Electric field-induced magnetochiral dichroism in a ferroaxial crystal.

In a chiral medium, any mirror symmetries are broken, which induces unique physical properties represented by natural optical rotation. When electromagnetic waves propagate through a chiral medium placed in a magnetic field, the refractive index, or equivalently, the absorption encountered by the electromagnetic waves differs depending on whether it travels parallel or antiparallel to the magnetic field. Such a phenomenon is known as magnetochiral dichroism (MChD), which is the characteristic interplay between chirality and magnetism. Similar to chirality, the so-called ferroaxial order, an emergent ferroic state of crystalline materials, is also characterized by mirror symmetry breaking. In contrast to chiral materials, however, the mirror symmetry perpendicular to the crystalline principal axis is allowed in ferroaxial materials. In other words, chirality and thus phenomena unique to chirality can be induced by breaking the remaining mirror symmetry by applying an electric field. Here, we show electric control of chirality and resulting electric field-induced MChD (E-MChD) of the short-wavelength infrared region in a ferroaxial crystal, NiTiO3. We performed spectroscopy measurements of E-MChD by taking a difference of absorption coefficients obtained with and without electric and magnetic fields. As a result, E-MChD was observed around the excitation energy corresponding to Ni2+ d-d magnetic-dipole transitions. The result is nicely explained by adopting the theory of MChD concerning the pseudo-Stark splitting of the energy state. Ferroaxial materials therefore provide platforms to achieve electric control of chirality-related phenomena.

Nonvolatile Switching of Large Nonreciprocal Optical Absorption at Shortwave Infrared Wavelengths.

We report large nonreciprocal optical absorption at shortwave infrared (SWIR) wavelengths in the magnetoelectric (ME) antiferromagnet (AFM) LiNiPO_{4}. The difference in absorption coefficients for light propagating in opposite directions, divided by the sum, reaches up to ∼40% at 1450 nm. Moreover, the nonreciprocity is switched by a magnetic field in a nonvolatile manner. Using symmetry considerations, we reveal that the large nonreciprocal absorption is attributed to Ni^{2+} d-d transitions through the spin-orbit coupling. Furthermore, we propose that an even larger nonreciprocity can be achieved for a Ni-based ME AFM where electric dipoles of every NiO_{6} unit and Ni^{2+} spins are orthogonal and, respectively, form a collinear arrangement. This study provides a pathway toward nonvolatile switchable one-way transparency of SWIR light.

Characteristics of macrophage aggregates prepared by rotation culture and their response to polymeric materials.

Understanding the interaction between macrophages and biomaterials is important for the creation of new biomaterials and the development of technologies to control macrophage function. Since macrophages are strongly adhesive, caution is required when performing in vitro evaluations. Similarly, when THP-1 cells, macrophage precursor cells, are differentiated into macrophages using phorbol-12-myristate-13-acetate (PMA), it becomes difficult to detach them from the adherent substrate, which has been a problem on investigation of immunological responses to biomaterials. In this study, the interaction of THP-1 cell-differentiated macrophages with biomaterials was analyzed based on a new method of seeding THP-1 cells. THP-1 cells were cultured in static and rotation culture without and with PMA. In undifferentiated THP-1 cells, there was no change in cellular function between static and rotation cultures. In rotation culture with PMA, THP-1 cells differentiated and formed macrophage aggregates. IL-1ß and MRC1 expression in macrophage aggregates was examined after differentiation and M1/M2 polarization. Macrophage aggregates in rotation culture tended to be polarized toward M2 macrophages compared with those in static culture. In the evaluation of the responses of macrophage aggregates to several kinds of polymeric materials, macrophage aggregates showed different changes in MRC1 expression over time at 30, 50, and 70 rpm. Rotation speed of 30 rpm was considered most appropriate condition in that it gave stable results with the same trend as obtained with static culture. The use of macrophage aggregates obtained by rotational culture is expected to provide new insights into the evaluation of inflammatory properties of biomaterials.

