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

A Type I Photosensitizer-Polymersome Boosts Reactive Oxygen Species Generation by Forcing H-Aggregation for Amplifying STING Immunotherapy

Activation of the innate immune Stimulator of Interferon Genes (STING) pathway potentiates antitumor immunity. However, delivering STING agonists systemically to tumors presents a formidable challenge, and resistance to STING monotherapy has emerged in clinical trials with diminishing natural killer (NK) cell proliferation. Here, we encapsulated the STING agonist diABZI within polymersomes containing a Type I photosensitizer (NBS), creating a nanoagonist (PNBS/diABZI) for highly responsive tumor immunotherapy. This structure promoted H-aggregation and intersystem crossing of NBS, resulting in a ∼ 3-fold amplification in superoxide anion and singlet oxygen generation. The photodynamic therapy directly damaged hypoxia tumor cells and stimulated the proliferation of NK cells and cytotoxic T lymphocytes, thereby sensitizing STING immunotherapy. A single systemic intravenous administration of PNBS/diABZI eradicated orthotopic mammary tumors in murine models, achieving long-term antitumor immune memory to inhibit tumor recurrence and metastasis and significantly improving long-term tumor-free survival. This work provides a design rule for boosting reactive oxygen species production by promoting the intersystem crossing process, highlighting the potential of Type I photosensitizer-polymer vehicles for augmenting STING immunotherapy.

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.

Fiber Optic-Mediated Type I Photodynamic Therapy of Brain Glioblastoma Based on an Aggregation-Induced Emission Photosensitizer

Glioblastoma (GBM) is one of the most lethal human malignancies. The current standard-of-care is highly invasive with strong toxic side effects, leading to poor prognosis and high mortality. As a safe and effective clinical approach, photodynamic therapy (PDT) has emerged as a suitable option for GBM. Nevertheless, its implementation is significantly impeded by the limits of light penetration depth and the firm reliance on oxygen. To overcome these challenges, herein, a promising strategy that harnesses a modified optical fiber and less oxygen-dependent Type I aggregation-induced emission (AIE) photosensitizer (PS) is developed for the first time to realize in vivo GBM treatments. The proposed AIE PS, namely TTTMN, characterized by a highly twisted molecular architecture and a bulky spacer, exhibits enhanced near-infrared emission and strong production of hydroxyl and superoxide radicals at the aggregated state, thus affording efficient fluorescence imaging-guided PDT once formulated into nanoparticles. The inhibition of orthotopic and subcutaneous GBM xenografts provides compelling evidence of the treatment efficacy of Type I PDT irradiated through a tumor-inserted optical fiber. These findings highlight the substantially improved therapeutic outcomes achieved through fiber optic-mediated Type I PDT, positioning it as a promising therapeutic modality for GBM.

Thiophene assisted cellular uptake enhancement for highly efficient NIR-II cancer phototheranostics

We designed two series of NIR-II PTAs with D-A or D-A-D structures, in which the introduction of thiophene promotes a bathochromic shift of emission into the NIR-II region, helps to improve the cellular uptake of the PTAs and facilitates NIR-II imaging-guided PDT/PTT cancer phototherapy.

Unraveling non-radiative decay channels of exciplexes to construct efficient red emitters for organic light-emitting diodes

Exciplex emitters naturally have thermally activated delayed fluorescence characteristics due to their spatially separated molecular orbitals. However, the intermolecular charge transfer potentially induces diverse non-radiative decay channels, severely hindering the construction of efficient red exciplexes. Thus, a thorough comprehension of this energy loss is of paramount importance. Herein, different factors, including molecular rigidity, donor-acceptor interactions and donor-donor/acceptor-acceptor interactions, that impact the non-radiative decay were systematically investigated using contrasting exciplex emitters. The exciplex with rigid components and intermolecular hydrogen bonds showed a photoluminescence quantum yield of 84.1% and a singlet non-radiative decay rate of 1.98 × 106 s-1 at an optimized mixing ratio, respectively, achieving a 3.3-fold increase and a 70% decrease compared to the comparison group. In the electroluminescent device, a maximum external quantum efficiency of 23.8% was achieved with an emission peak of 608 nm, which represents the state-of-the-art organic light-emitting diodes using exciplex emitters. Accordingly, a new strategy is finally proposed, exploiting system rigidification to construct efficient red exciplex emitters that suppress non-radiative decay.

