Recent advances in Metal-Organic Frameworks as nanocarriers for triggered release of anticancer drugs: Brief history, biomedical applications, challenges and future perspective

Metal-Organic Frameworks (MOFs) have emerged as a promising biomedical material due to its unique features such as high surface area, pore volume, variable pore size, flexible functional groups, and excellent efficiency for drug loading. In this review, we explored the use of novel and smart metal organic frameworks as drug delivery vehicles to discover a safer and more controlled mode of drug release aiming to minimize their side effects. Here, we systematically discussed the background of MOFs following a thorough review on structural and physical properties of MOFs, their synthesis techniques, and the important characteristics to establish a strong foundation for future research. Furthermore, the current status on the potential applications of MOF-based stimuli-responsive drug delivery systems, including pH-, ion-, temperature-, light-, and multiple responsive systems for the delivery of anticancer drugs has also been presented. Lastly, we discuss the prospects and challenges in implementation of MOF-based materials in the drug delivery. Therefore, this review will help researchers working in the relevant fields to enhance their understanding of MOFs for encapsulation of various drugs as well as their stimuli responsive mechanism.

A chiral metal-organic framework {(HQA)(ZnCl2)(2.5H2O)}n for the enantioseparation of chiral amino acids and drugs

Chiral metal-organic frameworks (CMOFs) with enantiomeric subunits have been employed in chiral chemistry. In this study, a CMOF formed from 6-methoxyl-(8S,9R)-cinchonan-9-ol-3-carboxylic acid (HQA) and ZnCl₂, {(HQA)(ZnCl₂)(2.5H₂O)}_n, was constructed as a chiral stationary phase (CSP) via an in situ fabrication approach and used for chiral amino acid and drug analyses for the first time. The {(HQA)(ZnCl₂)(2.5H₂O)}_n nanocrystal and the corresponding chiral stationary phase were systematically characterised using a series of analytical techniques including scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, circular dichroism, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller surface area measurements. In open-tubular capillary electrochromatography (CEC), the novel chiral column exhibited strong and broad enantioselectivity toward a variety of chiral analytes, including 19 racemic dansyl amino acids and several model chiral drugs (both acidic and basic). The chiral CEC conditions were optimised, and the enantioseparation mechanisms are discussed. This study not only introduces a new high-efficiency member of the MOF-type CSP family but also demonstrates the potential of improving the enantioselectivities of traditional chiral recognition reagents by fully using the inherent characteristics of porous organic frameworks.

Improving the genistein oral bioavailability via its formulation into the metal-organic framework MIL-100(Fe)

Despite the interesting chemopreventive, antioxidant and antiangiogenic effects of the natural bioflavonoid genistein (GEN), its low aqueous solubility and bioavailability make it necessary to administer it using a suitable drug carrier system. Nanometric porous metal-organic frameworks (nanoMOFs) are appealing systems for drug delivery. Particularly, mesoporous MIL-100(Fe) possesses a variety of interesting features related to its composition and structure, which make it an excellent candidate to be used as a drug nanocarrier (highly porous, biocompatible, can be synthesized as homogenous and stable nanoparticles (NPs), etc.). In this study, GEN was entrapped via simple impregnation in MIL-100 NPs achieving remarkable drug loading (27.1 wt%). A combination of experimental and computing techniques was used to achieve a deep understanding of the encapsulation of GEN in MIL-100 nanoMOF. Subsequently, GEN delivery studies were carried out under simulated physiological conditions, showing on the whole a sustained GEN release for 3 days. Initial pharmacokinetic and biodistribution studies were also carried out upon the oral administration of the GEN@MIL-100 NPs in a mouse model, evidencing a higher bioavailability and showing that this oral nanoformulation appears to be very promising. To the best of our knowledge, the GEN-loaded MIL-100 will be the first antitumor oral formulation based on nanoMOFs studied in vivo, and paves the way to the efficient delivery of nontoxic antitumorals via a convenient oral route.

