A Low Cytotoxic Cationic Metal–Organic Framework Carrier for Controllable Drug Release

Application and progress of 3D printed biomaterials in osteoporosis

Osteoporosis results from a disruption in skeletal homeostasis caused by an imbalance between bone resorption and bone formation. Conventional treatments, such as pharmaceutical drugs and hormone replacement therapy, often yield suboptimal results and are frequently associated with side effects. Recently, biomaterial-based approaches have gained attention as promising alternatives for managing osteoporosis. This review summarizes the current advancements in 3D-printed biomaterials designed for osteoporosis treatment. The benefits of biomaterial-based approaches compared to traditional systemic drug therapies are discussed. These 3D-printed materials can be broadly categorized based on their functionalities, including promoting osteogenesis, reducing inflammation, exhibiting antioxidant properties, and inhibiting osteoclast activity. 3D printing has the advantages of speed, precision, personalization, etc. It is able to satisfy the requirements of irregular geometry, differentiated composition, and multilayered structure of articular osteochondral scaffolds with boundary layer structure. The limitations of existing biomaterials are critically analyzed and future directions for biomaterial-based therapies are considered.

Neutral and ionic Co(II) metal-organic frameworks with 2-methylimidazole and trimesate: design and evaluation for molecule encapsulation and slow release

Two Co(II) mixed-ligand metal-organic frameworks (MOFs) based on 2-methylimidazole and trimesate were synthesised at room temperature. The structure and properties of the two MOFs, named material Deutsches Elektronen Synchrotron-1 and -2 (mDESY-1 and mDESY-2), were verified by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), SQUID magnetic susceptibility and N2 adsorption. The structural analysis indicates that mDESY-1 is a 3D ionic framework with 2-methyl-1H-imidazol-3-ium counterions residing in its pores, while mDESY-2 is a 2D neutral framework isostructural to ITH-1, with water as a co-crystallising solvent. PXRD data demonstrates that mDESY-1 exhibits better crystallinity than mDESY-2. Magnetic measurements indicate that both MOFs are paramagnetic with a weak ferromagnetic transition above room temperature. Although both structures suggest the presence of voids, N2 adsorption data confirms that these voids are not accessible in either MOF. Nevertheless, mDESY-1 was capable of encapsulating azobenzene during synthesis, which was observed via SCXRD. The encapsulated molecules were then slowly released in ethanol, with a release of up to 30 mg of azobenzene per g of MOF in a period of 60 days.

Exploring Synthesis Strategies and Interactions between MOFs and Drugs for Controlled Drug Loading and Release, Characterizing Interactions through Advanced Techniques

This study explores various aspects of Metal-Organic Frameworks (MOFs), focusing on synthesis techniques to adjust pore size and key ligands and metals for crafting carrier MOFs. It investigates MOF-drug interactions, including hydrogen bonding, van der Waals, and electrostatic interactions, along with kinetic studies. The multifaceted applications of MOFs in drug delivery systems are elucidated. The morphology and structure of MOFs are intricately linked to synthesis methodology, impacting attributes like crystallinity, porosity, and surface area. Hydrothermal synthesis yields MOFs with high crystallinity, suitable for catalytic applications, while solvothermal synthesis generates MOFs with increased porosity, ideal for gas and liquid adsorption. Understanding MOF-drug interactions is crucial for optimizing drug delivery, affecting charge capacity, stability, and therapeutic efficacy. Kinetic studies determine drug release rates and uniformity, vital for controlled drug delivery. Overall, comprehending drug-MOF interactions and kinetics is essential for developing effective and controllable drug delivery systems.

Integrated design and application of stimuli-responsive metal-organic frameworks in biomedicine: current status and future perspectives

In recent years, metal-organic frameworks (MOFs) have garnered widespread attention due to their distinctive attributes, such as high surface area, tunable properties, biodegradability, extremely low density, high loading capacity, diverse chemical functionalities, thermal stability, well-defined pore sizes, and molecular dimensions. Increasingly, biomedical researchers have turned their focus towards their multifaceted development. Among these, stimuli-responsive MOFs, with their unique advantages, have captured greater interest from researchers. This review will delve into the merits and drawbacks of both endogenous and exogenous stimuli-responsive MOFs, along with their application directions. Furthermore, it will outline the characteristics of different synthesis routes of MOFs, exploring various design schemes and modification strategies and their impacts on the properties of MOF products, as well as how to control them. Additionally, we will survey different types of stimuli-responsive MOFs, discussing the significance of various MOF products reported in biomedical applications. We will categorically summarize different strategies such as anticancer therapy, antibacterial treatment, tissue repair, and biomedical imaging, as well as insights into the development of novel MOFs nanomaterials in the future. Finally, this review will conclude by summarizing the challenges in the development of stimuli-responsive MOFs in the field of biomedicine and providing prospects for future research endeavors.

