Metal-organic-frameworks for biomedical applications in drug delivery, and as MRI contrast agents

Recent Advances in Metal-Organic Framework (MOF) Asymmetric Membranes/Composites for Biomedical Applications

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials composed of metal and organic material. MOFs have fascinating properties, such as fine tunability, large specific surface area, and high porosity. MOFs are widely used for environmental protection, biosensors, regenerative medicine, medical engineering, cell therapy, catalysts, and drug delivery. Recent studies have reported various significant properties of MOFs for biomedical applications, such as drug detection and delivery. In contrast, MOFs have limitations such as low stability and low specificity in binding to the target. MOF-based membranes improve the stability and specificity of conventional MOFs by increasing the surface area and developing the possibility of MOF-ligand binding, while conjugated membranes dramatically increase the area of active functional groups. This special property makes them attractive for drug and biosensor fabrication, as both the spreading and solubility components of the porosity can be changed. Asymmetric membranes are a structure with high potential in the biomedical field, due to the different characteristics on its two surfaces, the possibility of adjusting various properties such as the size of porosity, transfer rate and selectivity, and surface properties such as hydrophilicity and hydrophobicity. MOF assisted asymmetric membranes can provide a platform with different properties and characteristics in the biomedical field. The latest version of MOF materials/membranes has several potential applications, especially in medical engineering, cell therapy, drug delivery, and regenerative medicine, which will be discussed in this review, along with their advantages, disadvantages, and challenges.

Plasma Meets MOFs: Synthesis, Modifications, and Functionalities

As a porous and network materials consisting of metals and organic ligands, metal-organic frameworks (MOFs) have become one of excellent crystalline porous materials and play an important role in the era about materials science. Plasma, as a useful tool for stimulating efficient reactions under many conditions, and the plasma-assisted technology gets more attractions and endows MOFs more properties. Based on its feature, the research about the modifications and functionalities of MOFs have been developing a certain extent. This review contains a description of the methods for plasma-assisted modification and synthesis of MOFs, with specifically focusing on the plasma-assisted potential for modifications and functionalities of MOFs. The different applications of plasma-assisted MOFs were also presented.

A Robust Strontium Coordination Polymer with Selective and Sensitive Fluorescence Sensing Ability for Fe3+ Ions

Exploration of sensitive and selective fluorescence sensors towards toxic metal species is of great importance to solve metal pollution issues. In this work, a three-dimensional (3D) strontium coordination polymer of Sr₂(tcbpe) (H₄tcbpe = 1,1,2,2-tetrakis(4-(4-carboxy-phenyl)phenyl)ethene) has been synthesized and developed as a fluorescent sensor to Fe³⁺ ions. Sr₂(tcbpe) shows a mechanochromic fluorescence with emission shifting from blue of the pristine to green after being ground. Notably, based on a fluorescence quenching mechanism, Sr₂(tcbpe) displays a sensitive and selective fluorescent sensing behavior to Fe³⁺ ions with a detection limit of 0.14 mM. Moreover, Sr₂(tcbpe) exhibits high tolerance to water in a wide pH range (pH = 3-13), demonstrating that Sr₂(tcbpe) is a potential fluorescent sensor of Fe³⁺ in water.

pH-Responsive Metal-Organic Framework Thin Film for Drug Delivery

In this work, surface-supportive MIL-88B(Fe) was explored as a pH-stimuli thin film to release ibuprofen as a model drug. We used surface plasmon resonance microscopy to study the pH-responsive behaviors of MIL-88B(Fe) film in real time. A dissociation constant of (6.10 ± 0.86) × 10^-3 s^-1 was measured for the MIL-88B(Fe) film in an acidic condition (pH 6.3), which is about 10 times higher than the dissociation of the same film in a neutral pH condition. MIL-88B(Fe) films are also capable of loading around 6.0 μg/cm² of ibuprofen, which was measured using a quartz crystal microbalance (QCM). Drug release profiles were compared in both acidic and neutral pH conditions (pH 6.3 and 7.4) using a QCM cell to model the drug release in healthy body systems and those containing inflammatory tissues or cancerous tumors. It was found that the amount of drug released in acidic environments had been significantly higher compared to that in a neutral system within 55 h of testing time. The pH-sensitive chemical bond breaking between Fe³⁺ and the carboxylate ligands is the leading cause of drug release in acidic conditions. This work exhibits the potential of using MOF thin films as pH-triggered drug delivery systems.

