Nanoscale metal-organic frameworks for mitochondria-targeted radiotherapy-radiodynamic therapy

Nanoscale Metal-Organic Layer Isolates Phthalocyanines for Efficient Mitochondria-Targeted Photodynamic Therapy

Zinc-phthalocyanine (ZnPc) photosensitizers (PSs) have shown great potential in photodynamic therapy (PDT) owing to their strong absorption at long wavelengths (650-750 nm), high triplet quantum yields, and biocompatibility. However, the clinical utility of ZnPc PSs is limited by their poor solubility and tendency to aggregate in aqueous environments. Here we report the design of a new nanoscale metal-organic layer (nMOL) assembly, ZnOPPc@nMOL, with ZnOPPc [ZnOPPc = zinc(II)-2,3,9,10,16,17,23,24-octa(4-carboxyphenyl)phthalocyanine] PSs supported on the secondary building units (SBUs) of a Hf₁₂ nMOL for PDT. Upon irradiation, SBU-bound ZnOPPc PSs absorb 700 nm light and efficiently sensitize the formation of singlet oxygen by preventing aggregation-induced self-quenching of ZnOPPc excited states. With intrinsic mitochondria-targeting capability, ZnOPPc@nMOL showed exceptional PDT efficacy with >99% tumor growth inhibition and 40-60% cure rates on two mouse models of colon cancer.

Versatile Nanoscale Metal-Organic Frameworks (nMOFs): An Emerging 3D Nanoplatform for Drug Delivery and Therapeutic Applications

For decades, nanoscale metal-organic frameworks (nMOFs) have attracted extensive interest in biomedicine due to their distinct characteristics, including facile synthesis, porous interior, and tunable biocompatibility. With high porosity, versatile nMOFs allow for the facile encapsulation of various therapeutic agents with exceptionally high payloads. Constructed from metal ions and organic linkers through coordination bonds, nMOFs with plentiful functional groups enable the surface modification for active targeting and enhanced biocompatibility. This review outlines the up-to-date progresses on the exploration of nMOFs in the field of biomedicine. First, the classification and synthesis of nMOFs are discussed, followed by the concrete introduction of drug loading strategies of nMOFs and mechanisms of stimulation-responsive drug release. Second, the smart designs of the nMOFs-based platforms for anticancer and antibacterial treatment are summarized. Finally, the basic challenges faced by nMOFs research and the great potential of biomimetic nMOFs are presented. This review article affords an inspiring insight into the interdisciplinary research of nMOFs and their biomedical applications, which holds great expectation for their further clinical translation.

Reactive Oxygen Species-Regulating Strategies Based on Nanomaterials for Disease Treatment

Reactive oxygen species (ROS) play an essential role in physiological and pathological processes. Studies on the regulation of ROS for disease treatments have caused wide concern, mainly involving the topics in ROS-regulating therapy such as antioxidant therapy triggered by ROS scavengers and ROS-induced toxic therapy mediated by ROS-elevation agents. Benefiting from the remarkable advances of nanotechnology, a large number of nanomaterials with the ROS-regulating ability are developed to seek new and effective ROS-related nanotherapeutic modalities or nanomedicines. Although considerable achievements have been made in ROS-based nanomedicines for disease treatments, some fundamental but key questions such as the rational design principle for ROS-related nanomaterials are held in low regard. Here, the design principle can serve as the initial framework for scientists and technicians to design and optimize the ROS-regulating nanomedicines, thereby minimizing the gap of nanomedicines for biomedical application during the design stage. Herein, an overview of the current progress of ROS-associated nanomedicines in disease treatments is summarized. And then, by particularly addressing these known strategies in ROS-associated therapy, several fundamental and key principles for the design of ROS-associated nanomedicines are presented. Finally, future perspectives are also discussed in depth for the development of ROS-associated nanomedicines.

The application of nanoparticles in cancer immunotherapy: Targeting tumor microenvironment

The tumor development and metastasis are closely related to the structure and function of the tumor microenvironment (TME). Recently, TME modulation strategies have attracted much attention in cancer immunotherapy. Despite the preliminary success of immunotherapeutic agents, their therapeutic effects have been restricted by the limited retention time of drugs in TME. Compared with traditional delivery systems, nanoparticles with unique physical properties and elaborate design can efficiently penetrate TME and specifically deliver to the major components in TME. In this review, we briefly introduce the substitutes of TME including dendritic cells, macrophages, fibroblasts, tumor vasculature, tumor-draining lymph nodes and hypoxic state, then review various nanoparticles targeting these components and their applications in tumor therapy. In addition, nanoparticles could be combined with other therapies, including chemotherapy, radiotherapy, and photodynamic therapy, however, the nanoplatform delivery system may not be effective in all types of tumors due to the heterogeneity of different tumors and individuals. The changes of TME at various stages during tumor development are required to be further elucidated so that more individualized nanoplatforms could be designed.

Multifunctional metal-organic framework heterostructures for enhanced cancer therapy

Metal-organic frameworks (MOFs) are an emerging class of molecular crystalline materials built from metal ions or clusters bridged by organic linkers. By taking advantage of their synthetic tunability and structural regularity, MOFs can hierarchically integrate nanoparticles and/or biomolecules into a single framework to enable multifunctions. The MOF-protected heterostructures not only enhance the catalytic capacity of nanoparticle components but also retain the biological activity of biomolecules in an intracellular microenvironment. Therefore, the multifunctional MOF heterostructures have great advantages over single components in cancer therapy. In this review, we comprehensively summarize the general principle of the design and functional modulation of nanoscaled MOF heterostructures, and biomedical applications in enhanced therapy within the last five years. The functions of MOF heterostructures with a controlled size can be regulated by designing various functional ligands and in situ growth/postmodification of nanoparticles and/or biomolecules. The advances in the application of multifunctional MOF heterostructures are also explored for enhanced cancer therapies involving photodynamic therapy, photothermal therapy, chemotherapy, radiotherapy, immunotherapy, and theranostics. The remaining challenges and future opportunities in this field, in terms of precisely localized assembly, maximizing composite properties, and processing new techniques, are also presented. The introduction of multiple components into one crystalline MOF provides a promising approach to design all-in-one theranostics in clinical treatments.