Recent advances in metal-organic frameworks for stimuli-responsive drug delivery

After entering the human body, drugs for treating diseases, which are prone to delivery and release in an uncontrolled manner, are affected by various factors. Based on this, many researchers utilize various microenvironmental changes encountered during drug delivery to trigger drug release and have proposed stimuli-responsive drug delivery systems. In recent years, metal-organic frameworks (MOFs) have become promising stimuli-responsive agents to release the loaded therapeutic agents at the target site to achieve more precise drug delivery due to their high drug loading, excellent biocompatibility, and high stimuli-responsiveness. The MOF-based stimuli-responsive systems can respond to various stimuli under pathological conditions at the site of the lesion, releasing the loaded therapeutic agent in a controlled manner, and improving the accuracy and safety of drug delivery. Due to the changes in different physical and chemical factors in the pathological process of diseases, the construction of stimuli-responsive systems based on MOFs has become a new direction in drug delivery and controlled release. Based on the background of the rapidly increasing attention to MOFs applied in drug delivery, we aim to review various MOF-based stimuli-responsive drug delivery systems and their response mechanisms to various stimuli. In addition, the current challenges and future perspectives of MOF-based stimuli-responsive drug delivery systems are also discussed in this review.

γ-Cyclodextrin metal-organic frameworks as the promising carrier for pulmonary delivery of cyclosporine A

γ-Cyclodextrin metal-organic frameworks (CD-MOFs) are considered as a green and biocompatible material with great potential in drug delivery systems. Original CD-MOFs show the poor aerosol properties, which limit the application in pulmonary drug delivery. To improve the in vitro deposition properties, herein, we synthesized CD-MOFs by the vapor diffusion method using a series of modulators to achieve better pulmonary delivery of cyclosporine A (CsA). The results showed that blank CD-MOFs and drug loaded CD-MOFs prepared with different modulators all preserved the cubical shape, and exhibited the similar crystal form, structural characteristics, thermal behaviors and release properties. In addition, drug loaded CD-MOFs prepared with polyethylene glycol 10000 (PEG 10000) as a modulator exhibited better in vitro aerosol performance than those of synthesized using other modulators, and the in vivo pharmacokinetics data demonstrated that the bioavailability of CsA could be significantly enhanced by inhalation administration of drug loaded CD-MOFs compared with oral administration of Neoral®. The repeated dose inhalation toxicity also confirmed the fine biocompatibility of CD-MOFs as the carrier for pulmonary drug delivery. Therefore, the results demonstrated CD-MOFs as the promising carrier could be used for pulmonary drug delivery.

Recent Advances in Metallic Nanostructures-assisted Biosensors for Medical Diagnosis and Therapy

The field of nanotechnology has witnessed remarkable progress in recent years, particularly in its application to medical diagnosis and therapy. Metallic nanostructures-assisted biosensors have emerged as a powerful and versatile platform, offering unprecedented opportunities for sensitive, specific, and minimally invasive diagnostic techniques, as well as innovative therapeutic interventions. These biosensors exploit the molecular interactions occurring between biomolecules, such as antibodies, enzymes, aptamers, or nucleic acids, and metallic surfaces to induce observable alterations in multiple physical attributes, encompassing electrical, optical, colorimetric, and electrochemical signals. These interactions yield measurable data concerning the existence and concentration of particular biomolecules. The inherent characteristics of metal nanostructures, such as conductivity, plasmon resonance, and catalytic activity, serve to amplify both sensitivity and specificity in these biosensors. This review provides an in-depth exploration of the latest advancements in metallic nanostructures-assisted biosensors, highlighting their transformative impact on medical science and envisioning their potential in shaping the future of personalized healthcare.

Environmental implications of metal-organic frameworks and MXenes in biomedical applications: a perspective

Metal-organic frameworks (MOFs) and MXenes have demonstrated immense potential for biomedical applications, offering a plethora of advantages. MXenes, in particular, exhibit robust mechanical strength, hydrophilicity, large surface areas, significant light absorption potential, and tunable surface terminations, among other remarkable characteristics. Meanwhile, MOFs possess high porosity and large surface area, making them ideal for protecting active biomolecules and serving as carriers for drug delivery, hence their extensive study in the field of biomedicine. However, akin to other (nano)materials, concerns regarding their environmental implications persist. The number of studies investigating the toxicity and biocompatibility of MXenes and MOFs is growing, albeit further systematic research is needed to thoroughly understand their biosafety issues and biological effects prior to clinical trials. The synthesis of MXenes often involves the use of strong acids and high temperatures, which, if not properly managed, can have adverse effects on the environment. Efforts should be made to minimize the release of harmful byproducts and ensure proper waste management during the production process. In addition, it is crucial to assess the potential release of MXenes into the environment during their use in biomedical applications. For the biomedical applications of MOFs, several challenges exist. These include high fabrication costs, poor selectivity, low capacity, the quest for stable and water-resistant MOFs, as well as difficulties in recycling/regeneration and maintaining chemical/thermal/mechanical stability. Thus, careful consideration of the biosafety issues associated with their fabrication and utilization is vital. In addition to the synthesis and manufacturing processes, the ultimate utilization and fate of MOFs and MXenes in biomedical applications must be taken into account. While numerous reviews have been published regarding the biomedical applications of MOFs and MXenes, this perspective aims to shed light on the key environmental implications and biosafety issues, urging researchers to conduct further research in this field. Thus, the crucial aspects of the environmental implications and biosafety of MOFs and MXenes in biomedicine are thoroughly discussed, focusing on the main challenges and outlining future directions.

