Integration of Biomolecules with Metal-Organic Frameworks

Stimuli-responsive metal-organic framework nanoparticles for controlled drug delivery and medical applications

Stimuli-responsive metal-organic framework nanoparticles, NMOFs, provide a versatile platform for the controlled release of drugs and biomedical applications. The porous structure of NMOFs, their biocompatibility, low toxicity, and efficient permeability turn the NMOFs into ideal carriers for therapeutic applications. Two general methods to gate the drug-loaded NMOFs and to release the loads were developed: by one method, the loaded NMOFs are coated or surface-modified with stimuli-responsive gates being unlocked in the presence of appropriate chemical (e.g., ions or reducing agents), physical (e.g., light or heat), or biomarker (e.g., miRNA or ATP) triggers. By a second approach, the drug-loaded NMOFs include encoded structural information or co-added agents to induce the structural distortion or stimulate the degradation of the NMOFs. Different chemical triggers such as pH changes, ions, ATP, or redox agents, and physical stimuli such as light or heat are applied to degrade the NMOFs, resulting in the release of the loads. In addition, enzymes, DNAzymes, and disease-specific biomarkers are used to unlock the gated NMOFs. The triggered release of drugs for cancer therapy, anti-blood clotting, and the design of autonomous insulin-delivery systems ("artificial pancreas") are discussed. Specifically, multi-drug carrier systems and functional NMOFs exhibiting dual and cooperative therapeutic functions are introduced. The future perspectives and applications of stimuli-responsive particles are addressed.

Metal–organic frameworks as photoluminescent biosensing platforms: mechanisms and applications

Recent progress of MOF-based photoluminescent platforms: a comprehensive overview of their applications in biosensing and underlying mechanisms.

Supramolecular chirality in the crystals of mononuclear and polymeric cobalt(ii) complexes with enantiopure and racemic N-thiophosphorylated thioureas

The control of stereochemistry in Co(ii) complexes was provided by additional pyridine and pyrazine ligands. 1D and 2D supramolecular homochiral arrangements in racemic crystals of mononuclear complexes are transferred to their polymeric counterparts.

Multifunctional metal-organic framework heterostructures for enhanced cancer therapy

Metal-organic frameworks (MOFs) are an emerging class of molecular crystalline materials built from metal ions or clusters bridged by organic linkers. By taking advantage of their synthetic tunability and structural regularity, MOFs can hierarchically integrate nanoparticles and/or biomolecules into a single framework to enable multifunctions. The MOF-protected heterostructures not only enhance the catalytic capacity of nanoparticle components but also retain the biological activity of biomolecules in an intracellular microenvironment. Therefore, the multifunctional MOF heterostructures have great advantages over single components in cancer therapy. In this review, we comprehensively summarize the general principle of the design and functional modulation of nanoscaled MOF heterostructures, and biomedical applications in enhanced therapy within the last five years. The functions of MOF heterostructures with a controlled size can be regulated by designing various functional ligands and in situ growth/postmodification of nanoparticles and/or biomolecules. The advances in the application of multifunctional MOF heterostructures are also explored for enhanced cancer therapies involving photodynamic therapy, photothermal therapy, chemotherapy, radiotherapy, immunotherapy, and theranostics. The remaining challenges and future opportunities in this field, in terms of precisely localized assembly, maximizing composite properties, and processing new techniques, are also presented. The introduction of multiple components into one crystalline MOF provides a promising approach to design all-in-one theranostics in clinical treatments.

Fatty acids as biomimetic replication agents for luminescent metal-organic framework patterns

Luminescent metal-organic frameworks (MOFs) are known to spontaneously self-assemble on human fingerprints. Here, we investigate the different chemical components of fingerprints and determine that MOF growth is predominantly induced by insoluble fatty acids. This finding shows that these simple biomolecules can be employed for the precise positioning of luminescent MOFs.