Mechanisms for Tuning Engineered Nanomaterials to Enhance Radiation Therapy of Cancer

Engineered nanomaterials that produce reactive oxygen species on exposure to X- and gamma-rays used in radiation therapy offer promise of novel cancer treatment strategies. Similar to photodynamic therapy but suitable for large and deep tumors, this new approach where nanomaterials acting as sensitizing agents are combined with clinical radiation can be effective at well-tolerated low radiation doses. Suitably engineered nanomaterials can enhance cancer radiotherapy by increasing the tumor selectivity and decreasing side effects. Additionally, the nanomaterial platform offers therapeutically valuable functionalities, including molecular targeting, drug/gene delivery, and adaptive responses to trigger drug release. The potential of such nanomaterials to be combined with radiotherapy is widely recognized. In order for further breakthroughs to be made, and to facilitate clinical translation, the applicable principles and fundamentals should be articulated. This review focuses on mechanisms underpinning rational nanomaterial design to enhance radiation therapy, the understanding of which will enable novel ways to optimize its therapeutic efficacy. A roadmap for designing nanomaterials with optimized anticancer performance is also shown and the potential clinical significance and future translation are discussed.

Fucoidan-coated nanoparticles target radiation-induced P-selectin to enhance chemoradiotherapy in murine colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer-related death for both men and women, highlighting the need for new treatment strategies. Advanced disease is often treated with a combination of radiation and cytotoxic agents, such as DNA damage repair inhibitors and DNA damaging agents. To optimize the therapeutic window of these multimodal therapies, advanced nanomaterials have been investigated to deliver sensitizing agents or enhance local radiation dose deposition. In this study, we demonstrate the feasibility of employing an inflammation targeting nanoscale metal-organic framework (nMOF) platform to enhance CRC treatment. This novel formulation incorporates a fucoidan surface coating to preferentially target P-selectin, which is over-expressed or translocated in irradiated tumors. Using this radiation stimulated delivery strategy, a combination PARP inhibitor (talazoparib) and chemotherapeutic (temozolomide) drug-loaded hafnium and 1,4-dicarboxybenzene (Hf-BDC) nMOF was evaluated both in vitro and in vivo. Significantly, these drug-loaded P-selectin targeted nMOFs (TT@Hf-BDC-Fuco) show improved tumoral accumulation over multiple controls and subsequently enhanced therapeutic effects. The integrated radiation and nanoformulation treatment demonstrated improved tumor control (reduced volume, density, and growth rate) and increased survival in a syngeneic CRC mouse model. Overall, the data from this study support the continued investigation of radiation-priming for targeted drug delivery and further consideration of nanomedicine strategies in the clinical management of advanced CRC.

Multifunctional Hf/Mn-TCPP Metal-Organic Framework Nanoparticles for Triple-Modality Imaging-Guided PTT/RT Synergistic Cancer Therapy

Background

Recent studies have validated and confirmed the great potential of nanoscale metal-organic framework (NMOF) in the biomedical field, especially in improving the efficiency of cancer diagnosis and therapy. However, most previous studies only utilized either the metal cluster or the organic ligand of the NMOF for cancer treatments and merely reported limited theranostic functions, which may not be optimized. As a highly designable and easily functionalized material, prospective rational design offers a powerful way to extract the maximum benefit from NMOF for cancer theranostic applications.

Materials and Methods

A NMOF based on hafnium (Hf) cluster and Mn(III)-porphyrin ligand was rational designed and synthesized as a high-performance multifunctional theranostic agent. The folic acid (FA) was modified on the NMOF surface to enhance the cancer targeting efficacy. The proposed “all-in-one” FA-Hf-Mn-NMOF (fHMNM) was characterized and identified using various analytical techniques. Then, in vitro and in vivo studies were performed to further explore the effects of fHMNM both as the magnetic resonance imaging (MRI)/computed tomography (CT)/photoacoustic imaging (PAI) contrast agent and as the photothermal therapy (PTT)/radiotherapy (RT) agent.

Results

A tumour targeting multifunctional fHMNM was successfully synthesized with high performance for MRI/CT/PAI enhancements and image-guided PTT/RT synergistic therapy properties. Compared with the current clinical CT and MR contrast agents, the X-ray attenuation and T₁ relaxation rate of this integrated nanosystem increased 1.7-fold and 3–5-fold, respectively. More importantly, the catalase-like Mn(III)-porphyrin ligand can decompose H₂O₂ into O₂ in tumour microenvironments to improve the synergistic treatment efficiency of PTT and RT. Significant tumour growth inhibition was achieved in mouse cancer models without obvious damage to the other organs.

Conclusion

This work highlights the potential of fHMNM as an easily designable material for biomedical applications, could be an effective tool for in vivo detection and subsequent treatment of tumour.

Nanoscale metal-organic frameworks for x-ray activated in situ cancer vaccination

Cancer vaccines have been actively pursued to bolster antitumor immunity. Here, we designed nanoscale metal-organic frameworks (nMOFs) as locally activable immunotherapeutics to release danger-associated molecular patterns (DAMPs) and tumor antigens and deliver pathogen-associated molecular patterns (PAMPs) for in situ personalized cancer vaccination. When activated by x-rays, nMOFs effectively generate reactive oxygen species to release DAMPs and tumor antigens while delivering CpG oligodeoxynucleotides as PAMPs to facilitate the maturation of antigen-presenting cells. Together, DAMPs, tumor antigens, and PAMPs expand cytotoxic T cells in tumor-draining lymph nodes to reinvigorate the adaptive immune system for local tumor regression. When treated in combination with an immune checkpoint inhibitor, the local therapeutic effects of nMOF-based vaccines were extended to distant tumors via attenuating T cell exhaustion. Our work demonstrates the potential of nMOFs as x-ray-activable in situ cancer vaccines to awaken the host's innate and adaptive immune systems for systemic antitumor immunity.

