Nanomedicine Applications of Hybrid Nanomaterials Built from Metal-Ligand Coordination Bonds: Nanoscale Metal-Organic Frameworks and Nanoscale Coordination Polymers

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

Recent Progress in Metal-Free Covalent Organic Frameworks as Heterogeneous Catalysts

Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with conventional porous materials such as inorganic zeolite, active carbon, and metal-organic frameworks, COFs are a new type of porous materials with well-designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal-free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF-based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.

The Progress and Prospect of Zeolitic Imidazolate Frameworks in Cancer Therapy, Antibacterial Activity, and Biomineralization

The progressive development of zeolitic imidazolate frameworks (ZIFs), as a subfamily of metal-organic frameworks (MOFs), and their unique features, including tunable pore size, large surface area, high thermal stability, and biodegradability/biocompatibility, have made them attractive in the field of biomedicine, especially for drug delivery and biomineralization applications. The high porosity of ZIFs gives them the opportunity for encapsulating a high amount of therapeutic drugs, proteins, imaging cargos, or a combination of them to construct advanced multifunctional drug delivery systems (DDSs) with combined therapeutic and imaging capabilities. This review summarizes recent strategies on the design and fabrication of ZIF-based nansystems and their exploration in the biomedical field. First, recent developments for the adjustment of particle size, functionality, and morphology of ZIFs are discussed, which are important for achieving optimized therapeutic/theranostic nanosystems. Second, recent trends on the application of ZIF nanocarriers for the loading of diverse cargos, including anticancer medicines, antibiotic drugs, enzymes, proteins, photosensitizers, as well as imaging and photothermal agents, are investigated in order to understand how multifunctional DDSs can be designed based on the ZIF nanoparticles to treat different diseases, such as cancer and infection. Finally, prospects on the future research direction and applications of ZIF-based nanomedicines are discussed.

Biomedical Applications of Metal Organic Polygons and Polyhedra (MOPs)

Since the discovery and structural characterization of metal organic polygons and polyhedra (MOPs), scientists have explored their potential in various applications like catalysis, separation, storage, and sensing. In recent years, scientists have explored the potential of supramolecular MOPs in biomedical application. Pioneering works by Ehrlich, Rosenberg, Lippard, Stang and others have demonstrated that MOPs have great potential as a novel class of metallo-therapeutics that can deliver cargoes (drugs and dyes) selectively. In this article, we document the progress made over the past two decades on the biomedical applications of MOPs and discuss the future prospects of this emerging field.

Metal-Organic Framework Nanoparticles Induce Pyroptosis in Cells Controlled by the Extracellular pH

Ion homeostasis is essential for cellular survival, and elevated concentrations of specific ions are used to start distinct forms of programmed cell death. However, investigating the influence of certain ions on cells in a controlled way has been hampered due to the tight regulation of ion import by cells. Here, it is shown that lipid-coated iron-based metal-organic framework nanoparticles are able to deliver and release high amounts of iron ions into cells. While high concentrations of iron often trigger ferroptosis, here, the released iron induces pyroptosis, a form of cell death involving the immune system. The iron release occurs only in slightly acidic extracellular environments restricting cell death to cells in acidic microenvironments and allowing for external control. The release mechanism is based on endocytosis facilitated by the lipid-coating followed by degradation of the nanoparticle in the lysosome via cysteine-mediated reduction, which is enhanced in slightly acidic extracellular environment. Thus, a new functionality of hybrid nanoparticles is demonstrated, which uses their nanoarchitecture to facilitate controlled ion delivery into cells. Based on the selectivity for acidic microenvironments, the described nanoparticles may also be used for immunotherapy: the nanoparticles may directly affect the primary tumor and the induced pyroptosis activates the immune system.

