling the mechanisms underlying autophagy. [197]This intricate process encompasses two facets: basal autophagy, occurring during regular physiological states, and induced autophagy, which occurs under stress conditions. [198]Functioning as a double-edged sword, autophagy acts as a shield against cellular damage, facilitating survival in the face of nutrient scarcity and mounting a response to cytotoxic stimuli. [199]The former aspect embodies a cellular self-preservation mechanism.However, it is imperative to note that excessive autophagy can create metabolic strain, resulting in the degradation of cellular components and, in extreme instances, culminating in cell demise (Figure 10A).
For instance, the phenomenon of autophagy is pivotal in various contexts, such as during starvation-triggered protective autophagy, which promotes cell survival. [200]Conversely, for tumors, protective autophagy hinders the efficacy of starvation therapy, a potent broad-spectrum anti-tumor approach. [201,202]Tang group proposed a novel strategy for cancer treatment involving the integration of cancer starvation therapy with autophagy-activated fluorescent photosensitizers and PDT (Figure 10H). [203]This approach aimed to counteract cancer cells' protective autophagy mechanisms and amplify the therapeutic impact.Due to cancer cells' heightened energy requirements, targeting their energy supply is a feasible treatment avenue termed cancer starvation therapy.The photosensitizers used in this context generate ROS upon exposure to light.These photosensitizers (TPAQ and TPAP) are designed to activate within the autophagy process.Consequently, during protective autophagy, the molecules migrate to lysosomes (acidic organelles within cells) and generate ROS.The accumulation of ROS within the lysosomes triggered lysosomal membrane permeabilization, disrupting organelle integrity, and ultimately inducing cell apoptosis and promoting cell death.Notably, TPAQ and TPAP emitted fluorescence signals that changed color upon translocation to lysosomes and ROS generation.This alteration in fluorescence served as a real-time indicator of the autophagy process and ensuing cell death.The strategy's efficacy was validated using 3D tumor spheroids, which better emulated the intricacies of in vivo tumors compared to conventional 2D cell cultures.
Simultaneously, Zhang et al. introduced a groundbreaking cancer treatment method that marked a significant milestone (Figure 10C). [204]Their research revealed an innovative nano-medicine system known as (TP+A)@TkPEG NPs.This system was meticulously engineered to revolutionize the equilibrium of autophagy and enhance the therapeutic efficacy of PDT within the realm of TNBC treatment.The construction was comprised of three pivotal components: a ROS-responsive TK bond polymer carrier; a photosensitizer exhibiting AIE properties; and a hydrophobic autophagy regulator named triptolide (TP).Upon internalization, the system triggered a remarkable upsurge in intracellular ROS levels in the targeted cells, thereby initiating the ROS-responsive release of TP.Consequently, it effectively suppressed critical autophagy-related genes, including beclin-1 (an initiation gene) and light chain 3B (an elongation protein), within the tumor microenvironment.Notably, the nanosystem not only reinforced the therapeutic potency of PDT but also demonstrated an exceptional ability to selectively target tumor sites.The targeting capability was corroborated by its capacity to extend the survival duration of 4T1-bearing mice, highlighting its promising potential in the field of cancer treatment.
Currently, metallodrug is a common method for cancer treatment, but cancer cells generate metallodrug resistance and then reduce the efficacy of treatment with the specific drug. [205]Most mitochondrial targeting AIEgens retain the same anticancer mechanism with the cis-Pt, which both exhibit anticancer activity by inducing cell apoptosis. [206,207]n 2022, based on the cis-Pt anticancer mechanism, Su et al. proposed a novel way to solve cis-Pt resistance via mitochondrial dysfunction (Figure 10F). [208]They first synthesized two mitochondria-targeted AIEgens: DP-PPh 3 and TPE-PPh 3 , which showed high cytotoxicity to cis-Pt-resistant A549R cancer cells with IC 50 values of 1.25 and 3.60 μM, respectively.Moreover, DP-PPh 3 and TPE-PPh 3 could surmount the cis-Pt resistance observed in A549R cells by modifying the drug metabolism pathway (enhancing the expression of the influx transporter CTR1 and suppressing the efflux pump MRP2) and impeding the autophagic flux (resulting in the accumulation of undegraded autophagosomes).Additionally, in vivo studies revealed that DP-PPh 3 and TPE-PPh 3 exhibited potent anticancer efficacy while maintaining minimal systemic toxicity.The study elucidated a crucial mechanism through which AIE photodynamic therapy effectively counteracts drug resistance by modulating autophagy.
In 2023, Shen et al. chose BODIPY with remarkable spectral properties as the fluorophore parent nucleus and then utilized four different pyridine salt electron-receptor groups to complete chemical structure modification (Figure 10I). [209]etrapheny-lethylene (TPE) was added to induce the AIE effect, and four AIEgens were prepared: TBPy, TBPy-Bu, TBPy-TA, and TBVP.The report evaluated the ROS production ability of the four photosensitizers, which were better than the commercial photosensitizer Rose Bengal.They demonstrated through in vitro studies that TBPy targeted mitochondria, TBPy-Bu targeted lysosomes, TBPy-TA also targeted lysosomes, and TBVP targeted the cell membrane.Subsequently, Western blot analysis was employed to monitor the expression levels of autophagy-related proteins during TBVP and TBPy incubation.The augmentation in the autophagosome marker LC3-II (conversion from LC3-I to LC3-II) signified an elevation in autophagy levels (Figure 10J).Distinctively, TBVP showed prominent tumor suppression in in vivo studies of xenograft mouse models (Figure 10K).The research offered valuable insights into employing AIE photosensitizers in conjunction with autophagy for cancer therapy.

