Efficient Separation of Nucleic Acids with Different Secondary Structures by Metal-Organic Frameworks

Programmable Lanthanide Metal-Organic Framework for Ultra-Efficient Nucleic Acids Extraction and Interaction Analysis

Efficient, mild, and reversible adsorption of nucleic acids onto nanomaterials represents a promising analytical approach for medical diagnosis. However, there is a scarcity of efficient and reversible nucleic acid adsorption nanomaterials. Additionally, the lack of comprehension of the molecular mechanisms governing their interactions poses significant challenges. These issues hinder the rational design and analytical applications of the nanomaterials. Herein, we propose an ultra-efficient nucleic acid affinity nanomaterial based on programmable lanthanide metal-organic frameworks (Ln-MOFs). Through experiments and density functional theory calculations, a rational design guideline for nucleic acid affinity of Ln-MOF was proposed, and a modular and flexible preparation scheme was provided. Then, Er-TPA (terephthalic acid) MOF emerged as the optimal candidate due to its pore size-independent adsorption and desorption capabilities for nucleic acids, enabling ultra-efficient adsorption (about 150% mass ratio) within 1 min. Furthermore, we elucidate the molecular-level mechanisms underlying the Ln-MOF adsorption of single- and double-stranded DNA and G4 structures. The affinity nanomaterial based on Ln-MOF exhibits robust nucleic acid extraction capability (4-fold higher than commercial reagent kits) and enables mild and reversible CRISPR/Cas9 functional regulation. This method holds significant promise for broad application in DNA/RNA liquid biopsy and gene editing, facilitating breakthroughs in analytical chemistry, pharmacy, and medical research.

1D and 2D coordination polymers with a new rigid chelating linker: diacetylenedisalicylic acid

Diacetylenedisalicylic acid is a new rigid linker molecule, capable of forming strong chelate bonds with metal cations. Its monosubstituted salts with dimethylamine and sodium form 1D and 2D coordination polymers, whose structures were solved from single crystals, along with the dimethyl ester of diacetylenedisalicylic acid. The structure of the dimethyl ester is characterized by a dense co-facial π-stacking of molecules with a dominance of van der Waals interactions between the stacks. The angle between the stack direction and the butadiyne groups does not meet the Enkelmann criterion for polymerization in a crystal. In contrast to the dimethyl ester, both salts have a rigid framework with channels filled with disordered solvent molecules. Photoluminescence spectra of the acid and its dimethyl ester have been studied. Thermal analysis of the acid confirms its high thermal stability to 286°C. The acid and its dimethyl ester are prone to polymerization on further heating followed by 50-52% mass loss, forming an amorphous carbon residue at 1000°C.

Method for the extraction of circulating nucleic acids based on MOF reveals cell-free RNA signatures in liver cancer

Cell-free RNA (cfRNA) allows assessment of health, status, and phenotype of a variety of human organs and is a potential biomarker to non-invasively diagnose numerous diseases. Nevertheless, there is a lack of highly efficient and bias-free cfRNA isolation technologies due to the low abundance and instability of cfRNA. Here, we developed a reproducible and high-efficiency isolation technology for different types of cell-free nucleic acids (containing cfRNA and viral RNA) in serum/plasma based on the inclusion of nucleic acids by metal-organic framework (MOF) materials, which greatly improved the isolation efficiency and was able to preserve RNA integrity compared with the most widely used research kit method. Importantly, the quality of cfRNA extracted by the MOF method is about 10-fold that of the kit method, and the MOF method isolates more than three times as many different RNA types as the kit method. The whole transcriptome mapping characteristics of cfRNA in serum from patients with liver cancer was described and a cfRNA signature with six cfRNAs was identified to diagnose liver cancer with high diagnostic efficiency (area under curve = 0.905 in the independent validation cohort) using this MOF method. Thus, this new MOF isolation technique will advance the field of liquid biopsy, with the potential to diagnose liver cancer.

