Recent Advances in Metal-Organic Frameworks for Applications in Magnetic Resonance Imaging

Metal-organic frameworks for biomedical applications: A review

Metal-organic frameworks (MOFs) are emergent materials in diverse prospective biomedical uses, owing to their inherent features such as adjustable pore dimension and volume, well-defined active sites, high surface area, and hybrid structures. The multifunctionality and unique chemical and biological characteristics of MOFs allow them as ideal platforms for sensing numerous emergent biomolecules with real-time monitoring towards the point-of-care applications. This review objects to deliver key insights on the topical developments of MOFs for biomedical applications. The rational design, preparation of stable MOF architectures, chemical and biological properties, biocompatibility, enzyme-mimicking materials, fabrication of biosensor platforms, and the exploration in diagnostic and therapeutic systems are compiled. The state-of-the-art, major challenges, and the imminent perspectives to improve the progressions convoluted outside the proof-of-concept, especially for biosensor platforms, imaging, and photodynamic therapy in biomedical research are also described. The present review may excite the interdisciplinary studies at the juncture of MOFs and biomedicine.

Hyperpolarized 129Xe Atoms Sense the Presence of Drug Molecules in Nanohosts Revealed by Magnetic Resonance Imaging

Assessing the effectiveness of nanomedicines involves evaluating the drug content at the target site. Currently, most research focuses on monitoring the signal responses from loaded drugs, neglecting the changes caused by the nanohosts. Here, we propose a strategy to quantitatively evaluate the content of loaded drugs by detecting the signal variations resulting from the alterations in the microenvironment of the nanohosts. Specifically, hyperpolarized (HP) 129Xe atoms are employed as probes to sense the nanohosts' environment and generate a specific magnetic resonance (MR) signal that indicates their accessibility. The introduction of drugs reduces the available space in the nanohosts, leading to a crowded microenvironment that hinders the access of the 129Xe atoms. By employing 129Xe atoms as a signal source to detect the alterations in the microenvironment, we constructed a three-dimensional (3D) map that indicated the concentration of the nanohosts and established a linear relationship to quantitatively measure the drug content within the nanohosts based on the corresponding MR signals. Using the developed strategy, we successfully quantified the uptake of the nanohosts and drugs in living cells through HP 129Xe MR imaging. Overall, the proposed HP 129Xe atom-sensing approach can be used to monitor alterations in the microenvironment of nanohosts induced by loaded drugs and provides a new perspective for the quantitative evaluation of drug presence in various nanomedicines.

Metal-organic framework-based adsorbents for blood purification: progress, challenges, and prospects

Blood purification, such as hemodialysis (HD), plasma exchange (PE), and hemoperfusion (HP), is widely applied in patients with organ failure (such as kidney and liver failure). Among them, HP mainly relies on porous adsorbents to efficiently adsorb accumulated metabolic wastes and toxins, thus improving purification efficiency. Metal-organic frameworks (MOFs), with a high porosity, large surface area, high loading capacity, and tailorable topology, are emerging as some of the most promising materials for HP. Compared with non-metal framework counterparts, the self-built metal centers of MOFs feature the intrinsic advantages of coordination with toxin molecules. However, research on MOFs in blood purification is insufficient, particularly in contrast to materials applied in other biomedical applications. Thus, to broaden this area, this review first discusses the essential characteristics, potential mechanisms, and structure-function relationship between MOFs and toxin adsorption based on porosity, topology, ligand functionalization, metal centers, and toxin types. Moreover, the stability, utilization safety, and hemocompatibility of MOFs are illustrated for adsorbent selection. The current development and progress in MOF composites for HD, HP, and extracorporeal membrane oxygenation (ECMO) are also summarized to highlight their practicability. Finally, we propose future opportunities and challenges from materials design and manufacture to the computational prediction of MOFs in blood purification. It is anticipated that our review will expand the interest of researchers for more impact in this area.