Metal-organic Nanopharmaceuticals

Coordinative interactions between multivalent metal ions and drug derivatives with Lewis base functions give rise to nanoscale coordination polymers (NCPs) as delivery systems. As the pharmacologically active agent constitutes a main building block of the nanomaterial, the resulting drug loadings are typically very high. By additionally selecting metal ions with favorable pharmacological or physicochemical properties, the obtained NCPs are predominantly composed of active components which serve individual purposes, such as pharmacotherapy, photosensitization, multimodal imaging, chemodynamic therapy or radiosensitization. By this approach, the assembly of drug molecules into NCPs modulates pharmacokinetics, combines pharmacological drug action with specific characteristics of metal components and provides a strategy to generate tailorable multifunctional nanoparticles. This article reviews different applications and recent examples of such highly functional nanopharmaceuticals with a high 'material economy'. Lay Summary: Nanoparticles, that are small enough to circulate in the bloodstream and can carry cargo molecules, such as drugs, imaging or contrast agents, are attractive materials for pharmaceutical applications. A high loading capacity is a generally aspired parameter of nanopharmaceuticals to minimize patient exposure to unnecessary nanomaterial. Pharmaceutical agents containing Lewis base functions in their molecular structure can directly be assembled into metal-organic nanopharmaceuticals by coordinative interaction with metal ions. Such coordination polymers generally feature extraordinarily high loading capacities and the flexibility to encapsulate different agents for a simultaneous delivery in combination therapy or 'theranostic' applications.

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.

Optimizing Energy Transfer in Nanostructures Enables In Vivo Cancer Lesion Tracking via Near-Infrared Excited Hypoxia Imaging

To explore highly sensitive and low-toxicity techniques for tracking and evaluation of non-small-cell lung cancer (NSCLC), one of the most mortal tumors in the world, it is utterly imperative for doctors to select the appropriate treatment strategies. Herein, developing near-infrared (NIR) excited nanosensors, in which the donor and acceptor pairs within a biological metal-organic framework (bio-MOF) matrix are precisely controlled to rationalize upconversion Förster resonance energy transfer (FRET), is suggested for detecting the O₂ concentration inside tumors with reduced signal disturbance and health detriment. Under NIR excitation, as-fabricated core/satellite nanosensors exhibit much improved FRET efficiency and reversible hypoxic response with high sensitivity, which are effective both in vitro and in vivo (zebrafish) for cycling normoxia-hypoxia imaging. Significantly, combined with a reliable preclinical genetically engineered murine model, such nanosensors successfully realize tracking of in vivo NSCLC lesions upon clear and gradient hypoxia signals without apparent long-term biotoxicity, illustrating their exciting potential for efficient NSCLC evaluation and prognosis.

A Nanostrategy for Efficient Imaging-Guided Antitumor Therapy through a Stimuli-Responsive Branched Polymeric Prodrug

A stimuli-responsive polymeric prodrug-based nanotheranostic system with imaging agents (cyanine5.5 and gadolinium-chelates) and a therapeutic agent paclitaxel (PTX) is prepared via polymerization and conjugating chemistry. The branched polymeric PTX-Gd-based nanoparticles (BP-PTX-Gd NPs) demonstrate excellent biocompatibility, and high stability under physiological conditions, but they stimuli-responsively degrade and release PTX rapidly in a tumor microenvironment. The in vitro behavior of NPs labeled with fluorescent dyes is effectively monitored, and the NPs display high cytotoxicity to 4T1 cells similar to free PTX by impairing the function of microtubules, downregulating anti-apoptotic protein Bcl-2, and upregulating the expression of Bax, cleaved caspase-3, cleaved caspase-9, cleaved-PARP, and p53 proteins. Great improvement in magnetic resonance imaging (MRI) is demonstrated by these NPs, and MRI accurately maps the temporal change profile of the tumor volume after injection of NPs and the tumor treatment process is also closely correlated with the T 1 values measured from MRI, demonstrating the capability of providing real-time feedback to the chemotherapeutic treatment effectiveness. The imaging-guided chemotherapy to the 4T1 tumor in the mice model achieves an excellent anti-tumor effect. This stimuli-responsive polymeric nano-agent opens a new door for efficient breast cancer treatment under the guidance of fluorescence/MRI.

Metal-Organic Frameworks for Photodynamic Therapy: Emerging Synergistic Cancer Therapy

Photodynamic therapy (PDT) conducted by photosensitizers producing cytotoxic reactive oxygen species (ROS) under light irradiation is widely used in cancer treatment. A great number of photoactive nanoscale metal-organic frameworks (NMOFs) have been prepared for PDT. With the development of biomedicine and nanotechnology, many synergistic cancer therapies have emerged. In this mini-review, an overview on the latest progress in the application of NMOFs in PDT is provided, with emphasis on the recent emergence of some synergistic therapies.

