Integration of Biomolecules with Metal-Organic Frameworks

Fabricating oxygen self-supplying 3D printed bioactive hydrogel scaffold for augmented vascularized bone regeneration

Limited cells and factors, inadequate mechanical properties, and necrosis of defects center have hindered the wide clinical application of bone-tissue engineering scaffolds. Herein, we construct a self-oxygenated 3D printed bioactive hydrogel scaffold by integrating oxygen-generating nanoparticles and hybrid double network hydrogel structure. The hydrogel scaffold possesses the characteristics of extracellular matrix; Meanwhile, the fabricated hybrid double network structure by polyacrylamide and CaCl2-crosslinked sodium carboxymethylcellulose endows the hydrogel favorable compressive strength and 3D printability. Furthermore, the O2 generated by CaO2 nanoparticles encapsulated in ZIF-8 releases steadily and sustainably because of the well-developed microporous structure of ZIF-8, which can significantly promote cell viability and proliferation in vitro, as well as angiogenesis and osteogenic differentiation with the assistance of Zn2+. More significantly, the synergy of O2 and 3D printed pore structure can prevent necrosis of defects center and facilitate cell infiltration by providing cells the nutrients and space they need, which can further induce vascular network ingrowth and accelerate bone regeneration in all areas of the defect in vivo. Overall, this work provides a new avenue for preparing cell/factor-free bone-tissue engineered scaffolds that possess great potential for tissue regeneration and clinical alternative.

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.

DNA-induced assembly of biocatalytic nanocompartments for sensitive and selective aptasensing of aflatoxin B1

Enzyme cascade with high specificity and catalytic efficiency has significant applications for developing efficient bioanalysis methods. In this work, a sensitive and selective aptasensor was constructed based on the DNA-induced assembly of biocatalytic nanocompartments. Different from the conventional co-immobilization in one pot, the cascade enzymes of glucose oxidase (GOX) and horseradish peroxidase (HRP) were separately encapsulated in ZIF-90 nanoparticles. After conjugating complementary DNA or aptermer on enzyme@ZIF-90, DNA hybridization drove enzyme@ZIF-90 connected into clusters or linked on other DNA modified biocatalytic nanocompartment (such as invertase loaded Fe3O4@SiO2). Owing to the shortened distance between enzymes, the catalytic efficiency of connected clusters was significantly enhanced. However, the specifically interaction between the substrate molecule and aptermer sequence would lead to the disassembly of DNA duplexes, resulting in the gradual "switching-off" of cascade reactions. With aflatoxin B1 (AFB1) as the model substrate, the compartmentalized three-enzyme nanoreactors showed good analytical performance in the linear range from 0.01 ng mL-1 to 50 ng mL-1 with a low detection limit (3.3 pg mL-1). In addition, the proposed aptasensor was applied to detect AFB1 in corn oil and wheat powder samples with total recoveries ranging from 94 % to 109 %. As a result, this DNA-induced strategy for enzyme cascade nanoreactors opens new avenues for stimuli-responsive applications in biosensing.

Biomedical application of metal-organic frameworks (MOFs) in cancer therapy: Stimuli-responsive and biomimetic nanocomposites in targeted delivery, phototherapy and diagnosis

The nanotechnology is an interdisciplinary field that has become a hot topic in cancer therapy. Metal-organic frameworks (MOFs) are porous materials and hybrid composites consisted of organic linkers and metal cations. Despite the wide application of MOFs in other fields, the potential of MOFs for purpose of cancer therapy has been revealed by the recent studies. High surface area and porosity, significant drug loading and encapsulation efficiency are among the benefits of using MOFs in drug delivery. MOFs can deliver genes/drugs with selective targeting of tumor cells that can be achieved through functionalization with ligands. The photosensitizers and photo-responsive nanostructures including carbon dots and gold nanoparticles can be loaded in/on MOFs to cause phototherapy-mediated tumor ablation. The immunogenic cell death induction and increased infiltration of cytotoxic CD8+ and CD4+ T cells can be accelerated by MOF platforms in providing immunotherapy of tumor cells. The stimuli-responsive MOF platforms responsive to pH, redox, enzyme and ion can accelerate release of therapeutics in tumor site. Moreover, MOF nanocomposites can be modified ligands and green polymers to improve their selectivity and biocompatibility for cancer therapy. The application of MOFs for the detection of cancer-related biomarkers can participate in the early diagnosis of patients.

Zirconium-Based Metal-Organic Framework Capable of Binding Proinflammatory Mediators in Hydrogel Form Promotes Wound Healing Process through a Multiscale Adsorption Mechanism

The regulation of proinflammatory mediators has been explored to promote natural healing without abnormal inflammation or autoimmune response induced by their overproduction. However, most efforts to control these mediators have relied on pharmacological substances that are directly engaged in biological cycles. It is believed that functional porous materials removing target mediators provide a new way to promote the healing process using their adsorption mechanisms. In this study, the Zr-based metal-organic frameworks (MOF)-808 (Zr6 O4 (OH)4 (BTC)2 (HCOO)6 ) crystals are found to be effective at removing proinflammatory mediators, such as nitric oxide (NO), cytokines, and reactive oxygen species (ROS) in vitro and in vivo, because of their porous structure and surface affinity. The MOF-808 crystals are applied to an in vivo skin wound model as a hydrogel dispersion. Hydrogel containing 0.2 wt% MOF-808 crystals shows significant improvement in terms of wound healing efficacy and quality over the corresponding control. It is also proven that the mode of action is to remove the proinflammatory mediators in vivo. Moreover, the application of MOF-808-containing hydrogels promotes cell activation, proliferation and inhibits chronic inflammation, leading to increased wound healing quality. These findings suggest that Zr-based MOFs may be a promising drug-free solution for skin problems related to proinflammatory mediators.