Smart Design of Nanomaterials for Mitochondria-Targeted Nanotherapeutics

Mitochondria are the powerhouse of cells. They are vital organelles that maintain cellular function and metabolism. Dysfunction of mitochondria results in various diseases with a great diversity of clinical appearances. In the past, strategies have been developed for fabricating subcellular-targeting drug-delivery nanocarriers, enabling cellular internalization and subsequent organelle localization. Of late, innovative strategies have emerged for the smart design of multifunctional nanocarriers. Hierarchical targeting enables nanocarriers to evade and overcome various barriers encountered upon in vivo administration to reach the organelle with good bioavailability. Stimuli-responsive nanocarriers allow controlled release of therapeutics to occur at the desired target site. Synergistic therapy can be achieved using a combination of approaches such as chemotherapy, gene and phototherapy. In this Review, we survey the field for recent developments and strategies used in the smart design of nanocarriers for mitochondria-targeted therapeutics. Existing challenges and unexplored therapeutic opportunities are also highlighted and discussed to inspire the next generation of mitochondrial-targeting nanotherapeutics.

Surface-Charge-Switchable Nanoclusters for Magnetic Resonance Imaging-Guided and Glutathione Depletion-Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) is an effective noninvasive therapeutic method that employs photosensitizers (PSs) converting oxygen to highly cytotoxic singlet oxygen (¹O₂) under light irradiation. The conventional PDT efficacy is, however, compromised by the nonspecific delivery of PSs to tumor tissue, the hypoxic tumor microenvironment, and the reduction of generated ¹O₂ by the intracellular antioxidant glutathione (GSH). Herein, an intelligent multifunctional synergistic nanoplatform (CMGCC) for T₁-weighted magnetic resonance (MR) imaging-guided enhanced PDT is presented, which consists of nanoparticles composed of catalase (CAT) and manganese dioxide (MnO₂) that are integrated within chlorin-e6-modified glycol chitosan (GC) polymeric micelles. In this system, (1) GC polymers with pH-sensitive surface charge switchability from neutral to positive could improve the PS accumulation within the tumor region, (2) CAT could effectively reoxygenate the hypoxic tumor via catalyzing endogenous hydrogen peroxide to O₂, and (3) MnO₂ could consume the intracellular GSH while simultaneously producing Mn²⁺ as a contrast agent for T₁-weighted MR imaging. The CMGCC particles possess uniform size distribution, well-defined structure, favorable enzyme activity, and superior ¹O₂ generation ability. Both in vitro and in vivo experiments demonstrate that the CMGCC exhibit significantly enhanced PDT efficacy toward HeLa cells and subcutaneous HeLa tumors. Our study thereby demonstrates this to be a promising synergistic theranostic nanoplatform with highly efficient PDT performance for cancer therapy.

X-ray and NIR light dual-triggered mesoporous upconversion nanophosphor/Bi heterojunction radiosensitizer for highly efficient tumor ablation

Developing a multi-functional radiosensitizer with high efficiency and low toxicity remains challenging. Herein, we report a mesoporous heterostructure radiosensitizer (UCNP@NBOF-FePc-PFA) containing Lu-based upconversion nanophosphor (UCNP) and Bi-based nanomaterial loaded with iron phthalocyanine for X-ray and NIR light dual-triggered tri-modal tumor therapy. NaLuF₄:Yb,Tm, a Lu-based UCNP, offers radiosensitization and upconversion luminescence for optical bio-imaging. However, Bi has a higher X-ray mass attenuation coefficient than Lu. Thus, after stepwise fabrication, Na_0.2Bi_0.8O_0.35F_1.91:Yb (NBOF) was assembled with the UCNP to form a mesoporous heterostructure composite. This enhanced the radiosensitization effect and drug load to realize multi-modal tumor therapy. After coating it with folate-conjugated amphiphilic PEG (PFA), UCNP@NBOF-FePc-PFA realized tumor photothermal/photodynamic/radio-therapy. The structure of UCNP@NBOF-FePc-PFA was well characterized. Different properties triggered by X-ray and NIR light were evaluated. Finally, a highly efficient tumor ablation effect was demonstrated in vitro and in vivo. Consequently, this kind of nanocomposite provides a unique strategy for designing a theranostic platform for oncotherapy. STATEMENT OF SIGNIFICANCE: The synergy of enhanced radiotherapy and photothermal/photodynamic therapy is found to improve tumor therapeutic efficacy. On that basis, a heterostructure nanohybrid containing Lu-based UCNP and Bi-based mesoporous material is synthesized. The heterostructure nanohybrid can be loaded with FePc and decorated with folate-modified amphiphilic PEG to form a multi-functional theranostic nano-platform. The platform exhibits upconversion luminescence capacity, X-ray attenuation property, photothermal effect, and X-ray and NIR dual-light triggered ROS generation capability. These features can not only enable upconversion luminescence/CT bioimaging of living beings but also be applied to the photothermal/photodynamic/radio- synergistic tumor ablation. To sum up, the nanomaterial offers a novel method for the construction of a new theranostic platform.

Safety Considerations of Cancer Nanomedicine-A Key Step toward Translation

The rate of translational effort of nanomedicine requires strategic planning of nanosafety research in order to enable clinical trials and safe use of nanomedicine in patients. Herein, the experiences that have emerged based on the safety data of classic liposomal formulations in the space of oncology are discussed, along with a description of the new challenges that need to be addressed according to the rapid expansion of nanomedicine platform beyond liposomes. It is valuable to consider the combined use of predictive toxicological assessment supported by deliberate investigation on aspects such as absorption, distribution, metabolism, and excretion (ADME) and toxicokinetic profiles, the risk that may be introduced during nanomanufacture, unique nanomaterials properties, and nonobvious nanosafety endpoints, for example. These efforts will allow the generation of investigational new drug-enabling safety data that can be incorporated into a rational infrastructure for regulatory decision-making. Since the safety assessment relates to nanomaterials, the investigation should cover the important physicochemical properties of the material that may lead to hazards when the nanomedicine product is utilized in humans.

