Photodynamic Therapy Synergizes CD47 Blockade Strategy for Enhanced Antitumor Therapy.

The antitumor strategies based on innate immunity activation have become favored by researchers in recent years. In particular, strategies targeting antiphagocytic signaling blockade to enhance phagocytosis have been widely reported. For example, the addition of prophagocytic signals such as calreticulin could make the strategy significantly more effective. In this study, an antitumor strategy that combines photodynamic therapy (PDT) with CD47 blockade has been reported. This approach promotes the maturation of dendritic cells and the presentation of tumor antigens by PDT-mediated tumor immunogenic cell death, as well as the enhancement of cytotoxic T lymphocyte infiltration in tumor areas and the phagocytic activity of phagocytes. Furthermore, the downregulation and blockage of CD47 protein could further promote phagocytic activity, strengthen the innate immune system, and ultimately elevate the antitumor efficacy and inhibit tumor metastasis.

Fluorogenic Aptamer-Based Hybridization Chain Reaction for Signal-Amplified Imaging of Apurinic/Apyrimidinic Endonuclease 1 in Living Cells.

A fluorogenic aptamer (FA)-based hybridization chain reaction (HCR) could provide a sensitive and label-free signal amplification method for imaging molecules in living cells. However, existing FA-HCR methods usually face some problems, such as a complicated design and significant background leakage, which greatly limit their application. Herein, we developed an FA-centered HCR (FAC-HCR) method based on a remote toehold-mediated strand displacement reaction. Compared to traditional HCRs mediated by four hairpin probes (HPs) and two HPs, the FAC-HCR displayed significantly decreased background leakage and improved sensitivity. Furthermore, the FAC-HCR was used to test a non-nucleic acid target, apurinic/apyrimidinic endonuclease 1 (APE1), an important BER-involved endonuclease. The fluorescence analysis results confirmed that FAC-HCR can reach a detection limit of 0.1174 U/mL. By using the two HPs for FAC-HCR with polyetherimide-based nanoparticles, the activity of APE1 in living cells can be imaged. In summary, this study could provide a new idea to design an FA-based HCR and improve the performance of HCRs in live cell imaging.

Reversible flexoelectric domain engineering at the nanoscale in van der Waals ferroelectrics.

The universal flexoelectric effect in solids provides a mechanical pathway for controlling electric polarization in ultrathin ferroelectrics, eliminating potential material breakdown from a giant electric field at the nanoscale. One challenge of this approach is arbitrary implementation, which is strongly hindered by one-way switching capability. Here, utilizing the innate flexibility of van der Waals materials, we demonstrate that ferroelectric polarization and domain structures can be mechanically, reversibly, and arbitrarily switched in two-dimensional CuInP2S6 via the nano-tip imprinting technique. The bidirectional flexoelectric control is attributed to the extended tip-induced deformation in two-dimensional systems with innate flexibility at the atomic scale. By employing an elastic substrate, artificial ferroelectric nanodomains with lateral sizes as small as ~80 nm are noninvasively generated in an area of 1 µm2, equal to a density of 31.4 Gbit/in2. Our results highlight the potential applications of van der Waals ferroelectrics in data storage and flexoelectronics.

Origin of Interfacial Orbital Reconstruction in Perovskite Superlattices.

The competition between on-site electronic correlation and local crystal field stands out as a captivating topic in research. However, its physical ramifications often get overshadowed by influences of strong periodic potential and orbital hybridization. The present study reveals this competition may become more pronounced or even dominant in two-dimensional systems, driven by the combined effects of dimensional confinement and orbital anisotropy. This leads to electronic orbital reconstruction in certain perovskite superlattices or thin films. To explore the emerging physics, we investigate the interfacial orbital disorder-order transition with an effective Hamiltonian and how to modulate this transition through strains.

The association between the MELD-XI score and heart failure in patients with acute myocardial infarction after coronary artery stenting-a retrospective study.

