Supramolecular Photosensitizer Enables Oxygen-Independent Generation of Hydroxyl Radicals for Photodynamic Therapy

The synthesis, photophysical and biological properties of 5,10,15,20-tetra(4-substituted phenyl)tetrabenzoporphyrin derivatives

Photodynamic therapy (PDT) had garnered considerable focus owing to its high photoactivation efficacy and low systemic toxicity. The performance of PDT heavily relied on the behavior of photosensitizers. In this study, a series of new 5,10,15,20-tetra(4-substituted phenyl)tetrabenzoporphyrin derivatives were prepared and their antitumor effects in vitro and in vivo were evaluated. These new compounds presented an absorption peak at ∼700 nm within the phototherapeutic window (600-760 nm). Their effective ROS generation capacities were predominantly verified via the type II mechanism during the irradiation process. In vitro experiments displayed that all compounds exhibited notable phototoxicity with low dark toxicity (IC50 > 76 μM) toward Eca-109 cells. Among them, VI showed obvious photoactivation with a cell survival rate reduction to 7 % at a concentration of 10 μM after exposure to 650 nm laser light (12 J/cm2). In vivo studies revealed that VI had significant antitumor effects with inhibition rate up to 94 %. Subcellular experiments demonstrated that VI distributed mainly in mitochondria, lysosomes and partially in endoplasmic reticulum. Thus, compound VI, which possessed long-wavelength and multi-wavelength absorption capabilities, high photocytotoxicity and low dark toxicity to tumor, would emerge as a promising photosensitizer for individual photo-diagnosis and photodynamic therapy.

Novel one-/two-photon excited carbazole/quinolinium photosensitizers manifest nanomolar and hypoxia-resistant tumor photodynamic therapy by accelerating apoptosis, ferroptosis, and autophagy

Photodynamic therapy (PDT) holds potential in cancer treatment, but the development of photosensitizers with high-efficient PDT remains a challenge. Herein, we designed and synthesized a series of novel tricyclic carbazole/quinolinium hybrids-KNKQ, KAKQ, and KPKQ-as photosensitizers, and subsequently evaluated their photodynamic anticancer activities and the associated mechanisms. Among them, KPKQ exhibited the most prominent one-/two-photon activated photodynamic characteristics, generating •O2-, •OH, and 1O2. Particularly, the 1O2 quantum yield of KPKQ was 3∼9-fold stronger than KNKQ and KAKQ. Most interestingly, KPKQ demonstrated nanomolar-level and hypoxic-overcoming single-photon phototoxicities with IC50 values of 27∼43 nM (PIs = 46-54), significantly surpassing existing tricyclic carbazole photosensitizers, and also exerted potent photodynamic therapeutic effects (IC50s = 0.13-0.20 μM) via two-photon excitation at 808 nm. Furthermore, KPKQ significantly promoted mitochondrial damage, cell apoptosis, and DNA lesion via reducing Bcl-2 level and increasing the levels of Bax, cleaved-Caspase-3, and γ-H2AX. Concurrently, KPKQ lowered GSH/GPX4 levels and elevated malondialdehyde to trigger ferroptosis. Additionally, KPKQ powerfully promoted autophagy through boosting LC3-II and Beclin-1 expression, thereby demonstrating a multiple anti-tumor mechanism. Ultimately, KPKQ achieved a 90.7 % tumor-inhibitory rate through in vivo PDT. Our findings may provide a promising framework for the discovery of novel tricyclic carbazole photosensitizers with high PDT efficacy.

Trilocked Photodynamic Senolytic Inducer Potentiating Immunogenic Senescent Cell Removal for Liver Fibrosis Resolution

Liver fibrosis is a major global health problem without effective therapies, and targeted elimination of senescent cells is beneficial for hepatic function and organism survival. We report a new trilocked photodynamic senolytic inducer (PDSI) strategy for liver fibrosis resolution using a type-I photodynamic agent for immunogenic clearance of senescent cells. We demonstrate that this trilocked PDSI not only facilitates efficient production of superoxide anions (O2•-) in lysosomes of senescent cells for photodynamic therapy, but also permits NIR fluorescence and photoacoustic (NIRF/PA) imaging of senescent cells. Mechanistic investigation reveals that the trilocked PDSI elicited senescent cell clearance predominantly via the immunogenic necroptosis pathway. Moreover, this PDSI with a liver-targeting moiety enables high-contrast NIRF/PA imaging and effective liver fibrosis resolution in vivo. This liver-targeting PDSI exhibits remarkable immunogenic ablation of senescent cells, with enhancing dendritic cell maturation and cytotoxic T cell recruitment in liver fibrosis. Our study highlights the potential of trilocked type I PDSI for boosting immunity for senescent cell clearance and liver fibrosis treatment.

Heavy-Atom-Free Supramolecular Photosensitizers Derived from Conventional Fluorophores

Heavy-atom-free photosensitizers (PSs) offer advantages such as efficient generation of reactive oxygen species (ROS), low dark cytotoxicity, good photostability, and high biocompatibility. Although the development of new PSs through organic synthesis has been a focus of active research, supramolecular chemistry offers a complementary pathway. This study presents a versatile supramolecular strategy to convert conventional fluorophores into heavy-atom-free PSs using a cyclic peptide-based scaffold that densely assembles fluorophore moieties. Results demonstrate that supramolecular PSs constructed from four synthetic fluorophore types-cyanines, coumarins, rhodamines, and BODIPYs-exhibit a remarkable enhancement in ROS generation efficiency, attributed to the increased intersystem crossing efficiency induced by self-assembly. Moreover, these supramolecular PSs function as visible-light photocatalysts, efficiently regenerating NAD+ from NADH. The densely packed polymer shell further shields enzymes from ROS-induced deactivation, thereby facilitating the development of robust photoenzyme catalytic systems. This study not only enriches the design methodology of heavy-atom-free PSs, but also paves the way for eco-friendly photobiocatalytic systems.

Conjugated Polymer-Photosensitizers for Cancer Photodynamic Therapy and Their Multimodal Treatment Strategies

Conjugated polymers (CPs) have emerged as promising candidates for photodynamic therapy (PDT) in cancer treatment due to their high fluorescence quantum yield, excellent photostability, and remarkable reactive oxygen species (ROS) generation capability. This review systematically summarizes molecular design strategies to augment CP photosensitivity efficiency, including: (1) constructing donor-acceptor (D-A) alternating structures, (2) incorporating aggregation-induced emission (AIE) moieties, (3) employing heavy-atom effects, and (4) designing hyperbranched architectures. In addition, considering the limitations of monotherapy like tumor heterogeneity, we will further discuss the synergistic treatment strategies of CP-mediated PDT in combination with other therapeutic modalities, including photothermal therapy (PTT)-PDT, immunotherapy-PDT, chemotherapy-PDT, Chemiluminescence (CL)-PDT, diagnostic technology-PDT, and chemodynamic therapy (CDT)-PDT. These multimodal approaches leverage complementary mechanisms to achieve enhanced tumor eradication efficacy.