Innovative Metal-Organic Frameworks for Targeted Oral Cancer Therapy: A Review

Metal-organic frameworks (MOFs) have proven to be very effective carriers for drug delivery in various biological applications. In recent years, the development of hybrid nanostructures has made significant progress, including developing an innovative MOF-loaded nanocomposite with a highly porous structure and low toxicity that can be used to fabricate core-shell nanocomposites by combining complementary materials. This review study discusses using MOF materials in cancer treatment, imaging, and antibacterial effects, focusing on oral cancer cells. For patients with oral cancer, we offer a regular program for accurately designing and producing various anticancer and antibacterial agents to achieve maximum effectiveness and the lowest side effects. Also, we want to ensure that the anticancer agent works optimally and has as few side effects as possible before it is tested in vitro and in vivo. It is also essential that new anticancer drugs for cancer treatment are tested for efficacy and safety before they go into further research.

Review on Additives in Hydrogels for 3D Bioprinting of Regenerative Medicine: From Mechanism to Methodology

The regeneration of biological tissues in medicine is challenging, and 3D bioprinting offers an innovative way to create functional multicellular tissues. One common way in bioprinting is bioink, which is one type of the cell-loaded hydrogel. For clinical application, however, the bioprinting still suffers from satisfactory performance, e.g., in vascularization, effective antibacterial, immunomodulation, and regulation of collagen deposition. Many studies incorporated different bioactive materials into the 3D-printed scaffolds to optimize the bioprinting. Here, we reviewed a variety of additives added to the 3D bioprinting hydrogel. The underlying mechanisms and methodology for biological regeneration are important and will provide a useful basis for future research.

Design of hydrotalcite and biopolymers entrapped tunable cerium organic cubic hybrid material for superior fluoride adsorption

The excess fluoride in drinking water is serious risk which leads to fluorosis. The adsorption method is facile route for defluoridation studies. Hybrid adsorbent possesses unique advantages like high surface area and high stability has been employed for water treatment. In the present work, hydrotalcite (HT) fabricated Ce-metal organic frameworks (MOFs) bridged with biopolymers (alginate and chitosan) namely HT-CeMOFs@Alg-CS cubic hybrid beads was developed and employed towards fluoride removal in batch mode. The fabricated HT-CeMOFs@Alg-CS beads were analyzed by DTA, FTIR, SEM, EDAX, TGA and XRD studies. Besides, FTIR and EDAX proved the affinity of HT-CeMOFs@Alg-CS cubic hybrid beads on fluoride was majorly attributed by electrostatic interaction, ion-exchange and complexation mechanism. To include detail insight into adsorption route; the kinetics, thermodynamic and isotherm studies were investigated for fluoride adsorption. The equilibrium data of HT-CeMOFs@Alg-CS cubic hybrid beads for fluoride adsorption was fitted with Langmuir isotherm model. Thermodynamic investigation results demonstrated that the fluoride adsorption was spontaneous with endothermic nature. The regeneration and field investigation results revealed that the developed HT-CeMOFs@Alg-CS cubic hybrid beads are reusable and more apt at field environment.

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.

BioMOF-Based Anti-Cancer Drug Delivery Systems

A variety of nanomaterials have been developed specifically for biomedical applications, such as drug delivery in cancer treatment. These materials involve both synthetic and natural nanoparticles and nanofibers of varying dimensions. The efficacy of a drug delivery system (DDS) depends on its biocompatibility, intrinsic high surface area, high interconnected porosity, and chemical functionality. Recent advances in metal-organic framework (MOF) nanostructures have led to the achievement of these desirable features. MOFs consist of metal ions and organic linkers that are assembled in different geometries and can be produced in 0, 1, 2, or 3 dimensions. The defining features of MOFs are their outstanding surface area, interconnected porosity, and variable chemical functionality, which enable an endless range of modalities for loading drugs into their hierarchical structures. MOFs, coupled with biocompatibility requisites, are now regarded as highly successful DDSs for the treatment of diverse diseases. This review aims to present the development and applications of DDSs based on chemically-functionalized MOF nanostructures in the context of cancer treatment. A concise overview of the structure, synthesis, and mode of action of MOF-DDS is provided.

Metal-organic frameworks as chemical nanoreactors for the preparation of catalytically active metal compounds

Since the emergence of metal-organic frameworks (MOFs), a myriad of thrilling properties and applications, in a wide range of fields, have been reported for these materials, which mainly arise from their porous nature and rich host-guest chemistry. However, other important features of MOFs that offer great potential rewards have been only barely explored. For instance, despite the fact that MOFs are suitable candidates to be used as chemical nanoreactors for the preparation, stabilization and characterization of unique functional species, that would be hardly accessible outside the functional constrained space offered by MOF channels, only very few examples have been reported so far. In particular, we outline in this feature recent advances in the use of highly robust and crystalline oxamato- and oxamidato-based MOFs as reactors for the in situ preparation of well-defined catalytically active single atom catalysts (SACS), subnanometer metal nanoclusters (SNMCs) and supramolecular coordination complexes (SCCs). The robustness of selected MOFs permits the post-synthetic (PS) in situ preparation of the desired catalytically active metal species, which can be characterised by single-crystal X-ray diffraction (SC-XRD) taking advantage of its high crystallinity. The strategy highlighted here permits the always challenging large-scale preparation of stable and well-defined SACs, SNMCs and SCCs, exhibiting outstanding catalytic activities.