Lysozyme Adsorption on Porous Organic Cages: A Molecular Simulation Study

Recently, porous organic cages (POCs) have emerged as a novel porous material with many merits and are widely utilized in many application fields. In this work, for the first time, molecular dynamics simulations were performed to investigate the mechanism of lysozyme adsorption onto the CC3 crystal, a kind of widely studied POC material. The simulation results show that lysozyme adsorbs onto the surface of CC3 with "top end-on," "back-on," or "side-on" orientations. It is found that the van der Waals interaction is the primary contribution to the binding; the conformation of the lysozyme is well preserved during the adsorption process. This provides some evidence for its biocompatibility and feasibility in biorelated applications. Arginine plays an important role in mediating the adsorption through nonpolar aliphatic chains. More importantly, the distribution and structure of the water layer on the POC surface has a significant impact on adsorption. This study provides insights into the development of POC materials with defined morphologies for the adsorption of biomolecules and may help the rational design of biorelated systems.

Recent Advances in Affinity MOF-Based Sorbents with Sample Preparation Purposes

This review summarizes the recent advances concerning metal-organic frameworks (MOFs) modified with several biomolecules (e.g., amino acids, nucleobases, proteins, antibodies, aptamers, etc.) as ligands to prepare affinity-based sorbents for application in the sample preparation field. The preparation and incorporation strategies of these MOF-based affinity materials were described. Additionally, the different types of ligands that can be employed for the synthesis of these biocomposites and their application as sorbents for the selective extraction of molecules and clean-up of complex real samples is reported. The most important features of the developed biocomposites will be discussed throughout the text in different sections, and several examples will be also commented on in detail.

Interface engineering of zeolite imidazolate framework-8 on two-dimensional Al-metal-organic framework nanoplates enhancing performance for simultaneous capture and sensing tetracyclines

The increasing misgivings of environmental pollution derived from antibiotic residues make it imperative to explore a bifunctional platform for synchronous monitoring and removal of antibiotics. Herein, zeolite imidazolate framework-8 (ZIF-8) is anchored on two-dimensional (2D) amino-functionalized Al-metal organic framework (NH₂-MIL-53(Al)) nanoplates to construct a dual metal-organic frameworks smart platform (ZIF-8/NH₂-MIL-53(Al)) for simultaneous capture and fluorescence sensing of tetracyclines (TCs). ZIF-8 nanoparticles anchored on 2D nanoplates having a smaller size and a larger specific surface area boost the adsorption capabilities (561, 533, 526 and 578 mg g^-1 for doxycycline (DOX), tetracycline (TET), oxytetracycline (OTC) and chlortetracycline (CTC), respectively). Notably, the pyridine N of ZIF-8 cooperated with the abundant NH₂ on the surface of NH₂-MIL-53(Al) exhibits high affinity toward TCs, remarkably enhancing the sensitivity by facilitating the photo-induced electron transfer and the inner-filter effect. The LODs (1.2 μg L^-1 for TET, DOX, OTC and 2.2 μg L^-1 for CTC, respectively) are at least 10-fold lower than those of NH₂-MIL-53(Al) and are comparable or superior to those of reported sensors. The dual metal-organic frameworks smart platform presents satisfactory reliabilities and accuracies for detecting TCs in real samples, which anticipates new routes to develop integrated systems for simultaneous capture and detection of organic pollutants.

Review of the Biomolecular Modification of the Metal-Organ-Framework

Metal-organ frameworks (MOFs), as a kind of novel artificial material, have been widely studied in the field of chemistry. MOFs are capable of high loading capacities, controlled release, plasticity, and biosafety because of their porous structure and have been gradually functionalized as a drug carrier. Recently, a completely new strategy of combining biomolecules, such as oligonucleotides, polypeptides, and nucleic acids, with MOF nanoparticles was proposed. The synthetic bio-MOFs conferred strong protection and endowed the MOFs with particular biological functions. Biomolecular modification of MOFs to form bridges for communication between different subjects has received increased attention. This review will focus on bio-MOFs modification methods and discuss the advantages, applications, prospects, and challenges of using MOFs in the field of biomolecule delivery.

