MIL-100(Al) Gels as an Excellent Platform Loaded with Doxorubicin Hydrochloride for pH-Triggered Drug Release and Anticancer Effect

Degradation and Erosion of Metal-Organic Frameworks: Comparative Study of a NanoMIL-100 Drug Delivery System

To make a drug work better, the active substance can be incorporated into a vehicle for optimal protection and control of the drug delivery time and space. For making the drug carrier, the porous metal-organic framework (MOF) can offer high drug-loading capacity and various designs for effective drug delivery performance, biocompatibility, and biodegradability. Nevertheless, its degradation process is complex and not easily predictable, and the toxicity concern related to the MOF degradation products remains a challenge for their clinical translation. Here, we describe an in-depth molecular and nanoscale degradation mechanism of aluminum- and iron-based nanoMIL-100 materials exposed to phosphate-buffered saline. Using a combination of analytical tools, including X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, small-angle X-ray scattering, and electron microscopy, we demonstrate qualitatively and quantitatively the formation of a new coordination bond between metal(III) and phosphate, trimesate release, and correlation between these two processes. Moreover, the extent of material erosion, i.e., bulk or surface erosion, was examined from the transformation of nanoparticles' surface, morphology, and interaction with water. Similar analyses show the impact of drug loading and surface coating on nanoMIL-100 degradation and drug release as a function of the metal-ligand binding strength. Our results indicate how the chemistry of nanoMIL-100(Al) and nanoMIL-100(Fe) drug carriers affects their degradation behaviors in a simulated physiological medium. This difference in behavior between the two nanoMIL-100s enables us to better correlate the nanoscale and atomic-scale mechanisms of the observed phenomena, thus validating the presented multiscale approach.

Metal-organic gels: recent advances in their classification, characterization, and application in the pharmaceutical field

Metal-organic gels (MOGs) are a type of functional soft substance with a three-dimensional (3D) network structure and solid-like rheological behavior, which are constructed by metal ions and bridging ligands formed under the driving force of coordination interactions or other non-covalent interactions. As the homologous substances of metal-organic frameworks (MOFs) and gels, they exhibit the potential advantages of high porosity, flexible structure, and adjustable mechanical properties, causing them to attract extensive research interest in the pharmaceutical field. For instance, MOGs are often used as excellent vehicles for intelligent drug delivery and programmable drug release to improve the clinical curative effect with reduced side effects. Also, MOGs are often applied as advanced biomedical materials for the repair and treatment of pathological tissue and sensitive detection of drugs or other molecules. However, despite the vigorous research on MOGs in recent years, there is no systematic summary of their applications in the pharmaceutical field to date. The present review systematically summarize the recent research progress on MOGs in the pharmaceutical field, including drug delivery systems, drug detection, pharmaceutical materials, and disease therapies. In addition, the formation principles and classification of MOGs are complemented and refined, and the techniques for the characterization of the structures/properties of MOGs are overviewed in this review.

Hybrid liposome/metal-organic framework as a promising dual-responsive nanocarriers for anticancer drug delivery

In this work, liposome-coated iron (III) benzene-1,3,5-tricarboxylate (Fe-BTC) metal-organic framework is examined as a promising pH/Ultrasound dual-responsive nanocarriers for doxorubicin (DOX) delivery. The successful coating of the MOF particles (Lip-Fe-BTC) with the phospholipid bilayer (PBL) was established by direct fusion into the synthesized liposomes. The liposome coating was verified using several techniques, including dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS measurements showed an increase in the average particle diameter of liposomes from 150 nm to 163.1 nm for Lip-Fe-BTC particles. The Fe-BTC particles had the highest average particle diameter (287.3 nm). These results demonstrated that the PBL reduced the aggregation of the particles and improved their dispersity in the release medium. The TGA results demonstrated the MOF's excellent thermal stability. Furthermore, the nanocarrier's loading efficiency and capacity were determined to be ~90% and ~13.5 wt%, respectively. The in-vitro DOX release experiments demonstrated that the DOX-loaded Fe-BTC and liposome-coated Fe-BTC particles showed good pH and US dual-responsive capability, making them promising nanocarriers for drug delivery. The application of US enhanced DOX release from both Fe-BTC and liposome-coated Fe-BTC. In the case of Fe-BTC-DOX particles, the application of US enhanced the DOX release to around 38% and 67%, at pH levels of 7.4 and 5.3, respectively. Similarly, DOX release from the Lip-Fe-BTC-DOX particles reached ~35% and ~53%, at pH levels of 7.4 and 5.3, respectively. The MTT assay showed the biocompatibility and low cytotoxicity of these nanocarriers below 100 µg/ml.

