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1.
J Colloid Interface Sci ; 561: 203-210, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31816465

RESUMO

A three-dimensional free-standing hard carbon (FHC) electrode is synthesized by carbonizing the hemp haulm and employed as anode for sodium-ion batteries directly. A high current charging-discharging process is carried out to reconstruct surface structure of the FHC. Surface reconstructed FHC display a high capacity of 256 mAh/g and enhanced rate ability. With the formation of order surface structure, the plateau capacity increase and more sodium ions can insert into the FHC. This work demonstrates the importance of surface structure for sodium ion diffusion and storage and provide a new strategy to design high-performance anode materials.

2.
J Colloid Interface Sci ; 563: 104-111, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31869581

RESUMO

Herein, we choose the waste walnut shell as the carbon source, and ammonium heptamolybdate as the molybdenum source to prepare the ß-Mo2C catalyst supported on carbon matrix (Mo2C@C) by the calcination method for hydrogen evolution reaction (HER). The open pores in the porous Mo2C nanoparticle clusters can facilitate electrolyte permeation and hydrogen molecules release as well as the carbon matrix can enhance the conductivity. As a result, the optimal Mo2C exhibits an efficient HER performance, with an overpotential of 140 mV at 10 mA cm-2 and a Tafel slope of 63 mV dec-1 as well as excellent electrochemical stability. The strategy changing waste walnut shell into the effective catalysts sets an example for the searching and designing rational energy materials.

3.
ACS Appl Mater Interfaces ; 11(47): 43857-43864, 2019 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-31692325

RESUMO

Graphene (Gr) presents promising applications in regulating the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Light illumination is regarded as a spatiotemporally controllable, easily applicable, and noninvasive mean to modulate material responses. Herein, Gr-transferred silicon (Gr/Si) with a Schottky junction is utilized to evaluate the visible-light-promoted osteogenic differentiation of BMSCs. Under light illumination, light-induced charges, owing to the formation of the Schottky junction at the interface of Gr and Si, accumulated on the surface and then changed the surface potential of Gr/Si. The Schottky junction and surface potential at the interface of Gr and Si was measured by photovoltaic test and scanning Kelvin probe microscopy. Alkaline phosphatase (ALP) activity and quantitative real-time polymerase chain reaction (PCR) measurement showed that such variations of surface improved the osteogenic differentiation of BMSCs, and the activation of the voltage-gated calcium channels through surface potential and accumulation of cytosolic Ca2+ could be the reason. Moreover, X-ray photoelectron spectroscopy characterization showed that surface charge could also affect BMSCs differentiation through the promotion or inhibition of the adsorption of osteogenic growth factors. Such light-promoted osteogenic differentiation of BMSCs on Gr/Si may have huge potential for biomedical materials or devices for bone regeneration application.

4.
Stem Cells ; 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31721356

RESUMO

Mesenchymal stem cells (MSCs), which are undifferentiated stem cells with the property of stemness and the potential to differentiate into multiple lineages, including osteoblasts, have attracted a great deal of attention in bone tissue engineering. Consistent with the heterogeneity of MSCs, various surface markers have been used. However, it is still unclear which markers of MSCs are best for cell amplification in vitro and later bone regeneration in vivo. Krüppel-like Factor 2 (KLF2) is an important indicator of the stemness of human MSCs (hMSCs) and as early vascularization is also critical for bone regeneration, we used KLF2 as a novel in vitro marker for MSCs and investigated the angiogenesis and osteogenesis between KLF2+ MSCs and endothelial cells (ECs). We found a synergistic interaction between hMSCs and human umbilical vein ECs (HUVECs) in that KLF2+ stemness-maintained hMSCs initially promoted the angiogenesis of HUVECs, which in turn more efficiently stimulated the osteogenesis of hMSCs. In fact, KLF2+ hMSCs secreted angiogenic factors initially, with some of the cells then differentiating into pericytes through the PDGF-BB/PDGFR-ß signaling pathway, which improved blood vessel formation. The matured HUVECs in turn synergistically enhanced the osteogenesis of KLF2+ hMSCs through upregulated vascular endothelial growth factor. A three-dimensional coculture model using cell-laden gelatin methacrylate (GelMA) hydrogel further confirmed these results. This study provides insight into the stemness-directed synergistic interaction between hMSCs and HUVECs, and our results will have a profound impact on further strategies involving the application of KLF2+ hMSC/HUVEC-laden GelMA hydrogel in vascular network bioengineering and bone regeneration.