Thiophene engineering of near-infrared D-π-A nano-photosensitizers for enhanced multiple phototheranostics and inhibition of tumor metastasis

Phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT) is widely used for cancer treatment because of its non-invasiveness, spatiotemporal controllability, and low side effects. However, the PTT and PDT capabilities of photosensitizers (PSs) compete so it's still a crucial challenge to simultaneously enhance the PDT and PTT capabilities of PSs. In this work, donor-π-acceptor (D-π-A)-based boron dipyrromethene (BODIPY) dyes were developed via molecular engineering and applied for enhanced phototherapy of triple-negative breast cancer. With thiophene engineering and iodine addition, D-π-A BDP dyes possessed a low energy gap between the singlet and triplet states (ΔES1-T1). After the BDP dyes were prepared into nanoparticles (NPs), the BDP4 NPs showed increased generation of type I and II reactive oxygen species (ROS) as well as a high photothermal conversion efficiency (44 %). Furthermore, folate (FA)-modified BDP4 NPs achieved high tumor targeting via near-infrared bioimaging. With these advantages, BDP4 NPs with FA achieved total tumor eradication and tumor metastasis suppression via a single injection and 808 nm laser irradiation. This work provided a rational design of D-π-A PSs for simultaneously enhancing their photodynamic and photothermal performance, achieving efficient cancer therapy.

Donor Optimizing to Boost Type I and Type II Photosensitization for Solid Tumor Therapy

Oxygen-less dependent Type I photosensitizers (PSs) have emerged as a crucial strategy for enhancing photodynamic therapy efficiency in treating hypoxic tumors. However, solid tumors have normoxia regions situated near functional blood vessels and hypoxia regions in their interiors. To maximize the utilization of oxygen within solid tumors, herein a viable donor optimizing approach is developed to enhance both Type I&II reactive oxygen species generation of PSs. At the same mole concentration, one optimized PS (named DE) generated 9 times more 1O2 than commercial Type II PS Chlorin e6 upon white light irradiation for 60 s. Compared to the commercial Type I PS Rose Bengal, •OH generation by DE is 2.9 times more under the hypoxia condition. With its optimized Type I&II pathway under normoxia and hypoxia conditions, DE is proven to be an efficient PS for solid tumor treatment, offering a promising approach for PS development.

Controllable delivery of dual-drugs for combination therapy of chemotherapy and photodynamic therapy based on pH-responsive hyaluronic acid

The non-selectivity and undesirable water solubility are major limitations for the utilization of anti-cancer drugs in traditional therapy, leading to diminished therapeutic efficacy and severe side effects. Besides, the tumor inhibitory effect of photodynamic therapy (PDT) is limited, due to the limited depth of light penetration. However, combination therapies can reverse the dilemma that monotherapies face in clinical use. Here, a stimulus-sensitive drug delivery system was prepared by self-assembly for synchronized delivery and combination therapy. It was constructed by employing pH-responsive imine bonds to attach the chemotherapeutic drug daunorubicin (DNR) and the photosensitizer methyl aminolevulinate (MAL) to oxidized hyaluronic acid (OHA), named NPs(MAL/DNR). The nanoparticles demonstrated excellent inhibitory effect and synergistic effect in tumor suppression, as evidenced by in vitro cytotoxicity results (CI = 0.90, synergism). In summary, the prepared dual-drug nanoparticles can play a synergistic role in selectively killing tumor cells. This provides a new feasible direction for the use of combined chemotherapy and photodynamic therapy in the treatment of breast cancer.

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.

Side-Chain Engineering of NIR-II-Emissive Aggregation-Induced Emission Luminogens to Boost Photodynamic and Photothermal Antimicrobial Therapy

The development of antibiotic resistance has made multidrug-resistant bacterial and fungal infections one of the most serious health problems worldwide. Photothermal therapy (PTT) and photodynamic therapy (PDT) have received increasing attention in antimicrobial fields due to their precision treatment and less susceptibility to inducing resistance. In particular, developing second near-infrared (NIR-II, 1000-1700 nm)-emissive semiconducting polymers for phototheranostics is highly desirable but remains challenging due to the lack of rational molecular design guidelines. Herein, a precise side-chain engineering strategy based on donor-acceptor (D-A)-type semiconductor polymers is developed for antimicrobial phototherapy. By subtle regulation of the side-chain flexibility, a series of NIR-II-emissive polymer aggregation-induced-emission (AIE) luminogens (AIEgens) are constructed. The optimal polymer PIDT(He)TBT bearing flexible side chains shows optimal physicochemical properties, including the highest mass extinction coefficient, the best AIE property, red-shifted absorption/emission spectra, and desirable photodynamic and photothermal effects. PIDT(He)TBT is then encapsulated into nanoparticles to endow them with water solubility, excellent photostability, and enhanced type-I photodynamic and photothermal effects. The excellent performance of PIDT(He)TBT nanoparticles in terms of fluorescence-guided type-I PDT and PTT of bacterial and fungal infections has been demonstrated both in vitro and in vivo. This work brings useful insights into designing NIR-II-emissive semiconducting polymer AIEgens for highly efficient phototheranostics.

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.

Cascade Production of In Situ Oxygen and Singlet Oxygen from Self-Assembled Nanophotosensitizer for Anti-Hypoxic Photodynamic Therapy

Photosensitizers (PSs) capable of in situ oxygen (O2) production are attractive for overcoming hypoxia in photodynamic therapy (PDT). However, these PSs generally require multiple components and complex fabrication procedures, preventing their clinical translation. Herein, we develop a single-component nanophotosensitizer via simple self-assembly that enables cascade production of in situ O2 and singlet oxygen (1O2) for superior antibacterial PDT (aPDT). Perylene tetracarboxylic acid (PTA) molecules self-assemble into nanophotosensitizers (PTA NPs). Mechanism studies reveal dual functionality of PTA NPs due to their antiparallel-displaced π-π stacking. Aggregated PTA molecules undergo intermolecular electron transfer to yield substantial photogenerated holes, while unimolecular PTA undergoes intersystem crossing to produce triplet PS (3PS*). These holes effectively oxidize water into O2 in situ, which then participates in downstream photosensitization with 3PS* to yield 1O2. This cascade reaction affords PTA NPs with continuous O2 supply and efficient 1O2 production, enabling a 63.07% higher antibacterial rate compared with the clinical antibiotic vancomycin.

Sequential metabolic probes illuminate nuclear DNA for discrimination of cancerous and normal cells

Elucidating the timing and spatial distribution of DNA synthesis within cancer cells is vital for cancer diagnosis and targeted therapy. However, current probes for staining nucleic acids rely on electrostatic interactions and hydrogen bonds with the nucleic acid, resulting in "static" DNA staining and the inability to distinguish cell types. Here, we present a proof-of-concept study of sequential metabolic probes, for the first time allowing for cancer-cell-specific illumination of DNA. This breakthrough is achieved by the combination of a "dual-locked" nucleoside analog VdU-Lys, and a new tetrazine-based bioorthogonal probe. Specifically, 5-vinyl-2'-deoxyuridine (VdU) release is only conducted in programmatically triggered histone deacetylases (HDACs) and cathepsin L (CTSL) as "sequential keys", enabling the modification of vinyl groups into the nuclear DNA of cancerous cells rather than normal cells. Subsequently, tetrazine-based Et-PT-Tz could in situ light-up DNA containing VdUs with significant fluorescence illumination (120-fold enhancement) through rapid bioorthogonal reaction. We demonstrated the compatibility of our probe in cancer-specific sensing of DNA with a high signal-to-noise ratio ranging from in vitro multiple cell lines to whole-organism scale. This approach would serve as a benchmark for the development of cell-specific metabolic reporters for DNA labelling, to characterize DNA metabolism in various types of cell lines.