Isoreticular Chemistry and Applications of Supramolecularly Assembled Copper-Adenine Porous Materials

The useful concepts of reticular chemistry, rigid and predictable metal nodes together with strong and manageable covalent interactions between metal centers and organic linkers, have made the so-called metal-organic frameworks (MOFs) a flourishing area of enormous applicability. In this work, the extension of similar strategies to supramolecularly assembled metal-organic materials has allowed us to obtain a family of isoreticular compounds of the general formula [Cu7(μ-adeninato-κN3:κN9)6(μ3-OH)6(μ-OH2)6](OOC-R-COO)·nH2O (R: ethylene-, acetylene-, naphthalene-, or biphenyl-group) in which the rigid copper-adeninato entities and the organic dicarboxylate anions are held together not by covalent interactions but by a robust and flexible network of synergic hydrogen bonds and π-π stacking interactions based on well-known supramolecular synthons (SMOFs). All compounds are isoreticular, highly insoluble, and water-stable and show a porous crystalline structure with a pcu topology containing a two-dimensional (2D) network of channels, whose dimensions and degree of porosity of the supramolecular network are tailored by the length of the dicarboxylate anion. The partial loss of the crystallization water molecules upon removal from the mother liquor produces a shrinkage of the unit cell and porosity, which leads to a color change of the compounds (from blue to olive green) if complete dehydration is achieved by means of gentle heating or vacuuming. However, the supramolecular network of noncovalent interactions is robust and flexible enough to reverse to the expanded unit cell and color after exposure to a humid atmosphere. This humidity-driven breathing behavior has been used to design a sensor in which the electrical resistance varies reversibly with the degree of humidity, very similar to the water vapor adsorption isotherm of the SMOF. The in-solution adsorption properties were explored for the uptake and release of the widely employed 5-fluorouracil, 4-aminosalycilic acid, 5-aminosalycilic acid, and allopurinol drugs. In addition, cytotoxicity activity assays were completed for the pristine and 5-fluorouracil-loaded samples.

Mesoporous Metal-Organic Frameworks for Catalytic RNA Deprotection and Activation

A metal-organic framework (MOF) with mespores (2 to 50 nm) allows the inclusion of large biomolecules, such as nucleic acids. However, chemical reaction on the nucleic acids, to further regulate their bioactivity, is yet to be demonstrated within MOF pores. Here, we report the deprotection of carbonate protected RNA molecules (21 to 102 nt) to restore their original activity using a MOF as a heterogeneous catalyst. Two MOFs, MOF-626 and MOF-636 are designed and synthesized, with mesopores of 2.2 and 2.8 nm, respectively, carrying isolated metal sites (Ni, Co, Cu, Pd, Rh and Ru). The pores favor the entrance of RNA, while the metal sites catalyze C-O bond cleavage at the carbonate group. Complete conversion of RNA is achieved by Pd-MOF-626, 90 times more efficiently than Pd(NO3 )2 . MOF crystals are also removable from the aqueous reaction media, leaving a negligible metal footprint, 3.9 ppb, only 1/55 of that using homogeneous Pd catalysts. These features make MOF potentially suited for bioorthogonal chemistry.

Nanoporous Crystalline Materials for the Recognition and Applications of Nucleic Acids

Nucleic acid plays a crucial role in countless biological processes. Hence, there is great interest in its detection and analysis in various fields from chemistry, biology, to medicine. Nanoporous crystalline materials exhibit enormous potential as an effective platform for nucleic acid recognition and application. These materials have highly ordered and uniform pore structures, as well as adjustable surface chemistry and pore size, making them good carriers for nucleic acid extraction, detection, and delivery. In this review, the latest developments in nanoporous crystalline materials, including metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular organic frameworks (SOFs) for nucleic acid recognition and applications are discussed. Different strategies for functionalizing these materials are explored to specifically identify nucleic acid targets. Their applications in selective separation and detection of nucleic acids are highlighted. They can also be used as DNA/RNA sensors, gene delivery agents, host DNAzymes, and in DNA-based computing. Other applications include catalysis, data storage, and biomimetics. The development of novel nanoporous crystalline materials with enhanced biocompatibility has opened up new avenues in the fields of nucleic acid analysis and therapy, paving the way for the development of sensitive, selective, and cost-effective diagnostic and therapeutic tools with widespread applications.

