Effective transfection of genetic molecules such as DNA usually relies on vectors that can reversibly uptake and release these molecules, and protect them from digestion by nuclease. Non-viral vectors meeting these requirements are rare due to the lack of specific interactions with DNA. Here, we design a series of four isoreticular metal-organic frameworks (Ni-IRMOF-74-II to -V) with progressively tuned pore size from 2.2 to 4.2 nm to precisely include single-stranded DNA (ssDNA, 11–53 nt), and to achieve reversible interaction between MOFs and ssDNA. The entire nucleic acid chain is completely confined inside the pores providing excellent protection, and the geometric distribution of the confined ssDNA is visualized by X-ray diffraction. Two MOFs in this series exhibit excellent transfection efficiency in mammalian immune cells, 92% in the primary mouse immune cells (CD4+ T cell) and 30% in human immune cells (THP-1 cell), unrivaled by the commercialized agents (Lipo and Neofect).

We report hyperpolarized Xe signal advancement by metal-organic framework (MOF) entrapment (Hyper-SAME) in aqueous solution. The 129Xe NMR signal is drastically promoted by entrapping the Xe into the pores of MOFs. The chemical shift of entrapped 129Xe is clearly distinguishable from that of free 129Xe in water, due to the surface and pore environment of MOFs. The influences from the crystal size of MOFs and their concentration in water are studied. A zinc imidazole MOF, zeolitic imidazole framework-8 (ZIF-8), with particle size of 110 nm at a concentration of 100 mg/mL, was used to give an NMR signal with intensity four times that of free 129Xe in water. Additionally, Hyper-SAME is compatible with hyperpolarized 129Xe chemical exchange saturation transfer. The 129Xe NMR signal can be amplified further by combining the two techniques. More importantly, Hyper-SAME provides a way to make detection of hyperpolarized 129Xe in aqueous solution convenient and broadens the application area of MOFs.

We report the use of metal–organic frameworks (MOFs) for the selective separation of nucleic acids (DNA and RNA) with different secondary structures through size, shape, length, and capability of conformational transition. Three MOFs with precisely controlled pore environments, Co-IRMOF-74-II, -III, and -IV, composed of Co2+ and organic linkers (II, III, and IV), respectively, were used for the inclusion of nucleic acid into their pores from the solution. This was proven to be a spontaneous process from disordered free state to restricted ordered state via circular dichroism (CD) spectroscopy. Three critical factors were identified for their inclusion: (1) size selection induced by steric hindrance, (2) conformation transition energy selection induced by stability, and (3) molecular weight selection. These selection rules were used to extract nucleic acids with flexible and unstable secondary structures from complex mixtures of multiple nucleic acids, leaving those with rigid and stable secondary structures in the mother liquor. This provides the possibility to separate and enrich nucleic acids in bulk through their different structure feature, which is highly desirable in genome-wide structural measurement of nucleic acids. Unlike methods that rely on specific binding antibodies or ligand, this MOF method is capable of selecting all kinds of nucleic acids with similar secondary structure features; therefore, it is suitable for the handling of a large variety and quantity of nucleic acids at the same time. This method also has the potential to gather information about the folding stability of biomolecules with secondary structures.

No abstract

To achieve better resolution and contrast in fluorescence techniques, time‐resolved fluorophores are promising constituents for probes in imaging and sensing, allowing for the elimination of background signals from scattering and short‐lived autofluorescence. Here a metal–organic framework (MOF) named Spiro‐MOF‐1 is designed with high thermally activated delayed fluorescence (TADF) persistence using a strategy of high rigidity to achieve a lifetime more than two times longer than that of pure linker. The rigid structure originated from spiro‐bi‐acridine unit is unambiguously revealed through 3D electron diffraction tomography (3D‐EDT). Furthermore, nanocrystals of Spiro‐MOF‐1 are successfully developed and modified with polyethylene glycol (PEG) as a biocompatible, time‐resolved fluorescent fluorophore with high TADF persistence, which exhibits a lifetime around 1 μs with no obvious decay under various bio‐mimicking environments, which has not been achieved by any other MOF‐based TADF emitter and small organic molecules. In further cell experiments, PEG‐modified nanocrystals exhibit a fluorescent signal that is more than 30 times longer than that of autofluorescence background in BGC823 cell line.

Stability of metal-organic frameworks (MOFs) under hydrogen is of particular importance for a diverse range of applications, including catalysis, gas separations, and hydrogen storage. Hydrogen in gaseous form is known to be a strong reducing agent and can potentially react with the secondary building units of a MOF and decompose the porous framework structure. Moreover, rapid pressure swings expected in vehicular hydrogen storage could create significant mechanical stresses within MOF crystals that cause partial or complete pore collapse. In this work, we examined the stability of a structurally representative suite of MOFs by testing them under both static (70 MPa) and dynamic hydrogen exposure (0.5 to 10 MPa, 1000 pressure cycles) at room temperature. We aim to provide stability information for development of near room-temperature hydrogen storage media based on MOFs and suggest framework design rules to avoid materials unstable for hydrogen storage under relevant technical conditions.

No abstract

A specificity fluorescence platform for probing of sequence-specific miRNA using fluorophore labeled DNA and metal–organic frameworks (MOFs) is developed. Ni-IRMOF-74-II can quench the fluorescence of four fluorescent dyes labeled in the single strand oligodeoxynucleotides (ssODNs), and fluorescence recovers in the presence of their target miRNA and can be detected in their corresponding channels. Furthermore, recovered fluorescence intensity has a linear relationship with the concentration of the target miRNA in the range from 1.25 to 100 nM at the four corresponding channels. This fluorescence sensor platform can detect several kinds of miRNA in the same system and at same time with the high specificity and negligible cross-reactivity.