Evaluation of drug loading capabilities of γ-cyclodextrin-metal organic frameworks by high performance liquid chromatography

Cyclodextrin in drug delivery: Exploring scaffolds, properties, and cutting-edge applications

Cyclodextrins (CDs) are unique cyclic compounds that can form inclusion complexes via host-guest complexation with a wide range of molecules, thereby altering their physicochemical properties. These molecules offer the formation of inclusion complexes without the formation of covalent bonds, making them suitable for a variety of applications in pharmaceutical and biomedical fields. Due to their supramolecular host-guest properties, CDs are being utilized in the fabrication of biomaterials, metal-organic frameworks, and nano-drug carriers. Additionally, CDs in combination with biomolecules are biocompatible and can deliver nano to macromolecules at the site of drug actions. However, the availability of free hydroxyl groups and a simple crosslinking process for supramolecular fabrication show immense opportunities for researchers in the field of tissue engineering and biomedical applications. In this review article, we have covered the historical development, various types of chemical frameworks, unique chemical and physical properties, and important applications of CDs in drug delivery and biomedical sciences.

Cyclodextrin-based metal-organic frameworks transforming drug delivery

Cyclodextrin-based metal-organic frameworks (CD-MOFs) are gaining traction in the realm of drug delivery due to their inherent versatility and potential to amplify drug efficacy, specificity, and safety. This article explores the predominant preparation techniques for CD-MOFs, encompassing methods like vapor diffusion, microwave-assisted, and ultrasound hydrothermal approaches. Native CD-MOFs present compelling advantages in drug delivery applications. They can enhance drug loading capacity, stability, solubility, and bioavailability by engaging in diverse interactions with drugs, including host-guest, hydrogen bonding, and electrostatic interactions. Beyond their inherent properties, CD-MOFs can be customized as drug carriers through two primary strategies: co-crystallization with functional components and surface post-modifications. These tailored modifications pave the way for controlled release manners. They allow for slow and sustained drug release, as well as responsive releases triggered by various factors such as pH levels, glutathione concentrations, or specific cations. Furthermore, CD-MOFs facilitate targeted delivery strategies, like pulmonary or laryngeal delivery, enhancing drug delivery precision. Overall, the adaptability and modifiability of CD-MOFs underscore their potential as a versatile platform for drug delivery, presenting tailored solutions that cater to diverse biomedical and industrial needs.

Thrombotic microenvironment responsive crosslinking cyclodextrin metal-organic framework nanocarriers for precise targeting and thrombolysis

Global public health is seriously threatened by thrombotic disorders because of their high rates of mortality and disability. Most thrombolytic agents, especially protein-based pharmaceuticals, have a short half-life in circulation, reducing their effectiveness in thrombolysis. The creation of an intelligent drug delivery system that delivers medication precisely and releases it under regulated conditions at nearby thrombus sites is essential for effective thrombolysis. In this article, we present a unique medication delivery system (MCRUA) that selectively targets platelets and releases drugs by stimulation from the thrombus' microenvironment. The thrombolytic enzyme urokinase-type plasminogen-activator (uPA) and the anti-inflammatory medication Aspirin (acetylsalicylic acid, ASA) are both loaded onto pH-sensitive CaCO3/cyclodextrin crosslinking metal-organic frameworks (MC) that make up the MCRUA system. c(RGD) is functionalized on the surface of MC, which is functionalized by RGD to an esterification reaction. Additionally, the thrombus site's acidic microenvironment causes MCRUA to disintegrate to release uPA for thrombolysis and aiding in vessel recanalization. Moreover, cyclodextrin-encapsulated ASA enables the treatment of the inflammatory environment within the thrombus, enhancing the antiplatelet aggregation effects and promoting cooperative thrombolysis therapy. When used for thrombotic disorders, our drug delivery system (MCRUA) promotes thrombolysis, suppresses rethrombosis, and enhances biosafety with fewer hemorrhagic side effects.

