A “Ship in a Bottle” Strategy To Load a Hydrophilic Anticancer Drug in Porous Metal Organic Framework Nanoparticles: Efficient Encapsulation, Matrix Stabilization, and Photodelivery

MOFs for next-generation cancer therapeutics through a biophysical approach-a review

Metal-organic frameworks (MOFs) have emerged as promising nanocarriers for cancer treatment due to their unique properties. Featuring high porosity, extensive surface area, chemical stability, and good biocompatibility, MOFs are ideal for efficient drug delivery, targeted therapy, and controlled release. They can be designed to target specific cellular organelles to disrupt metabolic processes in cancer cells. Additionally, functionalization with enzymes mimics their catalytic activity, enhancing photodynamic therapy and overcoming apoptosis resistance in cancer cells. The controllable and regular structure of MOFs, along with their tumor microenvironment responsiveness, make them promising nanocarriers for anticancer drugs. These carriers can effectively deliver a wide range of drugs with improved bioavailability, controlled release rate, and targeted delivery efficiency compared to alternatives. In this article, we review both experimental and computational studies focusing on the interaction between MOFs and drug, explicating the release mechanisms and stability in physiological conditions. Notably, we explore the relationship between MOF structure and its ability to damage cancer cells, elucidating why MOFs are excellent candidates for bio-applicability. By understanding the problem and exploring potential solutions, this review provides insights into the future directions for harnessing the full potential of MOFs, ultimately leading to improved therapeutic outcomes in cancer treatment.

Polysilsesquioxane decorated ZIF-8 as a potential pH-responsive vehicle for topical delivery and release of acyclovir and tetracycline: Investigation of blood compatibility, cytotoxicity and antibacterial properties

In this research, poly-chloropropylmethyl-silsesquioxanen was prepared and decorated with ZIF-8 in order to investigate its loading capacity for acyclovir and tetracycline. Before and after drug loadings, the composites were characterized by FT-IR, SEM-EDS, XRD, and XPS analyses. Then, the in-vitro release of these drugs was investigated by UV-Vis spectroscopy in different buffers (pH = 5, 7.4, and 9.1). The results showed that the release of ACV reached a maximum amount of 41.3 mg at pH = 7.4 during 12 h. In comparison, the release of TC reached a maximum amount of 22.5 mg at pH = 5 during 6 h. The blood compatibility, in-vitro cytotoxicity on the L929 fibroblast cells line, and antibacterial assay against Staphylococcus aureus and Pseudomonas aeruginosa were also investigated for this composite as a drug carrier.

Oxaliplatin-Loaded Mil-100(Fe) for Chemotherapy-Ferroptosis Combined Therapy for Gastric Cancer

Oxaliplatin (Oxa) is a commonly used chemotherapy drug in the treatment of gastric cancer, but its toxic side effects and drug resistance after long-term use have seriously limited its efficacy. Loading chemotherapy drugs with nanomaterials and delivering them to the tumor site are common ways to overcome the above problems. However, nanomaterials as carriers do not have therapeutic functions on their own, and the effect of single chemotherapy is relatively limited, so there is still room for progress in related research. Herein, we construct Oxa@Mil-100(Fe) nanocomposites by loading Oxa with a metal-organic framework (MOF) Mil-100(Fe) with high biocompatibility and a large specific surface area. The pore structure of Mil-100(Fe) is conducive to a large amount of Oxa loading with a drug-loading rate of up to 27.2%. Oxa@Mil-100(Fe) is responsive to the tumor microenvironment (TME) and can release Oxa and Fe3+ under external stimulation. On the one hand, Oxa can inhibit the synthesis of DNA and induce the apoptosis of gastric cancer cells. On the other hand, Fe3+ can clear overexpressed glutathione (GSH) in TME and be reduced to Fe2+, inhibiting the activity of glutathione peroxidase 4 (GPX4), leading to the accumulation of intracellular lipid peroxides (LPO), and at the same time releasing a large number of reactive oxygen species (ROS) through the Fenton reaction, inducing ferroptosis in gastric cancer cells. With the combination of apoptosis and ferroptosis, Oxa@Mil-100(Fe) shows a good therapeutic effect, and the killing effect on gastric cancer cells is obvious. In a nude mouse model of subcutaneous tumor transplantation, Oxa@Mil-100(Fe) shows a significant inhibitory effect on tumor growth, with an inhibition rate of nearly 60%. In addition to its excellent antitumor activity, Oxa@Mil-100(Fe) has no obvious toxic or side effects. This study provides a new idea and method for the combined treatment of gastric cancer.

