Development of an SBU-Based Mechanochemical Approach for Drug-Loaded MOFs

Unveiling the potential of HKUST-1: synthesis, activation, advantages and biomedical applications

Metal-organic frameworks (MOFs) have emerged as a unique class of nanostructured materials, resulting from the self-assembly of metal ions or clusters with organic ligands, offering a wide range of applications in fields such as drug delivery, gas catalysis, and electrochemical sensing. Among them, HKUST-1, a copper-based MOF, has gained substantial attention due to its remarkable three-dimensional porous structure. Comprising copper ions and benzene-1,3,5-tricarboxylic acid, HKUST-1 exhibits an extraordinary specific surface area and pronounced porosity, making it a promising candidate in biomedicine. Notably, the incorporation of copper ions endows HKUST-1 with noteworthy activities, including antitumor, antibacterial, and wound healing-promoting properties. In this comprehensive review, we delve into the various synthesis methods and activation pathways employed in the preparation of HKUST-1. We also explore the distinct advantages of HKUST-1 in terms of its structural properties and functionalities. Furthermore, we investigate the exciting and rapidly evolving biomedical applications of HKUST-1. From its role in tumor treatment to its antibacterial effects and its ability to promote wound healing, we showcase the multifaceted potential of HKUST-1 in addressing critical challenges in biomedicine.

Solvent-Free Loading of Vitamin A Palmitate into β-Cyclodextrin Metal-Organic Frameworks for Stability Enhancement

Cyclodextrin metal-organic frameworks (CD-MOFs) exhibit a high structural diversity, which contributes to their functional properties. In this study, we have successfully synthesized a novel type of β-cyclodextrin metal-organic framework (β-CD-POF(I)) that exhibits excellent drug adsorption capacity and enhances stability. Single-crystal X-ray diffraction analysis revealed that β-CD-POF(I) possessed the dicyclodextrin channel moieties and long-parallel tubular cavities. Compared with the reported β-CD-MOFs, the β-CD-POF(I) has a more promising drug encapsulation capability. Here, the stability of vitamin A palmitate (VAP) was effectively improved by the solvent-free method. Molecular modeling and other characterization techniques like synchrotron radiation Fourier transform infrared spectroscopy (SR-FTIR), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and nitrogen adsorption isotherm were applied to confirm that the VAP was successfully encapsulated into the channel formed by the dicyclodextrin pairs. Furthermore, the mechanism of stability enhancement for VAP was determined to be due to the constraint and separation effects of β-CD pairs on VAP. Therefore, β-CD-POF(I) is capable of trapping and stabilizing certain unstable drug molecules, offering benefits and application possibilities. One kind of cyclodextrin particle with characteristic shapes of dicyclodextrin channel moieties and parallel tubular cavities, which was synthesized by a facile process. Subsequently, the spatial structure and characteristics of the β-CD-POF(I) were primarily confirmed. The structure of β-CD-POF(I) was then compared to that of KOH-β-CD-MOF, and a better material for vitamin A palmitate (VAP) encapsulation was determined. VAP was successfully loaded into the particles by solvent-free method. The arrangement of spatial structure made cyclodextrin molecular cavity encapsulation in β-CD-POF(I) more stable for VAP capture than that of KOH-β-CD-MOF.

From a Well-Defined Organozinc Precursor to Diverse Luminescent Coordination Polymers Based on Zn(II)-Quinolinate Building Units Interconnected by Mixed Ligand Systems

Introduction of photoactive building blocks into mixed-ligand coordination polymers appears to be a promising way to produce new advanced luminescent materials. However, rational design and self-assembly of the multi-component supramolecular systems is challenging from both a conceptual and synthetic perspective. Here, we report exploratory studies that investigate the potential of [Zn(q)₂]₂[tBuZn(OH)]₂ complex (q = deprotonated 8-hydroxyquinoline) as an organozinc precursor as well as a mixed-ligand synthetic strategy for the preparation of new luminescent coordination polymers (CPs). As a result we present three new 2D mixed-ligand Zn(II)-quinolinate coordination polymers which are based on various zinc quinolinate secondary building units interconnected by two different organic linker types, i.e., deprotonated 4,4'-oxybisbenzoic acid (H₂obc) as a flexible dicarboxylate linker and/or selected bipyridines (bipy). Remarkably, using the title organozinc precursors in a combination with H₂obc and 4,4'-bipyridine, a novel molecular zinc quinolinate building unit, [Zn₄(q)₆(bipy)₂(obc)₂], was obtained which self-assembled into a chain-type hydrogen-bonded network. The application of the organometallic precursor allowed for its direct reaction with the selected ligands at ambient temperature, avoiding the use of both solvothermal conditions and additional base reagents. In turn, the reaction involving Zn(NO₃)₂, as a classical inorganic precursor, in a combination with H₂obc and bipy led to a novel 1D coordination polymer [Zn₂(q)₂(NO₃)₂(bipy)]. While the presence of H₂obc was essential for the formation of this coordination polymer, this ditopic linker was not incorporated into the isolated product, which indicates its templating behavior. The reported compounds were characterized by single-crystal and powder X-ray diffraction, elemental analysis as well as UV-Vis and photoluminescence spectroscopy.