Extremely Large 3D Cages in Metal-Organic Frameworks for Nucleic Acid Extraction

Three-dimensional (3D) cages in the mesopore regime (2-50 nm) assembled from molecular building blocks are highly desirable in biological applications; however, their synthesis in crystalline form is quite challenging, as well as their structure characterization. Here, we report the synthesis of extremely large 3D cages in MOF crystals, with internal cage sizes of 6.9, and 8.5 nm in MOF-929; 9.3 and 11.4 nm in MOF-939, in cubic unit cells, a = 17.4 and 22.8 nm, respectively. These cages are constructed from relatively short organic linkers with the lengths of 0.85 and 1.3 nm, where the influence from molecular motion is minimized, thus favoring their crystallization. A 0.45 nm linker length elongation leads to a maximum 2.9 nm increase in cage size, giving a supreme efficiency in cage expansion. The spatial arrangements of these 3D cages were visualized by both X-ray diffraction and transmission electron microscopy. The efforts to obtain these cages in crystals pushed forward the size boundary for the construction of 3D cages from molecules and also exploited the limit of the area in space possibly supported per chemical bond, where the expansion efficiencies of the cages were found to play a critical role. These extremely large 3D cages in MOFs were useful in the complete extraction of long nucleic acid, such as total RNA and plasmid from aqueous solution.

Engineering nanoenzymes integrating Iron-based metal organic frameworks with Pt nanoparticles for enhanced Photodynamic-Ferroptosis therapy

Photodynamic therapy (PDT), as a promising strategy in cancer treatment that utilizes photosensitizers (PSs) to produce reactive oxygen species, has been widely used for eliminating cancer cells under specific wavelength light irradiation. However, the low aqueous solubility of PSs and special tumor microenvironments (TME), such as high glutathione (GSH) and tumor hypoxia remain challenges towards PDT for hypoxic tumor treatment. To address these problems, we constructed a novel nanoenzyme for enhanced PDT-ferroptosis therapy by integrating small Pt nanoparticles (Pt NPs) and near-infrared photosensitizer CyI into iron-based metal organic frameworks (MOFs). In addition, hyaluronic acid was adhered to the surface of the nanoenzymes to enhance the targeting ability. In this design, MOFs act not only as a delivery vector for PSs, but also a ferroptosis inducer. Pt NPs stabilized by MOFs were functioned as an oxygen (O₂) generator by catalyzing hydrogen peroxide into O₂ to relieve tumor hypoxia and increase singlet oxygen generation. In vitro and in vivo results demonstrated that under laser irradiation, this nanoenzyme could effectively relive the tumor hypoxia and decrease the level of GSH, resulting in enhanced PDT-ferroptosis therapy against hypoxic tumor. The proposed nanoenzymes represent an important advance in altering TME for improved clinical PDT-ferroptosis therapy, as well as their potential as effective theranostic agents for hypoxic tumors.

Highly Stable Fe/Co-TPY-MIL-88(NH2) Metal-Organic Framework (MOF) in Enzymatic Cascade Reactions for Chemiluminescence-Based Detection of Extracellular Vesicles

Metal-Organic Frameworks (MOFs) can deliver many advantages when acting as enzyme mimics to assist with signal amplification in molecular detection: they have abundant active catalytic sites per unit volume of the material; their structures and elemental compositions are highly tunable, and their high specific surface area and porous property can assist with target separation and enrichment. In the present work, we have demonstrated that, by adding the pore partition agent, 2,4,6-tris(4-pyridyl)pyridine (TPY) during synthesis of the bimetallic Fe/Co-MIL-88(NH₂) MOF to block the open metal sites, a highly porous MOF of Fe/Co-TPY-MIL-88(NH₂) can be produced. This material also exhibits high stability in basic solutions and biofluids and possesses high peroxidase-mimicking activity, which can be utilized to produce long-lasting chemiluminescence (CL) from luminol and H₂O₂. Moreover, acting as the peroxidase-mimic, the Fe/Co-TPY-MIL-88(NH₂) MOF can form the enzymatic cascade with glucose oxidase (GOx) for biomarker detection. When applied to detect extracellular vesicles (EVs), the MOF material and GOx are brought to the proximity on the EVs through two surface proteins, which triggers the enzyme cascade to produce high CL from glucose and luminol. EVs within the concentration range of 5 × 10⁵ to 4 × 10⁷ particles/mL can be detected with an LOD of 1 × 10⁵ particles/mL, and the method can be used to analyze EV contents in human serum without sample preparation and EV purification. Overall, our work demonstrates that the high versatility and tunability of the MOF structures could bring in significant benefits to biosensing and enable ultrasensitive detection of biomarkers with judicious material designs.

