High Biocompatible ZIF-8 Coated by ZrO2 for Chemo-microwave Thermal Tumor Synergistic Therapy

Drug delivery system based on metal-organic framework improved 5-Fluorouracil against spring viremia of carp virus

Spring viremia of carp virus (SVCV), as a high pathogenicity pathogen, has seriously restricts the healthy and sustainable development of cyprinid farming industry. In this study, we selected 5-Fluorouracil (5-Fu) as the drug model based on zeolitic imidazolate framework-8 (ZIF-8) to construct a drug delivery system (5-Fu@ZIF-8), and the anti-SVCV activity was detected in vitro and in vivo. The results showed 5-Fu@ZIF-8 was uniform cubic particle with truncated angle and smooth surface, and the particle size was 90 nm. The anti-SVCV activity in vitro results showed that the highest inhibition rate of 5-Fu was 77.93% at 40 mg/L and the inhibitory concentration at half-maximal activity (IC50) was 20.86 mg/L. For 5-Fu@ZIF-8, the highest inhibition rate was 91.36% at 16 mg/L, and the IC50 value was 5.85 mg/L. In addition, the cell viability was increased by 18.1% after 5-Fu treatment. Similarly, after 5-Fu@ZIF-8 treatment, the cell viability increased by 27.3%. Correspondingly, in vivo experimental results showed the viral loads reduced by 18.1% on the days 7 and the survival rate increased to 19.4% at 80 mg/L after 5-Fu treatment. For 5-Fu@ZIF-8, the viral loads reduced by 41.2% and the survival rate increased to 54.8%. Mechanistically, 5-Fu inhibits viral replication by regulating p53 expression and promoting early apoptosis in infected cells. All results indicated that 5-Fu@ZIF-8 improved the anti-SVCV activity; it may be a potential strategy to construct a drug-loaded system with ZIF-8 as a carrier for the prevention and treatment of aquatic diseases.

Fe3O4@Chitosan@ZIF-8@RVG29, an anti-glioma nanoplatform guided by fixed and activated by alternating magnetic field

There is considerable interest in developing anti-glioma nanoplatforms. They make the all-in-one combination of therapies possible. Here we show how the selective Glioblastoma multiforme (GBM) cell killing of the here-established nanoplatforms increased after each coating and how the here-established vibration-inducing Alternating magnetic field (AMF) decreased the treatment time from 72 h to 30 s. Thanks to their magnetite core, these nanoplatforms can be guided to the tumor's specific site by a Fixed magnetic field, they bypass the Blood-Brain Barrier (BBB) and accumulate at the tumor site thanks to the RVG29 bonding to the G-protein on the ion-gated channel receptor known as the nicotinic acetylcholine receptor (nAchR), which expresses on BBB cells and overexpresses on GBM cells, and thanks to the positive charge gained by both chitosan and RVG29's peptide. Both ZIF-8 and its mediate adherence, Chitosan increases the drug loading capacity that stimuli response to the tumor's acidic environment. The Zn2+ ions generated from ZIF-8 sustained degradation in such an environment kill the GBM cells. Dynamic Light Scattering (DLS) evaluated these nanoplatform's mean size 155 nm indicating their almost optimum size for brain applications. Based on their elements' intrinsic properties, these nanoplatforms can enhance and combine other adjuvant therapies.

Tunable Zeolitic Imidazolate Framework-8 Nanoparticles for Biomedical Applications

Zeolite imidazole framework-8 (ZIF-8) is the most prestigious one among zeolitic imidazolate framework (ZIF) with tunable dimensions and unique morphological features. Utilizing its synthetic adjustability and structural regularity, ZIF-8 exhibits enhanced flexibility, allowing for a wide range of functionalities, such as loading of nanoparticle components while preserving biomolecules activity. Extensive efforts are made from investigating synthesis techniques to develop novel applications over decades. In this review, the development and recent progress of various synthesis approaches are briefly summarized. In addition, its interesting properties such as adjustable porosity, excellent thermal, and chemical stabilities are introduced. Further, five representative biomedical applications are highlighted based on above physicochemical properties. Finally, the remaining challenges and offered insights into the future outlook are also discussed. This review aims to understand the co-relationships between structures and biomedical functionalities, offering the opportunity to construct attractive materials with promising characteristics.

Preparation and biological evaluation of antibody targeted metal-organic framework drug delivery system (TDDS) in Her2 receptor-positive cells

In this study, we designed and prepared a trastuzumab-coupled drug delivery system with pH response characteristics using mesoporous zeolitic imidazolate framework-8 (ZIF-8) as the carrier, Trastuzumab@ZIF-8@DOX. As results, the targeted drug delivery system (TDDS) ultimately showed high drug loading and good biocompatibility. The cumulative curve of drug release indicated that the early leakage levels were low under neutral pH conditions. However, under acidic pH conditions, there was an effective enhancement in drug release, indicating the presence of an explicit pH-triggered drug release mechanism. The results indicate that the prepared nanoparticles have the potential to serve as drug delivery systems, as they can release the loaded drug in a controlled manner. The results of cellular uptake tests showed that the uptake of the nanoparticles was greatly enhanced by the internalization mediated by the HER2 antibody. This finding indicates that the prepared nanoparticles can selectively target cancer cells that overexpress HER2. When the doxorubicin dose was 5 μg/ml, the survival rate of SK-BR-3 cells (cancer cells) was 47.75 %, and the survival rate of HaCaT cells (healthy cells) was 75.25 % when co-cultured with both cells. The therapeutic efficacy of Trastuzumab@ZIF-8@DOX was assessed on BALB/c nude mice to validate its potential as an effective drug delivery system for tumor inhibition in vivo. In conclusion, these findings demonstrate the specificity-targeted and pH-responsive nature of this smart drug delivery system, highlighting its promising prospects for efficient and controllable cancer treatment applications.