TRIGGERING FERROPTOSIS WITH AIE THERAPEUTIC AGENTS
Ferroptosis, a term introduced by Dixon et al. in 2012, [210] originates from the Greek words "ferro" (referring to ferrous ions) and "ptosis" (meaning falling).The term characterizes a mode of nonapoptotic programmed cell demise that relies on iron and results from an excessive accumulation of lipid peroxidation within cell membranes. [211]At the core of ferroptosis lies the disturbance of intracellular oxidative equilibrium, ultimately culminating in lipid peroxidation.By observing this phenomenon through a regulatory lens, ferroptosis pathways can be distinctly categorized into two types.The first type involves the reduction of intracellular antioxidant capacity, leading to the accumulation of ROS.The reduction primarily occurs through mechanisms such as the depletion of Glutathione and the inhibition of Glutathione peroxidase 4 (GPX4). [212]The second type involves the direct amplification of ROS production, thereby intensifying oxidative stress.This was caused by factors such as an excess of ferrous particles, the generation of ROS through PDT/SDT processes, and related mechanisms (Figure 11A). [213,214] I G U R E 1 1 (A) Illustration depicting the primary pathways of activating ferroptosis.(B) Presentation of the chemical structure of TCSVP.(C) TCSVP induces the expression of ferroptosis-related proteins and the content of markers.(D) TCSVP induces markers associated with ferroptosis.Reproduced with permission. [215]Copyright 2022, Springer Nature.(E) Schematic representation of a nanoparticle-coated AIE therapeutic agent.(F) Presentation of the chemical structure of TPEQM-DMA and schematic representation of the pathway by which TPEQM-DMA induces both apoptosis and ferroptosis.Reproduced with permission. [216]Copyright 2023, American Chemical Society.(G) Presentation of the chemical structure of PPR-2CN.(H) PPR-2CN NPs induce the expression of ferroptosis-related proteins.Reproduced with permission. [217]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (I) Presentation of the chemical structure of BOTTQ.(J) BOTTQ NPs induce the expression of ferroptosis-related proteins.Reproduced with permission. [218]Copyright 2023, Elsevier.(K) Presentation of the chemical structure of TBTP-Au.(L) Schematic representation of the pathway of ferroptosis induced by TBTP-Au NPs.Reproduced with permission. [221]opyright 2023, Wiley-VCH Verlag GmbH & Co.
Ferroptosis inducers have been explored for their potential to promote cell death in tumor cells, exerting an anti-tumor effect.However, the specificity and effectiveness of such ferroptosis inducers are somewhat lacking.In this context, a novel mitochondria-targeted PS with AIE properties, named TCSVP, was designed by the Tang group (Figure 11B). [215]CSVP efficiently generates ROS within mitochondria upon exposure to light.The administration of TCSVP significantly sensitized tumor cells to ferroptosis induction mediated by RSL3, with a specific and light-dependent triggering of moderate ROS production, both in vitro and in vivo.Mechanistically, the expression levels of proteins associated with ferroptosis, including GPX4, were coupled with a decrease in GPX4 activity and an excess accumulation of malondialdehyde (MDA).(Figure11C).The reported study highlighted that the light-induced, moderate ROS generation within the mitochondria of cancer cells by AIE-PS could be harnessed to enhance the specificity and efficacy of ferroptosis inducers, introducing a novel synergistic strategy for intervening in tumor growth.
In 2023, Zhuang et al. presented a novel AIEgens PS called TPEQM-DMA that operates in the NIR-II range, addressing the limitations of PDT in treating hypoxic tumors (Figure 11F). [216]TPEQM-DMA exhibited remarkable NIR-II emission (beyond 1000 nm) with an emission-enhancing property triggered by aggregation.It efficiently generated superoxide anions and •OH in an aggregated state, particularly in the presence of white light and low oxygen levels.The positively charged nature of TPEQM-DMA facilitated its accumulation within cancerous mitochondria.Consequently, PDT involving TPEQM-DMA disrupted the cellular redox balance, induced mitochondrial dysfunction, and elevated the levels of peroxidized lipids, ultimately leading to cellular apoptosis and ferroptosis.This combined mode of cell death enabled TPEQM-DMA to effectively inhibit the growth of cancer cells, multicellular tumor spheroids, and tumors.To enhance the pharmacological characteristics of TPEQM-DMA, researchers developed TPEQM-DMA NPs through their encapsulation in a polymer matrix.In vivo experiments confirmed the promising potential of the NPs in NIR-II fluorescence-guided PDT for tumor treatment.
During the same period, Fang et al. brilliantly conceptualized and synthesized a diverse range of intricately designed organic PSs, characterized by their donor-acceptor (D-A) structures (Figure 11G). [217]Among these compounds, PPR-2CN displayed exceptional attributes, which included stable NIR-I emission, an outstanding capacity for generating free radicals, and potent phototoxicity.Through experimental analysis and computational simulations, they showed that two key factors, a small singlet-triplet energy gap (ΔE ST ) and a significant spin-orbit coupling (SOC) constant, played pivotal roles in enhancing ISC.Moreover, PPR-2CN possessed distinct capabilities for depleting intracellular glutamate (Glu) and glutathione (GSH), thus hindering the biosynthesis of GSH within cells.This disruption led to a state of redox dyshomeostasis and GSH depletion, ultimately triggering ferroptosis (Figure 11H).This pioneering work represents an important milestone, demonstrating the adept utilization of a single-component organic PS as both a type-I photodynamic agent and a metal-free ferroptosis inducer.
The simultaneous overcoming of tumor hypoxia while promoting ferroptosis is a daunting task.In pursuit of this goal, Xue et al. synthesized a photosensitizer known as BOTTQ, designed to specifically target lipid droplets (LD), achieved by extending the tail chain of triphenylamine (Figure 11I). [218]Incorporating alkoxy chains optimized the molecular structure of BOTTQ, boosting intersystem crossing and fostering the generation of type I ROS under light excitation.BOTTQ proved highly efficient at oxidizing polyunsaturated fatty acids in the lipid monolayer of LD, contributing to the creation of ferroptosis substrates.Additionally, the substantial production of type I ROS accelerated the Fenton reaction, effectively promoting ferroptosis.Moreover, the encapsulation of BOTTQ within DSPE-PEGMAL material not only enhanced the stability of NP colloids but also, in a mild environment, the MAL component facilitated the depletion of GSH.This depletion led to glutathione failure, further fostering ferroptosis (Figure 11J).Consequently, this tumor-specific ferroptosis-inducing strategy presents a universally applicable therapeutic approach with the ability to enhance type I ROS production and effectively counteract tumorigenesis.
NIR-II ferroptosis activators hold tremendous promise for in vivo theranostics of deep-seated tumors such as gliomas.However, the majority of these activators are non-visual ironbased systems, making them unsuitable for precise in vivo studies. [219]Furthermore, the use of an iron species in these systems may lead to unintended adverse effects on normal cells. [220]By considering that gold (Au) is an essential cofactor for life and can selectively bind to tumor cells, Tang group developed Au(I)-based NIR-II ferroptosis NPs known as TBTP-Au NPs, designed specifically for brain-targeted orthotopic glioblastoma theranostics (Figure 11K). [221]This pioneering system enabled real-time visual monitoring of both blood-brain barrier (BBB) penetration and the targeting of glioblastoma processes.Moreover, the system established that the released TBTP-Au selectively activated the efficient heme oxygenase-1-regulated ferroptosis of glioma cells, significantly extending the survival time of mice bearing gliomas (Figure 11L).This novel ferroptosis mechanism, relying on Au(I), may pave the way for the development of advanced and highly specific visual anticancer drugs suitable for clinical trials.
In addition, Wang et al. described a newly developed molecule operating in the NIR-II range (Figure 12B), [222] which possessed a property known as AIE and was named TSST.Researchers strategically designed and synthesized NPs named DFT-NP, where TSST was co-assembled with DHA-PEG and ferrocene.The NPs exhibited various improved capabilities, including enhanced NIR-II fluorescence, photothermal effects, photoacoustic signals, magnetic resonance imaging, AIE attributes, and the ability to induce ferroptosis.The heightened NIR-II fluorescence intensity observed in the resulting NPs was attributed to the strong interaction between DHA and TSST.The observed interaction minimized intramolecular rotation constraints and non-radiative energy losses of TSST, thereby preventing energy dissipation in its aggregated state.Impressively, the photothermal effect triggered by DFT-NP promoted the Fenton reaction involving ferrocene and H 2 O 2 , resulting in NP dissolution and accelerated ferroptosis in cancer cells.This was achieved through the accumulation of lipid free radicals from DHA.Furthermore, the released TSST enhanced the effects of photothermal and photoacoustic imaging by eliminating the constraints imposed by DHA, thus restoring the non-radiative energy loss processes.The study innovatively combined four-mode imaging, photothermal responses, and ferroptosis-inducing therapeutic functions within NPs.
Tang group presented a novel approach to improve the efficiency of oxygen-dependent PDT for cancer treatment in hypoxic tumor microenvironments (TME) (Figure 12D). [223]he researchers developed a bonsai-inspired oxygen selfsufficient photodynamic cancer therapeutic system using an AIEgen PS and a vermiculite nanohybrid.This nanohybrid was created by loading the AIEgen photosensitizer (DCPy) onto ultrathin nanosheets (NSs) derived from vermiculite through lithium-ion intercalation and was referred to as NSs@DCPy.It demonstrated the capacity to generate 1 O 2 and •OH upon exposure to white light radiation.Furthermore, it could catalyze H 2 O 2 to produce oxygen (O 2 ), which significantly enhanced PDT efficacy by alleviating tumor hypoxia.Alongside its PDT capabilities, the NSs@DCPy nanohybrid induced ferroptosis in the tumor by promoting iron overload and depleting GSH (Figure 12E).The integration of PDT  [222] Copyright 2022, Elsevier.(D) Presentation of the chemical structure of DCPy and a simple schematic illustrating its loading onto a nanosheet.(E) NPs@DCPy induce the expression of ferroptosis-related proteins.(F) In vivo tumor inhibition in mice treated with NPs@DCPy.Reproduced with permission. [223]Copyright 2022, Elsevier.and ferroptosis in the nanohybrid allowed for oxygen selfsufficiency and improved therapeutic outcomes, offering a potential solution for effective photodynamic cancer therapy in challenging TME conditions.