Metal-Organic Frameworks Nanocarriers for Functional Nucleic Acid Delivery in Biomedical Applications

Metal-organic frameworks (MOFs), a distinctive funtionalmaterials which is constructed by various metal ions and organic molecules, have gradually attracted researchers' attention from they were founded. In the last decade, MOFs emerge as a biomedical material with potential applications due to their unique properties. However, the MOFs performed as nanocarriers for functional nucleic acid delivery in biomedical applications rarely summarized. In this review, we introduce recent developments of MOFs for nucleic acid delivery in various biologically relevant applications, with special emphasis on cancer therapy (including siRNA, ASO, DNAzyme, miRNA and CpG oligodeoxynucleotides), bioimaging, biosensors and separation of biomolecules. We expect the accomplishment of this review could benefit certain researchers in biomedical field to develop novel sophisticated nanocarriers for functional nucleic acid delivery based on the promising material of MOFs.

Construction of a novel "self-regenerative" electrochemical biosensor based on metal-organic frameworks and its application to the detection of Mycoplasma ovine pneumonia

This study aimed to prepare a novel "self-regenerative" electrochemical biosensor by successively modifying gold nanoparticles, four-arm polyethylene glycol-NH₂, and NH₂-MIL-53 (Al) (MOF) on the glassy carbon electrode interface. A hairpin G-triplex-mediated DNA (G3 probe) as a part of the mycoplasma ovine pneumonia (MO) gene was loosely adsorbed to MOF. Based on the mechanism of hybridization induction, the G3 probe could effectively detach from the MOF only after introducing the target DNA. Subsequently, its guanine-rich nucleic acid sequences were exposed to solution of methylene blue. As a result, the diffusion current of the sensor system showed a sharp decline. The developed biosensor showed excellent selectivity, and the concentration of target DNA exhibited a good correlation in the range 10^-10 to 10^-6 M with a detection limit of 1.00 pM (S/N = 3), even in 10% goat serum. Most interestingly, this biosensor interface automatically started the regeneration program. Moreover, regeneration could be effectively achieved at least seven times, and the recovery rate of the electrode interface and sensing efficiency was up to 90%. Additionally, this platform could be used for other clinical assays in various systems by simply changing the DNA sequence of the probe.

Metal Organic Framework-Based Bio-Barcode CRISPR/Cas12a Assay for Ultrasensitive Detection of MicroRNAs

CRISPR/Cas12a has shown great potential in molecular diagnostics, but its application in sensing of microRNAs (miRNAs) was limited by sensitivity and complexity. Here, we have sensitively and conveniently detected microRNAs by reasonably integrating metal-organic frameworks (MOFs) based biobarcodes with CRISPR/Cas12a assay (designated as MBCA). In this work, DNA-functionalized Zr-MOFs were designed as the converter to convert and amplify each miRNA target into activators that can initiate the trans-cleavage activity of CRISPR/Cas12a to further amplify the signal. Such integration provides a universal strategy for sensitive detection of miRNAs. By tuning the complementary sequences modified on nanoprobes, this assay achieves subattomolar sensitivity for different miRNAs and was selective to single-based mismatches. With the proposed method, the expression of miR-21 in different cancer cells can be assessed, and breast cancer patients and healthy individuals can be differentiated by analyzing the target miRNAs extracted from serum samples, holding great potential in clinical diagnosis.

Size-matched hydrogen bonded hydroxylammonium frameworks for regulation of energetic materials

Size matching molecular design utilizing host-guest chemistry is a general, promising strategy for seeking new functional materials. With the growing trend of multidisciplinary investigations, taming the metastable high-energy guest moiety in well-matched frameworks is a new pathway leading to innovative energetic materials. Presented is a selective encapsulation in hydrogen-bonded hydroxylammonium frameworks (HHF) by screening different sized nitrogen-rich azoles. The size-match between a sensitive high-energy guest and an HHF not only gives rise to higher energetic performance by dense packing, but also reinforces the layer-by-layer structure which can stabilize the resulting materials towards external mechanic stimuli. Preliminary assessment based on calculated detonation properties and mechanical sensitivity indicates that HHF competed well with the energetic performance and molecular stability (detonation velocity = 9286 m s-1, impact sensitivity = 50 J). This work highlights the size-matched phenomenon of HHF and may serve as an alternative strategy for exploring next generation advanced energetic materials.