Photodynamic and Photothermal Co-Induced Efficient Anti-Tumor Immunotherapy

Currently, immunotherapy based on photothermal and the application of photodynamic therapy in anti-tumor treatment is showing great potential. Its uniqueness lies in the critical role of small molecule immunomodulators in promoting effective immune responses against tumors, and the use of laser-activated biophysical mechanisms to precisely trigger the swift demise of cancer cells, avoiding damage to surrounding normal tissues. However, the use of photodynamic therapy (PDT) alone is hampered by the tumors' hypoxic environment, resulting in poor antitumor effects, while photothermal therapy (PTT) alone cannot arouse enough antigen presentation. It is of great significance to design photosensitizers (PSs) that possess both PDT and PTT effects. Herein, a series of PSs with both PDT and PTT efficacy are reported, ultimately selecting Cy7-Naph as the star molecule due to its best overall phototherapeutic effect. Upon reactive oxygen species (ROS) production and thermogenesis in tumor cells, Cy7-Naph induced significant apoptosis and eventually boosted the release of damage-associated molecular patterns (DAMPs) under near-infrared (NIR) light irradiation. By combining Cy7-Naph with the Toll-like receptor agonist Resiquimod (R848), a synergistic treatment for bilateral tumor-bearing mice is achieved. This combination promotes dendritic cell (DC) maturation and increases the infiltration of cytotoxic T lymphocytes (CTLs), leading to significant inhibition of both primary and distant tumors.

A Hypoxia-Triggered Bioreduction of Hydrophilic Type I Photosensitizer for Switchable In Vivo Photoacoustic Imaging and High-Specificity Cancer Phototherapy

Considering that hypoxia is strongly connected with tumor proliferation, metastasis, invasion, and drug resistance, it is of significant implication for alleviating the effects of hypoxia in tumor treatment. The negligible oxygen-dependent nature of type I photosensitizers (PSs) has made them appropriate candidates for the treatment of hypoxic tumors. However, the lack of effective molecular design approaches, the phototoxicity of PSs to normal tissue before and after treatment, and the drawbacks of poor hydrophilicity severely hinder the development of PSs in hypoxic tumor therapy. Thus, developing a hydrophilic PS with good hypoxia resistance and minimal side effects is an urgent but challenging problem. Herein, we present a nanotheranostic (NanoPcN8O) based on the self-assembly of a hydrophilic phthalocyanine derivative (PcN8O), a hypoxia-responsive bioreductive phototherapeutic agent suitable for activatable photoacoustic (PA) imaging and tumor therapy. Hypoxic regions in various tumors exhibit strong reductive capability, and only in such conditions did NanoPcN8O feature multiple N-oxide groups that could be bioreduced to yield the product NanoPcN8 with abundant electron-rich tertiary amine groups, which switches on the type I photodynamic and photothermal effects, facilitating the generation of type I reactive oxygen species (ROS) and heat. Better still, NanoPcN8O achieved hypoxia-induced selective PA imaging in a preclinical model. Based on these merits, the hypoxia-induced switchable type I photodynamic therapy (PDT) and photothermal therapy (PTT) strategies demonstrated remarkable phototherapeutic efficiency with high biosafety. This delicate design is anticipated to offer a novel and safe strategy to overcome hypoxia resistance in phototherapeutics.

Enhanced Sonodynamic Cancer Therapy through Boosting Reactive Oxygen Species and Depleting Glutathione

The complex tumor microenvironment (TME) affects reactive oxygen species (ROS)-based therapies; breaking the limitations of the TME to enhance the effectiveness of sonodynamic therapy (SDT) is full of great challenges. Herein, iron atomically dispersed nanoparticles (Fe-N-C) were first reported as sonosensitizers with highly efficient ROS generation by overcoming TME limitations. Its peroxidase and catalase-like activities catalyze H2O2 to produce highly toxic ·OH and in situ O2, respectively, and then O2 molecules adsorbed at Fe active sites obviously lower the energy barrier for ·OH formation. Meanwhile, its glutathione-oxidase-like activity can rapidly consume glutathione (GSH) in the TME to induce tumor cell apoptosis and ferroptosis. Density functional theory calculation results elucidate the possible mechanism of ROS generation: O2 molecules are activated by receiving sonoelectrons to generate ·O2-, which further reacts with H2O to produce OH-. Then OH- is oxidized by sonoholes to form ·OH. Fe-N-C displays a superior tumor specificity SDT.

Tumor-Targeted Exosome-Based Heavy Atom-Free Nanosensitizers With Long-Lived Excited States for Safe and Effective Sono-Photodynamic Therapy of Solid Tumors

Theranostic nanosensitizers with combined near-infrared (NIR) fluorescence imaging and sono-photodynamic effects have great potential for use in the personalized treatment of deep-seated tumors. However, developing effective nanosensitizers for NIR fluorescence image-guided sono-photodynamic therapy remains a considerable challenge, including the low generation efficacy of reactive oxygen species (ROS), poor photostability, and the absence of cancer specificity. Herein, a novel heavy atom-free nanosensitizer is developed, which exhibits intense NIR fluorescence, high ROS generation efficiency, and improved aqueous stability. By conjugating a bulky and electron-rich group, 4-(1,2,2-triphenylvinyl)-1,1'-biphenyl (TPE), to the IR820 backbone, the resulting IR820 bearing TPE (IR820-TPE) effectively generates ROS via type I and II photochemical mechanisms under 808 nm laser irradiation. Moreover, TPE conjugation considerably increases the sono-photodynamic performance of IR820. To improve the intracellular delivery and tumor-targeting ability of IR820-TPE, biotin-conjugated exosome (B-Exo) is used as a natural nanocarrier. In vitro studies demonstrate the outstanding therapeutic performance of IR820-TPE-loaded B-Exo (IR820-TPE@B-Exo) in synergistic sono-photodynamic cancer therapy. In vivo studies reveal that IR820-TPE@B-Exo shows enhanced tumor accumulation, strong fluorescence signals, and effective sono-photodynamic therapeutic activity with high biosafety. This work demonstrates that IR820-TPE@B-Exo is a promising sono-phototheranostic agent for safe and targeted cancer therapy and NIR fluorescence imaging.

Hepatoma Metastasis-Inhibiting Supramolecular Nanoglycocalyx for Enhanced Type I Photodynamic Therapy

Type I photodynamic therapy (PDT) is well demonstrated to have low oxygen dependency. However, fully suppressing the risk of hypoxia-induced tumor metastasis during PDT remains a great challenge. In this study, a tetra-lactosylated amphiphilic Aza-BODIPY glycocluster (TLBP) is reported that self-assembles into a supramolecular nanoglycocalyx on hepatoma cell membranes, serving as an artificial extracellular matrix (ECM) to inhibit hepatoma metastasis while facilitating efficient Type I PDT. Molecular engineering demonstrates that multi-glycosylation promotes the transition of nanostructures from disordered to ordered self-assembly by regulating intermolecular interactions. This modification enables the TLBP glycocalyx to exhibit significant intermolecular electron transfer, generating superoxide anion radicals (O2 -•) for Type I PDT. Moreover, the TLBP glycocalyx inhibits the PI3K-Akt signaling pathway by reducing Na+/K+-ATPase activity, leading to decreased migration and invasion of HepG2 cells. The synergistic antitumor effect of TLBP glycocalyx is further verified in a HepG2-bearing mouse model. This work innovatively utilizes glycosylation to regulate microelectronic properties and macroscopic nanoscale self-assembly characteristics, providing a novel concept for developing efficient synergistic anti-hepatoma strategies.

