Achieving Efficient NIR-II Type-I Photosensitizers for Photodynamic/Photothermal Therapy upon Regulating Chalcogen Elements

Recent advances in nanoagents delivery system-based phototherapy for osteosarcoma treatment

Osteosarcoma (OS) is a prevalent and highly malignant bone tumor, characterized by its aggressive nature, invasiveness, and rapid progression, contributing to a high mortality rate, particularly among adolescents. Traditional treatment modalities, including surgical resection, radiotherapy, and chemotherapy, face significant challenges, especially in addressing chemotherapy resistance and managing postoperative recurrence and metastasis. Phototherapy (PT), encompassing photodynamic therapy (PDT) and photothermal therapy (PTT), offers unique advantages such as low toxicity, minimal drug resistance, selective destruction, and temporal control, making it a promising approach for the clinical treatment of various malignant tumors. Constructing multifunctional delivery systems presents an opportunity to effectively combine tumor PDT, PTT, and chemotherapy, creating a synergistic anti-tumor effect. This review aims to consolidate the progress in the application of novel delivery system-mediated phototherapy in osteosarcoma. By summarizing advancements in this field, the objective is to propose a rational combination therapy involving targeted delivery systems and phototherapy for tumors, thereby expanding treatment options and enhancing the prognosis for osteosarcoma patients. In conclusion, the integration of innovative delivery systems with phototherapy represents a promising avenue in osteosarcoma treatment, offering a comprehensive approach to overcome challenges associated with conventional treatments and improve patient outcomes.

Photoimmunotherapy for cancer treatment based on organic small molecules: Recent strategies and future directions

Photodynamic therapy (PDT) is considered as a promising anticancer approach, owning to its high efficiency and spatiotemporal selectivity. Ample evidence indicated that PDT can trigger immunogenic cell death by releasing antigens that activate immune cells to promote anti-tumor immunity. Nevertheless, the inherent nature of tumors and their complex heterogeneity often limits the efficiency of PDT, which can be overcome with a novel strategy of photo-immunotherapy (PIT) strategy. By exploring the principles of PDT induction and ICD enhancement, combined with other therapies such as chemotherapy or immune checkpoint blockade, the tailored solutions can be designed to address specific challenges of drug resistance, hypoxic conditions, and tumor immunosuppressive microenvironments (TIMEs), which enables targeted enhancement of systemic immunity to address most distant and recurrent cancers. The present article summarizes the specific strategies of PIT and discusses recent existing limitations. More importantly, we anticipate that the perspectives presented herein will help address the clinical translation challenges associated with PIT.

Multifunctional NIR-II nanoplatform for disrupting biofilm and promoting infected wound healing

Healing wounds presents a significant challenge due to bacterial biofilm infections and the inherent drug resistance of these biofilms. This report introduces a multifunctional nanoplatform (NPs) designed to combat wound biofilm infections using NIR-II photothermal therapy. The NPs are self-assembled from amphiphilic polymers (AP) to encapsulate photothermal polymers (PT) through classic electrostatic interactions. Importantly, these NPs are electrically neutral, which enhances their ability to penetrate biofilms effectively. Once inside the biofilm, the NPs achieve complete thermal ablation of the biofilm under NIR-II laser irradiation. Additionally, when exposed to laser and the GSH microenvironment, the NPs exhibit strong photothermal effects and self-degradation capabilities. In vitro tests confirm that the NPs have excellent antibacterial and anti-biofilm properties against methicillin-resistant Staphylococcus aureus (MRSA). In vivo studies demonstrate that the NPs can efficiently clear wound biofilm infections and promote wound healing. Notably, the NPs show superior photothermal effects under NIR-II laser irradiation compared to NIR-I lasers. In summary, the developed NPs serve as an integrated diagnostic and therapeutic nano-antimicrobial agent, offering promising applications for biofilm wound infections and wound healing.

A simple hydrogen peroxide-activatable Bodipy for tumor imaging and type I/II photodynamic therapy

Tumor microenvironment-activatable photosensitizers have gained significant attention for cancer theranostics. Considering the hypoxic environment of solid tumors, activatable phototheranostic agents with type I PDT are desired to obtain improved cancer treatment efficiency. Herein, we report a simple, effective and multifunctional Bodipy photosensitizer for tumor imaging and type I/II photodynamic therapy. The photosensitizer featuring a methylphenylboronic acid pinacol ester group at the meso-position of Bodipy specifically responds to tumor-abundant H2O2. Its photophysical properties were characterized using steady-state and time-resolved transient optical spectroscopies. The fluorescence (ΦF = 0.09%) and singlet oxygen efficacy (ΦΔ = 10.2%) of the Bodipy units were suppressed in the caged dyads but significantly enhanced (ΦF = 0.72%, ΦΔ = 20.3%) upon H2O2 activation. Fluorescence emission spectroscopy and continuous wave electron paramagnetic resonance (EPR) spectroscopy confirmed that the Bodipy photosensitizer generates reactive oxygen species (ROS) via both electron transfer-mediated type I and energy transfer-mediated type II mechanisms. In vitro experiments demonstrated rapid internalization into tumor cells, enhanced brightness stimulated by tumor microenvironments, and tumor cell death (phototoxicity, IC50 = 0.5 μM). In vivo fluorescence imaging indicated preferential accumulation of this Bodipy photosensitizer in tumor sites, followed by decaging by tumor-abundant H2O2, further elevating the signal-to-background ratio (SBR) of imaging. Besides outstanding performance in tumor imaging, a prominent inhibition of tumor growth was observed. Given its simple molecular skeleton, this Bodipy photosensitizer is a competitive candidate for cancer theranostics.

Recent advances in biomaterials based near-infrared mild photothermal therapy for biomedical application: A review

Mild photothermal therapy (MPTT) generates heat therapeutic effect at the temperature below 45 °C under near-infrared (NIR) irradiation, which has the advantages of controllable treatment efficacy, lower hyperthermia temperatures, reduced dosage, and minimized damage to surrounding tissues. Despite significant progress has been achieved in MPTT, it remains primarily in the stage of basic and clinical research and has not yet seen widespread clinical adoption. Herein, a comprehensive overview of the recent NIR MPTT development was provided, aiming to emphasize the mechanism and obstacles, summarize the used photothermal agents, and introduce various biomedical applications such as anti-tumor, wound healing, and vascular disease treatment. The challenges of MPTT were proposed with potential solutions, and the future development direction in MPTT was outlooked to enhance the prospects for clinical translation.

Piezoelectric Bilayer Nickel-Iron Layered Double Hydroxide Nanosheets with Tumor Microenvironment Responsiveness for Intensive Piezocatalytic Therapy

Piezocatalytic therapy (PCT) based on 2D layered materials has emerged as a promising non-invasive tumor treatment modality, offering superior advantages. However, a systematic investigation of PCT, particularly the mechanisms underlying the reactive oxygen species (ROS) generation by 2D nanomaterials, is still in its infancy. Here, for the first time, biodegradable piezoelectric 2D bilayer nickel-iron layered double hydroxide (NiFe-LDH) nanosheets (thickness of ≈1.86 nm) are reported for enhanced PCT and ferroptosis. Under ultrasound irradiation, the piezoelectric semiconducting NiFe-LDH exhibits a remarkable ability to generate superoxide anion radicals, due to the formation of a built-in electric field that facilitates the separation of electrons and holes. Notably, the significant excitonic effect in the ultrathin NiFe-LDH system enables long-lived excited triplet excitons (lifetime of ≈5.04 µs) to effectively convert triplet O2 molecules into singlet oxygen. Moreover, NiFe-LDH exhibited tumor microenvironment (TME)-responsive peroxidase (POD)-like and glutathione (GSH)-depleting capabilities, further enhancing oxidative stress in tumor cells and inducing ferroptosis. To the best of knowledge, this is the first report on piezoelectric semiconducting sonosensitizers based on LDHs for PCT and ferroptosis, providing a comprehensive understanding of the piezocatalysis mechanism and valuable references for the application of LDHs and other 2D materials in cancer therapy.