Chemical Aspect of Displacive-Type Ferroaxial Phase Transition from Perspective of Second-Order Jahn-Teller Effect: NASICON Systems as an Example.

Ferroaxial order, characterized by a rotational arrangement of electric dipoles, attracts increasing attention in terms of a new family of ferroic orders. However, there has been no chemical guideline for exploring crystalline materials showing ferroaxial order, namely ferroaxial materials. Here, we present a chemical guideline grounded in staggered polyhedral connectivity, which we propose as a structural prerequisite for ferroaxial order, and the second-order Jahn-Teller (SOJT) theory extended from molecular orbitals to electronic band structures. Na-superionic conductors (NASICON) including NaM2(PO4)3 (M = early-transition or post-transition metal) are identified as potential ferroaxial materials because of their staggered structures composed of MO6 octahedra and PO4 tetrahedra. However, ferroaxial phase transitions hardly occur in some of the NASICON systems, which offers a platform to uncover a hidden factor playing an important role in driving this system into ferroaxial states. Our first-principles calculations demonstrate that a ferroaxial phase transition in NASICON systems occurs only when SOJT interaction is symmetrically allowed, that is, energy-lowering chemical bonds are formed as a consequence of the distortion. Our proposals would be not limited to NASICON systems but applicable to a variety of compounds and provide new insight into the exploration of displacive-type ferroaxial materials.

Detecting Magnetoelectric Effect in a Metallic Antiferromagnet via Nonreciprocal Rotation of Reflected Light.

Certain types of media breaking both space-inversion (P) and time-reversal (T) symmetries but preserving their combination PT exhibit the polarization rotation of reflected light even when that of transmitted light is prohibited. Such an effect is termed nonreciprocal rotation of reflected light (NRR). Although NRR shows nearly the same phenomenon as the magnetooptical Kerr effect or, equivalently, the Hall effect at optical frequencies, its origin is distinct and ascribed to a magnetoelectric (ME) effect at optical frequencies, i.e., the optical ME effect. Here we show the observation of NRR in a metallic antiferromagnet TbB_{4}. The result demonstrates that the ME effect in a metallic system, which is considered to be ill defined, can be detected using reflected light. Furthermore, we spatially resolve antiferromagnetic domains in TbB_{4} by microscope observations of NRR. Our work offers a unique way to probe the ME effect in metallic systems.

Fabrication of Polypropylene Nanoplastics Via Thermal Oxidation Reaction for Human Cells Responsiveness Studies.

With the current worldwide increasing use of plastics year by year, nanoplastics (NPs) have become a global threat to environmental and public health concerns. Among plastics, polypropylene (PP) is widely used in industrial and medical applications. Owing to the lack of validated detection methods and standard materials for PP NPs, understanding the impact of PP NPs on the environmental and biological systems is still limited. Here, isotactic polypropylene (iPP) was fabricated into oxidized polypropylene micro/nanoplastics (OPPs) via a thermal oxidation using hydrogen peroxide (H2O2) under various heating temperatures. The resulting OPPs were investigated in terms of the size distribution, surface chemistry, morphology, and thermal property as well as their concentration-dependent cytotoxicity to a human intestinal epithelial cell line (Caco-2), which could be a route to uptake NPs into the body through the food chain. The average diameters of the OPPs decrease with increasing reaction temperature. The OPPs obtained at 175 °C (OPP175) were spherical in shape and had a rough surface, with size distributions of approximately 0.14 ± 0.02 µm. A significant increase in the carbonyl content of the oxidized product was confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy analyses. Caco-2 cells were exposed to OPP175 in a dose-dependent manner, and a significant loss of cell viability occurred at the concentration of 100 µg/mL. Thus, this study provides a fundamental approach for the fabrication of a model of NPs for the urgently demanded in vitro and in vivo studies to assess the potential impact of NPs on biological systems.

Mechanoregulation of Osteoclastogenesis-Inducing Potentials of Fibrosarcoma Cell Line by Substrate Stiffness.