The Role of Open-Shell Organic Radical in Enhancing Anti-Tumor Photocatalysis Reaction of NIR Light-Activated Photosensitizer

Open-shell radical materials, which are characterized by unpaired electrons, have led to revolutionary breakthroughs in material science due to their unique optoelectronic properties. However, the involvement of organic radicals in photodynamic therapy (PDT) has rarely been reported or discussed. This work studies two photosensitizer analogs. 4AM-OS with extended π-conjugation exhibits open-shell radical characters and enhanced type-I photodynamic activity compared with closed-shell 2AM-CS. 4AM-OS displays the thermally accessible triplet-state character, resulting in more unpaired electrons delocalized along the π-conjugated backbone at higher temperatures. Accordingly, the temperature-dependent photodynamic activity of 4AM-OS confirms its association with the open-shell electronic structure. As the unpaired electrons in open-shell 4AM-OS are more delocalized and generate additional electronic energy states, photo-induced charge transfer is promoted to facilitate type-I photodynamic reactions. This observation addresses the challenge associated with near-infrared (NIR) photosensitizers, such as 4AM-OS, which often demonstrate low efficacy in PDT due to the limited energy provided by NIR light despite its superior tissue penetration depth. Overall, clarifying the beneficial role of organic radicals in photodynamic reactions will bring revolutionary breakthroughs to developing high-performance NIR photosensitizers and promoting the efficacy of PDT for deep-seated lesions.

Atomic Engineering and Aggregation Effect to Regulate Synergistically Type I Reactive Oxygen Species of AIE-Active Deep Red/Near Infrared Red Photosensitizer

"Molecular science" has long been regarded as the golden rule to guide the design of organic materials' performances in the past many years, but some interesting phenomena of conventional aggregation-caused fluorescence quenching and new aggregation-induced emission reflect that materials' properties would be changed from "molecule" to "aggregate". Therefore, "molecular science" theory faces certain limitations to guide regulating the performance of materials at aggregation. In this work, it is discovered that the photosensitizer's performances contain fluorescence and reactive oxygen species, which could be affected by changing molecular atoms and aggregation form. The introduction of oxygen and selenium atoms could redshift fluorescence and improve reactive oxygen species (ROS) efficiency. In addition to the atomic effect, the ROS efficiency of photosensitizers could be affected after coating a polymeric shell, that is, the production of type II ROS singlet oxygen (1O2) is suppressed, while the type I ROS of superoxide anion (O2 -•) is improved. This work discovers that the fluorescence and ROS efficiency of photosensitizers are relevant to the atomic effect and polymeric aggregation effect, and discussing deeply the influence mechanism, which has important research significance for modulating precisely the performances of photosensitizers and promoting the development of type I photodynamic therapy.

Oxygen tension regulating nanoformulation for the improved photodynamic therapy of hypoxic tumors

The clinical efficacy of photodynamic therapy (PDT) is hampered by the low oxygen tension highly prevalent in solid tumors. Hence, improving the oxygen tension by suppling hyperbaric oxygen (HBO), through oxygen delivery nanoarchitectures or by designing in situ oxygen-generating nanoenzymes is considered a robust approach for PDT that involves type II photosensitizers (PS). In this study, we successfully synthesized 4-arm chlorin-polylactide (CPLA) conjugates from meta-tetra-3-hydroxymethyl phenyl chlorin (m-THMPC) and D, L-lactide via ring opening polymerization (ROP), that could assemble into stable NPs, for the delivery of molecular oxygen into inner regions of hypoxic tumors (HTs). The monodispersed Air-CPLA-NPs prevented the PS, chlorin, from aggregation-induced quenching and loss of signal. Moreover, the Air-CPLA-NPs produced a marked level of intracellular ROS or 1O2 upon light irradiation (660 ± 10 nm, 20 J/cm2) which is indispensable for the prolonged and efficient PDT of HTs. The confocal laser scanning microscopy (CLSM) images revealed the gradual cellular internalization of Air-CPLA-NPs in hypoxic H1299 cells. It unveiled significant dose-dependent in vitro cytotoxicity towards normoxic and hypoxic H1299 cells. Furthermore, the in vivo anticancer study displayed the tumor growth inhibition (TGI) effect of Air-CPLA-NPs + PDT in normoxic and hypoxic xenograft mice models. Accordingly, the present architecture improved the PDT efficacy by overcoming the oxygen barrier in the inner tissues of HTs demonstrating the prospect of CPLA-NPs as an "oxygen shuttle" for the clinical PDT of solid tumors.

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

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

Engineering a Ru(ii) Nanostructure for Oxygen-Free Photocatalytic Degradation of Environmental Pollutants

The development of high-performing photocatalysts with visible-light-absorbing and oxidative properties for the degradation of organic contaminants in anaerobic microenvironments remains a challenge. Herein, a Ru-complex decorated with coumarin ([Ru(phen)2Cur]Cl2) molecules was created to achieve high absorption capacities and photocatalytic activity. Taking advantage of the nanoparticulate structure, the transformation of [Ru(phen)2Cur]Cl2 molecules into Ru(II) nanostructures (RuCur NPs) not only exhibited an extensive broad visible-light absorption spectrum but also possessed enhanced intersystem crossing efficiency and improved electron transfer. Consequently, these self-assembled nanocatalysts performed efficient photodegradation toward both antibiotics and organic dyes, especially in acidic and anaerobic environments. Mechanistically, photoactivated electrons and holes on the surface of nanostructures drive the degradation of organic molecules via direct redox reactions in an oxygen-independent manner. This result proposed a fundamental insight for developing oxygen-independent nanoparticulate photocatalysts.

Metallacage-crosslinked free-standing supramolecular networks via photo-induced copolymerization for photocatalytic water decontamination

The development of polymer materials for water decontamination makes a significant contribution to environmental protection and public health. Herein, we report the preparation of metallacage-crosslinked free-standing supramolecular networks by photo-induced copolymerization of acrylate metallacages and butyl methacrylate for water decontamination. The integration of metallacages into polymer networks endows the networks good capability for generating singlet oxygen via photosensitization, making them serve as a type of decontamination materials that can effectively eliminate diverse organic pollutants and bacterial contaminants. This study not only provides a mild and effective strategy for the preparation of metallacage-cored supramolecular networks via photo-induced copolymerization but also explores their applications for photocatalytic dye degradation and bacterial killing, which will promote the future development of metallacage-based supramolecular materials for photocatalytic applications.

Donor modulation brings all-in-one phototheranostics for NIR-II imaging-guided type-I photodynamic/photothermal synergistic cancer therapy

Type-I photodynamic (PDT) and photothermal (PTT) synergistic therapy guided by fluorescence imaging in the near-infrared region II (NIR-II) is crucial for cancer diagnosis and treatment. Phototheranostics provide a promising system for efficient imaging-guided phototherapy, combining diagnostics with therapeutics within a single photosensitizer and avoiding the complexity of composition and low reproducibility of combination methods. Herein, we design and synthesize an all-in-one phototheranostic agent OTAB by modifying aza-BODIPY with a methoxy group substituted triphenylamine moiety, followed by the formation of nanoparticle OTAB@cRGD NPs via self-assembly with DSPE-PEG2000-cRGD. Structurally, the methoxy-modified triphenylamine moiety as a strong electron donor can reduce the singlet-triplet energy gap (ΔE S1-T1) by creating a strong intramolecular charge transfer state, thereby accelerating the intersystem crossing process and thus preferentially generating O2˙- via electron transfer. A single 808 nm laser can trigger its NIR-II imaging and excellent type-I photodynamic and photothermal therapy. Furthermore, OTAB@cRGD NPs with high photostability, colloid stability and biocompatibility can actively target tumor tissue via intravenous injection. Thus, tumor localization and imaging diagnosis are successfully realized. The PDT/PTT synergistic therapy brings efficient tumor inhibition and ablation both in vitro and in vivo. Therefore, this work provides a new strategy to construct an all-in-one multifunctional probe for the integration of NIR-II diagnosis and treatment.