Advanced Characterization Methodology to Unravel the Biodegradability of Metal-Organic Framework Nanoparticles in Extremely Diluted Conditions

Porous iron(III) carboxylate metal-organic frameworks (MIL-100; MIL stands for Material of Institute Lavoisier) of submicronic size (nanoMOFs) have attracted a growing interest in the field of drug delivery due to their high drug payloads, excellent entrapment efficiencies, biodegradable character, and poor toxicity. However, only a few studies have dealt with the nanoMOF degradation mechanism, which is key to their biological applications. Complementary methods have been used here to investigate the degradation mechanism of Fe-based nanoMOFs under neutral or acidic conditions and in the presence of albumin. High-resolution STEM-HAADF coupled with energy-dispersive X-ray spectroscopy enabled the monitoring of the crystalline organization and elemental distribution during degradation. NanoMOFs were also deposited onto silicon substrates by dip-coating, forming stable thin films of high optical quality. The mean film thickness and structural changes were further monitored by IR ellipsometry, approaching the "sink conditions" occurring in vivo. This approach is essential for the successful design of biocompatible nano-vectors under extreme diluted conditions. It was revealed that while the presence of a protein coating layer did not impede the degradation process, the pH of the medium in contact with the nanoMOFs played a major role. The degradation of nanoMOFs occurred to a larger extent under neutral conditions, rapidly and homogeneously within the crystalline matrices, and was associated with the departure of their constitutive organic ligand. Remarkably, the nanoMOFs' particles maintained their global morphology during degradation.

Advancing Cancer Treatment: Enhanced Combination Therapy through Functionalized Porous Nanoparticles

Cancer remains a major global health challenge, necessitating the development of innovative treatment strategies. This review focuses on the functionalization of porous nanoparticles for combination therapy, a promising approach to enhance cancer treatment efficacy while mitigating the limitations associated with conventional methods. Combination therapy, integrating multiple treatment modalities such as chemotherapy, phototherapy, immunotherapy, and others, has emerged as an effective strategy to address the shortcomings of individual treatments. The unique properties of mesoporous silica nanoparticles (MSN) and other porous materials, like nanoparticles coated with mesoporous silica (NP@MS), metal-organic frameworks (MOF), mesoporous platinum nanoparticles (mesoPt), and carbon dots (CDs), are being explored for drug solubility, bioavailability, targeted delivery, and controlled drug release. Recent advancements in the functionalization of mesoporous nanoparticles with ligands, biomaterials, and polymers are reviewed here, highlighting their role in enhancing the efficacy of combination therapy. Various research has demonstrated the effectiveness of these nanoparticles in co-delivering drugs and photosensitizers, achieving targeted delivery, and responding to multiple stimuli for controlled drug release. This review introduces the synthesis and functionalization methods of these porous nanoparticles, along with their applications in combination therapy.

Study of Drug Delivery Using Purely Organic Macrocyclic Containers-Cucurbit[7]uril and Pillararene

An impaired immune system is the root of various human ailments provoking the urge to find vehicle-mediated quick delivery of small drug molecules and other vital metabolites to specific tissues and organs. Thus, drug delivery strategies are in need of improvement in therapeutic efficacy. It can be achieved only by increasing the drug-loading capacity, increasing the sustained release of a drug to its target site, easy relocation of drug molecules associated with facile complexation-induced properties of molecular vehicles, and high stimuli-responsive drug administration. Supramolecular drug delivery systems (SDDS) provide a much needed robust yet facile platform for fabricating innovative drug nanocarriers assembled by thermodynamically noncovalent interaction with the tunable framework and above-mentioned properties. Measures of cytotoxicity and biocompatibility are the two main criteria that lie at the root of any promising medicinal applications. This Review features significant advancements in (i) supramolecular host-guest complexation using cucurbit[7]uril (CB[7]), (ii) encapsulation of the drug and its delivery application tailored for CB[7], (iii) self-assembly of supramolecular amphiphiles, (iv) supramolecular guest relay using host-protein nanocavities, (v) pillararene (a unique macrocyclic host)-mediated SDDS for the delivery of smart nanodrugs for siRNA, fluorescent molecules, and insulin for juvenile diabetes. Furthermore, fundamental questions and future hurdles related to smart SDDS based on CB[7] and pillararenes and their future promising breakthrough implementations are also distinctly outlined in this Review.

A simple one step synthesis of magnetic-optical dual functional ZIF-8 in a sodalite phase for magnetically guided targeting bioimaging and drug delivery

Functionalized metal-organic frameworks (MOFs) that integrate targeted tumor imaging and drug delivery are expected to significantly enhance the therapeutic efficacy of cancer. However, the complicated synthesis process has greatly limited their utilization in clinical application. Herein, a one-step simple method was used to construct novel multifunctional MOFs by co-loading doxorubicin (DOX) and Fe3O4 into the ZIF-8 with sodalite topology. DOX serves as a fluorescence imaging reagent and an anticancer drug and Fe3O4 is used as a magnetic resonance imaging and magnetic targeting anticancer reagent. The fabricated DOX/Fe3O4@ZIF-8 nanocomposite showed excellent fluorescence and magnetic resonance imaging performances in tumors. Moreover, DOX/Fe3O4@ZIF-8 can be accumulated in tumors via a magnetic targeting effect and tumor growth could be inhibited in vivo due to the release of DOX. Additionally, the apoptosis process of DOX/Fe3O4@ZIF-8 on HepG2 cells is well investigated. Overall, DOX/Fe3O4@ZIF-8 synthesized in simple one step can be used for simultaneous targeted bioimaging and cancer therapy.