Background: The model for end-stage liver disease (MELD) score is a marker used to evaluate end-stage liver disease in patients with liver failure and is suggested to be valuable in evaluating heart diseases such as heart failure. Because patients with heart failure and myocardial infarction often use anticoagulants, there is an impact on the international normalized ratio (INR). Therefore, removing the INR from MELD score to form MELD-XI score may help to more accurately evaluate the cardiac function in patients with heart failure. This study was conducted to examine the predictive value of MELD-XI score in patients with acute myocardial infarction after coronary artery stenting, as there is a lack of literature in this area. Methods: The data of 318 patients with acute myocardial infarction admitted to The People's Hospital of Dazu from January 2018 to January 2021 was retrospectively collected. According to the MELD-XI score on admission, the patients were divided into a high-MELD-XI score group (n=159) and a low-MELD-XI score group (n=159). The patients were followed up for 1 year after surgery to observe the long-term prognosis and the long-term prognosis of the 2 groups was compared. Results: Compared with that in the low-MELD-XI score group, the left ventricular ejection fraction in the high-MELD-XI score group was significantly reduced (51.61%±7.66% vs. 60.48%±5.94%; P<0.001), while the level of N-terminal pro-B-type natriuretic peptide (NT-proBNP) increased significantly (821.58±461.81 vs. 723.51±335.16 ng; P=0.031). The MELD-XI score had a certain predictive value for heart failure in patients with acute myocardial infarction after coronary artery stenting, and the area under the curve was 0.730 (95% CI: 0.670-0.791; P<0.001). The MELD-XI score had a predictive value for death in patients with acute myocardial infarction after coronary artery stenting, and the area under the curve was 0.704 (95% CI: 0.564-0.843; P=0.022). MELD-XI score was significantly negatively correlated with left ventricular ejection fraction in patients with acute myocardial infarction after coronary artery stenting (r=-0.444; P<0.001). Conclusions: MELD-XI could evaluate the cardiac function of patients with acute myocardial infarction after coronary artery stenting, which was valuable in predicting the prognosis.

Orbital distortion and electric field control of sliding ferroelectricity in a boron nitride bilayer.

Recent experiments confirm that two-dimensional boron nitride (BN) films possess room-temperature out-of-plane ferroelectricity when each BN layer is sliding with respect to each other. This ferroelectricity is attributed to the interlayered orbital hybridization or interlayer charge transfer in previous work. In this work, we attempt to understand the sliding ferroelectricity from the perspective of orbital distortion of long-pair electrons. Using the maximally localized Wannier function method and first-principles calculations, the out-of-planepzorbitals of BN are investigated. Our results indicate that the interlayer van der Waals interaction causes the distortion of the Npzorbitals. Based on the picture of out-of-plane orbital distortion, we propose a possible mechanism to tune the ferroelectric polarization by external fields, including electric field and stress field. It is found that both the polarization intensity and direction can be modulated under the electric field. The polarization intensity of the system can also be controlled by stress field perpendicular to the plane. This study will provide theoretical help in the device design based on sliding ferroelectrics.

Facile preparation of a metal-phenolic network-based lymph node targeting nanovaccine for antitumor immunotherapy.

Cancer vaccines are being explored for enhanced cancer immunotherapy and prophylaxis. Some of their prevailing weaknesses, however, such as complicated preparation, poor biocompatibility, and failure to elicit strong cellular immune responses, have limited their further clinical applications. Here, we reported a multifunctional nanovaccine that was prepared in a quick and simple way. During the self-assembly of metal-phenolic networks (MPNs), the antigen ovalbumin (OVA) and immunoreactive chlorogenic acid (CHA) were simultaneously loaded. Owing to its dual pH and reduction sensitivities, the nanovaccine could deliver antigens into the cytoplasm of dendritic cells (DCs) and facilitate the cross-presentation of antigens. Moreover, the results of in vivo immunization assays demonstrated that the nanovaccine significantly excited the antigen presentation of DCs and provoked a robust cellular immune response with the restrained activation of regulatory T cells (Tregs), by targeting lymph nodes and executing the function of CHA. In vivo antitumor assays indicated that the nanovaccine with good biocompatibility afforded conspicuous cancer treatment and prevention effects. Overall, the nanovaccine presented in this study shows a promise for potentiating cancer immunotherapy by the lymph node-targeted delivery. STATEMENT OF SIGNIFICANCE: Cancer nanovaccines can be used for cancer immunotherapy. However, some existing shortcomings, such as cumbersome preparation, poor biocompatibility, and failure to elicit strong immune responses, limit the clinical application of cancer nanovaccines. This study developed a multifunctional nanovaccine that was readily prepared through the self-assembly of metal-phenolic networks. The nanovaccine with dual pH and reduction sensitivities could efficiently promote the antigen lysosome escape and cross-presentation. In vivo, it efficiently delivered antigen into lymph nodes and provoked strong cellular immune responses, and thus it showed significant cancer immunotherapy and prevention effect.

Large-Scale Domain Engineering in Two-Dimensional Ferroelectric CuInP2S6 via Giant Flexoelectric Effect.