In silico identification and synthesis of a multi-drug loaded MOF for treating tuberculosis

Conventional drug delivery systems have been applied to a myriad of active ingredients but may be difficult to tailor for a given drug. Herein, we put forth a new strategy, which designs and selects the drug delivery material by considering the properties of encapsulated drugs (even multiple drugs, simultaneously). Specifically, through an in-silico screening process of 5109 MOFs using grand canonical Monte Carlo simulations, a customized MOF (referred as BIO-MOF-100) was selected and experimentally verified to be biologically stable, and capable of loading 3 anti-Tuberculosis drugs Rifampicin+Isoniazid+Pyrazinamide at 10% + 28% + 23% wt/wt (total > 50% by weight). Notably, the customized BIO-MOF-100 delivery system cleared naturally Pyrazinamide-resistant Bacillus Calmette-Guérin, reduced growth of virulent Erdman infection in macaque macrophages 10-100-fold compared to soluble drugs in vitro and was also significantly reduced Erdman growth in mice. These data suggest that the methodology of identifying-synthesizing materials can be used to generate solutions for challenging applications such as simultaneous delivery of multiple, small hydrophilic and hydrophobic molecules in the same molecular framework.

Structural Diversity and Carbon Dioxide Sorption Selectivity of Zinc(II) Metal-Organic Frameworks Based on Bis(1,2,4-triazol-1-yl)methane and Terephthalic Acid

A three-component reaction between the 1,4-benzenedicarboxylic (terephthalic) acid (H₂bdc), bis(1,2,4-triazol-1-yl)methane (btrm) and zinc nitrate was studied, and three new coordination polymers were isolated by a careful selection of the reaction conditions. Coordination polymers {[Zn₃(DMF)(btrm)(bdc)₃]·nDMF}_∞ and {[Zn₃(btrm)(bdc)₃]·nDMF}_∞ containing trinuclear {Zn₃(bdc)₃} secondary building units are joined by btrm auxiliary linkers into three-dimensional metal–organic frameworks. The coordination polymer {[Zn(bdc)(btrm)]∙nDMF}_∞ consists of Zn²⁺ cations joined by bdc²⁻ and btrm linkers into a two-fold interpenetrated network. Upon activation, MOF [Zn₃(btrm)(bdc)₃]_∞ demonstrated CO₂/N₂ adsorption selectivity with an ideal adsorbed solution theory (IAST) factor of 21. All three MOF demonstrated photoluminescence with a maximum near 435–440 nm upon excitation at 330 nm.

Recent advances of the core-shell MOFs in tumour therapy

Coordination chemistry has always been vital to explore the material prominence of metal-organic systems. The metal-organic chemistry plays a fundamental role in decisive structural features, which are accountable for tuning the properties of materials. Tumour therapy has become an important research field of medical treatment in the world. Metal-organic frameworks (MOFs) have attracted extensive interest in medical science research due to their large effective surface area, clear pore network, and critical catalytic performance. Compared with traditional MOF materials, MOF materials with core-shell structures have a higher loading rate and better stability, which can overcome a single function. They have been successfully used in tumour medical research and have excellent prospects for diagnosing and treating various tumours. The current review article thoroughly describes the various synthetic approaches for engineering core-shell MOF materials, the structural types, and the potential functional applications. We also discussed core-shell MOF materials for the various treatment of tumours, such as tumour chemotherapy, tumour phototherapy and tumour microenvironment anti-hypoxia therapy. In this paper, the synthesized procedures of core-shell MOFs and their applications for tumour treatment have been discussed, and their future research has prospected. The current improved strategies, challenges, and prospects are also presented because of the metal-organic chemistry governing the structural modification of core-shell MOFs for tumour therapy applications. Therefore, the present review article opens a new door for medicinal chemists to tune the structural features of the core-shell MOF materials to modulate tumour therapy with simple, low-cost materials for better human lives.

Chiral Metal-Organic Frameworks

In the past two decades, metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) assembled from metal ions or clusters and organic linkers via metal-ligand coordination bonds have captivated significant scientific interest on account of their high crystallinity, exceptional porosity, and tunable pore size, high modularity, and diverse functionality. The opportunity to achieve functional porous materials by design with promising properties, unattainable for solid-state materials in general, distinguishes MOFs from other classes of materials, in particular, traditional porous materials such as activated carbon, silica, and zeolites, thereby leading to complementary properties. Scientists have conducted intense research in the production of chiral MOF (CMOF) materials for specific applications including but not limited to chiral recognition, separation, and catalysis since the discovery of the first functional CMOF (i.e., d- or l-POST-1). At present, CMOFs have become interdisciplinary between chirality chemistry, coordination chemistry, and material chemistry, which involve in many subjects including chemistry, physics, optics, medicine, pharmacology, biology, crystal engineering, environmental science, etc. In this review, we will systematically summarize the recent progress of CMOFs regarding design strategies, synthetic approaches, and cutting-edge applications. In particular, we will highlight the successful implementation of CMOFs in asymmetric catalysis, enantioselective separation, enantioselective recognition, and sensing. We envision that this review will provide readers a good understanding of CMOF chemistry and, more importantly, facilitate research endeavors for the rational design of multifunctional CMOFs and their industrial implementation.

