Efficient NIR-II Type-I AIE Photosensitizer for Mitochondria-Targeted Photodynamic Therapy through Synergistic Apoptosis-Ferroptosis

Molecular engineering strategies for fabricating type-I mitochondria-targeted aggregation-induced emission photosensitizers for apoptosis-ferroptosis synergistically boosting photodynamic therapy

The precise distribution and subcellular localization of photosensitizers (PSs) play a crucial role in maximizing the utilization of reactive oxygen species (ROS) and enhancing photodynamic therapy (PDT). However, the therapeutic efficacy of PDT is significantly compromised by the hypoxic microenvironment, particularly in malignant tumors. To address these challenges, we designed and synthesized three donor-donor-π-bridge-acceptor (D-D-π-A) type aggregation-induced emission (AIE) PSs: TCM-OTs, TCM-OH, and TCPy-OH. By fine-tuning the acceptor and donor substituents, we successfully modulated organelle-targeting specificity and ROS generation to mitigate hypoxia-related limitations. Among these compounds, TCM-OH emerged as a highly promising PS, exhibiting selective mitochondrial targeting and efficient type-I ROS generation. To further enhance its pharmacological properties, we encapsulated each PS into DSPE-PEG2k to form nanoparticles (NPs). Notably, TCM-OH NPs facilitated the production of superoxide (•O2-) and hydroxyl radicals (•OH) within mitochondria, leading to mitochondrial dysfunction and subsequent cell death via a synergistic ferroptosis-apoptosis pathway under light irradiation. Both in vitro and in vivo experiments demonstrated the potent therapeutic efficacy of this strategy, with minimal toxicity, underscoring its potential for hypoxic cancer treatment. Overall, this study provides a rational design framework for developing potent type-I PSs with multimodal capabilities for biomedical applications.

Regulated cell death mechanisms in mitochondria-targeted phototherapy

Phototherapy, comprising photodynamic therapy (PDT) and photothermal therapy (PTT), was first introduced over a century ago and has since evolved into a versatile cancer treatment modality. While numerous studies have explored regulated cell death (RCD) mechanisms induced by phototherapy, a comprehensive synthesis centered on mitochondria-targeted phototherapeutic strategies and agents as mediators of RCD is still lacking. This review provides a systematic and in-depth analysis of recent advances in mitochondria-centered mechanisms driving phototherapy-induced death pathways, including apoptosis, autophagy, pyroptosis, immunogenic cell death, ferroptosis, and cuproptosis. We highlight the critical role of mitochondria as central regulators of these death pathways in response to phototherapeutic interventions. Moreover, we discuss fundamental design strategies for developing precision-targeted phototherapeutic materials to enhance efficacy and minimize off-target effects. Finally, we identify prevailing challenges and propose future research directions to address these hurdles, paving the way for next-generation mitochondria-targeted phototherapy as a highly effective strategy for cancer management.

Antitumour and anti-angiogenesis efficacy of a multifunctional self-oxygenated active-targeting drug delivery system by encapsulating biological and chemotherapeutic drugs

The hypoxic tumour microenvironment (TME), resulting from abnormal tumour angiogenesis, is a major factor contributing to treatment failure in breast cancer patients. In this study, we present a ZnO2-based oestrone-conjugated PEGylated liposome (ZnO2@EPL-CDDP/EGCG) that incorporates cisplatin (CDDP) and epigallocatechin-3-gallate (EGCG). ZnO2 remains stable in neutral environments but decomposes under mildly acidic conditions, releasing Zn²⁺ and H₂O₂. These byproducts inhibit the electron transport chain, stimulate the endogenous reactive oxygen species production for chemodynamic therapy (CDT), and generate oxygen at tumour sites to alleviate hypoxia and enhance anti-angiogenic efficacy. EGCG inhibits tumour angiogenesis by down-regulating hypoxia-inducible factor-1α (HIF-1α) and its downstream pathways, while also exhibiting synergistic anti-tumour effects with CDDP. Oestrone-conjugated and polyethylene glycol (PEG) modifications facilitate targeted accumulation at tumour sites. Our findings indicate that ZnO2@EPL-CDDP/EGCG significantly improves the therapeutic efficacy of both EGCG and CDDP, remodels tumour vasculature, and alleviates hypoxia within the TME. This self-oxygenated, actively targeted drug delivery system notably extends the survival of healthy ICR mice without observed toxicity. This novel approach, which co-encapsulates ZnO2, EGCG, and CDDP in an active-targeting liposomal formulation for the first time, represents a promising strategy for effective cancer treatment.

Enhanced Intracellular IR780 Delivery by Acidity-Triggered PEG-Detachable Hybrid Nanoparticles to Augment Photodynamic and Photothermal Combination Therapy for Melanoma Treatment

The PEGylation of drug-carrying nanoparticles has often been used to prolong blood circulation and improve drug deposition at tumor sites. Nevertheless, the PEG-rich hydrophilic surfaces retard the release of the payloads and internalization of therapeutic nanoparticles by cancer cells, thus lowering the anticancer efficacy. To boost the anticancer potency of the combined photodynamic therapy (PDT) and photothermal therapy (PTT) against melanoma by conquering the PEG dilemma, herein, the hybrid PEGylated chitosan-covered polydopamine (PDA) nanoparticles (PCPNs) with acidity-elicited PEG detachment ability were fabricated as carriers of IR780, a small-molecule photosensitizer used for PTT and PDT. The IR780@PCPNs displayed a uniform, solid-like spherical shape and sound colloidal stability. Under near-infrared (NIR) irradiation, the IR780@PCPNs showed prominent photothermal conversion efficiency (ca. 54.6%), robust photothermal stability, reduced IR780 photobleaching, sufficient singlet oxygen (1O2) production, and glutathione-depleting ability. Moreover, with the environmental pH being reduced from 7.4 to 5.0 at 37 °C, the decreased interactions between IR780 and PCPNs due to the increased protonation of phenolic hydroxyl residues within PDA and primary amine groups of chitosan accelerated the release of IR780 species from IR780@PCPNs. Importantly, the cellular uptake of IR780@PCPNs by B16F10 melanoma was remarkably promoted in a weakly acidic milieu upon PEG detachment driven by the disintegration of acid-labile benzoic imine. With NIR irradiation, the internalized IR780@PCPNs generated hyperthermia and 1O2 to damage mitochondria, thereby effectively inhibiting the proliferation of B16F10 cells. Collectively, our findings present a practical strategy for amplifying the anticancer efficacy of PTT combined with PDT using PEG-detachable IR780@PCPNs.

Organelle-targeted small molecular photosensitizers for enhanced photodynamic therapy: a minireview for recent advances and potential applications

Photodynamic therapy (PDT) is a promising approach for cancer treatment that involves the use of photosensitizers to generate reactive oxygen species upon light irradiation, resulting in selective cytotoxicity. To enhance the efficiency of PDT, researchers have developed organelle-targeting photosensitizers that specifically accumulate in critical cellular organelles. This review provides a comprehensive overview of recent advancements in the development of organelle-targeting photosensitizers for PDT. Different organelles, including mitochondria, plasma membrane, lysosome, endoplasmic reticulum, lipid droplets, nucleus, and Golgi, have been targeted to improve the selectivity and effectiveness of PDT. Various strategies have been employed to design and synthesize these photosensitizers, optimizing their organelle-specific accumulation and photodynamic efficiency. This review discusses the principles and mechanisms underlying the design of organelle-targeting photosensitizers, along with their exceptional results achieved in preclinical studies. Furthermore, potential applications and challenges in the development of multi-organelles-targeting photosensitizers and the synergistic use of multiple photosensitizers targeting different organelles are highlighted. Overall, organelle-targeting photosensitizers offer a promising avenue for advancing the field of PDT and improving its clinical applicability.