Engineering poly(ethylene glycol) particles for targeted drug delivery

Poly(ethylene glycol) (PEG) is considered to be the "gold standard" among the stealth polymers employed for drug delivery. Using PEG to modify or engineer particles has thus gained increasing interest because of the ability to prolong blood circulation time and reduce nonspecific biodistribution of particles in vivo, owing to the low fouling and stealth properties of PEG. In addition, endowing PEG-based particles with targeting and drug-loading properties is essential to achieve enhanced drug accumulation at target sites in vivo. In this feature article, we focus on recent work on the synthesis of PEG particles, in which PEG is the main component in the particles. We highlight different synthesis methods used to generate PEG particles, the influence of the physiochemical properties of PEG particles on their stealth and targeting properties, and the application of PEG particles in targeted drug delivery.

Biomolecules meet organic frameworks: from synthesis strategies to diverse applications

Biomolecules are essential in pharmaceuticals, biocatalysts, biomaterials, etc., but unfortunately they are extremely susceptible to extraneous conditions. When biomolecules meet porous organic frameworks, significantly improved thermal, chemical, and mechanical stabilities are not only acquired for raw biomolecules, but also molecule sieving, substrate enrichment, chirality property, and other functionalities are additionally introduced for application expansions. In addition, the intriguing synergistic effect stemming from elaborate and concerted interactions between biomolecules and frameworks can further enhance application performances. In this paper, the synthesis strategies of the so-called bio-organic frameworks (BOFs) in recent years are systematically reviewed and classified. Additionally, their broad applications in biomedicine, catalysis, separation, sensing, and imaging are introduced and discussed. Before ending, the current challenges and prospects in the future for this infancy-stage but significant research field are also provided. We hope that this review will offer a concise but comprehensive vision of designing and constructing multifunctional BOF materials as well as their full explorations in various fields.

In-situ green synthesis of copper tannic acid framework in the presence of graphene quantum dots: Improved colloidal and antibacterial properties

This work reports the preparation of a copper tannic acid MOF (CuTA) and graphene quantum dot (GQD) nanocomposite, GQD/CuTA, by a simple, environmentally friendly, and inexpensive method with exceptionally enhanced antibacterial properties. To end this, GQDs were first fabricated from citric acid using a neoteric, simple and straightforward hydrolysis approach and followed by they effectively anchor MOF nanoparticles (CuTA) by a green hydrothermal in situ synthesizing method. The constructed GQD/CuTA nanomaterials were characterized and validated using XRD, FT-IR, TEM, DLS, UV-vis, and PL techniques. Significant antibacterial activity against E. coli bacteria for both CuTA and GQD/CuTA (0 CFU/mL) and S. aureus bacteria for CuTA and GQD/CuTA (300 and 40 CFU/mL) was observed for the GQD/CuTA nanocomposite. The MTT assay showed good cytocompatibility for the GQD/CuTA nanocomposite against human dermal fibroblast cells (HFF-2). The result suggests that the synthesized GQD/CuTA nanocomposite with improved colloidal and antibacterial properties has the potential to be used as a safe photoluminescent nanoplatform with strong antimicrobial activity.

Reprogramming mitochondrial metabolism of macrophages by miRNA-released microporous coatings to prevent peri-implantitis

Although various new biomaterials have enriched the methods for peri-implant inflammation treatment, their efficacy is still debated, and secondary operations on the implant area have also caused pain for patients. Recently, strategies that regulate macrophage polarization to prevent or even treat peri-implantitis have attracted increasing attention. Here, we prepared a laser-drilled and covered with metal organic framework-miR-27a agomir nanomembrane (L-MOF-agomir) implant, which could load and sustain the release of miR-27a agomir. In vitro, the L-MOF-agomir titanium plate promoted the repolarization of LPS-stimulated macrophages from M1 to M2, and the macrophage culture supernatant promoted BMSCs osteogenesis. In a ligation-induced rat peri-implantitis model, the L-MOF-agomir implants featured strong immunomodulatory activity of macrophage polarization and alleviated ligation-induced bone resorption. The mechanism of repolarization function may be that the L-MOF-agomir implants promote the macrophage mitochondrial function and metabolism reprogramming from glycolysis to oxidative phosphorylation. Our study demonstrates the feasibility of targeting cell metabolism to regulate macrophage immunity for peri-implantitis inhibition and provides a new perspective for the development of novel multifunctional implants.

The GSH responsive indocyanine green loaded PD-1 inhibitory polypeptide AUNP12 modified MOF nanoparticles for photothermal and immunotherapy of melanoma

Introduction: Photothermal therapy (PTT) holds significant potential for the treatment of malignant tumors. However, conventional single PTT often struggles to effectively inhibit tumor metastasis and recurrence. In this study, we constructed a MOF nanoparticle with a synergistic therapeutic effect combining photothermal and immunotherapy, enabling selective blocking of the PD-1/PD-L1 pathway within the tumor microenvironment. Methods: Firstly, MOF nanoparticles were synthesized using NH2-TPDC as ligands and Zr+4 as metal ions. Subsequently, NH2 was modified to N3 via azide transfer reagents. Through a copper free catalytic click chemical reaction, the PD-1/PD-L1 blocking agent AUNP-12 functionalized with disulfide bonds of DBCO was covalently introduced into MOF nanoparticles which were then loaded with the photothermal agent indocyanine green (ICG) to successfully obtain uniformly sized and stable ICG-MOF-SS-AUNP12 nanoparticles. Results and discussion: ICG-MOF-SS-AUNP12 exhibited GSH-triggered release of PD-1/PD-L1 blockers while demonstrating potent photothermal effects capable of efficiently killing tumor cells. Under 808 nm near-infrared (NIR) irradiation, ICG-MOF-SS-AUNP12 effectively promoted the maturation of DC cells and activated immune responses. This study presents a novel method for constructing MOF-based nanodrugs and offers new possibilities for the synergistic treatment of tumors involving photothermal combined with immunotherapy.

