A Luminescent Mg-Metal-Organic Framework for Sustained Release of 5-Fluorouracil: Appropriate Host-Guest Interaction and Satisfied Acid-Base Resistance

Strong aggregation-induced electrochemiluminescence of pyrene-coordination metal-organic frameworks coupled with zero-valent iron as novel accelerator for ultrasensitive immunoassay

Polycyclic aromatic hydrocarbons (PAHs) are excellent alternative luminophores for electrochemiluminescence (ECL) immunoassays. However, they are inevitably limited by the aggregation-caused quenching effect. In this study, aimed at eliminating the aggregation quenching of PAHs, luminescent metal-organic frameworks (MOFs) with 1,3,6,8-tetra(4-carboxybenzene)pyrene (H4TBAPy) as the ligand were exploited as a novel nano-emitter for the construction of ECL immunoassays. The luminophore exhibits efficient aggregation-induced emission enhancement, good acid-base resistance property and unusual ECL reactivity. In addition, the simultaneous use of potassium persulfate and hydrogen peroxide as dual co-reactants resulted in a synergistic enhancement of the cathodic ECL efficiency. The use of magnetic iron-nickel alloys as the multifunctional sensing platform can further enhance the ECL activity, and its enriched zero-valent iron as a co-reactant accelerator effectively drives ECL analytical performance. Profiting from the excellent characteristics, signal-on ECL immunoassays have been constructed. With carcinoembryonic antigen as the model analysis target, a detection limit of 0.63 pg/mL was obtained within the linear range of 1 pg/mL to 50 ng/mL, accompanied by excellent analytical performance. This report opens a new window for the rational design of efficient ECL illuminators, and the proposed ECL immunoassays may find promising applications in the detection of disease markers.

Crystal Clear: Metal-Organic Frameworks Pioneering the Path to Future Drug Detox

The growing number of acute drug abuse overdoses demands the development of innovative detoxification strategies for emergency purposes. In this study, an innovative approach for the application of porous Zr-based metal-organic frameworks for the treatment of acute overdoses of popular drugs of abuse including amphetamine, methamphetamine, cocaine, and MDMA is presented. A comprehensive approach determining the efficacy and the kinetics of drug removal, considering dosage, adsorption time, and adsorption mechanisms, was tested and corroborated with density functional theory (DFT) modeling. The experimental results showed high removal efficiency reaching up to 90% in the case of the application of the NU-1000 metal-organic framework. The difference Raman spectroscopy method presented in this study corroborated with DFT-based vibrational analysis allows the detection of drug adsorbed in the MOF framework even with as low a concentration as 5 mg/g. Additionally, the drug adsorption mechanisms were modeled with DFT, showing the π-π stacking in a vast majority of considered cases. The performance and influence on the living organisms were evaluated throughout the in vitro and in vivo experiments, indicating that Zr-based MOFs could serve as efficient, organic, safe drug adsorbents.

Recent advances in metal-organic frameworks for stimuli-responsive drug delivery

After entering the human body, drugs for treating diseases, which are prone to delivery and release in an uncontrolled manner, are affected by various factors. Based on this, many researchers utilize various microenvironmental changes encountered during drug delivery to trigger drug release and have proposed stimuli-responsive drug delivery systems. In recent years, metal-organic frameworks (MOFs) have become promising stimuli-responsive agents to release the loaded therapeutic agents at the target site to achieve more precise drug delivery due to their high drug loading, excellent biocompatibility, and high stimuli-responsiveness. The MOF-based stimuli-responsive systems can respond to various stimuli under pathological conditions at the site of the lesion, releasing the loaded therapeutic agent in a controlled manner, and improving the accuracy and safety of drug delivery. Due to the changes in different physical and chemical factors in the pathological process of diseases, the construction of stimuli-responsive systems based on MOFs has become a new direction in drug delivery and controlled release. Based on the background of the rapidly increasing attention to MOFs applied in drug delivery, we aim to review various MOF-based stimuli-responsive drug delivery systems and their response mechanisms to various stimuli. In addition, the current challenges and future perspectives of MOF-based stimuli-responsive drug delivery systems are also discussed in this review.

