Molecular Engineering Towards Efficient Aggregation-Induced Delayed Fluorescence Luminogens as Emitters and Sensitizers for High-Performance Organic Light-Emitting Diodes.

Exploring efficient thermally-activated delayed fluorescence materials having maximum external quantum efficiencies (ηext,maxs) exceeding 30% for organic light-emitting diodes (OLEDs) still remains challenging because it generally requires efficient reverse intersystem crossing (RISC), high photoluminescence quantum yield (ΦPL), and large optical out-coupling efficiency (Φout) simultaneously. Herein, two green aggregation-induced delayed fluorescence (AIDF) luminogens, named XTCz-2 and XTCz-3, are designed and constructed by using xanthone (XT) as electron acceptor and phenylcarbazole-substituted carbazole as donors. XTCz-2 and XTCz-3 exhibit distinguished advantages of high thermal stability (439‒560 oC), excellent ΦPLs (84‒88%) and fast RISC rates (1.9 × 105‒4.2 × 105 s-1), and prefer horizontal dipole orientation and thus have high Φouts. Consequently, they can achieve the state-of-the-art electroluminescence (EL) performances with ηext,maxs of up to 35.0%. Moreover, XTCz-3 is selected as a sensitizer for sky-blue multi-resonance delayed fluorescence emitter in hyperfluorescence OLEDs, providing narrow EL spectra and excellent ηext,maxs of up to 33.8% with low efficiency roll-offs. The splendid comprehensive performances demonstrate the significant application potential of these AIDF luminogens as both light-emitting materials and sensitizers for OLEDs.

Synthesis, photoluminescence and electroluminescence properties of a new blue emitter with aggregation-induced emission and thermally activated delayed fluorescence characteristics.

The emitters with aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) characteristics are in high demand in organic light-emitting diodes (OLEDs) owing to their strong fluorescence and high exciton utilization under electrical excitation. Herein, a blue emitter, 10-(3-((3,5-di(9H-carbazol-9-yl)phenyl)sulfonyl)phenyl)-9,9-dimethyl-9,10-dihydroacridine (m-CZ-DPS-DMAC), was synthesized by incorporating carbazole as skeleton, acridine as electron donor, and diphenyl sulfone as electron acceptor. m-CZ-DPS-DMAC emits weak fluorescence in good solvent, while it is obviously enhanced in the aggregate state, which is typical of AIE molecules. Meanwhile, the energy levels of the singlet and triplet states (ΔEST) of the molecule is relatively small, and it also exhibits obvious temperature dependence and oxygen sensitivity, which directly proves its TADF properties. In view of the above properties, a series of non-doped and doped OLEDs were prepared using m-CZ-DPS-DMAC as light-emitting layers. Among them, non-doped OLED (device A) displays blue emission (488 nm) with the turn-on voltage (Von), the maximum luminance (Lmax), the maximum current efficiency (CEmax), the maximum power efficiency (PEmax) and the maximum external quantum efficiency (EQEmax) of 2.6 V, 3460 cd m-2, 26.09 cd A-1, 29.26 lm W-1 and 10.05%, respectively. Doped OLED (device C) constructed based on m-CZ-DPS-DMAC doped 30% in DPEPO shows the satisfactory performance with the maximum emission peak of 486 nm, the Von of 2.8 V, the Lmax of 4571 cd m-2, the CEmax of 21.37 cd A-1, the PEmax of 22.37 lm W-1, and the EQEmax of 9.44%, respectively. The outstanding performance of m-CZ-DPS-DMAC proves that it is a potential material for designing blue OLEDs with AIE-TADF properties.