β-Cyclodextrin metal-organic framework as a green carrier to improve the dissolution, bioavailability, and liver protective effect of luteolin

The incidence of acetaminophen-induced liver injury has increased, but effective prevention methods are limited. Although luteolin has hepatoprotective activity, its low solubility and bioavailability limit its applications. Cyclodextrin metal-organic frameworks (CD-MOFs) possess 3D-network structures and large inner cavities, which make them excellent carriers of poorly soluble drugs. In this study, we used CD-MOFs as carriers to improve the dissolution of luteolin and assessed their antioxidant activity, bioavailability, and hepatoprotective effects. Luteolin was loaded into β-CD-MOF, γ-CD-MOF, β-CD, and γ-CD, and characterized by powder X-ray diffractometry (PXRD) and thermogravimetric analysis (TGA). Our results showed that luteolin-β-CD-MOF was the most stable. The main driving forces were hydrogen bonds and van der Waals forces, as determined by molecular simulation. The loading capacity of luteolin-β-CD-MOF was 14.67 wt%. Compared to raw luteolin, luteolin-β-CD-MOF exhibited a 4.50-fold increase in dissolution and increased antioxidant activity in vitro. Luteolin-β-CD-MOF increased the bioavailability of luteolin by approximately 4.04- and 11.07-fold in healthy rats and liver injured rats induced by acetaminophen in vivo, respectively. As determined by biochemical analysis, luteolin-β-CD-MOF exhibited a better hepatoprotective effect than raw luteolin in rats with acetaminophen-induced liver injury. This study provides a new approach for preventing acetaminophen-mediated liver damage.

Building respirable powder architectures: utilizing polysaccharides for precise control of particle morphology for enhanced pulmonary drug delivery

INTRODUCTION

Dry powder inhaler (DPI) formulations are gaining attention as universal formulations with applications in a diverse range of drug formulations. The practical application of DPIs to pulmonary drugs requires enhancing their delivery efficiency to the target sites for various treatment modalities. Previous reviews have not explored the relation between particle morphology and delivery to different pulmonary regions. This review introduces new approaches to improve targeted DPI delivery using novel particle design such as supraparticles and metal-organic frameworks based on cyclodextrin.

AREAS COVERED

This review focuses on the design of DPI formulations using polysaccharides, promising excipients not yet approved by regulatory agencies. These excipients can be used to design various particle morphologies by controlling their physicochemical properties and manufacturing methods.

EXPERT OPINION

Challenges associated with DPI formulations include poor access to the lungs and low delivery efficiency to target sites in the lung. The restricted applicability of typical excipients contributes to their limited use. However, new formulations based on polysaccharides are expected to establish a technological foundation for the development of DPIs capable of delivering modalities specific to different lung target sites, thereby enhancing drug delivery.

Cyclodextrin MOFs modified dry powder inhalers quadruple bioavailability of luteolin to ameliorate fibrosing interstitial lung disease

Fibrosing interstitial lung disease (ILD) is a pathological condition that is highly heterogeneous and lethal, and has few effective treatment choices. Other than pirfenidone and nintedanib for the therapy of idiopathic pulmonary fibrosis, no medications are currently licensed for the treatment of ILD. Luteolin is a common flavonoid with multiple biological effects such as anti-inflammation but with poor solubility and absorption. In this study, we loaded luteolin into γ-cyclodextrin metal-organic frameworks (CD-MOFs) to deliver the medicine to the lungs using dry powder inhalers; in vitro pulmonary deposition results showed LUT@CDMOF had a high fine particle fraction (FPF) (59.77 ± 3.48%). LUT@CDMOF effectively inhibited ILD progression in the BLM-induced fibrosing ILD model rats. When compared to oral administration, the inhalation of LUT@CDMOF dry powder in rats showed considerable improvements in absorption and bioavailability, with a tmax of 0.08 h and a high absolute bioavailability (82%) of LUT (The AUC(0-t) and Cmax of inhal. LUT@CDMOF respectively increased about 4.03 times and 9.11 times, when compared with the i.g. LUT group). These studies demonstrate the potent anti-inflammatory activities of LUT@CDMOF. The inhaled LUT@CDMOF might be considered as a promising new strategy in the treatment of fibrosing ILD.