Coordination Polymers Based on Highly Emissive Ligands: Synthesis and Functional Properties

Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4'-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4',4''-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

The Progress and Prospect of Zeolitic Imidazolate Frameworks in Cancer Therapy, Antibacterial Activity, and Biomineralization

The progressive development of zeolitic imidazolate frameworks (ZIFs), as a subfamily of metal-organic frameworks (MOFs), and their unique features, including tunable pore size, large surface area, high thermal stability, and biodegradability/biocompatibility, have made them attractive in the field of biomedicine, especially for drug delivery and biomineralization applications. The high porosity of ZIFs gives them the opportunity for encapsulating a high amount of therapeutic drugs, proteins, imaging cargos, or a combination of them to construct advanced multifunctional drug delivery systems (DDSs) with combined therapeutic and imaging capabilities. This review summarizes recent strategies on the design and fabrication of ZIF-based nansystems and their exploration in the biomedical field. First, recent developments for the adjustment of particle size, functionality, and morphology of ZIFs are discussed, which are important for achieving optimized therapeutic/theranostic nanosystems. Second, recent trends on the application of ZIF nanocarriers for the loading of diverse cargos, including anticancer medicines, antibiotic drugs, enzymes, proteins, photosensitizers, as well as imaging and photothermal agents, are investigated in order to understand how multifunctional DDSs can be designed based on the ZIF nanoparticles to treat different diseases, such as cancer and infection. Finally, prospects on the future research direction and applications of ZIF-based nanomedicines are discussed.

Metal-Organic Framework Composites for Theragnostics and Drug Delivery Applications

Among a plethora of nano-sized therapeutics, metal-organic frameworks (MOFs) have been some of the most investigated novel materials for, predominantly, cancer drug delivery applications. Due to their large drug uptake capacities and slow-release mechanisms, MOFs are desirable drug delivery vehicles that protect and transport sensitive drug molecules to target sites. The inclusion of other guest materials into MOFs to make MOF-composite materials has added further functionality, from externally triggered drug release to improved pharmacokinetics and diagnostic aids. MOF-composites are synthetically versatile and can include examples such as magnetic nanoparticles in MOFs for MRI image contrast and polymer coatings that improve the blood-circulation time. From synthesis to applications, this review will consider the main developments in MOF-composite chemistry for biomedical applications and demonstrate the potential of these novel agents in nanomedicine. It is concluded that, although vast synthetic progress has been made in the field, it requires now to develop more biomedical expertise with a focus on rational model selection, a major comparative toxicity study, and advanced targeting techniques.

Smart Biomimetic Nanocomposites Mediate Mitochondrial Outcome through Aerobic Glycolysis Reprogramming: A Promising Treatment for Lymphoma

Toxicity and drug resistance caused by chemotherapeutic drugs have become bottlenecks in treating tumors. The delivery of anticancer drugs based on nanocarriers is regarded as an ideal way to solve the aforementioned problems. In this study, a new antilymphoma nanodrug CD20 aptamer-RBCm@Ag-MOFs/PFK15 (A-RAMP) is designed and constructed, and it consists of two parts: (1) metal-organic frameworks Ag-MOFs (AM) loaded with tumor aerobic glycolysis inhibitor PFK15 (P), forming a core part (AMP); (2) targeted molecule CD20 aptamer (A) is inserted into the red blood cell membrane (RBCm) to form the shell part (A-R). A-RAMP under the guidance of CD20 aptamer actively targets B-cell lymphoma both in vitro and in vivo. As a result, A-RAMP not only significantly inhibits the effect on tumor growth but also shows no obvious side effects on the treated nude mice, indicating that A-RAMP can accurately target tumor cells, reprogram aerobic glycolysis, and exert synergistic antitumor effect by Ag⁺ and PFK 15. Furthermore, the antitumor mechanism of A-RAMP in vivo by apoptotic pathway and targeting metabonomics are explored. These results suggest that A-RAMP has a promising application prospect as an smart, safe, effective, and synergistic antilymphoma agent.

Multimodal Enzyme Delivery and Therapy Enabled by Cell Membrane-Coated Metal-Organic Framework Nanoparticles

Therapeutic enzymes used for genetic disorders or metabolic diseases oftentimes suffer from suboptimal pharmacokinetics and stability. Nanodelivery systems have shown considerable promise for improving the performance of enzyme therapies. Here, we develop a cell membrane-camouflaged metal-organic framework (MOF) system with enhanced biocompatibility and functionality. The MOF core can efficiently encapsulate enzymes while maintaining their bioactivity. After the introduction of natural cell membrane coatings, the resulting nanoformulations can be safely administered in vivo. The surface receptors on the membrane can also provide additional functionalities that synergize with the encapsulated enzyme to target disease pathology from multiple dimensions. Employing uricase as a model enzyme, we demonstrate the utility of this approach in multiple animal disease models. The results support the use of cell membrane-coated MOFs for enzyme delivery, and this strategy could be leveraged to improve the usefulness of enzyme-based therapies for managing a wide range of important human health conditions.