BiVO4@Bi2S3 Heterojunction Nanorods with Enhanced Charge Separation Efficiency for Multimodal Imaging and Synergy Therapy of Tumor

Despite malignant tumors being one of the most serious diseases threatening human health and living quality, exploring theranostic agents for highly effective tumor diagnosis and treatment is still full of challenges. Herein, we demonstrate the design and preparation of Tween-20-modified BiVO₄@Bi₂S₃ heterojunction nanorods (HNRs) for multimodal computed tomography (CT)/photoacoustic (PA) imaging and radiotherapy (RT)/radiodynamic therapy (RDT)/photothermal therapy (PTT) synergistic therapy. Benefiting from the high X-ray attenuation coefficient of Bi, BiVO₄@Bi₂S₃ HNRs exhibit a sensitive CT imaging capacity and radiation enhancement effect during RT. Meanwhile, the strong NIR absorption of Bi₂S₃ endows BiVO₄@Bi₂S₃ HNRs with an excellent PA imaging and photothermal transformation capacity. More importantly, by taking advantage of the type II band alignment between BiVO₄ and Bi₂S₃, an extra internal electric field is established to accelerate the separation of X-ray-induced electrons and holes in BiVO₄@Bi₂S₃ HNRs, resulting in the realization of highly effective X-ray-induced RDT. Because the in vitro and in vivo experiments have verified that the RT/RDT/PTT synergistic therapeutic efficacy is greatly superior to any single treatment, it is believed that our BiVO₄@Bi₂S₃ HNRs can be used as the multifunctional nanotheranostic platform for malignant tumor theranostics.

Pristine Cu-MOF Induces Mitotic Catastrophe and Alterations of Gene Expression and Cytoskeleton in Ovarian Cancer Cells

Metals-organic frameworks (MOFs) have been widely explored in biomedicine, mostly in drug delivery, biosensing, and bioimaging due to their large surface area, tunable porosity, readily chemical functionalization, and good biocompatibility. However, the underlining cellular mechanisms controlling the process for MOF cytotoxicity remains almost completely unknown. Here, we demonstrate that pristine Cu-MOF without any loaded drug selectively inhibited ovarian cancer mainly through promoting tubulin polymerization and destroying the cell actin cytoskeleton (F-actin) to trigger the mitotic catastrophe, accompanying by conventional programmed cell death. To our knowledge, this is the first report claiming that mitotic catastrophe may be an explaining mechanism of MOF cytotoxicity. Cu-MOF with an intrinsic protease-like activity also hydrolyzed cellular cytoskeleton proteins (F-actin). The RNA sequencing data indicated the differential expressional mRNA of cell proliferation and actin cytoskeleton (ACTA2, ACTN3, FSCN2, and SCIN) and mitotic spindles (PLK1 and TPX2) related genes. We found that Cu-MOF as a promising candidate in the disruption of cellular cytoskeleton and the change of the gene expression could be actin altering and antimitotic agents against cancer cells, allowing for fundamental biological and biophysical studies of MOFs.

Nanoscale Metal-Organic Frameworks Generate Reactive Oxygen Species for Cancer Therapy

In the past 15 years, enormous progress has been made in cancer nanotechnology, and a several nanoparticles have entered clinical testing for cancer treatment. Among these nanoparticles are nanoscale metal-organic frameworks (nMOFs), a class of organic-inorganic hybrid nanomaterials constructed from metal binding sites and bridging ligands, which have attracted significant attention for their ability to integrate porosity, crystallinity, compositional and structural tunability, multifunctionality, and biocompatibility into a singular nanomaterial for cancer therapies. This Outlook article summarizes the progress on the design of nMOFs as nanosensitizers for photodynamic therapy (PDT), radiotherapy (RT), radiotherapy-radiodynamic therapy (RT-RDT), and chemodynamic therapy (CDT) via nMOF-mediated reactive oxygen species (ROS) generated under external energy stimuli or in the presence of endogenous chemical triggers. Inflammatory responses induced by nMOF-mediated ROS generation activate tumor microenvironments to potentiate cancer immunotherapy, extending the local treatment effects of nMOF-based ROS therapy to distant tumors via abscopal effects. Future research directions in nMOF-mediated ROS therapies and the prospect of clinical applications of nMOFs as cancer therapeutics are also discussed.

Lanthanide Metal-Organic Frameworks for Multispectral Radioluminescent Imaging

In this report, we describe the X-ray luminescent properties of two lanthanide-based nanoscale metal-frameworks (nMOFs) and their potential as novel platforms for optical molecular imaging techniques such as X-ray excited radioluminescence (RL) imaging. Upon X-ray irradiation, the nMOFs display sharp tunable emission peaks that span the visible to near-infrared spectral region (∼400-700 nm) based on the identity of the metal (Eu, Tb, or Eu/Tb). Surface modification of the nMOFs with polyethylene glycol (PEG) resulted in nanoparticles with enhanced aqueous stability that demonstrated both cyto- and hemo-compatibility important prerequisites for biological applications. Importantly, this is the first report to document and investigate the radioluminescent properties of lanthanide nMOFs. Taken together, the observed radioluminescent properties and low in vitro toxicity demonstrated by the nMOFs render them promising candidates for in vivo translation.

