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1.
Cell ; 162(3): 648-61, 2015 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-26232230

RESUMO

We describe automated technologies to probe the structure of neural tissue at nanometer resolution and use them to generate a saturated reconstruction of a sub-volume of mouse neocortex in which all cellular objects (axons, dendrites, and glia) and many sub-cellular components (synapses, synaptic vesicles, spines, spine apparati, postsynaptic densities, and mitochondria) are rendered and itemized in a database. We explore these data to study physical properties of brain tissue. For example, by tracing the trajectories of all excitatory axons and noting their juxtapositions, both synaptic and non-synaptic, with every dendritic spine we refute the idea that physical proximity is sufficient to predict synaptic connectivity (the so-called Peters' rule). This online minable database provides general access to the intrinsic complexity of the neocortex and enables further data-driven inquiries.


Assuntos
Microscopia Eletrônica de Varredura/métodos , Microtomia/métodos , Neocórtex/ultraestrutura , Neurônios/ultraestrutura , Animais , Automação , Axônios/ultraestrutura , Dendritos/ultraestrutura , Camundongos , Neocórtex/citologia , Sinapses/ultraestrutura , Vesículas Sinápticas/ultraestrutura
2.
Chemistry ; 30(13): e202303755, 2024 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-38149882

RESUMO

A structurally precise hydride-containing Pt-doped Cu-rich nanocluster [PtH2 Cu14 {S2 P(Oi Pr)2 }6 (CCPh)6 ] (1) has been synthesized. It consists of a bicapped icosahedral Cu14 cage that encapsulates a linear PtH2 unit. Upon the addition of two equivalents of CF3 COOH to 1, two hydrido clusters are isolated. These clusters are [PtHCu11 {S2 P(Oi Pr)2 }6 (CCPh)4 ] (2), which is a vertex-missing Cu11 cuboctahedron encaging a PtH moiety, and [PtH2 Cu11 {S2 P(Oi Pr)2 }6 (CCPh)3 ] (3), a distorted 3,3,4,4,4-pentacapped trigonal prismatic Cu11 cage enclosing a PtH2 unit. The electronic structure of 2, analyzed by Density Functional Theory, is a 2e superatom. The electrocatalytic activities of 1-3 for hydrogen evolution reaction (HER) were compared. Notably, Cluster 2 exhibited an exceptionally excellent HER activity within metal nanoclusters, with an onset potential of -0.03 V (at 10 mA cm-2 ), a Tafel slope of 39 mV dec-1 , and consistent HER activity throughout 3000 cycles in 0.5 M H2 SO4 . Our study suggests that the accessible central Pt site plays a crucial role in the remarkable HER activity and may provide valuable insights for establishing correlations between catalyst structure and HER activity.

3.
Angew Chem Int Ed Engl ; : e202404387, 2024 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-38757232

RESUMO

The electrochemical CO2 reduction reaction (CO2RR) has been widely studied as a promising means to convert anthropogenic CO2 into valuable chemicals and fuels. In this process, the alkali metal ions present in the electrolyte are known to significantly influence the CO2RR activity and selectivity. In this study, we report a strategy for preparing efficient electrocatalysts by introducing a cation-relaying ligand, namely 6-mercaptohexanoic acid (MHA), into atom-precise Au25 nanoclusters (NCs). The CO2RR activity of the synthesized Au25(MHA)18 NCs was compared with that of Au25(HT)18 NCs (HT=1-hexanethiolate). While both NCs selectively produced CO over H2, the CO2-to-CO conversion activity of the Au25(MHA)18 NCs was significantly higher than that of the Au25(HT)18 NCs when the catholyte pH was higher than the pKa of MHA, demonstrating the cation-relaying effect of the anionic terminal group. Mechanistic investigations into the CO2RR occurring on the Au25 NCs in the presence of different catholyte cations and concentrations revealed that the CO2-to-CO conversion activities of these Au25 NCs increased in the order Li+