Tailoring biocompatibility of composite scaffolds of collagen/guar gum with metal-organic frameworks

Metal-organic frameworks (MOFs) are microporous materials with high potential for biomedical applications. They are useful as drug delivery systems, antibacterials, and biosensors. Recently, composite materials comprised of polymer matrixes and MOFs have gained relevance in the biomedical field due to their high potential as materials to accelerate wound healing. In this work, we studied the potential applications of composite hydrogels containing MgMOF74, CaMOF74, and Zn(Atz)(Py). The composite hydrogels are biodegradable, being completely degraded after 15 days by the action of collagenase and papain. The composites showed high biocompatibility reaching cell viabilities up to 165.3 ± 8.6% and 112.3 ± 12.8% for porcine fibroblasts and human monocytes, respectively. The composites did not show hemolytic character and they showed antibacterial activity against Escherichia coli reaching up to 84 ± 5% of inhibition compared with amoxicillin (20 ppm). Further, the immunological assays revealed that the composites produce a favorable cell signaling stimulating the secretion of the TGF-β and MCP-1 cytokines and maintaining the secretion of TNF-α in normal levels. Finally, the composites showed potential to be used as controlled drug delivery systems reaching a release efficiency of 30.5 ± 2.5% for ketorolac. Finally, results revealed that ColGG-Zn(Atz)(Py) was the best formulation evaluated.

Advances in antitumor nanomedicine based on functional metal-organic frameworks beyond drug carriers

Nanoscale metal-organic frameworks (MOFs) have attracted widespread interest due to their unique properties including a tunable porous structure, high drug loading capacity, structural diversity, and outstanding biocompatibility. MOFs have been extensively explored as drug nanocarriers in biotherapeutics. However, by harnessing the functionality of ligands and metal ions or clusters in MOFs, the applications of MOFs can be extended beyond drug delivery vehicles. Based on the intrinsic properties of the components of MOFs (e.g. magnetic moments of metal ions and fluorescence of ligands), different imaging modes can be achieved with varied MOFs. With careful design of the composition of MOFs (e.g. modification of organic linkers), they can respond to tumor microenvironments to realize on-demand treatment. By incorporating porphyrin-based ligands (photosensitizers for photodynamic therapy) or high-Z metal ions (radiosensitizers for radiotherapy) into the scaffold of MOFs, MOFs themselves can act as anticancer therapeutic agents. In this review, we highlight the application of MOFs from the above-mentioned aspects and discuss the prospects and challenges for using MOFs in stimuli-responsive imaging-guided antitumor therapy.

Journey to the Market: The Evolution of Biodegradable Drug Delivery Systems

Biodegradable polymers have been used as carriers in drug delivery systems for more than four decades. Early work used crude natural materials for particle fabrication, whereas more recent work has utilized synthetic polymers. Applications include the macroscale, the microscale, and the nanoscale. Since pioneering work in the 1960’s, an array of products that use biodegradable polymers to encapsulate the desired drug payload have been approved for human use by international regulatory agencies. The commercial success of these products has led to further research in the field aimed at bringing forward new formulation types for improved delivery of various small molecule and biologic drugs. Here, we review recent advances in the development of these materials and we provide insight on their drug delivery application. We also address payload encapsulation and drug release mechanisms from biodegradable formulations and their application in approved therapeutic products.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

All-in-One Nanomedicine: Multifunctional Single-Component Nanoparticles for Cancer Theranostics

The development of cancer diagnostic imaging and treatment is a major concern worldwide. By integrating imaging and therapy into one theranostic nanoplatform for simultaneously detecting tumors, evaluating the targeting ability and timely monitoring therapeutic responses provide more opportunities for precision medicine. Among various theranostic nanosystems, a series of single-component nanoparticles (NPs) have been developed for "all-in-one" theranostics, which presents the unique properties of facile preparation, simple composition, defined structure, high reproducibility, and excellent biocompatibility. Specifically, utilizing single-component NPs for both diagnostics and therapeutics can reduce the possible numerous untoward side effects and risks to the living body. In this review, the recent progress of multifunctional single-component NPs in the applications of cancer theranostics is systematically summarized. Notably, the structure design, categories of NPs, targeted strategies, biomedical applications, potential barriers, challenges, and prospects for the future clinical practice of this rapidly growing field are discussed.