Orthogonal Hydroxyl Functionalization of cGAMP Confers Metabolic Stability and Enables Antibody Conjugation.

cGAMP is a signaling molecule produced by the cGAS-DNA complex to establish antimicrobial and antitumor immunity through STING. Whereas STING activation holds potential as a new strategy to treat cancer, cGAMP is generally considered unsuitable for in vivo use because of the rapid cleavage of its phosphodiester linkages and the limited cellular uptake under physiological conditions. Consequently, phosphorothioation and fluorination are commonly used to improve the metabolic stability and permeability of cGAMP and its synthetic analogues. We now show that methylation of the 3'-hydroxyl group of cGAMP also confers metabolic stability and that acylation of the 2'-hydroxyl group can be achieved directly and selectively to enable receptor-mediated intracellular delivery. Unlike phosphorothioation and fluorination, these modifications do not create a new stereogenic center and do not require laborious building block synthesis. As such, orthogonal hydroxyl functionalization is a simple solution to issues associated with the in vivo use of cGAMP.

Tumor-targeted delivery of a STING agonist improvescancer immunotherapy.

The cGAS-STING pathway is essential for immune defense against microbial pathogens and malignant cells; as such, STING is an attractive target for cancer immunotherapy. However, systemic administration of STING agonists poses safety issues while intratumoral injection is limited by tumor accessibility. Here, we generated antibody-drug conjugates (ADCs) by conjugating a STING agonist through a cleavable linker to antibodies targeting tumor cells. Systemic administration of these ADCs was well tolerated and exhibited potent antitumor efficacy in syngeneic mouse tumor models. The STING ADC further synergized with an anti-PD-L1 antibody to achieve superior antitumor efficacy. The STING ADC promoted multiple aspects of innate and adaptive antitumor immune responses, including activation of dendritic cells, T cells, natural killer cells and natural killer T cells, as well as promotion of M2 to M1 polarization of tumor-associated macrophages. These results provided the proof of concept for clinical development of the STING ADCs.

One-Pot Preparation of HTPB/nNi and Its Catalyst for AP.

The liquid phase reduction method is a common method used for preparing nano-nickel powder (nNi). However, the nNi surface is easily oxidized to form nickel oxide film, which affects its performance. In this work, nNi was prepared using anhydrous ethanol as a solvent and hydrazine hydrate as a reducing agent. Furthermore, HTPB/nNi composites were prepared using hydroxyl-terminated polybutadiene (HTPB) as a coating agent. The structure and morphology of the samples are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The catalytic behavior of HTPB/nNi on the thermal decomposition of ammonium perchlorate (AP) is studied by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG). The results show that HTPB/nNi has little effect on the low temperature thermal decomposition of AP, but the peak of high temperature thermal decomposition advances from 456 °C to 332 °C.

Ionic liquid-induced in situ deposition of perovskite quantum dot films with a photoluminescence quantum yield of over 85.

Metal halide perovskite quantum dots (QDs) hold great promise as building blocks for next-generation light emitting devices (LEDs). The preparation of perovskite QD films with high photoluminescence quantum yield (PLQY) is the key to realizing efficient LEDs. However, the conventional deposition method of spin-coating of pre-synthesized QD ink solutions results in perovskite QD films with low PLQY (typically <45%) due to non-radiative recombination centers induced in the deposition process. Here, by utilizing the ionic nature and steric hindrance effect of the ionic liquid, we demonstrate an in situ deposition method for perovskite QD films with high PLQY by directly spin-coating precursor solutions containing an ionic liquid. Furthermore, mechanistic study reveals that the ionic liquid not only induces the formation of QDs but also suppresses defect-related recombination through the interaction with uncoordinated metal atoms on the surface of the QDs. As a result, the in situ deposited CsPbBr3 QD film with a PLQY as high as 85.2% and long-term air stability is achieved. These findings demonstrate that the introduction of an ionic liquid provides an effective strategy to enhance the performance of in situ formed perovskite QD films, which could benefit the development of efficient LEDs and other optoelectronic devices.

Vital Sign Detection during Large-Scale and Fast Body Movements Based on an Adaptive Noise Cancellation Algorithm Using a Single Doppler Radar Sensor.