A micro-physiological system is generally fabricated using soft materials, such as polydimethylsiloxane silicone (PDMS), and seeks an inflammatory osteolysis model for osteoimmunological research as one of the development needs. Microenvironmental stiffness regulates various cellular functions via mechanotransduction. Controlling culture substrate stiffness may help spatially coordinate the supply of osteoclastogenesis-inducing factors from immortalized cell lines, such as mouse fibrosarcoma L929 cells, within the system. Herein, we aimed to determine the effects of substrate stiffness on the osteoclastogenesis-inducing potential of L929 cells via cellular mechanotransduction. L929 cells showed increased expression of osteoclastogenesis-inducing factors when cultured on type I collagen-coated PDMS substrates with soft stiffness, approximating that of soft tissue sarcomas, regardless of the addition of lipopolysaccharide to augment proinflammatory reactions. Supernatants of L929 cells cultured on soft PDMS substrates promoted osteoclast differentiation of the mouse osteoclast precursor RAW 264.7 by stimulating the expression of osteoclastogenesis-related gene markers and tartrate-resistant acid phosphatase activity. The soft PDMS substrate inhibited the nuclear translocation of YES-associated proteins in L929 cells without reducing cell attachment. However, the hard PDMS substrate hardly affected the cellular response of the L929 cells. Our results showed that PDMS substrate stiffness tuned the osteoclastogenesis-inducing potential of L929 cells via cellular mechanotransduction.

Extraction and Biological Evaluation of Matrix-Bound Nanovesicles (MBVs) from High-Hydrostatic Pressure-Decellularized Tissues.

Decellularized tissues are widely used as promising materials in tissue engineering and regenerative medicine. Research on the microstructure and components of the extracellular matrix (ECM) was conducted to improve the current understanding of decellularized tissue functionality. The presence of matrix-bound nanovesicles (MBVs) embedded within the ECM was recently reported. Results of a previous experimental investigation revealed that decellularized tissues prepared using high hydrostatic pressure (HHP) exhibited good in vivo performance. In the current study, according to the hypothesis that MBVs are one of the functional components in HHP-decellularized tissue, we investigated the extraction of MBVs and the associated effects on vascular endothelial cells. Using nanoparticle tracking assay (NTA), transmission electron microscopy (TEM), and RNA analysis, nanosized (100-300 nm) and membranous particles containing small RNA were detected in MBVs derived from HHP-decellularized small intestinal submucosa (SIS), urinary bladder matrix (UBM), and liver. To evaluate the effect on the growth of vascular endothelial cells, which are important in the tissue regeneration process, isolated SIS-derived MBVs were exposed to vascular endothelial cells to induce cell proliferation. These results indicate that MBVs can be extracted from HHP-decellularized tissues and may play a significant role in tissue remodeling.

Effects of cognitive tasks on center-of-foot pressure displacements and brain activity during single leg stance: comparison in community-dwelling healthy older and young people.

[Purpose] This study aimed to investigate the effect of cognitive tasks on the center-of-foot pressure (COP) displacements and brain activity during single leg stance (SLS) in older people. [Participants and Methods] This study included 25 healthy older (age, 68.8 ± 4.9 years) and 25 young (age, 21.0 ± 0.9 years) participants. Participants performed SLS for 35 s under a single-task (ST) and three dual-tasks (DTs), namely verbal, subtraction, and recall tasks. We measured the total length of COP (COP_ TL ) and change in oxygenated hemoglobin (HbO2) levels during SLS under four tasks. [Results] There were no differences in COP_ TL and HbO2 levels in the young group, whereas COP_ TL in the recall task was significantly longer than in ST in the older group. In the comparisons of the DTc (the relative change of DT to ST), no differences were found among three DTs in the young group, whereas the DTc of COP_ TL in the recall task was significantly higher than that in the verbal task in the older group. Regarding HbO2, no differences were observed among the four tasks in both groups. [Conclusion] These results suggest that SLS combined with a recall task may be useful for fall risk screening in healthy older individuals.

