Interfacial galvanic replacement strategy for Pd-doped NiFe MOF nanosheets with highly efficient dopamine detection.

An interfacial galvanic replacement strategy to controllable synthesize palladium nanoparticles (Pd NPs)-modified NiFe MOF nanocomposite on nickel foam, which served as an efficient sensing platform for quantitative determination of dopamine (DA). Pd NPs grown in situ on the nanosheets of NiFe MOF via self-driven galvanic replacement reaction (GRR) and well uniform distribution was achieved. This method effectively reduced the aggregation of metallic nanoparticles and significantly promoted the electron transfer rate during the electrochemical process, leading to improved electrocatalytic activity for DA oxidation. Remarkably, the precisely constructed biosensor achieved a low detection limit (LOD) of 0.068 µM and recovery of 94.1% (RSD 6.7%, N = 3) for simulated real sample detection and also exhibited superior selectivity and stability. The results confirmed that the as-fabricated Pd-NiFe/NF composite electrode could realize the quantitative determination of DA and showed promising prospects in real sample biosensing.

Synthesis and performance of a nanosensing platform for homocysteine detection: A series of iridium(III) complexes containing aldehyde group as probe and MOF as supporting substrate.

The low cost and simple detection method for Hcy (homocysteine) is highly desired in analytical and biological fields since Hcy has been regarded as a bio-marker for multiple diseases. In this work, five Ir(C^N)2(N^N)+ compounds having -CHO group in their C^N or N^N ligand were synthesized and tried for Hcy sensing. Electron-donating groups such as -NH2 and -CH3 were incorporated into the C^N or N^N ligand. Their geometric structure, electronic structure, and optical parameters (with or without Hcy) were analyzed and compared carefully to explore their Hcy sensing potential. The sensing mechanism was revealed by NMR titration and theoretical simulation as a cyclization reaction between the -CHO group and Hcy. The optimal compounds, which showed increased emission quantum yield (2.5-fold) and emission blue-shift (by âˆ¼ 100 nm) upon Hcy, were then covalently grafted into a porous host bio-MOF-1. Linear working plots were fitted, with good selectivity, LOD of 0.15 µM, and response time of 33 s. The novelty of this work was the eye-sensitive emission color change of this nanosensing platform from red (without Hcy) to green (with Hcy).

Lipase in-situ immobilized in covalent organic framework: Enzymatic properties and application in the preparation of 1, 3-dioleoyl-2-palmitoylglycerol.

In this study, the critical importance of designing an appropriate immobilized carrier and method for free lipase to ensure exceptional biological catalytic activity and stability was emphasized. Covalent organic frameworks (COF-1) were synthesized as a novel porous carrier with an azine structure (-CN-NC-) through the condensation of hydrazine hydrate and benzene-1,3,5-tricarbaldehyde at room temperature. Simultaneously, Rhizomucor miehei lipase (RML) was immobilized within the COF-1 carrier using an in-situ aqueous phase method. Characterization of the carrier and RML@COF-1 and evaluation of the lipase properties of RML and RML@COF-1 through p-Nitrophenyl palmitate hydrolysis were conducted. Additionally, application in the synthesis of 1, 3-dioleoyl-2-palmitoylglycerol (OPO) was explored. The results showed that RML@COF-1 exhibited a high enzymatic loading of 285.4 mg/g. Under 60℃ conditions, the activity of RML@COF-1 was 2.31 times higher than that of free RML, and RML@COF-1 retained 77.25% of its original activity after 10 cycles of repeated use, indicating its excellent thermal stability and repeatability. Under the optimal conditions (10%, 1:8 PPP/OA, 45℃, 5 h), the yield of OPO reached 47.35%, showcasing the promising application prospects of the novel immobilized enzyme synthesized via in-situ aqueous phase synthesis for OPO preparation.

Constructing Highly Emissive Covalent Organic Frameworks for Fe3+ Ion Detection via Wall Function.

