IL-2 regulates tumor-reactive CD8+ T cell exhaustion by activating the aryl hydrocarbon receptor.

CD8+ T cell exhaustion dampens antitumor immunity. Although several transcription factors have been identified that regulate T cell exhaustion, the molecular mechanisms by which CD8+ T cells are triggered to enter an exhausted state remain unclear. Here, we show that interleukin-2 (IL-2) acts as an environmental cue to induce CD8+ T cell exhaustion within tumor microenvironments. We find that a continuously high level of IL-2 leads to the persistent activation of STAT5 in CD8+ T cells, which in turn induces strong expression of tryptophan hydroxylase 1, thus catalyzing the conversion to tryptophan to 5-hydroxytryptophan (5-HTP). 5-HTP subsequently activates AhR nuclear translocation, causing a coordinated upregulation of inhibitory receptors and downregulation of cytokine and effector-molecule production, thereby rendering T cells dysfunctional in the tumor microenvironment. This molecular pathway is not only present in mouse tumor models but is also observed in people with cancer, identifying IL-2 as a novel inducer of T cell exhaustion.

Breaking Rotational Symmetry in Supertwisted WS2 Spirals via Moiré Magnification of Intrinsic Heterostrain.

Twisted stacking of van der Waals materials with moiré superlattices offers a new way to tailor their physical properties via engineering of the crystal symmetry. Unlike well-studied twisted bilayers, little is known about the overall symmetry and symmetry-driven physical properties of continuously supertwisted multilayer structures. Here, using polarization-resolved second harmonic generation (SHG) microscopy, we report threefold (C3) rotational symmetry breaking in supertwisted WS2 spirals grown on non-Euclidean surfaces, contrasting the intact symmetry of individual monolayers. This symmetry breaking is attributed to a geometrical magnifying effect in which small relative strain between adjacent twisted layers (heterostrain), verified by Raman spectroscopy and multiphysics simulations, generates significant distortion in the moiré pattern. Density-functional theory calculations can explain the C3 symmetry breaking and unusual SHG response by the interlayer wave function coupling. These findings thus pave the way for further developments in the so-called "3D twistronics".

Tunnel versus medial approach in laparoscopic radical right hemicolectomy for right colon cancer: a retrospective cohort study.

PURPOSE: This study aimed to explore the feasibility and safety of the tunnel approach in laparoscopic radical right hemicolectomy for colon cancer. METHODS: From July 2016 to October 2018, a total of 106 consecutive patients with colon cancer who underwent laparoscopic radical right hemicolectomy at the Affiliated Cancer Hospital of Zhengzhou University were enrolled. The patients were stratified into either a tunnel approach (TA) (n = 56) group or traditional medial approach (MA) (n = 50) group according to the surgical technique performed. The baseline demographics, perioperative outcomes and oncologic outcomes were compared between the two groups. RESULTS: The baseline characteristics did not differ between groups. The TA group had significantly less blood loss [20.0 (10.0-40.0) vs. 100 (100.0-150.0) ml, p < 0.001] and a shorter operation time [128.4 ± 16.7 vs. 145.6 ± 20.3 min, p < 0.001] than the MA group. The time to first flatus and postoperative hospital stay were similar [3.0 (2.0-4.0) vs. 3.0 (3-4.0) days, p = 0.329; 10.4 ± 2.6 vs. 10.7 ± 3.0 days, p = 0.506] between the two groups. The conversion to laparotomy and complication rates were similar between groups (0 vs. 6.0%, p = 0.203; 14.3% vs. 18.0%, p = 0.603, respectively). No treatment-related deaths occurred in either group. The TA group did not have significantly better survival outcomes than the MA group (p = 0.372). CONCLUSIONS: The TA seems to allow for more favourable results in terms of blood loss and operative time than the MA, with similar results regarding time to first flatus, hospital stay, postoperative complication rate, conversion rate and oncologic outcomes; moreover, the TA is easier for beginners to master.

Chemical Etching of Screw Dislocated Transition Metal Dichalcogenides.