Photothermal-enhanced ROS storm by hyaluronic acid-conjugated nanocatalysts to amplify tumor-specific photo-chemodynamic therapy and immune response

Integrating photodynamic therapy (PDT) and chemodynamic therapy (CDT) shows promising potential in tumor treatment. Nevertheless, the lack of specific tumor targeting, serious photobleaching, and poor photothermal effect of photosensitizers, the intracellular low Fenton reaction efficiency, and glutathione (GSH)-elicited reactive oxygen species (ROS) depletion profoundly restrict ROS-mediated cancer therapy. To enhance ROS generation with the assistance of photothermal therapy (PTT), the hyaluronic acid (HA)-decorated Fe-MIL-88B (MIL) nanocatalysts were fabricated for tumor-targeted delivery of photosensitizer IR820. The IR820@HA-coated MIL (IHM) nanocatalysts remarkably enhanced the photothermal conversion efficacy and singlet oxygen (1O2) production of IR820 and lowered IR820 photobleaching. The IHM nanocatalysts promoted the conversion of H2O2 into toxic ·OH upon thermo/acidity-enhanced Fe3+-mediated Fenton reaction and consumed GSH via Fe3+-elicited GSH oxidation. After being internalized by 4 T1 cancer cells via CD44-mediated endocytosis, the IHM nanocatalysts under irradiation of near-infrared (NIR) laser prominently produced hyperthermia and strong ROS storm, thereby causing apoptosis and ferroptosis via mitochondria damage and lipid peroxidation, and inducing immunogenic cell death (ICD). Through HA-mediated tumor targeting, the IHM nanocatalysts effectively accumulated in 4 T1 tumor and inhibited tumor growth and lung metastasis by PTT-enhanced PDT/CDT combined with ferroptosis and ICD-amplified antitumor immune response, showing great promise in future tumor treatment.

Improved Orthogonality in Naphthalimide/Cyanine Dyad Boosts Superoxide Generation: a Tumor-Targeted Type-I Photosensitizer for Photodynamic Therapy of Tumor by Inducing Ferroptosis

It is highly desired to achieve Type-I photosensitizer (PS) to overcome the hypoxic limitation found in most clinically used PSs. Herein, a new heavy-atom-free Type-I PS T-BNCy5 is presented by incorporating a biotin-modified naphthalimide (NI) unit into the meso-position of a N-benzyl-functionalized, strongly photon-capturing pentamethine cyanine (Cy5) dye. Such molecular engineering induces a rigid orthogonal geometry between NI and Cy5 units by introducing an intramolecular sandwich-like π-π stacking assembly, which effectively promotes intersystem crossing (ISC) and greatly extends the triplet-state lifetime (τ = 389 µs), thereby markedly improving the superoxide (O2 •-)-generating ability. In vitro assays reveal that T-BNCy5 specifically accumulates in mitochondria, where it not only generates O2 •- under photoirradiation but also induces the burst of the most cytotoxic hydroxy radical (HO•) by a cascade of biochemical reactions, ultimately triggering cell ferroptosis with the IC50 value up to ≈0.45 µm whether under normoxia or hypoxia. In vivo assays manifest that, benefiting from its biotin unit, T-BNCy5 displays a strong tumor-targeting ability, and after a single PDT treatment, it can not only ablate the tumor almost completely but also be cleared from the body through biosafe urinary excretion, indicating its potential for future clinical translation.

Recent Progress of Molecular Design in Organic Type I Photosensitizers

Photodynamic therapy (PDT) represents a high-efficient and non-invasive therapeutic modality for current and future tumor treatments, drawing extensive attention in the fields of antitumor drug and clinical phototherapy. In recent years, the photosensitizer (PS) market and PDT clinical applications have expanded to address various cancers and skin diseases. However, hypoxic environment within tumors poses a substantial challenge to the therapeutic capability of reactive oxygen species-dependent PDT. Consequently, researches have increasingly focus from the type II to type I PDT mechanism, which relies on radical production with less or no oxygen dependence. Despite significant progress in the development of type I PSs, a holistic understanding regarding the design principles for these molecules remains elusive. Specifically, electron transfer-mediated type I PDT are extensively studied in recent years but is insufficiently addressed in existing reviews. This review systematically summarizes recent advancements in the molecular design rationales of organic type I PSs, categorizing them into three key fundamental strategies: modulating PS charge distribution, singlet oxygen forbidden via low triplet excited state, and accelerating PS radical formation via inducing electron transfer. This review aims to offer valuable insights for the future type I PS design and the advancement of anti-hypoxia PDT.

Targeting matrix metalloproteinases activating and indoleamine 2,3-dioxygenase suppression for triple-negative breast cancer multimodal therapy

The dense extracellular matrix (ECM) and immunosuppressive tumor microenvironment represent two major challenges in the treatment of triple-negative breast cancer (TNBC). To address these obstacles, this study has developed a polymer micelle (NTP) for ECM remodeling and mitigation the immune microenvironment, based on activating endogenous matrix metalloproteinases (MMP) and suppression indoleamine 2,3-dioxygenase (IDO). Through self-assembly technology, this micelle effectively incorporates chemotherapy drugs (camptothecin (CPT) and cinnamaldehyde (CA)), reactive oxygen species (ROS) stimulants, nitric oxide (NO) donor and IDO inhibitor (NLG919), where CPT and CA have been reported to help generating ROS mainly in the mitochondrion. The guanidine group of poly-L-arginine (PArg), as an NO donor, can react with ROS to generate NO. The micelles aim to achieve significant therapeutic outcomes through robust drug penetration and anti-tumor immunity in multimodal therapy. They exhibit remarkable tumor tissue penetration ability, facilitating precise targeting of mitochondria and ROS production stimulation. Building upon this therapeutic foundation, the micellar system achieves in situ NO release, which effectively degrades the ECM through the activation of MMPs, while simultaneously promoting tumor cells apoptosis. Furthermore, the encapsulated NLG919 can be released and effectively mitigating the immunosuppressive milieu and triggering anti-tumor immune responses. Experimental results demonstrate that the micelles exhibit significant anti-tumor effects both in vitro and in vivo, accompanied by favorable biocompatibility. This study provides new insights into the application of subcellular targeting drug delivery systems in TNBC treatment, potentially heralding a new breakthrough in TNBC therapy.

A Mitochondrion-Targeted NIR-II Modulator for Synergistic Ferroptosis-Immunotherapy

Immune checkpoint inhibitors (ICIs) have limited clinical efficacy against gastric cancer (GC) due to the nonimmunogenic tumor microenvironment. Therefore, inducing immunogenic cell death (ICD) to reprogram the immunogenic landscape is essential. This study develops HD-FA nanoparticles by encapsulating a novel mitochondrion-targeted NIR-II modulator, HD, within DSPE-PEG-FA. HD-FA exhibits superior spatiotemporal resolution, robust tumor accumulation, and minimal adverse effects. Upon 808 nm laser irradiation, HD-FA generates reactive oxygen species, leading to ferroptosis and oxidative stress damage in GC cells by inhibiting the SLC7A11/GSH/GPX4 axis. HD-FA triggers ICD, resulting in antitumor activity not only in primary tumors but also in distant tumors. Moreover, HD-FA promotes dendritic cell maturation, increases the effector-memory T-cell frequency, and reduces the presence of myeloid-derived suppressor cells, thereby fostering enhanced antitumor immunity. This study presents the first report of a novel NIR-II modulator for GC immunogenic synergistic therapy with ICIs, marking significant advancements in the fight against GC.

Molecular Engineering of NIR-II Excitable Phototheranostic for Mitochondria-Targeted Cancer Photoimmunotherapy

The advancement of mitochondria-targeted near-infrared-II (NIR-II) excitable phototheranostics constitutes a promising strategy for improving fluorescence-image-guided cancer phototherapy. However, developing phototheranostic agents that simultaneously combine high-contrast NIR-II fluorescence imaging with effective multimodal therapeutic techniques remains a substantial challenge. Herein, we reported a shielding-donor-acceptor-donor-shielding structured NIR-II phototheranostic (FCD-T) by a molecular engineering strategy, followed by self-assembly with glutathione-responsive copolymer to form FCD-T nanoparticles. The introduction of functional bithiophene endows FCD-T with significant electron-donating properties and reduces intermolecular π-π stacking interactions. The robust π-conjugation of fluorene with good rigidity would enhance the intramolecular charge transfer capability. Therefore, FCD-T NPs exhibited an NIR-II absorption peak at 1075 nm and an emission peak at 1280 nm. Upon NIR-II light excitation, such nanoparticles could generate excellent photothermal and photodynamic performances with good biocompatibility. Moreover, the NIR-II mitochondria-targeted phototherapy further facilitated mitochondrial apoptosis-related pathways, activating antitumor immunity and inhibiting tumor growth with single irradiation at low doses.