Cyclodextrin-metal-organic frameworks in molecular delivery, detection, separation, and capture: An updated critical review

Metal-organic frameworks (MOFs) are coordination compounds with tuneable structures and controllable functions. However, the biological toxicity of traditional MOFs materials is often inevitable, making their application in the biological field have many limitations. Therefore, frontier research increasingly focuses on developing biocompatible MOFs materials. Cyclodextrins (CDs), derived from starch, are favored by various biomaterials due to their good biosafety and are often seen in the preparation and application of MOFs materials. This review describes the features of MOFs materials, and the various preparation methods of CD-MOFs are analyzed in detail from the perspective of CD classification. Additionally, the promising applications of CD-MOFs materials for delivery, detection, separation, and capture of active molecules in recent studies are systematically discussed and summarized. In terms of safety, the CD-MOFs materials are meticulously summarized. Finally, this review presents the challenges and future prospects regarding the current CD-MOFs-based materials, which will shed new light on the application of such materials in various fields.

Cyclodextrin metal-organic frameworks and derivatives: recent developments and applications

While there is a tremendous amount of scientific research on metal organic frameworks (MOFs) for gas storage/separation, catalysis and energy storage, the development and application of biocompatible MOFs still poses major challenges. In general, they can be synthesised from various biocompatible linkers and metal ions but particularly cyclodextrins (CDs) as cyclic oligosaccharides are an astute choice for the former. Although the field of CD-MOF materials is still in the early stages and their design and fabrication comes with many hurdles, the benefits coming from CDs built in a porous framework are exciting. Versatile host-guest complexation abilities, high encapsulation capacity and hydrophilicity are among the valuable properties inherent to CDs and offer extended and novel applications to MOFs. In this review, we provide an overview of the state-of-the-art synthesis, design, properties and applications of these materials. Initially, a rationale for the preparation of CD-based MOFs is provided, based on the chemical and structural properties of CDs and including their advantages and disadvantages. Further on, the review exhaustively surveys CD-MOF based materials by categorising them into three sub-classes, namely (i) CD-MOFs, (ii) CD-MOF hybrids, obtained via combination with external materials, and (iii) CD-MOF-derived materials prepared under pyrolytic conditions. Subsequently, CD-based MOFs in practical applications, such as drug delivery and cancer therapy, sensors, gas storage, (enantiomer) separations, electrical devices, food industry, and agriculture, are discussed. We conclude by summarizing the state of the art in the field and highlighting some promising future developments of CD-MOFs.

The Emerging Role of Cyclodextrin Metal–Organic Frameworks in Ostheotherapeutics

Metal–Organic Frameworks (MOFs) are a class of coordination compounds with high versatility of design and a high loading ability. These properties have made them increasingly attractive for drug delivery, with research focusing mostly on the preparation of biocompatible MOFs. A suitable strategy is the use of cyclodextrins, cyclic oligosaccharides with excellent biosafety profiles. This review summarises the early steps taken in the application of cyclodextrin-coated and cyclodextrin-based MOFs in the treatment of bone-related diseases divided into three categories: cyclodextrin-coated MOFs, cyclodextrin-based MOFs and cross-linked derivatives of CD-MOFs. Applications in the delivery of bisphosphonates, osteoporotic regulating drugs and non-steroidal anti-inflammatory drugs, for osteoarthritis management, are highlighted. Lastly, the use of these materials in dentistry is exemplified with a recent report.

A γ-cyclodextrin-based metal-organic framework (γ-CD-MOF): a review of recent advances for drug delivery application

The relatively new class of porous material known as metal-organic framework (MOF) exhibits unique features such as high specific surface area, controlled porosity and high chemical stability. Many green synthesis approaches for MOFs have been proposed using biocompatible metal ions and linkers to maximise their use in pharmaceutical fields. The involvement of biomolecules as an organic ligand can act promising because of their biocompatibility. Recently, cyclodextrin metal-organic frameworks (CD-MOFs) represent environmentally friendly and biocompatible characteristics that lead them to biomedical applications. They are regarded as a promising nanocarrier for drug delivery, due to their high specific surface area, high porosity, tuneable chemical structure, and easy fabrication. This review focuses on the unique properties of CD-MOF and the recent advances in methods for the synthesis of these porous structures with emphasis on particle size. Then, the state-of-the-art drug delivery systems with various drugs along with the performance of CD-MOFs as efficient drug delivery systems are presented. Particular emphasis is laid on researches investigating the drug delivery potential of γ-CD-MOF.