4.
J Am Chem Soc ; 145(4): 2152-2160, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36657026

RESUMO

Electrocatalytic CO2 reduction reaction (CO2RR) is greatly facilitated by Au surfaces. However, large fractions of underlying Au atoms are generally unused during the catalytic reaction, which limits mass activity. Herein, we report a strategy for preparing efficient electrocatalysts with high mass activities by the atomic-level transplantation of Au active sites into a Ni4 nanocluster (NC). While the Ni4 NC exclusively produces H2, the Au-transplanted NC selectively produces CO over H2. The origin of the contrasting selectivity observed for this NC is investigated by combining operando and theoretical studies, which reveal that while the Ni sites are almost completely blocked by the CO intermediate in both NCs, the Au sites act as active sites for CO2-to-CO electroreduction. The Au-transplanted NC exhibits a remarkable turnover frequency and mass activity for CO production (206 molCO/molNC/s and 25,228 A/gAu, respectively, at an overpotential of 0.32 V) and high durability toward the CO2RR over 25 h.

5.
Angew Chem Int Ed Engl ; 62(33): e202302591, 2023 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-37117156

RESUMO

We report a new strategy in which a thiolate-protected Ag25 nanocluster can be doped with open d-shell group 8 (Ru, Os) and 9 (Ir) metals by forming metal hydride (RuH2 , OsH2 , IrH) superatoms with a closed d-shell. Structural analyses using various experimental and theoretical methods revealed that the Ag25 nanoclusters were co-doped with the open d-shell metal and hydride species to produce superatom-in-superatom nanoclusters, establishing a novel superatom doping phenomenon for open d-shell metals. The synthesized superatom-in-superatom nanoclusters exhibited dopant-dependent photoluminescence (PL) properties. Comparative PL lifetime studies of the Ag25 nanoclusters doped with 8-10 group metals revealed that both radiative and nonradiative processes were significantly dependent on the dopant. The former is strongly correlated with the electron affinity of the metal dopant, whereas the latter is governed predominantly by the kernel structure changed upon the doping of the metal hydride(s).

6.
Angew Chem Int Ed Engl ; 62(16): e202301272, 2023 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-36807455

RESUMO

The first hydride-containing 2-electron palladium/copper alloys, [PdHCu11 {S2 P(Oi Pr)2 }6 (C≡CPh)4 ] (PdHCu11 ) and [PdHCu12 {S2 P(Oi Pr)2 }5 {S2 PO(Oi Pr)} (C≡CPh)4 ] (PdHCu12 ), are synthesized from the reaction of [PdH2 Cu14 {S2 P(Oi Pr)2 }6 (C≡CPh)6 ] (PdH2 Cu14 ) with trifluoroacetic acid (TFA). X-ray diffraction reveals that the PdHCu11 and PdHCu12 kernels consist of a central PdH unit encapsulated within a vertex-missing Cu11 cuboctahedron and complete Cu12 cuboctahedron, respectively. DFT calculations indicate that both PdHCu11 and PdHCu12 can be considered as axially-distorted 2-electron superatoms. PdHCu11 shows excellent HER activity, unprecedented within metal nanoclusters, with an onset potential of -0.05 V (at 10 mA cm-2 ), a Tafel slope of 40 mV dec-1 , and consistent HER activity during 1000 cycles in 0.5 M H2 SO4 . Our study suggests that the accessible central Pd site is the key to HER activity and may provide guidelines for correlating catalyst structures and HER activity.

7.
Small ; 17(27): e2004836, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33559347

RESUMO

The development of efficient light-harvesting systems is important to understand the key aspects of solar-energy conversion processes and to utilize them in various photonic applications. Here, atomically well-defined gold nanoclusters are reported as a new platform to fabricate artificial light-harvesting systems. An efficient amide coupling method is developed to synthesize water-soluble Au22 clusters fully protected with pyrene chromophores by taking advantage of their facile phase-transfer reaction. The synthesized Au22 clusters with densely packed 18 pyrene chromophores (Au22 -PyB18 ) exhibit triple-emission in blue, green, and red wavelength regions arising respectively from pyrene monomer, pyrene excimer, and Au22 emission, producing bright white light emission together. The photoluminescence of Au22 is enhanced by more than tenfold, demonstrating that pyrenes at the periphery efficiently channel the absorbed energy to the luminescent Au22 at the center. A combination of femtosecond transient absorption and anisotropy measurements of Au22 -PyB18 explicitly reveals three main decay components of 220 fs, 3.5 ps, and 160 ps that can be assigned to energy migration between pyrenes and energy transfer processes from pyrene monomer and excimer to the central Au22 , respectively.