Tumor-Microenvironment-Triggered Ion Exchange of a Metal-Organic Framework Hybrid for Multimodal Imaging and Synergistic Therapy of Tumors

Nanotheranostic agents (NTAs) that integrate diagnostic capabilities and therapeutic functions have great potential for personalized medicine, yet poor tumor specificity severely restricts further clinical applications of NTAs. Here, a pro-NTA (precursor of nanotheranostic agent) activation strategy is reported for in situ NTA synthesis at tumor tissues to enhance the specificity of tumor therapy. This pro-NTA, also called PBAM, is composed of an MIL-100 (Fe)-coated Prussian blue (PB) analogue (K₂ Mn[Fe(CN)₆ ]) with negligible absorption in the near-infrared region and spatial confinement of Mn²⁺ ions. In a mildly acidic tumor microenvironment (TME), PBAM can be specifically activated to synthesize the photothermal agent PB nanoparticles, with release of free Mn²⁺ ions due to the internal fast ion exchange, resulting in the "ON" state of both T₁ -weighted magnetic resonance imaging and photoacoustic signals. In addition, the combined Mn²⁺ -mediated chemodynamic therapy in the TME and PB-mediated photothermal therapy guarantee a more efficient therapeutic performance compared to monotherapy. In vivo data further show that the pro-NTA activation strategy could selectively brighten solid tumors and detect invisible lymph node metastases with high specificity.

Evolving role of biomaterials in diagnostic and therapeutic radiation oncology

Radiation therapy to treat cancer has evolved significantly since the discovery of x-rays. Yet, radiation therapy still has room for improvement in reducing side effects and improving control of cancer. Safer and more effective delivery of radiation has led us to novel techniques and use of biomaterials. Biomaterials in combination with radiation and chemotherapy have started to appear in pre-clinical explorations and clinical applications, with many more on the horizon. Biomaterials have revolutionized the field of diagnostic imaging, and now are being cultivated into the field of theranostics, combination therapy, and tissue protection. This review summarizes recent development of biomaterials in radiation therapy in several application areas.

Auger Electrons Constructed Active Sites on Nanocatalysts for Catalytic Internal Radiotherapy

Excess electrons play important roles for the construction of superficial active sites on nanocatalysts. However, providing excess electrons to nanocatalysts in vivo is still a challenge, which limits the applications of nanocatalysts in biomedicine. Herein, auger electrons (AEs) emitted from radionuclide 125 (125I) are used in situ to construct active sites in a nanocatalyst (TiO2) and the application of this method is further extended to cancer catalytic internal radiotherapy (CIRT). The obtained 125I-TiO2 nanoparticles first construct superficial Ti3+ active sites via the reaction between Ti4+ and AEs. Then Ti3+ stretches and weakens the O-H bond of the absorbed H2O, thus enhancing the radiolysis of H2O molecules and generating hydroxyl radicals (•OH). All in vitro and in vivo results demonstrate a good CIRT performance. These findings will broaden the application of radionuclides and introduce new perspectives to nanomedicine.

Biomimetic nanoscale metal-organic framework harnesses hypoxia for effective cancer radiotherapy and immunotherapy

Tumor hypoxia presents a major impediment to effective cancer therapy with ionizing radiation and immune checkpoint inhibitors. Here we report the design of a biomimetic nanoscale metal–organic-framework (nMOF), Hf-DBP-Fe, with catalase-like activity to decompose elevated levels of H₂O₂ in hypoxic tumors to generate oxygen and hydroxyl radical. The generated oxygen attenuates hypoxia to enable radiodynamic therapy upon X-ray irradiation and fixes DNA damage while hydroxyl radical inflicts direct damage to tumor cells to afford chemodynamic therapy. Hf-DBP-Fe thus mediates effective local therapy of hypoxic cancer with low-dose X-ray irradiation, leading to highly immunogenic tumor microenvironments for synergistic combination with anti-PD-L1 immune checkpoint blockade. This combination treatment not only eradicates primary tumors but also rejects distant tumors through systemic anti-tumor immunity. We have thus advanced an nMOF-based strategy to harness hypoxic tumor microenvironments for highly effective cancer therapy using a synergistic combination of low dose radiation and immune checkpoint blockade.

Biomimetic Hf-DBP-Fe harnesses tumor hypoxia for cancer treatment via RT-RDT and CDT as well as synergistic combination with immune checkpoint blockade.

Design of a Functionalized Metal-Organic Framework System for Enhanced Targeted Delivery to Mitochondria

Mitochondria play a key role in oncogenesis and constitute one of the most important targets for cancer treatments. Although the most effective way to deliver drugs to mitochondria is by covalently linking them to a lipophilic cation, the in vivo delivery of free drugs still constitutes a critical bottleneck. Herein, we report the design of a mitochondria-targeted metal-organic framework (MOF) that greatly increases the efficacy of a model cancer drug, reducing the required dose to less than 1% compared to the free drug and ca. 10% compared to the nontargeted MOF. The performance of the system is evaluated using a holistic approach ranging from microscopy to transcriptomics. Super-resolution microscopy of MCF-7 cells treated with the targeted MOF system reveals important mitochondrial morphology changes that are clearly associated with cell death as soon as 30 min after incubation. Whole transcriptome analysis of cells indicates widespread changes in gene expression when treated with the MOF system, specifically in biological processes that have a profound effect on cell physiology and that are related to cell death. We show how targeting MOFs toward mitochondria represents a valuable strategy for the development of new drug delivery systems.

Revealing Mitochondrial Microenvironmental Evolution Triggered by Photodynamic Therapy

Mitochondrion is one of the most important organelles and becomes a target in many cancer therapeutic strategies. Mitochondrial microenvironments in response to therapeutic methods are the key to understand therapeutic mechanisms. However, they are almost rarely studied. Herein, the mitochondrial microenvironments, including mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) after different photodynamic therapy (PDT) dosages, were monitored by fluorescent imaging and compared among three cell lines (HepG2, MCF-7, and LO2). Furthermore, the fluctuations of intramitochondrial pHs were revealed via a plasmonic mitochondrion-targeting surface-enhanced Raman scattering (SERS) pH nanosensor. Results indicate that the MMP decreases gradually with the ROS generation and the cancerous cells exhibit less response to excess ROS relative to normal cells. On the other hand, the pH value in the mitochondria decreases initially and then increases when the amount of ROS increases. The LO2 cell is preliminarily evidenced to have a higher self-adjustment ability due to its better tolerance to differential intra/extracellular pHs. This study may provide a basis for an in-depth understanding of the mechanisms of the mitochondrial targeting-based PDT therapeutic processes. It is also helpful for more accurate and useful diagnosis according to intramitochondrial microenvironments and improvement on therapy efficiency of cancers.