Theranostic applications of peptide-based nanoformulations for growth factor defective cancers

Growth factors play a pivotal role in orchestrating cellular growth and division by binding to specific cell surface receptors. Dysregulation of growth factor production or activity can contribute to the uncontrolled cell proliferation observed in cancer. Peptide-based nanoformulations (PNFs) have emerged as promising therapeutic strategies for growth factor-deficient cancers. PNFs offer multifaceted capabilities including targeted delivery, imaging modalities, combination therapies, resistance modulation, and personalized medicine approaches. Nevertheless, several challenges remain, including limited specificity, stability, pharmacokinetics, tissue penetration, toxicity, and immunogenicity. To address these challenges and optimize PNFs for clinical translation, in-depth investigations are warranted. Future research should focus on elucidating the intricate interplay between peptides and nanoparticles, developing robust spectroscopic and computational methodologies, and establishing a comprehensive understanding of the structure-activity relationship governing peptide-nanoparticle interactions. Bridging these knowledge gaps will propel the translation of peptide-nanoparticle therapies from bench to bedside. While a few peptide-nanoparticle drugs have obtained FDA approval for cancer treatment, the integration of nanostructured platforms with peptide-based medications holds tremendous potential to expedite the implementation of innovative anticancer interventions. Therefore, growth factor-deficient cancers present both challenges and opportunities for targeted therapeutic interventions, with peptide-based nanoformulations positioned as a promising avenue. Nonetheless, concerted research and development endeavors are essential to optimize the specificity, stability, and safety profiles of PNFs, thereby advancing the field of peptide-based nanotherapeutics in the realm of oncology research.

A critical review on metal-organic frameworks (MOFs) based nanomaterials for biomedical applications: Designing, recent trends, challenges, and prospects

Nanomaterials (NMs) have garnered significant attention in recent decades due to their versatile applications in a wide range of fields. Thanks to their tiny size, enhanced surface modifications, impressive volume-to-surface area ratio, magnetic properties, and customized optical dispersion. NMs experienced an incredible upsurge in biomedical applications including diagnostics, therapeutics, and drug delivery. This minireview will focus on notable examples of NMs that tackle important issues, demonstrating various aspects such as their design, synthesis, morphology, classification, and use in cutting-edge applications. Furthermore, we have classified and outlined the distinctive characteristics of the advanced NMs as nanoscale particles and hybrid NMs. Meanwhile, we emphasize the incredible potential of metal-organic frameworks (MOFs), a highly versatile group of NMs. These MOFs have gained recognition as promising candidates for a wide range of bio-applications, including bioimaging, biosensing, antiviral therapy, anticancer therapy, nanomedicines, theranostics, immunotherapy, photodynamic therapy, photothermal therapy, gene therapy, and drug delivery. Although advanced NMs have shown great potential in the biomedical field, their use in clinical applications is still limited by issues such as stability, cytotoxicity, biocompatibility, and health concerns. This review article provides a thorough analysis offering valuable insights for researchers investigating to explore new design, development, and expansion opportunities. Remarkably, we ponder the prospects of NMs and nanocomposites in conjunction with current technology.

Advancements in Microwave Absorption Motivated by Interdisciplinary Research

Microwave absorption materials (MAMs) are originally developed for military purposes, but have since evolved into versatile materials with promising applications in modern technologies, including household use. Despite significant progress in bench-side research over the past decade, MAMs remain limited in their scope and have yet to be widely adopted. This review explores the history of MAMs from first-generation coatings to second-generation functional absorbers, identifies bottlenecks hindering their maturation. It also presents potential solutions such as exploring broader spatial scales, advanced characterization, introducing liquid media, utilizing novel toolbox (machine learning, ML), and proximity of lab to end-user. Additionally, it meticulously presents compelling applications of MAMs in medicine, mechanics, energy, optics, and sensing, which go beyond absorption efficiency, along with their current development status and prospects. This interdisciplinary research direction differs from previous research which primarily focused on meeting traditional requirements (i.e., thin, lightweight, wide, and strong), and can be defined as the next generation of smart absorbers. Ultimately, the effective utilization of ubiquitous electromagnetic (EM) waves, aided by third-generation MAMs, should be better aligned with future expectations.

A Comprehensive Review on Imperative Role of Ionic Liquids in Pharmaceutical Sciences

Ionic liquids (ILs) are poorly-coordinated ionic salts that can exist as a liquid at room temperatures (or <100 °C). ILs are also referred to as "designer solvents" because so many of them have been created to solve particular synthetic issues. ILs are regarded as "green solvents" because they have several distinctive qualities, including better ionic conduction, recyclability, improved solvation ability, low volatility, and thermal stability. These have been at the forefront of the most innovative fields of science and technology during the past few years. ILs may be employed in new drug formulation development and drug design in the field of pharmacy for various functions such as improvement of solubility, targeted drug delivery, stabilizer, permeability enhancer, or improvement of bioavailability in the development of pharmaceutical or vaccine dosage formulations. Ionic liquids have become a key component in various areas such as synthetic and catalytic chemistry, extraction, analytics, biotechnology, etc., due to their superior abilities along with highly modifiable potential. This study concentrates on the usage of ILs in various pharmaceutical applications enlisting their numerous purposes from the delivery of drugs to pharmaceutical synthesis. To better comprehend cuttingedge technologies in IL-based drug delivery systems, highly focused mechanistic studies regarding the synthesis/preparation of ILs and their biocompatibility along with the ecotoxicological and biological effects need to be studied. The use of IL techniques can address key issues regarding pharmaceutical preparations such as lower solubility and bioavailability which plays a key role in the lack of effectiveness of significant commercially available drugs.

Size-tunable nanogels for cascaded release of metronidazole and chemotherapeutic agents to combat Fusobacterium nucleatum-infected colorectal cancer

Bacteria play important roles in tumor formation, growth and metastasis through downregulating immune response and initiating drug resistance. Herein, size-tunable nanogels (NGs) have been developed to address the existing size paradox in tumor accumulation, intratumoral penetration and intracellular release of therapeutics for the treatment of Fusobacterium nucleatum (F. nucleatum)-infected colorectal cancer. Zinc-imidazolate frameworks with doxorubicin (DOX) loading and folate grafting (f-ZIFD) were mixed with metronidazole (MET) and encapsulated in NGs through thiol-ene click crosslinking of sulfhydryl hyaluronan, sulfhydryl alginate and 4-arm poly(ethylene glycol) acrylate. Hyaluronidase-initiated matrix degradation causes NG swelling to release sufficient MET and maintains a large size for an extended time period, and the gradually discharged f-ZIFD nanoparticles (NPs) from NGs exhibit acid-responsive intracellular release of DOX after folate-mediated internalization into tumor cells. The encapsulation into NGs significantly enhances the bioavailability and increases half-lives of MET and DOX by around 20 times. In the F. nucleatum-infected tumor model, the extended retention of swollen NGs and the efficient tumor infiltration and cellular uptake of the discharged f-ZIFD NPs cause 6 times higher DOX levels in tumors than that of free DOX administration. F. nucleatum promotes tumor cell proliferation and tumor growth, and the cascaded releases of MET and f-ZIFD NPs eliminate F. nucleatum to effectively inhibit tumor growth with a significant extension of animal survival. Thus, the hyaluronidase-mediated NG expansion and dual-responsive cascaded drug release have overcome challenges in the release regimen and size paradox of drug delivery carriers to combat bacteria-infected cancer.