A carnitine-based BODIPY photosensitizer

Organelle-selective photodynamic therapy (PDT) has emerged as a promising approach to enhance the precision and efficacy of cancer treatment by targeting key cellular structures. In this study, we report the design of a novel carnitine-based BODIPY photosensitizer, probe 1, which retains mitochondrial selectivity while acting as both a fluorescent probe and a potent photosensitizer. Building on our previously developed mitochondria-targeting probe (R)-BCT-2, which is transported into the mitochondrial matrix by the inner membrane protein carnitine-acylcarnitine translocase (CAC), probe 1 incorporates two bromine atoms that enhance intersystem crossing, leading to a singlet oxygen quantum yield of ∼80%, while retaining sufficient fluorescence for effective cell staining in fluorescence microscopy. Theoretical calculations indicate that the carnitine moiety distorts chromophore planarity, reducing oscillator strength but enhancing spin-orbit coupling, which, together with the extended triplet lifetime, contributes to increased phototoxicity. Probe 1 co-localizes in both mitochondria and, to a lesser extent, in lysosomes, and this dual targeting may synergistically enhance phototoxic activity by amplifying cellular stress responses. Importantly, probe 1 demonstrated high phototoxicity upon green light irradiation, with IC50 values of 52 nm under normoxia and 117 nm under hypoxia, while remaining non-cytotoxic in the dark. These results suggest that probe 1 is a promising candidate for organelle-targeted PDT, particularly in hypoxic tumor environments where its dual organelle targeting could enhance therapeutic efficacy.

Systematic review: Mechanisms of photoactive nanocarriers for imaging and therapy including controlled drug delivery

BACKGROUND

The design of smart, photoactivated nanomaterials for targeted drug delivery systems (DDS) has garnered significant research interest due in part to the ability of light to precisely control drug release in specific cells or tissues with high spatial and temporal resolution. The development of effective light-triggered DDS involves mechanisms including photocleavage, photoisomerization, photopolymerization, photosensitization, photothermal phenomena, and photorearrangement, which permit response to ultraviolet (UV), visible (Vis), and/or Near Infrared (NIR) light. This review explores recent advancements in light-responsive small molecules, polymers, and nanocarriers, detailing their underlying mechanisms and utility for drug delivery and/or imaging. Furthermore, it highlights key challenges and future perspectives in the development of light-triggered DDS, emphasizing the potential of these systems to revolutionize targeted therapies.

METHOD

A systematic literature search was performed using Google Scholar as the primary database and information source. We searched the recently published literature (within 15 years) with the following keywords individually and in relevant combinations: light responsive, nanoparticle, drug release, mechanism, photothermal, photosensitization, photopolymerization, photocleavage, and photoisomerization.

RESULTS

We selected 117 scientific articles to assess the strength of evidence after screening titles and abstracts. We found that six mechanisms (photocleavage, photoisomerization, photopolymerization, photosensitization, photothermal phenomena, and photorearrangement) have primarily been used for light-triggered drug release and categorized our review accordingly. Azobenzene/spiropyran-based derivatives and o-nitrobenzyl/Coumarin derivatives are often used for photoisomerization and photocleavage-enabled drug delivery, while free radical polymerization and cationic polymerization comprise two main mechanisms of photopolymerization. One hundred two is the primary active radical oxygen species employed for photosensitization, which is a key factor that impacts the therapeutic effects in Photodynamic therapy, but not in photothermal therapy.

CONCLUSION

The comprehensive review serves as a guiding compass for light-triggered DDS for biomedical applications. This rapidly advancing field is poised to generate breakthroughs for disease diagnosis and treatment.

Acceptor Elongation Boosted Intersystem Crossing Affords Efficient NIR Type-I and AIE-Active Photosensitizers for Targeting Ferroptosis-Based Cancer Therapy

Photosensitizers (PSs) featuring type I reactive oxygen species (ROS) generation and aggregation-induced emission (AIE) activity offer a promising solution to achieve non-invasive and precise theranostics. However, the reported AIE luminogens (AIEgens) with both AIE characteristic and strong type-I ROS generation are still scarce and the structure-property relationship is still unclear. Herein, an innovative acceptor elongation boosted intersystem crossing (AEBIC) design strategy has been proposed to endow the AIEgen strong type-I ROS producibility. The results indicate that the obtained AIEgen exhibit type-I ROS and aggregation-enhanced ROS efficacy, which has been verified by both experimental and theoretical results. Mechanistic study reveal that the acceptor elongation has promoted a dual-channel intersystem crossing pathway to enhance the intersystem crossing (ISC) process due to the differences in triplet configurations, which can be further amplified by aggregation. The afforded type-I AIE-PS show lipid droplet-anchored characteristic and can induce the ferroptosis through destroying the cellular redox homeostasis and increasing lethal levels of lipid peroxidation. Finally, targeting ferroptosis-based cancer therapy can be realized with excellent anti-tumor effect.

Acid triggering highly-efficient release of reactive oxygen species to block mitochondrial-mediated homeostasis maintenance for accelerating cell death

A pivotal pathway of photodynamic therapy (PDT) is to prompt mitochondrial damage by reactive oxygen species (ROS) generation, thus leading to cancer cell apoptosis. However, mitochondrial autophagy is induced during such a PDT process, which is a protective mechanism for cancer cell homeostasis, resulting in undermined therapeutic efficacy. Herein, we report a series of meticulously designed donor (D)-π-acceptor (A) photosensitizers (PSs), characterized by the strategic modulation of thiophene π-bridges, which exhibit unparalleled mitochondrial targeting proficiency. Notably, TTBI within this series possesses remarkable ROS generation capability, which can directly trigger mitochondrial depolarization, thus effectively inducing apoptosis in cancer cells. Meanwhile, the damaged mitochondria activate the mitophagy process, which further boosts the ROS generation of the TTBI owing to the acidic environment in the lysosome, ultimately inducing lysosomal membrane permeability (LMP), thereby blocking the protective autophagy route and promoting extra apoptotic cell death. Accordingly, TTBI disrupts the integrity of mitochondrial and lysosome, leveraging a synergistic interplay between cellular compartments to achieve more potent apoptosis. This work provides new insights to overcome the limitation of PDT efficacy imposed by mitochondrial autophagy.

Biodegradable semiconducting polymer nanoparticles for phototheranostics

Semiconducting polymer nanoparticles (SPNs) have been widely applied for phototheranostics. However, the disadvantage of in vivo long-term metabolism greatly suppresses the clinical application of SPNs. To improve the metabolic rate and minimize the long-term toxicity of SPNs, biodegradable semiconducting polymers (BSPs), whose backbones may be degraded under certain conditions, have been designed. This review summarizes recent advances in BSP-constructed nanoparticles (BSPNs) for phototheranostics. BSPs are divided into two categories: conjugated backbone degradable BSPs (CBD-BSPs) and non-conjugated backbone degradable BSPs (NCBD-BSPs), based on the feature of chemical structure. The biological applications, including cancer imaging and combination therapy, of these BSPNs are described. Finally, the conclusion and future perspectives of this field are discussed.

Twisted-Planar Molecular Engineering with Sonication-Induced J-Aggregation To Design Near-Infrared J-Aggregates for Enhanced Phototherapy

J-aggregates show great promise in phototherapy, but are limited to specific molecular skeletons and poor molecular self-assembly controllability. Herein, we report a twisted-planar molecular strategy with sonication-induced J-aggregation to develop donor-acceptor (D-A) type J-aggregates for phototherapy. With propeller aggregation-induced emission (AIE) moieties as the twisted subunits and thiophene as the planar π-bridge, the optimal twisted-planar π-interaction in MTSIC induces appropriate slip angle and J-aggregates formation, redshifting the absorption from 624 nm to 790 nm. In contrast, shorter π-planarity results in amorphous aggregates, and elongation promotes charge transfer (CT) coupled J-aggregates. Sonication was demonstrated to be effective in controlling self-assembly behaviors of MTSIC, which enables the transformation from amorphous aggregates to H-intermediates, and finally to stable J-aggregates. After encapsulation with lipid-PEG, the resultant J-dots show enhanced phototherapeutic effects over amorphous dots, including brightness, reactive oxygen species (ROS) generation, and photothermal conversion, delivering superior cancer phototherapy performance. This work not only advances D-A type J-aggregates design but also provides a promising strategy for supramolecular assembly development.

Using a stable radical as an "electron donor" to develop a radical photosensitizer for efficient type-I photodynamic therapy

Among type I photosensitizers, stable organic radicals are superior candidate molecules for hypoxia-overcoming photodynamic therapy. However, their wide applications are limited by complicated preparation processes and poor stabilities. Herein, a nitroxide radical was simply synthesized by introducing a commercially available "TEMPO" moiety. The radical exhibits efficient type-I ROS generation and appreciable photo-cytotoxicity under hypoxia, which open up a new avenue for the exploration of a novel and efficient type-I photosensitizer.