Covalent organic frameworks (COFs) represent a new type of crystalline porous polymers that possess pre-designed skeletons, uniform nanopores, and ordered π structure. These attributes make them well-suited for the design of light-emitting materials. However, the majority of COFs exhibits poor luminescence due to aggregation-caused quenching (ACQ), resulting from the strong interaction between adjacent layers. To break the limitation, the building units with three methoxy groups on the walls are used to construct TM-OMe-EBTHz-COF, which suppresses the ACQ effects to improve light-emitting activity of COF. The TM-OMe-EBTHz-COF exhibits a notable emission of yellow-green luminescence in the solid state, with a remarkably high absolute quantum yield of 21.1%. The methoxy groups and hydrazine linkage form three coordination sites, contributing to excellent performance in metal ions sensing. The TM-OMe-EBTHz-COF demonstrates high sensitivity and selectivity to Fe3+ ion. Importantly, the low detection limit is below 150 nanomolar, ranking it among the best-performing Fe3+ sensor systems.

Triangular Heteroporous Covalent Organic Framework via a K-Shaped "Two-in-One" Monomer: Targeted Synthesis and Selective Removal of Organic Pollutants.

Covalent organic frameworks (COFs) have attracted increasing research interest due to their intriguing topological structures and fascinating properties. Diverse COFs with different shapes and sizes are developed by the design of appropriate building blocks. However, the heteroporous COFs to date are still in their infancy due to the relatively limited configuration of precursors. Herein, it is ingeniously designed and synthesized a new K-shaped "two-in-one" building unit (3',6'-bis(4-(5,5-dimethyl-1,3-dixoan-2-yl)phenyl)-[1,1':2',1"-terphenyl]-4,4"-diamine, BPTD), thus realizing the construction of triangular dual microporous COF (BPTD-COF) via self-polycondensation of the K-shaped monomer. The super micropore (0.76 nm) of BPTD-COF endows the higher density of amine activity sites, while the other aperture size (1.35 nm) meets the need for accommodating cationic dyes (rhodamine B, methylene blue), thus BPTD-COF displays a distinctive selective adsorption for cationic dyes with good reusability.

Synthesis of dual-stimuli responsive metal organic framework-coated iridium oxide nanocomposite functionalized with tumor targeting albumin-folate for synergistic photodynamic/photothermal cancer therapy.

The synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT) has attracted considerable attention in the field of cancer therapy because of its excellent anti-tumor effect. This work provides a novel pH/NIR responsive therapeutic nanoplatform, IrO2@ZIF-8/BSA-FA (Ce6), producing a synergistic effect of PTT-PDT in the treatment of osteosarcoma. Iridium dioxide nanoparticles (IrO2 NPs) with exceptional catalase-like activity and PTT effects were synthesized by a hydrolysis method and decorated with zeolitic imidazolate framework-8 (ZIF-8) shell layer to promote the physical absorption of Chlorin e6 (Ce6), and further functionalized with bovine serum albumin-folate acid (BSA-FA) for targeting tumor cells. The IrO2@ZIF-8/BSA-FA nanocomposite indicated an outstanding photothermal heating conversion efficiency of 62.1% upon laser irradiation. In addition, the Ce6 loading endows nanoplatform with the capability to induce cell apoptosis under 660 nm near-infrared (NIR) laser irradiation through a reactive oxygen species (ROS)-mediated mechanism. It was further testified that IrO2@ZIF-8/BSA-FA can function as a catalase and convert the endogenous hydrogen peroxide (H2O2) into oxygen (O2) to improve the local oxygen pressure under the acidic tumor microenvironment (TME), which could subsequently amplified PDT-mediated ROS cell-killing performance via relieving hypoxia microenvironment of tumor. Both in vitro and in vivo experimental results indicated that the nanomaterials were good biocompatibility, and could remarkably achieve tumor-specific and enhanced combination therapy outcomes as compared with the corresponding PTT or PDT monotherapy. Taken together, this work holds great potential to design an intelligent multifunctional therapeutic nanoplatform for cancer therapy.

