Latest ArticlesAs a member of the curcuminoid compound family, curcumin (Cur) has many interesting therapeutic properties. However, its low aqueous solubility and stability have resulted in poor bioavailability and restricted clinical efficacy. Based on size matching, β-cyclodextrin polymer (β-CDP), with its hydrophilic polymer chains and hydrophobic cavities, can form an inclusion complex with Cur. To improve the water solubility and stability of Cur, a simple and eco-friendly grinding method was designed to form β-CDP inclusion complexes. According to the Boltzmann–Hamel's method and Job's method, the molar ratio of the β-CD unit in β-CDP to Cur was determined to be 1 : 1. The diffusion coefficient and diffusion activation energy of Cur-β-CDP were calculated in an electrochemical study. This supramolecular complex worked well in vitro to inhibit the proliferation of hepatoma carcinoma cells HepG2. Remarkably, this method visibly reduced the undesirable side effects on normal cells, without weakening the anti-cancer activity of the drugs. We expect that the obtained host–guest complex will provide a new approach for delivering natural drug molecules, having low water solubility.
A novel type sandwich-like composite films composed of ZIF-8 and CdTe QDs were successfully constructed through facile layer-by-layer assembly strategy and their potential applications were also explored. Based on the limitation effects of the aperture of ZIF-8, CdTe QDs/ZIF-8 fluorescent composite films exhibit obvious selective optical response toward hydrogen peroxide and folic acid. Furthermore, tunable colorful light emission composite films in the red-green region are obtained through incorporating two different sized QDs and ZIF-8 films into one composite films.
The unveiling of MOF growth mechanism is hampered by the lack of fundamental knowledge about the very early stage of nucleation, especially the form and ratio of molecular species in the solution for crystal growth. Herein, we report the detection of growth species for a series of MOFs with mono-linker, Cu-MOF-2-BDC and Cu-MOF-2-NDC, and two linkers, MTV-MOF-2-(C4H4), by high resolution ESI-MS, where a large variety of Cu-containing species are identified unambiguously. The solvent molecules such as H2O, methanol and DMF participate in the formation of these species, other than ethanol. Furthermore, in the growth solution of MTV-MOF-2-(C4H4), growth species containing two different organic linkers are observed. The feeding ratio is not the only factor controlling the distribution of growth species for MTV-MOFs, but also the solvent involves in coordination, an aspect usually overlooked previously.
Rational construction of fine-tuning and precisely controllable topological nanostructures based on supramolecular self-assembly system remains a challenge. Herein, coumarin-12-crown-4 (1) as a building block was synthesized by one-pot method and showed reversible high stereo-selective photodimerization (anti-head-to-head dimer (anti-HH-1): syn-head-to-head dimer (syn-HH-1) = 10.8:1) and photocleavage. Helical nanobelts were formed by the self-assembly of 1 through asymmetrical H-bonds, which were in concordance with the crystal state superstructure. Upon irradiation with 365 nm light, these nanobelts transformed into nanoballs which were constructed by three building blocks. Further, we investigated the photoreaction of 1 and got two pure covalent dimers (anti-HH-1 and syn-HH-1). The anti-HH-1 self-assembled into hollow micro-vesicles. The transformation of superstructures based on photo-controlled multiple blocks shines a light to the research on the relationship between molecules and superstructures.
To obtain high-efficiency flame retardancy of epoxy resins, a cyclophosphazene derivative tri-(o-henylenediamino)cyclotriphosphazene (3ACP) was successfully synthesized and used as a curing agent for the thermosetting of an epoxy resin system. The flame retardant properties, thermal stability, and pyrolysis mechanism of the resultant thermosets were investigated in detail. The experiments indicated that the synthesized thermoset achieved a UL-94 V-0 rate under a vertical burning test as well as a limiting oxygen index (LOI) of 29.2%, which was able to reach V-0 even when a small amount of 3ACP was incorporated. Scanning electronic microscopic observation demonstrated that the char residue of the thermosets was extremely expanded after the vertical flame test. Thermal analysis showed that the samples had a lower initial decomposition temperature when 3ACP was introduced into the epoxy resin systems. This indicates that the carbonization ability of the thermosets was significantly improved at elevated temperatures. In addition, the incorporation of 3ACP can effectively suppress the release of combustible gases during the pyrolysis process, and the decomposition of E-44/DDS-3ACP curing systems also promotes the formation of polyphosphoramides charred layer in the condensed phase. The investigation on the chemical structures of both the gaseous and condensed phase pyrolysis process confirmed the flame-retardant mechanism of the 3ACP-cured epoxy resins. Therefore, the nonflammable halogen-free epoxy resin developed in this study has potential applications in electric and electronic fields for environment protection and human health.