The non-contact detection of human vital signs (i.e., respiration rate (RR) and heartbeat rate (HR)) using a continuous-wave (CW) Doppler radar sensor has great potential for intensive care monitoring, home healthcare, etc. However, large-scale and fast random body movement (RBM) has been a bottleneck for vital sign detection using a single CW Doppler radar. To break this dilemma, this study proposed a scheme combining adaptive noise cancellation (ANC) with polynomial fitting, which could retrieve the weak components of both respiration and heartbeat signals that were submerged under serious RBM interference. In addition, the new-type discrete cosine transform (N-DCT) was introduced to improve the detection accuracy. This scheme was first verified using a numerical simulation. Then, experiments utilizing a 10-GHz Doppler radar sensor that was built from general-purpose radio frequency (RF) and communication instruments were also carried out. No extra RF/microwave components and modules were needed, and neither was a printed circuit board nor an integrated-chip design required. The experimental results showed that both the RR and HR could still be extracted during large-scale and fast body movements using only a single Doppler radar sensor because the RBM noises could be greatly eliminated by utilizing the proposed ANC algorithm.

Design and Development of Highly Efficient Light-Emitting Layers in OLEDs with Dimesitylboranes: An Updated Review.

With excellent luminescent properties and transport properties, triarylborane compounds containing two mesitylenes (Mes) have gained much attention for their application in OLEDs as light-emitting layers. This study serves as an updated review summarizing recent developments in the design of fluorescent chromophores and phosphorescent host materials for OLEDs comprising small molecular compounds of dimesitylborane (BMes2 ) as luminescent layers, with attention to the performance of different light-emitting devices. Problems that need to be solved in the research and application of BMes2 in OLEDs are presented and the application prospects of such materials are suggested.

Installation of a cancer promoting WNT/SIX1 signaling axis by the oncofusion protein MLL-AF9.

BACKGROUND: Chromosomal translocation-induced expression of the chromatin modifying oncofusion protein MLL-AF9 promotes acute myelocytic leukemia (AML). Whereas WNT/ß-catenin signaling has previously been shown to support MLL-AF9-driven leukemogenesis, the mechanism underlying this relationship remains unclear. METHODS: We used two novel small molecules targeting WNT signaling as well as a genetically modified mouse model that allow targeted deletion of the WNT protein chaperone Wntless (WLS) to evaluate the role of WNT signaling in AML progression. ATAC-seq and transcriptome profiling were deployed to understand the cellular consequences of disrupting a WNT signaling in leukemic initiating cells (LICs). FINDINGS: We identified Six1 to be a WNT-controlled target gene in MLL-AF9-transformed leukemic initiating cells (LICs). MLL-AF9 alters the accessibility of Six1 DNA to the transcriptional effector TCF7L2, a transducer of WNT/ß-catenin gene expression changes. Disruption of WNT/SIX1 signaling using inhibitors of the Wnt signaling delays the development of AML. INTERPRETATION: By rendering TCF/LEF-binding elements controlling Six1 accessible to TCF7L2, MLL-AF9 promotes WNT/ß-catenin-dependent growth of LICs. Small molecules disrupting WNT/ß-catenin signaling block Six1 expression thereby disrupting leukemia driven by MLL fusion proteins.

[Factors influencing induction and in vitro culture of hairy roots in Phytolacca americana L.]

To use hairy roots for producing medicinal ingredients of Phytolacca americana L. we studied the factors influencing the induction and in vitro culture. Hairy roots could be incited from the veins of cut surface (morphological lower) of P. americana L. leaf explants around 18 days after infection with the strain of Agrobacterium rhizogenes ATCC15834. The highest rooting rate, 70%, was obtained when leaf explants were pre-cultured for 1 day, infected for 20 min, and co-cultured for 4 days. The transformation was confirmed by PCR amplification of rolC of Ri plasmid and silica gel thin-layer chromatography of opines from P. americana L. hairy roots. All the hairy root lines could grow rapidly on solid exogenous phytohormone-free MS medium. Among the 9 hairy root lines, the hairy root line 2 had most rapid growth, most branched lateral roots and most intensive root hair; the root surface of some hairy root lines seemed purple or red, while that of the other hairy root line appeared white. Among liquid media MS, 1/2MS, B5 and 6,7-V tested, the best growth for hairy root lines was attained in liquid exogenous phytohormone-free MS medium. Compared with exogenous phytohormone-free MS medium, 6,7-V medium was better for synthesis and accumulation of esculento side A in hairy roots. The established optimal conditions for induction and in vitro culture of P. americana hairy roots had laid an experimental and technological foundation for production of medicinal constituents esculento side A from large scale culture of hairy roots.