A Redox-Triggered Polymeric Nanoparticle for Disrupting Redox Homeostasis and Enhanced Ferroptosis

Cancer cells possess an efficient redox system, enabling them to withstand oxidative damage induced by treatments, especially in hypoxia areas and ferroptosis can disrupt redox homeostasis in cancer cell. Herein, GSH-sensitive nanoparticles are constructed that induce ferroptosis by long-lasting GSH depletion and enhanced PDT. Carbonic anhydrase IX inhibitor, protoporphyrin IX (Por) complexed with Fe and epirubicin (EPI) are grafted to hyaluronic acid (HA) via disulfide bonds to obtain HSPFE and loaded xCT inhibitor SAS for fabricating SAS@HSPFE which is actively targeted to deep hypoxic tumor cells, and explosively releasing EPI, Por-Fe complex and SAS due to at high GSH concentration. Specifically, SAS inhibited the GSH biosynthesis, and the generation of ROS by Por and the involvement of Fe2+ in the Fenton reaction jointly facilitates oxidative stress. Besides, Fe2+ reacted with excess H2O2 to produce O2, which continuously fuels PDT. GPX4 and SLC7A11 related to antioxidant defense are down-regulated, while ACSL4 and TFRC promoting lipid peroxidation and ROS accumulation are up-regulated, which enhanced ferroptosis by amplifying oxidative stress and suppressing antioxidant defense. SAS@HSPFE NPs revealed highly efficient antitumor effect in vivo study. This study provides a novel approach to cancer treatment by targeting redox imbalance.

Ferroptosis: A novel cell death modality as a synergistic therapeutic strategy with photodynamic therapy

Although there has been significant progress in current comprehensive anticancer treatments centered on surgery, postoperative recurrence and tumor metastasis still significantly affect both prognosis and quality of life of the patient. Hence, the development of precisely targeted tumor therapies and exploration of immunotherapy represent additional strategies for tumor treatment. Photodynamic therapy (PDT) is a relatively safe treatment modality that not only induces multiple modes of tumor cell death but also mediates the secondary immunological responses against tumor resistance and metastasis. Ferroptosis, an iron-dependent type of programmed cell death characterized by accumulation of reactive oxygen species and lipid peroxidation products to lethal levels, has emerged as an attractive target trigger for tumor therapies. Recent research has revealed a close association between PDT and ferroptosis, suggesting that combining ferroptosis inducers with PDT could strengthen their synergistic anti-tumor efficiency. Here in this review, we discuss the rationale for combining PDT with ferroptosis inducers and highlight the progress of single-molecule photosensitizers to induce ferroptosis, as well as the applications of photosensitizers combined with other therapeutic drugs for collaborative therapy. Furthermore, given the current research dilemma, we propose potential therapeutic strategies to advance the combined usage of PDT and ferroptosis inducers, providing the basis and guidelines for prospective clinical translation and research directionality with regard to PDT.

Recent advances in nanomedicine design strategies for targeting subcellular structures

The current state of cancer treatment has encountered limitations, with each method having its own drawbacks. The emergence of nanotechnology in recent years has highlighted its potential in overcoming these limitations. Nanomedicine offers various drug delivery mechanisms, including passive, active, and endogenous targeting, with the advantage of modifiability and shapability. This flexibility enables researchers to develop tailored treatments for different types of tumors and populations. As nanodrug technology evolves from first to third generation, the focus is now on achieving precise drug delivery by targeting subcellular structures within tumors. This review summarizes the progress made in subcellular structure-targeted nanodrugs over the past 5 years, highlighting design strategies for targeting mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus, and cytoskeleton. The review also addresses the current status, limitations, and future directions about the research of nanodrugs.

Dextran-based nanodrugs with mitochondrial targeting/glutathione depleting synergy for enhanced photodynamic therapy

The efficacy of photodynamic therapy (PDT) for malignant tumors is significantly impeded by the short diffusion distance of reactive oxygen species (ROS) and the ROS-consuming glutathione (GSH) overexpressed in tumor cells. Therefore, enhanced PDT can be achieved by the construction of biomacromolecule-based nanodrugs that can specifically target ROS-sensitive mitochondria and deplete intracellular GSH. Herein, we synthesized the dextran-based nano-assemblies by a Graft copolymerization Induced Self-Assembly (GISA) method, in which methyl acrylate and diallyl disulfide (DADS) were copolymerized from a mixed dextran/amino dextran backbone in an aqueous medium. Notably, the disulfide bond-containing DADS served as both GSH-depleting agent and GSH-responsive crosslinker. In order to develop a nanodrug with mitochondrial targeting/GSH depleting synergy, we further conjugated a mitochondria-targeting ligand onto the amino dextran corona, and developed a "loading-post-assembly" strategy to load a hydrophobic photosensitizer protoporphyrin IX or even multi-drugs into the hydrophobic core of the nano-assemblies. Cell and animal studies illustrated that the nanodrug could accumulate in the mitochondria of tumor cells to generate ROS in situ and thus eliminate tumors. Taken together, our work presents the dextran-based nanodrug as an efficient platform to achieve mitochondria-targeting PDT with an enhanced efficiency by simultaneously depleting intracellular GSH.

Mitochondria-Targeting Type-I Photodynamic Therapy Based on Phenothiazine for Realizing Enhanced Immunogenic Cancer Cell Death via Mitochondrial Oxidative Stress

Purpose

Photo-immunotherapy faces challenges from poor immunogenicity and low response rate due to hypoxic microenvironment. This study presents Rh-PTZ, a small organic molecule with a D-π-A structure, that simultaneously amplifies mitochondria-targeted type-I PDT-dependent immune stimulation for the treatment of hypoxic cancer.

Methods

The hydrophobic Rh-PTZ was encapsulated into F127 to prepare Rh-PTZ nanoparticles (Rh-PTZ NPs). The type-I ROS generation ability, mitochondrial targeting capacity, and ICD triggering effect mediated by Rh-PTZ NPs under LED light irradiation were investigated. Based on a 4T1 subcutaneous tumor model, the in vivo biological safety assessment, in vivo NIR fluorescent imaging, and the efficacy of PDT were assessed.

Results

Rh-PTZ could efficiently accumulate in the mitochondrial site and induce O2 •- and •OH burst in situ under LED light irradiation, thereby causing severe mitochondrial dysfunction. Rh-PTZ can amplify mitochondrial stress-caused immunogenic cell death (ICD) to stimulate the immune response, promote the maturation of sufficient dendritic cells (DCs), enhance the infiltration of immune cells, and alleviate the tumor immunosuppressive microenvironment.

Conclusion

The mitochondria-targeting type-I PDT holds promise to enhance photo-immunotherapy for hypoxia tumor treatment and overcoming the limitations of traditional immunotherapy.

Anthracene-Based Endoperoxides as Self-Sensitized Singlet Oxygen Carriers for Hypoxic-Tumor Photodynamic Therapy

Singlet oxygen is a crucial reactive oxygen species (ROS) in photodynamic therapy (PDT). However, the hypoxic tumor microenvironment limits the production of cytotoxic singlet oxygen through the light irradiation of PDT photosensitizers (PSs). This restriction poses a major challenge in improving the effectiveness of PDT. To overcome this challenge, researchers have explored the development of singlet oxygen carriers that can capture and release singlet oxygen in physiological conditions. Among these developments, anthracene-based endoperoxides, initially discovered almost 100 years ago, have shown the ability to generate singlet oxygen controllably under thermal or photo stimuli. Recent advancements have led to the development of a new class of self-sensitized anthracene-endoperoxides, with potential applications in enhancing PDT effects for hypoxic tumors. This review discusses the current research progress in utilizing self-sensitized anthracene-endoperoxides as singlet oxygen carriers for improved PDT. It covers anthracene-conjugated small organic molecules, metal-organic complexes, polymeric structures, and other self-sensitized nano-structures. The molecular structural designs, mechanisms, and characteristics of these systems will be discussed. This review aims to provide valuable insights for developing high-performance singlet oxygen carriers for hypoxic-tumor PDT.

Tumor Site-Specific In Vivo Theranostics Enabled by Microenvironment-Dependent Chemical Transformation and Self-Amplifying Effect

Precise tumor diagnosis and treatment remain complex challenges. While numerous fluorescent probes have been developed for tumor-specific imaging and therapy, few exhibit effective function in vivo. Herein, a probe called TQ-H2 is designed that can realize robust theranostic effects both in vitro and in vivo. In vitro, TQ-H2 specifically targets the lysosome and reacts with hydroxyl radical (·OH) to generate TQ-HA, which lights up the cells. TQ-HA generates reactive oxygen species (ROS) under light irradiation, enabling the simultaneous induction and monitoring of apoptosis and ferroptosis in tumor cells. Remarkably, TQ-HA also acts as a self-amplifier, autocatalytically activating TQ-H2 by generating ·OH under light exposure. This self-amplification aligns with the tumor microenvironment, where TQ-H2 undergoes chemical transformation, distinguishing tumors from healthy tissue via near-infrared (NIR) fluorescence imaging. Furthermore, ROS generated by TQ-HA effectively kills tumor cells and inhibits tumor growth without harming normal cells. This study offers a promising strategy for targeted tumor theranostics using self-amplifying microenvironment-responsive fluorescent probes.