Application of Zeolites and Zeolitic Imidazolate Frameworks in Dentistry-A Narrative Review

Zeolites and zeolitic imidazolate frameworks (ZIFs) are crystalline aluminosilicates with porous structure, which are closely linked with nanomaterials. They are characterized by enhanced ion exchange capacity, physical-chemical stability, thermal stability and biocompatibility, making them a promising material for dental applications. This review aimed to provide an overview of the application of zeolites and ZIFs in dentistry. The common zeolite compounds for dental application include silver zeolite, zinc zeolite, calcium zeolite and strontium zeolite. The common ZIFs for dental application include ZIF-8 and ZIF-67. Zeolites and ZIFs have been employed in various areas of dentistry, such as restorative dentistry, endodontics, prosthodontics, implantology, periodontics, orthodontics and oral surgery. In restorative dentistry, zeolites and ZIFs are used as antimicrobial additives in dental adhesives and restorative materials. In endodontics, zeolites are used in root-end fillings, root canal irritants, root canal sealers and bone matrix scaffolds for peri-apical diseases. In prosthodontics, zeolites can be incorporated into denture bases, tissue conditioners, soft denture liners and dental prostheses. In implantology, zeolites and ZIFs are applied in dental implants, bone graft materials, bone adhesive hydrogels, drug delivery systems and electrospinning. In periodontics, zeolites can be applied as antibacterial agents for deep periodontal pockets, while ZIFs can be embedded in guided tissue regeneration membranes and guided bone regeneration membranes. In orthodontics, zeolites can be applied in orthodontic appliances. Additionally, for oral surgery, zeolites can be used in oral cancer diagnostic marker membranes, maxillofacial prosthesis silicone elastomer and tooth extraction medicines, while ZIFs can be incorporated to osteogenic glue or used as a carrier for antitumour drugs. In summary, zeolites have a broad application in dentistry and are receiving more attention from clinicians and researchers.

Ionic liquids revolutionizing biomedicine: recent advances and emerging opportunities

Ionic liquids (ILs), due to their inherent structural tunability, outstanding miscibility behavior, and excellent electrochemical properties, have attracted significant research attention in the biomedical field. As the application of ILs in biomedicine is a rapidly emerging field, there is still a need for systematic analyses and summaries to further advance their development. This review presents a comprehensive survey on the utilization of ILs in the biomedical field. It specifically emphasizes the diverse structures and properties of ILs with their relevance in various biomedical applications. Subsequently, we summarize the mechanisms of ILs as potential drug candidates, exploring their effects on various organisms ranging from cell membranes to organelles, proteins, and nucleic acids. Furthermore, the application of ILs as extractants and catalysts in pharmaceutical engineering is introduced. In addition, we thoroughly review and analyze the applications of ILs in disease diagnosis and delivery systems. By offering an extensive analysis of recent research, our objective is to inspire new ideas and pathways for the design of innovative biomedical technologies based on ILs.

Biomimetic Metal-Chalcogenide Agents Enable Synergistic Cancer Therapy via Microwave Thermal-Dynamic Therapy and Immune Cell Activation

Microwave thermal dynamic therapy (MTDT), which combines thermal effects and reactive oxygen species (ROS) by microwave activation, seems to be a promising anticancer therapeutic method. A multifunctional agent for achieving synergistic localized cancer treatment is the key to exploit the strategy to inhibit tumor cell recurrence and metastasis. In the study, a ZIF-67 based theranostic agent loaded with metal-chalcogenide open framework 3 (MCOF3) and heat shock protein 70 (HSP70) as the inner component was studied, coupled with targeting cancer cell membrane (TCM) as the biomimetic outer shell. We found that metal ions in MCOF3 enabled the composite agents to show peroxide-like activity to produce •OH and destroy cancer cells. And then, the microwave (MW) thermal sensitizer of ZIF-67 was used to specifically convert the MW energy into thermal energy and selectively heat the tumor via the cell's targeting. Additionally, the effect of continuous MW thermal therapy has been shown to promote the expression of HSP70, and further activate the effector of CD4 T cell and CD8α T cell. As such, the agents effectively inhibit the tumor cell growth under MW irradiation in vitro and in vivo due to the synergistic effects of MTDT and immune cell activation. The study provides an emerging strategy to ablation cancer effectively.

Microwave-activated Cu-doped zirconium metal-organic framework for a highly effective combination of microwave dynamic and thermal therapy

Percutaneous microwave ablation (PMA) is a thermoablative method used as a minimally invasive treatment for liver cancer. However, the application of PMA is limited by its insufficient ROS generation efficiency and thermal effects. Herein, a new microwave-activated Cu-doped zirconium metal-organic framework (MOF) (CuZr MOF) used for enhanced PMA has a significantly improved microwave sensitizing effect. Owing to the strong inelastic collisions between ions confined in numerous micropores, CuZr MOF has strong microwave sensitivity and high thermal conversion efficiency, which can significantly improve microwave thermal therapy (MTT). Moreover, because of the existence of Cu2+ ions, a further benefit of CuZr MOF is their Fenton-like activity, in particular, microwaves used as an excitation source for microwave dynamic therapy (MDT) can improve the Fenton-like reaction to maximize the synergistic effectiveness of cancer therapy. Importantly, CuZr MOF can inhibit the production of heat shock proteins (HSPs) by producing abundant ROS to enhance tumor destruction. Mechanistically, we found that CuZr MOF + MW treatment modulates ferroptosis-mediated tumor cell death by targeting the HMOX1/GPX4 axis. In summary, this study develops a novel CuZr MOF microwave sensitizer with great potential for synergistic treatment of liver cancer by MTT and MDT.