Biomimetic Gold Nanorods-Manganese Porphyrins with Surface-Enhanced Raman Scattering Effect for Photoacoustic Imaging-Guided Photothermal/Photodynamic Therapy

Surface-enhanced Raman scattering (SERS) imaging integrating photothermal and photodynamic therapy (PTT/PDT) is a promising approach for achieving accurate diagnosis and effective treatment of cancers. However, most available Raman reporters show multiple signals in the fingerprint region, which overlap with background signals from cellular biomolecules. Herein, a 4T1 cell membrane-enveloped gold nanorods-manganese porphyrins system (GMCMs) is designed and successfully fabricated as a biomimetic theranostic nanoplatform. Manganese porphyrins are adsorbed on the surface of Au nanorods via the terminal alkynyl group. Cell membrane encapsulation protects the manganese porphyrins from falling off the gold nanorods. The biomimetic GMCMs confirm specific homologous targeting to 4T1 cells with good dispersibility, excellent photoacoustic (PA) imaging properties, and preferable photothermal and 1O2 generation performance. GMCMs exhibit distinct SERS signals in the silent region without endogenous biomolecule interference both in vitro and in vivo. Manganese ions could not only quench the fluorescence of porphyrins to enhance the SERS imaging effect but also deplete cellular GSH to increase 1O2 yield. Both in vitro and in vivo studies demonstrate that GMCMs effectively eradicate tumors through SERS/PA imaging-guided PTT/PDT. This study provides a feasible strategy for augmenting the Raman imaging effects of the alkynyl group and integrating GSH-depletion to enhance PTT/PDT efficacy.

An Active Self-Mitochondria-Targeting Cyanine Immunomodulator for Near-Infrared II Fluorescence Imaging-Guided Synergistic Photodynamic Immunotherapy

Photodynamic therapy targeting mitochondria represents a promising therapeutic strategy for fighting diverse types of cancers. However, the currently available photosensitizers (PSs) suffer from insufficient therapeutic potency, limited mitochondria delivery efficiency, and the inability to treat invisible metastatic distal cancers. Herein, an active self-mitochondria-targeting heptapeptide cyanine (HCy) immunomodulator (I2HCy-QAP) is reported for near-infrared II (NIR-II) fluorescence imaging-guided photodynamic immunotherapy of primary and distal metastatic cancers. The I2HCy-QAP is designed by introducing a quaternary ammonium salt with a phenethylamine skeleton (QAP) into the iodinated HCy photosensitizer. The I2HCy-QAP can precisely target mitochondria due to the lipophilic cationic QAP unit, present strong NIR-II fluorescence tail emission, and effectively generate singlet oxygen 1O2 under NIR laser irradiation, thereby inducing mitochondria-targeted damages and eliciting strong systemic immunogenic cell death immune responses. The combination of the I2HCy-QAP-mediated photodynamic immunotherapy with anti-programmed death-1 antibody therapy achieves remarkable therapeutic efficacy against both primary and distal metastatic cancers with significant inhibition of lung metastasis in a triple-negative breast cancer model. This work provides a new concept for designing high-performance NIR emissive cyanine immunomodulators for NIR-II fluorescence-guided photodynamic immunotherapy.

De novo design of type-l photosensitizer agents based on structure-inherent low triplet energy for hypoxia photodynamic therapy

Photodynamic therapy (PDT), owing to its low invasiveness, high efficiency, fewer side effects, spatiotemporal controllability and good selectivity, has attracted increasing attention for its tremendous potential in revolutionizing conventional strategies of tumor treatment. However, hypoxia is a common feature of most malignancies and has become the Achilles' heel of PDT. Currently, Type II photosensitizers (PSs) have inadequate efficacy for PDT due to the inherent oxygen consumption of the anoxic tumor microenvironment. Moreover, due to the absence of a general molecular design strategy and the limitations imposed by the energy gap law, Type-I PSs are less reported. Therefore, the development of Type-I PSs with hypoxia resistant capabilities is urgently required. Herein, in this study, we have obtained pure Type-I materials for the first time by employing a strategy that decreases the triplet energy levels of the π-conjunction bridge. A sufficient donor-acceptor interaction reduces the lowest triplet energy level and aids in the transfer of excitons from singlet to triplet levels. With this strategy, dibenzofulvene derivatives (FEs) displayed purely Type-I ROS generation. Among them, FE-TMI exhibits superior Type-I reactive oxygen species-generation performance, showcasing the great potential of PDT in treating tumor cells under hypoxic conditions and several types of solid tumors in mouse in vivo experiments. This work provides a practical solution for the future design of Type-I PDT materials and is aimed at enhancing PDT efficiency.

Supramolecular H-Aggregates of Squaraines with Enhanced Type I Photosensitization for Combined Photodynamic and Photothermal Therapy

Combined photodynamic and photothermal therapy (PDT and PTT) can achieve more superior therapeutic effects than the sole mode by maximizing the photon utilization, but there remains a significant challenge in the development of related single-molecule photosensitizers (PSs), particularly those with type I photosensitization. In this study, self-assembly of squaraine dyes (SQs) is shown to be a promising strategy for designing PSs for combined type I PDT and PTT, and a supramolecular PS (TPE-SQ7) has been successfully developed through subtle molecular design of an indolenine SQ, which can self-assemble into highly ordered H-aggregates in aqueous solution as well as nanoparticles (NPs). In contrast to the typical quenching effect of H-aggregates on reactive oxygen species (ROS) generation, our results encouragingly manifest that H-aggregates can enhance type I ROS (•OH) generation by facilitating the intersystem crossing process while maintaining a high PTT performance. Consequently, TPE-SQ7 NPs with ordered H-aggregates not only exhibit superior combined therapeutic efficacy than the well-known PS (Ce6) under both normoxic and hypoxic conditions but also have excellent biosafety, making them have important application prospects in tumor phototherapy and antibacterial fields. This study not only proves that the supramolecular self-assembly of SQs is an effective strategy toward high-performance PSs for combined type I PDT and PTT but also provides a different understanding of the effect of H-aggregates on the PDT performance.

Sonodynamic Therapy-Driven Immunotherapy: Constructing AIE Organic Sonosensitizers Using an Advanced Receptor-Regulated Strategy

Benefit from the deeper penetration of mechanical wave, ultrasound (US)-based sonodynamic therapy (SDT) executes gratifying efficacy in treating deep-seated tumors. Nevertheless, the complicated mechanism of SDT undeniably hinders the exploration of ingenious sonosensitizers. Herein, a receptor engineering strategy of aggregation-induced emission (AIE) sonosensitizers (TPA-Tpy) with acceptor (A)-donor (D)-A' structure is proposed, which inspects the effect of increased cationizations on US sensitivity. Under US stimulation, enhanced cationization in TPA-Tpy improves intramolecular charge transfer (ICT) and accelerates charge separation, which possesses a non-negligible promotion in type I reactive oxygen species (ROS) production. Moreover, abundant ROS-mediated mitochondrial oxidative stress triggers satisfactory immunogenic cell death (ICD), which further promotes the combination of SDT and ICD. Subsequently, subacid pH-activated nanoparticles (TPA-Tpy NPs) are constructed with charge-converting layer (2,3-dimethylmaleic anhydride-poly (allylamine hydrochloride)-polyethylene glycol (DMMA-PAH-PEG)) and TPA-Tpy, achieving the controllable release of sonosensitizers. In vivo, TPA-Tpy-mediated SDT effectively initiates the surface-exposed of calreticulin (ecto-CRT), dendritic cells (DCs) maturation, and CD8+ T cell infiltration rate through enhanced ROS production, achieving suppression and ablation of primary and metastatic tumors. This study provides new opinions in regulating acceptors with eminent US sensitization, and brings a novel ICD sono-inducer based on SDT to realize superior antitumor effect.