A highly X-ray sensitive iridium prodrug for visualized tumor radiochemotherapy

Concomitant treatment of radiotherapy and chemotherapy is widely used in cancer therapy. The search for highly efficient radiochemotherapy drugs for tumor targeting therapy under image-guiding is of considerable interest. Herein we report an Ir-based prodrug Ir-NB with high sensitization efficiency for in vivo tumor microenvironment responsive cancer-targeted bioimaging radiochemotherapy. To the best of our knowledge, the sensitivity enhancement ratio (SER) of the Ir-NB prodrug is the highest among those reported for radiotherapy metal complex drugs. From detailed action mechanism study, we provide evidence that the prodrug is effectively suppresses the tumor growth through inducing mitochondrial dysfunction, and eventually amplifies the apoptotic signal pathway. This study provides an approach for the development of cancer theranostic agents for tumor radiotherapy.

A highly X-ray sensitive molecular prodrug, Ir-NB, was reported for visualized tumor radiochemotherapy. To our knowledge, the sensitivity enhancement ratio of the prodrug is the highest among the reported radiotherapy metal complexes drugs.

Full-Process Radiosensitization Based on Nanoscale Metal-Organic Frameworks

Full-process radiosensitization, that is, pre-increasing radiation sensitivity of cancer cells, magnifying •OH formation during ionizing irradiation, and intervention on the resultant DNA repair for final cells death, could enhance the overall radiotherapeutic effects, but has not yet been achieved. Herein, Hf-nMOFs with Fe³⁺ ions uniformly dispersed (Hf-BPY-Fe) were constructed to integratedly improve radiotherapeutic effects via a multifaceted mechanism. The in vitro experiments demonstrated that persistent reactive oxygen species stress from Hf-BPY-Fe-activated in situ Fenton reaction reassorted cell cycle distribution, consequently contributing to increased tumoral radiosensitivity to photon radiation. Upon irradiation during the course of radiation therapy, Hf⁴⁺ in Hf-BPY-Fe gave substantial amounts of high-energy electrons, which partially converted H₂O to •OH and, meanwhile, relaxed to a low-energy state in nMOF pores, leading to an electron-rich environment. These aggregated electrons facilitated the reduction from Fe³⁺ to Fe²⁺ and further promoted the production of •OH in the Fenton process to attack DNA. The Hf-BPY-Fe postponed the DNA damage response process by interfering with certain proteins involved in the DNA repair signaling pathway. The in vivo experiments showed improved radiotherapeutic effects from integrated contributions from Fe³⁺-based Fenton reaction and Hf⁴⁺-induced X-ray energy conversion in tumors. This work provides a nMOFs-based full-process radiosensitizing approach for better radiotherapeutic efficacy.

The Rational Design and Biological Mechanisms of Nanoradiosensitizers

Radiotherapy (RT) has been widely used for cancer treatment. However, the intrinsic drawbacks of RT, such as radiotoxicity in normal tissues and tumor radioresistance, promoted the development of radiosensitizers. To date, various kinds of nanoparticles have been found to act as radiosensitizers in cancer radiotherapy. This review focuses on the current state of nanoradiosensitizers, especially the related biological mechanisms, and the key design strategies for generating nanoradiosensitizers. The regulation of oxidative stress, DNA damage, the cell cycle, autophagy and apoptosis by nanoradiosensitizers in vitro and in vivo is highlighted, which may guide the rational design of therapeutics for tumor radiosensitization.

Ultrasmall BiOI Quantum Dots with Efficient Renal Clearance for Enhanced Radiotherapy of Cancer

Emerging strategies involving nanomaterials with high-atomic-number elements have been widely developed for radiotherapy in recent years. However, the concern regarding their potential toxicity caused by long-term body retention still limits their further application. In this regard, rapidly clearable radiosensitizers are highly desired for practical cancer treatment. Thus, in this work, ultrasmall BiOI quantum dots (QDs) with efficient renal clearance characteristic and strong permeability inside solid tumor are designed to address this issue. Additionally, considering that injection methods have great influence on the biodistribution and radiotherapeutic efficacy of radiosensitizers, two common injection methods including intratumoral injection and intravenous injection are evaluated. The results exhibit that intratumoral injection can maximize the accumulation of radiosensitizers within a tumor compared to intravenous injection and further enhance radiotherapeutic efficacy. Furthermore, the radiosensitizing effect of BiOI QDs is revealed, which is not only attributed to the radiation enhancement of high-Z elements but also is owed to the •OH production via catalyzing overexpressed H2O2 within a tumor by BiOI QDs under X-ray irradiation. As a result, this work proposes a treatment paradigm to employ ultrasmall radiosensitizers integrated with local intratumoral injection to realize rapid clearance and high-efficiency radiosensitization for cancer therapy.

Metal-Organic Frameworks for Biomedical Applications

Metal-organic frameworks (MOFs) are an interesting and useful class of coordination polymers, constructed from metal ion/cluster nodes and functional organic ligands through coordination bonds, and have attracted extensive research interest during the past decades. Due to the unique features of diverse compositions, facile synthesis, easy surface functionalization, high surface areas, adjustable porosity, and tunable biocompatibility, MOFs have been widely used in hydrogen/methane storage, catalysis, biological imaging and sensing, drug delivery, desalination, gas separation, magnetic and electronic devices, nonlinear optics, water vapor capture, etc. Notably, with the rapid development of synthetic methods and surface functionalization strategies, smart MOF-based nanocomposites with advanced bio-related properties have been designed and fabricated to meet the growing demands of MOF materials for biomedical applications. This work outlines the synthesis and functionalization and the recent advances of MOFs in biomedical fields, including cargo (drugs, nucleic acids, proteins, and dyes) delivery for cancer therapy, bioimaging, antimicrobial, biosensing, and biocatalysis. The prospects and challenges in the field of MOF-based biomedical materials are also discussed.