Coordination Polymers from Biphenyl-Dicarboxylate Linkers: Synthesis, Structural Diversity, Interpenetration, and Catalytic Properties

The present work explores two biphenyl-dicarboxylate linkers, 3,3'-dihydroxy-(1,1'-biphenyl)-4,4'-dicarboxylic (H4L1) and 4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic (H4L2) acids, in hydrothermal generation of nine new compounds formulated as [Co2(μ2-H2L1)2(phen)2(H2O)4] (1), [Mn2(μ4-H2L1)2(phen)2]n·4nH2O (2), [Zn(μ2-H2L1)(2,2'-bipy)(H2O)]n (3), [Cd(μ2-H2L1) (2,2'-bipy)(H2O)]n (4), [Mn2(μ2-H2L1)(μ4-H2L1)(μ2-4,4'-bipy)2]n·4nH2O (5), [Zn(μ2-H2L1)(μ2-4,4'-bipy)]n (6), [Zn(μ2-H2L2)(phen)]n (7), [Cd(μ3-H2L2)(phen)]n (8), and [Cu(μ2-H2L2) (μ2-4,4'-bipy)(H2O)]n (9). These coordination polymers (CPs) were generated by reacting a metal(II) chloride, a H4L1 or H4L2 linker, and a crystallization mediator such as 2,2'-bipy (2,2'-bipyridine), 4,4'-bipy (4,4'-bipyridine), or phen (1,10-phenanthroline). The structural types of 1-9 range from molecular dimers (1) to one-dimensional (3, 4, 7) and two-dimensional (8, 9) CPs as well as three-dimensional metal-organic frameworks (2, 5, 6). Their structural, topological, and interpenetration features were underlined, including an identification of unique two- and fivefold 3D + 3D interpenetrated nets in 5 and 6. Phase purity, thermal and luminescence behavior, as well as catalytic activity of the synthesized products were investigated. Particularly, a Zn(II)-based CP 3 acts as an effective and recyclable heterogeneous catalyst for Henry reaction between a model substrate (4-nitrobenzaldehyde) and nitroethane to give β-nitro alcohol products. For this reaction, various parameters were optimized, followed by the investigation of the substrate scope. By reporting nine new compounds and their structural traits and functional properties, the present work further outspreads a family of CPs constructed from the biphenyl-dicarboxylate H4L1 and H4L2 linkers.

Biophysical characterization and in vitro imaging of carbonized MOFs

Nanoparticles have been widely used in biological imaging and treatments of various diseases, especially for studies of tumors, due to their high efficiency in drug delivery and many other functions. Metal-organic frameworks have been an important research area in recent years because of advantages such as large apertures, adjustable structural compositions, adjustable sizes, multifunctionality, high drug loading, good biocompatibility and so on, and they show promise as multifunctional drug carriers. In this study, a carbonized MOF with photothermal therapeutic potential and dual-mode imaging capability was prepared. The biophysical properties of MIL-100 and C-MIL nanoparticles were determined, such as particle size, zeta potential and saturation magnetization strength. CCK-8 cell assays and mouse HE sections confirmed that C-MIL nanoparticles have good in vitro and in vivo biocompatibility. The solution temperature of C-MIL nanoparticles reached 58.1 °C during sustained laser irradiation at 808 nm, which confirmed the photothermal potential of the nanoparticles. Moreover, in biological imaging, C-MIL nanoparticles showed the ability to support in vitro nuclear magnetic and photoacoustic dual-mode imaging. C-MIL nanoparticles provide new options for tumor therapy, drug delivery and biological imaging.

Revisiting molecular adsorption: unconventional uptake of polymer chains from solution into sub-nanoporous media

Adsorption of polymers from the solution phase has been extensively studied to cope with many demands not only for separation technologies, but also for the development of coatings, adhesives, and biocompatible materials. Most studies hitherto focus on adsorption on flat surfaces and mesoporous adsorbents with open frameworks, plausibly because of the preconceived notion that it is unlikely for polymers to enter a pore with a diameter that is smaller than the gyration diameter of the polymer in solution; therefore, sub-nanoporous materials are rarely considered as a polymer adsorption medium. Here we report that polyethylene glycols (PEGs) are adsorbed into sub-nanometer one-dimensional (1D) pores of metal-organic frameworks (MOFs) from various solvents. Isothermal adsorption experiments reveal a unique solvent dependence, which is explained by the balance between polymer solvation propensity for each solvent and enthalpic contributions that compensate for potential entropic losses from uncoiling upon pore admission. In addition, adsorption kinetics identify a peculiar molecular weight (MW) dependence. While short PEGs are adsorbed faster than long ones in single-component adsorption experiments, the opposite trend was observed in double-component competitive experiments. A two-step insertion process consisting of (1) an enthalpy-driven recognition step followed by (2) diffusion regulated infiltration in the restricted 1D channels explains the intriguing selectivity of polymer uptake. Furthermore, liquid chromatography using the MOFs as the stationary phase resulted in significant PEG retention that depends on the MW and temperature. This study provides further insights into the mechanism and thermodynamics behind the present polymer adsorption system, rendering it as a promising method for polymer analysis and separation.