Designs of metal-organic framework nanoparticles for protein delivery

Recently, there has been high interest in developing metal-organic framework (MOF) nanoparticles (NPs) for delivering therapeutic proteins, propelled mainly by the unique hierarchical porous structures of MOFs for protein encapsulation. Novel design strategies have emerged for broad therapeutic applications and clinical translations, leading to multifunctional MOF-NPs with improved biointerfacing capabilities and higher potency. This review summarizes recent MOF-NP designs specifically for protein delivery. The summary focuses on four design categories, including environment-responsive MOF-NPs for on-demand protein delivery, cell membrane-coated MOF-NPs for biomimetic protein delivery, cascade reaction-incorporated MOF-NPs for combinatorial protein delivery, and composite MOF-NPs for intelligent protein delivery. The major challenges and opportunities in using MOF-NPs for protein delivery are also discussed. Overall, this review will promote designs of MOF-NPs with unique properties to address unmet medical needs.

Peptide nucleic acid-zirconium coordination nanoparticles

Ideal drug carriers feature a high loading capacity to minimize the exposure of patients with excessive, inactive carrier materials. The highest imaginable loading capacity could be achieved by nanocarriers, which are assembled from the therapeutic cargo molecules themselves. Here, we describe peptide nucleic acid (PNA)-based zirconium (Zr) coordination nanoparticles which exhibit very high PNA loading of [Formula: see text] w/w. This metal-organic hybrid nanomaterial class extends the enormous compound space of coordination polymers towards bioactive oligonucleotide linkers. The architecture of single- or double-stranded PNAs was systematically varied to identify design criteria for the coordination driven self-assembly with Zr(IV) nodes at room temperature. Aromatic carboxylic acid functions, serving as Lewis bases, and a two-step synthesis process with preformation of [Formula: see text] turned out to be decisive for successful nanoparticle assembly. Confocal laser scanning microscopy confirmed that the PNA-Zr nanoparticles are readily internalized by cells. PNA-Zr nanoparticles, coated with a cationic lipopeptide, successfully delivered an antisense PNA sequence for splicing correction of the [Formula: see text]-globin intron mutation IVS2-705 into a functional reporter cell line and mediated splice-switching via interaction with the endogenous mRNA splicing machinery. The presented PNA-Zr nanoparticles represent a bioactive platform with high design flexibility and extraordinary PNA loading capacity, where the nucleic acid constitutes an integral part of the material, instead of being loaded into passive delivery systems.

Amino Acid-Coated Zeolitic Imidazolate Framework for Delivery of Genetic Material in Prostate Cancer Cell

Metal-organic frameworks (MOFs) are currently under progressive development as a tool for non-viral biomolecule delivery. Biomolecules such as proteins, lipids, carbohydrates, and nucleic acids can be encapsulated in MOFs for therapeutic purposes. The favorable physicochemical properties of MOFs make them an attractive choice for delivering a wide range of biomolecules including nucleic acids. Herein, a green fluorescence protein (GFP)-expressing plasmid DNA (pDNA) is used as a representative of a biomolecule to encapsulate within a Zn-based metal-organic framework (MOF) called a zeolitic imidazolate framework (ZIF). The synthesized biocomposites are coated with positively charged amino acids (AA) to understand the effect of surface functionalization on the delivery of pDNA to prostate cancer (PC-3) cells. FTIR and zeta potential confirm the successful preparation of positively charged amino acid-functionalized derivatives of pDNA@ZIF (i.e., pDNA@ZIF_AA). Moreover, XRD and SEM data show that the functionalized derivates retain the pristine crystallinity and morphology of pDNA@ZIF. The coated biocomposites provide enhanced uptake of genetic material by PC-3 human prostate cancer cells. The AA-modulated fine-tuning of the surface charge of biocomposites results in better interaction with the cell membrane and enhances cellular uptake. These results suggest that pDNA@ZIF_AA can be a promising alternative tool for non-viral gene delivery.

Peptide-derived coordination frameworks for biomimetic and selective separation

Peptide-derived metal-organic frameworks (PMOFs) have emerged as a class of biomimetic materials with attractive performances in analytical and bioanalytical chemistry. The incorporation of biomolecule peptides gives the frameworks conformational flexibility, guest adaptability, built-in chirality, and molecular recognition ability, which greatly accelerate the applications of PMOFs in enantiomeric separation, affinity separation, and the enrichment of bioactive species from complicated samples. This review focuses on the recent advances in the engineering and applications of PMOFs in selective separation. The unique biomimetic size-, enantio-, and affinity-selective performances for separation are discussed along with the chemical structures and functions of MOFs and peptides. Updates of the applications of PMOFs in adaptive separation of small molecules, chiral separation of drug molecules, and affinity isolation of bioactive species are summarized. Finally, the promising future and remaining challenges of PMOFs for selective separation of complex biosamples are discussed.

Super-Stable Metal-Organic Framework (MOF)/Luciferase Paper-Sensing Platform for Rapid ATP Detection

Adenosine triphosphate (ATP) determination has been used for many decades to assess microbial contamination for hygiene monitoring in different locations and workplace environments. Highly sophisticated methods have been reported, yet commercially available kits rely on a luciferase-luciferin system and require storage and shipping at controlled temperatures (+4 or -20 °C). The applicability of these systems is limited by the need for a secure cold chain, which is not always applicable, especially in remote areas or low-resource settings. In this scenario, easy-to-handle and portable sensors would be highly valuable. Prompted by this need, we developed a bioluminescence paper biosensor for ATP monitoring in which a new luciferase mutant was combined with a metal-organic framework (MOF); i.e., zeolitic imidazolate framework-8 (ZIF-8). A paper biosensor was developed, ZIF-8@Luc paper sensor, and interfaced with different portable light detectors, including a silicon photomultiplier (SiPM) and smartphones. The use of ZIF-8 not only provided a five-fold increase in the bioluminescence signal, but also significantly improved the stability of the sensor, both at +4 and +28 °C. The ATP content in complex biological matrices was analyzed with the ZIF-8@Luc paper sensor, enabling detection down to 7 × 10^-12 moles of ATP and 8 × 10^-13 moles in bacterial lysates and urine samples, respectively. The ZIF-8@Luc sensor could, therefore, be applied in many fields in which ATP monitoring is required such as the control of microbial contamination.

