Dimensional Reduction Enhances Photodynamic Therapy of Metal-Organic Nanophotosensitizers

A self-powered theranostic DNA nanodevice for amplification of both intracellular microRNA imaging and photodynamic therapy

While numerous methods exist for diagnosing tumors through the detection of miRNA within tumor cells, few can simultaneously achieve both tumor diagnosis and treatment. In this study, a novel graphene oxide (GO)-based DNA nanodevice (DND), initiated by miRNA, was developed for fluorescence signal amplification imaging and photodynamic therapy in tumor cells. After entering the cells, tumor-associated miRNA drives DND to Catalyzed hairpin self-assembly (CHA). The CHA reaction generated a multitude of DNA Y-type structures, resulting in a substantial amplification of Ce6 fluorescence release and the generation of numerous singlet oxygen (1O2) species induced by laser irradiation, consequently inducing cell apoptosis. In solution, DND exhibited high selectivity and sensitivity to miRNA-21, with a detection limit of 11.47 pM. Furthermore, DND discriminated between normal and tumor cells via fluorescence imaging and specifically generated O21 species in tumor cells upon laser irradiation, resulting in tumor cells apoptosis. The DND offer a new approach for the early diagnosis and timely treatment of malignant tumors.

Engineered cyanobacteria-Fe3O4 hybrid system as oxygen generator and photosensitizer production factory for synergistic cancer PDT-immunotherapy

The combination of photodynamic therapy (PDT)-immunotherapy has brought much hope for cancer patients. However, the hypoxia tumor microenvironment (TME) can regulate tumor angiogenesis and inhibit immune response, thus limiting the therapeutic effects. In this paper, engineered cyanobacteria-M2-like tumor-associated macrophages (TAMs) targeting peptide modified Fe3O4 nanoparticles hybrid system (ECyano@Fe3O4-M2pep) was constructed for alleviating hypoxia and relieving immune suppression to achieve synergistic cancer PDT-immunotherapy. With the irradiation of red laser, oxygen was produced by the photosynthesis of ECyano to alleviate the hypoxia TME. Then, ECyano could secret 5-aminolevulinic acid (5-ALA) under the induction of theophylline for controllable PDT. In the process of PDT, the disulfide bond between ECyano and Fe3O4-M2pep was broken in response to reactive oxygen species (ROS), and then Fe3O4-M2pep was released to target M2-like TAMs, corresponding by the polarization of M2-like TAMs to M1-like TAMs for the killing of tumor cells. Compared with other groups, ECyano@Fe3O4-M2pep + theophylline + laser (ECyano@Fe3O4-M2pep + T + L) group displayed the lowest tumor volume (159.3 mm3) and the highest M1/M2 ratio (1.25- fold). We believe that this hybrid system will offer a promising way for the biomedical application of bacterial therapy.

Nanoscale Metal-Organic Layer Reprograms Cellular Metabolism to Enhance Photodynamic Therapy and Antitumor Immunity

Abnormal cancer metabolism causes hypoxic and immunosuppressive tumor microenvironment (TME), which limits the antitumor efficacy of photodynamic therapy (PDT). Herein, we report a photosensitizing nanoscale metal-organic layer (MOL) with anchored 3-bromopyruvate (BrP), BrP@MOL, as a metabolic reprogramming agent to enhance PDT and antitumor immunity. BrP@MOL inhibited mitochondrial respiration and glycolysis to oxygenate tumors and reduce lactate production. This metabolic reprogramming enhanced reactive oxygen species generation during PDT and reshaped the immunosuppressive TME to enhance antitumor immunity. BrP@MOL-mediated PDT inhibited tumor growth by >90 % with 40 % of mice being tumor-free, rejected tumor re-challenge, and prevented lung metastasis. Further combination with immune checkpoint blockade potently regressed the tumors with >98 % tumor inhibition and 80 % of mice being tumor-free.

Two-dimensional metal organic frameworks in cancer treatment

With large specific surface area, controllable pore size, increased active sites, and structural stability, two-dimensional metal organic frameworks (2D MOFs) have emerged as promising nanomedicines in cancer therapy. These distinctive features make 2D MOFs particularly advantageous in cancer treatment and the corresponding application has gained considerable popularity, signifying significant application potential. Herein, recent advances in various applications including drug delivery and chemotherapy, photodynamic therapy, sonodynamic therapy, chemodynamic therapy, catalytic therapy, and combined therapy were summarized, with emphasis on the latest progress of new materials and mechanisms for these processes. Moreover, the current challenges, potential solutions, and possible future directions are discussed as well.