Understanding the Structural Modulations in Twisted Donor-Acceptor-Donor (D-A-D) Systems for Boosting Type I Photosensitizing Photocatalytic Activity

Supramolecular assemblies based on the twisted donor-acceptor-donor (D-A-D) building block Qx-Ind have been developed, which interestingly, due to the balanced angle of twist (38.28°), high intermolecular charge transfer, and crystallization induced emission (CIE) characteristics, exhibit high molar absorptivity and a long-lived "lighted" excited state at the supramolecular level. The validity of the design concept was examined by preparing CIE active D-A-D system Qx-Indaz (weak donor, low angle of twist: 35.45°), in which, due to the insertion of an additional binding site for noncovalent interactions, a drastic change in the photophysical behavior is observed. The combined spectroscopic studies of all the compounds unveil the strong impact of modulation of the angle of twist and intermolecular charge transfer upon photophysical behavior in the aggregated state. Due to the favorable photophysical behavior, the supramolecular assemblies of Qx-Ind exhibit high type I photosensitizing activity in comparison to Qx-Indaz. The superior type I photosensitizing activity of Qx-Ind assemblies is manifested in their ability to efficiently catalyze the aerobic oxidative synthesis of quinazolin-4(3H)-ones (via type I ROS) from 2-aminobenzamide and aromatic aldehydes in the absence of additional additives (base/oxidant). Unlike photocatalytic nanoassemblies reported in the literature, due to the CIE characteristics, Qx-Ind does not require preliminary preparation and could be directly introduced in the solid state to reaction media. Thus, the present work demonstrates a simple strategy of upgrading type I photosensitizing activity by improving the ground/excited state behavior of a twisted D-A-D system through modulation of the angle of twist and charge transfer characteristics.

Applications of nanotheranostics in the second near-infrared window in bioimaging and cancer treatment

Achieving accurate and efficient tumor imaging is crucial in the field of tumor treatment, as it facilitates early detection and precise localization of tumor tissues, thereby informing therapeutic strategies and surgical interventions. The optical imaging technology within the second near-infrared (NIR-II) window has garnered significant interest for its remarkable benefits, such as enhanced tissue penetration depth, superior signal-to-background ratio (SBR), minimal tissue autofluorescence, reduced photon attenuation, and lower tissue scattering. This review explained the design and optimization strategies of nano-agents responsive to the NIR-II window, such as single-walled carbon nanotubes, quantum dots, lanthanum-based nanomaterials, and noble metal nanomaterials. These nano-agents enable non-invasive, deep-tissue imaging with high spatial resolution in the NIR-II window, and their superior optical properties significantly improve the accuracy, efficiency, and versatility of imaging-guided tumor treatments. And we discussed the characteristics and advantages of fluorescence imaging (FL)/photoacoustic imaging (PA) in NIR-II window, providing a comprehensive overview of the latest research progress of different nano-agents in FL/PA imaging-guided tumor therapy. Furthermore, we exhaustively reviewed the latest applications of multifunctional nano-phototherapy technologies carried out by NIR-II light including photothermal therapy (PTT), photodynamic therapy (PDT), and combined modalities like photothermal-chemodynamic therapy (PTT-CDT), photothermal-chemotherapy (PTT-CT), and photothermal- immunotherapy (PTT-IO). These imaging-guided integrated tumor therapy approaches within the NIR-II window have gradually matured over the past decade and are expected to become a safe and effective non-invasive tumor treatment. Finally, we outlined the prospects and challenges of development and innovation of the NIR-II integrated diagnosis and therapy nanoplatform. This review aims to provide insightful perspectives for future advancements in NIR-II optical tumor diagnosis and integrated treatment platforms.

Discrete Macrocyclic Polymer Hosts-Induced Cascade Luminescence Enhancement and Application in Bioimaging

The integration of polymers, supramolecular macrocycles and aggregation-induced emission (AIE) molecules provides numerous possibilities for constructing various functional supramolecular systems. Herein, we constructed supramolecular assembled systems based on discrete macrocyclic polymer hosts via the cooperation of hydra-headed macrocycles containing two or three pillar[5]arene units (defined as P2, P3), the block polymer F127 and AIE molecules (alkyl-cyano modified tetraphenylethene, alkyl-triazole-cyano modified 9,10-distyrylanthracene, defined as TPE-(CN)4 and DSA-(TACN)2). Compared with the binary assembly between hydra-headed hosts or F127 and AIE molecules, cascaded supramolecular assembly-induced emission enhancement (SAIEE) in aqueous solution was achieved in discrete macrocyclic polymer-based supramolecular assembled systems. Considering the cascaded SAIEE performance, we have successfully applied discrete macrocyclic polymer-based supramolecular assembled systems to bioimaging and constructed an artificial light-harvesting system (LHs) to explore more potential applications. The supramolecular assembly form of discrete macrocyclic polymers hosts and AIE molecules proposed in this work provides new inspiration for the construction and application of high-performance supramolecular luminescent systems.

Photodynamic therapy with NIR-II probes: review on state-of-the-art tools and strategies

In 2022 10% of the world's population was aged 65+, and by 2100 this segment is expected to hit 25%. These demographic changes place considerable pressure over healthcare systems worldwide, which results in an urgent need for accurate, inexpensive and non-invasive ways to treat cancers, a family of diseases correlated with age. Among the therapeutic tools that gained important attention in this context, photodynamic therapies (PDT), which use photosensitizers to produce cytotoxic substances for selectively destroying tumor cells and tissues under light irradiation, profile as important players for next-generation nanomedicine. However, the development of clinical applications is progressing at slow pace, due to still pending bottlenecks, such as the limited tissue penetration of the excitation light, and insufficient targeting performance of the therapeutic probes to fully avoid damage to normal cells and tissues. The penetration depth of long-wavelength near infrared (NIR) light is significantly higher than that of short-wavelength UV and visible light, and thus NIR light in the second window (NIR-II) is acknowledged as the preferred phototherapeutic means for eliminating deep-seated tumors, given the higher maximum permissible exposure, reduced phototoxicity and low autofluorescence, among others. Upon collective multidisciplinary efforts of experts in materials science, medicine and biology, multifunctional NIR-II inorganic or organic photosensitizers have been widely developed. This review overviews the current state-of-the art on NIR-II-activated photosensitizers and their applications for the treatment of deep tumors. We also place focus on recent efforts that combine NIR-II activated PDT with other complementary therapeutic routes such as photothermal therapy, chemotherapy, immunotherapy, starvation, and gas therapies. Finally, we discuss still pending challenges and problems of PDT and provide a series of perspectives that we find useful for further extending the state-of-the art on NIR-II-triggered PDT.

Recent progress of porphyrin metal-organic frameworks for combined photodynamic therapy and hypoxia-activated chemotherapy

Nanoscale metal-organic frameworks integrated with porphyrins (Por-nMOFs) have emerged as efficient nanoplatforms for photodynamic therapy (PDT), which relies on the conversion of molecular oxygen into cytotoxic singlet oxygen. However, the hypoxic microenvironment within tumors significantly limits the efficacy of PDT. To address this challenge, researchers have explored various strategies to either alter or exploit the hypoxic conditions in tumors. One such strategy involves leveraging the porous structure of Por-nMOFs to load hypoxia-activated prodrugs (HAPs) like tirapazamine (TPZ), thereby utilizing the tumor's intrinsic hypoxic environment to trigger a chemotherapeutic effect that synergizes with PDT. Advances in nanoscience have enabled the development of porphyrin-based nMOFs capable of simultaneously loading both porphyrin photosensitizers and TPZ, ensuring effective release within cancer cells under high-phosphate conditions. The subsequent activation of co-loaded TPZ, by the tumor's own hypoxic microenvironment, and that created during PDT, facilitates a combined PDT and chemotherapy approach. This method not only enhances the suppression of cancer cell proliferation but also improves control over tumor metastasis while mitigating the negative impact of hypoxia on singular Por-nMOFs in PDT. This review summarizes recent advances in Por-nMOFs research, focusing on the design strategies for enhancing water dispersibility, circulatory stability, and targeting specificity through post-synthetic modifications. Additionally, this review highlights the bioapplication of Por-nMOFs by integrating TPZ chemotherapy and other therapeutic modalities to combat hypoxic and metastatic malignancies. We anticipate that this review will inspire further research into Por-nMOFs and advance their application in biomedicine.