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.

A near-infrared broad-spectrum antimicrobial nanoplatform powered by bacterial metabolic activity for enhanced antimicrobial photodynamic-immune therapy

The emergence of antimicrobial-resistant bacterial infections poses a significant threat to public health, necessitating the development of innovative and effective alternatives to antibiotics. Photodynamic therapy (PDT) and immunotherapy show promise in combating bacteria. However, PDT's effectiveness is hindered by its low specificity to bacteria, while immunotherapy struggles to eliminate bacteria in immunosuppressive environments. In this work, we introduce an innovative near-infrared antimicrobial nanoplatform (ZFC) driven by bacterial metabolism. ZFC, comprising d-cysteine-functionalized pentafluorophenyl bacteriochlorin (FBC-Cy) coordinated with Zn2+, is designed for antimicrobial photodynamic-immune therapy (aPIT) against systemic bacterial infections. By specifically targeting bacteria via d-amino acid incorporation into bacterial surface peptidoglycans during metabolism, ZFC achieves precise bacterial clearance in wound and pulmonary infections, exhibiting an antimicrobial efficacy of up to 90 % with minimal damage to normal cells under 750 nm light. Additionally, ZFC enhances the activation of antigen-presenting cells by 3.2-fold compared to control groups. Furthermore, aPIT induced by ZFC triggers systemic immune responses and establishes immune memory, resulting in a 1.84-fold increase in antibody expression against bacterial infections throughout the body of mice. In conclusion, aPIT prompted by ZFC presents a approach to treating bacterial infections, offering a broad-spectrum solution for systemic bacterial infections. STATEMENT OF SIGNIFICANCE: The new concept demonstrated focuses on an innovative near-infrared antimicrobial nanoplatform (ZFC) for antimicrobial photodynamic-immune therapy (aPIT), highlighting its reliance on bacterial metabolism and its non-damaging effect on normal tissues. ZFC efficiently targets deep-tissue bacterial infections by harnessing bacterial metabolism, thereby enhancing therapeutic efficacy while sparing normal tissues from harm. This approach not only clears bacterial infections effectively but also induces potent adaptive immune responses, leading to the eradication of distant bacterial infections. By emphasizing ZFC's unique mechanism driven by bacterial metabolism and its tissue-sparing properties, this work underscores the potential for groundbreaking advancements in antimicrobial therapy. Such advancements hold promise for minimizing collateral damage to healthy tissues, thereby improving treatment outcomes and mitigating the threat of antimicrobial resistance. This integrated approach represents a significant progress forward in the development of next-generation antimicrobial therapies with enhanced precision and efficacy.

An Intramolecular Rotor-Bridged Dimeric Cyanine Photothermal Transducer for Efficient Near-Infrared II Fluorescence Imaging-Guided Mitochondria-Targeted Phototherapy

Near-infrared (NIR) heptamethine cyanine (HCy) dyes are promising photothermal transducers for image-guided cancer treatment owing to their prominent photophysical properties and high photothermal conversion ability. However, HCy photothermal transducers usually have poor photostability due to degradation induced by the self-generated reactive oxygen species. Herein, a novel mitochondria-targeting dimeric HCy dye, named dimeric oBHCy, is rationally designed, exhibiting strong near-infrared II (NIR-II) fluorescence emission, high photothermal conversion efficiency (PCE), and excellent photostability. The large π-conjugation and drastic intramolecular motion of the diphenol rotor in the dimeric oBHCy enhance the nonradiative energy dissipation and suppress the intersystem crossing process, thereby achieving a high PCE (49.2%) and improved photostability. Impressively, dimeric oBHCy can precisely target mitochondria and induce mitochondrial damage upon NIR light irradiation. Under the guidance of in vivo NIR-II fluorescence imaging, efficient NIR light-activated photothermal therapy of 4T1 breast tumors is accomplished with a tumor inhibitory rate of 96% following a single injection of the dimeric oBHCy. This work offers an innovative strategy for designing cyanine photothermal transducers with integrated NIR-II fluorescence and photothermal properties for efficient cancer theranostics.