5.
ACS Nano ; 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31747257

RESUMO

Metallic anodes have high theoretical specific capacities and low electrochemical potentials. However, short-circuit problems caused by dendritic deposition and low Coulombic efficiency limit the cyclic life and safety of metallic anode-based batteries. Herein, dendrite-free and flexible three-dimensional (3D) alkali anodes (Li/Na-Ti3C2Tx-rGO) are constructed by infusing molten lithium (Li) or sodium (Na) metal into 3D porous MXene Ti3C2Tx-reduced graphene oxide (Ti3C2Tx-rGO) membranes. First-principles calculations indicate that large fractions of functional groups on the Ti3C2Tx surface lead to the good affinity between the Ti3C2Tx-rGO membrane and molten alkali metal (Li/Na), and the formation of Ti-Li/Na, O-Li/Na, and F-Li/Na mixed covalent/ionic bonds is extremely critical for uniform electrochemical deposition. Furthermore, the porous structure in Li/Na-Ti3C2Tx-rGO composites results in an effective encapsulation, preventing dendritic growth and exhibiting stable stripping/plating behaviors up to 12 mA·cm-2 and a deeper capacity of 10 mA·h·cm-2. Stable cycling performances over 300 h (750 cycles) at 5.0 mA·cm-2 for Li-Ti3C2Tx-rGO and 500 h (750 cycles) at 3.0 mA·cm-2 for Na-Ti3C2Tx-GO are achieved. In a full cell with LiFePO4 cathodes, Li-Ti3C2Tx-rGO electrodes show low polarization and retain 96.6% capacity after 1000 cycles. These findings are based on 2D MXene materials, and the resulting 3D host provides a practical approach for achieving stable and safe alkali metal anodes.

6.
ACS Omega ; 4(21): 19350-19357, 2019 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-31763559

RESUMO

Naringin, a Chinese herbal medicine, has been demonstrated to concentration-dependently promote osteogenic differentiation of mesenchymal stem cells (MSCs). However, it remains a challenge to load naringin on coatings for osteogenesis and further control the release kinetics. Here, we demonstrated that the release behavior of naringin on rutile nanorod films could be controlled by either mixing naringin with gelatin methacryloyl (GelMA) before spinning onto the films or soaking the obtained GelMA-incorporated films with the naringin solution to achieve the distinct degradation-type release and diffusion-type release, respectively. We further revealed that the naringin-loaded coatings facilitated adhesion, proliferation and late differentiation, and mineralization of MSCs. Our findings provided a novel strategy to engineer the coatings with controlled release of naringin and emphasized the bioactivity of naringin for the osteogenic differentiation of MSCs.

7.
J Biomed Inform ; 100: 103302, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31614196

RESUMO

Numerous mobile apps have been developed for making our lives more convenient and improving our quality of life. Health apps are among them. These types of apps are designed to help users for recording their health-related behaviors and to give advice about improving users' physical conditions. However, users frequently do not continue to use these health apps. As a result, the companies of health apps have paid the development cost but cannot get back the benefit from the apps they launch. To find out the reason, this study conducts an empirical investigation and develops a trade-off dual-factor model to dissect the reason why users discontinue use of health apps. The research model is based on the perspectives of information disclosure and expectation-confirmation theory. Users may worry about the disclosure of individual health privacy; however, on the other hand, they enjoy the functions of health apps, proffering various kinds of health-related assistance. The decision of whether or not to continue using this kind of app turns into a trade-off issue. To delve into the determinants, we conduct an online survey and collect 242 qualified responses as our research samples. Structural equation modeling is employed to analyze the samples in this study. The result reveals that our research model explains 31% of the variance. The findings and implications can serve as references for researchers and practitioners.