A reliable QSPR model for predicting drug release rate from metal-organic frameworks: a simple and robust drug delivery approach

During the drug release process, the drug is transferred from the starting point in the drug delivery system to the surface, and then to the release medium. Metal-organic frameworks (MOFs) potentially have unique features to be utilized as promising carriers for drug delivery, due to their suitable pore size, high surface area, and structural flexibility. The loading and release of various therapeutic drugs through the MOFs are effectively accomplished due to their tunable inorganic clusters and organic ligands. Since the drug release rate percentage (RES%) is a significant concern, a quantitative structure-property relationship (QSPR) method was applied to achieve an accurate model predicting the drug release rate from MOFs. Structure-based descriptors, including the number of nitrogen and oxygen atoms, along with two other adjusted descriptors, were applied for obtaining the best multilinear regression (BMLR) model. Drug release rates from 67 MOFs were applied to provide a precise model. The coefficients of determination (R2) for the training and test sets obtained were both 0.9999. The root mean square error for prediction (RMSEP) of the RES% values for the training and test sets were 0.006 and 0.005, respectively. To examine the precision of the model, external validation was performed through a set of new observations, which demonstrated that the model works to a satisfactory degree.

Biocompatible Drug Delivery System Based on a MOF Platform for a Sustained and Controlled Release of the Poorly Soluble Drug Norfloxacin

Norfloxacin (NFX), an important antibacterial fluoroquinolone, is a class IV drug according to the biopharmaceutics classification system (BCS) and has low solubility and permeability issues. Such poor physicochemical properties of drug molecules lead to poor delivery and are of serious concern to the pharmaceutical industry for clinical development. We present here a conceptually new approach to deliver NFX, by loading the drug molecule on the porous platform of a biocompatible metal-organic framework (MOF), MIL-100(Fe). The loading of the drug on the MOF leading to NFX@MIL-100(Fe) was characterized by Fourier transform infrared (FTIR), UV-visible spectroscopy, thermogravimetric analyses (TGA), and nitrogen adsorption studies. Controlled experiments resulted in the high loading of the drug molecule (∼20 wt %) along with the desired sustained release. We could further control the release of norfloxacin by coating drug-loaded MIL-100(Fe) with PEG, PEG{NFX@MIL-100(Fe)}. Both drug delivery systems (DDSs), NFX@MIL-100(Fe) and PEG{NFX@MIL-100(Fe)}, were tested for their biocompatibility through toxicity studies. The DDSs are biocompatible and show insignificant cytotoxicity, as revealed by cell viability studies through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

Identification of folic acid and sulfaquinoxaline using a heterometallic Zn-Eu MOF as a sensor

A d-f heterometallic MOF using the 2,2'-bipyridine-4,4'-dicarboxylic acid ligand (H₂LZ) was obtained by solvothermal synthesis, namely [EuZn(LZ)₂(HCOO)(H₂O)₃]_n (1). The structure analysis shows that compound 1 comprises heterometallic Zn²⁺ and Eu³⁺ ions, which are connected by LZ^2- and HCOO^- anions to form a three-dimensional framework. MOF 1 exhibited high stability of fluorescence intensity in the scope of pH 2-11 in an aqueous solution. Furthermore, MOF 1 served as an excellent selective sensing material for the detection of folic acid in the presence of some imitating materials of the human body and discerned sulfaquinoxaline in sulfonamide drugs with high sensitivity, selectivity, and reusability. Moreover, we designed and manufactured a sensor paper based on MOF 1 as a portable device for the visual detection of folic acid and sulfaquinoxaline. More crucially, this is the first example in which luminescent MOF is used to identify sulfaquinoxaline molecules in an aqueous solution. In addition, the luminescence sensing mechanisms of MOF 1 for the detection of the above analytes were explored in detail.

Supramolecular Combination Cancer Therapy Based on Macrocyclic Supramolecular Materials

Supramolecular combination therapy adopts supramolecular materials to design intelligent drug delivery systems with different strategies for cancer treatments. Thereinto, macrocyclic supramolecular materials play a crucial role in encapsulating anticancer drugs to improve anticancer efficiency and decrease toxicity towards normal tissue by host-guest interaction. In general, chemotherapy is still common therapy for solid tumors in clinics. However, supramolecular combination therapy can overcome the limitations of the traditional single-drug chemotherapy in the laboratory findings. In this review, we summarized the combination chemotherapy, photothermal chemotherapy, and gene chemotherapy based on macrocyclic supramolecular materials. Finally, the application prospects in supramolecular combination therapy are discussed.