PEGylated BODIPY Photosensitizer for Type I Dominant Photodynamic Therapy and Afterglow Imaging

Type I photodynamic therapy (PDT) exhibits outstanding therapeutic effects in hypoxic environments in tumors, but the design of type I photosensitizers (PSs), especially those with simple structures but dramatic properties, remains a challenge. Herein, we report a design strategy for developing type I PSs in one molecule with afterglow luminescence. As a proof concept, a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) PS (BIP) bearing water-soluble poly(ethylene glycol) (mPEG550) chains is synthesized, and BIP can self-assemble into nanoparticles (BIPNs). Interestingly, BIPNs exhibit an O2•--triggered afterglow luminescence, which is scarce, especially for BODIPY derivatives. BIPNs demonstrate outstanding type I dominant PDT at an ultralow dose under both hypoxic and normoxic environments, which can significantly inhibit tumor growth under irradiation. This work highlights a high-performance PS with afterglow luminescence and excellent PDT effects, underscoring the significant potential of versatile PSs in clinical tumor theranostics.

Tetraphenylethene-Based Molecular Cage with Coenzyme FAD: Conformationally Isomeric Complexation toward Photocatalysis-Assisted Photodynamic Therapy

Flavin adenine dinucleotide (FAD), serving as a light-absorbing coenzyme factor, can undergo conformationally isomeric complexation within different enzymes to form various enzyme-coenzyme complexes, which exhibit photocatalytic functions that play a crucial role in physiological processes. Constructing an artificial photofunctional system using FAD or its derivatives can not only develop biocompatible photocatalytic systems with excellent activities but also further enhance our understanding of the role of FAD in biological systems. Here, we demonstrate a supramolecular approach for constructing an artificial enzyme-coenzyme-type host-guest complex with photoinduced catalytic function in water. First, we have designed and synthesized a water-soluble tetraphenylethene (TPE)-based octacationic molecular cage (1) with a large and flexible cavity, which can adaptively encapsulate with two FAD molecules with "U-shaped" conformation (uFAD) to form a 1:2 host-guest complex (1⊃uFAD2) in water. Second, based on the conformationally isomeric complexation of FAD within 1, the 1⊃uFAD2 complex facilitates electron and energy transfers to molecular oxygen upon the white-light illumination, efficiently producing reactive oxygen species (ROS) such as superoxide radical (O2•-) and singlet oxygen (1O2). To our knowledge, the 1⊃uFAD2 complex acts as a photocatalyst to achieve the highest turnover frequency (TOF) of 35.6 min-1 for the photocatalytic oxidation reaction of NADH via a photoinduced superoxide radical catalysis mechanism in an aqueous medium. At last, combining the cytotoxic effects of ROS and the disruption of the intracellular redox balance involving NADH, 1⊃uFAD2 as a supramolecular photosensitizer displays an excellent oxygen-independent photocatalysis-assisted photodynamic therapy in hypoxic tumors.

The cyano positional isomerism strategy for constructing mitochondria-targeted AIEgens with type I reactive oxygen species generation capability

In this work, a series of cationic luminogens (designated as PSMP isomers) were developed based on the cyano positional isomerism strategy. The isomerism of the cyano substituent on the molecular skeleton can finely regulate the optical behaviour, the type of photoinduced reactive oxygen species (ROS), and mitochondria-targeted capability of isomers. Interestingly, PSMP-4, with the cyano group installed at an appropriate location, exhibits a special aggregation-induced emission effect and potent O2˙- generation efficacy through the type I photochemistry pathway. Notably, PSMP-4 can accumulate in mitochondria with high specificity. Taking advantage of its excellent photostability, PSMP-4 realizes in situ mitochondria imaging in a washing-free manner and sensitive response to the change of mitochondrial membrane potential. The integration of comprehensive photophysical properties and mitochondrial specificity enable PSMP-4 to successfully trigger the death of cancer cells through an efficient type I photodynamic therapy process both in vitro and in multicellular tumor spheroid models.

Nanosonosensitizer Optimization for Enhanced Sonodynamic Disease Treatment

Low-intensity ultrasound-mediated sonodynamic therapy (SDT), which, by design, integrates sonosensitizers and molecular oxygen to generate therapeutic substances (e.g., toxic hydroxyl radicals, superoxide anions, or singlet oxygen) at disease sites, has shown enormous potential for the effective treatment of a variety of diseases. Nanoscale sonosensitizers play a crucial role in the SDT process because their structural, compositional, physicochemical, and biological characteristics are key determinants of therapeutic efficacy. In particular, advances in materials science and nanotechnology have invigorated a series of optimization strategies for augmenting the therapeutic efficacy of nanosonosensitizers. This comprehensive review systematically summarizes, discusses, and highlights state-of-the-art studies on the current achievements of nanosonosensitizer optimization in enhanced sonodynamic disease treatment, with an emphasis on the general design principles of nanosonosensitizers and their optimization strategies, mainly including organic and inorganic nanosonosensitizers. Additionally, recent advancements in optimized nanosonosensitizers for therapeutic applications aimed at treating various diseases, such as cancer, bacterial infections, atherosclerosis, and autoimmune diseases, are clarified in detail. Furthermore, the biological effects of the improved nanosonosensitizers for versatile SDT applications are thoroughly discussed. The review concludes by highlighting the current challenges and future opportunities in this rapidly evolving research field to expedite its practical clinical translation and application.

Three-in-One: Molecular Engineering of D-A-π-A Featured Type I and Type II Near-Infrared AIE Photosensitizers for Efficient Photodynamic Cancer Therapy and Bacteria Killing

Bacterial infections are closely correlated with the genesis and progression of cancer, and the elimination of cancer-related bacteria may improve the efficacy of cancer treatment. However, the combinatorial therapy that utilizes two or more chemodrugs will increase potential adverse effects. Image-guided photodynamic therapy is a highly precise and potential therapy to treat tumor and microbial infections. Herein, four donor-acceptor-π-bridge-acceptor (D-A-π-A) featured near-infrared (NIR) aggregation-induced emission luminogens (AIEgens) (TQTPy, TPQTPy, TQTC, and TPQTC) with type I and type II reaction oxygen species (ROS) generation capabilities are synthesized. Notably, TQTPy shows mitochondria targeted capacity, the best ROS production efficiency, long-term tumor retention capacity, and more importantly, the three-in-one fluorescence imaging guided therapy against both tumor and microbial infections. Both in vitro and in vivo results validate that TQTPy performs well in practical biomedical application in terms of NIR-fluorescence imaging-guided photodynamic cancer diagnosis and treatment. Moreover, the amphiphilic and positively charged TQTPy is able to specific and ultrafast discrimination and elimination of Gram-positive (G+) Staphylococcus aureus from Gram-negative (G-) Escherichia coli and normal cells. This investigation provides an instructive way for the construction of three-in-one treatment for image-guided photodynamic cancer therapy and bacteria elimination.

Chitosan-naphthalimide probes for dual channel recognition of HClO and H2S in cells and their application in photodynamic therapy

The combination of bio-imaging with photodynamic therapy (PDT) to accomplish theranostics is promising in cancer treatment. Three chitosan-naphthalimide probes were studied in this work. 4-(5-Bromothiophen-2-yl)-1,8-naphthalic anhydride was first synthesized, and then reacted with chitosan to obtain the macromolecules (CS-N-Br). The recognition group thiomorpholine or its derivatives were introduced into CS-N-Br to obtain nano-probes (CS-N-ML, CS-N-BSZ, CS-N-FSQ) eventually. The studies revealed that CS-N-ML and CS-N-FSQ exhibit high selectivity and can specifically recognize HClO and H2S. CS-N-ML and CS-N-FSQ can perform exogenous and endogenous confocal imaging of HClO and H2S in cells also. CS-N-ML's ability to target lysosomes positions indicated it could act as a lysosome-specific probe. It was discovered that the probes generate superoxide anions (O2•-) via a Type I mechanism. This discovery endows the probes with high photosensitizing activity even under hypoxic conditions. There is a positive correlation between the extent of the conjugated system and the photosensitivity of the probes, indicating that an enhanced conjugation leads to increased photosensitivity. Upon light irradiation, the probes generate ROS within HeLa cells. These results suggested that these probes can achieve theranostics for diseases associated with abnormal levels of HClO and H2S.