DFT-Assisted Spectroscopic Studies on the Coordination of Small Ligands to Palladium: From Isolated Ions to Nanoparticles

A combination of experimental spectroscopies (UV-vis and Fourier-transform infrared) and computational modeling was used to investigate the coordination of small ligands (aminopropanol and propanediol) to Pd species during the metal nanoparticle formation process. Differences emerged between O- (propanediol) and N-containing (aminopropanol) ligands. In particular, a strong interaction between the NH amino group and Pd²⁺ ions could be inferred on the basis of spectroscopic evidences, which was corroborated by theoretical simulations, which confirmed the preferential coordination of aminopropanol through the NH group. This interaction seems to potentially cause the aminopropanol ligand to control the particle shape through a selective blocking of Pd(100) facets, which promote the growth on the Pd(111) facets.

A zipped-up tunable metal coordinated cationic polymer for nanomedicine

Incorporating metal elements into polymers is a feasible means to fabricate new materials with multiple functionalities. In this work, a metal coordinated cationic polymer (MCCP) was developed. Ferric ions were incorporated into the polyethyleneimine-β-cyclodextrin (PC) polymer chain via coordination to produce a zipped-up polymer with a micro-ordered and macro-disordered topological structure. By varying the metal concentration, a tunable superstructure could be formed on the nano-templates via the "zipping" effect. In addition, the physicochemical properties of the assembly of MCCPs and nucleic acids were tailored by tuning the composition of the metal ions and polymers. The loading efficiency of Rhodamine-B by MCCPs was enhanced. The in vitro and in vivo results showed that the hybrid materials could be adjusted to deliver nucleic acids or small molecules with good performance and acquired the capacity of generating reactive oxygen species in tumor cells. Thus, the tunable and multifunctional MCCP system has great potential in nanomedicine and biomaterial science.

Metal-Organic Framework Nanoparticles for Ameliorating Breast Cancer-Associated Osteolysis

Breast cancer metastases to bone poses a significant challenge for the administration of treatment strategies. The bone microenvironment, metastatic tumor cells, osteoclasts, and tumor-associated macrophages (TAMs) all play crucial and synergistic roles in creating a favorable environment for the proliferation, progression, and survival of the metastatic tumor, which in turn induces osteoclast-mediated bone destruction. In this study, we functionalized immunostimulatory cytosine-phosphate-guanosine (CpG)-loaded metal-organic framework (MOF) nanoparticles with bone targeting capabilities by surface modification with FDA approved antiresorptive bisphosphonate, zoledronic acid (ZOL). The functionalized bone targeting immunostimulatory MOF (BT-isMOF) nanoparticles demonstrates strong binding to calcium phosphate in vitro and exhibits specific targeting and accumulation in bone tissues in vivo. In vitro cellular and biochemical analyses demonstrated that the BT-isMOF nanoparticles could potently inhibit osteoclast formation and concomitantly induce macrophages polarization toward the M1 pro-inflammatory phenotype. Finally, using the intratibial murine model of breast cancer bone metastasis, we showed that the administration of BT-isMOF nanoparticles significantly suppressed osteoclast-mediated bone destruction and enhanced polarization of tumor-resident macrophages to M1 phenotype. Together, our data provides promising evidence for the potential therapeutic application of the BT-isMOF nanoparticles in the treatment of breast cancer bone metastases.

Development of a nanodrug-delivery system camouflaged by erythrocyte membranes for the chemo/phototherapy of cancer

Aim: Development of a new drug-delivery system using a compound derived from Pronephrium penangianum (J5) for the treatment of cervical cancer. Materials & methods: The delivery system was developed using Prussian blue nanoparticles, camouflaged by red blood cell membrane and with folic acid surface modifications. Results: Our results showed the successful development of a nanodrug-delivery system, which increases the half-life and immune evasion ability of the drug. The mechanism of this system was through suppressing B-cell lymphoma 2 and increasing B-cell lymphoma 2-associated X protein and the cleaved caspase level. An in vivo study also confirmed good antitumor activity without any side effects to normal tissue. Conclusion: This drug-delivery system provides a good alternative for the treatment of cervical cancer using J5.