Supramolecular Reinforcement of a Large-Pore 2D Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D-COFs) are a class of crystalline porous organic polymers that consist of covalently linked, two-dimensional sheets that can stack together through noncovalent interactions. Here we report the synthesis of a novel COF, called PyCOFamide, which has an experimentally observed pore size that is greater than 6 nm in diameter. This is among the largest pore size reported to date for a 2D-COF. PyCOFamide exhibits permanent porosity and high crystallinity as evidenced by the nitrogen adsorption, powder X-ray diffraction, and high-resolution transmission electron microscopy. We show that the pore size of PyCOFamide is large enough to accommodate fluorescent proteins such as Superfolder green fluorescent protein and mNeonGreen. This work demonstrates the utility of noncovalent structural reinforcement in 2D-COFs to produce larger and persistent pore sizes than previously possible.

A CuS- and BODIPY-loaded nanoscale covalent organic framework for synergetic photodynamic and photothermal therapy.

Herein, we report an inorganic photothermal agent, CuS- and an organic photosensitizer, BODIPY-loaded composite nanoscale COF material via a stepwise post-synthetic modification. The obtained CuS@COF-BDP can be a dual-modal therapeutic agent to highly inhibit MCF-7 tumor cell proliferation due to its efficient singlet oxygen generation and photothermal conversion abilities.

Bimetallic metal-organic frameworks for tumor inhibition via combined photothermal-immunotherapy.

Herein, we report the design of therapeutic nanoparticles by encapsulating photosensitizers and aluminum ions into metal-organic frameworks. The nanoparticles could significantly inhibit the growth of primary and rechallenged tumors by a combination of photothermal therapy and immunotherapy. This work offers a promising strategy to design an immunologic nanoplatform for "cold" tumor therapy.

Application of polysaccharide-based metal organic framework membranes in separation science.

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.

Artificial Biomolecular Channels: Enantioselective Transmembrane Transport of Amino Acids Mediated by Homochiral Zirconium Metal-Organic Cages.

Natural transport channels (or carriers), such as aquaporins, are a distinct type of biomacromolecule capable of highly effective transmembrane transport of water or ions. Such behavior is routine for biology but has proved difficult to achieve in synthetic systems. Perhaps most significantly, the enantioselective transmembrane transport of biomolecules is an especially challenging problem both for chemists and for natural systems. Herein, a group of homochiral zirconium metal-organic cages with four triangular opening windows have been proposed as artificial biomolecular channels for enantioselective transmembrane transport of natural amino acids. These structurally well-defined coordination cages are assembled from six synthetically accessible BINOL-derived chiral ligands as spacers and four n-Bu3-Cp3Zr3 clusters as vertices, forming tetrahedral-shaped architectures that feature an intrinsically chiral cavity decorated with an array of specifically positioned binding sites mediated from phenol to phenyl ether to crown ether groups. Fascinatingly, the transformation of single-molecule chirality to global supramolecular chirality within the space-restricted chiral microenvironments accompanies unprecedented chiral amplification, leading to the enantiospecific recognition of amino acids. By virtue of the highly structural stability and excellent biocompatibility, the orientation-independent cages can be molecularly embedded into lipid membranes, biomimetically serving as single-molecular chiral channels for polar-residue amino acids, with the properties that cage-1 featuring hydroxyl groups preferentially transports the l-asparagine, whereas cage-2 attaching crown ether groups spontaneously favor transporting d-arginine. We therefore develop a new type of self-assembled system that can potentially mimic the functions of transmembrane proteins in nature, which is a realistic candidate for further biomedical applications.

Near-Infrared Emissive Lanthanide Metal-Organic Frameworks for Targeted Biological Imaging and pH-Controlled Chemotherapy.

Near-infrared window II (NIR-II, 1000-1700 nm) imaging displays the advantages in deep-tissue high-contrast imaging in vivo on the strength of the high temporal-spatial resolution and deeper penetration. However, the clinical utility of NIR-II imaging agents is limited by their single function. Herein, for the first time, we report the design of a multifunctional drug delivery system (DDS) assembly, CQ/Nd-MOF@HA nanohybrids, with NIR-II fluorescence (1067 nm), large Stokes shifts, and ultrahigh quantum yield, which combined targeted NIR-II luminescence bioimaging and pH-controlled drug delivery. The nanoscale metal-organic framework (MOF) as a highly promising multifunctional DDS for targeted NIR-II bioimaging and chemotherapy in vitro and in vivo lays the foundation of the MOF-based DDS for further clinical diagnosis and treatment.