Chemical etching can create novel structures inaccessible by growth and provide complementary understanding on the growth mechanisms of complex nanostructures. Screw dislocation-driven growth influences the layer stackings of transition metal dichalcogenides (MX2) resulting in complex spiral morphologies. Herein, we experimentally and theoretically study the etching of screw dislocated WS2 and WSe2 nanostructures using H2O2 etchant. The kinetic Wulff constructions and Monte Carlo simulations establish the etching principles of single MX2 layers. Atomic force microscopy characterization reveals diverse etching morphology evolution behaviors around the dislocation cores and along the exterior edges, including triangular, hexagonal, or truncated hexagonal holes and smooth or rough edges. These behaviors are influenced by the edge orientations, layer stackings, and the strain of screw dislocations. Ab initio calculation and kinetic Monte Carlo simulations support the experimental observations and provide further mechanistic insights. This knowledge can help one to understand more complex structures created by screw dislocations through etching.

Anion Exchange of Ruddlesden-Popper Lead Halide Perovskites Produces Stable Lateral Heterostructures.

Heterostructures of three-dimensional (3D) halide perovskites are unstable because of facile anion interdiffusion at halide interfaces. Two-dimensional (2D) Ruddlesden-Popper halide perovskites (RPPs) show suppressed and anisotropic ion diffusion that could enable stable RPP heterostructures, yet the direct and general growth of lateral RPP heterostructures remains challenging. Here, we show that halide miscibility in RPPs decreases with perovskite layer thickness (n), enabling the formation of sharp halide lateral heterostructures from n = 1 and 2 RP lead iodide microplates via anion exchange with hydrogen bromide vapor. In contrast, RPPs with n ≥ 3 form more diffuse lateral heterojunctions, more similar to those in 3D perovskites. The anion exchange behaviors are further modulated by the spacer and A-site cations in the RPP structures. These new insights, and kinetic studies of the exchange reactions, enable the preparation of lateral heterostructures from various n = 2 RPPs that are more stable against anion interdiffusion and degradation for potential optoelectronic device applications.

Distinct Carrier Transport Properties Across Horizontally vs Vertically Oriented Heterostructures of 2D/3D Perovskites.

Two-dimensional-on-three-dimensional (2D/3D) halide perovskite heterostructures have been extensively utilized in optoelectronic devices. However, the labile nature of halide perovskites makes it difficult to form such heterostructures with well-defined compositions, orientations, and interfaces, which inhibits understanding of the carrier transfer properties across these heterostructures. Here, we report solution growth of both horizontally and vertically aligned 2D perovskite (PEA)2PbBr4 (PEA = phenylethylammonium) microplates onto 3D CsPbBr3 single crystal thin films, with well-defined heterojunctions. Time-resolved photoluminescence (TRPL) transients of the heterostructures exhibit the monomolecular and bimolecular dynamics expected from exciton annihilation, dissociation, and recombination, as well as evidence for carrier transfer in these heterostructures. Two kinetic models based on Type-I and Type-II band alignments at the interface of horizontal 2D/3D heterostructures are applied to reveal a shift in balance between carrier transfer and recombination: Type-I band alignment better describes the behaviors of heterostructures with thin 2D perovskite microplates but Type-II band alignment better describes those with thick 2D microplates (>150 nm). TRPL of vertically aligned 2D microplates is dominated by directly excited PL and is independent of the height above the 3D film. Electrical measurements reveal current rectification behaviors in both heterostructures with vertical heterostructures showing better electrical transport. As the first systematic study on comparing models of 2D/3D perovskite heterostructures with controlled orientations and compositions, this work provides insights on the charge transfer mechanisms in these perovskite heterostructures and guidelines for designing better optoelectronic devices.

High-performance solar flow battery powered by a perovskite/silicon tandem solar cell.

The fast penetration of electrification in rural areas calls for the development of competitive decentralized approaches. A promising solution is represented by low-cost and compact integrated solar flow batteries; however, obtaining high energy conversion performance and long device lifetime simultaneously in these systems has been challenging. Here, we use high-efficiency perovskite/silicon tandem solar cells and redox flow batteries based on robust BTMAP-Vi/NMe-TEMPO redox couples to realize a high-performance and stable solar flow battery device. Numerical analysis methods enable the rational design of both components, achieving an optimal voltage match. These efforts led to a solar-to-output electricity efficiency of 20.1% for solar flow batteries, as well as improved device lifetime, solar power conversion utilization ratio and capacity utilization rate. The conceptual design strategy presented here also suggests general future optimization approaches for integrated solar energy conversion and storage systems.