Post-synthetic modification of aluminum trimesate and copper trimesate with TiO2 nanoparticles for photocatalytic applications

Organic pollutants have been a significant source of concern in recent years due to their facile dissemination and harmful effects. In this work, two different metal-organic frameworks (MOFs) were initially prepared by hydrothermal treatment, namely aluminum trimesate (MIL-100(Al)) and copper trimesate (HKUST-1). These materials were subsequently submitted to a post-synthetic modification step to grow titania nanoparticles on their surface. Anatase nanoparticles with sizes around 5 nm were successfully anchored on MIL-100(Al), and the concentration of TiO₂ in this sample was about 68 wt.%. This is the first time that this composite (TiO₂@MIL-100(Al)) is reported in the literature. It showed an improved photocatalytic activity, removing 90% of methylene blue (k _app = 1.29 h^-1), 55% of sodium diclofenac (k _app = 0.21 h^-1), and 62% of ibuprofen (k _app = 0.37 h^-1) after four hours of illumination with UV-A light. A significant concentration (14 µM) of reactive oxygen species (ROS) was detected for this composite. HKUST-1 showed a structural collapse during its post-synthetic modification, leading to a non-porous material and providing fewer sites for the heterogeneous nucleation of titania. This behavior led to a low concentration of rutile nanoparticles on HKUST-1 (9 wt.%). However, the obtained composite (TiO₂@HKUST) also showed an improved photoactivity compared to HKUST-1, increasing the photodegradation rates evaluated for methylene blue (0.05 h^-1 vs. 0.29 h^-1), sodium diclofenac (negligible vs. 0.03 h^-1), and ibuprofen (0.01 h^-1 vs. 0.02 h^-1). This work brings new insights concerning the preparation of photocatalysts by growing semiconductor nanoparticles on trimesate-based MOFs.

Porous nanoparticles with engineered shells release their drug cargo in cancer cells

Highly porous nanoscale metal-organic frameworks (nanoMOFs) attract growing interest as drug nanocarriers. However, engineering "stealth" nanoMOFs with poly(ethylene glycol) (PEG) coatings remains a main challenge. Here we address the goal of coating nanoMOFs with biodegradable shells using novel cyclodextrin (CD)-based oligomers with a bulky structure to avoid their penetration inside the open nanoMOF porosity. The PEG chains were grafted by click chemistry onto the CDs which were further crosslinked by citric acid. Advantageously, the oligomers' free citrate units allowed their spontaneous anchoring onto the nanoMOFs by complexation with the iron sites in the top layers. Up to 31 wt% oligomers could be firmly attached by simple incubation with the nanoMOFs in an aqueous medium. Moreover, the anticancer drug doxorubicin (DOX) was successfully entrapped in the core-shell nanoMOFs with loadings up to 41 wt%. High resolution STEM (HR-STEM) showed that the organized crystalline structures were preserved. Remarkably, at the highest loadings, DOX was poorly released out of the nanoMOFs at pH 7.4 (<2% in 2 days). In contrast, around 80% of DOX was released out at pH 4.5 of artificial lysosomal fluid in 24 h. Confocal microscopy investigations showed that the DOX-loaded nanoMOFs penetrated inside Hela cancer cell together with their PEG shells. There, they released the DOX cargo which further diffused inside the nucleus to eradicate the cancer cells.