8.
J Nanobiotechnology ; 17(1): 102, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31581945

RESUMO

Natural extracellular matrices (ECMs) are three-dimensional (3D) and multi-scale hierarchical structure. However, coatings used as ECM-mimicking structures for osteogenesis are typically two-dimensional or single-scaled. Here, we design a distinct quasi-three-dimensional hierarchical topography integrated of density-controlled titania nanodots and nanorods. We find cellular pseudopods preferred to anchor deeply across the distinct 3D topography, dependently of the relative density of nanorods, which promote the osteogenic differentiation of osteoblast but not the viability of fibroblast. The in vivo experimental results further indicate that the new bone formation, the relative bone-implant contact as well as the push-put strength, are significantly enhanced on the 3D hierarchical topography. We also show that the exposures of HFN7.1 and mAb1937 critical functional motifs of fibronectin for cellular anchorage are up-regulated on the 3D hierarchical topography, which might synergistically promote the osteogenesis. Our findings suggest the multi-dimensions and multi-scales as vital characteristic of cell-ECM interactions and as an important design parameter for bone implant coatings.

9.
Biomaterials ; 222: 119456, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31476662

RESUMO

Geometry sensing of cells inevitably involves cytoskeletal remodeling and the activation of biochemical signaling, which control multiple aspects of cell behaviors, such as proliferation, differentiation and migration. A variety of size-, shape- and geometry-dependent cell behaviors have been revealed, but the role of geometric chirality in regulating cellular behaviors and the underlying biophysical mechanisms remain elusive. Here, we report an intriguing mechanotransduction of stem cells on chiral geometries that human mesenchymal stem cells (hMSCs) prefer to migrate towards dextral geometry with nearly 30% relative advantage in migration speed, referred to as "chirotaxis". We also found that cell adhesion, proliferation, and differentiation of hMSCs are greatly enhanced for cells cultured on dextral geometry than those on sinistral geometry, by triggering transcription factor AP-1 complex through p38/MAPK signaling that regulates hMSCs fate and activity. We demonstrated that the cytoskeletal network consisting of transverse and radial stress fibers exhibits a strengthening/offsetting effect on dextral/sinistral geometry through focal adhesion sites, and consequently, cell's cytoskeletal contractility on the dextral geometry is nearly 80% higher. These findings highlight the importance of geometric chirality as an extracellular cue in regulating stem cell's behaviors through cell-material interactions.

10.
Nat Metab ; 1(3): 390-403, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31535081

RESUMO

Amino acid (AA) metabolism is involved in diverse cellular functions, including cell survival and growth, however it remains unclear how it regulates normal hematopoiesis versus leukemogenesis. Here, we report that knockout of Slc1a5 (ASCT2), a transporter of neutral AAs, especially glutamine, results in mild to moderate defects in bone marrow and mature blood cell development under steady state conditions. In contrast, constitutive or induced deletion of Slc1a5 decreases leukemia initiation and maintenance driven by the oncogene MLL-AF9 or Pten deficiency. Survival of leukemic mice is prolonged following Slc1a5 deletion, and pharmacological inhibition of ASCT2 also decreases leukemia development and progression in xenograft models of human acute myeloid leukemia. Mechanistically, loss of ASCT2 generates a global effect on cellular metabolism, disrupts leucine influx and mTOR signaling, and induces apoptosis in leukemic cells. Given the substantial difference in reliance on ASCT2-mediated AA metabolism between normal and malignant blood cells, this in vivo study suggests ASCT2 as a promising therapeutic target for the treatment of leukemia.

11.
Sci Total Environ ; 686: 1140-1151, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31412510

RESUMO

A novel preparation protocol for synthetic, look-a-like humic substances (i.e., fulvic and humic acids) simulating geochemical processes through hydrothermal reaction is presented, with crude waste biomass as an omnipresent and universal precursor. The chemical nature of the organic scaffold and the type and abundance of oxygen-containing functional groups of the synthetic humic substances (A-FA and A-HA) are revealed by a series of examinations. Results from EA, XPS analyze, FTIR spectra and NMR technology matched well each other, suggesting high similarity on chemical structure (abundant aromatic frameworks) and contents (e.g. N and S elements) in both humic acids. Pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS) analysis is employed on the organic structure and is directly compared to extracted natural humic matter from black soils (Harbin, China). Dehydrated carbohydrates and their condensates with low molecular weight that are rich in oxygen are the main structural components of the artificial fulvic acids, while aromatic structures and aliphatic side chains are almost absent. Aromatics (7.43%) and in some cases long-chain aliphatics (7.15%) are more prominent in the A-HA sample. The combination of the diverse analytical techniques not only allows a better understanding of artificial fulvic and humic acids, but also supports the high similarity to natural humic substances in structure and morphology. As the technology can be easily scaled and is comparable cheap, the as obtained products can be discussed to rehabilitate used up farm land.