Immobilization of cellulase on monolith supported with Zr(IV)-based metal-organic framework as chiral stationary phase for enantioseparation of five basic drugs in capillary electrochromatography

Metal-organic framework (UiO-66-NH₂)-incorporated organic polymer monolith was prepared by thermal polymerization. By virtue of the superior physical and chemical properties, the UiO-66-NH₂-modified organic monolith was then functionalized by chiral selector cellulase via the condensation reaction between the primary amino groups and aldehyde groups. The synthesized materials were characterized by Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectrometry, thermogravimetric analysis, and nitrogen sorption isotherm. The cellulase@poly(glycidyl methacrylate-UiO-66-NH₂-ethylene glycol dimethacrylate) (cellulase@poly(GMA-UiO-66-NH₂-EDMA)) monolith was applied to enantiomerically separate the basic racemic forms of metoprolol, atenolol, esmolol, bisoprolol, and propranolol. In contrast to the cellulase@poly(GMA-co-EDMA) monolith without UiO-66-NH₂, the cellulase@poly(GMA-UiO-66-NH₂-EDMA) monolith reveals significantly improved enantiodiscrimination performance for metoprolol (Rs: 0 → 1.67), atenolol (Rs: 0 → 1.50), esmolol (Rs: 0 → 1.52), bisoprolol (Rs: 0 → 0.36), and propranolol (Rs: 0 → 0.44). The immobilization pH of cellulase, buffer pH, UiO-66-NH₂ concentration, and the proportion of organic modifier were evaluated in detail with enantiomerically separating chiral molecules. The intra-day, inter-day, column-to-column, and inter-batch precision have been discussed, the result was preferable, and the relative standard deviation (RSD) of separation parameters was <4.3%. Schematic representation of the preparation of a UiO-66-NH₂-modified organic polymer monolith for enantioseparating five racemic β-blockers. UiO-66-NH₂ was synthesized and converted into a monolith as the stationary phase. Then, the modified monolith containing cellulase as the chiral selector was applied in a capillary electrochromatography system for enantioseparating chiral drugs.

Microwave-Assisted Synthesis, Characterization and Modeling of CPO-27-Mg Metal-Organic Framework for Drug Delivery

The coordination polymer CPO-27-Mg was rapidly synthesized under microwave irradiation. This material exhibits a sufficiently high drug loading towards aspirin (~8% wt.) and paracetamol (~14% wt.). The binding of these two molecules with the inner surface of the metal-organic framework was studied employing the Gaussian and Plane Wave approach of the Density Functional Theory. The structure of CPO-27-Mg persists after the adsorption of aspirin or paracetamol and their desorption energies, being quite high, decrease under solvent conditions.

Magnetic Tunability in RE-DOBDC MOFs via NOx Acid Gas Adsorption

The magnetic susceptibility of NO_x-loaded RE-DOBDC (rare earth (RE): Y, Eu, Tb, Yb; DOBDC: 2,5-dihydroxyterephthalic acid) metal-organic frameworks (MOFs) is unique to the MOF metal center. RE-DOBDC samples were synthesized, activated, and subsequently exposed to humid NO_x. Each NO_x-loaded MOF was characterized by powder X-ray diffraction, and the magnetic characteristics were probed by using a VersaLab vibrating sample magnetometer (VSM). Lanthanide-containing RE-DOBDC (Eu, Tb, Yb) are paramagnetic with a reduction in paramagnetism upon adsorption of NO_x. Y-DOBDC has a diamagnetic moment with a slight reduction upon adsorption of NO_x. The magnetic susceptibility of the MOF is determined by the magnetism imparted by the framework metal center. The electronic population of orbitals contributes to determining the extent of magnetism and change with NO_x (electron acceptor) adsorption. Eu-DOBDC results in the largest mass magnetization change upon adsorption of NO_x due to more available unpaired f electrons. Experimental changes in magnetic moment were supported by density functional theory (DFT) simulations of NO_x adsorbed in lanthanide Eu-DOBDC and transition metal Y-DOBDC MOFs.