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.

Selective Tumor Inhibition Effect of Drug-Free Layered Double Hydroxide-Based Films via Responding to Acidic Microenvironment

Nickel-titanium alloy stents are widely used in the interventional treatment of various malignant tumors, and it is important to develop nickel-titanium alloy stents with selective cancer-inhibiting and antibacterial functions to avoid malignant obstruction caused by tumor invasion and bacterial colonization. In this work, an acid-responsive layered double hydroxide (LDH) film was constructed on the surface of a nickel-titanium alloy by hydrothermal treatment. The release of nickel ions from the film in the acidic tumor microenvironment induces an intracellular oxidative stress response that leads to cell death. In addition, the specific surface area of LDH nanosheets could be further regulated by heat treatment to modulate the release of nickel ions in the acidic microenvironment, allowing the antitumor effect to be further enhanced. This acid-responsive LDH film also shows a good antibacterial effect against S. aureus and E. coli. Besides, the LDH film prepared without the introduction of additional elements maintains low toxicity to normal cells in a normal physiological environment. This work offers some guidance for the design of a practical nickel-titanium alloy stent for the interventional treatment of tumors.

In situ self-assembled near-infrared phototherapeutic agent: unleashing hydrogen free radicals and coupling with NADPH oxidation

Investigation of electron transfer (ET) between photosensitizers (PSs) and adjacent substrates in hypoxic tumors is integral to highly efficient tumor therapy. Herein, the oxygen-independent ET pathway to generate hydrogen free radicals (H˙) was established by the in situ self-assembled phototherapeutic agent d-ST under near-infrared (NIR)-light irradiation, coupled with the oxidation of reduced coenzyme NADPH, which induced ferroptosis and effectively elevated the therapeutic performance in hypoxic tumors. The higher surface energy and longer exciton lifetimes of the fine crystalline d-ST nanofibers were conducive to improving ET efficiency. In hypoxic conditions, the excited d-ST can effectively transfer electrons to water to yield H˙, during which the overexpressed NADPH with rich electrons can power the electron flow to facilitate the generation of H˙, accompanied by NADP+ formation, disrupting cellular homeostasis and triggering ferroptosis. Tumor-bearing mouse models further showed that d-ST accomplished excellent phototherapy efficacy. This work sheds light onto the versatile electron pathways between PSs and biological substrates.

A NIR-II absorbing conjugated polymer based on tetra-fused isoindigo with ultrahigh photothermal conversion efficiency for cancer therapy

A conjugated polymer, P4TTD-DPP, based on tetra-fused isoindigo-alt-diketopyrrolopyrrole, has been synthesized as a photothermal therapeutic nanotransducer within the near-infrared-II (NIR-II) window. P4TTD-DPP exhibits a notable mass extinction coefficient of 62.8 L g-1 cm-1 at 1064 nm. Additionally, P4TTD-DPP nanoparticles demonstrate remarkable photothermal conversion efficiency of 91.5% at 1064 nm and exhibit excellent anticancer efficacy under photothermal conditions.

NIR-II Emissive Superoxide Radical Photogenerator for Photothermal/Photodynamic Therapy against Hypoxic Tumor

Due to the "Achilles' heels" of hypoxia, complicated location in solid tumor, small molecular photosensitizers with second near-infrared window (NIR-II) fluorescence, type-I photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted great attention. However, these photosensitizers are still few but yet challenging. Herein, an "all in one" NIR-II acceptor-donor-acceptor fused-ring photosensitizer, Y6-Th, is presented for the in-depth diagnosis and efficient treatment of cancer. Benefiting from the strong intramolecular charge transfer, promoted highly efficient intersystem crossing, largely p-conjugated fused-ring structure, and reduced planarity, the fabricated nanoparticles (Y6-Th nanoparticles) can emit NIR-II fluorescence with the peak located at 1020 nm, exclusively generate O2•- for type-I PDT, and display excellent PTT performance under an 808 nm laser stimulation. These characteristics make Y6-Th a distinguished NIR-wavelength-triggered phototheranostic agent, which can effectively therapy the hypoxic tumor using NIR-II-fluorescence-guided type-I PDT/PTT. This work provides a valuable guideline for fabricating high-performing NIR-II emissive superoxide radical photogenerators.

Confined semiconducting polymers with boosted NIR light-triggered H2O2 production for hypoxia-tolerant persistent photodynamic therapy

Hypoxia featured in malignant tumors and the short lifespan of photo-induced reactive oxygen species (ROS) are two major issues that limit the efficiency of photodynamic therapy (PDT) in oncotherapy. Developing efficient type-I photosensitizers with long-term ˙OH generation ability provides a possible solution. Herein, a semiconducting polymer-based photosensitizer PCPDTBT was found to generate 1O2, ˙OH, and H2O2 through type-I/II PDT paths. After encapsulation within a mesoporous silica matrix, the NIR-II fluorescence and ROS generation are enhanced by 3-4 times compared with the traditional phase transfer method, which can be attributed to the excited-state lifetime being prolonged by one order of magnitude, resulting from restricted nonradiative decay channels, as confirmed by femtosecond spectroscopy. Notably, H2O2 production reaches 15.8 μM min-1 under a 730 nm laser (80 mW cm-2). Further adsorption of Fe2+ ions on mesoporous silica not only improves the loading capacity of the chemotherapy drug doxorubicin but also triggers a Fenton reaction with photo-generated H2O2 in situ to produce ˙OH continuously after the termination of laser irradiation. Thus, semiconducting polymer-based nanocomposites enables NIR-II fluorescence imaging guided persistent PDT under hypoxic conditions. This work provides a promising paradigm to fabricate persistent photodynamic therapy platforms for hypoxia-tolerant phototheranostics.

Supramolecular engineering cascade regulates NIR-II J-aggregates to improve photodynamic therapy

Rational design of small organic molecule-based NIR-II photosensitizers (PSs) with high singlet oxygen quantum yield in aqueous solution for deep tissue imaging and cancer therapy still presents challenges. Herein, we devised a general synthesis strategy to obtain six NIR-II region PSs with tunable aggregation states by adjusting the steric effect, and all PSs possess longer NIR absorption/emission wavelengths with tails extending beyond 1200 nm. Notably, ATX-6 possessed a singlet oxygen quantum yield of 38.2% and exhibited concentration-dependent J-aggregation properties upon self-assembly in an aqueous solution. What's more, supramolecular engineering with DSPE-PEG2000 further enhanced its degree of J-aggregation, which was attributed to the dimer-excited reduction of the energy levels of the single-linear/triple-linear states and the facilitation of intersystem crossover processes. In addition, ATX-6 NPs showed superior photodynamic therapy effects and great potential in high-contrast in vivo bioimaging of the NIR-II region. These results provide valuable insights for achieving the diagnostic and therapeutic integration of tumors.

An NIR Type I Photosensitizer Based on a Cyclometalated Ir(III)-Rhodamine Complex for a Photodynamic Antibacterial Effect toward Both Gram-Positive and Gram-Negative Bacteria

Type I photosensitizers offer an advantage in photodynamic therapy (PDT) due to their diminished reliance on oxygen levels, thus circumventing the challenge of hypoxia commonly encountered in PDT. In this study, we present the synthesis and comprehensive characterization of a novel type I photosensitizer derived from a cyclometalated Ir(III)-rhodamine complex. Remarkably, the complex exhibits a shift in absorption and fluorescence, transitioning from "off" to "on" states in aprotic and protic solvents, respectively, contrary to initial expectations. Upon exposure to light, the complex demonstrates the effective generation of O2- and ·OH radicals via the type I mechanism. Additionally, it exhibits notable photodynamic antibacterial activity against both Gram-positive and Gram-negative bacteria, demonstrated through in vitro and in vivo experiments. This research offers valuable insights for the development of novel type I photosensitizers.