Two cationic iron-based crystalline porous materials for encapsulation and sustained release of 5-fluorouracil

Iron-based crystalline porous materials (CPMs) emerged as a new class of biodegradable and non-toxic materials of high interest for drug delivery systems (DDSs) due to their high loading capacity and controllable structures. This work constructed two kinds of Fe-CPM coordination polymers (CPM-83 and CPM-85) from typical oxo-centered trimers of the iron octahedra cluster [Fe₃O(RCOO)₃(TPT)] with two functional modules. The tri-topic pyridine ligand (TPT) occupied the open metal sites of the trinuclear cluster, precluding the attachment of neutralizing anions, leading to three-dimensional frameworks with a positive charge and higher stability. Moreover, the triazine ligand TPT divides the original columnar channel into small domains, improving the adsorption efficiency and maximizing the host-guest interaction. Hence, the suitable pore size and electrostatic force make the materials highly adsorption selective for the anticancer drug 5-fluorouracil (5-Fu). We show that Fe-CPM-83 and Fe-CPM-85 loaded with 5-Fu are efficient drug delivery vehicles with loading content as high as 60.5 (wt%) and 32.8 (wt%) within 2-5 h of loading time. Simultaneously, their sustained release kinetics can be up to 96 hours with a completely different pH-responsive controlled release. The released content is 77% or 85% for each complex, significantly prolonging the release process and decreasing the plasma concentration. The MTT assay was performed on mouse fibroblasts (L929) to demonstrate the satisfactory biocompatibility of the matrix. This work has momentous research significance and application value for developing novel drug-delivery materials.

Acridine based metal-organic framework host-guest featuring efficient photoelectrochemical-type photodetector and white LED

A novel metal-organic framework (MOF) host-guest material [Cd₃(EtOIPA)₄(HAD)₂]·H₂O has been successfully synthesized by the reaction of 5-ethoxyisophthalic acid (EtOIPA), acridine (AD) and Cd(II) salts under hydrothermal conditions. Structurally, the title MOF possesses a trinucleate Cd(II) based 2D double-layer with the protonated AD cations as the template encapsulated into the grids. The combination of experiments and theoretical calculations reveals that the orderly arrangement of EtOIPA dimers, protonated AD cations and trinucleate Cd(II) clusters generates highly delocalized π-electron channels with a prolonged exciton lifetime. The MOF powders show bright yellow emission with a long lifetime of 50.63 ns. Photoelectrochemical measurements reveal a high photocurrent density ratio of 290 between light and dark conditions at 0 V bias potential, making it a perfect self-driven photodetector. By coating the yellow phosphor on a commercially available blue LED, a high performance white LED with CIE, CCT and CRI values of (0.325, 0.336), 88.2 and 5844 K, respectively can be obtained.

Metal-organic framework as a mimetic enzyme with excellent adaptability for sensitive chemiluminescence detection of glutathione in cell lysate

A novel [Co(L)(H₂O)₂] (1) was obtained by hydrothermal method and it exhibited a 1D chain with exposed carboxyl groups, the unique coordination mode made it have unusual physical and chemical stability. Meanwhile, 1 showed peroxidase-like and weak oxidase-like activity. 1 as a peroxidase mimic enzyme had an excellent affinity for the substrates luminol and H₂O₂. Compared with HRP, 1 had catalytic activity in a wide pH range and showed the best catalytic activity at pH 7.4. Meanwhile, the catalysis process of 1 was reversible and recyclable, and the catalytic activity remained stable after different pH and temperatures and long-time storage. Based on the inhibition of glutathione on luminol-H₂O₂-MOF 1 chemiluminescence signal, a chemiluminescence method for the determination of glutathione has been proposed with high sensitivity and selectivity and had been applied for detecting glutathione in cell lysate with satisfactory results.

Efficient Energy-Transfer-Induced High Photoelectric Conversion in a Dye-Encapsulated Ionic Pyrene-Based Metal-Organic Framework

The relationship between the aggregation states of pyrene-based linkers and the photoluminescence/photoelectric performance was well studied by the formation of an anionic metal-organic framework, [BMI]₂[Mg₃(TBAPy)₂(H₂O)₄]·2dioxane, which shows highly enhanced light-harvesting and photoelectric conversion efficiency by the encapsulation of D-π-A cation dyes.

Anti-inflammatory and antioxidant effects of nanoformulations composed of metal-organic frameworks delivering rutin and/or piperine natural agents

Plant-derived natural medicines have been extensively studied for anti-inflammatory or antioxidant properties, but challenges to their clinical use include low bioavailability, poor solubility in water, and difficult-to-control release kinetics. Nanomedicine may offer innovative solutions that can enhance the therapeutic activity and control release kinetics of these agents, opening the way to translating them into the clinic. Two agents of particular interest are rutin (Ru), a flavonoid, and piperine (Pip), an alkaloid, which exhibit a range of pharmacological activities that include antioxidant and anti-inflammatory effects. In this work, nanoformulations were developed consisting of two metal–organic frameworks (MOFs) with surface modifications, Ti-MOF and Zr-MOF, each of them loaded with Ru and/or Pip. Both MOFs and nanoformulations were characterized and evaluated in vivo for anti-inflammatory and antioxidant effects. Loadings of ∼17 wt.% for a single pro-drug and ∼27 wt.% for dual loading were achieved. The release patterns for Ru and or Pip followed two stages: a zero-order for the first 12-hour stage, and a second stage of stable sustained release. At pH 7.4, the release patterns best fit to zero-order and Korsmeyer–Peppas kinetic models. The nanoformulations had enhanced anti-inflammatory and antioxidant effects than any of their elements singly, and those with Ru or Pip alone showed stronger effects than those with both agents. Results of assays using a paw edema model, leukocyte migration, and plasma antioxidant capacity were in agreement. Our preliminary findings indicate that nanoformulations with these agents exert better anti-inflammatory and antioxidant effects than the agents in their free form.

