Latest ArticlesAlthough the construction of specific functional crystalline materials is still challenging, the multi-component molecular assembly has become a key solution for the design of functional materials. Here, we report a hydrogen-bonded organic framework (HOF) material FJU-360 constructed from disodium 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate (SSY) and terephthalimidamide. The charge-assisted hydrogen bonding between amidinium and sulfonate makes FJU-360 produce much stronger fluorescence than SSY, and can be used as a luminescence sensor to rapidly quench aniline through luminescence quenching. FJU-360 is sensitive and highly selective for the detection of aniline, and the detection limit reached 3.2 nmol/L, which is the lowest value reported currently. The mechanism of aniline response was analyzed through the aniline@FJU-360 single crystal structure, and the luminescence mechanism was clarified through density function theory calculations. This work is an important step towards the rational synthesis and assembly of sensing materials.
Corneal wound closure for surgical eye surgeries or accidents is typically performed to prevent pathogens from the sterile intraocular environment and avoid potential postoperative complications. Tissue adhesives are increasingly employed for corneal wound closure with superior treatment efficiency and less adverse effects. In this study, we successfully develop a novel corneal adhesive based on functionally coupled PEG-lysozyme (PEG-LZ) hydrogels for wound closure after surgical eye surgeries. PEG-LZ hydrogels have plenty of micropores and gradually decreased pore size with increasing concentration from 10%, 15% to 20% (w/v), in which PEG-LZ (15%) represents the suitable pH value, gelation time and elastic modulus. PEG-LZ hydrogels have no in vitro cytotoxicity and excellent ex vivo wound closure effectiveness in porcine eyes. The in vivo wound sealant in rabbit eyes by PEG-LZ hydrogels presents a superior therapeutic effect compared with the conventional methods of stromal hydration and suture, in terms of the wound closure percent, mean corneal thickness, percent of wound gaping, and the Descemet membrane detachment. PEG-LZ hydrogels do not induce obvious histological pathology changes. The PEG-LZ corneal adhesive is considered as a tissue adhesive alternative for wound closure after surgical eye surgeries.
Solid-state electrolytes (SSEs) with high ionic conductivity, mechanical stability, and high thermal stability, as well as the stringent requirement of application in high-temperature fuel cells and lithium-ion batteries is receiving increasing attention. Polymer nanocomposites (PNCs), combining the advantages of inorganic materials with those of polymeric materials, offer numerous opportunities for SSEs design. In this work, we report a facile and general one-pot approach based on polymerization-induced microphase separation (PIMS) to generate PNCs with bi-continuous microphases. This synthetic strategy transforms a homogeneous liquid precursor consisting of polyoxometalates (POMs, H3PW12O40, Li7[V15O36(CO3)]), poly(ethylene glycol) (PEG) macro-chain-transfer agent, styrene and divinylbenzene monomers, into a robust and transparent monolith. The resulting POMs are uniformly dispersed in the PEG block (PEG/POM) to form a conducting pathway that successfully realizes the effective transfer of protons and lithium ions, while the highly cross-linked polystyrene domains (P(S-co-DVB)) as mechanical support provide outstanding mechanical properties and thermal stability. As the POM loading ratio up to 35 wt%, the proton conductivity of nanocomposite reaches as high as 5.99 × 10-4 S/cm at 100 ℃ in anhydrous environment, which effectively promotes proton transfer under extreme environments. This study broadens the application of fuel cells and lithium-ion batteries in extreme environments.
Transforming immature DCs into mature state to activate cellular immunity is a critical step in initiating immunoprophylaxis and immunotherapy. Lipopolysaccharides (LPS) can promote DCs maturation by binding receptor on DCs surface, but their clinical application is limited due to biological toxicity. Although many LPS analogues have been developed, complex synthesis and purification hinder their practical application. Here, we propose a novel and simple strategy to synthesize LPS analogues with adjustable structural units. Using monomer units similar to the key functional groups of LPS, we synthesize LPS analogues with different group ratios by RAFT polymerization. The obtained analogues have little negative effect on cell viability. Compared with LPS, the analogues show greater promoting effect on DCs maturation. And the analogues can be applied to different scenarios since the degrees of promoting DCs maturation by LPS analogues with different group ratios are different. This strategy provides a new direction for synthesizing LPS analogues, and it has the potential to produce LPS analogues on a large scale with tunable promoting DCs maturation effect.
Nuclear magnetic resonance (NMR) spectroscopy has provided many powerful tools for the study of dynamic processes. Among the reported methods, chemical exchange saturation transfer (CEST) is more suitable for systems with slow exchange rates, and there will be promising in the detection and dynamic mechanism of metastable substances. It has been widely used in magnetic resonance imaging (MRI), however whether it is applicable in the field of chemical kinetics needs more examples. Here we studied, as a proof of concept, the kinetics of the slow chemical exchange between the two N-methyl protons of N, N-dimethylacetylamide (DMA), exploiting QUantifying Exchange using Z-spectrum (QUEZS) and QUantifying Exchange using Saturation Time (QUEST) methods. It turned out that both of QUEZS and QUEST could give the corresponding exchange rates, showcasing the capability of this method to provide accurate kinetic data under a range of temperatures. Our results clearly demonstrated the reliability of CEST-based techniques as a tool for dynamic kinetics by NMR.