Enhanced Antimicrobial Activity and Low Phytotoxicity of Acoustically Synthesized Large Aspect Ratio Cu-BTC Metal-Organic Frameworks with Exposed Metal Sites.

Metal-organic frameworks (MOFs) have recently been shown to be effective antimicrobial agents, particularly if they comprise pathogenicidal metal ions. Nevertheless, the accessibility of these active metal sites to the pathogen, and hence the MOFs' antimicrobial activity itself, is often poor since the metal nodes are usually embedded deep within its three-dimensional (3D) structure. We show that a unique copper-based (copper(II)-benzene-1,3,5-tricarboxylate) MOF, whose quasi-two-dimensional (quasi-2D) swordlike structure facilitates exposure of the metal ions along its surface, exhibits enhanced antimicrobial properties against three representative plant pathogens: a bacterium (Pseudomonas syringae), a fungus (Fusarium solani), and a virus (Odontoglossum ringspot virus (ORSV)). Such superior antimicrobial activity results in low minimum inhibitory concentrations (MICs)─half that of a commercial pesticide and an eighth of its conventional 3D cubic MOF counterpart (HKUST-1)─and hence low phytotoxicity, which can be attributed to the accessibility of the surface copper sites to the pathogen, thereby facilitating their adhesion and physical contact with the MOF. Additionally, we observed that orchids treated with the quasi-2D MOF showed negligible phytotoxicity and 80% decreased viral load. This work constitutes the first study to demonstrate the antimicrobial properties of this novel MOF against bacterial, fungal, and viral plant pathogens, and the first chemical control of ORSV.

Facile Synthesis of a Cubic Porphyrin-Based Covalent Organic Framework for Combined Breast Cancer Therapy.

A cubic porphyrin-based covalent organic framework (COF) named CTP with excellent hydrophilicity was prepared with a facile method for the first time. Different from the conventional methods for the synthesis of porphyrin-based COFs, this facile strategy has greatly shortened the reaction time under mild conditions. Linking the porphyrin monomer into the COF overcame its poor solubility and biocompatibility and also narrowed the band gap owing to the formation of the π-conjugation structure. The improved biocompatibility and narrowed band gap enabled CTP to be an excellent sonosensitizer with an enhanced sonodynamic effect. Moreover, CTP could also effectively realize photothermal conversion under external irradiation due to the extended conjugated structure. This work developed a novel synthesis method for COFs and employed a COF as a sonosensitizer for the first time, which not only provided a new strategy to improve the efficiency of organic sonosensitizers but also inspired us to design more functional COFs for versatile applications.

Silencing of Pyruvate Kinase M2 via a Metal-Organic Framework Based Theranostic Gene Nanomedicine for Triple-Negative Breast Cancer Therapy.

Triple-negative breast cancer (TNBC) is typically associated with poor prognosis due to its only partial response to chemotherapy and lack of clinically established targeted therapies coupled with an aggressive disease course. Aerobic glycolysis is a hallmark of reprogrammed metabolic activity in cancer cells, which can be repressed by small-interfering RNA (siRNA). However, the lack of effective carriers to deliver vulnerable siRNA restricts the clinical potentials of glycolysis-based gene therapy for TNBC. Herein, we develop a tumor-targeted, biomimetic manganese dioxide (MnO2)-shrouded metal-organic framework (MOF) based nanomedicine to deliver siRNA against pyruvate kinase muscle isozyme M2 (siPKM2), wherein PKM2 is a rate-limiting enzyme in glycolysis, to inhibit the reprogrammed glycolysis of TNBC. This MOF-based genetic nanomedicine shows excellent monodispersity and stability and protects siPKM2 against degradation by nucleases. The nanomedicine not only substantially blocks the glycolytic pathway but also improves intracellular hypoxia in TNBC cells, with a resultant O2-enhanced anticancer effect. In the mice orthotopic TNBC model, the nanomedicine shows a remarkable therapeutic effect. Meanwhile, the Mn2+ ions released from acid microenvironment-responsive MnO2 enable in vivo monitoring of the therapeutic process with magnetic resonance imaging (MRI). Our study shows great promise with this MRI-visible MOF-based nanomedicine for treating TNBC by inhibition of glycolysis via the RNA interference.