Observation of Ferrochiral Transition Induced by an Antiferroaxial Ordering of Antipolar Structural Units in Ba(TiO)Cu4(PO4)4.

Ferrochiral transition, i.e., a transition involving an emergence of chirality, provides an unique opportunity to achieve a nonvolatile reversible control of chirality with external fields. However, materials showing pure ferrochiral transitions, which are accompanied by no other types of ferroic transition, are exceedingly rare. In this study, we propose that a pure ferrochiral transition is achieved by a combination of antipolar and antiferroaxial orderings of structural units, and substantiate this proposal through a study of the chiral compound Ba(TiO)Cu4(PO4)4. Single crystal X-ray diffraction measurements have revealed that this material undergoes a second order ferrochiral transition whose order parameter is described by an antiferroaxial (staggered) rotation of antipolar structural units, thus demonstrating our proposal. Furthermore, by measuring spatial distributions of optical rotation, we successfully visualized a temperature evolution of ferrochiral domains across the transition temperature and demonstrated the relationship between chirality and optical rotation. This work provides a guide to find a pure ferrochiral transition, thus providing an opportunity to achieve a ferroic control of chirality.

Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation.

Phonon polaritons-light coupled to lattice vibrations-in polar van der Waals crystals are promising candidates for controlling the flow of energy on the nanoscale due to their strong field confinement, anisotropic propagation and ultra-long lifetime in the picosecond range1-5. However, the lack of tunability of their narrow and material-specific spectral range-the Reststrahlen band-severely limits their technological implementation. Here, we demonstrate that intercalation of Na atoms in the van der Waals semiconductor α-V2O5 enables a broad spectral shift of Reststrahlen bands, and that the phonon polaritons excited show ultra-low losses (lifetime of 4 ± 1 ps), similar to phonon polaritons in a non-intercalated crystal (lifetime of 6 ± 1 ps). We expect our intercalation method to be applicable to other van der Waals crystals, opening the door for the use of phonon polaritons in broad spectral bands in the mid-infrared domain.

Coexistence of Magnetoelectric and Antiferroelectric-like Orders in Mn3Ta2O8.

In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search for new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative, Mn3Ta2O8, is a new linear ME material. This is evidenced by the onset of magnetic-field-induced electric polarization in its collinear antiferromagnetic phase below TN = 24 K. Furthermore, we also find an antiferroelectric-like phase transition at TS = 55 K, which is attributable to an off-center displacement of magnetic Mn2+ ions. The present study shows that Mn3Ta2O8 is a rare material that exhibits both ME and antiferroelectric-like transitions. Thus, Mn3Ta2O8 may provide an opportunity to investigate the physics associated with complicated interactions between magnetic (spin) and electric dipole degrees of freedom.

Tumor growth suppression by implantation of an anti-CD25 antibody-immobilized material near the tumor via regulatory T cell capture.

In this study, we designed and synthesized an implantable anti-CD25 antibody-immobilized polyethylene (CD25-PE) mesh to suppress tumor growth by removing regulatory T cells (Tregs). The PE mesh was graft-polymerized with poly(acrylic acid), and the anti-mouse CD25 antibody was then immobilized using the 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide reaction. Immobilization of the antibody on the PE mesh was confirmed by immunostaining. The CD25-PE mesh could effectively and selectively capture CD25-positive cells through antigen-antibody interactions when the CD25-PE mesh was incubated with a suspension of mouse spleen cells, including CD25-positive cells. In addition, implantation of the CD25-PE mesh into mice subcutaneously demonstrated the Treg-capturing ability of the CD25-PE mesh with only a weak inflammatory reaction. In tumor-bearing mice, tumor growth was suppressed by subcutaneous implantation of the CD25-PE mesh near the tumor for 1 week. These results suggested that the anti-CD25 antibody-immobilized material could capture Tregs in vivo and inhibit tumor proliferation in a limited tumor-bearing mouse model. Further research is needed to facilitate cancer immunotherapy using implantable anti-CD25 antibody-immobilized material as a Treg-capturing device.

