Dielectric Relaxation and Dielectric Switching Behaviors in (N,N-Diisopropylethylamine) Tetrachloroantimonate(III).

Dielectric switches have drawn renewed attention to the study of their many potential applications with the adjustable switch temperatures (Ts ). Herein, a novel antimony-based halide semiconductor, (N,N-diisopropylethylamine) tetrachloroantimonate ((DIPEA)SbCl4 , DIPEA+ =N,N-diisopropylethylamine), with dielectric relaxation behavior and dielectric switches has been successfully synthesized. This compound, consisting of coordinated anion S b C l 4 ∞ - ${{\left[{{\rm S}{\rm b}{\rm C}{\rm l}}_{4}\right]}_{\infty }^{-}}$ chains and isolated DIPEA+ cations, undergoes an isostructural order-disorder phase transition and shows a step-like dielectric anomaly, which can function as a frequency-tuned dielectric switch with highly adjustable switch temperature (Ts ). Variable-temperature single-crystal structure analyses and first-principles molecular dynamics simulations give information about the general mechanisms of molecular dynamics. This work enriches the dielectric switch family and proves that hybrid metal halides are promising candidates for switchable physical or chemical properties.

Durable and Nontoxic Natural Rubber-Based Composites with Antibacterial Properties.

Natural rubber latex (NRL) has prophylactic properties and is used to make pathogen-isolating products like condoms and surgical gloves. However, obtaining NRL and casting it into durable products are challenging. Consequently, progress in the research and development of medical NRL products has been slow. This study aims to strengthen NR and induce it with bactericidal properties. In this regard, we introduce inorganic whiskers into the NRL and synthesize whiskers/NR composites with strong mechanical and antibacterial properties. The method proposed herein is a template method, which can rapidly and efficiently reveal the antibacterial effect of the composite latex, providing convenience for research institutions and factories studying antibacterial latex. A complete system is established for studying the antibacterial medical NRL, and a precedent is set for the relevant products.

Fabrication and DFT Calculation of Amine-Functionalized Metal-Organic Framework as a Turn-On Fluorescence Sensor for Fe3+ and Al3+ Ions.

Due to their important role in biological systems, it is urgent to develop a material that can rapidly and sensitively detect the concentration of Fe3+ and Al3+ ions. In this work, a brand-new CdII-based metal-organic framework [Cd(BTBD)2(AIC)]n (JXUST-18, BTBD = 4,7-bis(1H-1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole and H2AIC = 5-aminoisophthalic acid) with a 4-connected sql topology was designed and synthesized. The symmetrical CdII centers are linked by AIC2- ligands with µ3-η1:η1:η1:η1 coordination mode to form a [Cd2(COO)2] secondary building unit (SBU). The contiguous SBUs are further connected by BTBD ligands to form a two-dimensional (2D) layer structure. JXUST-18 can remain stable in aqueous solutions with pH values of 3-12 or in boiling water. Luminescent experiments suggest that JXUST-18 displays more than eightfold fluorescence enhancement in the presence of Fe3+ and Al3+ ions, and the detection limits for Fe3+ and Al3+ ions are 0.196 and 0.184 µM, respectively. Furthermore, the change in luminescence color is uncomplicatedly distinguishable with the naked eye under ultraviolet light at 365 nm. In addition, a series of devices based on JXUST-18 including fluorescence test strips, lamp beads, and composite films were developed to detect metal ions via visual changes in luminescence color. Significantly, JXUST-18 is a rare MOF-based turn-on fluorescence sensor for the detection of Fe3+ ions. The theoretical calculation suggests that the complexation of Fe3+/Al3+ ions and the -NH2 group contributes to fluorescence enhancement.

[Progress in replicative senescence of mesenchymal stem cells regulated by microenvironment].