Resonance-Induced Dynamic Triplet Exciton Population for Photoactivated Organic Ultralong Room Temperature Phosphorescence

Dynamically populating triplet excitons under external stimuli is desired to develop smart optoelectronic materials, but it remains a formidable challenge. Herein, we report a resonance-induced excited state regulation strategy to dynamically modulate the triplet exciton population by introducing a self-adaptive N-C═O structure to phosphors. The developed phosphors activated under high-power ultraviolet irradiation exhibited enhanced photoactivated organic ultralong room temperature phosphorescence (PA-OURTP) with lifetimes of up to ∼500 ms. The enhanced PA-OURTP was ascribed to activated N-C═O resonance variation-induced intersystem crossing to generate excess triplet excitons. The excellent PA-OURTP performance and ultralong deactivation time under ambient conditions of the developed materials could function as a reusable recorded medium for time-sensitive information encryption through optical printing. This study provides an effective approach to dynamically regulating triplet excitons and offers valuable guidance to develop high-performance PA-OURTP materials for security printing applications.

Efficient hydroxyl radical generation of an activatable phthalocyanine photosensitizer: oligomer higher than monomer and nanoaggregate

It remains a challenge to develop a single-component organic photosensitizer that efficiently produces hydroxyl radicals (˙OH) without oxygen involvement, especially while maintaining tumor-targeting capability. Herein, we propose an intelligent molecular design strategy whereby a tumor-targeted phthalocyanine is initially ˙OH-free and can be activated by overexpressed β-nicotinamide adenine dinucleotide sodium salt hydrate (NAD(P)H) in hypoxic tumors to efficiently produce ˙OH under light irradiation. Furthermore, the oligomer models based on the phthalocyanine molecules were constructed by a supramolecular regulation strategy, which were in an intermediate state between monomer and nanoaggregate, to achieve enhanced ˙OH generation. The level of NAD(P)H in cancer cells can be exhausted through two pathways, including spontaneous redox and the photocatalytic redox of phthalocyanines. As a result, the in vivo and in vitro assays illustrated that the oligomeric phthalocyanine containing N-O units (OligPcNOB) can specifically target cancer cells and tumor tissue with overexpressing biotin receptors. OligPcNOB exhibited significant photocytotoxicity even in an extremely low oxygen environment and successfully inhibited tumor progression.

A planar electronic acceptor motif contributing to NIR-II AIEgen with combined imaging and therapeutic applications

Designing molecules with donor-acceptor-donor (D-A-D) architecture plays an important role in obtaining second near-infrared region (NIR-II, 1000-1700 nm) fluorescent dyes for biomedical applications; however, this always comes with a challenge due to very limited electronic acceptors. On the other hand, to endow NIR-II fluorescent dyes with combined therapeutic applications, trivial molecular design is indispensable. Herein, we propose a pyrazine-based planar electronic acceptor with a strong electron affinity, which can be used to develop NIR-II fluorescent dyes. By structurally attaching two classical triphenylamine electronic donors to it, a basic D-A-D module, namely Py-NIR, can be generated. The planarity of the electronic acceptor is crucial to induce a distinct NIR-II emission peaking at ∼1100 nm. The unique construction of the electronic acceptor can cause a twisted and flexible molecular conformation by the repulsive effect between the donors, which is essential to the aggregation-induced emission (AIE) property. The tuned intramolecular motions and twisted D-A pair brought by the electronic acceptor can lead to a remarkable photothermal conversion with an efficiency of 56.1% and induce a type I photosensitization with a favorable hydroxyl radical (OH˙) formation. Note that no additional measures are adopted in the molecular design, providing an ideal platform to realize NIR-II fluorescent probes with synergetic functions based on such an acceptor. Besides, the nanoparticles of Py-NIR can exhibit excellent NIR-II fluorescence imaging towards orthotopic 4T1 breast tumors in living mice with a high sensitivity and contrast. Combined with photothermal imaging and photoacoustic imaging caused by the thermal effect, the imaging-guided photoablation of tumors can be well performed. Our work has created a new opportunity to develop NIR-II fluorescent probes for accelerating biomedical applications.