An ionic Fe-based metal-organic-framework with 4'-pyridyl-2,2':6',2''-terpyridine for catalytic hydroboration of alkynes

An ionic metal-organic-framework (MOF) containing nanoscale channels was readily assembled from ditopic 4'-pyridyl-2,2':6',2''-terpyridine (pytpy) and a simple iron(ii) salt. X-ray structural analysis revealed a two-dimensional grid-like framework assembled by classic octahedral (pytpy)2FeII cations as linkers (with pytpy as a new ditopic pyridyl ligand) and octa-coordinate FeCl2 centers as nodes. The layer-by-layer assembly of the 2-D framework resulted in the formation of 3-D porous materials consisting of nano-scale channels. The charges of the cationic framework were balanced with anionic Cl3FeOFeCl3 in its void channels. The new Fe-based MOF material was employed as a precatalyst for syn-selective hydroboration of alkynes under mild, solvent-free conditions in the presence of an activator, leading to the synthesis of a range of trans-alkenylboronates in good yields. The larger scale applicability and recyclability of the new MOF catalyst was further explored. This represents a rare example of an ionic MOF material that can be utilized in hydroboration catalysis.

Exploring the Physicochemical, Electroactive, and Biodelivery Properties of Metal Nanoparticles on Peripheral Nerve Regeneration

Despite the advances in the regeneration/rehabilitation field of damaged tissues, the functional recovery of peripheral nerves (PNs), especially in a long gap injury, is considered a great medical challenge. Recent progress in nanomedicine has provided great hope for PN regeneration through the strategy of controlling cell behavior by metal nanoparticles individually or loaded on scaffolds/conduits. Despite the confirmed toxicity of metal nanoparticles due to long-term accumulation in nontarget tissues, they play a role in the damaged PN regeneration based on the topography modification of scaffolds/conduits, enhancing neurotrophic factor secretion, the ion flow improvement, and the regulation of electrical signals. Determining the fate of neural progenitor cells would be a major achievement in PN regeneration, which seems to be achievable by metal nanoparticles through altering cell vital approaches and controlling their functions. Therefore, in this literature, an attempt was made to provide an overview of the effective activities of metal nanoparticles on the PN regeneration, until the vital clues of the PN regeneration and how they are changed by metal nanoparticles are revealed to the researcher.

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.

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.

Metal-Organic Frameworks as Unique Platforms to Gain Insight of σ-Hole Interactions for the Removal of Organic Dyes from Aquatic Ecosystems

The combination of high crystallinity and rich host-guest chemistry in metal-organic frameworks (MOFs), have situated them in an advantageous position, with respect to traditional porous materials, to gain insight on specific weak noncovalent supramolecular interactions. In particular, sulfur σ-hole interactions are known to play a key role in the biological activity of living beings as well as on relevant molecular recognitions processes. However, so far, they have been barely explored. Here, we describe both how the combination of the intrinsic features of MOFs, especially the possibility of using single-crystal X-ray crystallography (SCXRD), can be an extremely valuable tool to gain insight on sulfur σ-hole interactions, and how their rational exploitation can be enormously useful in the efficient removal of harmful organic molecules from aquatic ecosystems. Thus, we have used a MOF, prepared from the amino acid L-methionine and possessing channels decorated with -CH2 CH2 SCH3 thioalkyl chains, to remove a family of organic dyes at very low concentrations (10 ppm) from water. This MOF is able to efficiently capture the four dyes in a very fast manner, reaching within five minutes nearly the maximum removal. Remarkably, the crystal structure of the different organic dyes within MOFs channels could be determined by SCXRD. This has enabled us to directly visualize the important role sulfur σ-hole interactions play on the removal of organic dyes from aqueous solutions, representing one of the first studies on the rational exploitation of σ-hole interactions for water remediation.

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.

A biocompatible bismuth based metal-organic framework as efficient light-sensitive drug carrier

The low toxicity and good photo active property endow bismuth based metal-organic frameworks (MOFs) potential candidates for efficient light-sensitive drug carrier. In this work, SU-101, composed of Bi and ellagic acid (EA), is found to display high ciprofloxacin (CIP) loading ratio (85.8%) and controlled CIP release under light illumination (the maximum CIP release ratio is 95.56%). Further investigations suggest that hydrogen bond between the CO group in EA and the -OH group in CIP is responsible for above behavior. Light irradiation decreases the electron density around the CO group in EA, which consequently leads to the broken of the hydrogen bond and therefore the release of CIP. Further investigations suggest that SU-101 is universal for other drugs, such as norfloxacin (NOR), amoxicillin (AMO), tetracycline (TET) and doxorubicinhydrochloride (DOX), since all of them can form hydrogen bond with SU-101. This work suggests that SU-101 holds great potential as efficient light-sensitive drug carrier, and the investigation of other Bi based MOFs as drug carrier is under investigation.

A novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold with enhanced osteoporotic osseointegration through osteoimmunomodulation

Background

Femoral stem of titanium alloy has been widely used for hip arthroplasty with considerable efficacy; however, the application of this implant in patients with osteoporosis is limited due to excessive bone resorption. Macrophages participate in the regulation of inflammatory response and have been a topic of increasing research interest in implant field. However, few study has explored the link between macrophage polarization and osteogenic–osteoclastic differentiation. The present study aims to develop a novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold with enhanced osteoporotic osseointegration through immunotherapy.

Method

To improve the osteointegration under osteoporosis, we developed a hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold (PT). Biomimetic extracellular matrix (ECM) was constructed inside the interconnected pores of PT in micro-scale. And in nano-scale, a drug cargo icariin@Mg-MOF-74 (ICA@MOF) was wrapped in ECM-like structure that can control release of icariin and Mg²⁺.

Results

In this novel hierarchical biofunctionalized 3D-printed porous Ti6Al4V scaffold, the macroporous structure provides mechanical support, the microporous structure facilitates cell adhesion and enhances biocompatibility, and the nanostructure plays a biological effect. We also demonstrate the formation of abundant new bone at peripheral and internal sites after intramedullary implantation of the biofunctionalized PT into the distal femur in osteoporotic rats. We further find that the controlled-release of icariin and Mg²⁺ from the biofunctionalized PT can significantly improve the polarization of M0 macrophages to M2-type by inhibiting notch1 signaling pathway and induce the secretion of anti-inflammatory cytokines; thus, it significantly ameliorates bone metabolism, which contributes to improving the osseointegration between the PT and osteoporotic bone.

Conclusion

The therapeutic potential of hierarchical PT implants containing controlled release system are effective in geriatric orthopaedic osseointegration.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01277-0.

A nanosized anionic MOF with rich thiadiazole groups for controlled oral drug delivery

Controlling the crystal size and surface chemistry of MOF materials, and understanding their multifunctional effect are of great significance for the biomedical applications of MOF systems. Herein, we designed and synthesized a new anionic MOF, ZJU-64-NSN, which features 1D channels decorated with highly polarized thiadiazole groups, and its crystal size could be systematically tuned from 200 ​μm to 300 ​nm through a green and simple approach. As a result, the optimal nanosized ZJU-64-NSN is found to enable an ultrafast loading of cationic drug procainamide (PA) (21.2 ​wt% within 1 ​min). Moreover, the undesirable chemical stability of PA@ZJU-64-NSN is greatly improved by the surface coating of polyethylene glycol (PEG) biopolymer. The final drug delivery system PEG/PA@ZJU-64-NSN is found to effectively prevent PA from premature release under the harsh stomach environments due to the intense host-guest interaction, and mainly release PA to the targeted intestinal surroundings. Such controlled drug delivery is proved to be triggered by endogenic Na⁺ ions instead of H⁺ ions, well revealed by the study on the dynamics behavior of drug release and UV–Vis absorption spectrum. Good biocompatibility of ZJU-64-NSN and PEG-coated ZJU-64-NSN has been fully demonstrated by MTT assay as well as confocal microscopy imaging.

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A new anionic MOF enables an ultrafast drug loading.

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The crystal size of such MOF could be well size-controlled.

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The surface coating of PEG improves the chemical stability of drug carrier.

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The drug delivery system reveals an endogenic Na ​⁺ ​-triggered procainamide release.

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.

Metal-Organic Framework (MOF)-Based Biomaterials for Tissue Engineering and Regenerative Medicine

The synthesis of Metal-organic Frameworks (MOFs) and their evaluation for various applications is one of the largest research areas within materials sciences and chemistry. Here, the use of MOFs in biomaterials and implants is summarized as narrative review addressing primarely the Tissue Engineering and Regenerative Medicine (TERM) community. Focus is given on MOFs as bioactive component to aid tissue engineering and to augment clinically established or future therapies in regenerative medicine. A summary of synthesis methods suitable for TERM laboratories and key properties of MOFs relevant to biomaterials is provided. The use of MOFs is categorized according to their targeted organ (bone, cardio-vascular, skin and nervous tissue) and whether the MOFs are used as intrinsically bioactive material or as drug delivery vehicle. Further distinction between in vitro and in vivo studies provides a clear assessment of literature on the current progress of MOF based biomaterials. Although the present review is narrative in nature, systematic literature analysis has been performed, allowing a concise overview of this emerging research direction till the point of writing. While a number of excellent studies have been published, future studies will need to clearly highlight the safety and added value of MOFs compared to established materials for clinical TERM applications. The scope of the present review is clearly delimited from the general 'biomedical application' of MOFs that focuses mainly on drug delivery or diagnostic applications not involving aspects of tissue healing or better implant integration.