A review of recent developments of metal-organic frameworks as combined biomedical platforms over the past decade

Metal-organic frameworks (MOFs), also called porous coordination polymers, represent a class of crystalline porous materials made up of organic ligands and metal ions/metal clusters. Herein, an overview of the preparation of different metal-organic frameworks and the recent advances in MOF-based stimuli-responsive drug delivery systems (DDSs) with the drug release mechanisms including pH-, temperature-, ion-, magnetic-, pressure-, adenosine-triphosphate (ATP)-, H₂S-, redox-, responsive, and photoresponsive MOF were rarely introduced. The combination therapy containing of two or more treatments can be enhanced treatment effectiveness through overcoming limitations of monotherapy. Photothermal therapy (PTT) combined with chemotherapy (CT), chemotherapy in combination with PTT or other combinations were explained to overcome drug resistance and side effects in normal cells as well as enhancing the therapeutic response. Integrated platforms containing of photothermal/drug-delivering functions with magnetic resonance imaging (MRI) properties exhibited great advantages in cancer therapy.

Boosting Glioblastoma Therapy with Targeted Pyroptosis Induction

Glioblastoma (GBM) is a highly aggressive cancer that currently lacks effective treatments. Pyroptosis has emerged as a promising therapeutic approach for cancer, but there is still a need for new pyroptosis boosters to target cancer cells. In this study, it is reported that Aloe-emodin (AE), a natural compound derived from plants, can inhibit GBM cells by inducing pyroptosis, making it a potential booster for pyroptosis-mediated GBM therapy. However, administering AE is challenging due to the blood-brain barrier (BBB) and its non-selectivity. To overcome this obstacle, AE@ZIF-8 NPs are developed, a biomineralized nanocarrier that releases AE in response to the tumor's acidic microenvironment (TAM). Further modification of the nanocarrier with transferrin (Tf) and polyethylene glycol-poly (lactic-co-glycolic acid) (PEG-PLGA) improves its penetration through the BBB and tumor targeting, respectively. The results show that AE-NPs (Tf-PEG-PLGA modified AE@ZIF-8 NPs) significantly increase the intracranial distribution and tumor tissue accumulation, enhancing GBM pyroptosis. Additionally, AE-NPs activate antitumor immunity and reduce AE-related toxicity. Overall, this study provides a new approach for GBM therapy and offers a nanocarrier that is capable of penetrating the BBB, targeting tumors, and attenuating toxicity.

AIEgens/Mitochondria Nanohybrids as Bioactive Microwave Sensitizers for Non-Thermal Microwave Cancer Therapy

Aggregation-induced emission luminogens (AIEgens) are widely used as photosensitizers for image-guided photodynamic therapy (PDT). Due to the limited penetration depth of light in biological tissues, the treatments of deep-seated tumors by visible-light-sensitized aggregation-induced emission (AIE) photosensitizers are severely hampered. Microwave dynamic therapy attracts much attention because microwave irradiation can penetrate very deep tissues and sensitize the photosensitizers to generate reactive oxygen species (ROS). In this work, a mitochondrial-targeting AIEgen (DCPy) is integrated with living mitochondria to form a bioactive AIE nanohybrid. This nanohybrid can not only generate ROS under microwave irradiation to induce apoptosis of deep-seated cancer cells but also reprogram the metabolism pathway of cancer cells through retrieving oxidative phosphorylation (OXPHOS) instead of glycolysis to enhance the efficiency of microwave dynamic therapy. This work demonstrates an effective strategy to integrate synthetic AIEgens and natural living organelles, which would inspire more researchers to develop advanced bioactive nanohybrids for cancer synergistic therapy.

Specific Nanodrug for Diabetic Chronic Wounds Based on Antioxidase-Mimicking MOF-818 Nanozymes

Chronic wound is a common complication for diabetic patients, which entails substantial inconvenience, persistent pain, and significant economic burden to patients. However, current clinical treatments for diabetic chronic wounds remain unsatisfactory. A prolonged but ineffective inflammation phase in chronic wounds is the primary difference between diabetic chronic wounds and normal wounds. Herein, we present an effective antioxidative system (MOF/Gel) for chronic wound healing of diabetic rats through integrating a metal organic framework (MOF) nanozyme with antioxidant enzyme-like activity with a hydrogel (Gel). MOF/Gel can continuously scavenge reactive oxygen species to modulate the oxidative stress microenvironment in diabetic chronic wounds, which leads to a natural transition from the inflammation phase to the proliferation phase. Impressively, the efficacy of one-time-applied MOF/Gel was comparable to that of the human epidermal growth factor Gel, a widely used clinical drug for various wound treatments. Such an effective, safe, and convenient MOF/Gel system can meet complex clinical demands.

Microfluidic Synthesis of the Tumor Microenvironment-Responsive Nanosystem for Type-I Photodynamic Therapy

Type I photosensitizers with aggregation-induced emission luminogens (AIE-gens) have the ability to generate high levels of reactive oxygen species (ROS), which have a good application prospect in cancer photodynamic therapy (PDT). However, the encapsulation and delivery of AIE molecules are unsatisfactory and seriously affect the efficiency of a practical therapy. Faced with this issue, we synthesized the metal-organic framework (MOF) in one step using the microfluidic integration technology and encapsulated TBP-2 (an AIE molecule) into the MOF to obtain the composite nanomaterial ZT. Material characterization showed that the prepared ZT had stable physical and chemical properties and controllable size and morphology. After being endocytosed by tumor cells, ZT was degraded in response to the acidic tumor microenvironment (TME), and then TBP-2 molecules were released. After stimulation by low-power white light, a large amount of •OH and H₂O₂ was generated by TBP-2 through type I PDT, thereby achieving a tumor-killing effect. Further in vitro cell experiments showed good biocompatibility of the prepared ZT. To the best of our knowledge, this report is the first on the microfluidic synthesis of multifunctional MOF for type I PDT in response to the TME. Overall, the preparation of ZT by the microfluidic synthesis method provides new insight into cancer therapy.