Hierarchically Structured Two-Dimensional Bimetallic CoNi-Hexaaminobenzene Coordination Polymers Derived from Co(OH)2 for Enhanced Oxygen Evolution Catalysis

Conjugated coordination polymers (CPs) with designable and predictable structures have drawn tremendous attention in recent years. However, the poor electrical conductivity and low structural stability seriously restrict their practical applications in electronic devices. Herein, the rational design and synthesis of a hierarchically structured 2D bimetallic CoNi-hexaaminobenzene CPs derived from Co(OH)₂ are reported as an efficient oxygen evolution reaction (OER) self-supported electrode. The as-obtained electrode possesses high electrochemical surface area and intrinsic activity, exhibiting high electrochemical catalytic activity, favorable reaction kinetics performance, and strong durability compared with those of the powder catalysts. As a result, the electrode delivers low overpotential of 219 mV @ 10 mA cm^-2 and Tafel slope of 42 mV dec^-1 as well as 91.3% retention of current density after 24 h of reaction time. The results of density functional theory computations reveal that the synergistic effect of Co and Ni plays an important role in OER. This work not only presents a strategy to fabricate advanced self-supported electrodes with abundant and dense active sites, but also promotes the development of conjugated CPs for electrocatalysis.

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.

Titanium Incorporation into Zr-Porphyrinic Metal-Organic Frameworks with Enhanced Antibacterial Activity against Multidrug-Resistant Pathogens

This study uses metal-organic frameworks (MOFs) alone without any added antibacterial ingredients as the nonantibiotic agent for photodynamic therapy (PDT) of chronic wounds infected by multidrug-resistant (MDR) bacteria. Nanoparticles (NPs) of MOFs (PCN-224) are incorporated with titanium through a facile cation exchange strategy. The obtained bimetallic PCN-224(Zr/Ti) shows greatly enhanced photocatalytic performance for the generation of reactive oxygen species under visible light, which is responsible for the effective antibacterial activities. The PCN-224(Zr/Ti) NPs are loaded onto lactic-co-glycolic acid nanofibers to prepare a wound dressing, which shows high biocompatibility and minimal cytotoxicity. The wound dressing is efficient for PDT-based in vivo healing of the chronic wound infected by MDR bacteria. Most importantly, this work does not involve any additional antibacterial agents, which is facile, low cost, and in particular, greatly explores the potential of MOFs as a powerful nonantibiotic agent in PDT.

Tuning Internal Strain in Metal-Organic Frameworks via Vapor Phase Infiltration for CO2 Reduction

A gas-phase approach to form Zn coordination sites on metal-organic frameworks (MOFs) by vapor-phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution-phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO₂ to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200-300 mV. Using element-specific X-ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square-pyramidal geometry with four Zn-N bonds in the equatorial plane and one Zn-OH₂ bond in the axial plane. The fine-tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.

A magnetic nanoscale metal-organic framework (MNMOF) as a viable fluorescence quencher material for ssDNA and for the detection of mercury ions via a novel quenching-quenching mechanism

A novel fluorescent biosensor has been designed and synthesized comprising a magnetic nanoscale metal-organic framework (MNMOF) functionalized with fluorescein amidite (FAM)-labeled ssDNA. It exhibits good sensitivity and selectivity for Hg(ii) cations over other co-existing metal ions. MNMOF was fabricated by a one-pot synthetic method and it was successfully characterized with various techniques such as UV-visible spectroscopy, fluorescence spectroscopy, Fourier-transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The FAM-labeled ssDNA was adsorbed onto the surface of MNMOF through π-π stacking and electrostatic interactions, which resulted in the partial quenching of its fluorescence intensity (65%). Upon the subsequent addition of Hg(ii) ions, the fluorescence intensity was further quenched at 52%, due to the re-adsorption of dsDNA onto the surface of MNMOF. Thus, the FAM-labeled ssDNA showed a drastic decrease in fluorescence intensity with Hg(ii). This quenching-quenching mechanism led to a linear response in the fluorescence intensity to Hg(ii) concentration (R 2 = 0.934) with a low detection limit of 8 nM. The specific merits of MNMOF make it an ideal platform for mercury sensor applications.