Reversible pH-switchable NIR-II nano-photosensitizer for precise imaging and photodynamic therapy of tumors

Photodynamic therapy (PDT) has attracted widespread attention from researchers as an emerging cancer treatment method. There have been many reports on various types of NIR-II photosensitizers for imaging and treatment of tumor sites. However, there are few reports on the development of NIR-II organic small molecule photosensitizers that have intelligent response to the tumor microenvironment, precise imaging, real-time treatment, and high biocompatibility. In this work, we developed a series of NIR-II photosensitizers (RBTs) with near-infrared excitation, good photostability, and large Stokes shift. Among them, RBT-Br exhibited higher reactive oxygen species (ROS) generation efficiency due to the introduction of halogen heavy atoms to enhance intersystem crossing (ISC). It is noteworthy that RBT-Br can generate singlet oxygen (1O2) and superoxide anion radicals (•O2-) simultaneously under 730 nm laser. Subsequently, we used molecular engineering technology to construct three pH-responsive NIR-II photosensitizers (RBT-pHs) by utilizing the closure of the lactam ring, among which RBT-pH-1 (pKa = 6.78) is able to be directionally activated under the stimulation of tumor micro-acid environment, with its fluorescence emission window reaching 933 nm. Subsequently, RBT-pH-1 NPs encapsulated in DSPE-mPEG5k were applied for PDT treatment of mouse tumors. The results showed that RBT-pH-1 NPs were activated by the acidic tumor microenvironment and generated ROS under laser excitation, exhibiting precise tumor imaging and significant tumor growth inhibition. We look forward to these multifunctional NIR-II organic small molecule photosensitizers providing a more efficient approach for clinical treatment of tumors. STATEMENT OF SIGNIFICANCE: A reversible pH-switchable NIR-II nano-photosensitizer RBT-pH-1 NPs (pKa = 6.76) is developed for precise imaging and PDT therapy of mouse tumors, which can be effectively used for targeted enrichment and activation of tumor micro-acid environments. The results show that this NIR-II photosensitizer generates ROS through tumor micro-acid environment stimulation and laser triggering, showing precise tumor imaging guidance and significant tumor growth inhibition.

Targeting sub-cellular organelles for boosting precision photodynamic therapy

Among various cancer treatment methods, photodynamic therapy has received significant attention due to its non-invasiveness and high efficiency in inhibiting tumour growth. Recently, specific organelle targeting photosensitizers have received increasing interest due to their precise accumulation and ability to trigger organelle-mediated cell death signalling pathways, which greatly reduces the drug dosage, minimizes toxicity, avoids multidrug resistance, and prevents recurrence. In this review, recent advances and representative photosensitizers used in targeted photodynamic therapy on organelles, specifically including the endoplasmic reticulum, Golgi apparatus, mitochondria, nucleus, and lysosomes, have been comprehensively reviewed with a focus on organelle structure and organelle-mediated cell death signalling pathways. Furthermore, a perspective on future research and potential challenges in precision photodynamic therapy has been presented at the end.

Biodegradable Cascade-Amplified Nanotheranostics for Photoacoustic-Guided Synergistic PTT/CDT/Starvation Antitumor in the NIR-II Window

The development of nanoassemblies, activated by the tumor microenvironment, capable of generating photothermal therapy (PTT) and amplifying the "ROS (·OH) storm," is essential for precise and effective synergistic tumor treatment. Herein, an innovative cascade-amplified nanotheranostics based on biodegradable Pd-BSA-GOx nanocomposite for NIR-II photoacoustic imaging (PAI) guides self-enhanced NIR-II PTT/chemodynamic therapy (CDT)/starvation synergistic therapy. The Pd-BSA-GOx demonstrates the ability to selectively convert overexpressed H2O2 into strongly toxic ·OH by a Pd/Pd2+-mediated Fenton-like reaction at a lower pH level. Simultaneously, the GOx generates H2O2 and gluconic acid, effectively disrupting nutrient supply and instigating tumor starvation therapy. More importantly, the heightened levels of H2O2 and increased acidity greatly enhance the Fenton-like reactivity, generating a significant "·OH storm," thereby achieving Pd2+-mediated cascade-amplifying CDT. The specific PTT facilitated by undegraded Pd accelerates the Fenton-like reaction, establishing a positive feedback process for self-enhancing synergetic PTT/CDT/starvation therapy via the NIR-II guided-PAI. Therefore, the multifunctional nanotheranostics presents a simple and versatile strategy for the precision diagnosis and treatment of tumors.

Paclitaxel Prodrug Enables Glutathione Depletion to Boost Cancer Treatment

Herein, we constructed a paclitaxel (PTX) prodrug (PA) by conjugating PTX with acrylic acid as a cysteine-depleting agent. The as-synthesized PA can assemble with diacylphosphatidylethanolamine-PEG2000 to form stable nanoparticles (PA NPs). After endocytosis into cells, PA NPs can specifically react with cysteine and trigger release of PTX for chemotherapy. On the other hand, the depletion of cysteine can greatly downregulate the intracellular content of glutathione and lead to oxidative stress outburst-provoking ferroptosis. The released PTX can elicit antitumor immune response by inducing immunogenic cell death, thus promoting dendritic cells maturation and cascaded cytotoxic T lymphocytes activation, which not only produces a robust immunotherapy effect but also synergizes the ferroptosis therapy by inhibiting cysteine transport via the release of interferon-γ in the activated immune system. As a result, PA NPs exhibit favorable in vitro and in vivo antitumor performance with reduced systemic toxicity. Our work highlights the potential of simple molecular design of prodrugs for enhancing the therapeutic efficacy toward malignant cancer.

A Mitochondria-Targeted Photosensitizer for Combined Pyroptosis and Apoptosis with NIR-II Imaging/Photoacoustic Imaging-Guided Phototherapy

Overcoming tumor apoptosis resistance is a major challenge in enhancing cancer therapy. Pyroptosis, a lytic form of programmed cell death (PCD) involving inflammasomes, Gasdermin family proteins, and cysteine proteases, offers potential in cancer treatment. While photodynamic therapy (PDT) can induce pyroptosis by generating reactive oxygen species (ROS) through the activation of photosensitizers (PSs), many PSs lack specific subcellular targets and are limited to the first near-infrared window, potentially reducing treatment effectiveness. Therefore, developing effective, deep-penetrating, organelle-targeted pyroptosis-mediated phototherapy is essential for cancer treatment strategies. Here, we synthesized four molecules with varying benzene ring numbers in thiopyrylium structures to preliminarily explore their photodynamic properties. The near-infrared-II (NIR-II) PS Z1, with a higher benzene ring count, exhibited superior ROS generation and mitochondria-targeting abilities, and a large Stokes shift. Through nano-precipitation method, Z1 nanoparticles (NPs) also demonstrated high ROS generation (especially type-I ROS) upon 808 nm laser irradiation, leading to efficient mitochondria dysfunction and combined pyroptosis and apoptosis. Moreover, they exhibited exceptional tumor-targeting ability via NIR-II fluorescence imaging (NIR-II FI) and photoacoustic imaging (PAI). Furthermore, Z1 NPs-mediated phototherapy effectively inhibited tumor growth with minimal adverse effects. Our findings offer a promising strategy for cancer therapy, warranting further preclinical investigations in PDT.

Targeted mitochondrial nanomaterials in biomedicine: Advances in therapeutic strategies and imaging modalities

Mitochondria, pivotal organelles crucial for energy generation, apoptosis regulation, and cellular metabolism, have spurred remarkable advancements in targeted material development. This review surveys recent breakthroughs in targeted mitochondrial nanomaterials, illuminating their potential in drug delivery, disease management, and biomedical imaging. This review approaches from various application perspectives, introducing the specific applications of mitochondria-targeted materials in cancer treatment, probes and imaging, and diseases treated with mitochondria as a therapeutic target. Addressing extant challenges and elucidating potential therapeutic mechanisms, it also outlines future development trajectories and obstacles. By comprehensively exploring the diverse applications of targeted mitochondrial nanomaterials, this review aims to catalyze innovative treatment modalities and diagnostic approaches in medical research. STATEMENT OF SIGNIFICANCE: This review presents the latest advancements in mitochondria-targeted nanomaterials for biomedical applications, covering diverse fields such as cancer therapy, bioprobes, imaging, and the treatment of various systemic diseases. The novelty and significance of this work lie in its systematic analysis of the intricate relationship between mitochondria and different diseases, as well as the ingenious design strategies employed to harness the therapeutic potential of nanomaterials. By providing crucial insights into the development of mitochondria-targeted nanomaterials and their applications, this review offers a valuable resource for researchers working on innovative treatment modalities and diagnostic approaches. The scientific impact and interest to the readership lie in the identification of promising avenues for future research and the potential for clinical translation of these cutting-edge technologies.