Synergetic Thermal Therapy for Cancer: State-of-the-Art and the Future

As a safe and minimal-invasive modality, thermal therapy has become an effective treatment in cancer treatment. Other than killing the tumor cells or destroying the tumor entirely, the thermal modality results in profound molecular, cellular and biological effects on both the targeted tissue, surrounding environments, and even the whole body, which has triggered the combination of the thermal therapy with other traditional therapies as chemotherapy and radiation therapy or new therapies like immunotherapy, gene therapy, etc. The combined treatments have shown encouraging therapeutic effects both in research and clinic. In this review, we have summarized the outcomes of the existing synergistic therapies, the underlying mechanisms that lead to these improvements, and the latest research in the past five years. Limitations and future directions of synergistic thermal therapy are also discussed.

Micro-Opening Ridged Waveguide Tumor Hyperthermia Antenna Combined with Microwave-Sensitive MOF Material for Tumor Microwave Hyperthermia Therapy

Microwave hyperthermia is an emerging minimally invasive therapy in which thermal damage and apoptosis of tumor cells are induced by local heating of tissues with microwave radiation. Recently, microwave hyperthermia has been widely used in clinical practice; however, uneven aggregation and dispersion of malignant tumors after microwave hyperthermia are the main problems associated with this method. In this work, a microridged waveguide tumor hyperthermia antenna with an operating frequency of 915 MHz was designed. Although its volume is only 6.6 cm3, it exhibited a highly focused heating effect, achieving rapid heating in a small area. However, microwave hyperthermia has several shortcomings. Microwaves cannot specifically identify and target tumors; this decreases the efficiency of the treatment if the temperature of the tumor site is not sufficiently high for its size and location. Therefore, Zr metal-organic framework (ZrMOF)-derived composite ZCNC was synthesized using the ultrasonic aerosol flow method, which has good microwave sensitization and biosafety. ZCNC reduced the damage to normal cells and greatly improved the tumor treatment effect of microwave hyperthermia (tumor inhibition rate reached 78.01%). Thus, the proposed strategy effectively improves the current clinical microwave hyperthermia treatment method.

Polydopamine-modified ZIF-8 nanoparticles as a drug carrier for combined chemo-photothermal osteosarcoma therapy

Single chemotherapy often causes severe adverse effects and chemoresistance which limits therapeutic efficacy. Recently, combination of chemotherapy with photothermal therapy (PTT) have received broad attention for synergistic treatment of osteosarcoma, ultimately resulting in the enhancement of therapeutic efficacy of anticancer drugs. In this study, we have developed a novel drug delivery system based on polydopamine (pDA)-modified ZIF-8 nanoparticles loaded with methotrexate (MTX) (pDA/MTX@ZIF-8 NPs). Herein, pDA modification avoided the explosive release of the drug, and improved the biocompatibility and near-infrared (NIR) light absorbance performance of nanoparticles. The as-prepared pDA/MTX@ZIF-8 NPs could be used as drug targeting delivery system and simultaneously displayed excellent photothermal effects under NIR irradiation. Biology assays in vitro indicated that the pDA/MTX@ZIF-8 NPs were able to efficiently induce MG63 cell apoptosis through reducing mitochondrial membrane potentials (MMPs), and the introduction of photothermal agents enhanced the antitumor effect and decreased the dose of chemotherapeutic drugs. Moreover, the optimized pDA/MTX@ZIF-8 NPs (40 μg/mL) exhibited better photothermal conversion performance and facilitated tumor cells death. These results triumphantly exhibit that the pDA/MTX@ZIF-8 NPs have a synergistic effect of chemo-photothermal therapy (combination index CI = 0.346) and excellent biocompatibility, which has unexceptionable prospects for the therapy of osteosarcoma.

A core-shell liquid metal-Cu nanoparticle with glutathione consumption via an in situ replacement strategy for tumor combination treatment of chemodynamic, microwave dynamic and microwave thermal therapy

The presence of high content glutathione (GSH) provides an effective "protective shield" for tumor cells, which undoubtedly is a huge impediment to reactive oxygen species (ROS)-based treatment. Fortunately, divalent copper (Cu²⁺) can not only consume GSH, destroying the protection mechanism of GSH, but also can be reduced to Cu⁺ with excellent Fenton-like reaction activity. Hence, capitalizing on the properties of liquid metals, we introduced Cu with three different valances via an in situ replacement reaction. A stable core-shell liquid-metal based "Cu storage pool" was obtained. It can effectively deplete GSH within the cells, and simultaneously produce ·OH through a Fenton-like reaction, further improving the effect of chemodynamic therapy (CDT). Under microwave irradiation, it is also capable of producing a large amount of ROS to promote tumor treatment. In addition, the loading of ionic liquid endows LZC@IL nanoparticles with certain microwave heating performance, which is able to augment microwave thermal therapy (MWTT). With the combination of CDT, microwave dynamic therapy (MDT) and MWTT, LZC@IL has an excellent effect on tumor elimination. This work offers a new idea for the application of liquid metals and the combined treatment of tumors, which has potential application value.

Lanthanide europium MOF nanocomposite as the theranostic nanoplatform for microwave thermo-chemotherapy and fluorescence imaging

Backgrounds

Microwave sensitization nanoplatform, integrating multiple functional units for improving tumor selectivity, is of great significance for clinical tumor microwave treatment. Lanthanide europium metal organic framework (EuMOF) is expected to be a theranostic nanoplatform owing to its unique luminescent and microwave sensitization properties. However, it is difficult to be applied to complicated biological systems for EuMOF due to its rapid degradation induced by the solvent molecular and ionic environment. In this work, a luminescent EuMOF nanocomposite (EuMOF@ZIF/AP-PEG, named EZAP) was designed, which brought the multifunctional characteristics of microwave sensitization, fluorescence imaging and drug loading.