Polymer-Coated NH2-UiO-66 for the Codelivery of DOX/pCRISPR

Herein, the NH₂-UiO-66 metal organic framework (MOF) has been green synthesized with the assistance of high gravity to provide a suitable and safe platform for drug loading. The NH₂-UiO-66 MOF was characterized using a field-emission scanning electron microscope, transmission electron microscope (TEM), X-ray diffraction, and zeta potential analysis. Doxorubicin was then encapsulated physically on the porosity of the green MOF. Two different stimulus polymers, p(HEMA) and p(NIPAM), were used as the coating agents of the MOFs. Doxorubicin was loaded onto the polymer-coated MOFs as well, and a drug payload of more than 51% was obtained, which is a record by itself. In the next step, pCRISPR was successfully tagged on the surface of the modified MOFs, and the performance of the final nanosystems were evaluated by the GFP expression. In addition, successful loadings and internalizations of doxorubicin were investigated via confocal laser scanning microscopy. Cellular images from the HeLa cell line for the UiO-66@DOX@pCRISPR and GMA-UiO-66@DOX@pCRISPR do not show any promising and successful gene transfections, with a maximum EGFP of 1.6%; however, the results for the p(HEMA)-GMA-UiO-66@DOX@pCRISPR show up to 4.3% transfection efficiency. Also, the results for the p(NIPAM)-GMA-UiO-66@DOX@pCRISPR showed up to 6.4% transfection efficiency, which is the first and superior report of a MOF-based nanocarrier for the delivery of pCRISPR. Furthermore, the MTT assay does not shown any critical cytotoxicity, which is a promising result for further biomedical applications. At the end of the study, the morphologies of all of the nanomaterials were screened after drug and gene delivery procedures and showed partial degradation of the nanomaterial. However, the cubic structure of the MOFs has been shown in TEM, and this is further proof of the stability of these green MOFs for biomedical 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.

Versatile Nanoscale Metal-Organic Frameworks (nMOFs): An Emerging 3D Nanoplatform for Drug Delivery and Therapeutic Applications

For decades, nanoscale metal-organic frameworks (nMOFs) have attracted extensive interest in biomedicine due to their distinct characteristics, including facile synthesis, porous interior, and tunable biocompatibility. With high porosity, versatile nMOFs allow for the facile encapsulation of various therapeutic agents with exceptionally high payloads. Constructed from metal ions and organic linkers through coordination bonds, nMOFs with plentiful functional groups enable the surface modification for active targeting and enhanced biocompatibility. This review outlines the up-to-date progresses on the exploration of nMOFs in the field of biomedicine. First, the classification and synthesis of nMOFs are discussed, followed by the concrete introduction of drug loading strategies of nMOFs and mechanisms of stimulation-responsive drug release. Second, the smart designs of the nMOFs-based platforms for anticancer and antibacterial treatment are summarized. Finally, the basic challenges faced by nMOFs research and the great potential of biomimetic nMOFs are presented. This review article affords an inspiring insight into the interdisciplinary research of nMOFs and their biomedical applications, which holds great expectation for their further clinical translation.

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.

Recent advances in nanosized metal organic frameworks for drug delivery and tumor therapy

Metal organic-frameworks (MOFs) are novel materials that have attracted increasing attention for applications in a wide range of research, owing to their unique advantages including their small particle size, porous framework structure and high specific surface area. Because of their adjustable size, nanoscale MOFs (nano-MOFs) can be prepared as carriers of biotherapy drugs, thus enabling biotherapeutic applications. Nano-MOFs' metal ion catalytic activity and organic group functional characteristics can be exploited in biological treatments. Furthermore, the applications of nano-MOFs can be broadened by hybridization with other materials to form composites. This review focuses on the preparation and recent advances in nano-MOFs as drug carriers, therapeutic materials and functionalized materials in drug delivery and tumor therapy based on the single/multiple stimulus response of drug release to achieve the targeted therapy, offering a comprehensive reference for drug carrier design. At the end, the current challenges and prospects are discussed to provide significant insight into the design and applications of nano-MOFs in drug delivery and tumor therapy.

Architectural and catalytic aspects of designer materials built using metalloligands of pyridine-2,6-dicarboxamide based ligands

This perspective presents the design, synthesis and crystal structures of a large number of architectures constructed using assorted metalloligands of pyridine-2,6-dicarboxamide based ligands. The metalloligands offered various appended functional groups, whereas design strategies included varying both their position and number. A combination of these parameters resulted in the development of assorted architectures including discrete trinuclear and tetranuclear complexes as well as 1D/2D/3D coordination polymers. The metalloligand strategy not only assisted in the construction of ordered crystalline materials with varied dimensionalities but also judiciously allowed the incorporation of Lewis acidic and redox-active secondary metals in the resultant architectures. As a result, such designer architectures illustrated their noteworthy role both as homogenous and heterogeneous catalysts in different organic transformation reactions.