Nanoscale Metal-Organic Frameworks: Recent developments in synthesis, modifications and bioimaging applications

Porous Metal-Organic Frameworks (MOFs) have emerged as eye-catching materials in recent years. They are widely used in numerous fields of chemistry thanks to their desirable properties. MOFs have a key role in the development of bioimaging platforms that are hopefully expected to effectually pave the way for accurate and selective detection and diagnosis of abnormalities. Recently, many types of MOFs have been employed for detection of RNA, DNA, enzyme activity and small-biomolecules, as well as for magnetic resonance imaging (MRI) and computed tomography (CT), which are valuable methods for clinical analysis. The optimal performance of the MOF in the bio-imaging field depends on the core structure, synthesis method and modifications processes. In this review, we have attempted to present crucial parameters for designing and achieving an efficient MOF as bioimaging platforms, and provide a roadmap for researchers in this field. Moreover, the influence of modifications/fractionalizations on MOFs performance has been thoroughly discussed and challenging problems have been extensively addressed. Consideration is mainly focused on the principal concepts and applications that have been achieved to modify and synthesize advanced MOFs for future applications.

Preparation of Ni-microsphere and Cu-MOF using aspartic acid as coordinating ligand and study of their catalytic properties in Stille and sulfoxidation reactions

In this study, the thermal and catalytic behavior of Ni-microsphere and Cu-MOF were investigated with aspartic acid as the coordinating ligand with different morphologies. The Ni-microsphere and Cu-MOF with aspartic acid, as the coordinating ligand, were prepared via a solvothermal method. The morphology and porosity of the obtained Ni microsphere and Cu-MOF were characterized by XRD, FTIR, TGA, DSC, BET and SEM techniques. The catalytic activity of the Ni-microsphere and Cu-MOF was examined in Stille and sulfoxidation reactions. The Ni microsphere and Cu-MOF were easily isolated from the reaction mixtures by simple filtration and then recycled four times without any reduction of catalytic efficiency.

Applications of nanoscale metal-organic frameworks as imaging agents in biology and medicine

Nanoscale metal-organic frameworks (NMOFs) are an interesting and unique class of hybrid porous materials constructed by the self-assembly of metal ions/clusters with organic linkers. The high storage capacities, facile synthesis, easy surface functionalization, diverse compositions and excellent biocompatibilities of NMOFs have made them promising agents for theranostic applications. By combination of a large variety of metal ions and organic ligands, and incorporation of desired molecular functionalities including imaging modalities and therapeutic molecules, diverse MOF structures with versatile functionalities can be obtained and utilized in biomedical imaging and drug delivery. In recent years, NMOFs have attracted great interest as imaging agents in optical imaging (OI), magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET) and photoacoustic imaging (PAI). Furthermore, the significant porosity of MOFs allows them to be loaded with multiple imaging agents and therapeutics simultaneously and applied for multimodal imaging and therapy as a single entity. In this review, which is intended as an introduction to the use of MOFs in biomedical imaging for a reader entering the subject, we summarize the up-to-date progress of NMOFs as bioimaging agents, giving (i) a broad perspective of the varying imaging techniques that MOFs can enable, (ii) the different routes to manufacturing functionalised MOF nanoparticles and hybrids, and (iii) the integration of imaging with differing therapeutic techniques. The current challenges and perspectives of NMOFs for their further clinical translation are also highlighted and discussed.

Multifaceted Study of the Interactions between CPO-27-Ni and Polyurethane and Their Impact on Nitric Oxide Release Performance

A multifaceted study involving focused ion beam scanning electron microscopy techniques, mechanical analysis, water adsorption measurements, and molecular simulations is employed to rationalize the nitric oxide release performance of polyurethane films containing 5, 10, 20, and 40 wt % of the metal-organic framework (MOF) CPO-27-Ni. The polymer and the MOF are first demonstrated to exhibit excellent compatibility. This is reflected in the even distribution and encapsulation of large wt % MOF loadings throughout the full thickness of the films and by the rather minimal influence of the MOF on the mechanical properties of the polymer at low wt %. The NO release efficiency of the MOF is attenuated by the polymer and found to depend on wt % of MOF loading. The formation of a fully connected network of MOF agglomerates within the films at higher wt % is proposed to contribute to a more complex guest transport in these formulations, resulting in a reduction of NO release efficiency and film ductility. An optimum MOF loading of 10 wt % is identified for maximizing NO release without adversely impacting the polymer properties. Bactericidal efficacy of released NO from the films is demonstrated against Pseudomonas aeruginosa, with a >8 log₁₀ reduction in cell density observed after a contact period of 24 h.