Mesenchymal stem cells (MSCs) are a class of pluripotent cells that can self-renew and differentiate. Numerous studies have shown that MSCs have important roles in areas such as regenerative medicine and tissue engineering. However, it is worth noting that MSCs will gradually age during long-term in vitro expansion with decreased stemness such as weakened migration ability, slowed proliferation rate and decreased differentiation potential, which greatly hinders the application of MSCs. Currently, the microenvironment for cell growth is recognized as one of the factors causing senescence in MSCs. Recent studies point out that the latest technologies such as exogenous administration, oxygen concentration regulation and extracellular matrix (ECM) construction can delay stem cell senescence by simulating or regulating the microenvironment. Here, we review the current knowledge of the characteristics and molecular mechanisms of senescent MSCs and microenvironment strategies to maintain MSCs stemness, which can provide a reference for future large-scale application of MSCs preparations in tissue engineering and clinical studies.

Human umbilical cord-derived mesenchymal stem cells promote repair of neonatal brain injury caused by hypoxia/ischemia in rats.

Administration of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) is believed to be an effective method for treating neurodevelopmental disorders. In this study, we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism. We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy. Rat offspring were intranasally administered hUC-MSCs on postnatal day 14. We found that polypyrimidine tract-binding protein-1 (PTBP-1) participated in the regulation of lipopolysaccharide-induced maternal immune activation, which led to neonatal hypoxic/ischemic brain injury. Intranasal delivery of hUC-MSCs inhibited PTBP-1 expression, alleviated neonatal brain injury-related inflammation, and regulated the number and function of glial fibrillary acidic protein-positive astrocytes, thereby promoting plastic regeneration of neurons and improving brain function. These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.

A neurovascular unit-on-a-chip: culture and differentiation of human neural stem cells in a three-dimensional microfluidic environment.

Biological studies typically rely on a simple monolayer cell culture, which does not reflect the complex functional characteristics of human tissues and organs, or their real response to external stimuli. Microfluidic technology has advantages of high-throughput screening, accurate control of the fluid velocity, low cell consumption, long-term culture, and high integration. By combining the multipotential differentiation of neural stem cells with high throughput and the integrated characteristics of microfluidic technology, an in vitro model of a functionalized neurovascular unit was established using human neural stem cell-derived neurons, astrocytes, oligodendrocytes, and a functional microvascular barrier. The model comprises a multi-layer vertical neural module and vascular module, both of which were connected with a syringe pump. This provides controllable conditions for cell inoculation and nutrient supply, and simultaneously simulates the process of ischemic/hypoxic injury and the process of inflammatory factors in the circulatory system passing through the blood-brain barrier and then acting on the nerve tissue in the brain. The in vitro functionalized neurovascular unit model will be conducive to central nervous system disease research, drug screening, and new drug development.

In Vitro Neuroprotective Effects of Macrophage Membrane-Derived Curcumin-Loaded Carriers against 1-Methyl-4-phenylpyridinium-Induced Neuronal Damage.

Curcumin (CUR) possesses neuroprotective effects. However, its clinical therapeutic efficacy is limited because of its low systemic bioavailability due to poor water solubility and fast metabolism. Herein, we designed biomimetic therapeutic nanovesicles (NVs) with enhanced performance and biocompatibility for the intracellular delivery of hydrophobic CUR. Cell membrane NVs were constructed to function as drug carriers by the serial extrusion of macrophages using filters with decreasing pore sizes. Various CUR loading strategies were also evaluated. Furthermore, the neuroprotective effects of the CUR-loaded NVs (NVs-CUR) against 1-methyl-4-phenylpyridinium (MPP+)-induced neuronal degeneration were studied thoroughly. CUR-loaded NVs were readily taken up by neurons in vitro, and the survival rate of MPP+-induced primary neurons increased from 65.37 ± 6.37 to 90.91 ± 3.18% after pretreatment with NVs-CUR. Compared with traditional Parkinson's disease chemotherapeutic treatment, NV formulations can improve the bioavailability of this drug. NVs are expected to become a new and effective drug-delivery platform for further applications in the field of central nervous system therapy.

A Narrow Bandgap of 2D Ruddlesden-Popper Bilayer Perovskite with Giant Entropy Change and Photoluminescence.