Triggering cuproptosis with AIE therapeutic agents
In 2022, a groundbreaking discovery was made by a team led by Peter Tsvetkov and Todd R. Golub.They identified a new form of cell death, which was named cuproptosis to distinguish it from previously known cell death mechanisms. [224]uproptosis's pivotal process relied on the buildup of intracellular copper ions.These ions directly interacted with the fatty acylation components of the tricarboxylic acid cycle (TCA), leading to the aggregation and disruption of the proteins. [224]This, in turn, obstructed the TCA cycle, initiated proteotoxic stress, and ultimately triggered the demise of the cell.Additionally, the research team uncovered that Ferredoxin 1 (FDX1) played a crucial role as a regulator in the realm of copper-induced mortality. [224]uproptosis holds great promise in the field of tumor therapy, yet its effectiveness is often hindered by the copper efflux mechanism and the presence of highly expressed intracellular reducing agents. [225]In 2023, Tang group tackled the aforementioned obstacles (Figure 13A). [226]Their endeavor created an innovative platform, named platelet vesicle (PV)coated cuprous oxide NPs (Cu 2 O)/TBP-2 for cuproptosis sensitization (PTC), which enabled the multipronged induction of tumor cuproptosis.To create PTC, a physical extrusion technique was employed to combine an AIE photosensitizer called TBP-2 with Cu 2 O and PV.This biomimetic modification conferred PTC with extended circulation in the bloodstream and enhanced its ability to target tumor cells.Subsequently, when exposed to an acidic environment within tumor cells, PTC underwent rapid degradation, releasing copper ions and hydrogen peroxide.Upon exposure to light, TBP-2 swiftly infiltrated the cell membrane, initiating the generation of hydroxyl radicals.These radicals effectively depleted intracellular glutathione levels and suppressed copper efflux (Figure 13B).The accumulation of copper led to the aggregation of lipoylated proteins and the loss of ironsulfur proteins, inducing proteotoxic stress and ultimately triggering cuproptosis.In both in vitro and in vivo settings, PTC treatment exhibited the capacity to selectively target and induce cuproptosis in tumor cells.This approach significantly inhibited the metastasis of breast cancer to the lungs, boosted the population of central memory T cells in peripheral blood, and provided protection against tumor rechallenge.These findings pave the way for the design of nanomedicine strategies centered around the concept of cuproptosis.