Assuntos
Benzopiranos/análise , Poluição Ambiental/prevenção & controle , Recuperação e Remediação Ambiental/métodos , Substâncias Húmicas/análise , Eliminação de Resíduos/métodos , Resíduos Sólidos/análise , Biomassa , Solo
12.
J Chromatogr A ; 1606: 460386, 2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31400842

RESUMO

Dihydromyricetin, extracted from Ampelopsis grossedentata, has been widely used as one of Chinese health products in recent years. However, limited chiral separation method hinders the studies of pharmacological and pharmacokinetic activity differences of (+)-dihydromyricetin, (-)-dihydromyricetin, and (±)-dihydromyricetin. Herein, we developed a supercritical fluid chromatography approach for chiral separation of dihydromyricetin. Firstly, effects of chiral stationary phase, co-solvent, and flow rate of mobile phase have been investigated in detail. The resolution of 5.11 was achieved for dihydromyricetin enantiomers on amylose tris(3, 5-dimethylphenylcarbamate)-coated chiral stationary phase with the CO2-methanol mixture (60:40, v/v). With respect to the enantiomeric purity, production rate and solvent consumption of 15 stacked injections, sample loading for semi-preparative separation of dihydromyricetin was optimized in three given equivalents set by volume overloading. Along with increase of sample loading per injection from 40 mg to 120 mg, the productivity of dihydromyricetin increased from 0.07 g (racemate)/g (chiral stationary phase) /24 h to 0.27 g (racemate) /g (chiral stationary phase)/24 h, and the consumption of methanol significantly reduced from 5.86 L/g (racemate) to 1.76 L/g (racemate). Moreover, (-)-dihydromyricetin exhibited better anti-inflammatory activity in TLR 2-related Raw 264.7 cells than (+)-dihydromyricetin and (±)-dihydromyricetin.

13.
ACS Appl Mater Interfaces ; 11(28): 25457-25464, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31282143

RESUMO

A facile strategy is needed for accurate time-space supply of suitable growth factors or drugs. Polypyrrole (PPy) was able to carry almost all kinds of negatively charged biomolecules through anodizing method, which made it an appropriate way for codeposition of multiple molecules. The difference in the conjugation between different molecules and PPy makes it possible for selective release when the redox state of PPy changes. In this work, bovine serum albumin (BSA) and heparin (Hep) were chosen to be the model molecules in view of their differences in the level of electronegativity and molecular weight. Double-layer deposition method was used to improve the biocompatibility of PPy/BSA/Hep film. It was found the content of BSA and Hep in the film can be controlled by regulating deposition current and time. BSA release was facilitated under positive voltage and then promote the proliferation of preosteoblasts, while Hep release was promoted under negative voltage and enhance cell differentiation. Our work provides a dual-molecule model in PPy for selective release and further explores the mechanism of release selectivity, this discovery has potential applications in tissue engineering and regenerative medicine.

14.
Eur J Med Chem ; 179: 233-245, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31255924

RESUMO

A series of S-allyl-l-cysteine (SAC) with garlic acid conjugates as anti-inflammatory agents were designed and synthesized. Among the 40 tested compounds, SMU-8c exhibited the most potent inhibitory activity to Pam3CSK4-induced nitric oxide (NO) in RAW264.7 macrophages with IC50 of 22.54 ±â€¯2.60 µM. The structure-activity relationship (SAR) study suggested that the esterified carboxyl group, carbon chain extension and methoxylation phenol hydroxy could improve the anti-inflammatory efficacy. Preliminary anti-inflammatory mechanism studies showed that SMU-8c significantly down-regulated the levels of Pam3CSK4 triggered TNF-α cytokine in human THP-1 cells, mouse RAW 264.7 macrophages, as well as in ex-vivo human peripheral blood mononuclear cells (PBMC) with no influence on cell viability. SMU-8c specifically blocked the Pam3CSK4 ignited secreted embryonic alkaline phosphatase (SEAP) signaling with no influence to Poly I:C or LPS triggered TLR3 or TLR4 signaling. Moreover, SMU-8c suppressed TLR2 in HEK-Blue hTLR2 cells and inhibited the formation of TLR1-TLR2, and TLR2-TLR6 complex in human PBMC. In summary, SMU-8c inhibited the TLR2 signaling pathway to down-regulate the inflammation cytokines, such as NO, SEAP and TNF-α, to realize its anti-inflammatory activity.