Flexible Formation of Nanoparticles: Selectively Self-Assembling with Glycoclusters to Form Nano-Photosensitizers for Multipurpose Bioimaging and Photodynamic Therapy

The smart construction of nano-photosensitizers (PSs) is significant for multipurpose applications, such as bioimaging, efficient photodynamic anti-tumor or anti-bacterial studies. This work reports a flexible self-assembling strategy for the construction of nano-PSs, in which PSs spontaneously form amorphous aggregates for killing bacteria, or self-assemble with tetraphenylethene (TPE) based glycoclusters (TPE-Glc4) to construct glyco-dots for cell imaging and photodynamic anti-tumor studies. Tricyanofuran (TCF) and TPE units were bridged with furan or thiophene moiety to construct two PSs (1 and 2) with NIR fluorescence in monomers, and a performance of the aggregation-induced generation of reactive oxygen species (AIG-ROS) in an aggregated state. Compared to the large amorphous aggregates (2-a), TPE-based glycoclusters encapsulated with PS form glyco-dots (2-Glc) that exhibit a smaller and more homogeneous hydrated size of approximately 40 nm, as well as enhanced water-solubility and biocompatibility. TPE-glycoclusters facilitate the cellular uptake of 2 into HepG2 cells, therefore enhancing the NIR fluorescence imaging signal and photodynamic therapy. Meanwhile, 2-a exhibits satisfied phototoxicity against Escherichia coli. This work highlights the flexible self-assembly of nano-PSs for multifunctional bioapplications.

Zwitterionic Photosensitizer-Assembled Nanocluster Produces Efficient Photogenerated Radicals via Autoionization for Superior Antibacterial Photodynamic Therapy

Photodynamic therapy (PDT) holds significant promise for antibacterial treatment, with its potential markedly amplified when using Type I photosensitizers (PSs). However, developing Type I PSs remains a significant challenge due to a lack of reliable design strategy. Herein, a Type I PS nanocluster is developed via self-assembly of zwitterionic small molecule (C3TH) for superior antibacterial PDT in vivo. Mechanism studies demonstrate that unique cross-arranged C3TH within nanocluster not only shortens intermolecular distance but also inhibits intermolecular electronic-vibrational coupling, thus facilitating intermolecular photoinduced electron transfer to form PS radical cation and anion via autoionization reaction. Subsequently, these highly oxidizing or reducing PS radicals engage in cascade photoredox to generate efficient ·OH and O2‾·. As a result, C3TH nanoclusters achieve a 97.6% antibacterial efficacy against MRSA at an ultralow dose, surpassing the efficacy of the commercial antibiotic Vancomycin by more than 8.8-fold. These findings deepen the understanding of Type I PDT, providing a novel strategy for developing Type I PSs.

Photo-Facilitated Nitric Oxide-Triggered Turn-on Photodynamic Therapy for Precise Antitumor Application

Photodynamic therapy (PDT) is a powerful strategy for tumor therapy with noninvasiveness and desirable efficacy. However, the phototoxicity of photosensitizer after the post-PDT is the major obstacle limiting the clinic applications. Herein, a nitric oxide (NO)-activatable photosensitizer is reported with turn-on PDT behavior and endoplasmic reticulum (ER) targeting ability for precise tumor therapy. Four o-thiophenediamine derivatives with reaction-tunable donor/acceptor push-pull electronic effect are established, and the systematic structure and property relationship observation reveals the following features: 1) the reactivity against NO can be improved by enhancing the electron density and further facilitated upon photo-irradiation. 2) the reactivity with NO enables the improved intramolecular charge transfer process with the evoking of photosensitizing effect. 3) only o-thiophenediamine derivative with ER enrichment behavior exhibited cancer cell ablation effect compared to photosensitizers localized in lysosome and lipid droplet. Thus, the efficient inhibition of cancer cells both in vitro and in vivo is realized based on the photo-controlled PDT strategy. This work provides more insights into developing promising activatable photosensitizers for advanced therapy based on tumor microenvironment trigger.

An Albumin-Photosensitizer Supramolecular Assembly with Type I ROS-Induced Multifaceted Tumor Cell Deaths for Photodynamic Immunotherapy

Photodynamic therapy holds great potentials in cancer treatment, yet its effectiveness in hypoxic solid tumor is limited by the oxygen-dependence and insufficient oxidative potential of conventional type II reactive oxygen species (ROS). Herein, the study reports a supramolecular photosensitizer, BSA@TPE-BT-SCT NPs, through encapsulating aggregation-enhanced emission photosensitizer by bovine serum albumin (BSA) to significantly enhance ROS, particularly less oxygen-dependent type I ROS for photodynamic immunotherapy. The abundant type I ROS generated by BSA@TPE-BT-SCT NPs induce multiple forms of programmed cell death, including apoptosis, pyroptosis, and ferroptosis. These multifaceted cell deaths synergistically facilitate the release of damage-associated molecular patterns and antitumor cytokines, thereby provoking robust antitumor immunity. Both in vitro and in vivo experiments confirmed that BSA@TPE-BT-SCT NPs elicited the immunogenic cell death, enhance dendritic cell maturation, activate T cell, and reduce myeloid-derived suppressor cells, leading to the inhibition of both primary and distant tumors. Additionally, BSA@TPE-BT-SCP NPs also exhibited excellent antitumor performance in a humanized mice model, evidenced by a reduction in senescent T cells among these activated T cells. The findings advance the development of robust type I photosensitizers and unveil the important role of type I ROS in enhancing multifaceted tumor cell deaths and antitumor immunogenicity.

Bilateral Synergistic Effects of Phototherapy-Based NIR-II Absorption Photosensitizer for Allergic Rhinitis

Allergic rhinitis (AR) is the most prevalent global health issue, affecting approximately 3 billion people, with its incidence increasing annually. The current first-line pharmacotherapy for symptom relief has limited efficacy and often results in notable side effects. Here, aza-BODIPY-based nanoparticles (RH@NPs) are developed that exhibit mild photothermal therapy (PTT) and type I photodynamic therapy (PDT) capabilities. Enhanced intramolecular charge transfer induces NIR-II absorption of the photosensitizer (RH), facilitating deeper tissue penetration for augmented AR therapy. Additionally, the use of an asymmetric donor-acceptor-acceptor' configuration promotes the self-assembly of RH, enhancing its intersystem crossing ability and enabling efficient photophysical activity. The synergistic effects of PTT (enhancing HSF1 DNA-binding activity to inhibit epithelial-mesenchymal transition by epigenetically regulating the expression of epithelial-mesenchymal transition-associated genes) and PDT (activating NRF2 transcriptional activity to stimulate the antioxidant defense system) enable RH@NPs to provide a superior therapeutic effect in a mouse model of AR. This effect is achieved by mechanically reducing the allergic response rather than merely alleviating symptoms. Notably, the photosensitizer-based physical therapy demonstrates enhanced safety. This study is the first to successfully investigate the application of phototherapy for AR and elucidate its mechanism of action, offering a novel, straightforward, and efficient treatment strategy for AR.