Directing the Selectivity of Oxygen Reduction to Water by Confining a Cu Catalyst in a Metal Organic Framework

Electrocatalysis is to play a key role in the transition towards a sustainable chemical and energy industry and active, stable and selective redox catalysts are much needed. Porous structures such as metal organic frameworks (MOFs) are interesting materials as these may influence selectivity of chemical reactions through confinement effects. In this work, the oxygen reduction catalyst Cu-tmpa was incorporated into the NU1000 MOF. Confinement of the catalyst within NU1000 steers the selectivity of the oxygen reduction reaction (ORR) towards water rather than peroxide. This is attributed to retention of the obligatory H2 O2 intermediate in close proximity to the catalytic center. Moreover, the resulting NU1000|Cu-tmpa MOF shows an excellent activity and stability in prolonged electrochemical studies, illustrating the potential of this approach.

Stimuli-Responsive Design of Metal-Organic Frameworks for Cancer Theranostics: Current Challenges and Future Perspective

Scientific fraternity revealed the potential of stimuli-responsive nanotherapeutics for cancer treatment that aids in tackling the major restrictions of traditionally reported drug delivery systems. Among stimuli-responsive inorganic nanomaterials, metal-organic frameworks (MOFs) have transpired as unique porous materials displaying resilient structures and diverse applications in cancer theranostics. Mainly, it demonstrates tailorable porosity, versatile chemical configuration, tunable size and shape, and feasible surface functionalization, etc. The present review provides insights into the design of stimuli-responsive multifunctional MOFs for targeted drug delivery and bioimaging for effective cancer therapy. Initially, the concept of cancer, traditional cancer treatment, background of MOFs, and approaches for MOFs synthesis have been discussed. After this, applications of stimuli-responsive multifunctional MOFs-assisted nanostructures that include pH, light, ions, temperature, magnetic, redox, ATP, and others for targeted drug delivery and bioimaging in cancer have been thoroughly discussed. As an outcome, the designed multifunctional MOFs showed an alteration in properties due to the exogenous and endogenous stimuli that are beneficial for drug release and bioimaging. The several reported types of stimuli-responsive surface-modified MOFs revealed good biocompatibility to normal cells, promising drug loading capability, target-specific delivery of anticancer drugs into cancerous cells, etc. Despite substantial progress in this field, certain crucial issues need to be addressed to reap the clinical benefits of multifunctional MOFs. Specifically, the toxicological compatibility and biodegradability of the building blocks of MOFs demand a thorough evaluation. Moreover, the investigation of sustainable and greener synthesis methods is of the utmost importance. Also, the low flexibility, off-target accumulation, and compromised pharmacokinetic profile of stimuli-responsive MOFs have attracted keen attention. In conclusion, the surface-modified nanosized design of inorganic diverse stimuli-sensitive MOFs demonstrated great potential for targeted drug delivery and bioimaging in different kinds of cancers. In the future, the preference for stimuli-triggered MOFs will open a new frontier for cancer theranostic applications.

Robust Inclusion Complex of Topotecan Comprised within a Rhodamine-Labeled β-Cyclodextrin: Competing Proton and Energy Transfer Processes

Monitoring the biological fate of medicaments within the environments of cancer cells is an important challenge which is nowadays the object of intensive studies. In this regard, rhodamine-based supramolecular systems are one of the most suitable probes used in drug delivery thanks to their high emission quantum yield and sensitivity to the environment which helps to track the medicament in real time. In this work, we used steady-state and time-resolved spectroscopy techniques to investigate the dynamics of the anticancer drug, topotecan (TPT), in water (pH ~6.2) in the presence of a rhodamine-labeled methylated β-cyclodextrin (RB-RM-βCD). A stable complex of 1:1 stoichiometry is formed with a K_eq value of ~4 × 10⁴ M^-1 at room temperature. The fluorescence signal of the caged TPT is reduced due to: (1) the CD confinement effect; and (2) a Förster resonance energy transfer (FRET) process from the trapped drug to the RB-RM-βCD occurring in ~43 ps with 40% efficiency. These findings provide additional knowledge about the spectroscopic and photodynamic interactions between drugs and fluorescent functionalized CDs, and may lead to the design of new fluorescent CD-based host-guest nanosystems with efficient FRET to be used in bioimaging for drug delivery monitoring.

Inorganic nanoparticles as scaffolds for bioorthogonal catalysts

Bioorthogonal transition metal catalysts (TMCs) transform therapeutically inactive molecules (pro-drugs) into active drug compounds. Inorganic nanoscaffolds protect and solubilize catalysts while offering a flexible design space for decoration with targeting elements and stimuli-responsive activity. These "drug factories" can activate pro-drugs in situ, localizing treatment to the disease site and minimizing off-target effects. Inorganic nanoscaffolds provide structurally diverse scaffolds for encapsulating TMCs. This ability to define the catalyst environment can be employed to enhance the stability and selectivity of the TMC, providing access to enzyme-like bioorthogonal processes. The use of inorganic nanomaterials as scaffolds TMCs and the use of these bioorthogonal nanozymes in vitro and in vivo applications will be discussed in this review.