Spectroscopic studies of temperature induced phase transitions in metal-organic complex trans-PtCl2(PEt3)2

Tuning of molecular and electronic properties of Pt(II)-organic complexes have a profound effect on their applications in the fields of technology, pharmaceuticals and crystal engineering. Here, we present combined infrared and Raman spectroscopic investigations on trans-PtCl₂(PEt₃)₂ systematically carried out at various temperatures from 300 to 4.2 K in a wide spectral range. The studies suggest drastic orientational changes of different moieties around 180 K and 130 K in the ligand groups attached to the central Pt atom. This is accompanied by a systematic strengthening of C-H⋯Cl hydrogen bonds in the 180-130 K temperature range. A discontinuous change in intensity, peak variations of modes and emergence of new modes across 180 K and 130 K in the lattice region are suggestive of a possible structural phase transition. It is interesting to note that the spectral signatures of the low temperature phase are different from those reported recently for the high pressure phase in this compound. These studies will be useful in better understanding the physico-chemical properties of metal-organic complexes in order to exploit their applications in various bio-chemical and technological fields.

Porous materials as carriers of gasotransmitters towards gas biology and therapeutic applications

This review highlights the strategies employed to load and release gasotransmitters such as NO, CO and H₂S from different kinds of porous materials, including zeolites, mesoporous silica, metal–organic frameworks and protein assemblies.

Recent Advances in Polymeric Nanocomposites of Metal-Organic Frameworks (MOFs)

Recently, metal-organic frameworks (MOFs) have garnered enormous attention from researchers owing to their superior physicochemical properties, which are of particular interest in various fields such as catalysis and the diverse areas of biomedicine. Despite their position in the utilization for various applications compared to other innovative nanocarriers such as dendrimers and mesoporous silica nanoparticles (MSNs), in terms of advantageous physicochemical attributes, as well as attractive textural properties, ease of characterization, and abundant surface chemistry for functionalization and other benefits, MOFs yet suffer from several issues such as poor degradability, which might lead to accumulation-induced biocompatibility risk. In addition, some of the MOFs suffer from a shortcoming of poor colloidal stability in the aqueous solution, hindering their applicability in diverse biomedical fields. To address these limitations, several advancements have been made to fabricate polymeric nanocomposites of MOFs for their utility in various biomedical fields. In this review, we aim to provide a brief emphasis on various organic polymers used for coating over MOFs to improve their physicochemical attributes considering a series of recently reported intriguing studies. Finally, we summarize with perspectives.

The Impact of Synthesis Method on the Properties and CO2 Sorption Capacity of UiO-66(Ce)

A series of cerium-based UiO-66 was obtained via hydrothermal and sonochemical methods, using the same quantities of reagents (cerium ammonium nitrate (CAN), terephthalic acid (H2BDC)) and solvents) in each synthesis. The impact of synthesis method and metal to linker ratio on the structural and textural properties of obtained UiO-66(Ce), as well as their composition in terms of Ce4+/Ce3+ ratio, structure defects resulting from missing linker, and CO2 adsorption capacity was discussed. By using typical characterization techniques and methods, such as XRD, N2 and CO2 sorption, TGA, XPS, and SEM, it was shown that the agitation of reacting mixture during synthesis (caused by stirring or ultrasounds) allows to obtain structures that have more developed surfaces and fewer linker defects than when MOF was obtained in static conditions. The specific surface area was found to be of minor importance in the context of CO2 adsorption than the contribution of Ce3+ ions that were associated with the concentration of linker defects.