Riboflavin (RF, vitamin B2) is an essential vitamin and has been considered as a promising natural photosensitizer for photodynamic therapy (PDT). However, further exploration of RF in antitumor application was limited by its poor cellular uptake. In this study, using cell-penetrating peptides Arg8, (Cha-Arg)3 and small molecule triphenylphosphine (TPP) as delivery compounds, three RF conjugates were prepared to increase the accumulation of RF in cells, termed as Arg8-RF, (Cha-Arg)3-RF and TPP-RF, respectively. Compared with TPP-RF and Arg8-RF, (Cha-Arg)3-RF exhibited better cell internalization and stronger cytotoxicity against HeLa cells upon exposure to blue light. Further researches proved that (Cha-Arg)3-RF generated reactive oxygen species (ROS) under irradiation, which could indiscriminately destroy endogenous proteins and mitochondria, ultimately inducing cell death. This work provides a new approach to explore RF as a natural photosensitizer for antitumor photodynamic therapy.
Phosphorylated di-, tri- and tetra-saccharides of β-1, 2-mannan antigen derived from Candida albicans (C. albicans) cell wall were synthesized and covalently conjugated with keyhole limpet hemocyanin (KLH) and human serum albumin (HSA) via a bifunctional linker under mild conditions. The semi-synthetic β-1, 2-mannoside–KLH conjugates were evaluated for the immunization of BALB/c mice. The ELISA results revealed that all three conjugates could elicit high levels of specific IgG antibodies and the acquired antisera could effectively identify the β-1, 2-mannan epitope. Furthermore, the immunofluorescence and flow cytometry assays also uncovered that the induced antibodies, especially that obtained from immunization with β-1, 2-mannotriose–KLH conjugate (1b), could bind well to fungi cell. Eventually, the structure–immunogenicity relationship analysis of β-mannan showed that the length of oligo-β-mannoses had a big impact on their immunogenicity and β-1, 2-mannotriose showed the strongest immunogenicity. The results suggested the great potential of β-1, 2-mannotriose–KLH conjugate as an antifungal vaccine candidate.
Reasonable construction of sulfur host with high conductivity, large sulfur storage gap, strong chemical adsorption, and fast oxidation–reduction kinetics of polysulfide is very significant for its practical use in lithium-sulfur batteries (LSBs). In this paper, the surface modification of MIL-88A(Fe) is carried out by Dawson-type polyoxometalate (POM), and a hollow capsule shell material with P2W18, Fe3O4, and C components is synthesized by the subsequent carbonization process. When applied as the sulfur host, the hollow capsule shell material can efficiently improve the conductivity of sulfur electrode and restrain the volumetric change of active sulfur while charging and discharging. On this foundation, electrochemical analysis and density functional theory (DFT) calculation show that the P2W18 on the outer layer of the capsule shell have effective electrocatalytic activity and potent chemical bond on the lithium polysulfides (LiPSs), which is helpful to block the shuttle effect. Therefore, the as-assembled LSBs display the outstanding specific capacity and prominent cycle stability. Specifically, it delivers an excellent reversible capacity of 1063 mAh/g after 100 cycles of charge–discharge at a rate of 0.5 C, accounting for a preservation by 96% in comparison to that of the initial cycle. Moreover, even after 2000 cycles at 1 C, the reversible specific capacity of 585 mAh/g can still be maintained with an average decay rate of only 0.021%.
Selective cleavage of robust C−C bonds to harvest value-added aromatic oxygenates is an intriguing but challenging task in lignin depolymerization. Photocatalysis is a promising technology with the advantages of mild reaction conditions and strong sustainability. Herein, we show a novel urchin-like Nb2O5 hollow microsphere (U-Nb2O5 HM), prepared by one-pot hydrothermal method, are highly active and selective for Cα−Cβ bond cleavage of lignin β-O-4 model compounds under mild conditions, achieving 94% substrate conversion and 96% C−C bond cleavage selectivity. Systematic experimental studies and density functional theory (DFT) calculations revealed that the superior performance of U-Nb2O5 HMs arises from more exposed active sites, more efficient free charge separation and the active (001) facet, which facilitates the activation of Cβ−H bond of lignin models and generate key Cβ radical intermediates by photogenerated holes, further inducing the Cα−Cβ bond cleavage to produce aromatic oxygenates. This work could provide some suggestions for the fabrication of hierarchical photocatalysts in the lignin depolymerization system.
The tuning of olefin-polymerization catalyst properties through ligand modifications is efficient but requires complicated and costly syntheses. In this contribution, a simple Bu2Mg-based cocatalyst strategy is designed that can simultaneously enhance the catalytic properties (activity, thermal stability, polymer molecular weight, branching density, melting point, etc.) of various nickel catalysts (α-diimine nickel, pyridine imine nickel and iminopyridine-N-oxide nickel) in ethylene polymerization, and enable great product morphology control. For example, a simple α-diimine nickel catalyst can demonstrate polymerization activity of up to 1.29 × 107 g mol−1 h−1 and molecular weight of up to 1.90 × 106 g/mol in the presence of Bu2Mg cocatalyst. The resulting polyethylenes exhibit excellent mechanical properties, with tensile stress of up to 47.4 MPa and strain of up to 1020%. This cocatalyst strategy is generally applicable to different nickel catalysts, and can lead to property enhancement in ethylene copolymerization with a series of polar comonomers such as methyl 10-undecylenate, 10-undecylenic acid and 10-undecenol.
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