Cross-linked γ-cyclodextrin metal-organic framework-a new stationary phase for the separations of benzene series and polycyclic aromatic hydrocarbons

The cross-linked γ-cyclodextrin metal-organic framework (CL-CD-MOF) was synthesized by crosslinking γ-cyclodextrin metal-organic framework (γ-CD-MOF) with diphenyl carbonate to separate benzene series and polycyclic aromatic hydrocarbons (PAHs). The separation ability of the CL-CD-MOF packed column was assessed in both reverse-phase (RP-) and normal-phase (NP-) modes. The retention mechanisms of these compounds were discussed and confirmed by combining molecular simulations in detail. It was found that baseline separation could be obtained in RP-HPLC mode and it was superior to commercial C18 column in separating xylene isomers. The interaction between CL-CD-MOF and analytes, such as dipole-dipole interaction, π-electron transfer interaction, hydrophobic interaction, and van der Waals force, may dominate the chromatographic separation, and CL-CD-MOF column had a certain shape recognition ability. In addition, the composition of the mobile phase also had a crucial effect. Moreover, the column demonstrated satisfactory stability and repeatability (the relative standard deviations of retention time, peak height, peak area, and half peak width for six replicate separations of the tested analytes were within the ranges 0.17-1.1%, 0.96-1.9%, 0.23-1.7%, and 0.32-1.9%, respectively) and there was no significant change in the separation efficiency for at least 3 years of use. Thermodynamic characteristics indicated that the process of separations on the CL-CD-MOF column was both negative enthalpy change (ΔH) and entropy change (ΔS) controlled. The excellent performance made CL-CD-MOF a promising HPLC stationary phase material for separation and determination of benzene series and PAHs.

Noncovalent Complexes of Cyclodextrin with Small Organic Molecules: Applications and Insights into Host-Guest Interactions in the Gas Phase and Condensed Phase

Cyclodextrins (CDs) have drawn a lot of attention from the scientific communities as a model system for host–guest chemistry and also due to its variety of applications in the pharmaceutical, cosmetic, food, textile, separation science, and essential oil industries. The formation of the inclusion complexes enables these applications in the condensed phases, which have been confirmed by nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and other methodologies. The advent of soft ionization techniques that can transfer the solution-phase noncovalent complexes to the gas phase has allowed for extensive examination of these complexes and provides valuable insight into the principles governing the formation of gaseous noncovalent complexes. As for the CDs’ host–guest chemistry in the gas phase, there has been a controversial issue as to whether noncovalent complexes are inclusion conformers reflecting the solution-phase structure of the complex or not. In this review, the basic principles governing CD’s host–guest complex formation will be described. Applications and structures of CDs in the condensed phases will also be presented. More importantly, the experimental and theoretical evidence supporting the two opposing views for the CD–guest structures in the gas phase will be intensively reviewed. These include data obtained via mass spectrometry, ion mobility measurements, infrared multiphoton dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations.

Recent progress in the synthesis, structural diversity and emerging applications of cyclodextrin-based metal-organic frameworks

Inorganic-organic hybrid materials, especially metal-organic frameworks (MOFs) composed of metals and organic linkers, have emerged as a new class of versatile materials owing to their tunable structure and controllable functionality. As typical biocompatible MOFs, cyclic oligosaccharide cyclodextrin-based carbohydrate metal-organic frameworks (CD-MOFs) have recently attracted considerable attention due to their edible, renewable and biodegradable nature. Herein, we focus on the latest advances concerning these materials. First, the synthesis methods and structural diversity of CD-MOFs are introduced and summarized. Besides, the synthetic strategies of moisture-resistant CD-MOFs are also emphasized. Moreover, their applications, including gas adsorption, separation, sensing, memristor fabrication, as templates in nanoparticle synthesis, light emission and especially drug delivery, are systematically discussed and highlighted. Finally, to conclude the review, some insights and current challenges that need to be addressed for the further development of these materials are proposed. We anticipate that this review will result in a better understanding of CD-MOFs and will help maximize the potential functions of these materials.