Room-temperature ferroelectricity in two-dimensional (2D) materials is a potential for developing atomic-scale functional devices. However, as a key step for the technology implementations of 2D ferroelectrics in electronics, the controllable generation of uniform domains remains challenging at the current stage because domain engineering through an external electric field at the 2D limit inevitably leads to large leakage currents and material breakdown. Here, we demonstrate a voltage-free method, the flexoelectric effect, to artificially generate large-scale stripe domains in 2D ferroelectric CuInP2S6 with single domain lateral size at the scale of several hundred microns. With giant strain gradients (∼106 m-1), we mechanically switch the out-of-plane polarization in ultrathin CuInP2S6. The flexoelectric control of polarization is understood with a distorted Landau-Ginzburg-Devonshire double well model. Through substrate strain engineering, the stripe domain density is controllable. Our results highlight the potential of developing van der Waals ferroelectrics-based flexible electronics.

Ordered Macroporous Superstructure of Nitrogen-Doped Nanoporous Carbon Implanted with Ultrafine Ru Nanoclusters for Efficient pH-Universal Hydrogen Evolution Reaction.

The electrochemical hydrogen evolution reaction (HER) is an attractive technology for the mass production of hydrogen. Ru-based materials are promising electrocatalysts owing to the similar bonding strength with hydrogen but much lower cost than Pt catalysts. Herein, an ordered macroporous superstructure of N-doped nanoporous carbon anchored with the ultrafine Ru nanoclusters as electrocatalytic micro/nanoreactors is developed via the thermal pyrolysis of ordered macroporous single crystals of ZIF-8 accommodating Ru(III) ions. Benefiting from the highly interconnected reticular macro-nanospaces, this superstrucure affords unparalleled performance for pH-universal HER, with order of magnitude higher mass activity compared to the benchmark Pt/C. Notably, an exceptionally low overpotential of only 13 mV@10 mA cm-2 is required for HER in alkaline solution, with a low Tafel slope of 40.41 mV dec-1 and an ultrahigh turnover frequency value of 1.6 H2 s-1 at 25 mV, greatly outperforming Pt/C. Furthermore, the hydrogen generation rates are almost twice those of Pt/C during practical overall alkaline water splitting. A solar-to-hydrogen system is also demonstrated to further promote the application. This research may open a new avenue for the development of advanced electrocatalytic micro/nanoreactors with controlled morphology and excellent performance for future energy applications.

Understanding the Activity of Single-Atom Catalysis from Frontier Orbitals.

The d-band center and charge states are often used to analyze the catalytic activity of noble or transition metal surfaces and clusters, but their applicability for single-atom catalysts (SACs) is unsure. This work suggests that the spatial structure and orientation of frontier orbitals which are closest to the Fermi level of SACs play a vital role. Taking adsorption of several molecules and CO oxidization on C_{3}N-supported single-atom Au as examples, we demonstrate that adsorption and catalytic activities are well correlated with the characteristics of frontier orbitals. This work provides an effective guidance for understanding the performance of single-atom catalysts.

Tailoring the Electronic Structure of Transition Metals by the V2C MXene Support: Excellent Oxygen Reduction Performance Triggered by Metal-Support Interactions.

The enhancement of oxygen reduction reaction (ORR) activity can significantly boost the performance of fuel cells. MXene-supported transition metals with strong metal-support interactions (SMSI) are an effective strategy to increase the catalytic activity and durability while decreasing the usage of noble metals. Herein, a series of composites of transition-metal atoms (Ni, Pd, Pt, Cu, Ag, and Au) deposited on V2C MXene are designed as potential catalysts for ORR using density functional theory. The calculation results demonstrate that all the transition metals prefer to form a monolayer on V2C (TMML/V2C) with high thermodynamic stability because of SMSI, in which the Pd, Pt, Ag, and Au monolayers exhibit high chemical stability during the ORR process. PtML/V2C exhibits the highest activity toward ORR with the overpotential down to 0.38 V and the largest energy barrier of 0.48 eV. The excellent catalytic performance originates from the modification of the electronic structure by the V2C support because of SMSI. Our studies elucidate the SMSI between transition-metal atoms and V2C MXene from the atomic level and thus rationally design the ORR catalyst at the cathode of fuel cells to enhance the activity while possessing high stability and less Pt usage.

MXene (Ti3C2Tx) and Carbon Nanotube Hybrid-Supported Platinum Catalysts for the High-Performance Oxygen Reduction Reaction in PEMFC.