Theranostic Mn-Porphyrin Metal-Organic Frameworks for Magnetic Resonance Imaging-Guided Nitric Oxide and Photothermal Synergistic Therapy

Chemotherapy remains restricted by its toxic adverse effects and resistance to drugs. The treatment of nitric oxide (NO) combined with imaging-guided physical therapy is a promising alternative for clinical applications. Herein, we report nanoscale metal-organic framework (NMOF) systems to integrate magnetic resonance (MR) imaging, spatiotemporally controllable NO delivery, and photothermal therapy (PTT) as a new means of cancer theranostics. As a proof of concept, the NMOFs are prepared with biocompatible Zr⁴⁺ ions and Mn-porphyrin as a bridging ligand. By inserting paramagnetic Mn ions into porphyrin rings, Mn-porphyrin renders the NMOFs strong T₁-weighted MR contrast capacity and high photothermal conversion for efficient PTT. S-Nitrosothiol (SNO) is conjugated to the surfaces of the NMOFs for heat-sensitive NO generation. Moreover, single near-infrared (NIR) light triggers the controllable NO release and PTT simultaneously for their efficient synergistic therapy with one-step operation. Upon intravenous injection, NMOF-SNO shows effective tumor accumulation as exposed by the MR images of the tumor-bearing mice. When exposed to the NIR laser, the tumors of mice injected with NMOF-SNO are completely inhibited, verifying the efficiency of NMOF-SNO. For the first time, Mn-porphyrin NMOFs are developed to be an effective theranostic system for MR imaging-guided controllable NO release and photothermal synergetic therapy under single NIR irradiation.

Enzyme-MOF Nanoreactor Activates Nontoxic Paracetamol for Cancer Therapy

Prodrug activation, by exogenously administered enzymes, for cancer therapy is an approach to achieve better selectivity and less systemic toxicity than conventional chemotherapy. However, the short half-lives of the activating enzymes in the bloodstream has limited its success. Demonstrated here is that a tyrosinase-MOF nanoreactor activates the prodrug paracetamol in cancer cells in a long-lasting manner. By generating reactive oxygen species (ROS) and depleting glutathione (GSH), the product of the enzymatic conversion of paracetamol is toxic to drug-resistant cancer cells. Tyrosinase-MOF nanoreactors cause significant cell death in the presence of paracetamol for up to three days after being internalized by cells, while free enzymes totally lose activity in a few hours. Thus, enzyme-MOF nanocomposites are envisioned to be novel persistent platforms for various biomedical applications.

In situ growth of Zr-based metal-organic framework UiO-66-NH2 for open-tubular capillary electrochromatography

The high stability and other properties of Zr(IV)-based metal organic frameworks(MOFs) make it a promising choice for chromatographic separation, while the application in open-tubular capillary electrochromatography (OT-CEC) separation has not been explored yet. Herein, we report the first example of the in-situ growth of UiO-66-NH₂ onto the capillary for open-tubular capillary electrochromatography. UiO-66-NH₂ consists of ZrCl₄ and 2-amino-1,4-benzenedicarboxylic acid, which is highly porous and stable in a variety of solvents. The prepared UiO-66-NH₂ modified capillary was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectra (FT-IR), and the results confirmed the successful growth of the UiO-66-NH₂ . The baseline separation of chlorobenzenes, phenoxyacids and two groups of phenols was achieved owing to the combined interaction of π-π interaction, hydrophobic interaction, molecular sieve effect, electrophoretic migration and hydrogen-bonding interaction etc. Besides, the prepared capillaries showed good reproducibility, with relative standard deviations (RSDs) for intra-day, inter-day and column-to-column runs in the range of 1.38-2.60%, 3.39-4.05%, and 3.47-5.03%, respectively. Our work indicates Zr(IV)-based MOFs are promising materials as stationary phase in CEC separation.

Low temperature synthesis study of metal-organic framework CPO-27: investigating metal, solvent and base effects down to -78 °C

CPO-27-M (M = Co, Mg, Ni, Zn) metal-organic frameworks have been successfully synthesized at temperatures down to -78 °C in a range of solvent systems and their crystallinity and morphology analyzed by powder X-ray diffraction and scanning electron microscopy. CPO-27-Mg and -Zn could be synthesized at lower temperatures using MeOH-NaOH as the solvent with CPO-27-Zn showing the most crystalline material at -78 °C. CPO-27-Zn afforded the most crystalline samples of all studies in MeOH-TEA. However, in MeOH a non-porous monomeric [Zn(H₂dhtp)(H₂O)₂] complex was formed when no base was present. In THF with base (NaOH, TEA) the reaction produced crystalline MOFs in a controlled and stable manner at low temperatures, whilst the reagents were insoluble in THF at low temperature when no base was present. SEM was used to analyze the morphologies of the products.