Metal-Organic Frameworks as Versatile Media for Polymer Adsorption and Separation

Molecular recognition is of paramount importance for modern chemical processes and has now been achieved for small molecules using well-established host-guest chemistry and adsorption-science principles. In contrast, technologies for recognizing polymer structure are relatively undeveloped. Conventional polymer separation methods, which are mostly limited in practice to size-exclusion chromatography and reprecipitation, find it difficult to recognize minute structural differences in polymer structures as such small structural alterations barely influence the polymer characteristics, including molecular size, polarity, and solubility. Therefore, most of the polymeric products being used today contain mixtures of polymers with different structures as it is challenging to completely control polymer structures during synthesis even with state-of-the-art substitution and polymerization techniques. In this context, development of novel techniques that can resolve the challenges of polymer recognition and separation is in great demand, as these techniques hold the promise of a new paradigm in polymer synthesis, impacting not only materials chemistry but also analytical and biological chemistry.In biological systems, precise recognition and translation of base monomer sequences of mRNA are achieved by threading them through small ribosome tunnels. This principle of introducing polymers into nanosized channels can possibly help us design powerful polymer recognition and separation technologies using metal-organic frameworks (MOFs) as ideal and highly designable recognition media. MOFs are porous materials comprising organic ligands and metal ions and have been extensively studied as porous beds for gas separation and storage. Recently, we found that MOFs can accommodate large polymeric chains in their nanopores. Polymer chains can spontaneously infiltrate MOFs from neat molten and solution phases by threading their terminals into MOF nanochannels. Polymer structures can be recognized and differentiated due to such insertion processes, resulting in the selective adsorption of polymers on MOFs. This enables the precise recognition of the polymer terminus structure, resulting in the perfect separation of a variety of terminal-functionalized polymers that are otherwise difficult to separate by conventional polymer separation methods. Furthermore, the MOFs can recognize polymer shapes, thus enabling the large-scale separation of high purity cyclic polymers from the complex crude mixtures of linear polymers, which are used as precursor materials in common cyclization reactions. In solution-phase adsorption, many factors, including molecular weight, terminal groups, polymer shape, polymer-MOF interaction, and coexisting solvent molecules, influence the selective adsorption behavior; this yields a new liquid chromatography-based polymer separation technology using an MOF as the stationary phase. MOF-packed columns, in which a novel separation mode based on polymer insertion into the MOF operates under a dynamic insertion/rejection equilibrium at the liquid/solid interface, exhibited excellent polymer separation capability. The polymer recognition principle described in this study thus has a high probability for realizing previously unfeasible polymer separations based on monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences in synthetic polymers and biomacromolecules.

Theoretical investigation of conformational deviation of the human parallel telomeric G-quadruplex DNA in the presence of different salt concentrations and temperatures under confinement

Various experimental reports address the stability of G-quadruplex DNA inside a close confinement such as α-hemolysin, nanocavity water pool and different metal-organic-frameworks (MOFs). To understand the conformational change of G-quadruplex DNA at the atomistic level, we have carried out a total of 40 μs simulation run under both non-polar and polar confinement conditions. To investigate the dynamics, we have considered two different KCl salt concentrations, i.e., 0.47 M (minimal salt concentration) and higher than 2 M (higher salt concentration), at two distinct temperatures, 300 K and 350 K. Here, we have observed that the human telomeric G-quadruplex DNA deviates more from its crystal structure at minimal salt concentration under both non-polar and polar confinement conditions. Besides, the loop regions deviate and fluctuate more compared to the other regions, i.e., sugar-phosphate backbone and tetrad regions. The presence of K+ ions is found to be primarily responsible for this phenomenon. From the spatial density function (SDF) plots, a higher density of K+ ions is observed in the backbone region. Furthermore, from the residue-wise first solvation shell estimation, we have noticed that the K+ ions mainly accumulate in the tetrad region under both non-polar and polar confinement conditions due to which the tetrad regions are more rigid than the loop regions. Higher salt concentration results in increased rigidity of the G-quadruplex DNA. Our study provides valuable insight into the conformational deviation of the G-quadruplex DNA under nanoconfinement conditions.