Metal-organic frameworks (MOFs) as host materials for the enhanced delivery of biomacromolecular therapeutics

Biomacromolecular drugs have become an important class of therapeutic agents for the treatment of human diseases. Considering their high propensity for being degraded in the human body, the choice of an appropriate delivery system is key to ensure the therapeutic efficacy of biomacromolecular drugs in vivo. As an emerging class of supramolecular "host" materials, metal-organic frameworks (MOFs) exhibit advantages in terms of the tunability of pore size, encapsulation efficiency, controllable drug release, simplicity in surface functionalization and good biocompatibility. As a result, MOF-based host-guest systems have been extensively developed as a new class of flexible and powerful platform for the delivery of therapeutic biomacromolecules. In this review, we summarize current research progress in the synthesis of MOFs as delivery materials for a variety of biomacromolecules. Firstly, we briefly introduce the advances made in the use of biomacromolecular drugs for disease therapy and the types of commonly used clinical delivery systems. We then describe the advantages of using MOFs as delivery materials. Secondly, the strategies for the construction of MOF-encapsulated biomacromolecules (Biomacromolecules@MOFs) and the release mechanisms of the therapeutics are categorized. Thirdly, the application of MOFs to deliver different types of biomacromolecules (e.g., antigens/antibodies, enzymes, therapeutic proteins, DNA/RNA, polypeptides, and polysaccharides) for the treatment of various human diseases based on immunotherapy, gene therapy, starvation therapy and oxidation therapy is summarized. Finally, the remaining challenges and available opportunities for MOFs as drug delivery systems are outlined, which we anticipate will encourage additional research efforts directed towards developing Biomacromolecules@MOFs systems for biomedical applications.

Effect of the proximal secondary sphere on the self-assembly of tetrahedral zinc-oxo clusters

Metal-oxo clusters can serve as directional and rigid building units of coordination and noncovalent supramolecular assemblies. Therefore, an in-depth understanding of their multi-faceted chemistry is vital for the development of self-assembled solid-state structures of desired properties. Here we present a comprehensive comparative structural analysis of isostructural benzoate, benzamidate, and new benzamidinate zinc-oxo clusters incorporating the [O,O]-, [O,NH]- and [NH,NH]-anchoring donor centers, respectively. We demonstrated that the NH groups in the proximal secondary coordination sphere are prone to the formation of intermolecular hydrogen bonds, which affects the packing of clusters in the crystal structure. Coordination sphere engineering can lead to the rational design of new catalytic sites and novel molecular building units of supramolecular assemblies.

Recent advances in Cu(II)/Cu(I)-MOFs based nano-platforms for developing new nano-medicines

With increasing world population, life-span of humans and spread of viruses, myriad of diseases in human beings are becoming more and more common. Because of the interesting chemical and framework versatility and porosity of metal organic frameworks (MOFs) they find application in varied areas viz. catalysis, sensing, metal ion/gas storage, chemical separation, drug delivery, bio-imaging. This subclass of coordination polymers having interesting three-dimensional framework exhibits inordinate potential and hence may find application in treatment and cure of cancer, diabetes Alzheimer's and other diseases. The presented review focuses on the diverse mechanism of action, unique biological activity and advantages of copper-based metal organic framework (MOF) nanomaterials in medicine. Also, different methods used in the treatment of cancer and other diseases have been presented and the applications as well as efficacy of copper MOFs have been reviewed and discussed. Eventually, the current-status and potential of copper based MOFs in the field of anti-inflammatory, anti-bacterial and anti-cancer therapy as well as further investigations going on for this class of MOF-based multifunctional nanostructures in for developing new nano-medicines have been presented.

Mechanochemical approaches towards the in situ confinement of 5-FU anti-cancer drug within MIL-100 (Fe) metal–organic framework

Low-cost mechanochemistry methods for in situ confinement of “guest” drug molecules into a “host” metal–organic framework to yield nanoscale guest@host drug delivery systems.

Mechanochemistry: an efficient and versatile toolbox for synthesis, transformation, and functionalization of porous metal–organic frameworks

Multiple ways in which the synergy of mechanochemistry and MOFs advances the field of materials chemistry are presented here.