The metal-support interaction offers electronic, compositional, and geometric effects that could enhance catalytic activity and stability. Herein, a high corrosion resistance and an excellent electrical conductivity MXene (Ti3C2Tx) hybrid with a carbon nanotube (CNT) composite material is developed as a support for Pt. Such a composite catalyst enhances durability and improved oxygen reduction reaction activity compared to the commercial Pt/C catalyst. The mass activity of Pt/CNT-MXene demonstrates a 3.4-fold improvement over that of Pt/C. The electrochemical surface area of Pt/CNT-Ti3C2Tx (1:1) catalysts shows only 6% drop with respect to that in Pt/C of 27% after 2000 cycle potential sweeping. Furthermore, the Pt/CNT-Ti3C2Tx (1:1) is used as a cathode catalyst for single cell and stack, and the maximum power density of the stack reaches 138 W. The structure distortion of the Pt cluster induced by MXene is disadvantageous to the desorption of O atoms. This issue can be solved by adding CNT on MXene to stabilize the Pt cluster. These remarkable catalytic performances could be attributed to the synergistic effect between Pt and CNT-Ti3C2Tx.

An electronic perturbation in TiC supported platinum monolayer catalyst for enhancing water-gas shift performance: DFT study.

The water-gas shift (WGS) reaction behaviors over the TiC(0 0 1) supported Pt monolayer catalyst (PtML/TiC(0 0 1)) are investigated by using the spin-unrestricted density functional theory calculations. Importantly, we find that the PtML/TiC(0 0 1) system exhibits a much lower density of Pt-5d states nearby the Fermi level compared with that for Pt(1 1 1), and the monolayer Pt atoms undergo an electronic perturbation when in contact with TiC(0 0 1) support that would strongly improve the WGS activity of supported Pt atoms. Our calculations clearly indicate that the dominant reaction path follows a carboxyl mechanism involving a key COOH intermediate, rather than the common redox mechanism. Furthermore, through the detailed comparisons, the results demonstrate that the strong interactions between the monolayer Pt atoms and TiC(0 0 1) support make PtML/TiC(0 0 1) a highly active catalyst for the low-temperature WGS reaction. Following the route presented by Bruix et al (2012 J. Am. Chem. Soc. 134 8968-74), the positive effect derived from strong metal-support interaction in the metal/carbide system is revealed.

Strong metal-support interactions impart activity in the oxygen reduction reaction: Au monolayer on Mo2C (MXene).

The rational design of low-cost, high-efficiency, corrosion-resistant and persistent-activity oxygen reduction reaction (ORR) electrocatalysts is a common goal for the large-scale application of fuel cells. Inspired by the excellent characteristics of MXenes when used as substrate materials and recent experiments of depositing metal nanoparticles on MXenes, we systematically investigated monolayer metal thin films decorated by Mo2C (MXene) (MML/Mo2C, M = Cu, Pd, Pt, Ag and Au) as ORR catalysts using density functional theory. According to the stability and adsorption properties, we speculate that AuML/Mo2C possesses outstanding ORR performance and enhanced durability in comparison with Pt/C catalysts. The ORR on AuML/Mo2C proceeds through a four-electron reduction pathway with comparable or even better activity than Pt(1 0 0), Pt(1 1 1) and commercial Pt/C catalysts both kinetically and thermodynamically. Strong metal-support interactions give rise to larger electronic perturbations in the supported Au monolayer in contact with Mo2C, which strengthen the adsorption of oxygen-containing species and enhance the catalytic activity. Our current results indicate that AuML/Mo2C is a promising ORR catalyst candidate to replace precious Pt/C catalysts due to its good stability, enhanced durability, low cost and high activity. We hope our results will inspire more experimental and theoretical research to further design, explore and apply advanced metal monolayer-supported MXene composites.

How does the electric current propagate through fully-hydrogenated borophene?

We study the electronic transport properties of two-dimensional (2D) fully-hydrogenated borophene (namely, borophane), using density functional theory and non-equilibrium Green's function approaches. Borophane shows a perfect electrical transport anisotropy and is promising for applications. Along the peak- or equivalently the valley-parallel direction, 2D borophane exhibits a metallic characteristic and its current-voltage (I-V) curve shows a linear behavior, corresponding to the ON state in borophane-based nano-switches. In this case, electrons mainly propagate via the B-B bonds along the linear boron chains. In contrast, electron transmission is almost forbidden along the perpendicular buckled direction (i.e., the OFF state), due to its semi-conductor property. Our work demonstrates that 2D borophane could combine metal and semiconductor features and may be a promising candidate for nano-switching materials with a stable structure and high ON/OFF ratio.

Gap Symmetry of the Heavy Fermion Superconductor CeCu_{2}Si_{2} at Ambient Pressure.