Metal-Organic Frameworks as Sensors for Human Amyloid Diseases

Metal-organic frameworks (MOFs) are versatile compounds with emergent applications in the fabrication of biosensors for amyloid diseases. They hold great potential in biospecimen protection and unprecedented probing capabilities for optical and redox receptors. In this Review, we summarize the main methodologies employed in the fabrication of MOF-based sensors for amyloid diseases and collect all available data in the literature related to their performance (detection range, limit of detection, recovery, time of analysis, among other parameters). Nowadays, MOF sensors have evolved to a point where they can, in some cases, outperform technologies employed in the detection of several amyloid biomarkers (amyloid β peptide, α-synuclein, insulin, procalcitonin, and prolactin) present in biological fluids, such as cerebrospinal fluid and blood. A special emphasis has been given by researchers on Alzheimer's disease monitoring to the detriment of other amyloidosis that are underexploited despite their societal relevance (e.g., Parkinson's disease). There are still important obstacles to overcome in order to selectively detect the various peptide isoforms and soluble amyloid species associated with Alzheimer's disease. Furthermore, MOF contrast agents for imaging peptide soluble oligomers in living humans are also scarce (if not nonexistent), and action in this direction is unquestionably required to clarify the contentious link between the amyloidogenic species and the disease, guiding research toward the most promising therapeutic strategies.

A comprehensive review on bio-mimicked multimolecular frameworks and supramolecules as scaffolds for enzyme immobilization

Immobilization depicts a propitious route to optimize the catalytic performances, efficient recovery, minimizing autocatalysis, and also augment the stabilities of enzymes, particularly in unnatural environments. In this opinion, supramolecules and multimolecular frameworks have captivated immense attention to achieve profound controllable interactions between enzyme molecules and well-defined natural or synthetic architectures to yield protein bioconjugates with high accessibility for substrate binding and enhanced enantioselectivities. This scholastic review emphasizes the possibilities of associating multimolecular complexes with biological entities via several types of interactions, namely covalent interactions, host-guest complexation, π - π ${\rm{\pi }}-{\rm{\pi }}$ interactions, intra/inter hydrogen bondings, electrostatic interactions, and so forth offers remarkable applications for the modulations of enzymes. The potential synergies between artificial supramolecular structures and biological systems are the primary concern of this pedagogical review. The majority of the research primarily focused on the dynamic biomolecule-responsive supramolecular assemblages and multimolecular architectures as ideal platforms for the recognition and modulation of proteins and cells. Embracing sustainable green demeanors of enzyme immobilizations in a quest to reinforce site-selectivity, catalytic efficiency, and structural integrality of enzymes are the contemporary requirements of the biotechnological sectors that instigate the development of novel biocatalytic systems.

Novel Nanozeolitic Imidazolate Framework (ZIF-8)-Luciferase Biocomposite for Nanosensing Applications

The identification of new strategies to improve the stability of proteins is of utmost importance for a number of applications, from biosensing to biocatalysis. Metal-organic frameworks (MOFs) have been shown as a versatile host platform for the immobilization of proteins, with the potential to protect proteins in harsh conditions. In this work, a new thermostable luciferase mutant has been selected as a bioluminescent protein model to investigate the suitability of MOFs to improve its stability and prompt its applications in real-world applications, for example, ATP detection in portable systems. The luciferase has been immobilized onto zeolitic imidazolate framework-8 (ZIF-8) to obtain a bioluminescent biocomposite with enhanced performance. The biocomposite ZIF-8@luc has been characterized in harsh conditions (e.g., high temperature, non-native pH, etc.). Bioluminescence properties confirmed that MOF enhanced the luciferase stability at acidic pH, in the presence of organic solvents, and at -20 °C. To assess the feasibility of this approach, the recyclability, storage stability, precision, and Michaelis-Menten constants (K_m) for ATP and d-luciferin have been also evaluated. As a proof of principle, the suitability for ATP detection was investigated and the biocomposite outperformed the free enzyme in the same experimental conditions, achieving a limit of detection for ATP down to 0.2 fmol.

Carrier gas triggered controlled biolistic delivery of DNA and protein therapeutics from metal-organic frameworks

The efficacy and specificity of protein, DNA, and RNA-based drugs make them popular in the clinic; however, these drugs are often delivered via injection, requiring skilled medical personnel, and producing biohazardous waste. Here, we report an approach that allows for their controlled delivery, affording either a burst or slow release without altering the formulation. We show that when encapsulated within zeolitic-imidazolate framework eight (ZIF-8), the biomolecules are stable in powder formulations and can be inoculated with a low-cost, gas-powered "MOF-Jet" into living animal and plant tissues. Additionally, their release profiles can be modulated through judicious selection of the carrier gas used in the MOF-Jet. Our in vitro and in vivo studies reveal that when CO₂ is used, it creates a transient and weakly acidic local environment that causes a near-instantaneous release of the biomolecules through an immediate dissolution of ZIF-8. Conversely, when air is used, ZIF-8 biodegrades slowly, releasing the biomolecules over a week. This is the first example of controlled-biolistic delivery of biomolecules using ZIF-8, which provides a powerful tool for fundamental and applied science research.