Adsorption of CO2 on amine-functionalized green metal-organic framework: an interaction between amine and CO2 molecules

The efficient capture of CO₂ is a critical problem for porous adsorbents. The inadequacy of conventional adsorbents has low adsorption capacity towards CO₂ removal. Metal organic frame work has been considered as very effective for CO₂ adsorption as it shows higher rate of CO₂ adsorption at room temperature. In conventional amine processes, a comparatively high energy penalty is required, whereas a novel class of metal-organic framework by the combination of amine solvent have improve the potential of adsorption process and also the efficiency of separation. Amine-functionalized MOFs become more fascinated due to strong interaction between carbon dioxide and amine-functionalized MOF. A renewable green γCD-MOF was synthesized by using vapor diffusion method. Post-synthetic modification of γCD-MOF was done with piperazine and analyzed to expose its crystalline structure, morphology, and porous structure. The main aim of this paper is to enhance the CO₂ adsorption by functionalization of inexpensive, green, nanoporous γCD-MOF and also to highlight the effects of amine-based functionalization towards potential application. Gravimetric CO₂ adsorption isotherms for γCD-MOF, pip-γCD-MOF are reported up to 60 °C and found to follow a pseudo-second-order reaction. The pip-γCD-MOF confirms comparatively increased rapid adsorption rate of CO₂ than that of γCD-MOF and desorption of CO₂, and need less energy for regeneration. These results are the complete evidence of piperazine as an efficient amine group for increasing the CO₂ adsorption uptake capacity.

Metal-Organic Frameworks in Green Analytical Chemistry

Metal-organic frameworks (MOFs) are porous hybrid materials composed of metal ions and organic linkers, characterized by their crystallinity and by the highest known surface areas. MOFs structures present accessible cages, tunnels and modifiable pores, together with adequate mechanical and thermal stability. Their outstanding properties have led to their recognition as revolutionary materials in recent years. Analytical chemistry has also benefited from the potential of MOF applications. MOFs succeed as sorbent materials in extraction and microextraction procedures, as sensors, and as stationary or pseudo-stationary phases in chromatographic systems. To date, around 100 different MOFs form part of those analytical applications. This review intends to give an overview on the use of MOFs in analytical chemistry in recent years (2017–2019) within the framework of green analytical chemistry requirements, with a particular emphasis on possible toxicity issues of neat MOFs and trends to ensure green approaches in their preparation.

MOF Capacitates Cyclodextrin to Mega-Load Mode for High-Efficient Delivery of Valsartan

PURPOSE

To investigate the mechanism of enhancing solubility and bioavailability of water-insoluble drug, valsartan (VAL), with being mega-loaded by cyclodextrin metal organic framework (CD-MOF).

METHODS

VAL was successfully mega-loaded into CD-MOF by magnetic agitation of VAL in ethanolic solution. Characterizations including powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), synchrotron radiation-based Fourier transform-infrared spectroscopy (SR-FTIR) ¹³C solid-state nuclear magnetic resonance spectroscopy ( ¹³C SS-NMR), nitrogen gas adsorption, and small-angle X-ray scattering (SAXS) were carried out to confirm the mechanism and incorporation behavior of VAL in CD-MOF. Ball milling process combined with molecular modeling was also used to confirm the mechanism. Improvement of bioavailability in vivo was confirmed by pharmacokinetic experiment in beagles.

RESULTS

As a carrier with payload 150% higher than conventional CD complexation, CD-MOF included molecules of VAL as complexations in the chambers of (γ-CD)₂, and nanoclusters in the confined spherical cages of (γ-CD)₆ confirmed by SAXS and ¹³C SS-NMR. Ball milling combined with molecular modeling inferred that the reduced release rate of the milled CD-MOF with ultrahigh drug payload was mainly due to the partial aggregation of the VAL nanoclusters. The molecules of VAL as nanoclusters in the cages of (γ-CD)₆ are critical in dramatically improving the apparent solubility (39.5-fold) and oral bioavailability (1.9-fold) of VAL in contrast to γ-CD inclusion.

CONCLUSIONS

The new understanding of drug nanoclusters in CD-MOF will help to design more efficient drug delivery systems using CD-MOF carrier with nanocavities.