An Asymmetric NIR-II Organic Fluorophore with an Ultra-Large Stokes Shift for Imaging-Guided and Targeted Phototherapy

NIR-II imaging-guided phototherapy is an attractive, yet challenging, tumor treatment strategy. By monitoring the accumulation of phototherapy reagents at the tumor site through imaging and determining the appropriate therapy window, the therapeutic effect could be significantly improved. Probes with NIR-II (1000-1700 nm) fluorescence emission and a large Stokes shift hold great promise for fluorescence imaging with deep penetration, minimized self-quenching, and high spatiotemporal resolution. However, due to the lack of a suitable molecular framework, the design of a simple small-molecule dye with a large Stokes shift and NIR-II fluorescence emission has rarely been reported. Herein, we prepare an asymmetric D-π-A type NIR-II fluorescence probe (TBy). The probe is incapsulated in an amphiphilic polymer and modified with a fibronectin targeting peptide CREKA, which could recognize the fibrin-fibronectin complex overexpressed in multiple malignant tumors. The nanoparticles thus constructed (TByC-NPs) have maximum fluorescence emission at 1037 nm with a large Stokes shift of 426 nm, which is the largest Stokes shift among organic NIR-II fluorescent dyes reported in the literature. The TByC-NPs exhibit a good NIR-II imaging performance, active tumor targeting, and good photothermal and photodynamic capabilities. In vitro and in vivo studies verify that the TByC nanoplatform shows outstanding biocompatibility for NIR-II imaging-guided phototherapy and provides an excellent antitumor effect.

Regulating donor configuration to develop AIE-active type I photosensitizers for lipid droplet imaging and high-performance photodynamic therapy under hypoxia

Type I photodynamic therapy is considered to be a more promising cancer treatment than type II photodynamic therapy due to its non-oxygen-dependent characteristics. In this work, three D-A structure N,N'-dihydrophenazine (DHP)-based photosensitizers DP-CNPY, SMP-CNPY and DMP-CNPY were designed and synthesized by introducing different numbers of methyl groups in the backbone neighbor of DHP as the donor and combined with the typical strong electron acceptor 2-(pyridin-4-yl)acetonitrile. Among the three photosensitizers, SMP-CNPY with one methyl modification showed the best type I ROS (O2-˙, ˙OH) generation capacity and AIE performance. By encapsulation, SMP-CNPY was fabricated into nanoparticles, and SMP-CNPY NPs exhibited lipid droplet targeting ability with near-infrared (NIR) emission. Cell experiments have proved that SMP-CNPY NPs can effectively kill different kinds of cancer cells under normal oxygen conditions. Even under hypoxic and extreme hypoxic conditions, SMP-CNPY NPs can still produce ROS and kill cancer cells. This work holds significant potential in the field of type I AIE-active photosensitizers and provides a new strategy for overcoming the hypoxic dilemma in the malignant tumor microenvironment.

Expanded ROS Generation and Hypoxia Reversal: Excipient-free Self-assembled Nanotheranostics for Enhanced Cancer Photodynamic Immunotherapy

The efficacy of photodynamic therapy (PDT)-related cancer therapies is significantly restricted by two irreconcilable obstacles, i.e., low reactive oxygen species (ROS) generation capability and hypoxia which constrains the immune response. Herein, this work develops a self-assembled clinical photosensitizer indocyanine green (ICG) and the HSP90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) nanoparticles (ISDN) without any excipient. This work discovers that the hydrophobic interaction forces between ICG and 17-DMAG promote the photostability of ICG and its intersystem crossing (ISC) process, thereby improving the ROS quantum yield from 0.112 to 0.46. Augmented ROS generation enhances PDT efficacy and further enhances immunogenic cell death (ICD) effects. 17-DMAG inhibits the HSP90/hypoxia-inducible factor 1α (HIF-1α) axis to dramatically reverse the immunosuppressive tumor microenvironment caused by PDT-aggravated hypoxia. In a mouse model of pancreatic cancer, ISDN markedly improve cytotoxic T lymphocyte infiltration and MHC I and MHC II activation, demonstrating the superior ICD effects in situ tumor and the powerful systematic antitumor immunity generation, eventually achieving vigorous antitumor and recurrence resistance. This study proposes an unsophisticated and versatile strategy to significantly improve PDT efficacy for enhancing systemic antitumor immunity and potentially extending it to multiple cancers.

Smart Nanoassembly Enabling Activatable NIR Fluorescence and ROS Generation with Enhanced Tumor Penetration for Imaging-Guided Photodynamic Therapy

Fluorescence imaging-guided photodynamic therapy (FIG-PDT) holds promise for cancer treatment, yet challenges persist in poor imaging quality, phototoxicity, and insufficient anti-tumor effect. Herein, a novel nanoplatform, LipoHPM, designed to address these challenges, is reported. This approach employs an acid-sensitive amine linker to connect a biotin-modified hydrophilic polymer (BiotinPEG) with a new hydrophobic photosensitizer (MBA), forming OFF-state BiotinPEG-MBA (PM) micelles via an aggregation-caused quenching (ACQ) effect. These micelles are then co-loaded with the tumor penetration enhancer hydralazine (HDZ) into pH-sensitive liposomes (LipoHPM). Leveraging the ACQ effect, LipoHPM is silent in both fluorescence and reactive oxygen species (ROS) generation during blood circulation but restores both properties upon disassembly. Following intravenous injection in tumor-bearing mice, LipoHPM actively targets tumor cells overexpressing biotin-receptors, contributing to enhanced tumor accumulation. Upon cellular internalization, LipoHPM disassembles within lysosomes, releasing HDZ to enhance tumor penetration and inhibit tumor metastasis. Concurrently, the micelles activate fluorescence for tumor imaging and boost the production of both type-I and type-II ROS for tumor eradication. Therefore, the smart LipoHPM synergistically integrates near-infrared emission, activatable tumor imaging, robust ROS generation, efficient anti-tumor and anti-metastasis activity, successfully overcoming limitations of conventional photosensitizers and establishing itself as a promising nanoplatform for potent FIG-PDT applications.

Nature-Inspired Thylakoid-Based Photosynthetic Nanoarchitectures for Biomedical Applications

"Drawing inspiration from nature" offers a wealth of creative possibilities for designing cutting-edge materials with improved properties and performance. Nature-inspired thylakoid-based nanoarchitectures, seamlessly integrate the inherent structures and functions of natural components with the diverse and controllable characteristics of nanotechnology. These innovative biomaterials have garnered significant attention for their potential in various biomedical applications. Thylakoids possess fundamental traits such as light harvesting, oxygen evolution, and photosynthesis. Through the integration of artificially fabricated nanostructures with distinct physical and chemical properties, novel photosynthetic nanoarchitectures can be catalytically generated, offering versatile functionalities for diverse biomedical applications. In this article, an overview of the properties and extraction methods of thylakoids are provided. Additionally, the recent advancements in the design, preparation, functions, and biomedical applications of a range of thylakoid-based photosynthetic nanoarchitectures are reviewed. Finally, the foreseeable challenges and future prospects in this field is discussed.

Sulphur-atom positional engineering in perylenimide: structure-property relationships and H-aggregation directed type-I photodynamic therapy

An innovative design strategy of placing sulfur (S)-atoms within the pendant functional groups and at carbonyl positions in conventional perylenimide (PNI-O) has been demonstrated to investigate the condensed state structure-property relationship and potential photodynamic therapy (PDT) application. Incorporation of simply S-atoms at the peri-functionalized perylenimide (RPNI-O) leads to an aggregation-induced enhanced emission luminogen (AIEEgen), 2-hexyl-8-(thianthren-1-yl)-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dione (API), which achieves a remarkable photoluminescence quantum yield (Φ PL) of 0.85 in aqueous environments and established novel AIE mechanisms. Additionally, substitution of the S-atom at the carbonyl position in RPNI-O leads to thioperylenimides (RPNI-S): 2-hexyl-8-phenyl-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithione (PPIS), 8-([2,2'-bithiophen]-5-yl)-2-hexyl-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithione (THPIS), and 2-hexyl-8-(thianthren-1-yl)-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithion (APIS), with distinct photophysical properties (enlarged spin-orbit coupling (SOC) and Φ PL ≈ 0.00), and developed diverse potent photosensitizers (PSs). The present work provides a novel SOC enhancement mechanism via pronounced H-aggregation. Surprisingly, the lowest singlet oxygen quantum yield (Φ Δ) and theoretical calculation suggest the specific type-I PDT for RPNI-S. Interestingly, RPNI-S efficiently produces superoxide (O2˙-) due to its remarkably lower Gibbs free energy (ΔG) values (THPIS: -40.83 kcal mol-1). The non-toxic and heavy-atom free very specific thio-based PPIS and THPIS PSs showed selective and efficient PDT under normoxia, as a rare example.