Nanoscale MOFs in nanomedicine applications: from drug delivery to therapeutic agents

Metal-organic frameworks (MOFs) hold great promise for widespread applications in biomedicine and nanomedicine. MOFs are one of the most fascinating nanocarriers for drug delivery, benefiting from their high porosity and facile modification. Furthermore, the tailored components of MOFs can be therapeutic agents for various treatments, including drugs as organic ligands of MOFs, active metal as central metal ions of MOFs, and their combinations as carrier-free MOF-based nanodrug. In this review, the advances in delivery systems and applications as therapeutic agents for nanoscale MOF-based materials are summarized. The challenges of MOFs in clinical translation and the future directions in the field of MOFs therapy are also discussed. We hope that more researchers will focus their attention on advancing and translating MOF-based nanodrugs into pre-clinical and clinical applications.

Nanoscale Iron-Based Metal-Organic Frameworks: Incorporation of Functionalized Drugs and Degradation in Biological Media

Metal-organic frameworks (MOFs) attract growing interest in biomedical applications. Among thousands of MOF structures, the mesoporous iron(III) carboxylate MIL-100(Fe) (MIL stands for the Materials of Lavoisier Institute) is among the most studied MOF nanocarrier, owing to its high porosity, biodegradability, and lack of toxicity. Nanosized MIL-100(Fe) particles (nanoMOFs) readily coordinate with drugs leading to unprecedented payloads and controlled release. Here, we show how the functional groups of the challenging anticancer drug prednisolone influence their interactions with the nanoMOFs and their release in various media. Molecular modeling enabled predicting the strength of interactions between prednisolone-bearing or not phosphate or sulfate moieties (PP and PS, respectively) and the oxo-trimer of MIL-100(Fe) as well as understanding the pore filling of MIL-100(Fe). Noticeably, PP showed the strongest interactions (drug loading up to 30 wt %, encapsulation efficiency > 98%) and slowed down the nanoMOFs' degradation in simulated body fluid. This drug was shown to bind to the iron Lewis acid sites and was not displaced by other ions in the suspension media. On the contrary, PS was entrapped with lower efficiencies and was easily displaced by phosphates in the release media. Noticeably, the nanoMOFs maintained their size and faceted structures after drug loading and even after degradation in blood or serum after losing almost the totality of the constitutive trimesate ligands. Scanning electron microscopy with high annular dark field (STEM-HAADF) in conjunction with X-Ray energy-dispersive spectrometry (XEDS) was a powerful tool enabling the unraveling of the main elements to gain insights on the MOF structural evolution after drug loading and/or upon degradation.

Synthesis and potential applications of cyclodextrin-based metal-organic frameworks: a review

Metal-organic frameworks are porous polymeric materials formed by linking metal ions with organic bridging ligands. Metal-organic frameworks are used as sensors, catalysts for organic transformations, biomass conversion, photovoltaics, electrochemical applications, gas storage and separation, and photocatalysis. Nonetheless, many actual metal-organic frameworks present limitations such as toxicity of preparation reagents and components, which make frameworks unusable for food and pharmaceutical applications. Here, we review the structure, synthesis and properties of cyclodextrin-based metal-organic frameworks that could be used in bioapplications. Synthetic methods include vapor diffusion, microwave-assisted, hydro/solvothermal, and ultrasound techniques. The vapor diffusion method can produce cyclodextrin-based metal-organic framework crystals with particle sizes ranging from 200 nm to 400 μm. Applications comprise food packaging, drug delivery, sensors, adsorbents, gas separation, and membranes. Cyclodextrin-based metal-organic frameworks showed loading efficacy of the bioactive compounds ranging from 3.29 to 97.80%.

Photonic and magnetic materials for on-demand local drug delivery

Nanomedicine has been considered a promising tool for biomedical research and clinical practice in the 21st century because of the great impact nanomaterials could have on human health. The generation of new smart nanomaterials, which enable time- and space-controlled drug delivery, improve the limitations of conventional treatments, such as non-specific targeting, poor biodistribution and permeability. These smart nanomaterials can respond to internal biological stimuli (pH, enzyme expression and redox potential) and/or external stimuli (such as temperature, ultrasound, magnetic field and light) to further the precision of therapies. To this end, photonic and magnetic nanoparticles, such as gold, silver and iron oxide, have been used to increase sensitivity and responsiveness to external stimuli. In this review, we aim to report the main and most recent systems that involve photonic or magnetic nanomaterials for external stimulus-responsive drug release. The uniqueness of this review lies in highlighting the versatility of integrating these materials within different carriers. This leads to enhanced performance in terms of in vitro and in vivo efficacy, stability and toxicity. We also point out the current regulatory challenges for the translation of these systems from the bench to the bedside, as well as the yet unresolved matter regarding the standardization of these materials.

Nanoscale MOFs: From synthesis to drug delivery and theranostics applications

Since the first report in 1989, Metal-Organic Frameworks (MOFs) self-assembled from metal ions or clusters, as well as organic linkers, have attracted extensive attention. Due to their flexible composition, large surface areas, modifiable surface properties, and their degradability, there has been an exponential increase in the study of MOFs materials, specifically in drug delivery system areas such as infection, diabetes, pulmonary disease, ocular disease, imaging, tumor therapy, and especially cancer theranostics. In this review, we discuss the trends in MOFs biosafety, from "green" synthesis to applications in drug delivery systems. Firstly, we present the different "green" synthesis approaches used to prepare MOFs materials. Secondly, we detail the methods for the functional coating, either through grafting targeting units, poly(ethylene glycol) (PEG) chains or by using cell membranes. Then, we discuss drug encapsulation strategies, host-guest interactions, as well as drug release mechanisms. Lastly, we report on the drug delivery applications of nanoscale MOFs. In particular, we discuss MOFs-based imaging techniques, including magnetic resonance imaging (MRI), photoacoustic imaging (PAI), positron emission tomography (PET), and fluorescence imaging. MOFs-based cancer therapy methods are also presented, such as photothermal therapy (PTT), photodynamic therapy (PDT), radiotherapy (RT), chemotherapy, and immunotherapy.