The multifunctional two-dimensional (2D) organic-inorganic hybrid perovskites have potential applications in many fields, such as, semiconductor, energy storage and fluorescent device etc. Here, a 2D Ruddlesden-Popper (RP) perovskite (IPA)2 (FA)Pb2 I7 (1, IPA+ =C3 H9 NI+ , FA+ =CN2 H5 + ) is determined for its photophysical properties. Strikingly, 1 reveals a solid reversible phase transition with Tc of 382 K accompanied by giant entropy change of 40 J mol-1 K-1 . Further optical investigations indicate that 1 reveals a narrow direct bandgap (2.024 eV) attributed to the slight bending of I-Pb-I edge and inorganic [Pb2 I7 ]n layer and a superior photoluminescence (PL) emission with super long lifetime of 0.1607 ms. It is believed that this work will pave an avenue to further design multifunctional semiconductors that combines energy storage and photoelectric materials.

High-Temperature and Large-Polarization Ferroelectric with Second Harmonic Generation Response in a Novel Crown Ether Clathrate.

Molecular ferroelectrics of high-temperature reversible phase transitions are very rare and have attracted increasing attention in recent years. In this paper is described the successful synthesis of a novel high-temperature host-guest inclusion ferroelectric: [(C6 H5 NF3 )(18-crown-6)][BF4 ] (1) that shows a pair of reversible peaks at 348 K (heating) and 331 K (cooling) with a heat hysteresis about 17 K by differential scanning calorimetry measurements, thus indicating that 1 undergoes a reversible structural phase transition. Variable-temperature PXRD and temperature-dependent dielectric measurements further prove the phase-transition behavior of 1. The second harmonic response demonstrates that 1 belongs to a non-centrosymmetric space group at room temperature and is a good nonlinear optical material. In its semiconducting properties, 1 shows a wide optical band gap of about 4.43 eV that comes chiefly from the C, H and O atoms of the crystals. In particular, the ferroelectric measurements of 1 exhibit a typical polarization-electric hysteresis loop with a large spontaneous polarization (Ps ) of about 4.06 µC/cm2 . This finding offers an alternative pathway for designing new ferroelectric-dielectric and nonlinear optical materials and related physical properties in organic-inorganic and other hybrid crystals.

Chiral Switchable Low-Dimensional Perovskite Ferroelectrics.

Low-dimensional hybrid organic-inorganic perovskites (HOIPs) possess more localized electronic states and narrower conduction and valence bands to promote self-trapping of excitons and stronger exciton emission; therefore, they are widely used as building blocks for various applications in the fields of optoelectronics, photovoltaics, light-emitting diodes, luminescence, fluorescence, and so forth. Despite the past decades of intensive study, the discovered low-dimensional chiral HOIPs are rare as of the 1D chiral HOIP single crystals reported in 2003, as well as the low-dimensional chiral HOIP ferroelectrics are particularly scarce since the first chiral two-dimensional (2D) and/or one-dimensional (1D) HOIP ferroelectrics reported. Herein, two new low-dimensional HOIPs with the same conformational formula [R-MPA]2CdCl4 (R-MPA+ = (R)-(-)-1-methyl-3-phenylpropylamine) were successfully synthetized by means of regulating the stoichiometric proportion of R-MPA and CdCl2 in two ways of 1:1 (1) and 2:1 (2). By combining single-crystal X-ray diffraction, circular dichroism (CD) spectroscopy, differential scanning calorimetry, temperature-dependent dielectric constant, temperature-dependent second-harmonic generation (SHG) effect, polarization-dependent SHG response, and P-E hysteresis loop, we reveal that 1 is a 1D nonchiral molecular ferroelectric and 2 is the first zero-dimensional (0D) chiral ferroelectric with distinct CD signals; meanwhile, 2 exhibits increased properties of high-Tc, large dielectric constant, SHG isotropy, and ferroelectricity than that of 1. These results not only shed light on the high tunability of the low-dimensional HOIP ferroelectrics but also open up an avenue to explore multifunctional chiral ferroelectrics.

Coupling Narrow Band Gap and Switchable SHG Responses in a New Molecule Ferroelectric: Imidazolyl Propylamine Pentabromo Stibium(III).

