Latest ArticlesThe serum cholesterol level is an important indicator of healthy and there is a great necessity for frequent cholesterol monitoring to some cardiovascular-related diseases, which puts forward higher requirements for point-of-care testing (POCT) of cholesterol. In this work, a cascade catalytic system of cholesterol is developed by encapsulation of cholesterol oxidase (ChOx) and PdCuAu nanoparticles into zeolitic imidazolate framework-L (ChOx/PCA@ZIF-L). Results indicate that ZIF-L carrier can significantly increase the catalytic activity of single or multiple enzymes, due to its high loading capacity and efficient molecular transport. Under the optimal conditions, the absorbance of reaction system performs linear relationships with the concentration of cholesterol in two intervals from 0.0005 mmol/L to 1.0000 mmol/L, with a limit of detection of 0.2176 µmol/L. The proposed colorimetric strategy based on ChOx/PCA@ZIF-L performs a good agreement with the results provided by chemiluminescence method for the serum cholesterol detection. Interestingly, a simple paper-based sensing system is constructed through a pre-reaction-transfer operation, which gets rid of the complex pre-processing requirements of traditional operations on filter paper. The presented strategy allows for the sensitive, convenient, costless assay of serum cholesterol, and paves a new way to design the POCT device for daily monitoring of healthy.
The most practical high-temperature proton exchange membranes (PEMs) are phosphoric acid (PA)-doped polymer electrolytes. However, due to the plasticizing effect of PA, it is a challenge to address the trade-off between the proton conductivity and the mechanical performance of these materials. Here, we report an effective strategy to fabricate robust high-temperature PEMs based on the in situ electrostatic crosslinking of polyoxometalates and polymers. A comb copolymer poly(ether-ether-ketone)-grafted-poly(2-ethyl-2-oxazoline) (PGE) with transformable side chains was synthesized and complexed with H3PW12O40 (PW) by electrostatic self-assembly, forming PGE/PW nanocomposite membranes with bicontinuous nanostructures. After a subsequent PA-treatment of these membranes, high-temperature PEMs of PGE/PW/PA ternary nanocomposites were obtained, in which the in situ electrostatic crosslinking effect between PW and PGE side chains was generated in the hydrophilic domains of the bicontinuous structures. The microphase separation structure and the electrostatic crosslinking feature endow the PGE/PW/PA membranes with excellent anhydrous proton conductive ability while retaining high mechanical performance. The membranes show a high proton conductivity of 42.5 mS/cm at 150 ℃ and a high tensile strength of 13 MPa. Our strategy can pave a new route based on electrostatic control to design nanostructured polymer electrolytes.
Triplet-triplet annihilation (TTA) upconversion-based materials have potential application in the broad range of research areas, including photocatalysis and life sciences. However, near-infrared (NIR)-to-blue upconverted emission is preferred for most of the practical applications, but developing a NIR-to-blue TTA upconversion system is a challenging task in photochemistry. In this work, a thermally activated delayed fluorescence (TADF) material with intense visible-to-NIR absorption is demonstrated that shows a longer triplet state lifetime (32 µs) and high triplet state energy (ET = 1.55 eV). For the first time, a heavy atom-free NIR (λex > 650 nm) to blue (λem < 460 nm) TTA upconversion system was devised, employing the dimeric borondifluoride curcuminoid TADF material as triplet photosensitizer (PS) and a large anti-Stokes shift (0.88 eV) along with moderate upconversion yield was achieved. Our work provides the solution and guidance for the future development of purely organic heavy atom-free NIR activating TTA upconversion system for a wide array of applications.
Exosome, which is a kind of extracellular vesicles with size around 40-160 nm, plays an important role in cell-to-cell communication in multiple diseases. Especially in tumor microenvironment, exosomes are the important pathway to transit proteins, nucleic acids and small molecules between different kinds of cells. Based on these characteristics, exosomes are served as both therapeutic agents and drug delivery systems in cancer therapy. In this review, the applications of exosomes as drug delivery systems in cancer therapy were summarized and classified according to the cell source of the exosomes, including normal cells, immune cells and tumor cells. Different modifications of exosomes and drug loading methods were presented. Finally, some challenges that hindered the clinical translation of exosomes were also discussed.