Rationally Designed Benzobisthiadiazole-Based Covalent Organic Framework for High-Performance NIR-II Fluorescence Imaging-Guided Photodynamic Therapy

Although being applied as photosensitizers for photodynamic therapy, covalent organic frameworks (COFs) fail the precise fluorescence imaging in vivo and phototherapy in deep-tissue, due to short excitation/emission wavelengths. Herein, this work proposes the first example of NIR-II emissive and benzobisthiadiazole-based COF-980. Comparing to its ligands, the structure of COF-980 can more efficiently reducing the energy gap (ΔES1-T1) between the excited state and the triplet state to enhance photodynamic therapy efficiency. Importantly, COF-980 demonstrates high photostability, good anti-diffusion property, superior reactive oxygen species (ROS) generation efficiency, promising imaging ability, and ROS production in deep tissue (≈8 mm). Surprisingly, COF-980 combined with laser irradiation could trigger larger amount of intracellular ROS to high efficiently induce cancer cell death. Notably, COF-980 NPs precisely enable PDT guided by NIR-II fluorescence imaging that effectively inhibit the 4T1 tumor growth with negligible adverse effects. This study provides a universal approach to developing long-wavelength emissive COFs and exploits its applications for biomedicine.

Metal-Organic Framework Nanomaterials as a Medicine for Catalytic Tumor Therapy: Recent Advances

Nanomaterials, with unique physical, chemical, and biocompatible properties, have attracted significant attention as an emerging active platform in cancer diagnosis and treatment. Amongst them, metal-organic framework (MOF) nanostructures are particularly promising as a nanomedicine due to their exceptional surface functionalities, adsorption properties, and organo-inorganic hybrid characteristics. Furthermore, when bioactive substances are integrated into the structure of MOFs, these materials can be used as anti-tumor agents with superior performance compared to traditional nanomaterials. In this review, we highlight the most recent advances in MOFs-based materials for tumor therapy, including their application in cancer treatment and the underlying mechanisms.

Phosphate Coordination to Metal-Organic Layer Secondary Building Units Prolongs Drug Retention for Synergistic Chemoradiotherapy

Chemoradiotherapy combines radiotherapy with concurrent chemotherapy to potentiate antitumor activity but exacerbates toxicities and causes debilitating side effects in cancer patients. Herein, we report the use of a nanoscale metal-organic layer (MOL) as a 2D nanoradiosensitizer and a reservoir for the slow release of chemotherapeutics to amplify the antitumor effects of radiotherapy. Coordination of phosphate-containing drugs to MOL secondary building units prolongs their intratumoral retention, allowing for continuous release of gemcitabine monophosphate (GMP) for effective localized chemotherapy. In the meantime, the MOL sensitizes cancer cells to X-ray irradiation and provides potent radiotherapeutic effects. GMP-loaded MOL (GMP/MOL) enhances cytotoxicity by 2-fold and improves radiotherapeutic effects over free GMP in vitro. In a colon cancer model, GMP/MOL retains GMP in tumors for more than four days and, when combined with low-dose radiotherapy, inhibits tumor growth by 98 %. The synergistic chemoradiotherapy enabled by GMP/MOL shows a cure rate of 50 %, improves survival, and ameliorates cancer-proliferation histological biomarkers.

Metal-Organic Layers with Photosensitizer and Pyridine Pairs Activate Alkyl Halides for Photocatalytic Heck-Type Coupling with Olefins

Photochemical generation of alkyl radicals from haloalkanes often requires strong energy input from ultraviolet light or a strong photoreductant. Haloalkanes can alternatively be activated with nitrogen-based nucleophiles through a sequential SN2 reaction and single-electron reduction to access alkyl radicals, but these two reaction steps have opposite steric requirements on the nucleophiles. Herein, we report the design of Hf12 metal-organic layers (MOLs) with iridium-based photosensitizer bridging ligands and secondary-building-unit-supported pyridines for photocatalytic alkyl radical generation from haloalkanes. By bringing the photosensitizer and pyridine pairs in proximity, the MOL catalysts allowed facile access to the pyridinium salts from SN2 reactions between haloalkanes and pyridines and at the same time enhanced electron transfer from excited photosensitizers to pyridinium salts to facilitate alkyl radical generation. Consequentially, the MOLs efficiently catalyzed Heck-type cross-coupling reactions between haloalkanes and olefinic substrates to generate functionalized alkenes. The MOLs showed 4.6 times higher catalytic efficiency than the homogeneous counterparts and were recycled and reused without a loss of catalytic activity.