Synthesis, functionalization, and applications of metal–organic frameworks in biomedicine

Metal–organic frameworks (MOFs), also known as coordination polymers, have attracted extensive research interest in the past few decades due to their unique physical structures and potentially vast applications.

Liposome-Coated Iron Fumarate Metal-Organic Framework Nanoparticles for Combination Therapy

One of the main problems for effective treatment of cancer is resistances, which often require combination therapy-for effective treatment. While there are already some potential drug carriers-e.g., liposomes, available for treatment-the effective loading and retention of the desired drug ratio can be challenging. To address this challenge, we propose a new type of drug carrier: liposome-coated metal-organic framework (MOF) nanoparticles. They combine the advantages of liposomes with an easy and efficient loading process. In this work, we present the successful synthesis of liposome-coated MOF nanoparticles via the fusion method. The resulting particles, once loaded, show no premature leakage and an efficient release. Their successful loading with both single and multiple drugs at the same time makes them an interesting candidate for use in combination therapy.

Computational investigation of metal organic frameworks for storage and delivery of anticancer drugs

The potential of metal organic frameworks (MOFs) as binary drug carriers was computationally investigated for storage and delivery of two anticancer drug molecules, methotrexate (MTX) and 5-fluorouracil (5-FU).

Metal organic frameworks based on bioactive components

This review highlights the latest advances of Metal Organic Frameworks (MOFs) in the promising biomedical domain, from their synthesis to their biorelated activities.

Metal–organic framework incorporated monolithic capillary for selective enrichment of phosphopeptides

Protein phosphorylation is a major post-translational modification, which plays a central role in the cellular signaling of numerous biological processes.

Inorganic mesoporous silicas as vehicles of two novel anthracene-based ruthenium metalloarenes

Two novel anthracene-based half-sandwich organometallic Ru(II) compounds, namely, [Ru(p-cymene)(L₁)Cl₂] (1) and [Ru(p-cymene)(L₂)Cl₂] (2) (L₁=1-(anthracen-9-yl)-N-(pyridin-3-ylmethyl)methanamine; L₂=1-(anthracen-9-yl)-N-(pyridin-4-ylmethyl)methanamine) have been synthesized and characterized. We demonstrate that the fluorescence properties of these complexes are highly affected by the linking position of the anthracene unit, as only 2 shows fluorescence emission in the blue region. Regarding their biological activity, both ruthenium metallodrugs show interaction with different biological targets such as S-donor amino acids (cysteine) and proteases (cysteine cathepsin B). Moreover, 1 and 2 show in vitro cytotoxicity against HL-60 cancer cell line (IC₅₀=84.5 and 87.0μM for 1 and 2, respectively), with cell death occurring via apoptosis. Further studies have shown that diffusion into cells is the main mechanism of metallodrug uptake. Finally, as a proof of concept, these ruthenium complexes have been successfully encapsulated into MCM-41 and SBA-15 mesoporous silicas using two different incorporation strategies (impregnation and grinding).

Light-induced nitric oxide release from physiologically stable porous coordination polymers

The development of nitric oxide (NO) releasing materials has been of significant importance due to their application in cell biology and biomedicine. Besides the macromolecular scaffold dangling NO releasing moiety, porous materials have been used to host such NO releasing molecules. Here we synthesized a series of porous coordination polymers (PCPs), in which N-nitrosamine functional groups as photoactive NO donors were introduced into the framework scaffolds by post-synthetic nitrosation of amine functionalized analogous PCPs. We further demonstrated a controlled release of NO from the PCPs by light irradiation. Though isoreticular frameworks based on octanuclear clusters of titanium or aluminium ions were chosen due to their water-stability, the frameworks showed difference in stability in cell culture media; while aluminium frameworks were less stable in water and physiological media, the titanium analogue was highly stable even under physiological conditions.