The emission changes of fluorescent dyes under the influence of environmental changes or interaction with analytes are the basis for designing ratiometric fluorescent probes and logic gates. However, it is rare that only one external stimulus induces continuous fluorescent color changes in a fluorescent dye. In this paper, we report a cage-like molecule formed by two benzene rings and three imidazolium salts which produces continuous fluorescence wavelength changes when interacted with fluoride ions. Fluoride ions are first bound to the center of the cage under the action of anion-π interaction, and the (C−H)+···F– type ionic hydrogen bonds induce the blue-shift of fluorescence. The subsequent formation of C-F covalent bonds with fluoride ions makes the fluorophore wavelength continue to blue-shift, and finally obtains continuous multiple fluorescence changes caused by a single external stimulus. According to the fluorescence wavelength and intensity, six different fluorescence signal channels can be obtained, which can be encoded as six numbers from 0 to 5. We expect that this reaction process can find applications in quantitative anion recognition and molecular counters.
Hawanoids A‒E (1‒5), five highly cyclized diterpenoids were isolated from the deep-sea-derived fungus Paraconiothyrium hawaiiense FS482. Compounds 1 and 2 possessed an unprecedented tetracyclo[6.6.2.02,7.011,15]cetane carbon skeleton while 3 and 4 possessed an unusual 11, 14-macrocyclic ether moiety in phomactin family. Their structures including the stereo-chemistry were determined through spectroscopic analysis, X-ray diffractions and computational calculations. The plausible biosynthetic pathway was proposed based on the predicted biosynthetic gene cluster. All of the isolated compounds exhibited inhibitory activities against PAF-induced platelet aggregation. The molecular docking study was carried out understand the interaction between the PAF receptor and hawanoids with different skeletons.
Perpyrrospirone A (1) characterized an unprecedented 6/5/6/8/5/13/6 oxahexacyclic scaffold with a unique peroxide-bridged 8, 9-dioxa-2-azaspiro[4.7]dodecane core from marine-derived Penicillium citrinum. Compounds 2 and 3 possessed rare oxatetracyclic (6/5/6/5) skeleton fused with a 13-menbered-ring macrocyclic moiety. Their structure and absolute configurations were determined by comprehensive spectroscopic analyses, ECD data coupled with TD-DFT calculations and X-ray diffraction experiments. In addition, 7 showed cytotoxicity and induced apoptosis of Hela cells in a dose-dependent manner after a 48 h treatment.
Designing a multifunctional scaffold with osteogenic and angiogenic properties holds promise for ideal bone regeneration. Innovative scaffold was here constructed by immobilizing exosomes derived from human bone mesenchymal stem cells (hBMSCs) onto porous polymer meshes which developed by PLGA and Cu-based MOF (PLGA/CuBDC@Exo). The synthesized exosome-laden scaffold capable of providing a dual cooperative controllable release of bioactive copper ions and exosomes that promote osteogenesis and angiogenesis, thereby achieving cell-free bone regeneration. In vitro assay revealed the composite stent not only substantially upregulated the expression of osteogenic-related proteins (ALP, Runx2, Ocn) and VEGF in hBMSCs, but promoted the migration and tube formation of the human umbilical vein endothelial cells (HUVECs). In vivo evaluation further confirmed this scaffold dramatically stimulated bone regeneration and angiogenesis in critical-sized defects in rats. Altogether, this composite scaffold carrying therapeutic exosomes had an osteogenic-angiogenic coupling effect and offered a new idea for cell-free bone tissue engineering.
Coordination-driven self-assembly was used to construct two metallacycles of a dicarboxylate-functionalized dibenzo-18-crown-6 in combination with either a 0° anthracene-based clip-type acceptor or a 60° phenanthrene-based acceptor. The angularities of these moieties make them suitable for the formation of a [2 + 2] rectangle and a [3 + 3] triangle, respectively. The synthesis, characterization and host-guest chemistry of two metallacycles were described and supported by 31P{1H}, 1H NMR spectra and electrospray mass spectrometry.
Terminal deoxynucleotidyl transferase (TdT) has been characterized as template-independent polymerase using single-stranded DNA (ssDNA) as primers to generate random oligonucleotides. However, the extension performance of TdT to single-stranded RNA (ssRNA) is vague. By systematically comparing and contrasting the performance of TdT-catalyzed ssDNA and ssRNA extension, it is indicated that the catalytic efficiency of ssRNA as primers was about 3 times lower than ssDNA as primers. Collectively, it is believed that understanding the catalytic performance of TdT will help to design the strategy to synthesize chimeric DNA on 3′-OH of ssRNA, which becomes invaluable.
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