Exploring Linker-Group-Guided Self-Assembly of Ultrathin 2D Supramolecular Nanosheets in Water for Synergistic Cancer Phototherapy

Water is ubiquitous in natural systems where it builds an essential environment supporting biological supramolecular polymers to function, transport, and exchange. However, this extreme polar environment becomes a hindrance for the superhydrophobic functional π-conjugated molecules, causing significant negative impacts on regulating their aggregation pathways, structures, and properties of the subsequently assembled nanomaterials. It especially makes the self-assembly of ultrathin two-dimensional (2D) functional nanomaterials by π-conjugated molecules a grand challenge in water, although ultrathin 2D functional nanomaterials have exhibited unique and superior properties. Herein, we demonstrate the organic solvent-free self-assembly of one-molecule-thick 2D nanosheets based on exploring how side chain modifications rule the aggregation behaviors of π-conjugated macrocycles in water. Through an in-depth understanding of the roles of linking groups for side chains on affecting the aggregation behaviors of porphyrins in water, the regulation of molecular arrangement in the aggregated state (H- or J-type aggregation) was attained. Moreover, by arranging ionic porphyrins into 2D single layers through J-aggregation, the ultrathin nanosheets (thickness ≈ 2 nm) with excellent solubility and stability were self-assembled in pure water, which demonstrated both outstanding 1O2 generation and photothermal capability. The ultrathin nanosheets were further investigated as metal- and carrier-free nanodrugs for synergetic phototherapies of cancers both in vitro and in vivo, which are highly desirable by combining the advantages and avoiding the disadvantages of the single use of PDT or PTT.

A metal-organic framework complex for enhancing tumor treatments through synergistic effect of chemotherapy and photodynamic therapy

Porphyrin-based metal-organic frameworks (PMOFs) are a kind of crystal hybrid material with broad application prospects in energy, catalysis, biomedicine, and other fields. In this study, the La-TCPP PMOF nanocrystal was constructed using a porphyrin ligand and La ion. This material can produce a high loading rate on doxorubicin (DOX) owing to its special porous structure. The high loading rate of drug molecules and the reactive oxygen species (ROS) of the porphyrin ligand enable La-TCPP@DOX nanocrystal to produce a powerful killing effect on cancer cells under the synergistic attack of chemotherapy (CT) and photodynamic therapy (PDT). Finally, by modifying the targeted aptamer, the actual therapeutic effect of this special La-TCPP@DOX@Apt material on tumors was confirmed by applying the established mouse tumor model. The composite nanomaterial not only avoids the side effects caused by high concentrations of chemotherapeutic drugs, but also overcomes the limitation of PDT owing to insufficient light penetration and can inhibit and kill solid tumors under the condition of synergistic attack. This study is a complement to PMOF crystal materials, and its tumor-killing ability was achieved by loading drugs and introducing targeting molecules, which proves that the synergistic attack can more effectively inhibit and treat solid tumors. These studies have a reference and guiding significance for the treatment of cancer patients.

Carbon network-hosted porphyrin as a highly biocompatible nanophotosensitizer for enhanced photodynamic therapy