Rational design of a high-efficiency, multivariate metal-organic framework phosphor for white LED bulbs

Developing rare-earth element (REE) free yellow phosphors that can be excited by 455 nm blue light will help to decrease the environmental impact of manufacturing energy efficient white light-emitting diodes (WLEDs), decrease their cost of production, and accelerate their adoption across the globe. Luminescent metal-organic frameworks (LMOFs) demonstrate strong potential for use as phosphor materials and have been investigated intensively in recent years. However, the majority are not suitable for the current WLED technology due to their lack of blue excitability. Therefore, designing highly efficient blue-excitable, yellow-emitting, REE free LMOFs is much needed. With an internal quantum yield of 76% at 455 nm excitation, LMOF-231 is the most efficient blue-excitable yellow-emitting LMOF phosphor reported to date. Spectroscopic studies suggest that this quantum yield could be further improved by narrowing the material's bandgap. Based on this information and guided by DFT calculations, we apply a ligand substitution strategy to produce a semi-fluorinated analogue of LMOF-231, LMOF-305. With an internal quantum yield of 88% (λ _em = 550 nm) under 455 nm excitation, this LMOF sets a new record for luminescent efficiency in yellow-emitting, blue-excitable, REE free LMOF phosphors. Temperature-dependent and polarized photoluminescence (PL) studies have provided insight on the mechanism of emission and origin of the significant PL enhancement.

Oxalato bridged coordination polymer of manganese(iii) involving unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts: antiproliferative evaluation and theoretical studies

Unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts have been theoretically investigated for a Mn(iii) coordination polymer considering cytotoxicity, apoptosis, ROS generation, molecular docking and pharmacophore features.

A Cu(i)–I coordination polymer fluorescent chemosensor with amino-rich sites for nitro aromatic compound (NAC) detection in water

The detection sensitivity increased as the sizes of [Cu₂I₂(MA)₂] decreased and the selectivity improved by introducing amino-rich ligands.

Nanosheet-assembled microflower-like coordination polymers by surfactant-assisted assembly with enhanced catalytic activity

Nanosheet-assembled microflower-like coordination polymers were successfully prepared by a surfactant-assisted approach and used as an efficient heterogeneous catalyst to execute the conversion reactions of nitromethylbenzenes into benzoic acids.

Luminescent metal–organic frameworks (LMOFs) as potential probes for the recognition of cationic water pollutants

This review aims to provide an overview regarding the development of luminescent metal–organic frameworks (LMOFs) based sensory materials for the detection of cationic inorganic and organic water pollutants.

Functionalization of MOF-5 with mono-substituents: effects on drug delivery behavior

Metal organic frameworks (MOFs) are widely used in drug carrier research due to their tunability. The properties of MOFs can be adjusted through incorporation of mono-substituents to obtain pharmaceutical carriers with excellent properties. In this study, different functional groups of –NH₂, –CH₃, –Br, –OH and –CH₂ Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH are connected to MOF-5 to analyse the effect of mono-substituent incorporation on drug delivery properties. The resulting MOFs have similar structures, except for Br–MOF. The pore size of this series of MOFs ranges from 1.04 nm to 1.10 nm. Using oridonin (ORI) as a model drug, introduction of the functional groups appears to have a significant effect on the drug delivery performance of the MOFs. The IRMOFs can be ranked according to drug-loading capacity: MOF-5 > HO–MOF-5 > H₃C–MOF-5 = Br–MOF-5 > H₂N–MOF-5 > CH₂CH–MOF-5. The ORI release from ORI @IRMOFs is explored at two different pH values: 7.4 and 5.5, and the ORI@IRMOFs are ranked according to the cumulative release percentage of ORI: ORI@MOF-5 > ORI@Br–MOF-5 > ORI@H₃C–MOF-5 > ORI@H₂N–MOF-5 > CH₂CH–MOF-5 > ORI@ HO–MOF-5. In particular, the release behaviour of ORI@MOFs is described through a new model. The different drug delivery performance of MOFs may be due to the complex interactions between MOFs and ORI. In addition, the introduction of single substituents does not change the biocompatibility of MOFs. MTT in vitro experiments prove that this series of MOFs has low cytotoxicity. This study shows that the incorporation of single substituents can effectively adjust the drug delivery behaviour of MOFs, which is conducive to realization of personalized drug delivery modes. The introduction of active groups can also facilitate post-synthesis modification to achieve coupling of targeting groups. MOFs incorporated with single substituents perform favorably in terms of use as biomedical drug delivery alternative carriers in effective drug payload and flexible drug release.