Glycosylated and rhodamine-conjugated tetraphenylethylene: a type I and II reactive oxygen species generator for photodynamic therapy

A lactosylated and AIE-active multifunctional photosensitizer (Lac-TR) was synthesized. Lac-TR can self-assemble into fluorescent nanoparticles (Lac-TRs) to achieve fluorescence self-reporting during photodynamic therapy and induce pyroptosis under both normoxia and hypoxia to kill HepG2 cells.

Photoredox-Mediated Immunotherapy Utilizing Rhenium(I) Photocatalysts with Electron Donor-Acceptor-Donor Configuration

The hypoxic environment of solid tumors significantly diminishes the therapeutic efficacy of oxygen-dependent photodynamic therapy. Developing efficient photosensitizers that operate via photoredox catalysis presents a promising strategy to overcome this challenge. Herein, we report the rational design of two rhenium(I) tricarbonyl complexes (Re-TPO and Re-TP) with electron donor-acceptor-donor configuration. Notably, Re-TP exhibits aggregation-induced emission properties and enhanced spin-orbit coupling compared to Re-TPO, thus exhibiting promoted photosensitizing capability. In addition to generating type I and II reactive oxygen species, the excited Re-TP facilitates the photocatalytic oxidation of NADH to NAD+ and the photoreduction of pyruvic acid to lactic acid. This metabolic intervention triggers PD-L1-linked immune responses and disrupts tumor redox balance, leading to ferroptosis and immunogenic cell death. The combined ferroptosis and immunotherapy effects significantly suppress both primary and distant B16 tumors. This investigation provides a compelling model for designing efficient metal-based PSs for photoredox-mediated photoimmunotherapy against hypoxic tumors.

Dual Pathways of Photorelease Carbon Monoxide via Photosensitization for Tumor Treatment

Carbon monoxide (CO) gas therapy, as an emerging therapeutic strategy, is promising in tumor treatment. However, the development of a red or near-infrared light-driven efficient CO release strategy is still challenging due to the limited physicochemical characteristics of the photoactivated carbon monoxide-releasing molecules (photoCORMs). Here, we discovered a novel photorelease CO mechanism that involved dual pathways of CO release via photosensitization. Specifically, the photosensitizer Chlorin e6 (Ce6) sensitized oxygen to produce singlet oxygen (1O2) and oxidized photoCORM Mn2(CO)10 to release CO in an air-saturated solvent under red light (655 nm, 50 mW/cm2) irradiation. Furthermore, Ce6 and Mn2(CO)10 could undergo multistep photochemical reactions to release CO, as well as the degradation of the photosensitizer Ce6 in an oxygen-depleted solution. As a proof of concept, we demonstrated the feasibility and tumor inhibition of this CO release strategy both in vitro and in vivo. These results provide a robust platform for the development of new approaches to CO-mediated modulation of signaling pathways and further facilitate the practical use of gas therapeutic methods in tumor therapy in vivo.

The Current Advances in Design Strategy (Indirect Strategy and Direct Strategy) for Type-I Photosensitizers

Type-I photosensitizers (PSs) are among the most potential candidates for photodynamic therapy (PDT), as their low dependence on oxygen endow them with many advantages for treating hypoxic tumor. However, most of the reported type-I PSs have a contingency of molecular design, because electron transfer (ET) reaction is more difficult to achieve than energy transfer (EET) process. Therefore, it is urgent to understand molecular design mechanisms for type-I PSs. In this review, the two ways to achieve the type-I PSs, i.e., inhibiting EET process (type-II) or enhancing ET process (type-I), are detailly explained. In response, the current design strategies of type-I PSs are summarized from two perspectives: indirect strategy (inhibiting EET process: reducing the energy of the lowest triplet excited state (T1) to lower than the energy required for the excitation energy transfer to produce singlet oxygen) and direct strategy (enhancing ET process: promoting the ET efficiency of PSs to generate superoxide radicals). The construction of direct strategy can be realized by forming an electron-rich microenvironment, providing an electron-deficient intermediate transmitter, and introducing an enhanced electron transfer capacity primitive.

Near-Infrared Organic Small-Molecule Photosensitizer With O2 Self-Supply for Cancer Photodynamic-Photothermal Synergistic Therapy

Tumor hypoxia and heat resistance as well as the light penetration deficiency severely compromise the phototherapeutic efficacy, developing phototherapeutic agents to overcome these issues has been sought-after goal. Herein, a diradical-featured organic small-molecule semiconductor, namely TTD-CN, has been designed to show low exciton binding energy of 42 meV by unique dimeric π-π aggregation, promoting near-infrared (NIR) absorption beyond 808 nm and effective photo-induced charge separation. More interestingly, its redox potentials are tactfully manipulated for water splitting to produce O2 and reduction of O2 to generate O2 •-. Besides, both ultrafast internal conversion and high-frequency stretching vibrational relaxation of C≡N bonds favor photothermy. Accordingly, TTD-CN nanoparticles have been prepared to exhibit spatiotemporally-synchronous O2 and O2 •- generation and 63.2% photothermal conversion under 808 nm laser irradiation for high-efficient photodynamic and photothermal synergistic therapy. These findings successfully realize NIR light-triggered spatiotemporally-synchronous O2 self-supply, type-I photosensitization and superior photothermy in an organic small-molecule phototherapeutic agent, significantly boosting the development of phototherapy.

One-Pot Synthesis of Oxygen Vacancy-Rich Amorphous/Crystalline Heterophase CaWO4 Nanoparticles for Enhanced Radiodynamic-Immunotherapy

Radiodynamic therapy that employs X-rays to trigger localized reactive oxygen species (ROS) generation can tackle the tissue penetration issue of phototherapy. Although calcium tungstate (CaWO4) shows great potential as a radiodynamic agent benefiting from its strong X-ray absorption and the ability to generate electron-hole (e--h+) pairs, slow charge carrier transfer and fast e--h+ recombination greatly limit its ROS-generating performance. Herein, via a one-pot wet-chemical method, oxygen vacancy-rich amorphous/crystalline heterophase CaWO4 nanoparticles (Ov-a/c-CaWO4 NPs) with enhanced radiodynamic effect are synthesized for radiodynamic-immunotherapy of cancer. The phase composition and oxygen vacancy content of CaWO4 can be easily tuned by adjusting the solvothermal temperature. More intriguingly, the amorphous/crystalline interfaces and abundant oxygen vacancies accelerate charge carrier transfer and suppress e--h+ recombination, respectively, enabling synergistically improved ROS production from X-ray-irradiated Ov-a/c-CaWO4 NPs. In addition to directly inducing oxidative damage of cancer cells, radiodynamic generation of ROS also boosts immunogenic cell death to provoke a systemic antitumor immune response, thereby allowing the inhibition of both primary and distant tumors as well as cancer metastasis. This study establishes a synergistic enhancement strategy involving the integration of phase and defect engineering to improve the ROS generation capacity of radiodynamic-immunotherapeutic anticancer nanoagents.