Assuntos
Anti-Inflamatórios não Esteroides/farmacologia , Cisteína/análogos & derivados , Alho/química , Hidroxibenzoatos/farmacologia , Animais , Anti-Inflamatórios não Esteroides/síntese química , Anti-Inflamatórios não Esteroides/química , Cisteína/química , Cisteína/farmacologia , Citocinas/antagonistas & inibidores , Citocinas/metabolismo , Relação Dose-Resposta a Droga , Humanos , Hidroxibenzoatos/química , Lipopeptídeos/antagonistas & inibidores , Lipopeptídeos/farmacologia , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Camundongos , Estrutura Molecular , Óxido Nítrico/antagonistas & inibidores , Óxido Nítrico/biossíntese , Células RAW 264.7 , Relação Estrutura-Atividade , Células THP-1
15.
ACS Appl Mater Interfaces ; 11(25): 22218-22227, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31199127

RESUMO

The surface electric potential of biomaterials has been extensively proven to play a critical role in stem cells' fate. However, there are ambiguous reports on the relation of stem cells' osteogenic capacity to surface potential characteristics (potential polarity and intensity). To address this, we adopted a surface with a wide potential range and both positive/negative polarity in a comprehensive view to get insight into surface potential-regulating cellular osteogenic differentiation. Tb xDy1- xFe2 alloy/poly(vinylidene fluoride-trifluoroethylene) magnetoelectric films were prepared, and the film could provide controllable surface potential characteristics with positive or negative polarity and potential (ϕME) intensity variation from 0 to ±120 mV as well as keep the surface chemical composition and microstructure unchanged. Cell culture results showed that osteogenic differentiation of mesenchymal stem cells on both positive and negative potential films was obviously upregulated when the /ϕME/ intensities were set from 0-55 mV. Differently, the highest upregulated osteogenic differentiation on the positive potential films corresponded to the /ϕME/ intensity from 35-55 mV and was better than that on the negative potential films whereas the highest on the negative potential films corresponded to the /ϕME/ intensity from 0-35 mV and was better than that on the positive potential films. This fact could illustrate why previous reports appeared ambiguously; i.e., the comparative result in osteogenic differentiation between the positive and negative potential films strongly depends on the selection of surface potential intensity. On the basis of assaying of the exposed functional sites (RGD and PHSRN) of the adsorbed fibronectin (FN) and the expression of cellular integrin α5 and ß1 subunits, the difference in the behavior between the positive and negative potential films was attributed to the distinct conformation of adsorbed fibronectin (FN) and the opposite changing trend with /ϕME/ for the two films, which triggers the osteogenesis-related FAK/ERK signaling pathway to a different extent. This study could provide new cognition for the in-depth understanding of the regulation mechanism underlying surface potential characteristics in cell behaviors.

16.
J Mol Cell Cardiol ; 132: 120-135, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31082397

RESUMO

Immature phenotypes of cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) limit the utility of these cells in clinical application and basic research. During cardiac development, postnatal cardiomyocytes experience high oxygen tension along with a concomitant downregulation of hypoxia-inducible factor 1α (HIF-1α), leading to increased fatty acid oxidation (FAO). We hypothesized that targeting HIF-1α alone or in combination with other metabolic regulators could promote the metabolic maturation of hiPSC-CMs. We examined the effect of HIF-1α inhibition on the maturation of hiPSC-CMs and investigated a multipronged approach to promote hiPSC-CM maturation by combining HIF-1α inhibition with molecules that target key pathways involved in the energy metabolism. Cardiac spheres of highly-enriched hiPSC-CMs were treated with a HIF-1α inhibitor alone or in combination with an agonist of peroxisome proliferator activated receptor α (PPARα) and three postnatal factors (triiodothyronine hormone T3, insulin-like growth factor-1 and dexamethasone). HIF-1α inhibition significantly increased FAO and basal and maximal respiration of hiPSC-CMs. Combining HIF-1α inhibition with PPARα activation and the postnatal factors further increased FAO and improved mitochondrial maturation in hiPSC-CMs. Compared with mock-treated cultures, the cultures treated with the five factors had increased mitochondrial content and contained more cells with mitochondrial distribution throughout the cells, which are features of more mature cardiomyocytes. Consistent with these observations, a number of transcriptional regulators of mitochondrial metabolic processes were upregulated in hiPSC-CMs treated with the five factors. Furthermore, these cells had significantly increased Ca2+ transient kinetics and contraction and relaxation velocities, which are functional features for more mature cardiomyocytes. Therefore, targeting HIF-1α in combination with other metabolic regulators significantly improves the metabolic maturation of hiPSC-CMs.

