High performance liquid chromatography of substituted aromatics with the metal-organic framework MIL-100(Fe): Mechanism analysis and model-based prediction

A pH-Responsive Drug-Delivery System Based on Apatinib-Loaded Metal-Organic Frameworks for Ferroptosis-Targeted Synergistic Anti-Tumor Therapy

Purpose

The efficacy of systemic therapy for hepatocellular carcinoma (HCC) is limited mainly by the complex tumor defense mechanism and the severe toxic side-effects of drugs. The efficacy of apatinib (Apa), a key liver cancer treatment, is unsatisfactory due to inadequate targeting and is accompanied by notable side-effects. Leveraging nanomaterials to enhance its targeting represents a crucial strategy for improving the effectiveness of liver cancer therapy.

Patients and Methods

A metal polyphenol network-coated apatinib-loaded metal-organic framework-based multifunctional drug-delivery system (MIL-100@Apa@MPN) was prepared by using metal-organic frameworks (MOFs) as carriers. The nanoparticles (NPs) were subsequently characterized using techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), zeta potential measurements, and particle size analysis. In vitro experiments were conducted to observe the drug release kinetics and cytotoxic effects of MIL-100@Apa@MPN on HepG2 cells. The in vivo anti-tumor efficacy of MIL-100@Apa@MPN was evaluated using the H22 tumor-bearing mouse model.

Results

The formulated MIL-100@Apa@MPN demonstrates remarkable thermal stability and possesses a uniform structure, with measured drug-loading (DL) and encapsulation efficiency (EE) rates of 28.33% and 85.01%, respectively. In vitro studies demonstrated that HepG2 cells efficiently uptake coumarin-6-loaded NPs, and a significant increase in cumulative drug release was observed under lower pH conditions (pH 5.0), leading to the release of approximately 73.72% of Apa. In HepG2 cells, MIL-100@Apa@MPN exhibited more significant antiproliferative activity compared to free Apa. In vivo, MIL-100@Apa@MPN significantly inhibited tumor growth, attenuated side-effects, and enhanced therapeutic effects in H22 tumor-bearing mice compared to other groups.

Conclusion

We have successfully constructed a MOF delivery system with excellent safety, sustained-release capability, pH-targeting, and improved anti-tumor efficacy, highlighting its potential as a therapeutic approach for the treatment of HCC.

Synthesis of hierarchically porous zirconium-based metal-organic framework@silica core-shell stationary phase through etching strategy for liquid chromatography

Metal organic frameworks (MOFs) show promise to be employed as stationary phase for high performance liquid chromatography (HPLC), however, the microporous structures of MOFs seriously restrict the diffusion and mass transfer of solute molecules, leading to a low column efficiency. In this paper, the fabrication of hierarchically porous UiO-66@SiO2 (HP- UiO-66@SiO2) core-shell microspheres via H2O2 etching has been proposed as a viable approach to enhance the separation performance of MOFs-based columns for HPLC. Through the direct treatment of the preliminary prepared UiO-66@SiO2 microspheres with H2O2 etching, HP-UiO-66@SiO2 core-shell microspheres were successfully synthesized with an enlarged pore size of up to 9 nm, facilitating efficient mass transfer in chromatographic separation. The prepared HP-UiO-66@SiO2 core-shell microspheres were then explored as stationary phase in HPLC to separate the nonpolar alkyl benzene homologues, the polar aromatic alcohol homologues and the xylene isomers. The results indicated that the baseline separations of these solutes were achieved successfully with narrow peak width and higher resolution than the UiO-66@SiO2 column. The HP-UiO-66@SiO2 column exhibited superior separation performance, reaching a maximum plate number of 134,459/m for fluorene, and showing good reproducibility. As a result, this template-free approach suggests that the fabrication of hierarchically porous MOFs@silica core-shell microspheres is a successful approach to enhance the column efficiency of MOFs-based columns in HPLC.

Regulating metal-organic frameworks as stationary phases and absorbents for analytical separations

Metal-organic frameworks (MOFs) are highly ordered framework systems composed of metal centers and organic linkers formed through coordination bonds. The diversity of metal elements and easily modified organic ligands, together with controllable synthetic approaches, gives rise to the designability of various MOF structures and topologies and the capability of MOFs to be functionalized. Their structural diversity provides MOFs with many unique properties, such as permanent porosity, flexible structures, thermostability, and high adsorption capacity, leading to great practicability in technical applications. In this review, we concentrate on the applications of MOFs in the field of gas chromatography, high-performance liquid chromatography, and the enrichment of biomolecules, based on rational arrangements in the structures and functions of MOFs. Moreover, we emphasize the importance of structural and chemical regulations for the improvement of separation efficiency.