Effect of Neodymium Doping on MRI Relaxivity of Gadolinium Oxide Nanoparticles

Background

Gadolinium oxide nanoparticles as positive contrast material of magnetic resonance imaging (MRI) have attracted a great attention due to the appropriate magnetic properties. One of the most desirable features of these nanoparticles is their ability of doping with other lanthanides which can change their properties.

Objective

This study aimed to investigate the effect of neodymium doping on MRI relaxivity of the gadolinium oxide nanoparticles.

Material and Methods

In this experimental study, the oleic acid coated gadolinium oxide nanoparticles and the neodymium doped nanoparticles were prepared by polymer pyrolysis method. X-ray diffraction test and scanning electron microscopy were used for characterization of the particles. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to investigate the in vitro cell toxicity of the nanoparticles. The r1 and r2 relaxivities were extracted from the T1 and T2 weighted MR images, respectively.

Results

The average size of the cytocompatible spherical-like shape nanoparticles was 40 nm. The neodymium doped nanoparticles produced a significant decrease in the r1 relaxivity, and a 1.7 fold increase in the r2 relaxivity compared to the gadolinium oxide nanoparticles.

Conclusion

Doping of neodymium into the gadolinium oxide nanoparticles suppresses the r1 relaxivity and enhances the r2 relaxivity of the nanoparticles.

Coordination Polymers Based on Highly Emissive Ligands: Synthesis and Functional Properties

Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4'-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4',4''-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

Engineering Secretory Amyloids for Remote and Highly Selective Destruction of Metastatic Foci

Functional amyloids produced in bacteria as nanoscale inclusion bodies are intriguing but poorly explored protein materials with wide therapeutic potential. Since they release functional polypeptides under physiological conditions, these materials can be potentially tailored as mimetic of secretory granules for slow systemic delivery of smart protein drugs. To explore this possibility, bacterial inclusion bodies formed by a self-assembled, tumor-targeted Pseudomonas exotoxin (PE24) are administered subcutaneously in mouse models of human metastatic colorectal cancer, for sustained secretion of tumor-targeted therapeutic nanoparticles. These proteins are functionalized with a peptidic ligand of CXCR4, a chemokine receptor overexpressed in metastatic cancer stem cells that confers high selective cytotoxicity in vitro and in vivo. In the mouse models of human colorectal cancer, time-deferred anticancer activity is detected after the subcutaneous deposition of 500 µg of PE24-based amyloids, which promotes a dramatic arrest of tumor growth in the absence of side toxicity. In addition, long-term prevention of lymphatic, hematogenous, and peritoneal metastases is achieved. These results reveal the biomedical potential and versatility of bacterial inclusion bodies as novel tunable secretory materials usable in delivery, and they also instruct how therapeutic proteins, even with high functional and structural complexity, can be packaged in this convenient format.

Metal Organic Framework@Polysilsesequioxane Core/Shell-Structured Nanoplatform for Drug Delivery

Modern pharmaceutics requires novel drug loading platforms with high drug loading capacity, controlled release, high stability, and good biocompacity. Metal-organic frameworks (MOFs) show promising applications in biomedicine owing to their extraordinarily high surface area, tunable pore size, and adjustable internal surface properties. However, MOFs have low stability due to weak coordinate bonding and limited biocompatibility, limiting their bioapplication. In this study, we fabricated MOFs/polysilsesquioxane (PSQ) nanocomposites and utilized them as drug carriers. Amine-functionalized MOF (UiO-66-NH2) nanoparticles were synthesized and encapsulated with epoxy-functionalized polysilsesquioxane layer on the surface via a facile process. MOFs possessed high surface area and regular micropores, and PSQs offered stability, inertness, and functionality. The obtained UiO-66-NH2@EPSQ nanocomposites were utilized as carriers for ibuprofen, a drug with carboxylic groups on the surface, and demonstrated high drug loading capacity and well-controlled release property. The UiO-66-NH2@EPSQ nanocomposite exhibited low cytotoxicity to HeLa cells within a wide concentration range of 10-100 µg/mL, as estimated by the MTT method. The UiO-66-NH2@EPSQ drug release system could be a potential platform in the field of controlled drug delivery.

Polymer/Metal Organic Framework (MOF) Nanocomposites for Biomedical Applications

The utilization of polymer/metal organic framework (MOF) nanocomposites in various biomedical applications has been widely studied due to their unique properties that arise from MOFs or hybrid composite systems. This review focuses on the types of polymer/MOF nanocomposites used in drug delivery and imaging applications. Initially, a comprehensive introduction to the synthesis and structure of MOFs and bio-MOFs is presented. Subsequently, the properties and the performance of polymer/MOF nanocomposites used in these applications are examined, in relation to the approach applied for their synthesis: (i) non-covalent attachment, (ii) covalent attachment, (iii) polymer coordination to metal ions, (iv) MOF encapsulation in polymers, and (v) other strategies. A critical comparison and discussion of the effectiveness of polymer/MOF nanocomposites regarding their synthesis methods and their structural characteristics is presented.