Triggering necroptosis with AIE therapeutic agents
Necroptosis, often recognized as programmed necrotic cell death, represents a unique mode of cellular demise orchestrated by the coordinated actions of RIP1 and RIP3 kinases. [226]This distinctive pathway is characterized by the swift disintegration of the cell's cytoplasmic membrane, resulting in the release of cellular contents and the swelling of organelles.In contrast to apoptosis, a highly regulated process featuring distinctive markers such as intact cell membranes, condensed chromatin, and fragmented nuclear DNA, necroptotic cell death deviates from these conventional apoptotic characteristics. [227]Traditionally, when conventional photosensitizers are directed toward lysosomes or mitochondria, they tend to induce cell apoptosis, a process in which immediate and conspicuous DNA damage is not typically observed. [155]In an innovative approach, Tang group explored photosensitizers targeting the cell membrane (Figure 13C). [228]This involved the molecular design Illustration depicting the pathways of activating cuproptosis.Reproduced with permission. [226]Copyright 2023, American Chemical Society.(C) Presentation of the chemical structure of TBMPEI.(D) Measurement of TBMPEI-induced necroptosis using flow cytometry.(E) Visualization of the morphology of necrotizing apoptotic cells induced by TBMPEI.(F) Demonstrated in vivo tumor inhibition in mice treated with TBMPEI dots.Reproduced with permission. [228]opyright 2022, Royal Society of Chemistry.
incorporating three essential elements: rotatable units, a robust donor-acceptor (D-A) structure, and positive charges.These components met the requirements of AIE, photosensitizing capability, and membrane affinity, leading to the creation of a pyridine salt known as TBMPEI.This specialized compound not only featured an extensive absorption spectrum but also outperformed conventional photosensitizers in terms of ROS generation.Importantly, TBMPEI selectively accumulated on the cell membrane and, upon exposure to light, induced cell necroptosis, characterized by membrane rupture and DNA degradation (Figure 13D,E).In contrast to the control group, the combination of TBM-PEI and light exhibited a remarkable capacity to effectively suppress tumor growth (Figure 13F).In vivo evaluations revealed the potential of TBMPEI as an outstanding candidate for fluorescence imaging-guided PDT, marking a significant advancement in the field of cancer treatment.