Metal organic framework encapsulated tamavidin-Gluc reporter: application in COVID-19 spike antigen bioluminescent immunoassay

Enzyme linked immunosorbent assay (ELISA) is one of the most utilized serological methods to diagnose and identify etiologic agents of many infectious diseases and other physiologically important analytes. ELISA can be used either alone or adjunct to other diagnostic methods such as molecular arrays, and other serological techniques. Most ELISA assays utilize reagents that are proteinaceous in nature, which are not very stable and require cold-chain transport systems. Development of a desirable immunoassay requires stability of reagents used and its ability to be stored at room temperature without sacrificing the activity of the reagents or the protein of interest. Metal organic frameworks (MOFs) are a rapidly emerging and evolving class of porous polymeric materials used in a variety of biosensor applications. In this study, we introduce the use of MOFs to stabilize a universal reporter fusion protein, specifically, avidin-like protein (Tam-avidin2) and the small bioluminescent protein Gaussia luciferase (Gluc) forming the fusion reporter, tamavidin2-Gluc (TA2-Gluc). This fusion protein serves as a universal reporter for any assays that utilize biotin-avidin binding strategy. Using SARS-CoV2 S1 spike antigen as the model target antigen, we demonstrated that encapsulation of TA2-Gluc fusion protein using a nano-porous material, zeolitic imidazolate framework-8 (ZIF-8), allows us to store and preserve this reporter protein at room temperature for over 6 months and use it as a reporter for an ELISA assay. Our optimized assay was validated demonstrating a 0.26 μg mL-1 limit of detection, high reproducibility of assay over days, detection of spiked non-virulent SARS-COV2 pseudovirus in real sample matrix, and detection in real COVID-19 infected individuals. This result can lead to the utilization of our TA2-Gluc fusion protein reporter with other assays and potentially in diagnostic technologies in a point-of-care setting.

Encapsulation of Imazalil in HKUST-1 with Versatile Antimicrobial Activity

Based on high surface areas, adjustable porosity and microbicide activity, metal-organic frameworks (MOFs) HKUST-1 are widely used as drug release carriers for their slow degradation characteristics under slightly acidic conditions. In this work, porous HKUST-1 was reacted rapidly by cholinium salt (as the deprotonation agent and template) in an aqueous solution at room temperature. A novel antimicrobial system based on an imazalil encapsulated metal organic framework (imazalil IL-3@HKUST-1) was established. Imazalil IL-3@HKUST-1 could achieve synergism in inhibiting pathogenic fungi and bacteria. Moreover, six days after treatment, the slow and constant release of imazalil from imazalil IL@HKUST-1 exhibited better sustainability and microbicidal activity than imazalil. We believe that the method may provide a new strategy for related plant diseases caused by bacteria or fungi.

Synthesis and Biomedical Applications of Highly Porous Metal-Organic Frameworks

In this review, aspects of the synthesis, framework topologies, and biomedical applications of highly porous metal-organic frameworks are discussed. The term "highly porous metal-organic frameworks" (HPMOFs) is used to denote MOFs with a surface area larger than 4000 m² g^-1. Such compounds are suitable for the encapsulation of a variety of large guest molecules, ranging from organic dyes to drugs and proteins, and hence they can address major contemporary challenges in the environmental and biomedical field. Numerous synthetic approaches towards HPMOFs have been developed and discussed herein. Attempts are made to categorise the most successful synthetic strategies; however, these are often not independent from each other, and a combination of different parameters is required to be thoroughly considered for the synthesis of stable HPMOFs. The majority of the HPMOFs in this review are of special interest not only because of their high porosity and fascinating structures, but also due to their capability to encapsulate and deliver drugs, proteins, enzymes, genes, or cells; hence, they are excellent candidates in biomedical applications that involve drug delivery, enzyme immobilisation, gene targeting, etc. The encapsulation strategies are described, and the MOFs are categorised according to the type of biomolecule they are able to encapsulate. The research field of HPMOFs has witnessed tremendous development recently. Their intriguing features and potential applications attract researchers' interest and promise an auspicious future for this class of highly porous materials.

Role of Molecular Modification and Protein Folding in the Nucleation and Growth of Protein-Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a class of porous nanomaterials that have been extensively studied as enzyme immobilization substrates. During in situ immobilization, MOF nucleation is driven by biomolecules with low isoelectric points. Investigation of how biomolecules control MOF self-assembly mechanisms on the molecular level is key to designing nanomaterials with desired physical and chemical properties. Here, we demonstrate how molecular modifications of bovine serum albumin (BSA) with fluorescein isothiocyanate (FITC) can affect MOF crystal size, morphology, and encapsulation efficiency. Final crystal properties are characterized using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), fluorescent microscopy, and fluorescence spectroscopy. To probe MOF self-assembly, in situ experiments were performed using cryogenic transmission electron microscopy (cryo-TEM) and X-ray diffraction (XRD). Biophysical characterization of BSA and FITC-BSA was performed using ζ potential, mass spectrometry, circular dichroism studies, fluorescence spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The combined data reveal that protein folding and stability within amorphous precursors are contributing factors in the rate, extent, and mechanism of crystallization. Thus, our results suggest molecular modifications as promising methods for fine-tuning protein@MOFs' nucleation and growth.

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.

Multi-Emission from Single Metal-Organic Frameworks under Single Excitation

Multi-emission materials have come to prominent attention ascribed to their extended applications other than single-emission ones. General and robust design strategies of a single matrix with multi-emission under single excitation are urgently required. Metal-organic frameworks (MOFs) are porous materials prepared with organic ligands and metal nodes. The variety of metal nodes and ligands makes MOFs with great superiority as multi-emission matrices. Guest species encapsulated into the channels or pores of MOFs are the additional emission sites for multi-emission. In this review, multi-emission MOFs according to the different excitation sites are summarized and classified. The emission mechanisms are discussed, such as antenna effect, excited-state intramolecular proton transfer (ESIPT) and tautomerism for dual-emission. The factors that affect the emissions are revealed, including ligand-metal energy transfer and host-guest interaction, etc. Multi-emission MOFs could be predictably designed and prepared, once the emissive factors are controlled rationally in combination with the different multi-emission mechanisms. Correspondingly, new and practical applications are realized, including but not limited to ratiometric/multi-target sensing and bioimaging, white light-emitting diodes, and anti-counterfeiting. The design strategies of multi-emission MOFs and their extensive applications are reviewed. The results will shed light on other multi-emission systems to develop the structure-derived functionality and applications.