Ferrocene-Conjugated Paclitaxel Prodrug for Combined Chemo-Ferroptosis Therapy of Cancer

Herein, we developed a paclitaxel prodrug (PSFc) through the conjugation of paclitaxel (PTX) and ferrocene via a redox-responsive disulfide bond. PSFc displays acid-enhanced catalytic activity of Fenton reaction and is capable of forming stable nanoparticles (PSFc NPs) through the assembly with distearoyl phosphoethanolamine-PEG2000. After being endocytosed, PSFc NPs could release PTX to promote cell apoptosis in response to overexpressed redox-active species of tumor cells. Meanwhile, the ferrocene-mediated Fenton reaction promotes intracellular accumulation of hydroxyl radicals and depletion of glutathione, thus leading to ferroptosis. Compared with the clinically used Taxol, PSFc NPs exhibited more potent in vivo antitumor outcomes through the combined effect of chemotherapy and ferroptosis. This study may offer insight into a facile design of a prodrug integrating different tumor treatment methods for combating malignant tumors.

Self-Chemiluminescence-Triggered Ir(III) Complex Photosensitizer for Photodynamic Therapy against Hypoxic Tumor

The limited optical penetration depth and hypoxic tumor microenvironment (TME) are key factors that hinder the practical applications of conventional photodynamic therapy (PDT). To fundamentally address these issues, self-luminescent photosensitizers (PSs) can achieve efficient PDT. Herein, a self-chemiluminescence (CL)-triggered Ir complex PS, namely, IrL2, with low-O2-dependence type I photochemical processes is reported for efficient PDT. The rational design achieves efficient chemiluminescence resonance energy transfer (CRET) from covalently bonded luminol units to the Ir complex in IrL2 under the catalysis of H2O2 and hemoglobin (Hb) to generate O2•- and 1O2. Liposome IrL2H nanoparticles (NPs) are constructed by loading IrL2 and Hb. The intracellular H2O2 and loaded Hb catalyze the luminol part of IrL2H, and the Ir2 part is then excited to produce types I and II reactive oxygen species (ROS) through CRET, inducing cell death, even under hypoxic conditions, and promoting cell apoptosis. IrL2H is used for tumor imaging and inhibits tumor growth in 4T1-bearing mouse models through intratumoral injection without external light sources. This work provides new designs for transition metal complex PSs that conquer the limitations of external light sources and the hypoxic TME in PDT.

High-Performance NIR-II Fluorescent Type I/II Photosensitizer Enabling Augmented Mild Photothermal Therapy of Tumors by Disrupting Heat Shock Proteins

NIR-II fluorescent photosensitizers as phototheranostic agents hold considerable promise in the application of mild photothermal therapy (MPTT) for tumors, as the reactive oxygen species generated during photodynamic therapy can effectively disrupt heat shock proteins. Nevertheless, the exclusive utilization of these photosensitizers to significantly augment the MPTT efficacy has rarely been substantiated, primarily due to their insufficient photodynamic performance. Herein, the utilization of high-performance NIR-II fluorescent type I/II photosensitizer (AS21:4) is presented as a simple but effective nanoplatform derived from molecule AS2 to enhance the MPTT efficacy of tumors without any additional therapeutic components. By taking advantage of heavy atom effect, AS21:4 as a type I/II photosensitizer demonstrates superior efficacy in producing 1O2 (1O2 quantum yield = 12.4%) and O2 •- among currently available NIR-II fluorescent photosensitizers with absorption exceeding 800 nm. In vitro and in vivo findings demonstrate that the 1O2 and O2 •- generated from AS21:4 induce a substantial reduction in the expression of HSP90, thereby improving the MPTT efficacy. The remarkable phototheranostic performance, substantial tumor accumulation, and prolonged tumor retention of AS21:4, establish it as a simple but superior phototheranostic agent for NIR-II fluorescence imaging-guided MPTT of tumors.

Metal-Coordinated NIR-II Nanoadjuvants with Nanobody Conjugation for Potentiating Immunotherapy by Tumor Metabolism Reprogramming

Immune checkpoint blockade (ICB) immunotherapy remains hampered by insufficient immunogenicity and a high-lactate immunosuppressive tumor microenvironment (TME). Herein, a nanobody-engineered NIR-II nanoadjuvant with targeting metabolic reprogramming capability is constructed for potentiating NIR-II photothermal-ferroptosis immunotherapy. Specifically, the nanoadjuvant (2DG@FS-Nb) is prepared by metallic iron ion-mediated coordination self-assembly of D-A-D type NIR-II molecules and loading of glycolysis inhibitor, 2-deoxy-D-glucose (2DG), followed by modification with aPD-L1 nanobody (Nb), which can effectively target the immunosuppressive TME and trigger in situ immune checkpoint blockade. The nanoadjuvants responsively release therapeutic components in the acidic TME, enabling the precise tumor location by NIR-II fluorescence/photoacoustic imaging while initiating NIR-II photothermal-ferroptosis therapy. The remarkable NIR-II photothermal efficiency and elevated glutathione (GSH) depletion further sensitize ferroptosis to induce severe lipid peroxidation, provoking robust immunogenic cell death (ICD) to trigger anti-tumor immune response. Importantly, the released 2DG markedly inhibits lactate generation through glycolysis obstruction. Decreased lactate efflux remodels the immunosuppressive TME by suppressing M2 macrophage proliferation and downregulating regulatory T cell levels. This work provides a new paradigm for the integration of NIR-II phototheranostics and lactate metabolism regulation into a single nanoplatform for amplified anti-tumor immunotherapy combined with ICB therapy.

Exploring nanodiamonds: leveraging their dual capacities for anticancer photothermal therapy and temperature sensing

Cancer has become a primary global health concern, which has prompted increased attention towards targeted therapeutic approaches like photothermal therapy (PTT). The unique optical and magnetic properties of nanodiamonds (NDs) have made them versatile nanomaterials with promising applications in biomedicine. This comprehensive review focuses on the potential of NDs as a multifaceted platform for anticancer therapy, mainly focusing on their dual functionality in PTT and temperature sensing. The review highlighted NDs' ability to enhance PTT through hybridization or modification, underscoring their adaptability in delivering small molecule reagents effectively. Furthermore, NDs, particularly fluorescent nanodiamonds (FNDs) with negatively charged nitrogen-vacancy centers, enable precise temperature monitoring, enhancing PTT efficacy in anticancer treatment. Integrating FNDs into PTT holds promise for advancing therapeutic efficacy by providing valuable insights into localized temperature variations and cell death mechanisms. This review highlights new insights into cancer treatment strategies, showcasing the potential of NDs to revolutionize targeted therapeutics and improve patient outcomes.

Cyanine dyes in the mitochondria-targeting photodynamic and photothermal therapy

Mitochondrial dysregulation plays a significant role in the carcinogenesis. On the other hand, its destabilization strongly represses the viability and metastatic potential of cancer cells. Photodynamic and photothermal therapies (PDT and PTT) target mitochondria effectively, providing innovative and non-invasive anticancer therapeutic modalities. Cyanine dyes, with strong mitochondrial selectivity, show significant potential in enhancing PDT and PTT. The potential and limitations of cyanine dyes for mitochondrial PDT and PTT are discussed, along with their applications in combination therapies, theranostic techniques, and optimal delivery systems. Additionally, novel approaches for sonodynamic therapy using photoactive cyanine dyes are presented, highlighting advances in cancer treatment.

Structural engineering of mitochondria-targeted Au-Ag2S photosensitizers for enhanced photodynamic and photothermal therapy

Much effort has been devoted to designing diverse photosensitizers for efficient photodynamic therapy (PDT) and photothermal therapy (PTT) performance. However, the effect of PS morphology on the PDT and PTT performance needs to be further explored. In this work, a photosensitizer, Au-Ag2S nanoparticles functionalized with indocyanine green, caspase-3 recognition peptides, and mitochondria-targeting peptides (AICM NPs) with different morphologies, including core-shell, eccentric core-shell-I, eccentric core-shell-II, and Janus morphologies, were synthesized to enhance PDT and PTT performance. Among them, AICM Janus NPs with enhanced charge-transfer efficiency and photothermal conversion demonstrate superior PDT and PTT performance compared to those of other morphologies. In addition, AICM NPs exhibit satisfactory surface-enhanced Raman scattering performance for in situ SERS monitoring of caspase-3 during PDT and PTT processes. After PDT and PTT treatment with AICM Janus NPs, the damaged mitochondria released caspase-3. AICM Janus NPs achieved a superior apoptosis rate in tumor cells in vitro. Furthermore, AICM Janus NPs treat the tumors in vivo within only 10 days, which is half the time reported in other work. The AICM NPs demonstrated superior therapeutic safety both in vitro and in vivo. This study investigates the effects of morphology-property-performance of photosensitizers on the PDT and PTT performances, which opens a new pathway toward designing photosensitizers for efficient PDT and PTT.