Metal-organic frameworks for pharmaceutical and biomedical applications

Metal-organic framework (MOF) materials provide unprecedented opportunities for evaluating valuable compounds for various medical applications. MOFs merged with biomolecules, used as novel biomaterials, have become particularly useful in biological environments. Bio-MOFs can be promising materials in the global to avoid utilization above toxicological substances. Bio-MOFs with crystallin and porosity nature offer flexible structure via bio-linker and metal node variation, which improves their wide applicability in medical science.

Green synthesis of PEG-coated MIL-100(Fe) for controlled release of dacarbazine and its anticancer potential against human melanoma cells

In this study, the potential of using MIL-100(Fe) metal-organic framework (MOF) for loading and controlling the release of dacarbazine (DTIC) was evaluated for in vitro treatment of melanoma. The drug loading was performed during the green synthesis of MIL-100(Fe) in an aqueous media without using any harmful solvents, to obtain MIL-DTIC. The surface of this structure was then coated with polyethylene glycol (PEG) in the same aqueous solution to synthesize MIL-DTIC-PEG. The synthesized samples were characterized using various methods. Their release profile was studied in phosphate-buffered saline (PBS) and simulated cutaneous medium (SCM). The cytotoxicity of DTIC and its nano-MOF formulation were investigated against melanoma A375 cell lines. The results revealed that the PEG coating (PEGylation) changed the surface charge of MOF from -2.8 ± 0.9 mV to -42.8 ± 1.2 mV, which can contribute to the colloidal stability of MOF. The PEGylation showed a significant effect on controlled drug release, especially in SCM, which increases the complete release time from 60 h to 12 days. Moreover, both of the drug-containing MOFs showed more toxicity than DTIC and unloaded MOFs, confirming that the cumulative release of drug and better cellular uptake of NPs lead to increased toxicity.

Toxicity of metal-organic framework nanoparticles: from essential analyses to potential applications

In the last two decades, the field of metal-organic frameworks (MOFs) has exploded, and MOF nanoparticles in particular are being investigated with increasing interest for various applications, including gas storage and separation, water harvesting, catalysis, energy conversion and storage, sensing, diagnosis, therapy, and theranostics. To further pave their way into real-world applications, and to push the synthesis of MOF nanoparticles that are 'safe-and-sustainable-by-design', this tutorial review aims to shed light on the importance of a systematic toxicity assessment. After clarifying and working out the most important terms and aspects from the field of nanotoxicity, the current state-of-the-art of in vitro and in vivo toxicity studies of MOF nanoparticles is evaluated. Moreover, the key aspects affecting the toxicity of MOF nanoparticles such as their chemical composition, their physico-chemical properties, including their colloidal and chemical stability, are discussed. We highlight the need of more targeted synthesis of MOF nanoparticles that are 'safe-and-sustainable-by-design', and their tailored hazard assessment in the context of their potential applications in order to tap the full potential of this versatile material class in the future.

The Impact of MOF in pH-dependent Drug Delivery System: Progress in Last Decade

Metal-organic frameworks (MOFs) are porous crystalline materials of one-, two-, or three-dimensional networks manufactured from metal ions/clusters and multidentate organic linkers through coordination bonding. MOFs are one of the most...

MCP-1-Functionalized, Core-Shell Gold Nanorod@Iron-Based Metal-Organic Framework (MCP-1/GNR@MIL-100(Fe)) for Photothermal Therapy

The low vessel density and oxygen concentration in hypoxia are the main causes of reduced efficiency of anticancer therapeutics and can stimulate the tumor's relapse. Research showed that macrophages could cross the blood-vessel barriers and reach the hypoxic regions of tumors. Using macrophages in a drug delivery system has been a promising method for tumor targeting in recent years. In this work, we successfully modified monocyte chemoattractant protein-1 (MCP-1) and iron-based metal-organic framework (MIL-100(Fe)) on the photothermal agent, gold nanorods (GNRs) (i.e., MCP-1/GNR@MIL-100(Fe)), to increase cellular uptake and biocompatibility. The results of TEM, UV-vis, and FTIR all confirmed that we'd synthesized MCP-1/GNR@MIL-100(Fe) successfully, and the MCP-1/GNR@MIL-100(Fe) also showed good biocompatibility. A transwell migration assay illustrated that our material attracted macrophages, and the material uptake amount was increased by 1.5 times after MCP-1 functionalization. It also indicated that the macrophages have a tumor-targeting ability. In the in vivo experiment, we subcutaneously implanted U251 MG cells in nude mice as a xenograft model to demonstrate the photothermal activity of MCP-1/GNR@MIL-100(Fe). With successive NIR treatment, the tumor growth could be controlled, and the tumor volume still remained below 100 mm3 after laser treatment. MCP-1/GNR@MIL-100(Fe) combined with the laser treatment showed an excellent antitumor efficacy from the histology of tumor tissues, survival rates, and bioluminescence imaging.