Metal organic frameworks (MOFs) are widely used in drug carrier research due to their tunability.

Luminescent metal–organic framework-based phosphor for the detection of toxic oxoanions in an aqueous medium

Compound 1 has been utilized for the luminescence based visible detection of chromate, permanganate and phosphate ions in aqueous medium.

An NIF-doped ZIF-8 hybrid membrane for continuous antimicrobial treatment

Sodium alginate (ALG) composites with ZIF-8 and niflumic acid (NIF) were prepared by a one-pot method at room temperature and characterized by FTIR, SEM and XRD studies. In the composite, ZIF-8 was used as a highly connected node in a supercrosslinked polymer network. In addition, the material exhibits good antibacterial activity against Staphylococcus aureus and Escherichia coli in vitro. Compared to the original ALG membrane and ZIF-8, the ZIF–NIF–ALG membrane has the following advantages: stronger antibacterial properties; slow release of Zn(ii); high drug loading; and longer sustained release time. This research introduces new concepts for the design and manufacture of various antimicrobial membranes and broadens the range of applications of MOFs.

A ZIF-8 hybrid film has shows continuous medical effects, with including antibacterial and anti-inflammatory effects.

Controlling the morphology of metal–organic frameworks and porous carbon materials: metal oxides as primary architecture-directing agents

We give a comprehensive overview of how the morphology control is an effective and versatile way to control the physicochemical properties of metal oxides that can be transferred to metal–organic frameworks and porous carbon materials.

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.

Thrombin Aptamer-Modified Metal-Organic Framework Nanoparticles: Functional Nanostructures for Sensing Thrombin and the Triggered Controlled Release of Anti-Blood Clotting Drugs

This paper features the synthesis of thrombin-responsive, nucleic acid-gated, UiO-68 metal-organic framework nanoparticles (NMOFs) loaded with the drug Apixaban or rhodamine 6G as a drug model. Apixaban acts as an inhibitor of blood clots formation. The loads in the NMOFs are locked by duplex nucleic acids that are composed of anchor nucleic acids linked to the NMOFs that are hybridized with the anti-thrombin aptamer. In the presence of thrombin, the duplex gating units are separated through the formation of thrombin-aptamer complexes. The unlocking of the NMOFs releases the drug (or the drug model). The release of the drug is controlled by the concentration of thrombin. The Apixaban-loaded NMOFs revealed improved inhibition, as compared to free Apixaban, toward blood clot formation. This is reflected by their longer time intervals for inducing clot formation and the decreased doses of the drug required to affect clots formation. The beneficial effects of the Apixaban-loaded NMOFs are attributed to the slow-release mechanism induced by the NMOFs carriers, where the inhibition of factor Xa in the blood clotting cycle retards the formation of thrombin, which slows down the release of the drug.

Lanthanide Metal-Organic Framework Nanoprobes for the In Vitro Detection of Cardiac Disease Markers

Acute myocardial infarction (AMI) is one of the leading causes of death around the world. An early and accurate diagnosis of AMI is critical to reduce the mortality rate. As an important cardiac biomarker, creatine kinase (CK) has been used in the clinical diagnosis of AMI. However, it still remains a great challenge to realize highly sensitive and selective CK detection in blood specimens. Herein, we have developed an ultrasensitive platform for the detection of CK activity based on time-resolved (TR) luminescent lanthanide metal-organic framework nanoprobes (Eu-QPTCA). Benefiting from the intense emission of lanthanide ions sensitized by the organic ligands and the eliminated short-lived autofluorescence by the TR technique, these nanoprobes enabled the homogeneous detection of CK activity with a limit of detection down to 1.0 U/L, which is about 1 order of magnitude improvement relative to that of the traditional methods. In addition, the Eu-QPTCA nanoprobes showed superior selectivity and reliability toward the practical detection of CK activity in human serum, indicating the great significance of our method in the early diagnosis of AMI. We envision that the proposed bioassay strategy can be extended to the detection of other phosphorylation enzymes, paving a way for promising applications in clinical diagnostics.