Nanocomposites Based on Magnetic Nanoparticles and Metal-Organic Frameworks for Therapy, Diagnosis, and Theragnostics

In the last two decades, metal-organic frameworks (MOFs) with highly tunable structure and porosity, have emerged as drug nanocarriers in the biomedical field. In particular, nanoscaled MOFs (nanoMOFs) have been widely investigated because of their potential biocompatibility, high drug loadings, and progressive release. To enhance their properties, MOFs have been combined with magnetic nanoparticles (MNPs) to form magnetic nanocomposites (MNP@MOF) with additional functionalities. Due to the magnetic properties of the MNPs, their presence in the nanosystems enables potential combinatorial magnetic targeted therapy and diagnosis. In this Review, we analyze the four main synthetic strategies currently employed for the fabrication of MNP@MOF nanocomposites, namely, mixing, in situ formation of MNPs in presynthesized MOF, in situ formation of MOFs in the presence of MNPs, and layer-by-layer methods. Additionally, we discuss the current progress in bioapplications, focusing on drug delivery systems (DDSs), magnetic resonance imaging (MRI), magnetic hyperthermia (MHT), and theragnostic systems. Overall, we provide a comprehensive overview of the recent advances in the development and bioapplications of MNP@MOF nanocomposites, highlighting their potential for future biomedical applications with a critical analysis of the challenges and limitations of these nanocomposites in terms of their synthesis, characterization, biocompatibility, and applicability.

The Promise and Potential of Metal-Organic Frameworks and Covalent Organic Frameworks in Vaccine Nanotechnology

The immune system's complexity and ongoing evolutionary struggle against deleterious pathogens underscore the value of vaccination technologies, which have been bolstering human immunity for over two centuries. Despite noteworthy advancements over these 200 years, three areas remain recalcitrant to improvement owing to the environmental instability of the biomolecules used in vaccines─the challenges of formulating them into controlled release systems, their need for constant refrigeration to avoid loss of efficacy, and the requirement that they be delivered via needle owing to gastrointestinal incompatibility. Nanotechnology, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), has emerged as a promising avenue for confronting these challenges, presenting a new frontier in vaccine development. Although these materials have been widely explored in the context of drug delivery, imaging, and cancer immunotherapy, their role in immunology and vaccine-related applications is a recent yet rapidly developing field. This review seeks to elucidate the prospective use of MOFs and COFs for biomaterial stabilization, eliminating the necessity for cold chains, enhancing antigen potency as adjuvants, and potentializing needle-free delivery of vaccines. It provides an expansive and critical viewpoint on this rapidly evolving field of research and emphasizes the vital contribution of chemists in driving further advancements.

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.

Bimetallic Porphyrin-Based Metal-Organic Framework as a Superior Photocatalyst for Enhanced Photocatalytic Hydrogen Production

The meaningful and rational engineering of porphyrin-based catalysts with multimetallic active sites is very attractive toward photocatalytic hydrogen generation from water decomposition. Herein, three metal organic frameworks (MOFs) based on meso-tetrakis(4-carboxylphenyl)porphyrin (TCPP) were successfully constructed under solvothermal conditions. As a novel architectured photocatalyst (triclinic, C48H29N4O10PdYb), Pd/Yb-PMOF manifested diverse metal active sites, suitable bandgap positions, prominent visible light-collecting capacity, excellent carrier transfer efficiency, and obvious synergistic effect between ytterbium and palladium ions. Consequently, such a bimetallic MOF exhibited strengthened photocatalytic hydrogen evolution performance. Concretely, its hydrogen generation efficiency was up to 3196.42 μmol g-1 h-1 with 2 wt % Pt as a cocatalyst under visible light illumination. Our work demonstrates a promising strategy for highly efficient visible-light catalysts based on bimetallic-trimmed porphyrin MOFs.