Metal–organic frameworks: a future toolbox for biomedicine?

The present review focuses on the use of Metal–Organic Frameworks, (MOFs) highlighting the most recent developments in the biological field and as bio-sensors.

Novel route to size-controlled synthesis of MnFe2O4@MOF core-shell nanoparticles

Nanoscale metal-organic framework (nMOF) is a distinctive type of crystalline compounds that consists of metal ions or clusters coordinated to organic ligands. This hybrid material has attracted fast-growing attention due to its tunable pore sizes, remarkably large surface areas, and high selectivity in uptaking small molecules. In this paper, we successfully developed a novel approach for synthesizing a core-shell structure with MIL-88B-4CH₃ as a tunable nMOF shell and MnFe₂O₄ as a magnetic core. We controlled the growth of the core-shell particles by introducing different acetic acid concentrations and with varied reaction time. Acetic acid works as a modulating agent that allows for nucleation rate control, leading to tailored particle size. Our results show an increase in the particle size with increasing acetic acid concentration or reaction time. This study provides a valuable methodology for synthesis of core-shell nanoparticles with controlled sizes based on nMOF platforms.

Recent developments on zinc(ii) metal-organic framework nanocarriers for physiological pH-responsive drug delivery

The high storage capacities and excellent biocompatibilities of zinc(ii) metal-organic frameworks (Zn-MOFs) have made them outstanding candidates as drug delivery carriers. Recent studies on the pH-responsive processes based on carrier-drug interactions have proven them to be the most efficient and effective way to control the release profiles of drugs. To satisfy the ever-growing demand in cancer therapy, great efforts are being devoted to the development of methods to precisely control drug release and achieve targeted use of an active substance at the right time and place. In this review article, we discuss the diverse stimuli based on Zn-MOFs carriers that have been achieved upon external activation from single pH-stimulus-responsive or/and multiple pH-stimuli-responsive viewpoints. Also, the perspectives and future challenges in this type of carrier system are discussed.

Functional Metal Organic Framework/SiO2 Nanocomposites: From Versatile Synthesis to Advanced Applications

Metal organic frameworks (MOFs), also called porous coordination polymers, have attracted extensive attention as molecular-level organic-inorganic hybrid supramolecular solid materials bridged by metal ions/clusters and organic ligands. Given their advantages, such as their high specific surface area, high porosity, and open active metal sites, MOFs offer great potential for gas storage, adsorption, catalysis, pollute removal, and biomedicine. However, the relatively weak stability and poor mechanical property of most MOFs have limited the practical application of such materials. Recently, the combination of MOFs with inorganic materials has been found to provide a possible strategy to solve such limitations. Silica, which has excellent chemical stability and mechanical properties, shows great advantages in compounding with MOFs to improve their properties and performance. It not only provides structured support for MOF materials but also improves the stability of materials through hydrophobic interaction or covalent bonding. This review summarizes the fabrication strategy, structural characteristics, and applications of MOF/silica composites, focusing on their application in chromatographic column separation, catalysis, biomedicine, and adsorption. The challenges of the application of MOF/SiO2 composites are addressed, and future developments are prospected.

Toxicity screening of two prevalent metal organic frameworks for therapeutic use in human lung epithelial cells

INTRODUCTION

The flexibility and tunability of metal organic frameworks (MOFs), crystalline porous materials composed of a network of metal ions coordinated by organic ligands, confer their variety of applications as drug delivery systems or as sensing and imaging agents. However, such properties also add to the difficulty in ensuring their safe implementation when interaction with biological systems is considered.

METHODS

In the current study, we used real-time sensorial strategies and cellular-based approaches to allow for fast and effective screening of two MOFs of prevalent use, namely, MIL-160 representative of a hydrophilic and ZIF-8 representative of a hydrophobic framework. The two MOFs were synthesized "in house" and exposed to human bronchial epithelial (BEAS-2B) cells, a pertinent toxicological screening model.

RESULTS

Analysis allowed evaluation and differentiation of particle-induced cellular effects as well identification of different degrees and routes of toxicity, all in a high-throughput manner. Our results show the importance of performing screening toxicity assessments before introducing MOFs to biomedical applications.

DISCUSSION

Our proposed screening assays could be extended to a wider variety of cell lines to allow for identification of any deleterious effects of MOFs, with the range of toxic mechanisms to be differentiated based on cell viability, morphology and cell-substrate interactions, respectively.