Single-Atom Catalysts in Catalytic Biomedicine

The intrinsic deficiencies of nanoparticle-initiated catalysis for biomedical applications promote the fast development of alternative versatile theranostic modalities. The catalytic performance and selectivity are the critical issues that are challenging to be augmented and optimized in biological conditions. Single-atom catalysts (SACs) featuring atomically dispersed single metal atoms have emerged as one of the most explored catalysts in biomedicine recently due to their preeminent catalytic activity and superior selectivity distinct from their nanosized counterparts. Herein, an overview of the pivotal significance of SACs and some underlying critical issues that need to be addressed is provided, with a specific focus on their versatile biomedical applications. Their fabrication strategies, surface engineering, and structural characterizations are discussed briefly. In particular, the catalytic performance of SACs in triggering some representative catalytic reactions for providing the fundamentals of biomedical use is discussed. A sequence of representative paradigms is summarized on the successful construction of SACs for varied biomedical applications (e.g., cancer treatment, wound disinfection, biosensing, and oxidative-stress cytoprotection) with an emphasis on uncovering the intrinsic catalytic mechanisms and understanding the underlying structure-performance relationships. Finally, opportunities and challenges faced in the future development of SACs-triggered catalysis for biomedical use are discussed and outlooked.

Recent advances in porphyrin-based nanocomposites for effective targeted imaging and therapy

Porphyrins are organic compounds that continue to attract much theoretical interest, and have been called the "pigments of life". They have a wide role in photodynamic and sonodynamic therapy, along with uses in magnetic resonance, fluorescence and photoacoustic imaging. There is a vast range of porphyrins that have been isolated or designed, but few of them have real clinical applications. Due to the hydrophobic properties of porphyrins, and their tendency to aggregate by stacking of the planar molecules they are difficult to work with in aqueous media. Therefore encapsulating them in nanoparticles (NPs) or attachment to various delivery vehicles have been used to improve delivery characteristics. Porphyrins can be used in a composite designed material with properties that allow specific targeting, immune tolerance, extended tissue lifetime and improved hydrophilicity. Drug delivery, healing and repairing of damaged organs, and cancer theranostics are some of the medical uses of porphyrin-based nanocomposites covered in this review.

miR-31 Modulates Liver Cancer HepG2 Cell Apoptosis and Invasion via ROCK1/F-Actin Pathways

PURPOSE

Liver cancer is one of the most common malignant tumor in the world. miR-31 is downregulated in liver cancer and associated with tumor growth and metastasis. However, the underlying mechanism remains unclear.

METHODS

Cellular apoptosis was detected via MTT, TUNEL assay, LDH release and Annexin V/PI flow-cytometry analysis. Cellular migration and invasion were measured by the Transwell chamber assay. Mitochondrial functions were evaluated via mitochondrial membrane potential JC-1 staining and mPTP opening assessment. The mitophagy activity was examined via Western blots.

RESULTS

In the present study, our results confirm that miR-31 promotes apoptosis and inhibits proliferation and metastasis in liver cancer HepG2 cells. In vitro, miR-31 promotes HepG2 cell apoptosis through the mitochondrial pathway as indicated by mitochondrial potential reduction, increased mPTP opening time, cty-c release and imbalance of pro- and anti-apoptotic proteins. Furthermore, miR-31 reduces the energy generation by inhibiting mitochondrial respiratory function. At last, it is demonstrated that miR-31 triggers the mitochondrial damage via ROCK1/F-actin pathway. Inhibiting the ROCK1/F-actin pathway abolishes the effects of miR-31 mimic on mitochondrial injury, apoptosis, proliferation arrest and migration inhibition.

CONCLUSION

Our results reveal that miR-31 can inhibit HepG2 cell survival and metastasis by activating the ROCK1/F-actin pathway.

Dual pH-triggered catalytic selective Mn clusters for cancer radiosensitization and radioprotection

Hypoxia is known to be a common feature within many types of solid tumors, which is closely related to the limited efficacy of radiotherapy. Meanwhile, due to the non-discriminatory killing effect of both normal and cancer cells during the radiation process, traditional radiosensitizers could bring severe non-negligible side-effects to the whole body. In this work, stable and atomically precise Mn clusters which possess efficient pH-triggered catalytic selective capacity are developed rationally. Mn clusters could efficiently catalyze oxygen production in an acidic tumor microenvironment, while exhibiting strong reducibility and free radical scavenging ability in neutral circumstances. In vivo experiments show that Mn clusters are able to enhance the radiotherapy effect in the mouse model of 4T1 tumors and protect normal tissues from radiation at the same time. Thus, the present work provides a novel dual-functional strategy to enhance radiotherapy-induced tumor treatment by improving tumor oxygenation and protect normal tissues from radiation simultaneously.

Organelle-localized radiosensitizers

This feature article highlights the recent advances of organelle-localized radiosensitizers and discusses the current challenges and future directions.

Nanoscintillator-Mediated X-Ray Induced Photodynamic Therapy for Deep-Seated Tumors: From Concept to Biomedical Applications

Photodynamic therapy (PDT) has shown great effectiveness in oncotherapy but has not been implemented in broad clinical applications because the limited penetration depth of the light used has been unable to reach deep-seated tumors. However, X-rays have been widely used in the clinical field for imaging and radiation therapy due to their excellent tissue penetration depth. Recently, X-rays have been established as an ideal excitation source for PDT, which holds great promise for breaking the depth limitation of traditional PDT for treatment of deep-seated tumors. This review aims to provide an overview of nanoscintillator-mediated X-ray induced PDT (X-PDT) including the concept, the design considerations of nanosensitizers for X-PDT, the modelling of nanosensitizer energy deposition, the putative mechanism by which X-PDT kills cells, and the prospects of future directions. We attempt to summarize the main developments that have occurred over the past decades. Possibilities and challenges for the clinical translation of X-PDT are also discussed.