Programmable Photoluminescence via Intrinsic and DNA-Fluorophore Association in a Mixed Cluster Heterometallic MOF

A rapid and facile design strategy to create a highly complex optical tag with programmable, multimodal photoluminescent properties is described. This was achieved via intrinsic and DNA-fluorophore hidden signatures. As a first covert feature of the tag, an intricate novel heterometallic near-infrared (NIR)-emitting mesoporous metal-organic framework (MOF) was designed and synthesized. The material is constructed from two chemically distinct, homometallic hexanuclear clusters based on Nd and Yb. Uniquely, the Nd-based cluster is observed here for the first time in a MOF and consists of two staggered Nd μ₃-oxo trimers. To generate controlled, multimodal, and tailorable emission with difficult to counterfeit features, the NIR-emissive MOF was post-synthetically modified via a fluorescent DNA oligo labeling design strategy. The surface attachment of several distinct fluorophores, including the simultaneous attachment of up to three distinct fluorescently labeled oligos was achieved, with excitation and emission properties across the visible spectrum (480-800 nm). The DNA inclusion as a secondary covert element in the tag was demonstrated via the detection of SYBR Gold dye association. Importantly, the approach implemented here serves as a rapid and tailorable way to encrypt distinct information in a facile and modular fashion and provides an innovative technology in the quest toward complex optical tags.

Journey to the Market: The Evolution of Biodegradable Drug Delivery Systems

Biodegradable polymers have been used as carriers in drug delivery systems for more than four decades. Early work used crude natural materials for particle fabrication, whereas more recent work has utilized synthetic polymers. Applications include the macroscale, the microscale, and the nanoscale. Since pioneering work in the 1960’s, an array of products that use biodegradable polymers to encapsulate the desired drug payload have been approved for human use by international regulatory agencies. The commercial success of these products has led to further research in the field aimed at bringing forward new formulation types for improved delivery of various small molecule and biologic drugs. Here, we review recent advances in the development of these materials and we provide insight on their drug delivery application. We also address payload encapsulation and drug release mechanisms from biodegradable formulations and their application in approved therapeutic products.

Hierarchically encapsulating enzymes with multi-shelled metal-organic frameworks for tandem biocatalytic reactions

Biocatalytic transformations in living organisms, such as multi-enzyme catalytic cascades, proceed in different cellular membrane-compartmentalized organelles with high efficiency. Nevertheless, it remains challenging to mimicking biocatalytic cascade processes in natural systems. Herein, we demonstrate that multi-shelled metal-organic frameworks (MOFs) can be used as a hierarchical scaffold to spatially organize enzymes on nanoscale to enhance cascade catalytic efficiency. Encapsulating multi-enzymes with multi-shelled MOFs by epitaxial shell-by-shell overgrowth leads to 5.8~13.5-fold enhancements in catalytic efficiencies compared with free enzymes in solution. Importantly, multi-shelled MOFs can act as a multi-spatial-compartmental nanoreactor that allows physically compartmentalize multiple enzymes in a single MOF nanoparticle for operating incompatible tandem biocatalytic reaction in one pot. Additionally, we use nanoscale Fourier transform infrared (nano-FTIR) spectroscopy to resolve nanoscale heterogeneity of vibrational activity associated to enzymes encapsulated in multi-shelled MOFs. Furthermore, multi-shelled MOFs enable facile control of multi-enzyme positions according to specific tandem reaction routes, in which close positioning of enzyme-1-loaded and enzyme-2-loaded shells along the inner-to-outer shells could effectively facilitate mass transportation to promote efficient tandem biocatalytic reaction. This work is anticipated to shed new light on designing efficient multi-enzyme catalytic cascades to encourage applications in many chemical and pharmaceutical industrial processes.

Mimicking multi-enzyme catalytic cascades in natural systems with spatial organization in confined structures is gaining increasing attention in the emerging field of systems chemistry. Here, the authors demonstrate that multi-shelled metal-organic frameworks can be used as a hierarchical scaffold to spatially organize enzymes on nanoscale to enhance cascade catalytic efficiency.

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

A defining characteristic of nearly all catalytically functional MOFs is uniform, molecular-scale porosity. MOF pores, linkers and nodes that define them, help regulate reactant and product transport, catalyst siting, catalyst accessibility, catalyst stability, catalyst activity, co-catalyst proximity, composition of the chemical environment at and beyond the catalytic active site, chemical intermediate and transition-state conformations, thermodynamic affinity of molecular guests for MOF interior sites, framework charge and density of charge-compensating ions, pore hydrophobicity/hydrophilicity, pore and channel rigidity vs. flexibility, and other features and properties. Collectively and individually, these properties help define overall catalyst functional behaviour. This review focuses on how porous, catalyst-containing MOFs capitalize on molecular-scale confinement, containment, isolation, environment modulation, energy delivery, and mobility to accomplish desired chemical transformations with potentially superior selectivity or other efficacy, especially in comparison to catalysts in homogeneous solution environments.

Recent Advances in Metal-Organic Framework-Based Electrochemical Biosensing Applications

In the face of complex environments, considerable effort has been made to accomplish sensitive, accurate and highly-effective detection of target analytes. Given the versatility of metal clusters and ligands, high porosity and large specific surface area, metal–organic framework (MOF) provides researchers with prospective solutions for the construction of biosensing platforms. Combined with the benefits of electrochemistry method such as fast response, low cost and simple operation, the untapped applications of MOF for biosensors are worthy to be exploited. Therefore, this review briefly summarizes the preparation methods of electroactive MOF, including synthesize with electroactive ligands/metal ions, functionalization of MOF with biomolecules and modification for MOF composites. Moreover, recent biosensing applications are highlighted in terms of small biomolecules, biomacromolecules, and pathogenic cells. We conclude with a discussion of future challenges and prospects in the field. It aims to offer researchers inspiration to address the issues appropriately in further investigations.

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...

