Latest ArticlesTriplet-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.
Vercytochalasins A (1) and B (2), two biosynthetically related cytochalasins featuring novel structure and substituents, were isolated from the endozoic fungus Curvularia verruculosa which was associated with the deep-sea squat lobster Shinkaia crosnieri collected from the cold seep environment in South China sea. Their structures were elucidated by detailed interpretation of NMR spectroscopic and mass spectrometric data. The absolute configurations were confirmed by NOESY experiments as well as by DP4+ and ECD calculations. Differed from common cytochalasins, compound 1 is an uncommon secocytochalasin featuring the ester group cleaved between C-9 and C-23, and incorporating an additional oxygenated C4 unit which coupled with C-20 and C-22 to form a new substituted cyclohexenone moiety, while compound 2 contains an unusual 2‑hydroxy-3-oxobutan-2-yl unit at C-22. Both compounds are distinctive from the commonly described cytochalasins. Compound 1 exhibited potent activity against angiotensin-Ⅰ-converting enzyme (ACE) whereas compound 2 showed antibacterial activity. Molecular docking simulations were performed to explore the intermolecular interaction of compounds 1 and 2 with ACE.
G-quadruplex (G4) is widely known as a non-classical secondary structure of nucleic acid. With the in-depth study of G4, it is an urgent need for a phosphorescent probe with a high G4 binding ability to evaluate the level of G4 in the cytoplasm. Thus, this study designed and synthesized Ir-PDP where an Ir(Ⅲ) complex was used as a phosphorescent emitter. Meanwhile, two installed PDPs (pyridostatin derivatives) were used to improve the combination ability with G4 and reduced the cytotoxicity of the Ir(Ⅲ) complex. Compared with other nucleic acid secondary structures, Ir-PDP produced a higher phosphorescence lifetime after interacting with G4. Ir-PDP was distributed in the cytoplasm of living cells, and two-photon phosphorescence lifetime imaging can detect the binding events of the probe in the cytoplasm. The addition of G4 binder PDS significantly regulated cytoplasmic phosphorescence lifetime. The project explored a new sensing pathway to observe the binding manners of probes in the cytoplasm through the phosphorescence lifetime of probes.
Decades have passed since the first nanoparticles-base medicine was approved for human cancer treatment, and the research and development of nanoparticles for drug delivery are always undergoing. Nowadays, the significant advances complicate nanoparticles' branches, including liposomes, solid lipid nanoparticles, inorganic nanoparticles, micelles, nanovaccines and nano-antibodies, etc. These nanoparticles show numerous capabilities in treatment and diagnosis of stubborn diseases like cancer and neurodegenerative diseases, emerging as novel drug carriers or therapeutic agents in future. In this review, the complicated branches of nanoparticles are classified and summarized, with their property and functions concluded. Besides, there are also some delivery strategies that make nanoparticles smarter and more efficient in drug delivery, and frontiers in these strategies are also summarized in this review. Except these excellent works in newly-produced drug delivery nanoparticles, some points of view and future expectations are made in the end.
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.
We report the synthesis and characterization of a fan-shaped chiral nanographene 1, which is composed of 6 hexabenzocoronene subunits with 216 conjugated carbon atoms. In the dehydrocyclization reaction, 38 CC bonds are formed simultaneously. 1 exhibits strong panchromatic absorption from the ultraviolet to the near-infrared, with an absorption coefficient of 209,000 L mol−1 cm−1 at 564 nm. Optically pure samples, obtained via chiral HPLC, show distinct ECD signals (|Δε| = 704 L mol−1 cm−1 at 405 nm). Upon excitation, 1 emits near-infrared fluorescence at 820 nm with a quantum yield of 5.5%. These photophysical properties of 1 were analyzed with the assistance of DFT calculations.
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.
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.
Heat shock protein 90 (Hsp90) is an appealing anticancer drug target that provoked a tremendous wave of investigations. Geldanamycin (GA) is the first identified Hsp90 inhibitor that exhibited potent anti-cancer activity, but the off-target toxicity associated with the benzoquinone moiety hampered its clinical application. Until now, structure optimization of GA is still in need to fully exploit the therapeutic value of Hsp90. Due to the structural complexity and synthetic challenge of this compound family, conventional optimization is bound to be costly but high efficiency is expected to be reachable by combining the art of rational design and total synthesis. Described in this paper is our first attempt at this approach aiming at rational modification of the C6-position of GA. The binding affinities towards Hsp90 of compound 1 (C6-ethyl) and 2 (C6-methyl) were designed and predicted by using Discovery Studio. These compounds were synthesized and further subjected to a thorough in vitro biological evaluation. We found that compounds 1 and 2 bind to Hsp90 protein with the IC50 of 34.26 nmol/L and 163.7 nmol/L, respectively. Both compounds showed broad-spectrum antitumor effects. Replacing by ethyl, compound 1 exhibited more potent bioactivity than positive control GA, such as in G2/M cell cycle arrest, cell apoptosis and client proteins degradations. The results firstly indicated that the docking study is able to provide a precise prediction of Hsp90 affinities of GA analogues, and the C6 substituent of GA is not erasable without affecting its biological activity.
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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