Dancing with reactive oxygen species generation and elimination in nanotheranostics for disease treatment

Reactive oxygen species (ROS) play important roles in cell signaling and tissue homeostasis, in which the level of ROS is critical through the equilibrium between ROS generating and eliminating events. A disruption of the balance leads to disease development either by a surplus or a dearth of ROS, which requires ROS-modulating strategies to overturn the defect for disease treatment. Over the past decade, there have been tremendous advances in nanomedicine centering ROS generation and/or elimination as major mechanisms to treat a variety of diseases. In this review, we will discuss the research achievements on two opposite approaches of ROS-generating and ROS-eliminating strategies for treating cancer and other related diseases. Importantly, we will highlight the conceptual and strategic advances of ROS-mediated immunomodulation, including macrophage polarization, immunogenic cell death and T cell activation, which are currently rising as one of the mainstreams of cancer therapy. At the end, the future challenges and opportunities of mediating ROS-based mechanisms are envisioned. In light of the pleiotropic roles of ROS in different diseases, we hope this review is timely to deliver a clear logic of designing principles on ROS generation and elimination for different disease treatments.

Recent Progress of Nanoscale Metal-Organic Frameworks in Cancer Theranostics and the Challenges of Their Clinical Application

The growing incidence of cancer raises an urgent need to develop effective diagnostic and therapeutic strategies. With the rapid development of nanomedicine, nanoscale metal-organic frameworks (NMOFs) presented promising potential in various biomedical applications in the last 2 decades, especially in cancer theranostics. Due to the unique features of NMOFs, including structural diversities, enormous porosity, multifunctionality and biocompatibility, they have been widely used to deliver imaging contrast agents and therapeutic drugs. Moreover, multiple types of contrast agents, anti-cancer drugs and targeting ligands could be co-delivered through one single NMOF to enable combination therapy. Co-delivering system using NMOFs helped to avoid multidrug resistance, to reduce adverse effects, to achieve imaging-guided precise therapy and to enhance anti-cancer efficacy. This review summarized the recent research advances on the application of NMOFs in biomedical imaging and cancer treatments in the last few years. The current challenges that impeding their translation to clinical practices and the perspectives for their future applications were also highlighted and discussed.

Metal-Organic Frameworks as a Theranostic Nanoplatform for Combinatorial Chemophotothermal Therapy Adapted to Different Administration

With the rapid development of nanotechnology, nanomaterial drug delivery systems have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal-organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, we demonstrate an MOF as a theranostic nanoplatform to combine drug therapy and phototherapy after labeling targeting peptide iRGD. The micropore Fe-MOF was used as MRI agents for locating tumors and as nanocarriers to upload chemotherapeutic drugs. Moreover, MOF showed excellent targeting performance under different administration including intravenous injection for breast cancer and local instillation for bladder cancer. Notably, when irradiated with an 808 nm laser, the agent demonstrates the high efficacy of photothermal therapy and heat release efficiency of the drug around the tumor site. This combination therapy provides an alternative drug administration method and can be adapted to a series of cancer cell types and molecular targets associated with disease progression.

Multifunctional Nanoscale Metal-Organic Layers for Ratiometric pH and Oxygen Sensing

As a monolayered version of nanoscale metal-organic frameworks (nMOFs), nanoscale metal-organic layers (nMOLs) represent an emerging class of highly tunable two-dimensional materials for hierarchical functionalization and with facile access to analytes. Here we report the design of the first nMOL-based biosensor for ratiometric pH and oxygen sensing in mitochondria. Cationic Hf₁₂-Ru nMOL was solvothermally synthesized by laterally connecting Hf₁₂ secondary building units (SBUs) with oxygen-sensitive Ru(bpy)₃²⁺-derived DBB-Ru ligands (bpy = 2,2'-bipyridine). The Hf₁₂-Ru nMOL was then covalently functionalized with pH-sensitive fluorescein isothiocyanate and pH/oxygen-independent Rhodamine-B isothiocyanate through thiourea linkages to afford Hf₁₂-Ru-F/R as a mitochondria-targeted ratiometric sensor for pH and O₂ in live cells. High-resolution confocal microscope imaging with Hf₁₂-Ru-F/R revealed a positive correlation between pH and local O₂ concentration in mitochondria. Our work shows the potential of nMOL-based ratiometric biosensors in sensing and imaging of biologically important analytes in live cells.

MiR-506 Targets UHRF1 to Inhibit Colorectal Cancer Proliferation and Invasion via the KISS1/PI3K/NF-κB Signaling Axis

Background

The UHRF1 gene is an epigenetic modification factor that mediates tumor suppressor gene silencing in a variety of cancers. Related studies have reported that UHRF1 can inhibit the expression of the KISS1 gene. However, the regulatory mechanism underlying UHRF1 expression in colorectal cancer (CRC) is still unclear. The aim of this study was to gain a better understanding of the regulation of UHRF1 expression in CRC and to determine whether it regulates the mechanism by which KISS1 promotes CRC metastasis.

Methods

In the present study, the levels of miR-506, UHRF1 and KISS1 expression in CRC tissues and in human CRC cell lines were studied using quantitative real-time PCR (qRT-PCR) and Western blotting. Cell proliferation, migration, and invasion assays are used to detect cell proliferation, migration, and invasion. A dual-luciferase reporter system was used to confirm the target gene of miR-506.

Results

This study found that UHRF1 protein is highly expressed in CRC tissues and negatively correlated with KISS1 protein expression. UHRF1 overexpression activates the PI3K/NF-κB signaling pathway by inhibiting the mRNA expression levels of pathway mediators. Bioinformatics analysis and luciferase reporter gene assays confirmed that miR-506 targets UHRF1.

Conclusion

This study identified the regulation of UHRF1 expression in CRC and the mechanism of CRC metastasis. UHRF1 may be a new potential target molecule for future CRC metastasis treatment.