Enhancement of Cancer Chemotherapeutic Efficacy via Bone-Targeted Drug Delivery Carrier in Bone Metastases

Purpose

Bone metastases are common in malignant tumors, especially for the advanced cancers. Chemotherapy is an important treatment in clinic, but the application is limited due to the severe adverse reactions. We try to design bone-targeted drug delivery systems (DDS) for the delivery of chemotherapeutic drugs in bone metastatic carcinoma.

Material and Methods

We added alendronate (Aln) to metal organic framework (MOF) to synthesize a new bone-targeted DDS named Aln-MOF. Doxorubicin (DOX) as a classic anti-cancer drug was encapsulated. The material characterization, drug release and bone affinity were detected. In vitro experiment, the cell toxicity was detected by cck-8 test and cellular uptake were detected by laser scanning confocal microscope and flow cytometry. In vivo experiment, the pharmacokinetics of DDS in the blood was analyzed by fluorescence spectrophotometer and the biodistribution was detected by a multi-mode optical in vivo imaging system. The anti-tumor effects of MOF_DOX and Aln-MOF_DOX were evaluated by monitoring the tumor volume and weight during the animal experiment. In addition, the toxicity of DDS to different organs was determined by HE staining.

Results

Aln-MOF showed good stability, no cytotoxicity and better bone affinity than MOF. Both MOF_DOX and Aln-MOF_DOX could release DOX, and the release rate at pH = 5.5 was faster than the rate at pH = 7.4. The cellular uptake of Aln-MOF and MOF showed no difference. Aln-MOF had a long retention time in blood, which is beneficial for the enrichment of Aln-MOF in tumor sites. Aln-MOF mainly concentrated at bone metastases in mice. MOF_DOX and Aln-MOF_DOX could effectively delay tumor progression, and the effect of Aln-MOFDOX was more obvious (P < 0.05).

Conclusion

Our study confirmed that Aln-MOF has good stability, bone targeting and biosafety. Aln-MOF_DOX could release DOX and effectively kill tumor cells of bone metastases. Aln-MOF_DOX has a promising prospect in the treatment of bone metastasis.

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.

When metal-organic framework mediated smart drug delivery meets gastrointestinal cancers

Cancers of the gastrointestinal tract constitute one of the most common cancer types worldwide and a ∼58% increase in the global number of cases has been estimated by IARC for the next twenty years. Recent advances in drug delivery technologies have attracted scientific interest for developing and utilizing efficient therapeutic systems. The present review focuses on the use of nanoscale MOFs (Nano-MOFs) as carriers for drug delivery and imaging purposes. In pursuit of significant improvements to current gastrointestinal cancer chemotherapy regimens, systems that allow multiple concomitant therapeutic options (polytherapy) and controlled release are highly desirable. In this sense, MOF-based nanotherapeutics represent a significant step towards achieving this goal. Here, the current state-of-the-art of interdisciplinary research and novel developments into MOF-based gastrointestinal cancer therapy are highlighted and reviewed.

Recognition and Sequestration of Toxic Inorganic Water Pollutants with Hydrolytically Stable Metal-Organic Frameworks

Water pollution and crisis of freshwater is one of the most alarming concern globally, which threatens the development and survival of living beings. Recycling of contaminated water has been the prime demand of 21^st century as the area of contamination in natural waterbodies increasing rapidly worldwide. Detoxification and purification of wastewater via adsorptive removal technology has been proven to be more efficient because of it's simplicity, lesser complexity and cost-effectiveness. As the most rapid-growing division of coordination chemistry, porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) with the liberty of crafting tailorable porous architecture and presence of numerous functional sites have become quintessential for recognition and sequestration of water pollutants. This personal account intends to highlight our recent contributions in the field of sensing and sequestration of toxic aquatic inorganic pollutants by functionalized water stable MOFs.

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.

Iron-Based Metal-Organic Frameworks in Drug Delivery and Biomedicine

Metal-organic frameworks (MOFs) are crystalline materials comprising metal centers and organic linkers that feature structural rigidity and functional flexibility. These attractive materials offer large surface areas, high porosity, and good chemical stability; they have shown promise in chemistry (H₂ separation and catalysis), magnetism, and optics. They have also shown potential for drug delivery following the demonstration in 2006 that chromium-based MOFs can be loaded with ibuprofen. Since then, iron-based MOFs (Fe-MOFs) have been shown to offer high drug loading and excellent biocompatibility. The present review focuses on the synthesis and surface modifications of Fe-MOFs as well as their applications in drug delivery and biomedicine.

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.

Metal-Organic Framework Nanocarriers for Drug Delivery in Biomedical Applications

Investigation of metal-organic frameworks (MOFs) for biomedical applications has attracted much attention in recent years. MOFs are regarded as a promising class of nanocarriers for drug delivery owing to well-defined structure, ultrahigh surface area and porosity, tunable pore size, and easy chemical functionalization. In this review, the unique properties of MOFs and their advantages as nanocarriers for drug delivery in biomedical applications were discussed in the first section. Then, state-of-the-art strategies to functionalize MOFs with therapeutic agents were summarized, including surface adsorption, pore encapsulation, covalent binding, and functional molecules as building blocks. In the third section, the most recent biological applications of MOFs for intracellular delivery of drugs, proteins, and nucleic acids, especially aptamers, were presented. Finally, challenges and prospects were comprehensively discussed to provide context for future development of MOFs as efficient drug delivery systems.

