Spontaneous differentiation of human induced pluripotent stem cells to odorant-responsive olfactory sensory neurons.

Pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells (iPSCs), can differentiate into almost all cell types and are anticipated to have significant applications in the field of regenerative medicine. However, there are no reports of successfully directing iPSCs to become functional olfactory sensory neurons (OSNs) capable of selectively receiving odorant compounds. In this study, we employed dual SMAD inhibition and fibroblast growth factor 8 (FGF-8, reported to dictate olfactory fates) along with N-2 and B-27 supplements in the culture medium to efficiently induce the differentiation of iPSCs into neuronal cells with olfactory function through olfactory placode. Temporal gene expression and expression of OSN-specific markers during differentiation indicated that the expression of olfactory marker proteins and various olfactory receptors (ORs), which are markers of mature OSNs, was observed after approximately one month of differentiation culture, irrespective of the differentiation cues, suggesting differentiation into OSNs. Cells that exhibited specific responses to odorant compounds were identified after administering odorant compounds to differentiated iPSC-derived OSNs. This suggests the spontaneous generation of functional OSNs expressing diverse ORs that respond to odorant compounds from iPSCs.

Metal-organic framework adhesives with exceptionally high heat resistance.

We synthesized high-heat-resistant adhesives based on metal - organic frameworks owing to their high decomposition temperature and the absence of a glass transition. Heat-resistance tests were performed on adhesive joints consisting of zeolitic imidazolate framework (ZIF)-67-based adhesives and a copper substrate. The as-synthesized ZIF-67-based adhesive exhibited heat resistances at 600 and 700°C in air and nitrogen atmospheres, respectively, comparable to those of conventional high-heat-resistant polymer-based adhesives. The degradation mechanism of the ZIF-67 adhesives was investigated, and their high heat resistance was attributed to the stable existence of the ZIF-67 qtz phase in the adhesive layer at high temperatures without the formation of voids. Thus, adhesives based on ZIF-67 and other metal - organic frameworks can be applied in high-temperature industrial systems.

By focusing on its high thermal stability and absence of glass transition, the ZIF-67 gel was found to have high potential that is comparable to existing heat-resistant adhesives.

Sintering Metal-Organic Framework Gels for Application as Structural Adhesives.

Metal-organic frameworks (MOFs)/coordination polymers are promising materials for gas separation, fuel storage, catalysis, and biopharmaceuticals. However, most applied research on MOFs is limited to these functional materials thus far. This study focuses on the potential of MOFs as structural adhesives. A sintering technique is applied to a zeolitic imidazolate framework-67 (ZIF-67) gel that enables the joining of Cu substrates, resulting in a shear strength of over 30 MPa, which is comparable to that of conventional structural adhesives. Additionally, systematic experiments are performed to evaluate the effects of temperature and pressure on adhesion, indicating that the removal of excess 2-methylimidazole and the by-product (acetic acid) from the sintered material by vaporization results in a microstructure composed of large spherical ZIF-67 crystals that are densely aggregated, which is essential for achieving a high shear strength.

Evidence of a reversible redox reaction in a liquid-electrolyte-type fluoride-ion battery.

Fluoride-ion batteries (FIBs) have received significant attention as promising alternatives to conventional lithium-ion batteries, but a reversible redox reaction has not been confirmed yet for liquid-electrolyte-type FIBs. We conducted ex situ X-ray diffraction and energy dispersive X-ray analyses for a conventional full-cell assembly of FIBs, in which BiF3, a Pb plate (or Pb powder), and tetraethylammonium fluoride dissolved in propylene carbonate were used as the positive electrode, negative electrode, and liquid electrolyte, respectively. A FIB using a Pb plate exhibited a flat operating voltage at ∼0.29 V during the discharge reaction with a discharge capacity of ∼105 mA h g-1. The reversible electrochemical reaction was, however, attained when the discharge and charge capacities were controlled to be less than 20 mA h g-1. In a such capacity-limited cycle test, Bi and PbF2 phases were formed during the discharge reaction, while BiF3 and Pb phases were generated during the charge reaction. Therefore, a reversible movement of F- ions between the BiF3 and Pb electrodes, i.e., reversible redox reaction was firstly confirmed for the liquid-electrolyte-type FIB. We also attempted to improve the reversibility at the first cycle by replacing the Pb plate with Pb powder electrodes, and consequently, the FIB using an annealed Pb powder indicated the best electrochemical performance.

Direct Sintering Behavior of Metal Organic Frameworks/Coordination Polymers.

In this study, we investigate the sintering behavior and mechanisms of metal-organic frameworks/coordination polymers (CPs) through physical and microstructural characterization of [Zn(HPO4)(H2PO4)2]·2H2Im (ZPI; a melting CP, Im = imidazole) and ZIF-8 (a non-melting CP). By performing simple compaction and subsequent sintering, a bulk body of CPs was obtained without losing the macroscopic crystallinity. The sintering behavior was found to be dependent on the temperature, heating rate, and physical properties of the CPs and, in particular, their meltability. During sintering, shrinkage occurred in both the CPs, but the observed shrinkage rate of the ZPI was in the 10-20% range, whereas that of the ZIF-8 was less than 1%. Additionally, the sintering mechanisms of the ZPI and ZIF-8 varied between low and high temperatures, and in the case of ZPI, localized melting between the primary particles was the dominant mechanism on the high-temperature side. However, substantial shrinkage did not correspond to an increase in density; on the contrary, a decrease in the apparent density of ZPI was observed as the sintering temperature was increased. The sintering technique is well established and commercially available; thus, the results obtained in this study can be utilized for optimizing the manufacturing conditions of melting CPs.

Balancing volumetric and gravimetric uptake in highly porous materials for clean energy.

A huge challenge facing scientists is the development of adsorbent materials that exhibit ultrahigh porosity but maintain balance between gravimetric and volumetric surface areas for the onboard storage of hydrogen and methane gas-alternatives to conventional fossil fuels. Here we report the simulation-motivated synthesis of ultraporous metal-organic frameworks (MOFs) based on metal trinuclear clusters, namely, NU-1501-M (M = Al or Fe). Relative to other ultraporous MOFs, NU-1501-Al exhibits concurrently a high gravimetric Brunauer-Emmett-Teller (BET) area of 7310 m2 g-1 and a volumetric BET area of 2060 m2 cm-3 while satisfying the four BET consistency criteria. The high porosity and surface area of this MOF yielded impressive gravimetric and volumetric storage performances for hydrogen and methane: NU-1501-Al surpasses the gravimetric methane storage U.S. Department of Energy target (0.5 g g-1) with an uptake of 0.66 g g-1 [262 cm3 (standard temperature and pressure, STP) cm-3] at 100 bar/270 K and a 5- to 100-bar working capacity of 0.60 g g-1 [238 cm3 (STP) cm-3] at 270 K; it also shows one of the best deliverable hydrogen capacities (14.0 weight %, 46.2 g liter-1) under a combined temperature and pressure swing (77 K/100 bar → 160 K/5 bar).