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 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.

Targeted gene silencing in vivo by platelet membrane-coated metal-organic framework nanoparticles

Small interfering RNA (siRNA) is a powerful tool for gene silencing that has been used for a wide range of biomedical applications, but there are many challenges facing its therapeutic use in vivo. Here, we report on a platelet cell membrane-coated metal-organic framework (MOF) nanodelivery platform for the targeted delivery of siRNA in vivo. The MOF core is capable of high loading yields, and its pH sensitivity enables endosomal disruption upon cellular uptake. The cell membrane coating provides a natural means of biointerfacing with disease substrates. It is shown that high silencing efficiency can be achieved in vitro against multiple target genes. Using a murine xenograft model, significant antitumor targeting and therapeutic efficacy are observed. Overall, the biomimetic nanodelivery system presented here provides an effective means of achieving gene silencing in vivo and could be used to expand the applicability of siRNA across a range of disease-relevant applications.

Metal-Organic Framework Preserves the Biorecognition of Antibodies on Nanoscale Surfaces Validated by Single-Molecule Force Spectroscopy

Antibody biorecognition forms the basis for numerous biomedical applications such as diagnostic assays, targeted drug delivery, and targeted cancer imaging. However, antibodies, especially after being conjugated to surfaces or nanostructures, suffer from stability issues when stored under nonrefrigeration conditions. Therefore, enhancing the stability of antibodies on surfaces and nanostructures under ambient and elevated temperatures is of paramount importance for many nanobiotechnology applications. In this study, we introduce a simple and facile approach based on a metal-organic framework (MOF) coating to preserve the biorecognition capability of antibodies immobilized on nanoscale surfaces after exposure to elevated temperatures for a prolonged period. By using atomic force microscopy (AFM)-based force spectroscopy, we demonstrate that the MOF coating is able to preserve the binding force and binding frequency of the anti-CD-146 antibody attached to an AFM tip to CD-146 antigen on the surface of melanoma cells at the single-molecule level. We also demonstrate that the MOF coating outperforms another commonly used sucrose coatings in terms of maintaining the binding force and binding frequency of the antibody to antigen. Herein, the AFM tip functionalized with antibodies provides a nanoscale testbed (analogous to an antibody-conjugated nanostructure) to assess antibody biorecognition at the single-molecule level and preservation efficacy under antibody denaturing conditions. This MOF coating approach should be applicable to the preservation of a variety of antibody-conjugated nanostructures aiming for targeted drug delivery, targeted cancer imaging, and nanobiosensors. The improved stability and elimination of refrigeration requirements will facilitate wide applications of antibody-enabled nanobiotechnology in resource-limited environments and populations.

Highly Sensitive Biosensors Based on Biomolecules and Functional Nanomaterials Depending on the Types of Nanomaterials: A Perspective Review

Biosensors are very important for detecting target molecules with high accuracy, selectivity, and signal-to-noise ratio. Biosensors developed using biomolecules such as enzymes or nucleic acids which were used as the probes for detecting the target molecules were studied widely due to their advantages. For example, enzymes can react with certain molecules rapidly and selectively, and nucleic acids can bind to their complementary sequences delicately in nanoscale. In addition, biomolecules can be immobilized and conjugated with other materials by surface modification through the recombination or introduction of chemical linkers. However, these biosensors have some essential limitations because of instability and low signal strength derived from the detector biomolecules. Functional nanomaterials offer a solution to overcome these limitations of biomolecules by hybridization with or replacing the biomolecules. Functional nanomaterials can give advantages for developing biosensors including the increment of electrochemical signals, retention of activity of biomolecules for a long-term period, and extension of investigating tools by using its unique plasmonic and optical properties. Up to now, various nanomaterials were synthesized and reported, from widely used gold nanoparticles to novel nanomaterials that are either carbon-based or transition-metal dichalcogenide (TMD)-based. These nanomaterials were utilized either by themselves or by hybridization with other nanomaterials to develop highly sensitive biosensors. In this review, highly sensitive biosensors developed from excellent novel nanomaterials are discussed through a selective overview of recently reported researches. We also suggest creative breakthroughs for the development of next-generation biosensors using the novel nanomaterials for detecting harmful target molecules with high sensitivity.