Fabrication of Carboxymethylcellulose/Metal-Organic Framework Beads for Removal of Pb(II) from Aqueous Solution

The ability to remove toxic heavy metals, such as Pb(II), from the environment is an important objective from both human-health and ecological perspectives. Herein, we describe the fabrication of a novel carboxymethylcellulose-coated metal organic material (MOF-5⁻CMC) adsorbent that removed lead ions from aqueous solutions. The adsorption material was characterized by Fourier-transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and X-ray photoelectron spectroscopy. We studied the functions of the contact time, pH, the original concentration of the Pb(II) solution, and adsorption temperature on adsorption capacity. MOF-5⁻CMC beads exhibit good adsorption performance; the maximum adsorption capacity obtained from the Langmuir isotherm-model is 322.58 mg/g, and the adsorption equilibrium was reached in 120 min at a concentration of 300 mg/L. The adsorption kinetics is well described by pseudo-second-order kinetics, and the adsorption equilibrium data are well fitted to the Langmuir isotherm model (R² = 0.988). Thermodynamics experiments indicate that the adsorption process is both spontaneous and endothermic. In addition, the adsorbent is reusable. We conclude that MOF-5⁻CMC is a good adsorbent that can be used to remove Pb(II) from aqueous solutions.

Inverse Adsorption Separation of CO2/C2H2 Mixture in Cyclodextrin-Based Metal-Organic Frameworks

The demand for CO₂/C₂H₂ separation, especially the removal of CO₂ impurity, continues to grow because of the high-purity C₂H₂ required for various industrial applications. The adsorption separation of C₂H₂ and CO₂ via porous materials is gaining a considerable attention as it is more energy-efficient compared with cryogenic distillation. The ideal porous materials are those that preferentially adsorb CO₂ over C₂H₂; however, very few adsorbents meet such requirement. Herein, two isostructural cyclodextrin-based CD-MOFs (CD-MOF-1 and CD-MOF-2) were demonstrated to have an inverse ability to selectively capture CO₂ from C₂H₂ by single-component adsorption isotherms and dynamic breakthrough experiments. These two MOFs showed excellent adsorption capacity and benchmark selectivity (118.7) for CO₂/C₂H₂ mixture at room temperature, enabling the pure C₂H₂ to be obtained in only one step. This work revealed that these materials were promising adsorbents for obtaining high-purity C₂H₂ via selectively capturing CO₂ from C₂H₂.

Characterization and Mechanisms of Novel Emulsions and Nanoemulsion Gels Stabilized by Edible Cyclodextrin-Based Metal-Organic Frameworks and Glycyrrhizic Acid

In this study, a novel emulsion stabilized by nano-cyclodextrin-based metal-organic frameworks and glycyrrhizic acid (CD-MOF/GA) was successfully fabricated, exhibiting long-term storage stability. The characterization and mechanisms for the emulsion formation with CD-MOF/GA were studied. The phase change of the emulsions from sol to gel could be controlled using different oil fractions and mass ratios of CD-MOF and GA. The rheological results showed that the emulsions were transformed from liquid emulsions to emulsion gels when the oil fractions were higher than 0.3 and the mass ratio of CD-MOF and GA was 1:3. The low-field nuclear magnetic resonance results revealed that the T₂₂ relaxation time of emulsions decreased from 403.702 to 231.013 ms when the oil fractions increased from 0.1 to 0.6, indicating that movable water was converted to constructal water. The emulsions showed good stability, even in high-alkaline pH and high-temperature conditions.

Drug nanoclusters formed in confined nano-cages of CD-MOF: dramatic enhancement of solubility and bioavailability of azilsartan

Tremendous efforts have been devoted to the enhancement of drug solubility using nanotechnologies, but few of them are capable to produce drug particles with sizes less than a few nanometers. This challenge has been addressed here by using biocompatible versatile γ-cyclodextrin (γ-CD) metal-organic framework (CD-MOF) large molecular cages in which azilsartan (AZL) was successfully confined producing clusters in the nanometer range. This strategy allowed to improve the bioavailability of AZL in Sprague-Dawley rats by 9.7-fold after loading into CD-MOF. The apparent solubility of AZL/CD-MOF was enhanced by 340-fold when compared to the pure drug. Based on molecular modeling, a dual molecular mechanism of nanoclusterization and complexation of AZL inside the CD-MOF cages was proposed, which was confirmed by small angle X-ray scattering (SAXS) and synchrotron radiation-Fourier transform infrared spectroscopy (SR-FTIR) techniques. In a typical cage-like unit of CD-MOF, three molecules of AZL were included by the γ-CD pairs, whilst other three AZL molecules formed a nanocluster inside the 1.7 nm sized cavity surrounded by six γ-CDs. This research demonstrates a dual molecular mechanism of complexation and nanoclusterization in CD-MOF leading to significant improvement in the bioavailability of insoluble drugs.