Reticular Chemistry of the Fcu-Type Gd(III)-Doped Metal-Organic Framework for T1 -Weighted Magnetic Resonance Imaging

Nanoscale metal-organic frameworks (nanoMOFs) are emerging as an important class of nanomaterials for the systematical investigation of biomedically relevant structure-property relationship (SPR) due to their highly tailorable features. In this work, the reticular chemistry approach is shown to explore the SPR of a fcu-type Zr(IV)-nanoMOF for T1 -weighted magnetic resonance imaging (MRI). Isoreticular replacement of the eight-coordinated square-antiprismatic Zr(IV) by nine-coordinated Gd(III) brings a stoichiometric water capped on the square-antiprismatic site, enabling the relaxation transfer in the inner-sphere, giving the r1 value of 4.55 mM-1 ·s-1 at the doping ratio of Gd : Zr = 1 : 1. Then, these isoreticular engineering studies provide feasible ways to facilitate the relaxation transfer in the second- and outer-sphere of the Gd(III)-doped Zr-oxo cluster for the relaxation respectively. Finally, these in vitro and in vivo MRI studies revealed that the Gd(III)-doped Zr-oxo cluster aggregated underlying the fcu-type framework surpasses its discrete molecular cluster for MRI. These results demonstrated that there is plenty of room inside MOFs for T1 -weighted MRI by reticular chemistry.

Metal-Organic Frameworks: Versatile Platforms for Biomedical Innovations

This review article explores the multiple applications and potential of metal-organic frameworks (MOFs) in the biomedical field. With their highly versatile and tunable properties, MOFs present many possibilities, including drug delivery, biomolecule recognition, biosensors, and immunotherapy. Their crystal structure allows precise tuning, with the ligand typology and metal geometry playing critical roles. MOFs' ability to encapsulate drugs and exhibit pH-triggered release makes them ideal candidates for precision medicine, including cancer treatment. They are also potential gene carriers for genetic disorders and have been used in biosensors and as contrast agents for magnetic resonance imaging. Despite the complexities encountered in modulating properties and interactions with biological systems, further research on MOFs is imperative. The primary focus of this review is to provide a comprehensive examination of MOFs in these applications, highlighting the current achievements and complexities encountered. Such efforts will uncover their untapped potential in creating innovative tools for biomedical applications, emphasizing the need to invest in the continued exploration of this promising field.

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.

Thermally activated bipyridyl-based Mn-MOFs with Lewis acid-base bifunctional sites for highly efficient catalytic cycloaddition of CO2 with epoxides and Knoevenagel condensation reactions

Metal-organic frameworks (MOFs) have become preferred heterogeneous catalytic materials for many reactions due to their advantages such as porosity and abundant active sites. Here, a 3D Mn-MOF-1 [Mn₂(DPP)(H₂O)₃]·6H₂O (DPP = 2,6-di(2,4-dicarboxyphenyl)-4-(pyridine-4-yl)pyridine) was successfully synthesized under solvothermal conditions. This Mn-MOF-1 possesses a 3D structure constructed by the combination of a 1D chain and the DPP^4- ligand and features a micropore with a 1D drum-like shaped channel. Interestingly, Mn-MOF-1 can maintain the structure unchanged by the removal of coordinated and lattice water molecules, whose activated state (denoted as Mn-MOF-1a) contains rich Lewis acid sites (tetra- and pentacoordinated Mn²⁺ ions) and Lewis base sites (N_pyridine atoms). Furthermore, Mn-MOF-1a shows excellent stability, which can be used to catalyze CO₂ cycloaddition reactions efficiently under eco-friendly, solvent-free conditions. In addition, the synergistic effect of Mn-MOF-1a resulted in its promising potential in Knoevenagel condensation under ambient conditions. More importantly, the heterogeneous catalyst Mn-MOF-1a can be recycled and reused without an obvious decrease of activity for at least 5 reaction cycles. This work not only paves the way for the construction of Lewis acid-base bifunctional MOFs based on pyridyl-based polycarboxylate ligands but also demonstrates that Mn-based MOFs hold great promise as a heterogeneous catalyst toward both CO₂ epoxidation and Knoevenagel condensation reactions.