Defect-induced activity enhancement of enzyme-encapsulated metal-organic frameworks revealed in microfluidic gradient mixing synthesis

Mimicking the cellular environment, metal-organic frameworks (MOFs) are promising for encapsulating enzymes for general applications in environments often unfavorable for native enzymes. Markedly different from previous researches based on bulk solution synthesis, here, we report the synthesis of enzyme-embedded MOFs in a microfluidic laminar flow. The continuously changed concentrations of MOF precursors in the gradient mixing on-chip resulted in structural defects in products. This defect-generating phenomenon enables multimodal pore size distribution in MOFs and therefore allows improved access of substrates to encapsulated enzymes while maintaining the protection to the enzymes. Thus, the as-produced enzyme-MOF composites showed much higher (~one order of magnitude) biological activity than those from conventional bulk solution synthesis. This work suggests that while microfluidic flow synthesis is currently underexplored, it is a promising strategy in producing highly active enzyme-MOF composites.

Glucose oxidase and Au nanocluster co-encapsulated metal–organic frameworks as a sensitive colorimetric sensor for glucose based on a cascade reaction

The GOx & AuNCs@ZIF-8 composite was simply obtained as a colorimetric glucose sensor with high sensitivity and selectivity and long-term storage stability.

Recent developments on zinc(ii) metal-organic framework nanocarriers for physiological pH-responsive drug delivery

The high storage capacities and excellent biocompatibilities of zinc(ii) metal-organic frameworks (Zn-MOFs) have made them outstanding candidates as drug delivery carriers. Recent studies on the pH-responsive processes based on carrier-drug interactions have proven them to be the most efficient and effective way to control the release profiles of drugs. To satisfy the ever-growing demand in cancer therapy, great efforts are being devoted to the development of methods to precisely control drug release and achieve targeted use of an active substance at the right time and place. In this review article, we discuss the diverse stimuli based on Zn-MOFs carriers that have been achieved upon external activation from single pH-stimulus-responsive or/and multiple pH-stimuli-responsive viewpoints. Also, the perspectives and future challenges in this type of carrier system are discussed.

Engineering of Nanoscale Coordination Polymers with Biomolecules for Advanced Applications

Nanoscale coordination polymers (NCPs) have shown extraordinary advantages in various research areas due to their structural diversity and multifunctionality. Recently, integration of biomolecules with NCPs received extensive attention and the formed hybrid materials exhibit superior properties over the individual NCPs or biomolecules. In this review, the state-of-the-art of approaches to engineer NCPs with different types of guest biomolecules, such as amino acids, nucleic acids, enzymes and lipids are systematically introduced. Additionally, advanced applications of these biomolecule-NCP composites in the areas of sensing, catalysis, molecular imaging and therapy are thoroughly summarized. Finally, current challenges and prospects are also discussed.

Metal-Organic Frameworks in Polymer Science: Polymerization Catalysis, Polymerization Environment, and Hybrid Materials

The development of metal-organic frameworks (MOFs) has had a significant impact on various fields of chemistry and materials science. Naturally, polymer science also exploited this novel type of material for various purposes, which is due to the defined porosity, high surface area, and catalytic activity of MOFs. The present review covers various topics of MOF/polymer research beginning with MOF-based polymerization catalysis. Furthermore, polymerization inside MOF pores as well as polymerization of MOF ligands is described, which have a significant effect on polymer structures. Finally, MOF/polymer hybrid and composite materials are highlighted, encompassing a range of material classes, like bulk materials, membranes, and dispersed materials. In the course of the review, various applications of MOF/polymer combinations are discussed (e.g., adsorption, gas separation, drug delivery, catalysis, organic electronics, and stimuli-responsive materials). Finally, past research is concluded and an outlook toward future development is provided.