Design of metal-organic framework composites in anti-cancer therapies

Metal-organic frameworks are a class of new and promising anti-cancer materials. MOFs with adjustable pore size, large specific surface area, diverse structure, and excellent chemical and physical properties make them a class of effective protection carriers for anti-cancer substances. This review is centered on the core point of "anti-cancer" and discusses MOFs' research progress in anti-cancer therapies. Firstly, we provided readers with the different types of MOFs, their preparation strategies and the resulting structures. Then, different MOF composites and their biological applications were systematically presented. The specificity of biomolecules endows MOFs with broader anti-cancer applications, while MOFs can protect the drugs and biomolecules to make the best of a challenging situation. Finally, we elucidated a comprehensive overview of the biological applications of MOFs, including research hotspots as drug delivery and biomolecule carriers. Besides, we looked forward to the future developments of MOFs in the field of anti-cancer therapies. As a class of novel materials, the anti-cancer applications of MOFs are extended through the combination of different materials and different methods to improve their efficacy.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

Construction of Molecular Sensing and Logic Systems Based on Site-Occupying Effect-Modulated MOF-DNA Interaction

Interactions between metal-organic frameworks (MOFs) and nucleic acids are of great importance in molecular assembly. However, current MOF-nucleic acid interactions lack diversity and are normally realized in an uncontrollable manner. Herein, the interaction of zirconium-based MOFs (Zr-MOFs) with nucleic acids is enabled by the formation of Zr-O-P bonds and further manipulated by a phosphate-induced site-occupying effect. Covering Zr ions in clusters of MOFs with phosphates impedes the formation of Zr-O-P bonds with nucleic acids, rendering the MOF-nucleic acid interaction tunable and stimulus-responsive. Notably, the experimental results demonstrate that various phosphates, Zr-MOFs, and nucleic acids can all be adopted in the tunable interaction. On the basis of these findings, fluorescent DNA and typical Zr-MOFs are proposed as functional probe-quencher pairs to establish molecular sensing and logic systems. Accordingly, alkaline phosphatase and inorganic pyrophosphatase can be quantified simultaneously, and the overall relation of different phosphates and phosphatases is facilely displayed. The work provides a general strategy for modulating MOF-nucleic acid interactions, which is conducive to the development of molecular intelligent systems.

Cobalt Metal-Organic Frameworks Incorporating Redox-Active Tetrathiafulvalene Ligand: Structures and Effect of LLCT within the MOF on Photoelectrochemical Properties

Understanding the effect of charge transfer on the physical properties of metal-organic frameworks (MOFs) is essential for designing multifunctional MOF materials. In this work, three redox-active tetrathiafulvalene (TTF)-based MOFs, formulated as [Co₆L₆(bpe)₆(EtOH)₂(MeOH)₂(H₂O)]_n·5nH₂O (1), [Co₅(μ₃-OH)₂L₄(bpe)₂]_n (2), and [CoL(bpa)(H₂O)]_n·2nH₂O (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bis(4-pyridyl)ethane), are crystallographically characterized. Complexes 1 and 3 are two-dimensional (2D) coordination polymers, and 2 features an unusual three-dimensional (3D) MOF. The structure of 2 contains a cluster chain constructed from μ₂-O bridged pentanuclear cluster subunits, which is first found for 3D MOFs. Complexes 1 and 2 are comprised of the same ligands L and bpe but with different multidimensional configuration, and complexes 1 and 3 have the same 2D layered structures with the same ligand L but with different conjugation ligand bpe/bpa, which provide a good comparison for the structure-property relationship. The charge-transfer (CT) interactions within MOF 1 are stronger than those of 2 due to the closer packing of electron donor (D) L and electron acceptor (A) bpe in 1, and no CT occurs within MOF 3 because of the unconjugated bpa. The order of photocurrent density is 1 > 2 ≫ 3, which is in accordance with that of CT interactions. Further analysis reveals that the CT interactions within the MOF are not beneficial for the supercapacitance which is verified by the highest supercapacitance performance of 3. This work is the first study of the structures and CT effects on the supercapacitance performance.