Due to the existence of some cross properties such as SHG (second-harmonic generation), ferroelectricity, piezoelectricity, and thermoelectricity, molecular ferroelectrics have been widely used as a composite multipurpose material. Particularly, organic-inorganic molecular ferroelectrics have received much interest recently because of their unique flexible structures, friendly environment, ease of synthesis, etc. Also, these hybrids show great flexibility in band-gap engineering. Here we report a new molecular halide, [C6H13N3SbBr5]n (1; C6H13N3 = 1-(3-aminopropyl)imidazole), which experiences a unique ferroelectric to paraelectric phase transition at around 230 K from space group P21 to P21/c. Significantly, compound 1 exhibits a narrow band gap with a value of 2.52 eV, large pronounced SHG-active, perfect rectangle hysteresis loops with a large spontaneous polarization of 6.86 µC/cm2. DSC (differential scanning calorimetry) and dielectric dependence on temperature tests and the volume change before and after the phase transition show that compound 1 is characterized by a second-order phase transition. These findings will contribute to the multifunctional materials field of organic-inorganic hybrids.

Regulating Reversible Phase Transition Behaviors by Poly-H/F Substitution in Hybrid Perovskite-Like 2[CH2FCH2NH3]·[CdCl4].

The molecular design and regulation has shown bright future for constructing smart molecular materials such as ferroelectrics, dielectric switches, electro-optic effect, and so forth. Here, by poly-H/F substitution in a simple organic-inorganic hybrid 2[CH2FCH2NH3]·[CdCl4], 1 (CH2FCH2NH3 = fluorine ethylamine cation), we obtained two novel hybrids, namely, 2[CHF2CH2NH3]·[CdCl4], 2 (CHF2CH2NH3 = 2,2'-difluorine ethylamine cation) and 2[CF3CH2NH3]·[CdCl4], 3 (CF3CH2NH3 = 2,2',2″-trifluorine ethylamine cation). Further investigations show that compounds 1, 2, and 3 experience solid reversible phase transitions with temperatures at 294, 319, and 329 K respectively. These unique phase transitions were confirmed by their remarkable dielectric and heat anomalies around the phase transition temperatures. X-ray single-crystal diffraction analyses before and after the phase transitions show that the order-disorder motions of F atoms and the twist motions from the 2D [CdCl4]2- framework lead to these solid reversible phase transitions. Also, the Hirshfeld surface calculation of compounds 1, 2, and 3 suggests that the increasing ratio of the F···F interaction from the intermolecular interaction makes a major contribution for the substantial increase of their phase transition temperatures.

Two Rare-Earth Molecular Ferroelectrics with High Curie Temperatures, Large Spontaneous Polarization, Switchable Second Harmonic Generation Effects, and Strong Photoluminescence.

Smart multifunctional molecular ferroelectrics bearing high Curie temperatures and diverse excellent physical properties, such as second harmonic generation (SHG) responses, luminescence, and semiconductivity, among others, have significant applications but have seldom been documented. Herein, the rare-earth metals Nd and Pr are introduced into a simple molecular system (nBu4 N)3 [M(NO3 )x (SCN)y ] (nBu4 N= tetrabutyl ammonium, M=rare-earth metal, nBu=CH3 CH2 CH2 CH2 ), and two new multifunctional molecular ferroelectrics are obtained: (nBu4 N)3 [Nd(NO3 )4 (SCN)2 ] (1) and (nBu4 N)3 [Pr(NO3 )4 (SCN)2 ] (2). Their distinct heat and dielectric anomaly dependence on temperature verifies that compounds 1 and 2 experience high-temperature para-ferroelectric phase transitions at 408 and 413 K, respectively. Strikingly, both molecular ferroelectrics possess large spontaneous polarization with Ps values of 9.05 and 8.50 µC cm-2 , respectively, and are further characterized by the appearance of multiple intersecting non-180° domains and polarization switching behavior. In particular, compounds 1 and 2 show good stability with only a small decrease in SHG intensity after switching cycles, suggesting that they have great potential for application in nonlinear optical (NLO) switches. Simultaneously, the rare-earth compounds 1 and 2 present bright yellow-red and bright green fluorescence, respectively, at room temperature.

Designing and Constructing a High-Temperature Molecular Ferroelectric by Anion and Cation Replacement in a Simple Crown Ether Clathrate.