Metal-Organic Framework Nanoparticles Induce Pyroptosis in Cells Controlled by the Extracellular pH

Ion homeostasis is essential for cellular survival, and elevated concentrations of specific ions are used to start distinct forms of programmed cell death. However, investigating the influence of certain ions on cells in a controlled way has been hampered due to the tight regulation of ion import by cells. Here, it is shown that lipid-coated iron-based metal-organic framework nanoparticles are able to deliver and release high amounts of iron ions into cells. While high concentrations of iron often trigger ferroptosis, here, the released iron induces pyroptosis, a form of cell death involving the immune system. The iron release occurs only in slightly acidic extracellular environments restricting cell death to cells in acidic microenvironments and allowing for external control. The release mechanism is based on endocytosis facilitated by the lipid-coating followed by degradation of the nanoparticle in the lysosome via cysteine-mediated reduction, which is enhanced in slightly acidic extracellular environment. Thus, a new functionality of hybrid nanoparticles is demonstrated, which uses their nanoarchitecture to facilitate controlled ion delivery into cells. Based on the selectivity for acidic microenvironments, the described nanoparticles may also be used for immunotherapy: the nanoparticles may directly affect the primary tumor and the induced pyroptosis activates the immune system.

Metal-Organic Framework (MOF)-based Nanomaterials for Biomedical Applications

BACKGROUND

Metal-organic frameworks (MOFs), as a new class of porous organic-inorganic crystalline hybrid materials that governed by the self-assembled of metal atoms and organic struts have attracted tremendous attention because of their special properties. Recently, some more documents have reported different types of nanoscale metal-organic frameworks (NMOFs) as biodegradable and physiological pH-responsive systems for photothermal therapy and radiation therapy in the body.

DISCUSSION

In this review paper aims at describing the benefits of using MOF nanoparticles in the field of biomedicine, and putting into perspective their properties in the context of the ones of other NPs. The first section briefly reviews the biomaterial scaffolds of MOFs. The second section presents the main types of stimuli-responsive mechanisms and strategies from two categories: intrinsic (pH, redox state) and extrinsic (temperature, light irradiation and magnetic field) ones. The combinations of photothermal therapy and radiation therapy have been concluded in detail. Finally, clinical applications of MOFs, future challenges and perspectives are also mentioned.

CONCLUSION

This review outlines the most recent advances MOFs design and biomedical applications, from different synthesis to their use as smart drug delivery systems, bioimaging technology or a combination of both.

Coordinative Reduction of Metal Nodes Enhances the Hydrolytic Stability of a Paddlewheel Metal-Organic Framework

Enhancement of hydrolytic stability of metal-organic frameworks (MOFs) is a challenging issue in MOF chemistry because most MOFs have shown limitations in their applications under a humid environment. Meanwhile, inner sphere electron transfer has constituted one of the most intensively studied subjects in contemporary chemistry. In this report, we show, for the first time, a new conceptual coordinative reduction of Cu²⁺ ion, which is realized in a paddlewheel MOF, HKUST-1, with a postsynthetic manner via inner sphere "single" electron transfer from hydroquinone (H₂Q) to Cu²⁺ through its coordination bond. H₂Q treatment of HKUST-1 under anhydrous conditions leads to the single charge (1+) reduction of approximately 30% of Cu²⁺ ions. Thus, this coordinative reduction is an excellent reduction process to be self-controlled in both oxidation state and quantity. As described below, once Cu²⁺ ions are reduced to Cu⁺, the reduction reaction does not proceed further, in terms of their oxidation state as well as their amount. Also, we demonstrate that a half of the Cu⁺ ions (about 15%) remains in paddlewheel framework with pseudo square planar geometry and the other half of the Cu⁺ ions (about 15%) forms [Cu(MeCN)₄]⁺ complex in a small cage in the fashion of a ship-in-a-bottle after dissociation from the framework. Furthermore, we show that the coordinative reduction results in substantial enhancement of the hydrolytic stability of HKUST-1 to the extent that its structure remains intact even after exposure to humid air for two years.

On-Demand Degradation of Metal-Organic Framework Based on Photocleavable Dianthracene-Based Ligand

We have designed a rigid photocleavable dianthracene-based ligand that reacts with ytterbium as coordination metal ion for the creation of a class of tridimensional light-degradable metal-organic framework (MOF). We demonstrated that we can obtain a high level of control on the disassembly of the MOF formed with this ligand which can be triggered either through light irradiation or temperature increase. The reversible 4π-4π photodimerization is the intrinsic chemical mechanism ruling the ligand and MOF cleavage. In the fields of biology and medicine, MOFs have sparked a strong interest as highly porous vehicles for drug release but have only been explored so far through the passive leakage of their payloads. The designed light-degradable MOFs can potentially overcome this limitation and serve as prototypes for drug delivery and corresponding therapeutic applications.