Photodynamic therapy (PDT) has the characteristics of being simple and non-invasive, and with on-demand light control. However, most photosensitizers exhibit strong hydrophobicity, low quantum yields in water and low tumor selectivity. In this study, carbon network-hosted porphyrins (CPs) with high biocompatibility and efficient singlet oxygen (1O2) generation were developed to reduce the biotoxicity of photosensitizers and avoid quenching caused by hydrophobic aggregation for enhanced PDT. The CPs were prepared by a simple solid-phase synthesis method using porphyrin, green non-toxic citric acid and urea as the raw materials. The CPs exhibited excellent water solubility and high biocompatibility. Even when the concentration reached 1.5 mg mL-1, cells still had good biological activity. By separately fixing the porphyrins in the carbon network, the CPs avoided aggregation-induced inactivation and had high generation efficiency of 1O2. Furthermore, in order to improve the PDT effect, the CPs were modified with the upper nuclear targeting peptide TAT (T-CPs), which was used to target the nucleus and generate 1O2in situ to directly destroy genetic material. The proposed strategy provides a simple and green path to prepare nanophotosensitizers with high biocompatibility and efficient 1O2 generation for PDT.

Escherichia coli-Based In Situ Triggerable Probe as an Amplifier for Sensitive Diagnosis and Penetrated Therapy of Cancer

Escherichia coli (E. coli) was used for cancer therapy due to the tumor-targeting, catalytic, and surface-reducing properties. Effective diagnosis combined with treatment of cancer based on E. coli, however, was rarely demonstrated. In this study, E. coli was used to surface reduce HAuCl4 and as a carrier to modify riboflavin (Rf) and luminol (E-Au@Rf@Lum). After targeted delivery to tumor, the E-Au@Rf@Lum probe could actively emit 425 nm blue-violet chemiluminescence (CL) to achieve cell imaging for cancer diagnosis. Furthermore, this light could in situ trigger the photosensitizer (Rf) through CL resonance energy transfer, which produces reactive oxygen species (ROS) for accurate photodynamic therapy. In return, the excessive ROS enhanced the blue-violet light which was further absorbed by Rf, and ROS production was cyclically amplified. Abundant ROS broke down the dense extracellular matrix network and penetrated deep into tumors. Besides, E. coli with excellent catalytic property could decompose H2O2 to O2 to relieve tumor hypoxia for a long time and enhance the photosensitized process of Rf. By self-illumination, effective penetration, and tumor hypoxia relief, this work opens a self-amplified therapy modality to tumor.

Manganese-Based Immunostimulatory Metal-Organic Framework Activates the cGAS-STING Pathway for Cancer Metalloimmunotherapy

Metal-organic frameworks (MOFs) show tremendous promise for drug delivery due to their structural and functional versatility. However, MOFs are usually used as biologically inert carriers in most cases. The creation of intrinsically immunostimulatory MOFs remains challenging. In this study, a facile and green synthesis method is proposed for the preparation of a manganese ion (Mn2+)-based immunostimulatory MOF (ISAMn-MOF) for cancer metalloimmunotherapy. ISAMn-MOF significantly facilitates the activation of cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) related genes and signaling pathways in bone-marrow-derived dendritic cells (BMDCs). BMDCs treated with ISAMn-MOF secrete 4-fold higher type I interferon and 2- to 16-fold higher proinflammatory cytokines than those treated with equivalent MnCl2. ISAMn-MOF alone or its combination with immune checkpoint antibodies significantly suppresses tumor growth and metastasis and prolongs mouse survival. Mechanistic studies indicate that ISAMn-MOF treatment facilitates the infiltration of stimulatory immune cells in tumors and lymphoid organs. This study provides insight into the design of bioactive MOFs for improved cancer metalloimmunotherapy.

Metal-Organic Layer Delivers 5-Aminolevulinic Acid and Porphyrin for Dual-Organelle-Targeted Photodynamic Therapy

The efficacy of photodynamic therapy (PDT) depends on the subcellular localization of photosensitizers. Herein, we report a dual-organelle-targeted nanoparticle platform for enhanced PDT of cancer. By grafting 5-aminolevulinic acid (ALA) to a Hf12 -based nanoscale metal-organic layer (Hf-MOL) via carboxylate coordination, ALA/Hf-MOL enhanced ALA delivery and protoporphyrin IX (PpIX) synthesis in mitochondria, and trapped the Hf-MOL comprising 5,15-di-p-benzoatoporphyrin (DBP) photosensitizers in lysosomes. Light irradiation at 630 nm simultaneously excited PpIX and DBP to generate singlet oxygen and rapidly damage both mitochondria and lysosomes, leading to synergistic enhancement of the PDT efficacy. The dual-organelle-targeted ALA/Hf-MOL outperformed Hf-MOL in preclinical PDT studies, with a 2.7-fold lower half maximal inhibitory concentration in cytotoxicity assays in vitro and a 3-fold higher cure rate in a colon cancer model in vivo.