Results

Lamellar EuMOF was synthesized by a hydrothermal method. Through the charge adsorption mechanism, the zeolite imidazole framework (ZIF) structure was intensively assembled on the surface of EuMOF to realize the protection. Then, through in-situ Apatinib drug loading and PEG modification, EZAP nanocomposite was finally obtained. Apatinib (AP) was a kind of chemotherapy drug approved by Food and Drug Administration for targeted therapy of tumors. PEG modification increased long-term circulation of EZAP nanocomposite. The physical and chemical structure and properties of EuMOF@ZIF (EZ) were systematically represented, indicating the successful synthesis of the nanocomposite. The toxic and side effects were negligible at a safe dose. The growth of human liver cancer cells and murine liver cancer cells in vitro was significantly inhibited, and the combined microwave-thermal therapy and chemotherapy in vivo achieved high anti-cancer efficacy. Moreover, EZAP nanocomposite possessed bright red fluorescence, which can be applied for tumor imaging in tumor-bearing mice in vivo.

Conclusion

Therefore, EZAP nanocomposite showed high microwave sensitization, excellent fluorescence properties and outstanding drug loading capacity, establishing a promising theranostic nanoplatform for tumor therapy and fluorescence imaging. This work proposes a unique strategy to design for the first time a multifunctional nanoplatform with lanthanide metal organic frameworks for biological applications in tumor therapy and diagnosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01335-7.

Visualization of the Final Stage of Sintering in Nanoceramics with Atomic Resolution

The deep understanding of the sintering mechanism is pivotal to optimizing denser ceramics production. Although several models explain the sintering satisfactorily on the micrometric scale, the extrapolation for nanostructured systems is not trivial. Aiming to provide additional information about the particularities of the sintering at the nanoscale, we performed in situ experiments using high-resolution transmission electron microscopy (HRTEM). We studied the pore elimination process in a ZrO₂ thin film and identified a high anisotropic pore elimination. Interestingly, there is a redistribution of the atoms from the rough surface in the solid-gas surface, followed by the atom attachment in a faceted surface. Finally, we found evidence of the pore acting as a pin, reducing the GB mobility. These findings certainly can contribute to enhance the kinetic models to describe the densification process of systems at the nanoscale.

Metal-Organic Frameworks for Bioimaging: Strategies and Challenges

Metal-organic frameworks (MOFs), composited with metal ions and organic linkers, have become promising candidates in the biomedical field own to their unique properties, such as high surface area, pore-volume, tunable pore size, and versatile functionalities. In this review, we introduce and summarize the synthesis and characterization methods of MOFs, and their bioimaging applications, including optical bioimaging, magnetic resonance imaging (MRI), computed tomography (CT), and multi-mode. Furthermore, their bioimaging strategies, remaining challenges and future directions are discussed and proposed. This review provides valuable references for the designing of molecular bioimaging probes based on MOFs.

Current status and future prospects of nanoscale metal–organic frameworks in bioimaging

The importance of diagnosis and in situ monitoring of lesion regions and transportation of bioactive molecules has a pivotal effect on successful treatment, reducing side effects, and increasing the chances of survival in the case of diseases.

Curcumin doped zeolitic imidazolate framework nanoplatform as a multifunctional nanocarrier for tumor chemo/immunotherapy

Curcumin as a hydrophobic polyphenol has great potential for tumor therapy, yet rapid degradation and hydrophobicity severely impair its therapeutic effect in the clinic. Herein, we report a novel strategy...

Super-assembled silica nanoprobes for intracellular Zn(II) sensing and reperfusion injury treatment through in situ MOF crystallization

The production of excess free zinc ions (Zn²⁺) in cells has been identified as an important cause of cell injury or apoptosis after ischemia reperfusion. Thus, developing a nanosystem with multiple therapeutic functions to significantly eliminate multiple cell injury factors is of great interest. Here, a super-assembled nanosystem consisting of a polyethylene glycol (PEG) surface-modified mesoporous silica nanoparticle (MSN) encapsulating 2-methylimidazole (2MI) and a Zn²⁺ probe (PZn) was fabricated. The 2MI-P@MSN nanoassemblies showed a "turn-on" fluorescence signal at 476 nm toward zinc ions due to the presence of PZn. Besides, zeolitic imidazolate framework-8 (ZIF-8) could be assembled on the site intracellularly after 2MI chelating with free zinc ions. The experimental results revealed that 2MI-P@MSN exhibited excellent biocompatibility and non-cytotoxicity, and was able to provide satisfactory protection to OGD/R-treated cells based on zinc ion adsorption and the antioxidant effect of ZIF-8, which could effectively improve the survival rate of reperfusion injury cells from 52% to 73%. Notably, selective and quantitative sensing of Zn²⁺ was successfully carried out in the cells. This strategy highlights the potential of the detection, absorption and assembly of excess zinc ions simultaneously for cell therapy, which provides a promising therapeutic method for ischemic stroke, oxidative damage and diseases associated with zinc ion accumulation.

A Novel H2O2 Generator for Tumor Chemotherapy-Enhanced CO Gas Therapy

Carbon monoxide (CO) gas therapy is a promising cancer treatment. However, gas delivery to the tumor site remains problematic. Proper tunable control of CO release in tumors is crucial to increasing the efficiency of CO treatment and reducing the risk of CO poisoning. To overcome such challenges, we designed ZCM, a novel stable nanotechnology delivery system comprising manganese carbonyl (MnCO) combined with anticancer drug camptothecin (CPT) loaded onto a zeolitic imidazole framework-8 (ZIF-8). After intravenous injection, ZCM gradually accumulates in cancerous tissues, decomposing in the acidic tumor microenvironment, releasing CPT and MnCO. CPT acts as a chemotherapy agent destroying tumors and producing copious H2O2. MnCO can react with the H2O2 to generate CO, powerfully damaging the tumor. Both in vitro and in vivo experiments indicate that the ZCM system is both safe and has excellent tumor inhibition properties. ZCM is a novel system for CO controlled release, with significant potential to improve future cancer therapy.

Recent Advances in Ionic Liquids in Biomedicine

The use of ionic liquids and deep eutectic solvents in biomedical applications has grown dramatically in recent years due to their unique properties and their inherent tunability. This review will introduce ionic liquids and deep eutectics and discuss their biomedical applications, namely solubilization of drugs, creation of active pharmaceutical ingredients, delivery of pharmaceuticals through biological barriers, stabilization of proteins and other nucleic acids, antibacterial agents, and development of new biosensors. Current challenges and future outlooks are discussed, including biocompatibility, the potential impact of the presence of impurities, and the importance of understanding the microscopic interactions in ionic liquids in order to design task-specific solvents.