Molecular ferroelectrics have displayed a promising future since they are light-weight, flexible, environmentally friendly and easily synthesized, compared to traditional inorganic ferroelectrics. However, how to precisely design a molecular ferroelectric from a non-ferroelectric phase transition molecular system is still a great challenge. Here we designed and constructed a molecular ferroelectric by double regulation of the anion and cation in a simple crown ether clathrate, 4, [K(18-crown-6)]+ [PF6 ]- . By replacing K+ and PF6 - with H3 O+ and [FeCl4 ]- respectively, we obtained a new molecular ferroelectric [H3 O(18-crown-6)]+ [FeCl4 ]- , 1. Compound 1 undergoes a para-ferroelectric phase transition near 350 K with symmetry change from P21/n to the Pmc21 space group. X-ray single-crystal diffraction analysis suggests that the phase transition was mainly triggered by the displacement motion of H3 O+ and [FeCl4 ]- ions and twist motion of 18-crown-6 molecule. Strikingly, compound 1 shows high a Curie temperature (350 K), ultra-strong second harmonic generation signals (nearly 8 times of KDP), remarkable dielectric switching effect and large spontaneous polarization. We believe that this research will pave the way to design and build high-quality molecular ferroelectrics as well as their application in smart materials.

A Temperatural Semi-Memorized Phase Transition in a 1D Organic-Inorganic Hybrid Material of Sb|||-Based [(CH2)3NH2S]2SbCl5.

The hybrid organic-inorganic materials have received extraordinary attention from the academic community not only because of their natural chemical tunability but also because of their potential in producing exotic physical properties. However, these characteristics are usually caused by the phase transition of materials under changing of external terms, and it is crucial to fully understand their origins. Here, we research an unusual phase transition near room temperature between two ordered phases in a one-dimensional (1D) hybrid organic-inorganic material of Sb|||-based [(CH2)3NH2S]2SbCl5 (1). This phase transition is caused by collective actions, including the primary variation in the bonds of inorganic five-coordinated tetragonal pyramids, displacement and rotation of organic and inorganic components, along with concurrent hydrogen bonds transformation. Afterward, we observe a significant dielectric anomaly at low frequencies between low and high temperatures. This attributed to the fact that two phases coexist with the lessening temperature, which means that a small number of high-temperature features remained but did not occur during the heating process. These findings offer an avenue for inventing a fresh phase transition and dielectric switch hybrid materials, which further open up the prospect for their practical application.

Mapping theme trends and knowledge structures for human neural stem cells: a quantitative and co-word biclustering analysis for the 2013-2018 period.

Neural stem cells, which are capable of multi-potential differentiation and self-renewal, have recently been shown to have clinical potential for repairing central nervous system tissue damage. However, the theme trends and knowledge structures for human neural stem cells have not yet been studied bibliometrically. In this study, we retrieved 2742 articles from the PubMed database from 2013 to 2018 using "Neural Stem Cells" as the retrieval word. Co-word analysis was conducted to statistically quantify the characteristics and popular themes of human neural stem cell-related studies. Bibliographic data matrices were generated with the Bibliographic Item Co-Occurrence Matrix Builder. We identified 78 high-frequency Medical Subject Heading (MeSH) terms. A visual matrix was built with the repeated bisection method in gCLUTO software. A social network analysis network was generated with Ucinet 6.0 software and GraphPad Prism 5 software. The analyses demonstrated that in the 6-year period, hot topics were clustered into five categories. As suggested by the constructed strategic diagram, studies related to cytology and physiology were well-developed, whereas those related to neural stem cell applications, tissue engineering, metabolism and cell signaling, and neural stem cell pathology and virology remained immature. Neural stem cell therapy for stroke and Parkinson's disease, the genetics of microRNAs and brain neoplasms, as well as neuroprotective agents, Zika virus, Notch receptor, neural crest and embryonic stem cells were identified as emerging hot spots. These undeveloped themes and popular topics are potential points of focus for new studies on human neural stem cells.

Crystal structure of a Y-box binding protein 1 (YB-1)-RNA complex reveals key features and residues interacting with RNA.