Encapsulation of Plasmid DNA by Nanoscale Metal-Organic Frameworks for Efficient Gene Transportation and Expression

The intracellular delivery and functionalization of genetic molecules play critical roles in gene-based theranostics. In particular, the delivery of plasmid DNA (pDNA) with safe nonviral vectors for efficient intracellular gene expression has received increasing attention; however, it still has some limitations. A facile one-pot method is employed to encapsulate pDNA into zeolitic imidazole framework-8 (ZIF-8) and ZIF-8-polymer vectors via biomimetic mineralization and coprecipitation. The pDNA molecules are found to be well distributed inside both nanostructures and benefit from their protection against enzymatic degradation. Moreover, through the use of a polyethyleneimine (PEI) 25 kD capping agent, the nanostructures exhibit enhanced loading capacity, better pH responsive release, and stronger binding affinity to pDNA. From in vitro experiments, the cellular uptake and endosomal escape of the protected pDNA are greatly improved with the superior ZIF-8-PEI 25 kD vector, leading to successful gene expression with high transfection efficacy, comparable to expensive commercial agents. New cost-effective avenues to develop metal-organic-framework-based nonviral vectors for efficient gene delivery and expression are provided.

In Situ Loading and Delivery of Short Single- and Double-Stranded DNA by Supramolecular Organic Frameworks

Short DNA represents an important class of biomacromolecules that are widely applied in gene therapy, editing, and modulation. However, the development of simple and reliable methods for their intracellular delivery remains a challenge. Herein, we describe that seven water-soluble, homogeneous supramolecular organic frameworks (SOFs) with a well-defined pore size and high stability in water that can accomplish in situ inclusion of single-stranded (ss) and double-stranded (ds) DNA (21, 23, and 58 nt) and effective intracellular delivery (including two noncancerous and six cancerous cell lines). Fluorescence quenching experiments for single and double end-labeled ss- and ds-DNA support that the DNA sequences can be completely enveloped by the SOFs. Confocal laser scanning microscopy and flow cytometry reveal that five of the SOFs exhibit excellent delivery efficiencies that, in most of the studied cases, outperform the commercial standard Lipo2000, even at low SOF–nucleic acid ratios. In addition to high delivery efficiencies, the water-soluble, self-assembled SOF carriers have a variety of advantages, including convenient preparation, high stability, and in situ DNA inclusion, which are all critical for practical applications in nucleic acid delivery.

MOF-Based Nanotubes to Hollow Nanospheres through Protein-Induced Soft-Templating Pathways

A controllable and facile strategy is established for constructing metal-organic frameworks-based (MOF-based) hollow composites via a protein-induced soft-templating pathway. Using metal-sodium deoxycholate hydrogel as soft-template, nanotubes are gained while the protein is absent. With the presence of protein, hollow nanospheres structure are prepared by changing the amount of protein. To verify the universality of the proposed pathway, two kinds of proteins (Burkholderia cepacia lipase and penicillin G acylase) and three kinds of MOF (ZIF-8, ZIF-67, and Fe-MOF) are adopted as model proteins and materials, and the obtained protein-containing composites (named protein@H-MOF) possess high bioactivity and stability. This proposed strategy provides a facile method for preparing MOF-based composites under mild conditions, facilitating the applications of MOF in the fields of biocatalyst construction, biomolecule encapsulation, and drug delivery.

A novel approach for the synthesis of phospholipid bilayer-coated zeolitic imidazolate frameworks: preparation and characterization as a pH-responsive drug delivery system

The first example of enveloping of the ZIF family by PLB as an effective biodegradable/biocompatible/responsive drug delivery system.

Encapsulation of collagenase within biomimetically mineralized metal–organic frameworks: designing biocomposites to prevent collagen degradation

Collagen-degrading enzyme induced rapid formation of a metal–organic framework (ZIF-8) as a protective shell, which afforded the control of the enzyme's bioactivity.