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.

Deepened Photodynamic Therapy through Skin Optical Clearing Technology in the Visible Light Window

The trade-off that shorter wavelength light facilitates the efficient generation of reactive oxygen species (ROS) from photosensitizer (PS) while facing the drawback of limited penetration depth through skin tissue restricts the further development of photodynamic therapy (PDT). Here, we address this contradiction and achieve visible-light-tailored deep PDT combined with the skin optical clearing technology. With the help of the prepared skin optical clearing gel, the refractive index inhomogeneity between skin tissue components is greatly attenuated, and the light scattering effect within the skin tissue is remarkably reduced. As a consequence, the transmittance of visible light at 600 nm through in vitro porcine skin and in vivo mouse skin after treatment increases from approximately 10 and 40 to 70 and 70%, respectively. Furthermore, in the tumor cell eradication experiment, the local ROS generation efficiency in the experimental group is several times higher than that in the control group owing to improved visible transmittance, which is thus responsible for the complete eradication of tumor cells, even when shaded by skin tissue. The results suggest that this strategy may serve as a valuable supplement to the current deep PDT strategies.

A novel polymer enabled by polymerized small molecule strategy for tumor photothermal and photodynamic therapy

Photothermal therapy (PTT) and photodynamic therapy (PDT) are effective method for tumor treatment. However, the limited variety and quantity of photothermal agents (PTAs) and photosensitizer (PSs) are still major challenges. Moreover, the cell apoptosis mechanism induced by PDT and PTT is still elusive. A fused-ring small molecule acceptor-donor acceptor' donor-acceptor (A-DA'D-A) type of Y5 (Scheme 1) has a narrow band-gap and strong light absorption. Herein, we used Y5 to polymerize with thiophene unit to obtain polymer PYT based on polymerized small molecule strategy, and PYT nanoparticles (PYT NPs) was prepared via one-step nanoprecipitation strategy with DSPE-PEG2000. PYT NPs had excellent biocompatibility, good photostability, high photothermal conversion efficiency (67%) and reactive oxygen species (ROS) production capacity under 808 nm laser irradiation (PYT NPs + NIR). In vitro and in vivo experiments revealed that PYT NPs + NIR had the ability to completely ablate tumor cells. It was demonstrated that cell apoptosis induced by PYT NPs + NIR was closely related to mitochondrial damage. This study provides valuable guidance for constructing high-performance organic PTAs and PSs for tumor treatment. Scheme 1 PYT enabled by polymerized small molecule strategy for tumor photothermal and photodynamic therapy.

Dual-Mechanism Tuned Engineered Polyphenols with Cascade Photocatalytic Self-Fenton Reaction for Sustainable Biocidal Coatings

Traditional disposable personal protective equipment (PPE) only blocks pathogenic bacteria by mechanical filtration, with the risk of recontamination and transmission remaining. Herein, inspired by phenolic-enabled nanotechnology (PEN), we proposed engineered polyphenol coatings by plant-derived aromatic aldehydes and metal involvement, denoted as FQM, to obtain the desired photocatalysis-self-Fenton antibacterial performance. Experiments and theoretical analysis proved the dual mechanism of Fe-induced enhancement: (1) tuning of molecular structure realized improved optical properties; (2) Fe(III)/Fe(II) triggered photocatalytic cascade self-Fenton reaction. Mechanism study reveals FQM killing bacteria by direct-contact ROS attack and gene regulation. Further, the FQM was developed as the ideal antibacterial coating on different fabrics (cloth cotton, polyester, and N95 mask), killing more than 93% of bacteria after 5 cycles of use. Such photocatalysis-self-Fenton coatings based on engineered polyphenols endowed with desirable safety, sustainability, and efficient antibacterial features are promising solutions to meet the challenges of the currently available PPE.