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

Slow and controlled release systems for drugs have attracted increasing interest recently. A highly efficient metal-organic gel (MOGs) drug delivery carrier, i.e., MIL-100(Al) gel, has been fabricated by a facile, low cost, and environmentally friendly one-pot process. The unique structure of MIL-100(Al) gels has led to a high loading efficiency (620 mg/g) towards doxorubicin hydrochloride (DOX) as a kind of anticancer drug. DOX-loaded MOGs exhibited high stability under physiological conditions and sustained release capacity of DOX for up to three days (under acidic environments). They further showed sustained drug release behavior and excellent antitumor effects in in vitro experiments on HeLa cells, in contrast with the extremely low biotoxicity of MOGs. Our work provides a promising way for anticancer therapy by utilizing this MOGs-based drug delivery system as an efficient and safe vehicle.

Cargo delivery on demand from photodegradable MOF nano-cages

We report the photo-induced degradation of and cargo release from a nanoscale metal-organic framework (nMOF) incorporating photo-isomerizable 4,4'-azobenzenedicarboxylate (AZB) linkers. The structure matches a UiO-type framework where 12 4,4'-azobenzenedicarboxylate moieties are connected to a Zr₆O₄(OH)₄ cluster, referred to as UiO-AZB. Due to the incorporation of photo-isomerizable struts, the degradation of UiO-AZB is accelerated by irradiation with white light (1.3 ± 0.1% h^-1 under dark conditions vs. 8.4 ± 0.4% h^-1 when irradiated). Additionally, we show slow release of Nile Red (NR) which is triggered by irradiation (0.04 ± 0.01% h^-1 under dark conditions vs. 0.36 ± 0.02% h^-1 when irradiated).

Photochemistry of Zr-based MOFs: ligand-to-cluster charge transfer, energy transfer and excimer formation, what else is there?

Understanding of the photocatalytic behaviour of Zr-based MOFs is fundamental for the improved design of new and more efficient photocatalysts. The present work describes steady-state and photodynamical studies on the behavior of two MOFs: Zr-2,6-naphthalene dicarboxylate (Zr-NDC) and Zr-4-amino-2,6-naphthalene dicarboxylate (Zr-NADC, 65% NDC/35% NADC) in dichloromethane (DCM) and N,N-dimethylformamide (DMF) suspensions. In the DMF suspension, the Zr-NDC MOF exhibits excimer formation in 280 ps due to the interactions between neighboring linkers. Using the femtosecond transient absorption (fs-TA) technique we have found that the Zr-NADC MOF exhibits a ligand-to-cluster charge transfer (LCCT) event in ∼170 and <100 fs in DMF and DCM, respectively. The Zr-NDC MOF shows similar LCCT in <100 fs in both solvents. The Zr-NADC MOF in DMF suspension shows an energy transfer (ET) from the excited NDC linkers to the NADC ones in 1.1 ps. Flash photolysis experiments demonstrate dominant radiative electron-hole (e^--h⁺) recombination from two different trap states in 310 ns and 1.3 μs, and 32 ns and 1.0 μs in the photoexcited Zr-NADC and Zr-NDC MOFs in DMF, respectively. Excitation of the NDC linkers in the Zr-NADC and Zr-NDC MOFs in DCM allows for the characterization of the dynamics associated with the charge-separated state and the non-radiative recombination from the trap states (45 ns and 0.3 μs). Direct excitation of the NADC linkers (410 nm) in the Zr-NADC MOF in DCM suspension produces a radiative (e^--h⁺) recombination in 3.5 μs. Further experiments in the presence of electron donor (N,N,N',N'-tetramethyl-p-phenylenediamine, TMPD) and acceptor (methyl viologen, MV²⁺) molecules corroborate the formation of charge separated states in these MOFs. These findings are relevant for understanding the photocatalytic and photonic behaviours of these MOFs.

Photonic functional metal–organic frameworks

The recent progress in photonic MOFs for luminescence sensing, white-light emission, photocatalysis, nonlinear optics, lasing devices, and biomedicine is summarized.

Photochemistry and Photophysics in Silica-Based Materials: Ultrafast and Single Molecule Spectroscopy Observation

Silica-based materials (SBMs) are widely used in catalysis, photonics, and drug delivery. Their pores and cavities act as hosts of diverse guests ranging from classical dyes to drugs and quantum dots, allowing changes in the photochemical behavior of the confined guests. The heterogeneity of the guest populations as well as the confinement provided by these hosts affect the behavior of the formed hybrid materials. As a consequence, the observed reaction dynamics becomes significantly different and complex. Studying their photobehavior requires advanced laser-based spectroscopy and microscopy techniques as well as computational methods. Thanks to the development of ultrafast (spectroscopy and imaging) tools, we are witnessing an increasing interest of the scientific community to explore the intimate photobehavior of these composites. Here, we review the recent theoretical and ultrafast experimental studies of their photodynamics and discuss the results in comparison to those in homogeneous media. The discussion of the confined dynamics includes solvation and intra- and intermolecular proton-, electron-, and energy transfer events of the guest within the SBMs. Several examples of applications in photocatalysis, (photo)sensors, photonics, photovoltaics, and drug delivery demonstrate the vast potential of the SBMs in modern science and technology.