Near-Infrared-II Nanomaterials for Activatable Photodiagnosis and Phototherapy

Near-Infrared-II (NIR-II) spans wavelengths between 1,000 to 1,700 nanometers, featuring deep tissue penetration and reduced tissue scattering and absorption characteristics, providing robust support for cancer treatment and tumor imaging research. This review explores the utilization of activatable NIR-II photodiagnosis and phototherapy based on tumor microenvironments (e. g., reactive oxygen species, pH, glutathione, hypoxia) and external stimulation (e. g., laser, ultrasound, photothermal) for precise tumor treatment and imaging. Special emphasis is placed on the advancements and advantages of activatable NIR-II nanomedicines in novel therapeutic modalities like photodynamic therapy, photothermal therapy, and photoacoustic imaging. This encompasses achieving deep tumor penetration, real-time monitoring of the treatment process, and obtaining high-resolution, high signal-to-noise ratio images even at low material concentrations. Lastly, from a clinical perspective, the challenges faced by activatable NIR-II phototherapy are discussed, alongside potential strategies to overcome these hurdles.

Thymoquinone as an electron transfer mediator to convert Type II photosensitizers to Type I photosensitizers

The development of Type I photosensitizers (PSs) is of great importance due to the inherent hypoxic intolerance of photodynamic therapy (PDT) in the hypoxic microenvironment. Compared to Type II PSs, Type I PSs are less reported due to the absence of a general molecular design strategy. Herein, we report that the combination of typical Type II PS and natural substrate carvacrol (CA) can significantly facilitate the Type I pathway to efficiently generate superoxide radical (O2-•). Detailed mechanism study suggests that CA is activated into thymoquinone (TQ) by local singlet oxygen generated from the PS upon light irradiation. With TQ as an efficient electron transfer mediator, it promotes the conversion of O2 to O2-• by PS via electron transfer-based Type I pathway. Notably, three classical Type II PSs are employed to demonstrate the universality of the proposed approach. The Type I PDT against S. aureus has been demonstrated under hypoxic conditions in vitro. Furthermore, this coupled photodynamic agent exhibits significant bactericidal activity with an antibacterial rate of 99.6% for the bacterial-infection female mice in the in vivo experiments. Here, we show a simple, effective, and universal method to endow traditional Type II PSs with hypoxic tolerance.

Recent Advances in Photosensitizer Materials for Light-Mediated Tumor Therapy

Photodynamic therapy (PDT) as an emerging therapeutic method has drawn much attention in the treatment field for cancer. Photosensitizer, which can convert photon energy into cytotoxic species under light irradiation, is the core component in PDT. The design of photosensitizers still faces problems of light absorption, targeting, penetration and oxygen dependence. With the rapid progress of material science, various photosensitizers have been developed to produce cytotoxic species for treatment of tumor with high selectivity, safety, and noninvasiveness. Besides, the applications of photosensitizers have been expanded to diverse cancer treatments such as drug release, optogenetics and immune checkpoint blockade. In this review, we summarize the recent advances of photosensitizers in various therapeutic methods for cancer. Prevailing challenges and further prospects associated with photosensitizers are also discussed.

Membrane-anchoring selenophene viologens for antibacterial photodynamic therapy against periodontitis via restoring subgingival flora and alleviating inflammation

Antibacterial photodynamic therapy (aPDT) has emerged as a promising strategy for treating periodontitis. However, the weak binding of most photosensitizers to bacteria and the hypoxic environment of periodontal pockets severely hamper the therapeutic efficacy. Herein, two novel oxygen-independent photosensitizers are developed by introducing selenophene into viologens and modifying with hexane chains (HASeV) or quaternary ammonium chains (QASeV), which improve the adsorption to bacteria through anchoring to the negatively charged cell membrane. Notably, QASeV binds only to the bacterial surface of Porphyromonas gingivalis and Fusobacterium nucleatum due to electrostatic binding, but HASeV can insert into their membrane by strong hydrophobic interactions. Therefore, HASeV exhibits superior antimicrobial activity and more pronounced plaque biofilm disruption than QASeV when combined with light irradiation (MVL-210 photoreactor, 350-600 nm, 50 mW/cm2), and a better effect on reducing the diversity and restoring the structure of subgingival flora in periodontitis rat model was found through 16S rRNA gene sequencing analysis. The histological and Micro-CT analyses reveal that HASeV-based aPDT has a better therapeutic effect in reducing periodontal tissue inflammation and alveolar bone resorption. This work provides a new strategy for the development of viologen-based photosensitizers, which may be a favorable candidate for the aPDT against periodontitis.

An NIR-II-emitting type-I photosensitizer for efficient hypoxic tumor phototheranostics

A small molecule-based NIR-II type-I photosensitizer (IT-IC) with a strong push-pull effect and good planar π-conjugated structure was synthesized. The IT-IC NPs exhibited strong light absorption, outstanding NIR-II fluorescence emission, excellent photothermal conversion and efficient type-I/II ROS generation, showing encouraging therapeutic outcomes for hypoxic tumors.

Near-Infrared Light-Driven Nanoparticles for Cancer Photoimmunotherapy by Synergizing Immune Cell Death and Epigenetic Regulation

Histone deacetylases (HDACs) are a class of epigenetic enzymes that are closely related to tumorigenesis and suppress the expression of tumor suppressor genes. Whereas the HDACs inhibitors can release DNA into the cytoplasm and trigger innate immunity. However, the high density of chromatin limits DNA damage and release. In this study, suitable nanosized CycNHOH NPs (150 nm) and CypNHOH NPs (85 nm) efficiently accumulate at the tumor site due to the enhanced permeability and retention (EPR) effect. In addition, robust single-linear oxygen generation and good photothermal conversion efficiency under NIR laser irradiation accelerated the DNA damage process. By effectively initiating immune cell death, CypNHOH NPs activated both innate and adaptive immunity by maturing dendritic cells, infiltrating tumors with natural killer cells, and activating cytotoxic T lymphocytes, which offer a fresh perspective for the development of photo-immunotherapy.

Molecular engineering to design a bright near-infrared red photosensitizer: cellular bioimaging and phototherapy

Near-infrared red (NIR) fluorescence imaging guide phototherapeutic therapy (PDT) has the advantages of deep tissue penetration, real-time monitoring of drug treatment and disease, little damage to normal tissue, low cytotoxicity and almost no side effects, and thus, it is attracting increasing research attention and is expected to show promising potential for clinical tumor treatment. The photosensitizer (PS), light source and oxygen are the three basic and important factors to construct PDT technology, and highly efficient PSs are still being passionately pursued because they determine the PDT efficiency. Ideal PSs should have properties such as good biocompatibility, deep tissue penetration, and highly efficient reactive oxygen species (ROS) generation despite the hypoxic environment. Therefore, pure organic type I PSs with NIR fluorescence have been receiving increasing attention due to their deep penetration and hypoxia resistance. However, reported NIR-active type I PSs usually require complex synthetic procedures, which presents a challenge for mass production. In this research work, based on the molecular design ideas of introducing the heavy atom effect and intramolecular charge transfer, we prepared three NIR-active type I PSs (TNZ, TNZBr, and TNZCHO) using a very simple method with one or two synthetic steps. Clear characterizations of photophysical properties, ROS performance tests, and fluorescent imaging of human umbilical vein endothelial (HUVE) cells and PDT treatment of HepG2 cells were carried out. The results revealed that the heavy atom and intramolecular charge transfer (ICT) effects could obviously enhance the ROS efficiency, and both PSs produce only type I ROS without any type II ROS (1O2) generation. The good NIR fluorescence brightness and type I ROS efficiency ensure satisfactory bioimaging and PDT outcomes. This research provides the possibility of preparing NIR-active type I PSs via mass production.

