Dual functions of pH-sensitive cation Zr-MOF for 5-Fu: large drug-loading capacity and high-sensitivity fluorescence detection

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Advancements and Challenges in the Application of Metal-Organic Framework (MOF) Nanocomposites for Tumor Diagnosis and Treatment

Nanoscale metal-organic frameworks (MOFs) offer high biocompatibility, nanomaterial permeability, substantial specific surface area, and well-defined pores. These properties make MOFs valuable in biomedical applications, including biological targeting and drug delivery. They also play a critical role in tumor diagnosis and treatment, including tumor cell targeting, identification, imaging, and therapeutic methods such as drug delivery, photothermal effects, photodynamic therapy, and immunogenic cell death. The diversity of MOFs with different metal centers, organics, and surface modifications underscores their multifaceted contributions to tumor research and treatment. This review is a summary of these roles and mechanisms. The final section of this review summarizes the current state of the field and discusses prospects that may bring MOFs closer to pharmaceutical applications.

A sandwich electrochemiluminescence immunoassay based on 1T-MoS2@dual MOFs for detecting CA153

A "signal-on" electrochemiluminescence (ECL) immunosensor has been proposed for detecting carbohydrate antigen 153 (CA153) based on the dual MOFs sandwich strategy. The conductive and porous substrate consisting of 1T-MoS2 and two-dimensional conductive metal-organic framework (MOF, Ni-HAB) was anchored onto the glassy carbon electrode (GCE) to label the capture antibody (Ab1), and the luminescence-functionalized MOF (Ru(bpy)32+@UiO-66-NH2) was utilized to immobilize the detection second antibody (Ab2) to construct a "signal-on" responsive sandwich-type electrochemiluminescence immunoassay. Meanwhile, tripropylamine (TPA) acts as the co-reactant and provides a luminescence system for Ru(bpy)32+@UiO-66-NH2. The luminescence-functionalized MOFs showed excellent ECL activity owing to the tunable structure of MOFs. The remarkable enhancement in ECL intensity was obtained by the immunoreaction of antigen and antibody. Under the optimized conditions, the biosensor exhibited a detection limit of 0.0001 U mL-1 (S/N = 3) with a wide range from 0.001 to 50 U mL-1. The proposed ECL immunosensor was applicable for detecting human serum samples with a recovery of 99.83 ∼ 101 % (RSD < 5 %). This work demonstrates that the advantage of multifunctional MOFs could be applied to construct highly selective ECL immunosensor, and it may facilitate the diagnosis of breast cancer in clinics.

Current Principles, Challenges, and New Metrics in pH-Responsive Drug Delivery Systems for Systemic Cancer Therapy

The paradigm of drug delivery via particulate formulations is one of the leading ideas that enable overcoming limitations of traditional chemotherapeutic agents. The trend toward more complex multifunctional drug carriers is well-traced in the literature. Nowadays, the prospectiveness of stimuli-responsive systems capable of controlled cargo release in the lesion nidus is widely accepted. Both endogenous and exogenous stimuli are employed for this purpose; however, endogenous pH is the most common trigger. Unfortunately, scientists encounter multiple challenges on the way to the implementation of this idea related to the vehicles' accumulation in off-target tissues, their immunogenicity, the complexity of drug delivery to intracellular targets, and finally, the difficulties in the fabrication of carriers matching all imposed requirements. Here, we discuss fundamental strategies for pH-responsive drug delivery, as well as limitations related to such carriers' application, and reveal the main problems, weaknesses, and reasons for poor clinical results. Moreover, we attempted to formulate the profiles of an "ideal" drug carrier in the frame of different strategies drawing on the example of metal-comprising materials and considered recently published studies through the lens of these profiles. We believe that this approach will facilitate the formulation of the main challenges facing researchers and the identification of the most promising trends in technology development.

A resonant energy transfer electrochemiluminescence immunosensor based on low trigger potential of Zn-metal organic framework and CoOOH nanosheets for 5-fluorouracil detection

The organic luminophores have inspired widespread interest in electrochemiluminescence (ECL). Herein, a novel rod-like metal-organic framework was formed by chelating Zn ion with 9,10-di(p-carboxyphenyl)-anthracene (DPA), defined as Zn-MOF for simplicity. In this proposal, the prepared Zn-MOF was first used as a powerful organic luminophore with low trigger potential, thus developing a competitive ECL immunoassay for ultrasensitive detection of 5-fluorouracil (5-FU) with 1,4-diazabicyclo[2.2.2]octane (D-H₂) as the coreactant. The absorption spectrum of cobalt oxyhydroxide (CoOOH) nanosheets and the ECL emission spectrum of Zn-MOF could be highly matched, which ensured the occurrence of resonance energy transfer (RET). For that, ECL-RET was applied in the assembly strategy of the ECL biosensor, and Zn-MOF was used as the energy donor and CoOOH nanosheets as the acceptor. Taking advantage of the luminophore and ECL-RET, the immunoassay can be used for ultra-sensitive quantitative detection of 5-fluorouracil. The proposed ECL-RET immunosensor showed satisfactory sensitivity and accuracy with a wider linear range from 0.001 to 1000 ng/mL, and a lower detection limit (0.52 pg/mL). Hence, it is worth believing that this strategy can pave a bright research direction for the detection of 5-FU or other biological small molecules.