Tunable and Controlled Release of Cobalt Ions from Metal-Organic Framework Hydrogel Nanocomposites Enhances Bone Regeneration.

Cobalt (Co) ions, which can mimic hypoxia to promote angiogenesis, exhibit great potential for bone repair. However, a key point for the use of Co ions is that their release profile should be controllable and, more importantly, suitable for the bone regeneration process. Here, 2-ethylimidazole (eIm) was introduced into zeolitic imidazolate framework-67 (ZIF-67) to slow down Co-ion release and fabricate eIm-doped ZIF-67 (eIm/ZIF-67), which was combined into gelatin methacrylate (GelMA) to obtain an in situ photo-cross-linking nanocomposite hydrogel as a tunable Co-ion controlled release system. A tunable and controlled release of Co ions from the nanocomposite hydrogel was achieved by variation of linker composition, and GelMA with 75% eIm/ZIF-67 (with 75% eIm in the precursor solutions) could maintain a 21-day sustained release of Co ions, which is matched with early-stage angiogenesis during the bone formation process. Our in vitro study also showed that the GelMA@eIm/ZIF-67 hydrogel could reduce cytotoxicity and effectively promote the angiogenic activity of human umbilical vein endothelial cells (HUVECs) and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Moreover, an in vivo rat calvarial defect model demonstrated that the GelMA@eIm/ZIF-67 hydrogel exhibited remarkably enhanced bone formation and neovascularization abilities and had good biocompatibility as shown in organ histopathological examinations. Therefore, this novel nanocomposite hydrogel has strong therapeutic potential as a desirable Co-ion controlled release system and a powerful proangiogenic/osteogenic agent for the treatment of bone defects.

Heparin-Coated Photosensitive Metal-Organic Frameworks as Drug Delivery Nanoplatforms of Autophagy Inhibitors for Sensitized Photodynamic Therapy against Breast Cancer.

Photosensitive nanosized metal-organic frameworks (nanoMOFs) with a tunable structure and high porosity have been developed recently as nanophotosensitizers (nanoPSs) for photodynamic therapy (PDT). However, the effect of photodynamic therapy is greatly limited by the fast blood clearance and poor tumor retention of the ordinary nanoPSs. Besides, autophagy, a prosurvival self-cannibalization pathway mediated by autolysosomes, was elevated by cytotoxic reactive oxygen species (ROS) produced during PDT. Herein, a chloroquine phosphate (CQ)-loaded photosensitive nanoMOF coated by heparin was fabricated for sensitized PDT by increasing the tumor accumulation of nanoPSs and abolishing the self-protective autophagy within cancer cells. After internalization by cancer cells, the encapsulated CQ alkalizes autolysosomes and blocks the postautophagy process, which disarm the vigilant cancer cells irritated by PDT and finally enhance the therapeutic effect. Furthermore, the accompanied antiangiogenesis ability of the heparin coat also helps improve the cancer therapy outcomes. This study would open up new horizons for building heparin-coated nanoMOFs and understanding the role of autophagy in cancer therapy.

Two mesoporous anionic metal-organic frameworks for selective and efficient adsorption of a cationic organic dye.