Recent Advances in Strategies to Enhance Photodynamic and Photothermal Therapy Performance of Single-Component Organic Phototherapeutic Agents

Photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as promising treatment options, showcasing immense potential in addressing both oncologic and nononcologic diseases. Single-component organic phototherapeutic agents (SCOPAs) offer advantages compared to inorganic or multicomponent nanomedicine, including better biosafety, lower toxicity, simpler synthesis, and enhanced reproducibility. Nonetheless, how to further improve the therapeutic effectiveness of SCOPAs remains a challenging research area. This review delves deeply into strategies to improve the performance of PDT or PTT by optimizing the structural design of SCOPAs. These strategies encompass augmenting reactive oxygen species (ROS) generation, mitigating oxygen dependence, elevating light absorption capacity, broadening the absorption region, and enhancing the photothermal conversion efficiency (PCE). Additionally, this review also underscores the ideal strategies for developing SCOPAs with balanced PDT and PTT. Furthermore, the potential synergies are highlighted between PDT and PTT with other treatment modalities such as ferroptosis, gas therapy, chemotherapy, and immunotherapy. By providing a comprehensive analysis of these strategies, this review aspires to serve as a valuable resource for clinicians and researchers, facilitating the wider application and advancement of SCOPAs-mediated PDT and PTT.

Integration of Motion and Stillness: A Paradigm Shift in Constructing Nearly Planar NIR-II AIEgen with Ultrahigh Molar Absorptivity and Photothermal Effect for Multimodal Phototheranostics

The two contradictory entities in nature often follow the principle of unity of opposites, leading to optimal overall performance. Particularly, aggregation-induced emission luminogens (AIEgens) with donor-acceptor (D-A) structures exhibit tunable optical properties and versatile functionalities, offering significant potential to revolutionize cancer treatment. However, trapped by low molar absorptivity (ε) owing to the distorted configurations, the ceilings of their photon-harvesting capability and the corresponding phototheranostic performance still fall short. Therefore, a research paradigm from twisted configuration to near-planar structure featuring a high ε is urgently needed for AIEgens development. Herein, by introducing the strategy of "motion and stillness" into a highly planar A-D-A skeleton, we successfully developed a near-infrared (NIR)-II AIEgen of Y5-2BO-2BTF, which boasts an impressive ε of 1.06 × 105 M-1 cm-1 and a photothermal conversion efficiency (PCE) of 77.8%. The modification of steric hindrance on the benzene ring in the acceptor unit of the aggregation-caused quenching counterpart Y5-2BO, to a meta-CF3-substituted naphthyl, leads to reversely staggered packing and various intermolecular noncovalent conformational locks in Y5-2BO-2BTF ("stillness"). Furthermore, the -CF3 moiety acted as a flexible motion unit with an ultralow energy barrier, significantly facilitating the photothermal process in loose Y5-2BO-2BTF aggregates ("motion"). Accordingly, Y5-2BO-2BTF nanoparticles enabled tumor eradication and pulmonary metastasis inhibition through NIR-II fluorescence-photoacoustic-photothermal imaging-navigated type I photodynamic-photothermal therapy. This work provides the first evidence that the highly planar conformation with a reversely staggered stacking arrangement could serve as a novel molecular design direction for AIEgens, shedding new light on constructing superior phototheranostic agents for bioimaging and cancer therapy.

Constructing a Polyoxometalate-Based Metal-Organic Framework for Photocatalytic Oxidation of Thioethers to Sulfoxides Utilizing In Situ-Generated Superoxide Radicals

Developing new photocatalysts for the selective oxidation of thioethers to high-value-added sulfoxides under low-oxygen mild conditions is a promising but challenging strategy. Here, a new polyoxometalate-based metal-organic framework (POMOF), CoBW12-TPT, was successfully synthesized, wherein continuous π···π stacking interactions and direct coordination bonds not only strengthen the framework's stability but also accelerate electron transfer. A series of experiments and theoretical studies, including control experiments, kinetic studies, electrochemical spectroscopic analyses, and electron paramagnetic resonance, revealed the synergistic catalytic effect among Co(II) metal centers, BW12O405-, and the photosensitizer TPT. CoBW12-TPT was applied in the photocatalytic oxidation of thioethers to sulfoxides. Under irradiation, the photoinduced electron transfer of POMOF leads to the generation of superoxide radicals from O2, which controls the selective generation of sulfoxide compounds in the photocatalytic desulfurization reaction and shows good activity. In particular, it can be applied to the construction of some drug molecules such as Modafinil and Albendazole Oxide.

A Conjugated Oligomer with Drug Efflux Pump Inhibition and Photodynamic Therapy for Synergistically Combating Resistant Bacteria

High expression of drug efflux pump makes antibiotics ineffective against bacteria, leading to drug-resistant strains and even the emergence of "superbugs". Herein, we design and synthesize a dual functional o-nitrobenzene (NB)-modified conjugated oligo-polyfluorene vinylene (OPFV) photosensitizer, OPFV-NB, which can depress efflux pump activity and also possesses photodynamic therapy (PDT) for synergistically overcoming drug-resistant bacteria. Upon light irradiation, the OPFV-NB can produce aldehyde active groups to covalently bind outer membrane proteins, such as tolerant colicin (TolC), blocking drug efflux of bacteria. The minimum inhibitory concentration of antibiotic model chloramphenicol (CHL) is reduced about 64 times, significantly resensitizing drug-resistant bacteria to antibiotics. Also, the probe can produce highly efficient reactive oxygen species (ROS) under light irradiation. Consequently, the unimolecular OPFV-NB-based system demonstrates insusceptibility to antibiotic resistance while maintaining significant antimicrobial effects (100%) against drug-resistant bacteria. More importantly, in vivo assays corroborate that the combined system greatly accelerates wound healing by eradicating the bacterial population, dampening inflammation, and promoting angiogenesis. Overall, the OPFV-NB not only counteracts antibiotic resistance but also holds tremendous PDT efficiency, which provides a promising therapeutic strategy for combating drug-resistant bacteria and treating bacteria-infected wounds.

Core-Shell Structured Metal-Organic Frameworks for pH-Triggered Combination Photodynamic/Chemotherapy-Based Cancer Treatment

The use of hypoxia-activated prodrugs is a promising strategy to address the limitations of photodynamic therapy (PDT) caused by a hypoxic tumor microenvironment. However, the controlled release of these hypoxia-activated prodrugs during PDT remains a challenge. In this study, we present a metal-organic framework (MOF) with a core-shell structure that can achieve a high PDT efficacy and on-demand release of hypoxia-activated prodrugs (AQ4N) for hypoxic tumor therapy. The nanocomposites were created by assembling zeolitic imidazolate frameworks (ZIF-8) onto the surface of AQ4N-encapsulated porphyrinic MOF, followed by surface functionalization with folic acid-conjugated polyethylene glycol. AQ4N is entrapped in the mesopores of MOFs, and it shows acidic environment-triggered release due to the degradation of the ZIF-8. When exposed to laser, porphyrinic MOFs can produce reactive oxygen species for PDT. At the same time, PDT exacerbates hypoxia at the tumor site, leading to the bioreduction of AQ4N to AQ4 for enhanced anticancer activity. This work presents a practical approach to improve the tumor-targeting and therapeutic efficiency of hypoxic tumors.

Engineered hypoxia-responsive albumin nanoparticles mediating mitophagy regulation for cancer therapy

Hypoxic tumors present a significant challenge in cancer therapy due to their ability to adaptation in low-oxygen environments, which supports tumor survival and resistance to treatment. Enhanced mitophagy, the selective degradation of mitochondria by autophagy, is a crucial mechanism that helps sustain cellular homeostasis in hypoxic tumors. In this study, we develop an azocalix[4]arene-modified supramolecular albumin nanoparticle, that co-delivers hydroxychloroquine and a mitochondria-targeting photosensitizer, designed to induce cascaded oxidative stress by regulating mitophagy for the treatment of hypoxic tumors. These nanoparticles are hypoxia-responsive and release loaded guest molecules in hypoxic tumor cells. The released hydroxychloroquine disrupts the mitophagy process, thereby increasing oxidative stress and further weakening the tumor cells. Additionally, upon laser irradiation, the photosensitizer generates reactive oxygen species independent of oxygen, inducing mitochondria damage and mitophagy activation. The dual action of simultaneous spatiotemporal mitophagy activation and mitophagy flux blockade results in enhanced autophagic and oxidative stress, ultimately driving tumor cell death. Our work highlights the effectiveness of hydroxychloroquine-mediated mitophagy blockade combined with mitochondria-targeted photosensitizer for cascade-amplified oxidative stress against hypoxic tumors.