CONCLUSIONS AND OUTLOOK
This comprehensive review aims to synthesize the extensive research conducted in the last 2 years concerning AIE therapeutic agents.Specifically, the focus is on their activation through light or ultrasound, either as inducers of RCD or in synergy with RCD inducers.In the context of cancer therapy, a diverse array of AIE therapeutic agents has been investigated for their capacity to induce RCD or collaborate with RCD inducers, spanning various forms of cell death, including apoptosis, pyroptosis, ICD, autophagy, fer-roptosis, cuproptosis, and necroptosis.These agents activate RCD pathways independently or synergistically through the generation of ROS or thermal effects under physical stimuli such as light or ultrasound, presenting a promising avenue for anticancer treatment.The modulation of classical apoptotic pathways by ROS or thermal effects generated by AIE therapeutic agents not only effectively combats chemoresistance induced by conventional chemotherapy drugs but also enhances treatment outcomes for chemotherapy-resistant tumors.Achieving a delicate balance between autophagy-induced cell death and protective autophagy harnesses the cellular autophagic mechanism for effective cancer treatment.Particularly noteworthy is the stimulation and regulation of the ICD process by AIE therapeutic agents, demonstrating the potential to eliminate pre-existing tumors while fortifying tumor resistance through immune system activation.Moreover, the release of inflammatory factors during pyroptosis and necroptosis underscores their integral role in immunotherapy, adding a layer of complexity to the exploration of these pathways.As emerging pathways like ferroptosis and cuproptosis intertwine with biological REDOX processes, closely associated with PDT or SDT, they represent the next frontiers in research.
Looking ahead, emerging pathways like ferroptosis and cuproptosis, intricately linked with biological REDOX processes and associated with PDT or SDT, beckon as the next frontiers in research.As we stand on the precipice of a new era in cancer treatment, the exploration of AIE therapeutic agents, either independently or in synergy with RCD inducers, promises to be an increasingly captivating field.The unfolding complexities of RCD pathways and their interactions with AIE agents through photodynamic, sonodynamic, and photothermal pathways open avenues for extensive exploration and innovation.Researchers are poised to play a pivotal role in unraveling these intricate mechanisms, offering hope for the development of advanced AIE therapeutic agents that could revolutionize cancer treatment paradigms.
In conclusion, this review provides an encompassing perspective on the activation of AIE therapeutic agents in inducing RCD and their potential synergy with RCD inducers.The anticipation is that this exploration will stimulate growing interest in the investigation of AIE therapeutic agents, either acting independently or in tandem with RCD inducers.As we foresee an expanding phase in this field, researchers are encouraged to delve deeper into the intricate regulatory mechanisms governing the interaction of AIE therapeutic agents with RCD pathways through photodynamic, sonodynamic, and photothermal pathways.It is our hope that the insights shared here will serve as inspiration for researchers, fostering contributions to the development of activated AIE therapeutic agents for RCD induction and furthering the understanding of these complex regulatory mechanisms.