Ferrous ions doped layered double hydroxide: smart 2D nanotheranostic platform with imaging-guided synergistic chemo/photothermal therapy for breast cancer

Developing simple and efficient nanotheranostic platforms with behavior responsive to the acid microenvironment of a tumor is of great significance for accurate tumor diagnosis and therapy. In this study, a smart 2D nanotheranostic platform has been successfully fabricated by doping functional ferrous ions into as-synthesized MgAl-layered double hydroxide (LDH) with doxurubicin (DOX) loading to form Fe-LDH/DOX NPs, which achieved magnetic resonance imaging (MRI)-guided synergistic chemo/photothermal therapy for breast cancer. The doping of ferrous ions into Fe-LDH/DOX enabled a strong photo-induced heating ability with a high photothermal conversion efficiency of 45.67%, which could be combined with the antitumor drug DOX to achieve the synergistic effect of photothermal therapy (PTT) and chemotherapy for killing tumor cells. Additionally, its in vitro pH-dependent degradation behavior and T₂-weighted MRI effect revealed that the as-prepared Fe-LDH/DOX is sensitive to the tumor acid microenvironment. Most importantly, the growth rate of tumors in 4T1 bearing mice could be effectively inhibited after the synergistic treatment of PTT and chemotherapy by Fe-LDH/DOX. These results show that doping functional metal ions into LDH NPs may open a novel approach to fabricating an LDH NP-based nanotheranostics platform with advanced diagnostic and therapeutic performances.

Nanoengineered biomimetic Cu-based nanoparticles for multifunational and efficient tumor treatment

The microwave dynamic therapy (MDT) mediated by cytotoxic reactive oxygen species (ROS) is a promising anticancer therapeutic method. However, the therapeutic efficiency of MDT is restricted by several limitations including insufficient ROS generation, strong proangiogenic response, and low tumor-targeting efficiency. Herein, we find that Cu-based nanoparticles can produce oxygen under microwave (MW) irradiation to raise the generation of ROS, such as •O₂, •OH and ¹O₂, especially •O₂. On this basis, a nanoengineered biomimetic strategy is designed to improve the efficiency of MDT. After intravenous administration, the nanoparticles accumulate to the tumor site through targeting effect mediated by biomimetic modification, and it can continuously produce oxygen to raise the levels of ROS in tumor microenvironment under MW irradiation for MDT. Additionally, Apatinib is incorporated as antiangiogenic drug to downregulate the expression of vascular endothelial growth factor (VEGF), which can effectively inhibit the tumor angiogenesis after MDT. Hence, the tumor inhibition rate is as high as 96.79%. This study provides emerging strategies to develop multifunctional nanosystems for efficient tumor therapy by MDT.

Hyaluronic acid coating on the surface of curcumin-loaded ZIF-8 nanoparticles for improved breast cancer therapy: An in vitro and in vivo study

Despite developments in surgery and chemotherapy, effective treatment of breast cancer is still an urgent problem owing to recurrence and metastasis. By combining the advantages of curcumin (Cur), zeolitic imidazolate framework-8 nanoparticles (ZIF-8), and hyaluronic acid (HA) in breast cancer therapy, Cur-loaded and HA-coated ZIF-8 (Cur@ZIF-8@HA) were synthesized using a method based on the pH-dependent solubility of Cur and the electrostatic interactions between zinc ions and carboxyl groups of HA. Cur@ZIF-8 were also prepared as a control group. Comprehensive comparisons of the physicochemical properties and anticancer activities of Cur@ZIF-8@HA and Cur@ZIF-8 were conducted. The results indicated that the degradation of Cur during the synthesis of Cur@ZIF-8 was negligible. The obtained Cur@ZIF-8 and Cur@ZIF-8@HA were truncated cubes with hydrodynamic diameters of 174 and 217 nm, respectively. Cur@ZIF-8@HA possessed better stability during storage in different media, a slower drug release rate under neutral and acidic conditions, and a greater inhibitory effect on breast cancer than Cur@ZIF-8. For 4T1 cells, treatment using Cur@ZIF-8@HA induced more cellular uptake and higher cytotoxicity, accompanied by higher lactate dehydrogenase release, cell cycle arrest in G2/M and S phases, production of reactive oxygen species, and apoptosis. In 4T1 tumor-bearing mice models, Cur@ZIF-8@HA showed a stronger inhibitory effect on tumor growth and pulmonary metastasis. Therefore, Cur@ZIF-8@HA might hold great potential as an agent for the effective therapy of breast cancer.

Glutathione-depleting nanoplatelets for enhanced sonodynamic cancer therapy

In combating cancer, ultrasound (US)-triggered sonodynamic therapy (SDT) manifests a wide range of promising applications as a noninvasive treatment modality, thus showing potential to overcome the shortcomings and disadvantages of conventional photodynamic therapy (PDT). Reactive oxygen species (ROS)-based therapy is practically destroyed by the high concentration of glutathione (GSH) inside tumors, and depleting GSH to improve the outcome of SDT is indeed a great challenge. Herein, we designed GSH-depleting nanoplatelets for enhanced sonodynamic cancer therapy. A platelet membrane coated nanosystem (PSCI) has been designed and tested comprising mesoporous silica nanoparticles (MSNs) which have been loaded with cinnamaldehyde (CA) as an oxidative stress amplifier. The inner layer comprises the sonosensitizer IR780 and the oxidative stress amplifier CA, whereas the platelet membranes (PM) were designed and utilized as an outer layer that can target tumors, thereby enhancing the effectiveness of SDT by attenuating the capability of tumor cells for scavenging ROS with GSH. SDT and cinnamaldehyde amplify oxidative stress by acting synergistically, leading to the preferential destruction of cancer cells in vitro and in vivo. It is hoped that next-generation tumor SDT treatments will find their way with the help of this strategy.