Controllable Growth and Formation Mechanisms of Dislocated WS2 Spirals.

Two-dimensional (2D) layered metal dichalcogenides can form spiral nanostructures by a screw-dislocation-driven mechanism, which leads to changes in crystal symmetry and layer stackings that introduce attractive physical properties different from their bulk and few-layer nanostructures. However, controllable growth of spirals is challenging and their growth mechanisms are poorly understood. Here, we report the controllable growth of WS2 spiral nanoplates with different stackings by a vapor phase deposition route and investigate their formation mechanisms by combining atomic force microscopy with second harmonic generation imaging. Previously not observed "spiral arm" features could be explained as covered dislocation spiral steps, and the number of spiral arms correlates with the number of screw dislocations initiated at the bottom plane. The supersaturation-dependent growth can generate new screw dislocations from the existing layers, or even new layers templated by existing screw dislocations. Different number of dislocations and orientation of new layers result in distinct morphologies, different layer stackings, and more complex nanostructures, such as triangular spiral nanoplates with hexagonal spiral pattern on top. This work provides the understanding and control of dislocation-driven growth of 2D nanostructures. These spiral nanostructures offer diverse candidates for probing the physical properties of layered materials and exploring new applications in functional nanoelectronic and optoelectronic devices.

Chemically Derived Kirigami of WSe2.

Layered metal dichalcogenides have shown intriguing physical phenomena depending on their complex layer stackings and unique architectures. Here, we report novel microscale kirigami structures of multilayered WSe2 formed by a simple chemical vapor deposition and etching method. Scanning electron microscopy and atomic force microscopy reveal the unusual structure features of curved concave edges, panhandles, and sawtooth corners of these intricate multilayer architectures that result from etching. The structure-symmetry relationship and layer stackings of these WSe2 kirigami were elucidated by second-harmonic generation imaging and micro-Raman spectroscopy. We propose an etching model in which the etching behaviors of WSe2 multilayers are governed by the layer stacking of the bottom trilayer, which can successfully explain the formation process of WSe2 kirigami. This chemical etching approach could be applied to other metal dichalcogenide materials and open up new possibilities for creating novel and complex platforms for studying the rich physical properties in two-dimensional materials.

Vapor-Phase Epitaxial Growth of Aligned Nanowire Networks of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

With the intense interest in inorganic cesium lead halide perovskites and their nanostructures for optoelectronic applications, high-quality crystalline nanomaterials with controllable morphologies and growth directions are desirable. Here, we report a vapor-phase epitaxial growth of horizontal single-crystal CsPbX3 (X = Cl, Br, I) nanowires (NWs) and microwires (MWs) with controlled crystallographic orientations on the (001) plane of phlogopite and muscovite mica. Moreover, single NWs, Y-shaped branches, interconnected NW or MW networks with 6-fold symmetry, and, eventually, highly dense epitaxial network of CsPbBr3 with nearly continuous coverage were controllably obtained by varying the growth time. Detailed structural study revealed that the CsPbBr3 wires grow along the [001] directions and have the (100) facets exposed. The incommensurate heteroepitaxial lattice match between the CsPbBr3 and mica crystal structures and the growth mechanism of these horizontal wires due to asymmetric lattice mismatch were proposed. Furthermore, the photoluminescence waveguiding and good performance from the photodetector device fabricated with these CsPbBr3 networks demonstrated that these well-connected CsPbBr3 NWs could serve as straightforward platforms for fundamental studies and optoelectronic applications.

Stabilization of the Metastable Lead Iodide Perovskite Phase via Surface Functionalization.