Rational design of type-I photosensitizer molecules for mitochondrion-targeted photodynamic therapy

Photodynamic therapy (PDT) has emerged as a promising approach for tumor treatment. However, traditional type II PDT faces limitations due to its oxygen-dependent nature. Type-I photosensitizers (PSs) exhibit superiority over conventional type-II PSs owing to their diminished oxygen dependence. Nevertheless, designing effective type-I PSs remains a significant challenge. In this work, we provide a novel strategy to tune the PDT mechanism of an excited photosensitizer through aryl substituent engineering. Using S-rhodamine as the base structure, three PSs were synthesized by incorporating phenyl, furyl, or thienyl groups at the meso position. Interestingly, furyl- or thienyl-substituted S-rhodamine are type-I-dominated PSs that produce O2˙-, while phenyl S-rhodamine results in O2˙- and 1O2 through type-I and type-II mechanisms, respectively. Experimental analyses and theoretical calculations showed that the introduction of a five-membered heterocycle at the meso position promoted intersystem crossing (ISC) and electron transfer, facilitating the production of O2˙-. Furthermore, furyl- or thienyl-substituted S-rhodamine exhibited high phototoxicity at ultralow concentrations. Thienyl-substituted S-rhodamine showed promising PDT efficacy against hypoxic solid tumors. This innovative strategy provides an alternative approach to developing new type-I PSs without the necessity for creating entirely new skeletons.

Deciphering Oxygen-Independent Augmented Photodynamic Oncotherapy by Facilitating the Separation of Electron-Hole Pairs

Developing Type-I photosensitizers provides an attractive approach to solve the dilemma of inadequate efficacy of photodynamic therapy (PDT) caused by the inherent oxygen consumption of traditional Type-II PDT and anoxic tumor microenvironment. The challenge for the exploration of Type-I PSs is to facilitate the electron transfer ability of photosensitization molecules for transforming oxygen or H2O to reactive oxygen species (ROS). Herein, we propose an electronic acceptor-triggered photoinduced electron transfer (a-PET) strategy promoting the separation of electron-hole pairs by marriage of two organic semiconducting molecules of a non-fullerene scaffold-based photosensitizer and a perylene diimide that significantly boost the Type-I PDT pathway to produce plentiful ROS, especially, inducing 3.5-fold and 2.5-fold amplification of hydroxyl (OH⋅) and superoxide (O2 -⋅) generation. Systematic mechanism exploration reveals that intermolecular electron transfer and intramolecular charge separation after photoirradiation generate a competent production of radical ion pairs that promote the Type-I PDT process by theoretical calculation and ultrafast femtosecond transient absorption (fs-TA) spectroscopy. By complementary tumor diagnosis with photoacoustic imaging and second near-infrared fluorescence imaging, this as-prepared nanoplatform exhibits fabulous photocytotoxicity in harsh hypoxic conditions and terrific cancer revoked abilities in living mice. We envision that this work will broaden the insight into high-efficiency Type-I PDT for cancer phototheranostics.

Supramolecular self-assembled gold nanoparticle clusters for synergistic photothermal-chemo tumor therapy

The combination of photothermal therapy and chemotherapy has emerged as a promising strategy to improve cancer therapeutic efficacy. However, developing a versatile nanoplatform that simultaneously possesses commendable photothermal effect and high drug encapsulation efficiency remains a challenging problem yet to be addressed. Herein, we report a facile supramolecular self-assembly strategy to construct gold nanoparticle clusters (AuNCs) for synergistic photothermal-chemo therapy. By utilizing the functional polysaccharide as a targeted ligand, hyaluronic acid-enriched AuNCs were endowed with targeting CD44 receptor overexpressed on the B16 cancer cells. Importantly, these hyaluronic acid modified AuNCs can shelter therapeutic cargo of doxorubicin (DOX) to aggregate larger nanoparticles via a host-guest interaction with the anchored β-cyclodextrin, as a "nanocluster-bomb" (DOX@AuNCs). The in vitro results revealed that these DOX@AuNCs showed light-triggered drug release behavior and synergistic photothermal-chemo therapy. The improved efficacy of synergistic therapy was further demonstrated by treating a xenografted B16 tumor model in vivo. We envision that our multipronged design of DOX@AuNCs provides a potent theranostic platform for precise cancer therapy and could be further enriched by introducing different imaging probes and therapeutic drugs as appropriate suitable guest molecules.

An Activatable Dual Polymer Nanosystem for Photoimmunotherapy and Metabolic Modulation of Deep-Seated Tumors

Nanomedicine in combination with immunotherapy has shown great potential in the cancer treatment, but phototherapeutic nanomaterials that specifically activate the immunopharmacological effects in deep tumors have rarely been developed due to limited laser penetration depth and tumor immune microenvironment. Herein, this work reports a newly synthesized semiconducting polymer (SP) grafted with imiquimod R837 and indoxmid encapsulated micelle (SPRIN-micelle) with strong absorption in the second near infrared window (NIR-II) that can relieve tumor immunosuppression and enhance the photothermal immunotherapy and catabolic modulation on tumors. Immune agonists (Imiquimod R837) and immunometabolic modulators (indoxmid) are covalently attached to NIR-II SP sensors via a glutathione (GSH) responsive self-immolation linker and then loaded into Pluronic F127 (F127) micelles by a temperature-sensitive critical micelle concentration (CMC)-switching method. Using this method, photothermal effect of SPRIN-micelles in deep-seated tumors can be activated, leading to effective tumor ablation and immunogenic cell death (ICD). Meanwhile, imiquimod and indoxmid are tracelessly released in response to the tumor microenvironment, resulting in dendritic cell (DC) maturation by imiquimod R837 and inhibition of both indoleamine 2,3-dioxygenase (IDO) activity and Treg cell expression by indoxmid. Ultimately, cytotoxic T-lymphocyte infiltration and tumor metastasis inhibition in deep solid tumors (9 mm) are achieved. In summary, this work demonstrates a new strategy for the combination of photothermal immunotherapy and metabolic modulation by developing a dual functional polymer system including activable SP and temperature-sensitive F127 for the treatment of deep solid tumors.

End Group Engineering for Constructing A-D-A Fused-Ring Photosensitizers with Balanced Phototheranostics Performance

Phototheranostics continues to flourish in cancer treatment. Due to the competitive relationships between these photophysical processes of fluorescence emission, photothermal conversion, and photodynamic action, it is critical to balance them through subtle photosensitizer designs. Herein, it is provided a useful guideline for constructing A-D-A photosensitizers with superior phototheranostics performance. Various cyanoacetate group-modified end groups containing ester side chains of different length are designed to construct a series of A-D-A photosensitizers (F8CA1 ∼ F8CA4) to study the structure-property relationships. It is surprising to find that the photophysical properties of A-D-A photosensitizers can be precisely regulated by these tiny structural changes. The results reveal that the increase in the steric hindrance of ester side chains has positive impacts on their photothermal conversion capabilities, but adverse impacts on the fluorescence emission and photodynamic activities. Notably, these tiny structural changes lead to their different aggregation behavior. The molecule mechanisms are detailedly explained by theoretical calculations. Finally, F8CA2 nanoparticles with more balanced photophysical properties perform well in fluorescence imaging-guided photothermal and type I&II photodynamic synergistic cancer therapy, even under hypoxic conditions. Therefore, this work provides a novel practicable construction strategy for desired A-D-A photosensitizers.