Synthesis, Structure, and Anomalous Magnetic Ordering of the Spin-1/2 Coupled Square Tetramer System K(NbO)Cu4(PO4)4.

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu4(PO4)4. Single-crystal X-ray diffraction measurements reveal that the crystal structure belongs to the tetragonal space group P4/nmm, in which Cu2+ ions align to form a quasi-two-dimensional layer of spin-1/2 coupled square tetramers. The structure is quasi-isostructural to recently reported magnetoelectric antiferromagnets, A(TiO)Cu4(PO4)4 (A = Ba, Sr, and Pb) with the P4212 space group. Despite their structural similarities, whereas the antiferromagnetic transition in A(TiO)Cu4(PO4)4 produces conventional anomalies in magnetization and heat capacity, that in K(NbO)Cu4(PO4)4 has several unusual features such as an upturn in magnetic susceptibility and a very weak specific heat anomaly that corresponds to a spin entropy release as small as 3%. These results indicate that the magnetism of K(NbO)Cu4(PO4)4 is far different from that of A(TiO)Cu4(PO4)4 and suggest that the ground state is very close to a quantum nonmagnetic singlet state. The origin of the distinct magnetism in K(NbO)Cu4(PO4)4 is discussed in terms of structural modifications of a Cu4O12 unit forming a square tetramer. Our study demonstrates that the present material family, represented by an extended chemical formula A(BO)Cu4(PO4)4 (AB = KNb, BaTi, SrTi, and PbTi), has broad chemical controllability of their magnetism. This makes this system an attractive material platform to study the physics of quantum spin-1/2 coupled square tetramers.

Elastic Modulus of ECM Hydrogels Derived from Decellularized Tissue Affects Capillary Network Formation in Endothelial Cells.

Recent applications of decellularized tissue have included the use of hydrogels for injectable materials and three-dimensional (3D) bioprinting bioink for tissue regeneration. Microvascular formation is required for the delivery of oxygen and nutrients to support cell growth and regeneration in tissues and organs. The aim of the present study was to evaluate the formation of capillary networks in decellularized extracellular matrix (d-ECM) hydrogels. The d-ECM hydrogels were obtained from the small intestine submucosa (SIS) and the urinary bladder matrix (UBM) after decellularizing with sodium deoxycholate (SDC) and high hydrostatic pressure (HHP). The SDC d-ECM hydrogel gradually gelated, while the HHP d-ECM hydrogel immediately gelated. All d-ECM hydrogels had low matrix stiffness compared to that of the collagen hydrogel, according to a compression test. D-ECM hydrogels with various elastic moduli were obtained, irrespective of the decellularization method or tissue source. Microvascular-derived endothelial cells were seeded on d-ECM hydrogels. Few cells attached to the SDC d-ECM hydrogel with no network formation, while on the HHP d-ECM hydrogel, a capillary network structure formed between elongated cells. Long, branched networks formed on d-ECM hydrogels with lower matrix stiffness. This suggests that the capillary network structure that forms on d-ECM hydrogels is closely related to the matrix stiffness of the hydrogel.

Extracellular Matrix Induces Periodontal Ligament Reconstruction In Vivo.

One of the problems in dental implant treatment is the lack of periodontal ligament (PDL), which supports teeth, prevents infection, and transduces sensations such as chewiness. The objective of the present study was to develop a decellularized PDL for supporting an artificial tooth. To this end, we prepared mouse decellularized mandible bone with a PDL matrix by high hydrostatic pressure and DNase and detergent treatments and evaluated its reconstruction in vivo. After tooth extraction, the decellularized mandible bone with PDL matrix was implanted under the subrenal capsule in rat and observed that host cells migrated into the matrix and oriented along the PDL collagen fibers. The extracted decellularized tooth and de- and re-calcified teeth, which was used as an artificial tooth model, were re-inserted into the decellularized mandible bone and implanted under the subrenal capsule in rat. The reconstructed PDL matrix for the extracted decellularized tooth resembled the decellularized mandible bone without tooth extraction. This demonstrates that decellularized PDL matrix can reconstruct PDL tissue by controlling host cell migration, which could serve as a novel periodontal treatment approach.