Anionic metal-organic frameworks (MOFs) are beginning to have a great impact in the field of absorption and separation of ionic organic molecules due to the enhanced electrostatic interactions between their anionic frameworks and counter-ionic guests. Herein, the rational design and synthesis of two mesoporous anionic MOFs, [Zn3(ITTC)3](Me2 NH2)3·3DMF·H2O (1) and [Cd2(ITTC)3](Me2NH2)5·2DMF (2), where H3ITTC = 4,4',4''-(1H-imidazole-2,4,5-triyl) tribenzoic acid, is reported. Structural analysis revealed that both materials are anionic MOFs with a 2-fold interpenetrating three dimensional (3D) framework. The cross sectional area of the open one-dimensional rectangular channels is 31.7 Å × 15.6 Å for 1, of which the architecture is indicative of an unprecedented (3,3,4,5)-connection topology. For 2, the diameter of the open one-dimensional regular hexagonal channel is about 34.1 Å, decorated with uncoordinated carboxyl O atoms, and the framework exhibits a (3,4)-connected fcu network. Due to their anionic frameworks and bulky pore window sizes, both MOFs can be employed for absorbing and separating the cationic organic dye methylene blue (MB). The results reveal that both MOFs have better dye adsorption selectivity for MB, than for MO and SDI, because of charge and size-matching effects, enabling them to be potential candidates for use in environmental cleaning. By comparison, 2 presents superior selectivity and adsorptivity for cationic MB which depends on the presence of a basic functionalized pore surface.

Postsynthetic Modification of the Magnetic Zirconium-Organic Framework for Efficient and Rapid Solid-Phase Extraction of DNA.

In recent years, several approaches have been applied to modify metal-organic frameworks (MOFs) owing to their excellent structural tunability such as higher extraction efficiency than that of primitive crystals. Herein, Zr-based MOFs (UiO-66-NH2) with a suitable size modulated by acetic acid were successfully synthesized for effective DNA extraction. The bonding conformations and adsorption mechanism indicated a high affinity between UiO-66-NH2 and the DNA molecules. Furthermore, Fe3O4 nanoparticles were immobilized on the UiO-66-NH2 surface to allow MOFs with magnetism. The magnetic zirconium-organic framework (MZMOF) retained the intact structure of MOFs and simplified subsequent extraction operations. In the DNA recovery investigation, MZMOF showed high recovery efficiency for both short-stranded DNA (90.4%) and pseudovirus DNA (95.1%). In addition, it showed superior DNA extraction efficiency from plasma (57.6%) and swab preservation solution (86.5%). The prepared MZMOF was employed for highly specific extraction of viral DNA and cfDNA from samples. To further simplify the extraction process, MZMOF was applied to immiscible phase filtration assisted by a surface tension (IFAST) chip for facilitating rapid DNA extraction with sensitive point-of-care testing. The developed MZMOF-based extraction method has significant potential for increasing the demand for rapid and efficient nucleic acid extraction.

Fabrication of Dexamethasone-Loaded Dual-Metal-Organic Frameworks on Polyetheretherketone Implants with Bacteriostasis and Angiogenesis Properties for Promoting Bone Regeneration.

Polyetheretherketone (PEEK) is a biocompatible polymer, but its clinical application is largely limited due to its inert surface. To solve this problem, a multifunctional PEEK implant is urgently fabricated. In this work, a dual-metal-organic framework (Zn-Mg-MOF74) coating is bonded to PEEK using a mussel-inspired polydopamine interlayer to prepare the coating, and then, dexamethasone (DEX) is loaded on the coating surface. The PEEK surface with the multifunctional coating provides superior hydrophilicity and favorable stability and forms an alkaline microenvironment when Mg2+, Zn2+, 2,5-dihydroxyterephthalic acid, and DEX are released due to the coating degradation. In vitro results showed that the multifunctional coating has strong antibacterial ability against both Escherichia coli and Staphylococcus aureus; it also improves human umbilical vein endothelial cell angiogenic ability and enhances rat bone marrow mesenchymal stem cell osteogenic differentiation activity. Furthermore, the in vivo rat subcutaneous infection model, chicken chorioallantoic membrane model, and rat femoral drilling model verify that the PEEK implant coated with the multifunctional coating has strong antibacterial and angiogenic ability and promotes the formation of new bone around the implant with a stronger bone-implant interface. Our findings indicate that DEX loaded on the Zn-Mg-MOF74 coating-modified PEEK implant with bacteriostasis, angiogenesis, and osteogenesis properties has great clinical application potential as bone graft materials.