Preparation of value-added metal-organic frameworks for high-performance liquid chromatography. Towards green chromatographic columns

This work applies the concepts of green chemistry, where polyethylene terephthalate (PET) bottles were used as the acid-dicarboxylic linker source for the synthesis of MIL-53(Al) metal organic frameworks (MOFs) and then used as a stationary phase for the separation of various solutes and compared with MIL-53(Al) synthesized from traditional terephthalic acid. Both synthesized MIL-53(Al) MOFs were characterized by scanning electron microscopy (SEM), FT-IR, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and specific surface area analysis. Eight groups of standard analytes in addition to real samples were tested to evaluate the separation performance of the MIL-53(Al) packed columns in HPLC under various chromatographic conditions. Based on elution order of the studied compounds and the effects of mobile phase composition, the working mechanism was reversed phase mode in the presence of size-exclusion effects for large molecules, which exceeded the dynamic diameter of MIL-53(Al) (~7.6 Å). The effects of stationary phase sieving, mobile phase flow rate and composition, injected sample mass, and temperature were investigated relative to the chromatographic behavior of MIL-53(Al). MIL-53(Al) particle sieving before packing reduced peak broadening and significantly enhanced the chromatographic performance of the prepared columns up to 2.26 times relative to the number of theoretical plates. The MIL-53(Al) packed columns offered high-resolution separation for all studied mixtures with R_s >2 and good stability and long-term durability. At optimal conditions, the prepared columns exhibited efficiencies between 5600-63200 plates m^-1. Higher efficiencies were observed for alkylbenzenes and polyaromatic hydrocarbons as the organic linker in the MIL-53(Al) structure, which improved retention and separation of aromatics through π-π interactions. Thermodynamic parameters including ΔH, ΔS, and ΔG for the transfer of analyte from the mobile phase to the MIL-53(Al) stationary phase were studied. Compared with previously cited MOFs packed columns, the present MIL-53(Al) columns gave comparable selectivity and much better efficiency for most of the studied chemicals at optimum conditions, indicating the feasibility of MIL-53(Al) as a stationary phase for HPLC applications.

Controlled Fabrication of Silica@Covalent Triazine Polymer Core-Shell Spheres as a Reversed-Phase/Hydrophilic Interaction Mixed-Mode Chromatographic Stationary Phase

The unique properties of covalent triazine-based organic framework/polymers, including large surface area, hydrophilic-lipophilic-balanced adsorption, and economical preparation, make it a promising candidate as a stationary phase for high-performance liquid chromatography. However, irregular shapes and wide size distributions of such particles hinder column packing, resulting in a low column efficiency or a high back pressure. Herein, we describe the fabrication of SiO₂@ covalent triazine-based organic polymer (CTP) core-shell microspheres with a distinct sphere-coating-sphere appearance using aminosilica as the supporting substrate to grow the CTP shell. By adjusting the amount of reactants, the thickness of the CTP shell, which consists of triazine and 1,3,5-triphenylbenzene monomers, was easily controlled. The developed core-shell microspheres were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, solid-state ¹³C nuclear magnetic resonance analysis, and N₂ adsorption experiments. The synergism of the triazine and aromatic moieties on CTP provides the new stationary phase with multiple retention mechanisms, including hydrophobic, π-π, electron donor-acceptor, hydrogen-bonding interactions, and so forth. On the basis of these interactions, successful separation and higher shape selectivity were achieved among several analytes that vary in polarity under both reversed-phase and hydrophilic interaction liquid chromatography conditions. Therefore, SiO₂@CTP microspheres combine the advantages of good column packing properties of the uniform monodisperse silica microspheres and the recognition performance of CTP, generating flexible selectivity and application prospect for both hydrophilic and hydrophobic analytes.

Core-Shell Metal-Organic Frameworks as the Mixed-Mode Stationary Phase for Hydrophilic Interaction/Reversed-Phase Chromatography

Stationary phases with mixed-mode mechanisms have emerged as a hot research topic. In the present research, monodisperse core-shell UiO-67@SiO₂ materials were prepared and further served as the packed column for mixed-mode hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography. The developed UiO-67@SiO₂ materials were characterized via thermogravimetric analysis, scanning electron microscopy, X-ray Powder diffraction, and Fourier transform infrared techniques. The developed UiO-67@SiO₂ column shows flexible selectivity for separation of both hydrophobic (anilines, alkylbenzenes, and polycyclic aromatic hydrocarbons) and hydrophilic (thioureas) compounds. Furthermore, the UiO-67@SiO₂ column was also utilized to characterize potential pollutants in lake water samples. In summary, the UiO-67@SiO₂ column provided flexible selectivity and wide-range retention behaviors for both hydrophilic and hydrophobic analytes.

Excess adsorption of acetonitrile and water on MIL-100(Fe) and its potential application in mixed-mode chromatography

Potential application of MIL-100(Fe) to reversed- and-normal phase mixed-mode chromatography was suggested.

Cationic Ionic Liquids Organic Ligands Based Metal-Organic Frameworks for Fabrication of Core-Shell Microspheres for Hydrophilic Interaction Liquid Chromatography

In this study, new metal-organic frameworks (MOFs) nanocrystals modified SiO2 core-shell microspheres were designed with cationic ionic liquids (ILs) 1,3-bis(4-carboxybutyl)imidazolium bromide (ILI) as organic ligands. By further adjustment the growth cycles, the new ILI-01@SiO2 core-shell stationary phase was facilely fabricated. The developed stationary phase was respectively characterized via element analysis, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. Because the introduction of cationic imidazolium-based ILs ILI for fabrication of the MOFs nanocrystals shell, the new stationary phase exhibits the retention mechanism of hydrophilic interaction liquid chromatography (HILIC). Many polar samples, such as amides, vitamins, nucleic acid bases, and nucleosides, were utilized to investigate the performance of the prepared ILI-01@SiO2 column. Compared to the conventional aminosilica column, the new ILI-01@SiO2 column displays high separation selectivity in a shorter separation time. Furthermore, the new ILI-01@SiO2 column was also used for detection of illegal melamine addition in the baby formula. All the above results demonstrate the new ILI-01@SiO2 core-shell stationary phase is of good potentials for high-selectivity separation the polar samples.