Two Novel Two-Stage Direction of Arrival Estimation Algorithms for Two-Dimensional Mixed Noncircular and Circular Sources.

This paper addresses the two-dimensional (2D) direction-of-arrival (DOA) estimation problem with two novel methods for mixed noncircular and circular signals. The first proposed method is named the two-stage direction-of-arrival matrix (TSDOAM) method, and the other is called the two-stage rank reduction (TSRARE) method. The proposed methods utilize both the circularity and the direction-of-arrival differences between the noncircular and circular sources to estimate the 2D directions-of-arrival (DOAs). The maximum detectable 2D angle parameters of the TSDOAM and TSRARE methods are twice those of the existing methods. Moreover, the TSRARE method can detect more incident signals than the TSDOAM method due to the array aperture of two parallel uniform linear arrays (ULAs) being fully utilized. Simulation results show that compared to the existing methods for the small angle separation of 2D directions-of-arrival, the two proposed methods perform well in terms of the signal-to-noise ratio (SNR) and snapshots.

cGAS is essential for the antitumor effect of immune checkpoint blockade.

cGMP-AMP (cGAMP) synthase (cGAS) is a cytosolic DNA sensor that activates innate immune responses. cGAS catalyzes the synthesis of cGAMP, which functions as a second messenger that binds and activates the adaptor protein STING to induce type I interferons (IFNs) and other immune modulatory molecules. Here we show that cGAS is indispensable for the antitumor effect of immune checkpoint blockade in mice. Wild-type, but not cGAS-deficient, mice exhibited slower growth of B16 melanomas in response to a PD-L1 antibody treatment. Consistently, intramuscular delivery of cGAMP inhibited melanoma growth and prolonged the survival of the tumor-bearing mice. The combination of cGAMP and PD-L1 antibody exerted stronger antitumor effects than did either treatment alone. cGAMP treatment activated dendritic cells and enhanced cross-presentation of tumor-associated antigens to CD8 T cells. These results indicate that activation of the cGAS pathway is important for intrinsic antitumor immunity and that cGAMP may be used directly for cancer immunotherapy.

Aromatic primary monoamine-based fast-response and highly specific fluorescent probes for imaging the biological signaling molecule nitric oxide in living cells and organisms.

Nitric oxide (NO) is an important cellular signaling molecule involved in many physiological and pathological processes. To probe its spatiotemporal information in biosystems, a large number of NO fluorescent probes have been exploited in the past ten years. Among them, the o-phenylenediamine-based probes are the earliest developed and most versatile NO fluorescent probes to date. However, there are still limitations such as relatively long response time, possible interference by dehydroascorbic acid (DHA)/methylglyoxal (MGO), and pH-sensitivity of their fluorescence signals. In this work, we present two aromatic primary monoamine-based NO fluorescent probes, MA and NIR-MA, and explore the reductive deamination reaction of the electron-rich p-methoxyaniline group with NO under aerobic conditions. The superiority of both probes is illustrated by their quick, stable, sensitive, and specific fluorescence off-on responses for NO over a series of biologically relevant interfering species, including reactive oxygen species, DHA/MGO, biothiols, and metal ions. Coupled with good cell permeability and low cytotoxicity, the two probes have successfully been applied to imaging the endogenous NO in RAW 264.7 macrophages stimulated by LPS/IFN-γ. Moreover, the fluorescence response of NIR-MA for NO occurs in the physiologically favorable NIR region, enabling its further use to image endogenous NO in an inflamed mouse model.

A new class of fast-response and highly selective fluorescent probes for visualizing peroxynitrite in live cells, subcellular organelles, and kidney tissue of diabetic rats.