CONCLUSION

Our analysis highlights the importance of considering the physicochemical properties of MOFs when recommending a MOF-based therapeutic option or MOFs implementation in biomedical applications.

Zinc-based metal-organic frameworks as nontoxic and biodegradable platforms for biomedical applications: review study

Development of biomedical systems for controllable drug delivery systems and construction of biosensors is imperative to reduce side effects of common treatment techniques and enhance the therapeutic efficacy. To address this issue, metal-organic frameworks (MOFs) as hybrid porous polymeric structures have attracted worldwide attention due to their unprecedented opportunities in vast range of applications in diverse fields including chemistry, biological, and medicinal science as gas storage/separation, sensing, and drug delivery systems. Recently, biomedical application has become an interesting and promising issue for development and usage of multi-functional MOFs. Flexible chemical composition and versatile porous structure of MOFs enable the engineering and enhancement of their medical formulation and functionality as practical carriers for whether therapeutic or imaging agents. One important point in this domain is the efficient delivery of drugs in the body using nontoxic and biodegradable carriers. This review brings together the literatures that addressing the biomedical applications of Zinc-based MOFs (i.e. as drug delivery systems or nontoxic agent in matter of therapeutic applications) to present recent achievements in this interesting field.

A Series of Early Lanthanide Chloranilate Frameworks with a Square Grid Topology

A series of lanthanide chloranilate frameworks containing a (4,4)-net with LaIII, CeIII, NdIII, SmIII, and EuIII have been synthesised and structurally characterised. Two structure types of square grids were obtained for these frameworks. Type 1 consists of the formula (Et4N)[Ln(can)2(H2O)] (Ln=LaIII, CeIII, NdIII; H2can=chloranilic acid) and crystallised in the tetragonal space group I4/m, featuring a nine-coordinate lanthanide ion with a coordinated water molecule and four chloranilate ligands. Type 2, (Et4N)[Ln(can)2] (SmIII and EuIII) crystallised in the I4/mcm space group, and contains an eight-coordinate lanthanide ion without a coordinated water molecule. A single-crystal-to-single-crystal transformation was carried out for (Et4N)[Nd(can)2(H2O)] on removal of the coordinated aqua ligand.

Electrochemical and spectroscopic properties of a cobalt framework with (3,7)-c topology

A Co(ii) framework containing a 7-c Co dimer forms a (3,7)-c binodal net incorporating redox-active triarylamine and light-active azobenzene moieties.

Lanthanide phosphate (LnPO4 ) rods as bio-probes: A systematic investigation on structural, optical, magnetic, and biological characteristics

The proposed work involves an exclusive study on the synthesis protocol, crystal structure analysis, and imaging contrast features of unique lanthanide phosphates (LnPO₄ ). XRD and Raman spectra affirmed the ability of the proposed synthesis technique to achieve unique LnPO₄ devoid of impurities. The crystal structure analysis confirms the P121/c1 space setting of NdPO₄ , EuPO₄ , GdPO₄ , and TbPO₄ that all uniformly crystallizes in monoclinic unit cell. In a similar manner, the tetragonal crystal setting of DyPO₄ , ErPO₄ , HoPO₄ , and YbPO₄ that unvaryingly possess the I41/amd space setting is confirmed. Under the same synthesis conditions, the monoclinic (Eu) and tetragonal (Ho) lanthanide phosphates displayed uniform rod-like morphologies. Absorption and luminescence properties of unique LnPO₄ were determined. In vitro biological studies demonstrated low toxicity levels of LnPO₄ and clearly distinguished fluorescence of TbPO₄ and EuPO₄ in Y79, retinoblastoma cell lines. The paramagnetic response of GdPO₄ , NdPO₄ , DyPO₄ , TbPO₄ , and HoPO₄ facilitated excellent magnetic resonance imaging (MRI) contrast features. Meanwhile, GdPO₄ , DyPO₄ , HoPO₄ , and YbPO₄ possessing higher X-ray absorption coefficient than clinical contrast Omnipaque™ exhibited high computed tomography (CT) efficiency. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1372-1383, 2019.