Cancer-Thylakoid Hybrid Membrane Camouflaged Thulium Oxide Nanoparticles with Oxygen Self-Supply Capability for Tumor-Homing Phototherapy

Nanomaterials that generate reactive oxygen species (ROS) upon light irradiation have significant applications in various fields, including photodynamic therapy (PDT) that is widely recognized as a highly momentous strategy for the eradication of cancer cells. However, the ROS production rate of photosensitizers, as well as the tumor hypoxia environment, are two major challenges that restrict the widespread application of PDT. In this study, a cancer-thylakoid hybrid membrane-camouflaged thulium oxide nanoparticles (Tm2O3) for tumor-homing phototherapy through dual-stage-light-guided ROS generation and oxygen self-supply is developed. Tm2O3 as a type II photosensitizer are viable for NIR-stimulated ROS generation due to the unique energy levels, large absorption cross section, and long lifetime of the 3H4 state of Tm ions. The thylakoid membrane (TK) plays a catalase-like role in converting hydrogen peroxide into oxygen and also acts as a natural photosensitizer that can generate lethal ROS through electron transfer when exposed to light. In addition, fluorescence dye DiR is embedded in the hybrid membrane for in vivo tracing as well as photothermal therapy. Results show that tumors in Tm2O3@TK-M/DiR group are effectively ablated following dual-stage-light irradiation, highlighting the promising potential of rare-earth element-based type II photosensitizers in various applications.

Oxygen-independent organic photosensitizer with ultralow-power NIR photoexcitation for tumor-specific photodynamic therapy

Photodynamic therapy (PDT) is a promising cancer treatment but has limitations due to its dependence on oxygen and high-power-density photoexcitation. Here, we report polymer-based organic photosensitizers (PSs) through rational PS skeleton design and precise side-chain engineering to generate •O2- and •OH under oxygen-free conditions using ultralow-power 808 nm photoexcitation for tumor-specific photodynamic ablation. The designed organic PS skeletons can generate electron-hole pairs to sensitize H2O into •O2- and •OH under oxygen-free conditions with 808 nm photoexcitation, achieving NIR-photoexcited and oxygen-independent •O2- and •OH production. Further, compared with commonly used alkyl side chains, glycol oligomer as the PS side chain mitigates electron-hole recombination and offers more H2O molecules around the electron-hole pairs generated from the hydrophobic PS skeletons, which can yield 4-fold stronger •O2- and •OH production, thus allowing an ultralow-power photoexcitation to yield high PDT effect. Finally, the feasibility of developing activatable PSs for tumor-specific photodynamic therapy in female mice is further demonstrated under 808 nm irradiation with an ultralow-power of 15 mW cm-2. The study not only provides further insights into the PDT mechanism but also offers a general design guideline to develop an oxygen-independent organic PS using ultralow-power NIR photoexcitation for tumor-specific PDT.

Photo-Induced Disproportionation-Mediated Photodynamic Therapy: Simultaneous Oxidation of Tetrahydrobiopterin and Generation of Superoxide Radicals

We herein present an approach of photo-induced disproportionation for preparation of Type-I photodynamic agents. As a proof of concept, BODIPY-based photosensitizers were rationally designed and prepared. The photo-induced intermolecular electron transfer between homotypic chromophores leads to the disproportionation reaction, resulting in the formation of charged intermediates, cationic and anionic radicals. The cationic radicals efficiently oxidize the cellularimportant coenzyme, tetrahydrobiopterin (BH4 ), and the anionic radicals transfer electrons to oxygen to produce superoxide radicals (O2 - ⋅). One of our Type-I photodynamic agents not only self-assembles in water but also effectively targets the endoplasmic reticulum. It displayed excellent photocytotoxicity even in highly hypoxic environments (2 % O2 ), with a half-maximal inhibitory concentration (IC50 ) of 0.96 μM, and demonstrated outstanding antitumor efficacy in murine models bearing HeLa tumors.

Galactosyl BODIPY-based nanoparticles as a type-I photosensitizer for HepG2 cell targeted photodynamic therapy

We report a galactosyl diiodo-BODIPY-based nanoparticles as type-I photosensitizer (PS) with high water solubility for HepG2 cell targeted photodynamic therapy. Functionalized galactoside and glucoside were introduced into diiodo-BODIPY to obtain BP1 and BP2, respectively. The glycolyl PSs could self-assemble to form the nanoparticles BP1-NP and BP2-NP with red-shifted near-infrared (NIR) absorption and fluorescence at 682 nm and 780 nm, as well as excellent chemo- and photo-stability. In comparison to the monomer in DMSO, the aggregated photosensitizers in the nanoparticles enabled the sensitization of oxygen to superoxide (O2˙-) through a type-I process, while repressing the generation of singlet oxygen (1O2) through a type-II process. The galactosyl-modified BP1-NPs could target and concentrate on HepG2 cells, subsequently generating O2˙- and 1O2 to trigger cell death under 660 nm light irradiation. This work provides an efficient strategy for the construction of glycoside-recognized type-I photosensitizers for tumor cell imaging and photodynamic therapy.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Enhancing near-infrared II photodynamic therapy with nitric oxide for eradicating multidrug-resistant biofilms in deep tissues

Nitric oxide (NO) enhanced photodynamic therapy (PDT) is a promising approach to overcome drug tolerance and resistance to biofilm but is limited by its short excitation wavelengths and low yield of reactive oxygen species (ROS). Herein, we develop a compelling degradable polymer-based near-infrared II (NIR-II, 1000-1700 nm) photosensitizer (PNIR-II), which can maintain 50 % PDT efficacy even under a 2.6 cm tissue barrier. Remarkably, PNIR-II is synthesized by alternately connecting the electron donor thiophene to the electron acceptors diketopyrrolopyrrole (DPP) and boron dipyrromethene (BODIPY), where the intramolecular charge transfer properties can be tuned to increase the intersystem crossover rate and decrease the internal conversion rate, thereby stabilizing the NIR-II photodynamic rather than photothermal effect. For exerting a combination therapy to eradicate multidrug-resistant biofilms, PNIR-II is further assembled into nanoparticles (NPs) with a synthetic glutathione-triggered NO donor polymer. Under 1064 nm laser radiation, NPs precisely release ROS and NO that triggered by over-expressed GSH in the biofilm microenvironment, thereby forming more bactericidal reactive nitrogen species (RNS) in vitro and in vivo in the mice model that orderly destroy biofilm of multidrug-resistant Staphylococcus aureus cultures from clinical patients. It thus provides a new outlook for destroy the biofilm of deep tissues.

Engineered Extracellular Vesicles Expressing Siglec-10 Camouflaged AIE Photosensitizer to Reprogram Macrophages to Active M1 Phenotype and Present Tumor-Associated Antigens for Photodynamic Immunotherapy

Cancer immunotherapy has attracted considerable attention due to its advantages of persistence, targeting, and ability to kill tumor cells. However, the efficacy of tumor immunotherapy in practical applications is limited by tumor heterogeneity and complex tumor immunosuppressive microenvironments in which abundant of M2 macrophages and immune checkpoints (ICs) are present. Herein, two type-I aggregation-induced emission (AIE)-active photosensitizers with various reactive oxygen species (ROS)-generating efficiencies are designed and synthesized. Engineered extracellular vesicles (EVs) that express ICs Siglec-10 are first obtained from 4T1 tumor cells. The engineered EVs are then fused with the AIE photosensitizer-loaded lipidic nanosystem to form SEx@Fc-NPs. The ROS generated by the inner type-I AIE photosensitizer of the SEx@Fc-NPs through photodynamic therapy (PDT) can convert M2 macrophages into M1 macrophages to improve tumor immunosuppressive microenvironment. The outer EV-antigens that carry 4T1 tumor-associated antigens directly stimulate dendritic cells maturation to activate different types of tumor-specific T cells in overcoming tumor heterogeneity. In addition, blocking Siglec-10 reversed macrophage exhaustion for enhanced antitumor ability. This study presents that a combination of PDT, immune checkpoints, and EV-antigens can greatly improve the efficiency of tumor immunotherapy and is expected to serve as an emerging strategy to improve tumor immunosuppressive microenvironment and overcome immune escape.