Peroxynitrite (ONOO(-)) is an extremely powerful oxidant in biological systems, and can react with a wide variety of molecular targets including proteins, lipids, and nucleic acids, eventually resulting in a series of disease states such as diabetes, Alzheimer's disease, cancer, arthritis, autoimmune, and other disorders. In this work, we present a new class of ONOO(-) fluorescent probes by exploiting the ONOO(-)-triggered N-oxidation and N-nitrosation reactions of aromatic tertiary amine for the first time. The as-obtained fluorescent probe A2 could detect ONOO(-) with quite fast fluorescence off-on response (within seconds), ultrasensitivity (detection limit: <2 nM), and excellent selectivity over a series of biologically relevant reactive oxygen species as well as metal cations. With the probe, the endogenous ONOO(-) in activated RAW264.7 murine macrophage, EA.hy926 endothelial cells after oxygen glucose deprivation and reoxygenation (OGD/RO), and kidney tissue of diabetic rats has been successfully visualized. Based on the molecular platform of A2, we further develop its mitochondria- and lysosome-targetable fluorescent probes Mito-A2 and Lyso-A2 by installing the corresponding targeting groups to alkoxy unit of A2, and confirm their abilities to image ONOO(-) in mitochondria and lysosomes, respectively, by co-localization assays. It is greatly expected that these probes can serve as useful imaging tools for clarifying the distribution and pathophysiological functions of ONOO(-) in cells, subcellular organelles, and animal tissues.

Sulfone-Rhodamines: A New Class of Near-Infrared Fluorescent Dyes for Bioimaging.

Given the wavelength dependence of tissue transparency and the requirement for sufficiently low background autofluorescence, the development of fluorescent dyes with excitation and emission maxima beyond 700 nm is highly desired, but it is a challenging task. Herein, a new class of fluorescent dyes, named sulfone-rhodamines (SO2Rs), was developed on the basis of the one-atom replacement of the rhodamine 10-position O atom by a sulfone group. Such a modification makes their absorption and emission maxima surprisingly reach up to 700-710 and 728-752 nm, respectively, much longer than their O-, C-, and Si-rhodamine analogs, due to the unusual d*-π* conjugation. Among these dyes, SO2R4 and SO2R5, bearing disubstituted meso-phenyl groups, show the greatest potentials for bioimaging applications in view of their wide pH range of application, high photostability, and big extinction coefficients and fluorescence quantum yields. They could quickly penetrate cells to give stable NIR fluorescence, even after continuous irradiation by a semiconductor laser, making them suitable candidates for time-lapse and long-term bioimaging applications. Moreover, they could specifically localize in lysosomes independent of alkylmorpholine targeted group, thus avoiding the problematic alkalization effect suffered by most LysoTrackers. Further imaging assays of frozen slices of rat kidney reveal that their tissue imaging depth is suprior to the widely used NIR labeling agent Cy5.5.

Coordination reactions of 2-pyridinecarboxaldehyde-phenylhydrazonatolithium with selected transition metal (Zn, Sn, Fe, Co, Ni and Zr) chlorides and its coupling reaction with dichloromethane.

The reactions of 2-pyridinecarboxaldehyde-phenylhydrazonatolithium C5H4Npy-CH[double bond, length as m-dash]Ni-NaLi(Ph) (abbreviated as Li) with a 1/2 equivalent of anhydrous metal (Zn, Sn, Fe and Co) chlorides or NiCl2(DME) (DME = 1, 2-dimethoxyethane) produced the corresponding mononuclear metal(ii) complexes ( and ), in which each ligand acts as a bidentate ligand and the coordination geometries around the metals are shown to be tetrahedral within the complexes , , and , respectively, and a tetragonal pyramid in the complex . The reaction of Li successively with sodium tert-butoxide and anhydrous ZrCl4 afforded the unanticipated bizirconium complex , in which each monoanionic ligand behaves as a tridentate bridge. Whereas treatment of Li with NiCl2 and then CH2Cl2 led to an interesting methylene-bridged bis(2-pyridyl-phenylhydrazone) compound in moderate yield; a comparative experiment showed that when the Li reacted with CH2Cl2, the coupling compound was also obtained but in very low yield. A plausible mechanism of compound formation was also proposed and supported by the density functional theory (DFT) calculations. All the synthesized compounds were characterized by single-crystal X-ray diffraction.