Bimetallic Zeolitic Imidazolate Framework as an Intrinsic Two-Photon Fluorescence and pH-Responsive MR Imaging Agent

Zeolitic imidazolate framework-8 (ZIF-8) has received wide attention in recent years as a potential drug vehicle for the treatment of cancer due to its acid-responsiveness and moderate biocompatibility. However, its congenital deficiency of intrinsic imaging capability limits its wider applications; therefore, a postsynthetic exchange approach was utilized to introduce paramagnetic manganese(II) ions into the ZIF-8 matrix. As a result, bimetallic zeolitic imidazolate frameworks (Mn-Zn-ZIF) were thus fabricated and exhibited pH-responsive T1-weighted magnetic resonance imaging (MRI) contrast effect. Remarkably, we also found its own fluorescence derived from 2-methylimidazole, which is the first report of the intrinsic two-photon fluorescence imaging of ZIFs to our knowledge. Mn-Zn-ZIF still preserves the original properties of ZIF-8 of high surface areas, microporosity, and acid sensitivity. After further PEGylation of Mn-Zn-ZIF, the nanoparticles showed no obvious toxicity and its MRI contrast effect has also been enhanced. Our work highlights the promise of modified zeolitic imidazolate frameworks as potential cancer theranostic platforms.

Prussian blue nanoparticles: Synthesis, surface modification, and application in cancer treatment

This review outlines recently developed Prussian blue nanoparticle (PB NPs)-based multimodal imaging-guided chemo-photothermal strategies for cancer diagnosis and treatment in order to provide insight into the future of the field. The primary limitation of existing therapeutics is the lack of selectivity in drug delivery: they target healthy and cancerous cells alike. In this paper, we provide a thorough review of diverse synthetic and surface engineering techniques for PB NP fabrication. We have elucidated the various targeting approaches employed to deliver the therapeutic and imaging ligands into the tumor area, and outlined methods for enhancement of the tumor ablative ability of the NPS, including several important combinatorial approaches. In addition, we have summarized different in vitro and in vivo effects of PB NP-based therapies used to overcome both systemic and tumor-associated local barriers. An important new approach - PB NP-based immune drug delivery, which is an exciting and promising strategy to overcome cancer resistance and tumor recurrence - has been discussed. Finally, we have discussed the current understanding of the toxicological effects of PB NPs and PB NP-based therapeutics. We conclude that PB NP-based multimodal imaging-guided chemo-photothermal therapy offers new treatment strategies to overcome current hurdles in cancer diagnosis and treatment.

Multistimuli Responsive Core-Shell Nanoplatform Constructed from Fe3 O4 @MOF Equipped with Pillar[6]arene Nanovalves

An intelligent theranostic nanoplatform based on nanovalve operated metal-organic framework (MOF) core-shell hybrids, incorporating tumorous microenvironment-triggered drug release, magnetic resonance imaging (MRI) guidance, sustained release, and effective chemotherapy in one pot is reported. The core-shell hybrids are constructed by an in situ growth method, in which Fe₃ O₄ particles with superior abilities of MRI and magnetic separation form the core and UiO-66 MOF with high loading capacity compose the shell, and then are surface-installed with pillararene-based pseudorotaxanes as tightness-adjustable nanovalves. This strategy endows the system with the ability of targeted, multistimuli responsive drug release in response to pH changes, temperature variations, and competitive agents. Water-soluble carboxylatopillar[6]arene system achieved sustained drug release over 7 days due to stronger host-guest binding, suggesting that the nanovalve tightness further reinforces the desirable release of anticancer agent over a prolonged time at the lesion site.

Intelligent anticancer drug delivery performances of two poly(N-isopropylacrylamide)-based magnetite nanohydrogels

This article evaluates the anticancer drug delivery performances of two nanohydrogels composed of poly(N-isopropylacrylamide-co-itaconic anhydride) [P(NIPAAm-co-IA)], poly(ethylene glycol) (PEG), and Fe₃O₄ nanoparticles. For this purpose, the magnetite nanohydrogels (MNHGs) were loaded with doxorubicin hydrochloride (DOX) as a universal anticancer drug. The morphologies and magnetic properties of the DOX-loaded MNHGs were investigated using transmission electron microscopy (TEM) and vibrating-sample magnetometer (VSM), respectively. The sizes and zeta potentials (ξ) of the MNHGs and their corresponding DOX-loaded nanosystems were also investigated. The DOX-loaded MNHGs showed the highest drug release values at condition of 41 °C and pH 5.3. The drug-loaded MNHGs at physiological condition (pH 7.4 and 37 °C) exhibited negligible drug release values. In vitro cytotoxic effects of the DOX-loaded MNHGs were extensively evaluated through the assessing survival rate of HeLa cells using the MTT assay, and there in vitro cellular uptake into the mentioned cell line were examined using fluorescent microscopy and fluorescence-activated cell sorting (FACS) flow cytometry analyses. As the results, the DOX-loaded MNHG1 exhibited higher anticancer drug delivery performance in the terms of cytotoxic effect and in vitro cellular uptake. Thus, the developed MNHG1 can be considered as a promising de novo drug delivery system, in part due to its pH and thermal responsive drug release behavior as well as proper magnetite character toward targeted drug delivery.