The Y-box binding protein 1 (YB-1) is a member of the cold shock domain (CSD) protein family and is recognized as an oncogenic factor in several solid tumors. By binding to RNA, YB-1 participates in several steps of posttranscriptional regulation of gene expression, including mRNA splicing, stability, and translation; microRNA processing; and stress granule assembly. However, the mechanisms in YB-1-mediated regulation of RNAs are unclear. Previously, we used both systematic evolution of ligands by exponential enrichment (SELEX) and individual-nucleotide resolution UV cross-linking and immunoprecipitation coupled RNA-Seq (iCLIP-Seq) analyses, which defined the RNA-binding consensus sequence of YB-1 as CA(U/C)C. We also reported that through binding to its core motif CAUC in primary transcripts, YB-1 regulates the alternative splicing of a CD44 variable exon and the biogenesis of miR-29b-2 during both Drosha and Dicer steps. To elucidate the molecular basis of the YB-1-RNA interactions, we report high-resolution crystal structures of the YB-1 CSD in complex with different RNA oligos at 1.7 Å resolution. The structure revealed that CSD interacts with RNA mainly through π-π stacking interactions assembled by four highly conserved aromatic residues. Interestingly, YB-1 CSD forms a homodimer in solution, and we observed that two residues, Tyr-99 and Asp-105, at the dimer interface are important for YB-1 CSD dimerization. Substituting these two residues with Ala reduced CSD's RNA-binding activity and abrogated the splicing activation of YB-1 targets. The YB-1 CSD-RNA structures presented here at atomic resolution provide mechanistic insights into gene expression regulated by CSD-containing proteins.

Regulating Second-Harmonic Generation by van der Waals Interactions in Two-dimensional Lead Halide Perovskite Nanosheets.

The flexible organic amine cations on the interfaces of two-dimensional (2D) hybrid organic-inorganic perovskite nanosheets could form relaxed structures, which would lead to exotic optoelectronic properties but are hard to understand. Here, the unusual interfacial relaxation of nanosheets exfoliated from an orthorhombic 2D lead halide perovskite, [(C6H5CH2NH3)2]PbCl4, is interrogated via ultrafast second-harmonic generation (SHG) spectroscopy. The in-plane SHG intensity anisotropy of these nanosheets is found to decrease with reducing layer thickness. Combined first-principles calculations and Monte Carlo simulations reveal that the induced second-order polarization arises primarily from the (C6H5CH2NH3)+ cations; and these organic amine cations form significantly reorganized conformations with decreasing nanosheet thickness due to weakened van der Waals interactions. Because the orientations of organic components at the interface determine their electric properties and specifically the dipolar susceptibility, the resulting structure leads to striking changes in the SHG properties.

High-Temperature Reversible Phase-Transition Behavior, Switchable Dielectric and Second Harmonic Generation Response of Two Homochiral Crown Ether Clathrates.

Crowning achievement: Two homochiral crown ether clathrates were synthesized which undergo high-temperature reversible phase transition. In addition, second harmonic generation (SHG) responses and abnormal dielectric property further confirm the reversible phase transitions and symmetry breaking behaviors of the structures.

Dried Rehmannia root protects against glutamate-induced cytotoxity to PC12 cells through energy metabolism-related pathways.

Rehmannia has been shown to be clinically effective in treating neurodegenerative diseases; however, the neuroprotective mechanisms remain unclear. In this study, we established a model of neurodegenerative disease using PC12 cytotoxic injury induced by glutamate. The cells were treated with 20 mM glutamate in the absence or presence of water extracts of dried Rehmannia root of varying concentrations (70%, 50% and 30%). The different concentrations of Rehmannia water extract significantly increased the activity of glutamate-injured cells, reduced the release of lactate dehydrogenase, inhibited apoptosis, increased the concentrations of NADH, NAD and ATP in cells, ameliorated mitochondrial membrane potential, and reduced the levels of light chain 3. Taken together, our findings demonstrate that Rehmannia water extracts exert a cytoprotective effect against glutamate-induced PC12 cell injury via energy metabolism-related pathways.