Metastable structural polymorphs can have superior properties and applications to their thermodynamically stable phases, but the rational synthesis of metastable phases is a challenge. Here, a new strategy for stabilizing metastable phases using surface functionalization is demonstrated using the example of formamidinium lead iodide (FAPbI3) perovskite, which is metastable at room temperature (RT) but holds great promises in solar and light-emitting applications. We show that, through surface ligand functionalization during direct solution growth at RT, pure FAPbI3 in the cubic perovskite phase can be stabilized in nanostructures and thin films at RT without cation or anion alloying. Surface characterizations reveal that long-chain alkyl or aromatic ammonium (LA) cations bind to the surface of perovskite structure. Calculations show that such functionalization reduces the surface energy and plays a dominant role in stabilizing the metastable perovskite phase. Excellent photophysics and optically pumped lasing from the stabilized single-crystal FAPbI3 nanoplates with low thresholds were demonstrated. High-performance solar cells can be fabricated with such directly synthesized stabilized phase-pure FAPbI3 with a lower bandgap. Our results offer new insights on the surface chemistry of perovskite materials and provide a new strategy for stabilizing metastable perovskites and metastable polymorphs of solid materials in general.

Complex and Noncentrosymmetric Stacking of Layered Metal Dichalcogenide Materials Created by Screw Dislocations.

The interesting and tunable properties of layered metal dichalcogenides heavily depend on their phase and layer stacking. Here, we show and explain how the layer stacking and physical properties of WSe2 are influenced by screw dislocations. A one-to-one correlation of atomic force microscopy and high- and low-frequency Raman spectroscopy of many dislocated WSe2 nanoplates reveals variations in the number and shapes of dislocation spirals and different layer stackings that are determined by the number, rotation, and location of the dislocations. Plates with triangular dislocation spirals form noncentrosymmetric stacking that gives rise to strong second-harmonic generation and enhanced photoluminescence, plates with hexagonal dislocation spirals form the bulk 2H layer stacking commonly observed, and plates containing mixed dislocation shapes have intermediate noncentrosymmetric stackings with mixed properties. Multiple dislocation cores and other complexities can lead to more complex stackings and properties. These previously unobserved properties and layer stackings in WSe2 will be interesting for spintronics and valleytronics.

Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO3).

High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcoming the limitation of island-forming Volmer-Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (104 cm s-1), and low defect density of 1012 cm-3, which are comparable to those of CsPbBr3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. The high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.

A systematic analysis of the resistance and sensitivity of HER2YVMA receptor tyrosine kinase mutant to tyrosine kinase inhibitors in HER2-positive lung cancer.

Human epidermal growth factor receptor 2 (HER2) has become a well-established target for the treatment of HER2-positive lung cancer. However, a frequently observed in-frame mutation that inserts amino acid quadruplex Tyr776-Val777-Met778-Ala779 at G776 (G776(YVMA)) in HER2 kinase domain can cause drug resistance and sensitivity, largely limiting the application of reversible tyrosine kinase inhibitors in lung cancer therapy. A systematic investigation of the intermolecular interactions between the HER2(YVMA) mutant and clinical small-molecule inhibitors would help to establish a complete picture of drug response to HER2 G776(YVMA) insertion in lung cancer, and to design new tyrosine kinase inhibitors with high potency and selectivity to target the lung cancer-related HER2(YVMA) mutant. Here, we combined homology modeling, ligand grafting, structure minimization, molecular simulation and binding affinity analysis to profile a number of tyrosine kinase inhibitors against the G776(YVMA) insertion in HER2. It is found that the insertion is far away from HER2 active pocket and thus cannot contact inhibitor ligand directly. However, the insertion is expected to induce marked allosteric effect on some regions around the pocket, including A-loop and hinges connecting between the N- and C-lobes of HER2 kinase domain, which may exert indirect influence to inhibitor binding. Most investigated inhibitors exhibit weak binding strength to both wild-type and mutant HER2, which can be attributed to steric hindrance that impairs ligand compatibility with HER2 active pocket. However, the cognate inhibitor lapatinib and the non-cognate inhibitor bosutinib were predicted to have low affinity for wild-type HER2 but high affinity for HER2(YVMA) mutant, which was confirmed by subsequent kinase assay experiments; the inhibitory potencies of bosutinib against wild-type and mutant HER2 were determined to be IC(50) > 1000 and =27 nM, respectively, suggesting that the bosutinib might be exploited as a selective inhibitor for mutant over wild-type HER2. Structural examination revealed that formation of additional non-bonded interactions such as hydrogen bonds and hydrophobic contacts with HER2 A-loop region due to G776(YVMA) insertion is the primary factor to improve bosutinib affinity upon the mutation.