Rational Design of Mesoporous Coordination Polymer Nanophotosensitizers for Photodynamic Tumor Ablation

Effective clinical practice of precise photodynamic therapy (PDT) is severely impeded by the inherent drawbacks and aggregation propensity of conventional photosensitizers. An all-in-one approach is highly desired to optimize structural features, photophysical properties, and pharmacokinetic behaviors of photosensitizers. Herein, we have fabricated mesoporous boron dipyrromethene-bridged coordination polymer nanophotosensitizers (BCP-NPs) for high-performance PDT via a unique solvent-assisted assembly strategy. Distinctive photophysical and structural characteristics of BCP-NPs confer enhanced photodynamic activities, together with high cellular uptake and ultrahigh stability. Moreover, BCP-NPs showed excellent tumor accumulation and prolonged tumor retention, achieving eradication of the triple-negative breast cancer (TNBC) model under low-power-density LED irradiation. This work has provided a valuable paradigm for the construction of mesoporous photoactive nanomaterials for biophotonic applications.

2D Nano-Sonosensitizers Facilitate Energy Transfer to Enhance Sonodynamic Therapy

Although sonodynamic therapy (SDT) has shown promise for cancer treatment, the lack of efficient sonosensitizers (SSs) has limited the clinical application of SDT. Here, a new strategy is reported for designing efficient nano-sonosensitizers based on 2D nanoscale metal-organic layers (MOLs). Composed of Hf-oxo secondary building units (SBUs) and iridium-based linkers, the MOL is anchored with 5,10,15,20-tetra(p-benzoato)porphyrin (TBP) sensitizers on the SBUs to afford TBP@MOL. TBP@MOL shows 14.1- and 7.4-fold higher singlet oxygen (1 O2 ) generation than free TBP ligands and Hf-TBP, a 3D nanoscale metal-organic framework, respectively. The 1 O2 generation of TBP@MOL is enhanced by isolating TBP SSs on the SBUs of the MOL, which prevents aggregation-induced quenching of the excited sensitizers, and by triplet-triplet Dexter energy transfer between excited iridium-based linkers and TBP SSs, which more efficiently harnesses broad-spectrum sonoluminescence. Anchoring TBP on the MOL surface also enhances the energy transfer between the excited sensitizer and ground-state triplet oxygen to increase 1 O2 generation efficacy. In mouse models of colorectal and breast cancer, TBP@MOL demonstrates significantly higher SDT efficacy than Hf-TBP and TBP. This work uncovers a new strategy to design effective nano-sonosensitizers by facilitating energy transfer to efficiently capture broad-spectrum sonoluminescence and enhance 1 O2 generation.

Recent Development of Rhenium-Based Materials in the Application of Diagnosis and Tumor Therapy

Rhenium (Re) is widely used in the diagnosis and treatment of cancer due to its unique physical and chemical properties. Re has more valence electrons in its outer shell, allowing it to exist in a variety of oxidation states and to form different geometric configurations with many different ligands. The luminescence properties, lipophilicity, and cytotoxicity of complexes can be adjusted by changing the ligand of Re. This article mainly reviews the development of radionuclide 188Re in radiotherapy and some innovative applications of Re as well as the different therapeutic approaches and imaging techniques used in cancer therapy. In addition, the current application and future challenges and opportunities of Re are also discussed.

Nanoscale Two-Dimensional FeII- and CoII-Based Metal-Organic Frameworks of Porphyrin Ligand for the Photodynamic Therapy of Breast Cancer

The delivery of biocompatible reagents into cancer cells can elicit an anticancer effect by taking advantage of the unique characteristics of the tumor microenvironment (TME). In this work, we report that nanoscale two-dimensional FeII- and CoII-based metal-organic frameworks (NMOFs) of porphyrin ligand meso-tetrakis (6-(hydroxymethyl) pyridin-3-yl) porphyrin (THPP) can catalyze the generation of hydroxyl radicals (•OH) and O2 in the presence of H2O2 that is overexpressed in the TME. Photodynamic therapy consumes the generated O2 to produce a singlet oxygen (1O2). Both •OH and 1O2 are reactive oxygen species (ROS) that inhibit cancer cell proliferation. The FeII- and CoII-based NMOFs were non-toxic in the dark but cytotoxic when irradiated with 660 nm light. This preliminary work points to the potential of porphyrin-based ligands of transition metals as anticancer drugs by synergizing different therapeutic modalities.