Photo-Triggered Fluorescence Polyelectrolyte Nanoassemblies: Manipulate and Boost Singlet Oxygen in Photodynamic Therapy

Photodynamic therapy (PDT) is a clinically approved therapeutic modality that has shown great potential for cancer treatment. However, there exist two major problems hindering PDT applications: the nonspecific phototoxicity requiring patients to stay in dark post-PDT, and the limited photodynamic efficiency. Herein, we report a photo-triggered porphyrin polyelectrolyte nanoassembling (photo-triggered PPN) strategy, in which porphyrin photosensitizer and photoswitchable energy accepter are assembled into polyelectrolyte micelles by a combined force of charge interaction and metal-ligand coordination. The polyelectrolyte-based PPN exhibits good biocompatibility, and bestows a unique "confining isolated" inner microenvironment for fully overcoming the π-π stacking of porphyrins with significant photodynamic efficiency (123-fold enhancement). Due to the high Förster resonance energy transfer (FRET) (91.5 %) between porphyrin and photoswitch in closed-form, we could use light as a specific trigger to modulate photoswitch between closed- and open-form, and manipulate the 1O2 generation in three stages: pre-PDT (quenching 1O2 generation), during PDT (activating 1O2 generation), and post-PDT (silencing 1O2 generation). This de novo strategy has for the first time realized remotely manipulating and boosting 1O2 generation in PDT, well resolving the critical and general challenges of limited photodynamic efficiency and side effects from nonspecific phototoxicity.

The Photodynamic Agent Designed by Involvement of Hydrogen Atom Transfer for Enhancing Photodynamic Therapy

Although Type-I photodynamic therapy has attracted increasingly growing interest due to its reduced dependence on oxygen, the design of effective Type-I photosensitizers remains a challenge. In this work, we report a design strategy for Type-I photosensitizers by the involvement of hydrogen atom transfer (HAT). As a proof of concept, a HAT-involved Type-I PS, which simultaneously generates superoxide and carbon-centered radicals under light-irradiation, was synthesized. This photosensitizer is comprised of a fluorene-substituted BODIPY unit as an electron acceptor covalently linked with a triphenylamine moiety as an electron donor. Under light-irradiation, photo-induced intramolecular electron transfer occurs to generate the BODIPY anion radical and triphenylamine cation radical. The former transfers electrons to oxygen to generate O2 -⋅, while the latter loses a proton to produce a benzyl carbon-centered radical which is well characterized. The resulting carbon-centered radicals efficiently oxidize NADH by HAT reaction. This photosensitizer demonstrates remarkable photocytotoxicity even under hypoxic conditions, along with outstanding in vivo antitumor efficacy in mouse models bearing HeLa tumors. This work offers a novel strategy for the design of Type-I photosensitizers by involvement of HAT.

Phthalocyanine aggregates as semiconductor-like photocatalysts for hypoxic-tumor photodynamic immunotherapy

Photodynamic immunotherapy (PIT) has emerged as a promising approach for efficient eradication of primary tumors and inhibition of tumor metastasis. However, most of photosensitizers (PSs) for PIT exhibit notable oxygen dependence. Herein, a concept emphasizing on transition from molecular PSs into semiconductor-like photocatalysts is proposed, which converts the PSs from type II photoreaction to efficient type I photoreaction. Detailed mechanism studies reveal that the nanostructured phthalocyanine aggregate (NanoNMe) generates radical ion pairs through a photoinduced symmetry breaking charge separation process, achieving charge separation through a self-substrate approach and leading to exceptional photocatalytic charge transfer activity. Additionally, a reformed phthalocyanine aggregate (NanoNMO) is fabricated to improve the stability in physiological environments. NanoNMO showcases significant photocytotoxicities under both normoxic and hypoxic conditions and exhibits remarkable tumor targeting ability. Notably, the NanoNMO-based photodynamic therapy and PD-1 checkpoint inhibitor-based immunotherapy synergistically triggers the infiltration of cytotoxic T lymphocytes into the tumor sites of female mice, leading to the effective inhibition of breast tumor growth.

Divulging the potency of naturally derived photosensitizers in green PDT: an inclusive review Of mechanisms, advantages, and future prospects

Photodynamic Therapy (PDT) offers a minimally invasive approach for treating various health conditions, employing a photosensitizer (PS) and specific light. Recent enhancements make PDT outpatient-friendly and less discomforting. Effectiveness hinges on selecting the appropriate PS. This article delves into natural and synthetic PSs, emphasizing the rising interest in natural alternatives for their safety. It explores their mechanisms, characteristics, and applications, offering insights into their potential contributions to advancing PDT. This extensive review delves into the preclinical and clinical landscape of natural PSs for PDT, shedding light on their diverse applications and promising outcomes. Compounds like curcumin, piperine, riboflavin, psoralen, hypericin, and others show significant potential in preclinical in vitro studies across various cell lines. In vivo, these photosensitizers prove effective against skin tumors, carcinomas, and sarcomas, inducing apoptosis, autophagy, and ROS generation for therapeutic efficacy. The review underscores the critical role of proper dosing and monitoring in balancing therapeutic benefits and risks. It highlights the advantages and limitations of natural PSs, emphasizing their specific targeting, bioavailability, and limited side effects. The future of PDT holds promising breakthroughs, taking from some evidence like Bergamot oil in nanostructured lipid carriers for dermatological conditions. Second-generation photosensitizer Tookad shows potential in prostate cancer treatment, while Tripterygium wilfordii Hook. F. emerges as an antimicrobial PDT source etc. Thus, environmental concerns in PDT prompt a shift to plant extracts for PS purification. The evidence-supported focus on natural PSs establishes this article as a key resource for advancing natural compounds in PDT and their therapeutic applications.

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.

Coassembly of Dual-Modulated AIE-ESIPT Photosensitizers and UCNPs for Enhanced NIR-Excited Photodynamic Therapy

Aggregation-induced emission (AIE) photosensitizers are promising for photodynamic therapy, yet their short excitation wavelengths present a limitation. In this study, we develop a series of organic photosensitizers with dual modulation capabilities based on excited-state intramolecular proton transfer (ESIPT) and AIE. Notably, we synthesize near-infrared (NIR)-excited photosensitive nanoparticles through a coassembly strategy utilizing upconversion nanoparticles (UCNPs) and amphiphilic polymers. The spectroscopic analysis and theoretical calculations elucidate the significant impact of additional or π-spacer groups on the conformational change and the energy barrier of the ESIPT process. An efficient Förster resonance energy transfer between the photosensitizer and UCNPs is achieved through the coassembly strategy. Both in vitro and in vivo experiments demonstrate the antitumor efficacy of these nanoparticles under NIR excitation. This work not only introduces a novel approach for simultaneously modulating AIE properties and the ESIPT process but also provides a robust solution for overcoming the excitation wavelength limitations of many organic photosensitizers.