Doxorubicin-Loaded Metal-Organic Frameworks Nanoparticles with Engineered Cyclodextrin Coatings: Insights on Drug Location by Solid State NMR Spectroscopy

Recently developed, nanoscale metal-organic frameworks (nanoMOFs) functionalized with versatile coatings are drawing special attention in the nanomedicine field. Here we show the preparation of core-shell MIL-100(Al) nanoMOFs for the delivery of the anticancer drug doxorubicin (DOX). DOX was efficiently incorporated in the MOFs and was released in a progressive manner, depending on the initial loading. Besides, the coatings were made of biodegradable γ-cyclodextrin-citrate oligomers (CD-CO) with affinity for both DOX and the MOF cores. DOX was incorporated and released faster due to its affinity for the coating material. A set of complementary solid state nuclear magnetic resonance (ssNMR) experiments including 1H-1H and 13C-27Al two-dimensional NMR, was used to gain a deep understanding on the multiple interactions involved in the MIL-100(Al) core-shell system. To do so, 13C-labelled shells were synthesized. This study paves the way towards a methodology to assess the nanoMOF component localization at a molecular scale and to investigate the nanoMOF physicochemical properties, which play a main role on their biological applications.

CO2 gas separation using mixed matrix membranes based on polyethersulfone/MIL-100(Al)

The excessive use of natural gas and other fossil fuels by the industrial sector leads to the production of great quantities of gas pollutants, including CO2, SO2, and NO x . Consequently, these gases increase the temperature of the earth, producing global warming. Different strategies have been developed to help overcome this problem, including the utilization of separation membrane technology. Mixed matrix membranes (MMMs) are hybrid membranes that combine an organic polymer as a matrix and an inorganic compound as a filler. In this study, MMMs were prepared based on polyethersulfone (PES) and a type of metal–organic framework (MOF), Materials of Institute Lavoisier (MIL)-100(Al) [Al3O(H2O)2(OH)(BTC)2] (BTC: benzene 1,3,5-tricarboxylate) using a phase inversion method. The influence on the properties of the produced membranes by addition of 5, 10, 20, and 30% MIL-100(Al) (w/w) to the PES was also investigated. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that no chemical interactions occurred between PES and MIL-100(Al). Scanning electron microscope (SEM) images showed agglomeration at PES/MIL-100(Al) 30% (w/w) and that the thickness of the dense layer increased up to 3.70 µm. After the addition of MIL-100(Al) of 30% (w/w), the permeability of the MMMs for CO2, O2, and N2 gases was enhanced by approximately 16, 26, and 14 times, respectively, as compared with a neat PES membrane. The addition of MIL-100(Al) to PES increased the thermal stability of the membranes, reaching 40°C as indicated by thermogravimetry analysis (TGA). An addition of 20% MIL-100(Al) (w/w) increased membrane selectivity for CO2/O2 from 2.67 to 4.49 (approximately 68.5%), and the addition of 10% MIL-100(Al) increased membrane selectivity for CO2/N2 from 1.01 to 2.12 (approximately 110.1%).

Soft and Condensed Nanoparticles and Nanoformulations for Cancer Drug Delivery and Repurpose

Drug repurpose or reposition is recently recognized as a high-performance strategy for developing therapeutic agents for cancer treatment. This approach can significantly reduce the risk of failure, shorten R&D time, and minimize cost and regulatory obstacles. On the other hand, nanotechnology-based delivery systems are extensively investigated in cancer therapy due to their remarkable ability to overcome drug delivery challenges, enhance tumor specific targeting, and reduce toxic side effects. With increasing knowledge accumulated over the past decades, nanoparticle formulation and delivery have opened up a new avenue for repurposing drugs and demonstrated promising results in advanced cancer therapy. In this review, recent developments in nano-delivery and formulation systems based on soft (i.e., DNA nanocages, nanogels, and dendrimers) and condensed (i.e., noble metal nanoparticles and metal-organic frameworks) nanomaterials, as well as their theranostic applications in drug repurpose against cancer are summarized.