Cyclodextrin-Based Metal-Organic Frameworks (CD-MOFs) in Pharmaceutics and Biomedicine

Metal-organic frameworks (MOFs) show promising application in biomedicine and pharmaceutics owing to their extraordinarily high surface area, tunable pore size, and adjustable internal surface properties. However, MOFs are prepared from non-renewable or toxic materials, which limit their real-world applications. Cyclodextrins (CDs) are a typical natural and biodegradable cyclic oligosaccharide and are primarily used to enhance the aqueous solubility, safety, and bioavailability of drugs by virtue of its low toxicity and highly flexible structure, offering a peculiar ability to form CD/drug inclusions. A sophisticated strategy where CD is deployed as a ligand to form an assembly of cyclodextrin-based MOFs (CD-MOFs) may overcome real-world application drawbacks of MOFs. CD-MOFs incorporate the porous features of MOFs and the encapsulation capability of CD for drug molecules, leading to outstanding properties when compared with traditional hybrid materials. This review focuses on the inclusion technology and drug delivery properties associated with CD-MOFs. In addition, synthetic strategies and currently developed uses of CD-MOFs are highlighted as well. Also, perspectives and future challenges in this rapidly developing research area are discussed.

Novel Approach with Controlled Nucleation and Growth for Green Synthesis of Size-Controlled Cyclodextrin-Based Metal-Organic Frameworks Based on Short-Chain Starch Nanoparticles

In this study, the nano- and microsized cyclodextrin-based metal-organic frameworks (CD-MOFs) were successfully conducted using short-chain starch nanoparticles as seeds through the seed-mediated method. The morphology, size, crystal structure, thermal, and N₂ adsorption properties of CD-MOFs prepared at different time intervals were investigated. The scanning electron microscopy results showed that the size variation from nanometer to millimeter could be controlled by crystal growth time. The CD-MOFs based on short-chain starch nanoparticle had higher crystallinity and N₂ uptake, thus indicating that the method of seed-mediated was more facile and efficient than the previous approach. Resveratrol (Res) is a natural polyphenol compound that has anticancer and antimicrobial activities against several pathogens. However, this compound suffers from poor stability. trans-Res rapidly isomerizes when exposed under ultraviolet or visible light. The results showed that the stability of Res was substantially enhanced by its encapsulation in CD-MOF crystals.

Green Synthesis of Cyclodextrin-Based Metal-Organic Frameworks through the Seed-Mediated Method for the Encapsulation of Hydrophobic Molecules

Metal-organic frameworks (MOFs) are attracting considerable attention as a result of their unique structural properties, such as a high surface area, highly porous topology, and tunable size and shape, which enable them to have potential applications as a new class of carriers for functional agent or drug delivery. However, most of the MOFs and the polymers used are not pharmaceutically acceptable. For the first time, this study successfully conducted the rapid synthesis of cyclodextrin metal-organic frameworks (CD-MOFs) through a facile and green seed-mediated method. The size control, crystal structure, and thermal properties of CD-MOFs with and without seeds were investigated. When 1 mg/mL seed was added, the size of γ-CD-MOF crystals decreased from 6.2 ± 0.8 to 1.8 ± 0.4 μm. The CD-MOFs synthesized though the seed-mediated method had higher crystallinity and thermal stability than those that were not. Furthermore, the CD-MOFs could encapsulate hydrophobic molecules, such as Nile red (NR), which was chosen as a model, and the interaction mechanism between γ-CD-MOFs and NR was investigated. Results showed the formation of a 1:1 complex between NR and CD-MOFs, demonstrating the potential of these polymers as carriers for hydrophobic drug delivery applications.

γ-Cyclodextrin metal–organic framework for efficient separation of chiral aromatic alcohols

A γ-cyclodextrin metal–organic framework was applied as an efficient chiral stationary phase for HPLC separation of chiral aromatic alcohols.