Optimizing ibuprofen concentration for rapid pharmacokinetics on biocompatible zinc-based MOF-74 and UTSA-74

Metal-organic frameworks (MOFs) have potential as drug carriers on the basis of their surface areas and pore volumes that allow for high loading and fast release. This study investigated two biocompatible MOFs - Zn MOF-74 and UTSA-74 - for ibuprofen delivery. The effect of drug loading was studied by impregnating the MOFs with 30, 50, and 80 wt% ibuprofen. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and N₂ physisorption. From SEM, the MOF structures were maintained at 30 wt% ibuprofen, however, became agglomerated at 50-80 wt% loading, as the drug deposited on the surface and adhered the particles to one another. In the physisorption measurements, the Zn MOF-74 samples decreased in surface area with ibuprofen loading, until they became zero at 80 wt%. In UTSA-74, the drug impregnation was less effective, as 35% of the original surface area was retained in the 80 wt% sample. On the basis of our drug release measurements, 50 wt% ibuprofen loading was found to be optimal on Zn MOF-74, as it gave rise to fast kinetics (k = 0.27 h^-1/2) and high drug concentrations within the first 10 h. In UTSA-74, the fastest release rate was observed at 30 wt% loading (k = 0.22 h^-1/2), as the poor impregnation efficiency blocked diffusion through the MOF pores at higher loading. Color changes of phosphate buffer saline (PBS) solutions at different time intervals also suggested that Zn MOF-74 decomposed during drug release, as it produced yellowing of the PBS solution. On the other hand, UTSA-74 did not discolor the PBS solution, and was concluded to not have dissolved during drug release. From these results, it was concluded that Zn MOF-74 was the superior drug carrier, as it could effectively deliver higher ibuprofen loadings and would dissolve in the process of drug release, thereby reducing its invasiveness in the human body.

Development of High-Drug-Loading Nanoparticles

Formulating drugs into nanoparticles offers many attractive advantages over free drugs including improved bioavailability, minimized toxic side effects, enhanced drug delivery, feasibility of incorporating other functions such as controlled release, imaging agents for imaging, targeting delivery, and loading more than one drug for combination therapies. One of the key parameters is drug loading, which is defined as the mass ratio of drug to drug-loaded nanoparticles. Currently, most nanoparticle systems have relatively low drug loading (<10 wt%), and developing methods to increase drug loading remains a challenge. This Minireview presents an overview of recent research on developing nanoparticles with high drug loading (>10 wt%) from the perspective of synthesis strategies, including post-loading, co-loading, and pre-loading. Based on these three different strategies, various nanoparticle systems with different materials and drugs are summarized and discussed in terms of their synthesis methods, drug loadings, encapsulation efficiencies, release profiles, stabilities, and their applications in drug delivery. The advantages and disadvantages of these strategies are presented with an objective of providing useful design rules for future development of high-drug-loading nanoparticles.

In Situ Biomimetic Mineralization on ZIF-8 for Smart Drug Delivery

The exploration of metal-organic frameworks (MOFs) with good biocompatibility and physiological stability as carrier platforms for biomedical applications is of great importance but remains challenging. Herein, we developed an in situ biomimetic mineralization strategy on zeolitic imidazolate framework (ZIF) nanocrystals to construct a drug release system with favorable cytocompatibility, improved stability, and pH responsiveness. With lysozyme (Lys) wrapped on the surface of Zn-based ZIF (ZIF-8), Lys/ZIF-8 could strongly bond metal ions to promote nucleation and growth of bone-like hydroxyapatite (HAp), leading to formation of HAp@Lys/ZIF-8 composites. In vitro investigations indicate that the composites with a hollow Lys/ZIF-8 core and a HAp shell exhibited a high drug-loading efficiency (56.5%), smart pH-responsive drug delivery, cytocompatibility, and stability under physiological conditions. The proposed biomimetic mineralization strategy for designing MOFs-based composites may open a new avenue to construct advanced delivery systems in the biomedical field.

Antibody Targeted Metal-Organic Frameworks for Bioimaging Applications

We report on the availability and chemical utility of primary amines within metal-organic frameworks (MOFs) for cell targeting. Primary amine groups represent one of the most versatile chemical moieties for conjugation to biologically relevant molecules, including antibodies and enzymes. Specifically, we used two different chemical conjugations schemes, utilizing the amino functionality on the organic linker: first, carbodiimide chemistry was used to link the primary amine to available carboxyl groups on the protein neutravidin; second, sulfhydryl cross-linking chemistry was used via Traut's reagent scheme. Importantly, this is the first report that documents this methodology implemented with MOF systems. Finally, the ability of the EpCAM antibody targeted MOFs to bind to a human epithelial cell line (A549), a common target for imaging studies, was confirmed with confocal microscopy.