A novel zinc(ii) metal–organic framework with a diamond-like structure: synthesis, study of thermal robustness and gas adsorption properties

A novel 3D metal–organic framework with a diamond-like structure has been synthesised and structurally characterized. Adsorption of Ar, CO₂, H₂ and N₂ has been studied. Heats of CO₂ and H₂ adsorption were calculated according to the Clausius–Clapeyron equation.

A combined experimental and computational study of novel nanocage-based metal-organic frameworks for drug delivery

Three new metal organic frameworks (MOFs) with chemical formulae [(CH3)2NH2] [Sm3(L1)2(HCOO)2(DMF)2(H2O)]·2DMF·18H2O (1), [Cu2(L2)(H2O)2]·2.22DMA (2) and [Zn2(L1)(DMA)]·1.75DMA were synthesized and structurally characterized. 1 and 2 show a classical NbO-like topology and have two types of interconnected cages. 3 exhibits an uncommon zzz topology and has two types of interconnected cages. These MOFs can adsorb large amounts of the drug 5-fluorouracil (5-FU) and release it in a progressive way. 5-FU was incorporated into desolvated 1, 2 and 3 with loadings of 0.40, 0.42, and 0.45 g g(-1), respectively. The drug release rates were 72%, 96% and 79% of the drug after 96 hours in 1, 120 hours in 2 and 96 hours in 3, respectively. Grand Canonical Monte Carlo (GCMC) simulations were performed to investigate the molecular interactions during 5-FU adsorption to the three novel materials. The GCMC simulations reproduced the experimental trend with respect to the drug loading capacity of each material. They also provided a structural description of drug packing within the frameworks, helping to explain the load capacity and controlled release characteristics of the materials. 5-FU binding preferences to 1, 2 and 3 reflect the diversity in pore types, chemistry and sizes. The calculated drug load is more related to the molecular properties of accessible volume Vacc than to the pore size.

Facile Preparation of Core-Shell Magnetic Metal-Organic Framework Nanoparticles for the Selective Capture of Phosphopeptides

In regard to the phosphoproteome, highly specific and efficient capture of heteroideous kinds of phosphopeptides from intricate biological sample attaches great significance to comprehensive and in-depth phosphorylated proteomics research. However, until now, it has been a challenge. In this study, a new-fashioned porous immobilized metal ion affinity chromatography (IMAC) material was designed and fabricated to promote the selectivity and detection limit for phosphopeptides by covering a metal-organic frameworks (MOFs) shell onto Fe3O4 nanoparticles, taking advantage of layer-by-layer method (the synthesized nanoparticle denoted as Fe3O4@MIL-100 (Fe)). The thick layer renders the nanoparticles with perfect hydrophilic character, super large surface area, large immobilization of the Fe(3+) ions and the special porous structure. Specifically, the as-synthesized MOF-decorated magnetic nanoparticles own an ultra large surface area which is up to 168.66 m(2) g(-1) as well as two appropriate pore sizes of 1.93 and 3.91 nm with a narrow grain-size distribution and rapid separation under the magnetic circumstance. The unique features vested the synthesized nanoparticles an excellent ability for phosphopeptides enrichment with high selectivity for β-casein (molar ratio of β-casein/BSA, 1:500), large enrichment capacity (60 mg g(-1)), low detection limit (0.5 fmol), excellent phosphopeptides recovery (above 84.47%), fine size-exclusion of high molecular weight proteins, good reusability, and desirable batch-to-batch repeatability. Furthermore, encouraged by the experimental results, we successfully performed the as-prepared porous IMAC nanoparticle in the specific capture of phosphopeptides from the human serum (both the healthy and unhealthy) and nonfat milk, which proves itself to be a good candidate for the enrichment and detection of the low-abundant phosphopeptides from complicated biological samples.