Cyclodextrin-Based Metal-Organic Frameworks (CD-MOFs) in Pharmaceutics and Biomedicine

Metal-organic frameworks (MOFs) show promising application in biomedicine and pharmaceutics owing to their extraordinarily high surface area, tunable pore size, and adjustable internal surface properties. However, MOFs are prepared from non-renewable or toxic materials, which limit their real-world applications. Cyclodextrins (CDs) are a typical natural and biodegradable cyclic oligosaccharide and are primarily used to enhance the aqueous solubility, safety, and bioavailability of drugs by virtue of its low toxicity and highly flexible structure, offering a peculiar ability to form CD/drug inclusions. A sophisticated strategy where CD is deployed as a ligand to form an assembly of cyclodextrin-based MOFs (CD-MOFs) may overcome real-world application drawbacks of MOFs. CD-MOFs incorporate the porous features of MOFs and the encapsulation capability of CD for drug molecules, leading to outstanding properties when compared with traditional hybrid materials. This review focuses on the inclusion technology and drug delivery properties associated with CD-MOFs. In addition, synthetic strategies and currently developed uses of CD-MOFs are highlighted as well. Also, perspectives and future challenges in this rapidly developing research area are discussed.

Metal-Organic Framework Encapsulation Preserves the Bioactivity of Protein Therapeutics

Protein therapeutics are prone to lose their structure and bioactivity under various environmental stressors. This study reports a facile approach using a nanoporous material, zeolitic imidazolate framework-8 (ZIF-8), as an encapsulant for preserving the prototypic protein therapeutic, insulin, against different harsh conditions that may be encountered during storage, formulation, and transport, including elevated temperatures, mechanical agitation, and organic solvent. Both immunoassay and spectroscopy analyses demonstrate the preserved chemical stability and structural integrity of insulin offered by the ZIF-8 encapsulation. Biological activity of ZIF-8-preserved insulin after storage under accelerated degradation conditions (i.e., 40 °C) is evaluated in vivo using a diabetic mouse model, and shows comparable bioactivity to refrigeration-stored insulin (-20 °C). It is also demonstrated that ZIF-8-preserved insulin has low cytotoxicity in vitro and does not cause side effects in vivo. Furthermore, ZIF-8 residue can be completely removed by a simple purification step before insulin administration. This biopreservation approach is potentially applicable to diverse protein therapeutics, thus extending the benefits of advanced biologics to resource-limited settings and underserved populations/regions.

MOF/polymer composite synthesized using a double solvent method offers enhanced water and CO2 adsorption properties

A double solvent method is for the first time used to synthesize a polymer composite that is constructed by a Ni-pyrazolate MOF and polydopamine (PDA). The resulting composite shows significantly enhanced water and CO₂ adsorption properties compared to the parent MOF and the composite synthesized without the double solvent method.

Integrated Antibody with Catalytic Metal-Organic Framework for Colorimetric Immunoassay

Enzyme-linked immunosorbent assay has been widely used as a gold standard in biomedical field, but some inevitable drawbacks still exist in its practical applications, especially the laborious preparation of enzyme-antibody conjugates by a covalent linkage. In this work, we proposed a new strategy to prepare enzyme-antibody conjugate by integrating antibody with catalytic metal-organic framework (MOF) to form dual-functional MOF/antibody composite. As models, rabbit antimouse immunoglobulin G antibody (RIgG) and Cu-MOF with peroxidase-like activity were used to fabricate RIgG@Cu-MOF composite for colorimetric immunoassay. It was found that Cu-MOF as a host not only has no influence on the original capture ability of RIgG to its corresponding antigen (mIgG), but also can shield RIgG against long-term storage, high temperature, and biological degradation. More importantly, upon the formation of sandwiched immunocomplex between RIgG@Cu-MOF and capture antibody, Cu-MOF can serve as a signal amplification unit to perform colorimetric immunoassay. The detection limit of RIgG@Cu-MOF toward mIgG was obtained at 0.34 ng/mL, which is 3-fold lower than that of horseradish peroxidase labeled RIgG. Furthermore, the successful determination of mIgG in serum sample demonstrates the applicability of RIgG@Cu-MOF in detecting real sample. Therefore, it is highly anticipated that this study can offer a new way to prepare enzyme-antibody conjugates, facilitating the exploration of MOF composites in biomedical field.