17.
Adv Sci (Weinh) ; 6(10): 1802042, 2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-31131189

RESUMO

Toll-like receptor 2 (TLR2) expressed on antigen presenting cells evokes a series of critical cytokines, which favor the development of tumor-specific cytotoxic T lymphocytes (CTLs). Therefore, TLR2 represents an attractive cancer immunotherapeutic target. Here, a synthetic library of 14 000 compounds together with a series of newly developed compounds for NF-κB activation using HEK-Blue hTLR2 cells is initially screened. Following further screening in a variety of cells including HEK-Blue hTLRs reporter cells, murine, and human macrophage cell lines, a potent small molecule agonist 23 (SMU-Z1) is identified, which specifically activates TLR2 through its association with TLR1, with a EC50 of 4.88 ± 0.79 × 10-9 m. Toxicology studies, proinflammatory cytokines (e.g., TNF-α, IL-1ß, IL-6, and nitric oxide) and target-protein based biophysical assays demonstrate the pharmacologically relevant characteristics of SMU-Z1. In addition, SMU-Z1 promotes murine splenocyte proliferation and upregulates the expression of CD8+ T cells, NK cells and DCs, which results in a significant antitumor effect in a murine leukemia model. Finally, the induced tumors in three out of seven mice disappear after administration of SMU-Z1. Our studies thus identify a novel and potent TLR1/2 small molecule agonist, which displays promising immune adjuvant properties and antitumor immunity.

19.
Nanoscale ; 11(17): 8219-8225, 2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-30973564

RESUMO

With the development of portable electronic devices, highly efficient thermal management has become an important design consideration which requires good flexibility and excellent thermal conductivity. In this work, an integrated "modified-welding" method is used to deliver a flexible film with superior thermal conductivity. Firstly, graphene oxide (GO) is modified by 4,4'-diaminodiphenyl ether (ODA) through covalent bonding, aiming at providing reactive sites by polyimide (PI) on GO sheets for further in situ "modified-welding". The intercalated PI in mGO film layers serves as the solder to weld adjacent graphene sheets into large ones with less grain boundaries, leading to a superior in-plane thermal conductivity of the graphitized graphene/polyimide composite film (g-mGO/PI) which reaches 1352 ± 5 W m-1 K-1, 92.3% higher than that of the pristine graphitized graphene film (g-GO). Additionally, the g-mGO/PI film survives a 2000-cycle anti-bending test, which demonstrates excellent flexibility. Last but not least, the "modified-welding" strategy also provides an innovative way to develop graphene-based films for thermal management.

20.
Cell Stem Cell ; 24(4): 608-620.e6, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30880025

RESUMO

Hematopoietic stem cell (HSC) quiescence is a tightly regulated process crucial for hematopoietic regeneration, which requires a healthy and supportive microenvironmental niche within the bone marrow (BM). Here, we show that deletion of Ptpn21, a protein tyrosine phosphatase highly expressed in HSCs, induces stem cell egress from the niche due to impaired retention within the BM. Ptpn21-/- HSCs exhibit enhanced mobility, decreased quiescence, increased apoptosis, and defective reconstitution capacity. Ptpn21 deletion also decreased HSC stiffness and increased physical deformability, in part by dephosphorylating Spetin1 (Tyr246), a poorly described component of the cytoskeleton. Elevated phosphorylation of Spetin1 in Ptpn21-/- cells impaired cytoskeletal remodeling, contributed to cortical instability, and decreased cell rigidity. Collectively, these findings show that Ptpn21 maintains cellular mechanics, which is correlated with its important functions in HSC niche retention and preservation of hematopoietic regeneration capacity.

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