Fast-response and highly selective fluorescent probes for biological signaling molecule NO based on N-nitrosation of electron-rich aromatic secondary amines.

Nitric oxide (NO) is a ubiquitous biological messenger molecule, and plays the active roles in the regulation of various physiological processes. Although numerous NO fluorescent probes have also been successfully developed in the past ten years, it still remains challenging to increase the response rate for NO while having the high selectivity and sensitivity. In this work, a simple N-nitrosation reaction of the electron-rich aromatic secondary amine with NO under aerobic condition has been utilized for the first time to construct fluorescent probe for NO. The resulting probe 1, containing a N-benzyl-4-hydroxyaniline moiety as reaction group and a BODIPY dye as fluorescence reporter, could detect NO with the fast fluorescence off-on response (within seconds), high sensitivity (nM level), and excellent selectivity over various reactive oxygen species (ROS) as well as dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Even in the presence of glutathione (GSH, a high reactive biothiol for NO), the probe still works well for NO. Further, a mitochondria-targetable probe 2 was exploited by introducing a targeted triphenylphosphonium cation into probe 1 scaffold. It's excellent NO sensing performance as well as its ability to specifically target mitochondria and image NO there have been nicely demonstrated. With the two probes, the basal and stimulation-induced NO in RAW264.7 murine macrophages as well as the endogenous NO in endothelial cells after oxygen-glucose deprivation (OGD) have been successfully visualized.

A Luminescent Nitrogen-Containing Polycyclic Aromatic Hydrocarbon Synthesized by Photocyclodehydrogenation with Unprecedented Regioselectivity.

We present a nitrogen-containing polycyclic aromatic hydrocarbon (N-PAH), namely 12-methoxy-9-(4-methoxyphenyl)-5,8-diphenyl-4-(pyridin-4-yl)pyreno[1,10,9-h,i,j]isoquinoline (c-TPE-ON), which exhibits high quantum-yield emission both in solution (blue) and in the solid state (yellow). This molecule was unexpectedly obtained by a three-fold, highly regioselective photocyclodehydrogenation of a tetraphenylethylene-derived AIEgen. Based on manifold approaches involving UV/Vis, photoluminescence, and NMR spectroscopy as well as HRMS, we propose a reasonable mechanism for the formation of the disk-like N-PAH that is supported by density functional theory calculations. In contrast to most PAHs that are commonly used, our system does not suffer from entire fluorescence quenching in the solid state due to the peripheral aromatic rings preventing π-π stacking interactions, as evidenced by single-crystal X-ray analysis. Moreover, its rod-like microcrystals exhibit excellent optical waveguide properties. Hence, c-TPE-ON comprises a N-PAH with unprecedented luminescent properties and as such is a promising candidate for fabricating organic optoelectronic devices. Our design and synthetic strategy might lead to a more general approach to the preparation of solution- and solid-state luminescent PAHs.

Molecular basis for the specific recognition of the metazoan cyclic GMP-AMP by the innate immune adaptor protein STING.

Cyclic GMP-AMP containing a unique combination of mixed phosphodiester linkages (2'3'-cGAMP) is an endogenous second messenger molecule that activates the type-I IFN pathway upon binding to the homodimer of the adaptor protein STING on the surface of endoplasmic reticulum membrane. However, the preferential binding of the asymmetric ligand 2'3'-cGAMP to the symmetric dimer of STING represents a physicochemical enigma. Here we show that 2'3'-cGAMP, but not its linkage isomers, adopts an organized free-ligand conformation that resembles the STING-bound conformation and pays low entropy and enthalpy costs in converting into the active conformation. Our results demonstrate that analyses of free-ligand conformations can be as important as analyses of protein conformations in understanding protein-ligand interactions.

Construction of the 5,6,7-tricyclic skeleton of lancifodilactone F.

We report herein the synthesis of a fully functionalized B,C,D-ring system of lancifodilactone F. The key transformations involve an arene-olefin meta-photocycloaddition reaction and a palladium-catalyzed oxidative C-C cleavage reaction to establish its B,C-rings.