The Fate of Transplanted Periodontal Ligament Stem Cells in Surgically Created Periodontal Defects in Rats.

Periodontal disease is chronic inflammation that leads to the destruction of tooth-supporting periodontal tissues. We devised a novel method ("cell transfer technology") to transfer cells onto a scaffold surface and reported the potential of the technique for regenerative medicine. The aim of this study is to examine the efficacy of this technique in periodontal regeneration and the fate of transplanted cells. Human periodontal ligament stem cells (PDLSCs) were transferred to decellularized amniotic membrane and transplanted into periodontal defects in rats. Regeneration of tissues was examined by microcomputed tomography and histological observation. The fate of transplanted PDLSCs was traced using PKH26 and human Alu sequence detection by PCR. Imaging showed more bone in PDLSC-transplanted defects than those in control (amnion only). Histological examination confirmed the enhanced periodontal tissue formation in PDLSC defects. New formation of cementum, periodontal ligament, and bone were prominently observed in PDLSC defects. PKH26-labeled PDLSCs were found at limited areas in regenerated periodontal tissues. Human Alu sequence detection revealed that the level of Alu sequence was not increased, but rather decreased. This study describes a novel stem cell transplantation strategy for periodontal disease using the cell transfer technology and offers new insight for cell-based periodontal regeneration.

Magnetoelectric Behavior from S=1/2 Asymmetric Square Cupolas.

Magnetoelectric properties are studied by a combined experimental and theoretical study of a quasi-two-dimensional material composed of square cupolas, Ba(TiO)Cu_{4}(PO_{4})_{4}. The magnetization is measured up to the field above the saturation, and several anomalies are observed depending on the field directions. We propose a S=1/2 spin model with Dzyaloshinskii-Moriya interactions, which reproduces the full magnetization curves well. Elaborating the phase diagram of the model, we show that the anomalies are explained by magnetoelectric phase transitions. Our theory also accounts for the scaling of the dielectric anomaly observed in the experiments. The results elucidate the crucial role of the in-plane component of Dzyaloshinskii-Moriya interactions, which is induced by the noncoplanar buckling of a square cupola. We also predict a "hidden" phase and another magnetoelectric response, both of which appear in a nonzero magnetic field.

Electric-Field-Induced Reorientation of the Magnetic Easy Plane in a Co-Substituted BiFeO3 Single Crystal.

Single crystals of BiFe0.9Co0.1O3 and BiFe0.892Mn0.008Co0.1O3, room temperature ferroelectric ferromagnets, were successfully grown by a flux method at a high pressure of 3 GPa. Remanent magnetization measurements along 18 crystallographic directions revealed the existence of a magnetic easy plane perpendicular to the electric polarization. Reorientation of the magnetic easy plane occurred in connection with 71° ferroelectric switching by applying an electric field. This is the first demonstration of an electric field affecting the local magnetic moment of Co-substituted BiFeO3.

A(2+) Cation Control of Chiral Domain Formation in A(TiO)Cu4(PO4)4 (A = Ba, Sr).

Single crystals of two novel tetragonal chiral materials, A(TiO)Cu4(PO4)4 (A = Ba, Sr), were grown from Na2Mo2O7 flux, and their crystal and chiral domain structures were characterized. Polarized-light microscopy studies of the chiral domain structures in the crystals show that Ba(TiO)Cu4(PO4)4 mostly hosts a multidomain state, while a monodomain state predominantly appears in Sr(TiO)Cu4(PO4)4. To explain this striking difference, we quantified the chirality strength of these materials by comparing atomic positions in the chiral and nearest-achiral crystal structures, revealing larger chirality strength in Sr(TiO)Cu4(PO4)4 than in Ba(TiO)Cu4(PO4)4. Our proposed mechanisms linking the chirality strength and domain formation can account for the different occurrence frequency of chiral domains in this system.