Stable DNA Aptamer-Metal-Organic Framework as Horseradish Peroxidase Mimic for Ultra-Sensitive Detection of Carcinoembryonic Antigen in Serum

Carcinoembryonic antigen (CEA) is an important broad-spectrum tumor marker. For CEA detection, a novel type of metal-organic framework (MOF) was prepared by grafting CEA aptamer-incorporated DNA tetrahedral (TDN) nanostructures into PCN-222 (Fe)-based MOF (referred as CEAapt-TDN-MOF colloid nanorods). The synthesized CEAapt-TDN-MOF is a very stable detection system due to the vertex phosphorylated TDN structure at the interface, possessing a one-year shelf-life. Moreover, it exhibits a significant horseradish peroxidase mimicking activity due to the iron porphyrin ring, which leads to a colorimetric reaction upon binding toward antibody-captured CEA. Using this method, we successfully achieved the highly specific and ultra-sensitive detection of CEA with a limit of detection as low as 3.3 pg/mL. In addition, this method can detect and analyze the target proteins in clinical serum samples, effectively identify the difference between normal individuals and patients with colon cancer, and provide a new method for the clinical diagnosis of tumors, demonstrating a great application potential.

Polymer-Surfactant Driven Interactions and the Resultant Microstructure in Protein-Containing Liquid Crystal Droplets

Integration of molecular liquid crystals (LCs) with functional proteins can provide new class of materials for potential applications in optical biosensing. However, hydrophobic nematic LCs (length ∼ 1-2 nm) and hydrophilic proteins, size ∼ O (nm), do not intermix without chemical modification of at least one of them. Bioconjugation of proteins with a polyethylene glycol-based polymeric surfactant (PS) can provide a core-shell system that is sequestered within nonaqueous LC (4-cyano-4'-pentylbiphenyl) microdroplets. However, the nature of interactions between the components and detailed understanding of the resultant hybrid microstructure remains unclear. Here, using a combination of isothermal titration calorimetry (ITC), fluorescence microscopy, and infrared-imaging spectroscopy, we show that strong hydrophobic interactions between the LC and PS drives the sequestration of a myoglobin-PS (Mb-PS; dispersed in the aqueous phase) into the LC spherical microdroplets or even into a bulk LC phase. The average values of both, the binding constant and the standard molar enthalpy change, are increased by approximately a factor of 2.5 times when the unmodified Mb is conjugated to the PS. Small-angle X-ray scattering studies reveal that LC molecules act as a solvent for the Mb-PS conjugate; furthermore, the LC long-range order is disturbed due to mixing, as exemplified by the change in its coherence length from 8.9 to 5.7 nm. Detailed all-atomistic molecular dynamic simulations for a three-component PS-water-LC system show a change in interaction energy of -144 kJ mol^-1 PS^-1 upon the contact of PS chains (initially dispersed in water) with LC and agree with the ITC experiments.

Simultaneous improvement to solubility and bioavailability of active natural compound isosteviol using cyclodextrin metal-organic frameworks

Cyclodextrin metal-organic framework (CD-MOF) as a highly porous supramolecular carrier could be one of the solutions to the insolubility of isosteviol (STV). The solubility of STV was lower than 20.00 ng/mL at pH 1.0 and pH 4.5, whilst its solubility increased to 20,074.30 ng/mL at pH 6.8 and 129.58 ng/mL in water with a significant pH-dependence. The in vitro release profiles of STV from STV@CD-MOF (0.5:1) were pH-independent in distinct pH media and closed to be thoroughly released but no such release profiles were observed for STV@CD-MOF (1:1) owing to nanoclusters formation. The bioavailability of STV@CD-MOF (1:1) in rats was 8.67-fold higher than that of STV, and was 1.32- and 1.27-fold higher than that of STV@CD and STV@CD-MOF (0.5:1). Our results indicated that the inclusion mechanism played a primary role when STV in CD-MOF was at a low loading ratio, while the increasement in bioavailability at a high loading ratio, which was attributed to the nanocluster mechanism. This was confirmed by molecular simulation. In conclusion, CD-MOF is a promising system for STV loading, overcoming the insolubility and to improve the bioavailability of this natural compound.

Biodegradation pathway of penicillins by β-lactamase encapsulated in metal-organic frameworks

The pollution caused by the abuse of antibiotics has posed a serious threat to the ecological environment and human health, so development of effective strategies for degradation and disposal of antibiotic residues is urgently needed. In this work, penicillinase, a kind of β-lactamase, was immobilized into zeolitic imidazolate framework-8 (ZIF-8) by self-assembly method and the catalytic performance of the β-lactamase@ZIF-8 porous materials for degradation of penicillins has been investigated by high performance liquid chromatography coupled with mass spectrometry. The results illustrated that the catalytic activity of the encapsulated enzyme was significantly enhanced comparing with that of free enzyme. Meanwhile, the β-lactamase@ZIF-8 exhibited excellent stability under denaturing conditions including high temperature, organic solvent and the enzyme inhibitor. The catalytic degradation mechanism of the β-lactamase@ZIF-8 for penicillins has been probed and verified, and it has been found that the Zn (II) ion on ZIF-8 frameworks could form the complex with the target molecule, which weakened the bond of the four-membered β-lactam ring in the penicillin molecule, and thus enhanced the degradation efficiency of the enzyme. This work provided a promising strategy for eliminating the penicillin residues in water environment.