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.

A 2D Porous Zinc-Organic Framework Platform for Loading of 5-Fluorouracil

A hydrostable 2D Zn-based MOF, {[Zn(5-PIA)(imbm)]·2H2O}n (1) (5-H2PIA = 5-propoxy-isophthalic acid, imbm = 1,4-di(1H-imidazol-1-yl)benzene), was synthesized and structurally characterized. Complex 1 shows good water and thermal stability based on the TGA and PXRD analyses and displays a 2D framework with 1D channels of 4.8 × 13.8 and 10.0 × 8.3 Å2 along the a axis. The 5-fluorouracil (5-FU) payload in activated complex 1 (complex 1a) is 19.3 wt%, and the cumulative release value of 5-FU at 120 h was about 70.04% in PBS (pH 7.4) at 310 K. In vitro MTT assays did not reveal any cytotoxic effect of NIH-3T3 and HEK-293 cells when the concentration of 1 was below 500 μg/mL and 5 μg/mL, respectively. No morphological abnormalities were observed on zebrafish exposed to complex 1.

Ultrasensitive and Specific Detection of Anticancer Drug 5-Fluorouracil in Blood Samples by a Surface-Enhanced Raman Scattering (SERS)-Based Lateral Flow Immunochromatographic Assay

5-Fluorouracil (5-FU) is an effective anticancer drug widely used in the world. To improve therapy efficiency and reduce side effects, it is very important to frequently detect the concentration of 5-FU in blood samples of patients. In this work, a new type of lateral flow immunochromatographic assay (LFIA) based on surface-enhanced Raman scattering (SERS) for ultrasensitive and specific detection of 5-FU in blood samples was developed. Au@Ag/Au nanoparticles (NPs) employing Au particles as the core and Ag/Au alloy as the shell were synthesized, characterized and used as the substrate in SERS-LFIA due to their high SERS enhancement and biocompatibility. The immunoprobe was made in the form of AuMBA@Ag/Au-Ab in which mercaptobenzoic acid (MBA, a common Raman active reporter) was embedded in the core-shell layer and the monoclonal antibody (mAb) against 5-FU was immobilized on the surface. The performance of SERS-LFIA was similar to that in colloidal gold based-LFIA, and the entire assay time was within 20 min. According to the color intensity on the testing (T) lines of LFIA strips visualized by eyes, the contents of 5-FU in the samples could be qualitatively or semi-quantitatively identified. Furthermore, by measuring the characteristic Raman intensities of MBA on T lines, quantitative detection of 5-FU in the samples were achieved. The IC50 and limit of detection (LOD) of the LFIA for 5-FU were found to be 20.9 pg mL-1 and 4.4 pg mL-1, respectively. There was no cross-reactivity (CR) of the LFIA with nine relative compounds, and the CR with cytosine, tegafur and carmofur were less than 4.5%. The recoveries of 5-FU from spiked blood samples were in the range of 78.6~86.4% with the relative standard deviation (RSD) of 2.69~4.42%. Five blood samples containing 5-FU collected from the Cancer Hospital were measured by SERS-LFIA, and the results were confirmed by LC-MS/MS. It was proven that the proposed method was able to simply and rapidly detect 5-FU in blood samples with high sensitivity, specificity, accuracy and precision.

Applications of Metal-Organic Frameworks as Drug Delivery Systems

In the last decade, metal organic frameworks (MOFs) have shown great prospective as new drug delivery systems (DDSs) due to their unique properties: these materials exhibit fascinating architectures, surfaces, composition, and a rich chemistry of these compounds. The DSSs allow the release of the active pharmaceutical ingredient to accomplish a desired therapeutic response. Over the past few decades, there has been exponential growth of many new classes of coordination polymers, and MOFs have gained popularity over other identified systems due to their higher biocompatibility and versatile loading capabilities. This review presents and assesses the most recent research, findings, and challenges associated with the use of MOFs as DDSs. Among the most commonly used MOFs for investigated-purpose MOFs, coordination polymers and metal complexes based on synthetic and natural polymers, are well known. Specific attention is given to the stimuli- and multistimuli-responsive MOFs-based DDSs. Of great interest in the COVID-19 pandemic is the use of MOFs for combination therapy and multimodal systems.