Stimuli-responsive nanocarriers for therapeutic applications in cancer

Cancer has become a very serious challenge with aging of the human population. Advances in nanotechnology have provided new perspectives in the treatment of cancer. Through the combination of nanotechnology and therapeutics, nanomedicine has been successfully used to treat cancer in recent years. In terms of nanomedicine, nanocarriers play a key role in delivering therapeutic agents, reducing severe side effects, simplifying the administration scheme, and improving therapeutic efficacies. Modulations of the structure and function of nanocarriers for improved therapeutic efficacy in cancer have attracted increasing attention in recent years. Stimuli-responsive nanocarriers penetrate deeply into tissues and respond to external or internal stimuli by releasing the therapeutic agent for cancer therapy. Notably, stimuli-responsive nanocarriers reduce the severe side effects of therapeutic agents, when compared with systemic chemotherapy, and achieve controlled drug release at tumor sites. Therefore, the development of stimuli-responsive nanocarriers plays a crucial role in drug delivery for cancer therapy. This article focuses on the development of nanomaterials with stimuli-responsive properties for use as nanocarriers, in the last few decades. These nanocarriers are more effective at delivering the therapeutic agent under the control of external or internal stimuli. Furthermore, nanocarriers with theranostic features have been designed and fabricated to confirm their great potential in achieving effective treatment of cancer, which will provide us with better choices for cancer therapy.

Pyrene-based metal organic frameworks: from synthesis to applications

Pyrene is one of the most widely investigated aromatic hydrocarbons given to its unique optical and electronic properties. Hence, pyrene-based ligands have been attractive for the synthesis of metal-organic frameworks (MOFs) in the last few years. In this review, we will focus on the most important characteristics of pyrene, in addition to the development and synthesis of pyrene-based molecules as bridging ligands to be used in MOF structures. We will summarize the synthesis attempts, as well as the post-synthetic modifications of pyrene-based MOFs by the incorporation of metals or ligands in the structure. The discussion of promising results of such MOFs in several applications; including luminescence, photocatalysis, adsorption and separation, heterogeneous catalysis, electrochemical applications and bio-medical applications will be highlighted. Finally, some insights and future prospects will be given based on the studies discussed in the review. This review will pave the way for the researchers in the field for the design and development of novel pyrene-based structures and their utilization for different applications.

Smart metal organic frameworks: focus on cancer treatment

Metal–organic frameworks (MOFs), as a prominent category of hybrid porous materials, have been broadly employed as controlled systems of drug delivery due to their inherent interesting properties.

Distinct and Selective Amine- and Anion-Responsive Behaviors of an Electron-Deficient and Anion-Exchangeable Metal-Organic Framework

Smart materials that respond to chemical stimuli with color or luminescence changes are highly desirable for daily-life and high-tech applications. Here, we report a novel porous metal-organic framework (MOF) that shows multiple, selective, and discriminative responsive properties owing to the combination of different functional ingredients [tripyridinium chromogen, Eu(III) luminophore, cationic framework, and special porous structure]. The MOF contains two interpenetrated three-dimensional cationic coordination networks built of a tetrahedral [Eu₄(μ₃-OH)₄] cluster and a tripyridinium-tricarboxylate zwitterionic linker. It shows reversible and discriminative chromic response to aliphatic amines and aniline through different host-guest interactions between electron-deficient pyridinium and electron-rich amines. The size- and shape-selective response to aliphatic amines is ascribed to the radical formation through host-guest electron transfer, whereas the response to aniline is ascribed to the formation of sandwich-type acceptor-donor-acceptor complexes. The MOF is capable of reversible anion exchange with various anions and shows selective and discriminative ionochromic response to iodide, bromide, and thiocyanate, which is attributed to charge-transfer complexation. The above chromic behaviors are accompanied by efficient quenching of Eu(III) photoluminescence. The MOF represents a multi-stimuli dual-output responsive system. It can be used for discrimination and identification of anions and amines. The potential use in invisible printing, reusable sensory films, and optical switches was demonstrated by the ink and the membrane made of the MOF and organic polymers.