Recent observations of two nodeless gaps in superconducting CeCu_{2}Si_{2} have raised intensive debates on its exact gap symmetry, while a satisfactory theoretical basis is still lacking. Here we propose a phenomenological approach to calculate the superconducting gap functions, taking into consideration both the realistic Fermi surface topology and the intra- and interband quantum critical scatterings. Our calculations yield a nodeless s^{±}-wave solution in the presence of strong interband pairing interaction, in good agreement with experiments. This provides a possible basis for understanding the superconducting gap symmetry of CeCu_{2}Si_{2} at ambient pressure and indicates the potential importance of multiple Fermi surfaces and interband pairing interaction in understanding heavy fermion superconductivity.

Repairing single and double atomic vacancies in a C3N monolayer with CO or NO molecules: a first-principles study.

Even the simplest point defect in a two-dimensional (2D) material can have a significant influence on its electronic, magnetic, and chemical properties. Defect repairing in 2D materials has been a focus of concern in recent years. Based on first-principles calculations, the repair of C and N single vacancies with CO or NO molecules in a C3N monolayer has been studied. The repair process consists of two steps, i.e., filling of the vacancy with the first molecule and removal of the extra O atom by a second molecule. Overall, the repair processes of C and N single vacancies by CO or NO molecules are both thermodynamically and kinetically favorable, as evidenced by the significant energy released and the small energy barriers. In addition, the electronic and magnetic properties and the chemical activity of the C3N monolayer before and after the defect repair have been studied systematically. In addition to single vacancies, the repair of double vacancies with CO was also studied; this process is much less kinetically favorable than the case of single vacancies. This study provides useful insight into the effects of simple atomic vacancies on the physical and chemical properties of the C3N 2D semiconductor and also presents a promising strategy for repairing vacancies.

Synthesis, Structure, and Properties of the Layered Oxyselenide Ba2CuO2Cu2Se2.

A new layered oxyselenide, Ba2CuO2Cu2Se2, was synthesized under high-pressure and high-temperature conditions and was characterized via structural, magnetic, and transport measurements. It crystallizes into space group I4/ mmm and consists of a square lattice of [CuO2] planes and antifluorite-type [Cu2Se2] layers, which are alternately stacked along the c axis. The lattice parameters are obtained as a = b = 4.0885 Å and c = 19.6887 Å. The Cu-O bond length is given by half of the lattice constant a, i.e., 2.0443 Å. Ba2CuO2Cu2Se2 is a semiconductor with a resistivity of ∼18 mΩ·cm at room temperature. No magnetic transition was found in the measured temperature range, and the Curie-Weiss temperature was obtained as -0.2 K, suggesting a very weak exchange interaction. The DFT+ Ueff calculation demonstrates that the band gap is about 0.2 eV for the supposed antiferromagnetic order, and the density of state near the top of the valence band is mainly contributed from the Se 4p electrons.

Density functional study on the high catalytic performance of single metal atoms on the NbC(001) surface.

The adsorption and activation of O2 is regarded as the first critical step for the oxygen reduction reaction (ORR), and catalysts with a high performance toward O2 adsorption and activation would provide a theoretical foundation for further investigations. Here, we have studied the adsorption and electronic properties as well as the catalytic activities of group 9-11 single metal atoms deposited on NbC(001), denoted M/NbC(001). According to the location of the d-band centers and the frontier molecular orbital analysis, single metals of Co, Rh, Ir and Ni on NbC(001) exhibit higher activities than other metals (Pd, Pt, Cu, Ag and Au). The quite different catalytic activities of M/NbC(001) may be attributed to the differences in their electro-negativities and work-functions. Meanwhile, the reasonable stabilities of Co, Rh, Ir and Ni on NbC(001) were clarified by investigating the agglomeration resistance and oxidation resistance, and the results indicate that Co and Ni have poor oxidative stability, and Rh and Ir are antioxidants on NbC(001). Further research into the adsorption and activation of O2 confirmed the outstanding properties of Rh/NbC(001) and Ir/NbC(001), which may provide great opportunities to find alternative catalysts.

The rectifying and negative differential resistance effects in graphene/h-BN nanoribbon heterojunctions.

We investigate the electronic transport properties of four types of lateral graphene/h-BN nanoribbon heterojunctions using the non-equilibrium Green's function method in combination with the density functional theory. The results show that the heterojunction displays an interesting rectifying effect when the interface has a left-right type structure, while a pronounced negative differential resistance (NDR) effect when the interface has an up-down type structure. Moreover, when the interface of the heterojunction has a left-bank or right-bank type structure, it presents the rectifying (with a larger rectification ratio) and NDR effects. This work is helpful to further construct and prepare a nanodevice based on the graphene/h-BN heterojunction materials according to the proposed structures.