Pressure-induced amorphous zeolitic imidazole frameworks with reduced toxicity and increased tumor accumulation improves therapeutic efficacy In vivo

Zeolitic Imidazole Frameworks (ZIFs) are widely applied in nanomedicine for their high drug loading, suitable pore size, pH-responsive drug release, and so on. However, fast drug release during circulation, unexpected toxicity to mice major organs, undesirable long-term accumulation in the lung and even death currently hinder their in vivo biomedical applications. Herein, we report an amorphous ZIF-8 (aZIF-8) with high loading of 5-Fu through pressure-induced amorphization. This nano-system avoids early drug release during circulation and provides tumor microenvironment-responsive drug release with improved in vitro cell viability, and survival rate in in vivo evaluations as compared to ZIF-8. Furthermore, aZIF-8 shows longer blood circulation and lower lung accumulation than ZIF-8 at same injected doses. Less drug release during circulation, longer blood circulation, and better biocompatibility of aZIF-8/5-Fu significantly improves its therapeutic efficacy in ECA-109 tumor-bearing mouse, and result in 100% survival rate over 50 days after treatment. Therefore, aZIF-8 with favorable biocompatibility and long blood circulation is expected to be a promising nano-system for efficacious cancer therapy in vivo.

Development of MOF "Armor-Plated" Phycocyanin and Synergistic Inhibition of Cellular Respiration for Hypoxic Photodynamic Therapy in Patient-Derived Xenograft Models

Significant progress has been made in the use of phycocyanin (PC) as a photosensitizer (PS) agent for photodynamic therapy (PDT). The clinical use of PC, however, has been limited by its poor stability, unfavorable pharmacokinetics, limited tumor cell uptake, and the hypoxic nature of the tumor microenvironment. In this study, a novel biomimetic mineralization approach is described for encapsulating PC using zeolitic imidazolate framework-8 (ZIF-8), after which MPEG₂₀₀₀ -COOH is further utilized as an anchor on the ZIF/PC complex in order to yield MPEG₂₀₀₀ -ZIF/PC composites (PMs). These PMs are then used as a stable reinforced PS for PDT, effectively improving the intracellular delivery of this protein PS. In contrast to prior studies that have sought to overcome intratumoral hypoxia via increasing oxygen delivery to the tumor site, the mitochondrial complex I inhibitor papaverine (PPV) is instead utilized to reduce intratumor oxygen consumption in an effort to augment the PDT efficacy of the PMs. It is found that this combination treatment strategy markedly improves the antitumor properties of these PMs both in vitro and in patient-derived xenograft (PDX) models without inducing significant side effects. It is therefore proposed that the "armor-plating" of protein PS agents with ZIF-8 in combination with PPV may be a promising approach to precision medicine-mediated tumor treatment.

Development of MOF Reinforcement for Structural Stability and Toughness Enhancement of Biodegradable Bioinks

Three-dimensional (3D) bioprinting is a technology that can precisely fabricate customized tissues and organs. Hydrogel materials that can embed living cells for use in 3D printing are called bioinks. However, there are only limited options of bioinks currently because they require the following features at once, such as printability, repetitive layer-by-layer stacking (stackability), structure stabilization, and biological properties. A polyurethane-gelatin double network hydrogel bioink was previously reported to own tunable modulus through changing the solid content, but cell viability at the high solid content is inevitably reduced. In the present study, the reinforcement effects of a metal-organic framework (MOF), zeolitic imidazolate framework-8 (ZIF-8), in the PUG bioink were evaluated. The printability, stackability, thermoresponsiveness, and shear-thinning behavior of the PUG-ZIF-8 composite hydrogels were examined. It was found that the PUG composite hydrogel containing 1250 μg/mL ZIF-8 crystals showed significant structural stability and modulus enhancement (∼2.5-fold). However, the PUG bioink containing 1250 μg/mL ZIF-8 crystals may lead to cell senescence or death. The cytocompatible concentration of ZIF-8 crystals in the bioink was about 875 μg/mL, and this concentration was much higher than the reported tolerable amount (∼50 μg/mL) of ZIF-8 for biomedical applications. The strong reinforcement effect of ZIF-8 and the drug-loading/sensing possibilities of MOFs may open new opportunities for using MOFs in 3D bioprinting applications.

Yolk–shell magnetic composite Fe3O4@Co/Zn-ZIF for MR imaging-guided chemotherapy of tumors in vivo

The yolk–shell composites Fe₃O₄@Co/Zn-ZIF exhibited high doxorubicin loading capacity, pH-responsive release characteristics, and strong T₂-weighted MR imaging contrast enhancement, and were used for MR imaging-guided chemotherapy of tumors in vivo.

Regulating glucose metabolism using nanomedicines for cancer therapy

The regulation of glucose metabolism is a research focus in cancer treatment. Glucose metabolism is essential for maintaining the growth and proliferation of tumor cells, thus offering us great opportunities for tumor treatment. Recently, much progress has been made in efficient cancer treatment by regulating the pathway of glucose metabolism with nanomedicines due to the rapid development of nanotechnology and promising drug targets. In this review, we first introduced the pathway of cell energy supply from the perspective of aerobic and anaerobic processes. Then, we discussed the recent research progress in regulating glucose metabolism for various tumor resistance strategies including heat resistance, multiple drug resistance, and hypoxia. Finally, we presented the prospects and challenges of developing multifunctional nanoagents for efficient chemotherapy, hyperthermia, dynamic therapy and so on by regulating glucose metabolism.

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.

Mineralization of pH-Sensitive Doxorubicin Prodrug in ZIF-8 to Enable Targeted Delivery to Solid Tumors

The zeolitic imidazolate framework (ZIF-8), composed of zinc ion and dimethylimidazole, is widely used in drug delivery because of the easy fabrication process and the good biosafety. However, ZIF-8 suffers from low affinity to nonelectric-rich drugs and does not have surface functional groups. Here, to deliver doxorubicin (DOX) with ZIF-8 to specific target sites, DOX was first modified with a pH-sensitive linker containing two carboxyl groups to form the inactive prodrug CAD and subsequently seeded inside ZIF-8 by a 5 min mineralization process. CAD has high affinity to ZIF-8 because of the carboxyl groups and can anchor to the ZIF-8 surface to enable the surface modification with folic acid for tumor targeting. Moreover, the DOX release is precisely controlled by three steps of acidic pH response, with the dissociation of the FA layer, the breakdown of the ZIF-8 structure, and the cleavage of the pH-sensitive linker in prodrug. This novel "prodrug-ZIF-8" strategy has opened a new horizon in drug delivery.