Toward Type I/II ROS Generation Photoimmunotherapy by Molecular Engineering of Semiconducting Perylene Diimide

As prospective phototheranostic agents for cancer imaging and therapy, semiconducting organic molecule-based nanomedicines are developed. However, near-infrared (NIR) emission, and tunable type I (O2 • -) and type II (1O2) photoinduced reactive oxygen species (ROS) generation to boost cancer photoimmunotherapy remains a big challenge. Herein, a series of D-π-A structures, NIR absorbing perylene diimides (PDIs) with heavy atom bromide modification at the bay position of PDIs are prepared for investigating the optimal photoinduced type I/II ROS generation. The heavy atom effect has demonstrated a reduction of molecular ∆EST and promotion of the intersystem crossing processes of PDIs, enhancing the photodynamic therapy (PDT) efficacy. The modification of three bromides and one pyrrolidine at the bay position of PDI (TBDT) has demonstrated the best type I/II PDT performance by batch experiments and theoretical calculations. TBDT based nanoplatforms (TBDT NPs) enable type I/II PDT in the hypoxic tumor microenvironment as a strong immunogenic cell death (ICD) inducer. Moreover, TBDT NPs showing NIR emission allow in vivo bioimaging guided phototherapy of tumor. This work uses novel PDIs with adjustable type I/II ROS production to promote antitumor immune response and accomplish effective tumor eradication, consequently offering molecular guidelines for building high-efficiency ICD inducers.

A Single NIR-II Laser-Triggered Self-Enhancing Photo/Enzyme-coupled Three-in-One Nanosystems for Breast Cancer Phototheranostics

Multifunctional phototheranostics, employing precise and non-invasive techniques, is widely developed to enhance theranostic efficiency of breast cancer (BC), reduce side-effects, and improve quality of life. Integrating all phototheranostic modalities into a single photosensitizer for highly effective BC treatment is particularly challenging due to the potential inefficiency and time consumption associated with repeated switching of multiple-wavelength lasers. Herein, a novel single NIR-II laser-triggered three-in-one nanosystem(PdCu NY) is rationally designed, which enables dual-modal (NIR-II FL/NIR-II PA) imaging-guided self-enhancing photothermal-photodynamic therapy (PTT-PDT) in NIR-II window. The PdCu NY based on optimal Pd/Cu molar-ratio(1:11) can be easily fabricated and large-scale production for simultaneous PTT-PDT against BC under a single 1064nm laser irradiation. Significantly, the PdCu NY acted as a promising photocatalyst for decomposition of H2O into O2 upon the same laser irradiation. In addition, the inherent catalase (CAT)-like activity of PdCu NYs enables photo-enzyme dual-catalytic O2 supply to effectively alleviate hypoxia, achieving self-enhanced PDT efficiency. These PTT-PDT self-enhanced nanosystems demonstrate precise lesion localization and complete tumor ablation using a single 1064nm laser source by "one-laser, multi-functions" strategy. More importantly, this study not only reports a three-in-one PdCu-based phototheranostic agent, but also sheds light on the exploration of versatile biosafety nanosystems for clinical applications.

A Self-Assembly-Induced Exciton Delocalization Strategy for Converting a Perylene Diimide Derivative from a Type-II to Type-I Photosensitizer

Type-I photosensitizers have shown advantages in addressing the shortcomings of traditional oxygen-dependent type-II photosensitizers for the photodynamic therapy (PDT) of hypoxic tumors. However, developing type-I photosensitizers is yet a huge challenge because the type-II energy transfer process is much faster than the type-I electron transfer process. Herein, from the fundamental point of view, an effective approach is proposed to improve the electron transfer efficiency of the photosensitizer by lowering the internal reorganization energy and exciton binding energy via self-assembly-induced exciton delocalization. An example proof is presented by the design of a perylene diimide (PDI)-based photosensitizer (PDIMp) that can generate singlet oxygen (1O2) via a type-II energy transfer process in the monomeric state, but induce the generation of superoxide anion (O2˙-) via a type-I electron transfer process in the aggregated state. Significantly, with the addition ofcucurbit[6]uril (CB[6]), the self-assembled PDIMp can convert back to the monomeric state via host-guest complexation and consequently recover the generation of 1O2. The biological evaluations reveal that supramolecular nanoparticles (PDIMp-NPs) derived from PDIMp show superior phototherapeutic performance via synergistic type-I PDT and mild photothermal therapy (PTT) against cancer under either normoxia or hypoxia conditions.

Dye-augmented bandgap engineering of a degradable cascade nanoreactor for tumor immune microenvironment-enhanced dynamic phototherapy of breast cancer

Non-invasive precision tumor dynamic phototherapy has broad application prospects. Traditional semiconductor materials have low photocatalytic activity and low reactive oxygen species (ROS) production rate due to their wide band gap, resulting in unsatisfactory phototherapy efficacy for tumor treatment. Employing the dye-sensitization mechanism can significantly enhance the catalytic activity of the materials. We develop a multifunctional nanoplatform (BZP) by leveraging the benefits of bismuth-based semiconductor nanomaterials. BZP possesses robust ROS generation and remarkable near-infrared photothermal conversion capabilities for improving tumor immune microenvironment and achieving superior phototherapy sensitization. BZP produces highly cytotoxic ROS species via the photocatalytic process and cascade reaction, amplifying the photocatalytic therapy effect. Moreover, the simultaneous photothermal effect during the photocatalytic process facilitates the improvement of therapeutic efficacy. Additionally, BZP-mediated phototherapy can trigger the programmed death of tumor cells, stimulate dendritic cell maturation and T cell activation, modulate the tumor immune microenvironment, and augment the therapeutic effect. Hence, this study demonstrates a promising research paradigm for tumor immune microenvironment-improved phototherapy. STATEMENT OF SIGNIFICANCE: Through the utilization of dye sensitization and rare earth doping techniques, we have successfully developed a biodegradable bismuth-based semiconductor nanocatalyst (BZP). Upon optical excitation, the near-infrared dye incorporated within BZP promptly generates free electrons, which, under the influence of the Fermi energy level, undergo transfer to BiF3 within BZP, thereby facilitating the effective separation of electron-hole pairs and augmenting the catalytic capability for reactive oxygen species (ROS) generation. Furthermore, a cascade reaction mechanism generates highly cytotoxic ROS, which synergistically depletes intracellular glutathione, thereby intensifying oxidative stress. Ultimately, this dual activation strategy, combining oxidative and thermal damage, holds significant potential for tumor immunotherapy.

Multifunctional agents based on 3-dicycanovinylindan-1-one acceptor: Molecular design and phototheranostic application

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has garnered considerable attention in recent years, owing to its precise spatiotemporal accuracy with minimal side effects. Recent research reveals that the combination of PDT and PTT exhibits a remarkable anti-tumor efficacy compared to PDT or PTT alone, which has put forward the new requirements of multifunctional phototherapy agents with both high photosensitization and photothermal conversion efficiencies. Among the newly developed multifunctional agents, the ones with one or two 3-dicycanovinylindan-1-one (IC) moieties as the acceptors attract much more attention, due to their long-wavelength excitation and emission, as well as high phototherapy efficacies. Therefore, in this review, the latest advancement of multifunctional agents based on IC acceptor is summarized. Especially, we focus on the structure-property relationships of the agents, as well as their biomedical application in anti-tumor therapy or image-guided therapy. Our perspective on the further future development of this field is also discussed to conclude.