C O N F L I C T O F I N T E R E S T S TAT E M E N T
The authors declare no conflicts of interest.

R E F E R E N C E S
(B) The straightforward process of inducing apoptosis through therapeutic agents.(C) The straightforward process of inducing pyroptosis through therapeutic agents.(D) The straightforward process of inducing ICD through therapeutic agents.(E) The straightforward process of inducing ferroptosis through therapeutic agents.(F) The straightforward process of inducing cuproptosis through therapeutic agents.(G) The straightforward process of inducing autophagy through therapeutic agents.

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I G U R E 5 (A) The schematic diagram delineates the principal pathways of ROS-induced pyroptosis.(B) Chemical structures of TBD-1C, TBD-2C, and TBD-2C are provided.(C) The chemical structure of TPA-2TIN is outlined, showcasing its ability to induce the expression of pyroptosis-related proteins.

F I G U R E 6
Illustration depicting immunogenic cell deaths (ICDs) within tumor cells induced by AIE diagnostic and therapeutic agents.(Tumor and cell models) Reproduced under the terms of a Creative Commons Attribution 3.0 Generic License from Servier Medical Art (http://smart.servier.com/).molecule-based photoactivators targeting the STING pathway.The activation of cGAS-STING in conjunction with the induction of pyroptosis has the potential for the development of novel anticancer immunotherapy agents.