Molecular Engineering of Metal-Organic Layers for Sustainable Tandem and Synergistic Photocatalysis

Metal-organic layers (MOLs), a monolayered version of metal-organic frameworks (MOFs), have recently emerged as a novel two-dimensional molecular material platform to design multifunctional catalysts. MOLs inherit the intrinsic molecular tunability of MOFs and yet have more accessible and modifiable building blocks. Here we report molecular engineering of six MOLs via modulated solvothermal synthesis between HfCl4 and three photosensitizing ligands followed by postsynthetic modification with two carboxylate-containing cobaloximes for tandem and synergistic photocatalysis. Morphological and structural characterization by transmission electron microscopy and atomic force microscopy and compositional analysis by inductively coupled plasma-mass spectrometry and nuclear magnetic resonance spectroscopy establish the MOLs as flat nanoplates with a periodic lattice structure of hexagonal symmetry. The MOLs efficiently catalyze tandem dehydrogenative coupling reactions and synergistic Heck-type coupling reactions. The most active MOL catalyst was used for the gram-scale synthesis of vesnarinone, a cardiotonic agent, in 80% yield with a turnover number of 400 and in eight consecutive reaction cycles without significant loss of activities.

Microorganism-enabled photosynthetic oxygeneration and ferroptosis induction reshape tumor microenvironment for augmented nanodynamic therapy

Nanodynamic therapy (NDT) based on reactive oxygen species (ROS) generation has been envisioned as a distinct modality for efficient cancer treatment. However, insufficient ROS generation and partial ROS consumption frequently limit the theraputic effect and outcome of NDT owing to the low oxygen (O2) tension and high glutathione (GSH) level in tumor microenvironment (TME). To circumvent these critical issues, we herein proposed and engineered the biodegradable GSH-depletion Mn(III)-riched manganese oxide nanospikes (MnOx NSs) with the photosynthetic bacterial cyanobacteria (Cyan) as a high-efficient and synergistic platform to reshape TME by simultaneously increasing oxygen content and decreasing GSH level. Specifically, under the trigger of acidity, MnOx NSs reacted with photosynthetic oxygen can generate toxic singlet oxygen (1O2). Moreover, MnOx NSs significantly reduced intracellular GSH, resulting in decreased GPX4 activity, which induced tumor cell non-apoptotic ferroptosis. Consequently, this combined strategy based on coadministration with Cyan and MnOx NSs demonstrated the superior antitumor efficacy via amplification of oxidative stress in 4T1 tumor-bearing mice for the synergetic oxygen-augmented nanodynamic/ferroptosis therapy. This work highlights a facile synergistic micro-/nano-system with the specific capability of reshaping TME to augment the sensitivity and therapeutic efficacy of NDT in solid hypoxic tumor therapy.

Tuning the aqueous self-assembly of porphyrins by varying the number of cationic side chains

Due to their excellent electronic and optical properties, porphyrins are extensively studied conjugated macrocycles in supramolecular chemistry for assembling functional nanomaterials. Although the aggregation of monomers plays a significant role in driving the self-assembly process into ordered nanostructures, it remains a challenge for tuning the self-assembling behavior of porphyrins through molecular structure modifications, especially in aqueous solutions. In the present work, two novel water-soluble porphyrin derivatives were synthesized by introducing cationic linear side chains into the π-conjugated core for phosphate-templated assembly through electrostatic interactions. It was found that the stacking patterns (H- or J-type aggregation) of porphyrins could be tuned by varying the number of side chains, which are associated with dramatic morphological change. The cytotoxicity and photodynamic properties of the J-aggregation-driven nano-assemblies were also investigated for the purpose of anti-cancer treatment. This study demonstrates a facile and effective strategy to regulate the aqueous self-assembling behavior of porphyrins that can impact the structure and properties of assembly, which will be of great benefit to the design and synthesis of functional nanomaterials for specific applications.