Surface engineering that could modulate the surface shape to be endowed with the high specific surface ratio, abundant chemical dangling bonds and improved defects exposure is highly desired and needs further exploring. Here, we report a facile strategy of surface engineering on decorating the controllable segmented copper-iron nanowires arrays (Cu-Fe NWs) with their respective hydroxides. Specifically, the pristine segmented Cu-Fe NWs are firstly synthesized via sequentially electrodepositing Cu NWs and Fe NWs inside the nanochannels of anode aluminum oxide (AAO) template. Subsequently, the surface and interface of Cu-Fe NWs are wet-chemically etched, in which the metallic Cu and Fe are partially converted into Cu(OH)x nano-fibrous roots (NFRs) and FeO(OH)y nanoparticles (NPs), and finally decorate around the respective outer-surface of Cu NWs and Fe NWs segments. As one case of the applications in hydrogen evolution reaction (HER), our surface-modified Cu-Fe NWs exhibit improved catalytic activity compared with Fe NWs.
Aflatoxin B1 (AFB1) is one of the most common mycotoxins that threatens human health. As single-stranded oligonucleotides with high affinity and specificity, aptamers have incomparable effect on the targeted detection of AFB1. Herein, after 11 rounds of selection and analysis using a modified affinity chromatography-based SELEX strategy, the truncated 37 nt aptamer AF11–2 was successfully obtained. The aptamer shows good detection performance for AFB1, and can sensitively detect AFB1 in the range of 100–1000 nmol/L, with a detection limit of 42 nmol/L. In the detection of pretreated edible peanut oil samples, AF11–2 aptamer also showed a high recovery rate and good stability for AFB1, and achieved satisfactory results. In addition, AF11–2 aptamer can significantly enhance the fluorescence ability of AFB1, which is not available in traditional Afla17–2–3 aptamer. After molecular docking analysis, it was found that AF11–2 and Afla17–2–3 had different nucleotide binding sites for AFB1. Afla17–2–3 binds to the carbonyl O of AFB1, while AF11–2 binds to the pyrrolic O of AFB1, which may be the main reason that AF11–2 can enhance the fluorescence of AFB1.
Three polymorphs (forms Ⅰ, Ⅱ and Ⅴ) of isonicotinamide (INA) were mechanically flexible and exhibited one-dimensional (1D) plasticity. Anisotropic intermolecular interactions contribute to the plasticity of single crystals: weak dispersive interactions between slip planes such as 1D columns in forms Ⅰ and Ⅱ or 2D layers in form Ⅴ were stabilized by strong hydrogen bonds, allowing the layer or column's surface to glide smoothly without hindrance. The disparity of intermolecular interactions on plastic properties of INA polymorphic crystals was confirmed by energy framework analysis, nanoindentation tests and micro-Raman spectroscopy. The crystal which exhibits plastic property provides a promising application in pharmaceuticals and material sciences.
A hydrogen fluoride-free and chloro-free method for synthesizing LiPF6 was developed. Employing CaF2 as the direct fluorinating reagent instead of hydrogen fluoride made it much safer and more environment-friendly than conventional methods and reduced the metal residues in product owing to the relatively low-acid reaction conditions less corrosive to equipments. The use of P2O5 as phosphorus source instead of traditionally employed PCl5 significantly reduced the chloro residue in product. Ca(H2PO4)2, the only by-product of the process, could be easily converted into Ca3(PO4)2, a best-selling chemical. The above advantages not only reduce the production costs by ca. 20%, but also significantly improve the product purity. The fluorine-oxygen exchange reaction is a completely new technique for LiPF6 production and may bring about technological revolution in the related industry.
Nanocrystals are of great value in delivering poorly soluble drugs as a technique enables enhanced dissolution and bioavailability. The bottom-up technique allows better control of particle properties. However, the commonly used organic solvents are hazardous to environment and operators, and always lead to large particle size and wide size distribution due to failure on controlling the nucleation and crystal growth. The situation is exacerbated in scale-up production. Therefore, in the proof-of-concept study, we evaluated the feasibility of green and controllable fabrication of drug nanocrystals by using biocompatible ionic liquids (ILs) as solvents. Choline based ILs (Ch-ILs) were synthesized via metathesis reactions. Pure paclitaxel nanocrystals of high quality were obtained from Ch-ILs with surface tension higher than 42 mN/m. The sizes were below 250 nm, while the polydispersity indexes were lower than 0.25. Compared with ethanol, choline lactate is superior in controlling the size of the nanocrystals in scale-up production, where the drug concentration was increased by 6 times. The underlying mechanism may be due to the high viscosity and low surface tension of the ILs, which are supposed to benefit homogeneous and burst nucleation. Ch-ILs can be recycled from the process and recovery rate reached 91.1%. Moreover, the applicability of the green technique was validated in a wider range of model drugs and Ch-ILs. In conclusion, ILs are potent solvents in bottom-up technique for green and controllable fabrication of nanocrystals.
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