Highly Stable Lanthanide Metal-Organic Framework as an Internal Calibrated Luminescent Sensor for Glutamic Acid, a Neuropathy Biomarker

Glutamic acid (Glu) is the most abundant excitatory neurotransmitter in the central nervous system, and an elevated level of Glu may indicate some neuropathological diseases. Herein, three isomorphic microporous lanthanide metal-organic frameworks (MOFs) [(CH₃)₂NH₂]₂[Ln₆(μ₃-OH)₈(BDC-OH)₆(H₂O)₆]·(solv)_x (ZJU-168; ZJU = Zhejiang University, H₂BDC-OH = 2-hydroxyterephthalic acid, Ln = Eu, Tb, Gd) were designed for the detection of Glu. ZJU-168(Eu) and ZJU-168(Tb) suspensions simultaneously produce the characteristic emission bands of both lanthanide ions and ligands. When ZJU-168(Eu) and ZJU-168(Tb) suspensions exposed to Glu, the fluorescence intensity of ligands increases while the emission of lanthanide ions is almost unchanged. By utilizing the emission of ligands as the detected signal and the emission of lanthanide ions as the internal reference, an internal calibrated fluorescence sensor for Glu was obtained. There is a good linear relationship between fluorescence intensity ratio and Glu concentration in a wide range with the detection limit of 3.6 μM for ZJU-168(Tb) and 4.3 μM for ZJU-168(Eu). Major compounds present in blood plasma have no interference for the detection of Glu. Furthermore, a convenient analytical device based on a one-to-two logic gate was constructed for monitoring Glu. These establish ZJU-168(Tb) as a potential turn-on, ratiometric, and colorimetric fluorescent sensor for practical detection of Glu.

Metal-Organic Frameworks for Biomedical Applications

Metal-organic frameworks (MOFs) are an interesting and useful class of coordination polymers, constructed from metal ion/cluster nodes and functional organic ligands through coordination bonds, and have attracted extensive research interest during the past decades. Due to the unique features of diverse compositions, facile synthesis, easy surface functionalization, high surface areas, adjustable porosity, and tunable biocompatibility, MOFs have been widely used in hydrogen/methane storage, catalysis, biological imaging and sensing, drug delivery, desalination, gas separation, magnetic and electronic devices, nonlinear optics, water vapor capture, etc. Notably, with the rapid development of synthetic methods and surface functionalization strategies, smart MOF-based nanocomposites with advanced bio-related properties have been designed and fabricated to meet the growing demands of MOF materials for biomedical applications. This work outlines the synthesis and functionalization and the recent advances of MOFs in biomedical fields, including cargo (drugs, nucleic acids, proteins, and dyes) delivery for cancer therapy, bioimaging, antimicrobial, biosensing, and biocatalysis. The prospects and challenges in the field of MOF-based biomedical materials are also discussed.

Metal–organic frameworks: a future toolbox for biomedicine?

The present review focuses on the use of Metal–Organic Frameworks, (MOFs) highlighting the most recent developments in the biological field and as bio-sensors.

Synthesis and Functionalization of Porous Zr-Diaminostilbenedicarboxylate Metal-Organic Framework for Storage and Stable Delivery of Ibuprofen

A stable porous metal-organic framework (MOF), Zr-diaminostilbenedicarboxylate (Zr-DASDCA), was synthesized and modified with oxalyl chloride (OC) or terephthaloyl chloride (TC) to introduce various functional groups onto the Zr-DASDCA. Both pristine and functionalized Zr-DASDCAs, together with activated carbon, were used as a potential carrier for ibuprofen (IBU) storage and delivery. Zr-DASDCAs, especially the modified ones (OC-Zr-DASDCA and TC-Zr-DASDCA), showed competitive results in IBU delivery. Specifically, the release rate in phosphate-buffered saline solution at pH 7.4 was nearly constant (R 2 ≈ 0.98) for up to 10 days, which would be very effective in IBU dosing to the human body. Moreover, the release rate could be controlled by changing the pH of the releasing solution. The rate of IBU release from both pristine and modified Zr-DASDCAs at pH 7.4 and 3.0 was also explained with a few interactions such as H-bonding and electrostatic repulsion, together with the relative pore size of the Zr-DASDCAs. Therefore, the results suggested that functionalization of MOFs via postsynthetic modification, especially with OC and TC, to introduce various functional groups onto MOFs is an effective approach to not only reducing the release rate of IBU but also inducing a constant release of IBU for as long as 10 days.

Facile Method To Prepare a Novel Biological HKUST-1@CMCS with Macroscopic Shape Control for the Long-Acting and Sustained Release

We have developed a green and versatile method to prepare hierarchically porous Cu₃(BTC)₂@carboxymethyl chitosan (HKUST-1@CMCS) with a macroscopic shape control and designable performance via the cross-linking of Cu(II) ions with CMCS. Furthermore, atomic force microscopy, scanning electron microscopy, powder X-ray diffraction, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy analyses showed that the morphology of HKUST-1 could be controlled and changed by tailoring the surface roughness ( R_q) of polymer matrix. For the ball-like, fiberlike, and membrane-like composites, the matrix R_q values were 887, 88.4, and 18.2 nm and the average sizes of HKUST-1 crystals were about 10.2, 5.9, and 1.7 μm, respectively. It was found that the larger the R_q of the polymer matrix, the higher the drug payload. The results of drug release showed that the release percentage of dimethyl fumarate from HKUST-1@CMCS was 66% in 326 h, whereas that of Cu@CMCS was only 12 h. Obviously, the HKUST-1@CMCS had a long-acting and sustained release property compared to that of Cu@CMCS due to its complementary advantages of metal-organic frameworks (MOFs) and polymers. Therefore, this study not only provided an interesting way to make up for the shortcomings of MOFs and natural polymer but also developed a long-acting delivery system for a huge potential application prospect.