Ultrasensitive immunoassay for detection of zearalenone in agro-products using enzyme and antibody co-embedded zeolitic imidazolate framework as labels

Zearalenone (ZEN) has a potential hazard to human health, and is frequently found in agro-products. To minimize ZEN exposure to consumers, a novel metal-organic framework-based immunoassay system using zeolitic imidazolate framework-encapsulated horseradish peroxidase and goat anti-mouse IgG (HRP/Ab@ZIF-L) as labels was proposed for rapid and ultrasensitive detection of ZEN in agro-products. The HRP/Ab@ZIF-L not only maintained recognition ability of antibody and catalytic activity of enzyme, but also protected encapsulated proteins against high temperature, organic solvents and long term storage. Under optimal conditions, the detection limit of HRP/Ab@ZIF-L-based immunoassay reached 0.5 ng/L for ZEN, which was approximately 126-fold lower than that of conventional HRP-based immunoassay. Moreover, the proposed method showed an excellent selectivity, and a good dynamic linear detection for ZEN in the range of 0.5 ng/L to 0.476 μg/L. The recoveries of ZEN from spiked corn and wheat samples ranged from 84.50% to 96.70% with the relative standard deviation under 8.9%. In brief, the proposed immunoassay method has potential application for rapid and ultrasensitive detection of ZEN in agro-products.

Metal organic frameworks (MOFs) with therapeutic and biomedical applications: a patent review

Introduction: Metal organic frameworks (MOFs) are a recent group of nano porous materials with exceptional physical properties, such as large surface areas, high pore volumes, low densities and well-defined pores. This type of material has been used frequently for biomedical and therapeutic applications, such as drug delivery systems and theranostic materials.Areas covered: In this review, the authors searched for patents filed in the last 10 years, found in different databases, related to the therapeutic or biomedical application of MOFs for use in different health fields. The possibility of these new materials becoming new therapeutic possibilities available to the population was emphasized.Expert opinion: The advances in research with MOFs have grown in the last 10 years and with that many possibilities for their applications have emerged in several areas, especially biomedical. The possibility of using these materials in drug delivery systems is the most common form of possibility of use in the health area, mainly due to easy obtaining and high reproducibility, which are seen very positively by the drug development technology sector.

Molecular Surgery at Microporous MOF for Mesopore Generation and Renovation

Hierarchically porous MOFs (HP-MOFs) present advantageous synergism of micro- and mesopore but challenging in synthetic control at molecular scale. Herein, we present the first example of reversible and controllable mesopore generation and renovation in a microporous MOF of HKUST-1 via synthetic manipulation at molecular scale. An ammonia-gas etching strategy is proposed to create mesopores in carboxylate-based microporous MOFs and thus produce HP-MOFs. Gas-phase etching ensures uniform mesopore formation inside the MOF crystals via plane-oriented cutting the carboxylate-metal bonds off without affecting the crystal size and morphology. The mesopore size is controlled by the etching temperature, while the mesopore volume could be tuned by adjusting etchant pressure. The generated mesopores could be renovated using MOF precursors solutions so that to achieve controllable mesopore generation/closure, and encapsulation of the adsorbed molecules. This work demonstrates a powerful protocol for precisely tailoring and tuning the properties of MOF materials at molecular scale.

Metal-Organic Framework-Based Composites for Protein Delivery and Therapeutics

Owing to high bioactivity and specificity, protein drugs have achieved great success in both diagnosis and therapy. The idea of delivering active proteins directly to targets is becoming more and more attractive. However, due to their large size and environmental sensitivity, it is not easy for proteins to maintain bioactivity in extracellular fluids and cross cell membrane without being damaged. A series of techniques and carriers have been developed to deliver proteins. Thereinto, metal-organic frameworks (MOFs), which are made of metal ions connected by organic linkers, are one of the most important vehicles for protein delivery. Their porous structures, stability, biocompatibility, reproducibility, and the possibility for further functionalities offer great potential for protein delivery. In this review, recent developments of protein encapsulated by MOF nanoparticles, including mechanism of treatment, structural design, loading capacity, delivery, and release properties of proteins, are summarized, and the relationship between structure and performance is emphasized. Meanwhile, further improvements and implementations are discussed.

Stabilization of surface-bound antibodies for ELISA based on a reversable zeolitic imidazolate framework-8 coating

Immunoassays typically must be stored under refrigerated conditions because antibodies, after being immobilized to solid surfaces, tend to lose their recognition capabilities to target antigens under non-refrigerated conditions. This requirement hinders application of immunoassays in resource-limited settings including rural clinics in tropical regions, disaster struck areas, and low-income countries, where refrigeration may not be feasible. In this work, a facile approach based on a reversable zeolitic imidazolate framework-8 (ZIF-8) coating is introduced to stabilize surface-bound antibodies on enzyme-linked immunosorbent assay (ELISA) plates under non-refrigerated conditions. Using a sandwich ELISA for the detection of neutrophil gelatinase-associated lipocalin (NGAL), a urine biomarker for acute kidney injury, as a model system, ZIF-8 is demonstrated to be able to uniformly coat the surface-bound anti-NGAL IgG, and stabilize the dynamic range and detection sensitivity of the assay after storage at an elevated temperature (50 °C) for at least 4 weeks. The stabilization efficacy of the ZIF-8 coating is comparable to the current "gold standard" refrigeration approach, and superior to the commonly used sucrose coating method. This approach will greatly improve the shelf-life and stability of antibody-coated ELISAs and other types of assays which utilize surface-bound antibodies, thus extending biomedical research and medical diagnostics to resource-limited settings.

Cerium-Based Metal-Organic Framework Nanocrystals Interconnected by Carbon Nanotubes for Boosting Electrochemical Capacitor Performance

In this study, nanocrystals of a cerium-based metal-organic framework (Ce-MOF), Ce-MOF-808, are directly grown on the surface of carboxylic acid-functionalized carbon nanotubes (CNTs) by a facile one-step solvothermal synthesis method. Ce-MOF-CNT nanocomposites with various Ce-MOF-to-CNT ratios are synthesized, and their crystallinity, morphology, porosity, and electrical conductivity are examined. The redox-hopping and electrochemical behaviors of the pristine Ce-MOF in aqueous electrolytes are investigated, suggesting that the pristine Ce-MOF is electrochemically active but possesses a limited charge-transport behavior. As a demonstration, all the Ce-MOF, CNT, and nanocomposites are used as active materials for application in aqueous-based supercapacitors. The capacitive performance of the CNT can be significantly boosted with the help of redox-active Ce-MOF-808 nanocrystals.