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I G U R E 7 (A) Illustration depicting a nanoparticle-coated AIE therapeutic agent.(B) Presentation of the chemical structure of AIE1.(C) Depiction of the chemical structures of RC-DTE-DPA-SCP and RO-DTE-DPA-SCP.(D) Display of the chemical structure of TPA-Erdn and its self-assembly into nanoparticles.Reproduced with permission. [144]Copyright 2023, Wiley-VCH Verlag GmbH & Co. (E) Schematic representation of a nanoparticle-coated AIE therapeutic agent and drug.(F) Presentation of the chemical structures of TST, AZD4635, and CPT-S-PEG.(G) Display of the chemical structures of T-TBBTD and

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I G U R E 8 (A) Illustration depicting a cell membrane-coated nanoparticle serving as carriers for AIE therapeutic agents.(B) Presentation of the chemical structure of BITT.(C) Display of the chemical structure of BPBBT.(D) Presentation of the chemical structure of TTPA.(E) Schematic diagram outlining the preparation process of saDC@Fs-NPs.Reproduced with permission. [174]Copyright 2022, Wiley-VCH Verlag GmbH & Co. (F) Presentation of the chemical structure of Fs. (G) Illustration depicting a cell membrane-coated nanoparticle as carriers for AIE therapeutic agents.(H) Presentation of the chemical structure of MBPN-TcyP.(I) Demonstration of the tumor inhibition effect of DEV-AIE nanoparticles in vivo.Reproduced with permission.

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I G U R E 9 (A) Illustration depicting AIE therapeutic drugs covalently coupled to peptides and self-assembled into nanoparticles.(B) Presentation of the chemical structure of TPE alongside a schematic representation of the peptide.(C) Display of the chemical structure of TPE alongside a schematic representation of the peptide.Reproduced with permission. [184]Copyright 2022, Springer.(D) Presentation of the chemical structure of PyTPA alongside a schematic representation of the peptide.(E) Presentation of the chemical structure of TPA-S-RDN alongside a schematic representation of the peptide.(F) Presentation of the chemical structure of BP alongside a schematic representation of the peptide.(G) Activation of tumor T cells by BP-containing nanoparticles.

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I G U R E 1 0 (A) Illustration depicting the primary pathways of activating autophagy.(B) Schematic representation of a nanoparticle-coated AIE therapeutic agent and drug.(C) Presentation of the chemical structures of AIE and Triptolide.(D) Depiction of autophagy activation pathways.(E) AIE NPs inducing autophagy-related protein expression and tumor suppression in vivo.Reproduced with permission.

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I G U R E 1 2 (A) Schematic representation of nanoparticle-coated AIE therapeutic agents and drugs.(B) Presentation of the chemical structure of TSST.(C) Demonstrated in vivo tumor inhibition in mice treated with TSST-NF NPs.Reproduced with permission.

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I G U R E 1 3 (A) Presentation of the chemical structure of TBP-2 and schematic representation of a nanoparticle-coated AIE therapeutic agent.(B) This work was financially supported by the National Natural Science Foundation of China (No. 22067019, 22367023), Yunnan Provincial Science and Technology Department-Yunnan University Joint Special Project (No. 202201BF070001-001), the Postgraduate Research Innovation Foundation of Yunnan University (KC-22222295), the National Research Foundation of Korea (CRI project no.2018R1A3B1052702, J.S.K).L. Yu thanks the China Scholarship Council (CSC, No. 201907030009).
•OH and H 2 O 2 through type-1 PDT.Subsequently, H 2 O 2 interacted with the Cu SAZs, triggering the production of •OH within the tumor.Experiments conducted on the SGC-7901 tumor model revealed that CCS effectively curtailed tumor growth and induced tumor ICD with notable efficiency.The CCS system promoted augmentation and consistent •OH generation, compensating for H 2 O 2 deficiency in SAZ-catalyzed therapy.Importantly, the findings of this study demonstrated that CCS effectively suppressed tumor recurrence in a recurrent mouse tumor model (CT26) following surgery.