Gleditsiae fructus regulates osteoclastogenesis by inhibiting the c­Fos/NFATc1 pathway and alleviating bone loss in an ovariectomy model.

Medical and economic developments have allowed the human lifespan to extend and, as a result, the elderly population has increased worldwide. Osteoporosis is a common geriatric disease that has no symptoms and even a small impact can cause fractures in patients, leading to a serious deterioration in the quality of life. Osteoporosis treatment typically involves bisphosphonates and selective estrogen receptor modulators. However, these treatments are known to cause severe side effects, such as mandibular osteonecrosis and breast cancer, if used for an extended period of time. Therefore, it is essential to develop therapeutic agents from natural products that have fewer side effects. Gleditsiae fructus (GF) is a dried or immature fruit of Gleditsia sinensis Lam. and is composed of various triterpenoid saponins. The anti­inflammatory effect of GF has been confirmed in various diseases, and since the anti­inflammatory effect plays a major role in inhibiting osteoclast differentiation, GF was expected to be effective in osteoclast differentiation and menopausal osteoporosis; however, to the best of our knowledge, it has not yet been studied. Therefore, the present study was designed to examine the effect of GF on osteoclastogenesis and to investigate the mechanism underlying inhibition of osteoclast differentiation. The effects of GF on osteoclastogenesis were determined in vitro by tartrate­resistant acid phosphatase (TRAP) staining, pit formation assays, filamentous actin (F­actin) ring formation assays, western blotting and reverse transcription­quantitative PCR analyses. Furthermore, the administration of GF to an animal model exhibiting menopausal osteoporosis allowed for the analysis of alterations in the bone microstructure of the femur using micro­CT. Additionally, assessments of femoral tissue and serum were conducted. The present study revealed that the administration of GF resulted in a reduction in osteoclast levels, F­actin rings, TRAP activity and pit area. Furthermore, GF showed a dose­dependent suppression of nuclear factor of activated T­cells cytoplasmic, c­Fos and other osteoclastogenesis­related markers.

Chemically Stable Low-Dimensional Electrides in Transition Metal-Rich Monochalcogenides: Theoretical and Experimental Explorations.

Electrides, which are ionic crystals composed of excess anionic electrons, are of great interest as an exotic material for fundamental research and practical applications in broad fields of science and technology. However, an inherent chemical instability under ambient conditions at room temperature has been a fatal drawback to be addressed. Here, we report that transition metal-rich monochalcogenides are an emerging class of low-dimensional electrides with excellent chemical and thermal stability in air and water at room temperature through a comprehensive exploration of theoretical prediction and experimental verification. We predict new two-dimensional (2D) electrides crystallized in hexagonal P3̅m1 and P63/mmc structures with strong localization of anionic electrons in a dumbbell shape at the tetrahedral cavity of the interlayer space, which are distinct from the anionic electrons localized at the octahedral cavity in the hexagonal R3̅m structure of the previous 2D [Ca2N]+·e- and [Y2C]2+·2e- electrides. We successfully synthesized the room-temperature stable [Ti2O]2+·2e-, [Ti2S]2+·2e-, [Zr2S]2+·2e-, and primary solid solution [Hf2SxSe1-x]2+·2e- electrides, showing no structural degradation in air and water. Among them, we found that the synthesized [Ti2S]2+·2e- and [Zr2S]2+·2e- electrides are crystallized in orthorhombic symmetry (Pnnm), showing the feature of a one-dimensional (1D) electride with an anionic electron chain, which has never been reported yet. In addition to the successful finding of new 1D and 2D electrides, we discuss the self-passivation effect-driven chemical stability and the role of anionic electrons in determining the physical properties of the newly discovered electrides.

Non-oxidized bare copper nanoparticles with surface excess electrons in air.

Copper (Cu) nanoparticles (NPs) have received extensive interest owing to their advantageous properties compared with their bulk counterparts. Although the natural oxidation of Cu NPs can be alleviated by passivating the surfaces with additional moieties, obtaining non-oxidized bare Cu NPs in air remains challenging. Here we report that bare Cu NPs with surface excess electrons retain their non-oxidized state over several months in ambient air. Cu NPs grown on an electride support with excellent electron transfer ability are encapsulated by the surface-accumulated excess electrons, exhibiting an ultralow work function of ~3.2 eV. Atomic-scale structural and chemical analyses confirm the absence of Cu oxide moiety at the outermost surface of air-exposed bare Cu NPs. Theoretical energetics clarify that the surface-accumulated excess electrons suppress the oxygen adsorption and consequently prohibit the infiltration of oxygen into the Cu lattice, provoking the endothermic reaction for oxidation process. Our results will further stimulate the practical use of metal NPs in versatile applications.

Symmetry Dictated Grain Boundary State in a Two-Dimensional Topological Insulator.

Grain boundaries (GBs) are ubiquitous in solids and have been of central importance in understanding the nature of polycrystals. In addition to their classical roles, topological insulators (TIs) offer a chance to realize GBs hosting distinct topological states that can be controlled by their crystal symmetries. However, such roles of crystalline symmetry in two-dimensional (2D) TIs have not been definitively measured yet. Here, we present the first direct evidence of a symmetry-enforced metallic state along a GB in 1T'-MoTe2, a prototypical 2D TI. Using scanning tunneling microscopy, we show a metallic state along a GB with nonsymmorphic lattice symmetry and its absence along another boundary with symmorphic symmetry. Our atomistic simulations demonstrate in-gap Weyl semimetallic states for the former, whereas they demonstrate gapped states for the latter, explaining our observation well. The observed metallic state, tightly linked to its crystal symmetry, can be used to create a stable conducting nanowire inside TIs.

Water- and acid-stable self-passivated dihafnium sulfide electride and its persistent electrocatalytic reaction.

Electrides have emerged as promising materials with exotic properties, such as extraordinary electron-donating ability. However, the inevitable instability of electrides, which is caused by inherent excess electrons, has hampered their widespread applications. We report that a self-passivated dihafnium sulfide electride ([Hf2S]2+∙2e-) by double amorphous layers exhibits a strong oxidation resistance in water and acid solutions, enabling a persistent electrocatalytic hydrogen evolution reaction. The naturally formed amorphous Hf2S layer on the cleaved [Hf2S]2+∙2e- surface reacts with oxygen to form an outermost amorphous HfO2 layer with ~10-nm thickness, passivating the [Hf2S]2+∙2e- electride. The excess electrons in the [Hf2S]2+∙2e- electride are transferred through the thin HfO2 passivation layer to water molecules under applied electric fields, demonstrating the first electrocatalytic reaction with excellent long-term sustainability and no degradation in performance. This self-passivation mechanism in reactive conditions can advance the development of stable electrides for energy-efficient applications.