Engineering of Nanoscale Coordination Polymers with Biomolecules for Advanced Applications

Nanoscale coordination polymers (NCPs) have shown extraordinary advantages in various research areas due to their structural diversity and multifunctionality. Recently, integration of biomolecules with NCPs received extensive attention and the formed hybrid materials exhibit superior properties over the individual NCPs or biomolecules. In this review, the state-of-the-art of approaches to engineer NCPs with different types of guest biomolecules, such as amino acids, nucleic acids, enzymes and lipids are systematically introduced. Additionally, advanced applications of these biomolecule-NCP composites in the areas of sensing, catalysis, molecular imaging and therapy are thoroughly summarized. Finally, current challenges and prospects are also discussed.

Mn-Porphyrin-Based Metal-Organic Framework with High Longitudinal Relaxivity for Magnetic Resonance Imaging Guidance and Oxygen Self-Supplementing Photodynamic Therapy

A nanoplatform for magnetic resonance imaging guidance and oxygen self-supplementing photodynamic therapy (PDT) was constructed on the basis of a porous metal-organic framework (PCN-222(Mn)), which was built by simple Mn-porphyrin ligands and biocompatible Zr⁴⁺ ions. Because of the good dispersibility of Mn³⁺ in the open framework and the high water affinity of the channel, PCN-222(Mn) exhibits a high longitudinal relaxivity of ∼35.3 mM^-1 s^-1 (1.0 T). In addition, it shows good catalytic activity for the conversion of endogenous hydrogen peroxide into oxygen, thereby improving tumor hypoxia during photodynamic therapy. The intravenous injection of PCN-222(Mn) into tumor-bearing mice mode provided good T₁-weighted contrast of the tumor site and effectively inhibited tumor growth upon a single-laser irradiation. The findings provide insights for the development of multifunctional theranostic nanoplatforms based on simple components.

Recent advances in metallopolymer-based drug delivery systems

Metallopolymers (MPs) or metal-containing polymers have shown great potential as new drug delivery systems (DDSs) due to their unique properties, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the recent advances and challenges associated with using MPs as DDSs. Among the most widely used MPs for these purposes, metal complexes based on synthetic and natural polymers, coordination polymers, metal-organic frameworks, and metallodendrimers are distinguished. Particular attention is paid to the stimulus- and multistimuli-responsive metallopolymer-based DDSs. Of considerable interest is the use of MPs for combination therapy and multimodal systems. Finally, the problems and future prospects of using metallopolymer-based DDSs are outlined. The bibliography includes articles published over the past five years.

Ultrathin metal-organic layer-mediated radiotherapy-radiodynamic therapy enhances immunotherapy of metastatic cancers

Checkpoint blockade immunotherapy (CBI) is effective in promoting a systemic immune response against some metastatic tumors. The reliance on the pre-existing immune environment of the tumor, however, limits the efficacy of CBI on a broad spectrum of cancers. Herein, we report the design of a novel nanoscale metal-organic layer (nMOL), Hf-MOL, for effective treatment of local tumors by enabling radiotherapy-radiodynamic therapy (RT-RDT) with low-dose X-rays and, when in combination with an immune checkpoint inhibitor, regression of metastatic tumors by re-activating anti-tumor immunity and inhibiting myeloid-derived suppressor cells. Owing to the reduced dimensionality, nMOLs allow facile diffusion of reactive oxygen species and exhibit superior RT-RDT effects. The synergy of Hf-MOL-enabled RT-RDT immune activation and anti-programmed death ligand 1 (anti-PD-L1) CBI led to robust abscopal effects on a series of bilateral models of colon, head and neck, and breast cancers and significant anti-metastatic effects on an orthotopic model of breast cancer.