Assuntos
Ouro , Luminescência , Anisotropia , Transferência de Energia
8.
J Chem Phys ; 155(1): 014305, 2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34241411

RESUMO

Syngas, a gaseous mixture of CO and H2, is a critical industrial feedstock for producing bulk chemicals and synthetic fuels, and its production via direct CO2 electroreduction in aqueous media constitutes an important step toward carbon-negative technologies. Herein, we report controlled syngas production with various H2/CO ratios via the electrochemical CO2 reduction reaction (CO2RR) on specifically formulated Au25 and PtAu24 nanoclusters (NCs) with core-atom-controlled selectivities. While CO was predominantly produced from the CO2RR on the Au NCs, H2 production was favored on the PtAu24 NCs. Density functional theory calculations of the free energy profiles for the CO2RR and hydrogen evolution reaction (HER) indicated that the reaction energy for the conversion of CO2 to CO was much lower than that for the HER on the Au25 NC. In contrast, the energy profiles calculated for the HER indicated that the PtAu24 NCs have nearly thermoneutral binding properties; thus, H2 production is favored over CO formation. Based on the distinctly different catalytic selectivities of Au25 and PtAu24 NCs, controlled syngas production with H2/CO ratios of 1 to 4 was demonstrated at a constant applied potential by simply mixing the Au25 and PtAu24 NCs based on their intrinsic catalytic activities for the production of CO and H2.

9.
Angew Chem Int Ed Engl ; 60(41): 22293-22300, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34224193

RESUMO

Heterometal doping is a powerful method for tuning the physicochemical properties of metal nanoclusters. While the heterometals doped into such nanoclusters predominantly include transition metals with closed d-shells, the doping of open d-shell metals remains largely unexplored. Herein, we report the first synthesis of a [RhHAg24 (SPhMe2 )18 ]2- nanocluster, in which a Rh atom with open d-shells ([Kr]4d8 5s1 ) is incorporated into the Ag24 framework by forming a RhH superatom with closed d-shells ([Kr]4d10 ). Combined experimental and theoretical investigations showed that the Ag24 framework was co-doped with Rh and hydride and that the RhH dopant was a superatomic construct of a Pd atom. Additional studies demonstrated that the [RhHAg24 (SPhMe2 )18 ]2- nanocluster was isoelectronic to the [PdAg24 (SPhMe2 )18 ]2- nanocluster with the superatomic 8-electron configuration (1S2 1P6 ). This study demonstrated for the first time that a superatom could be incorporated into a cluster superatom to generate a stable superatom-in-superatom nanocluster.

10.
Angew Chem Int Ed Engl ; 60(26): 14563-14570, 2021 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-33877721

RESUMO

Accurate identification of active sites is critical for elucidating catalytic reaction mechanisms and developing highly efficient and selective electrocatalysts. Herein, we report the atomic-level identification of active sites using atomically well-defined gold nanoclusters (Au NCs) Au25 , Au38 , and Au144 as model catalysts in the electrochemical CO2 reduction reaction (CO2 RR). The studied Au NCs exhibited remarkably high CO2 RR activity, which increased with increasing NC size. Electrochemical and X-ray photoelectron spectroscopy analyses revealed that the Au NCs were activated by removing one thiolate group from each staple motif at the beginning of CO2 RR. In addition, density functional theory calculations revealed higher charge densities and upshifts of d-states for dethiolated Au sites. The structure-activity properties of the studied Au NCs confirmed that dethiolated Au sites were the active sites and that CO2 RR activity was determined by the number of active sites on the cluster surface.

11.
Acc Chem Res ; 52(1): 12-22, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30500153

RESUMO

Thiolate-protected metal nanoparticles containing a few to few hundred metal atoms are interesting materials exhibiting unique physicochemical properties. They encompass the bulk-to-molecule transition region, where discrete electronic states emerge and electronic band energetics yield to quantum confinement effects. Recent progresses in the synthesis and characterization of ultrasmall gold nanoparticles have opened up new avenues for the isolation of extremely monodispersed nanoparticles with atomically precision. These nanoparticles are also called nanoclusters to distinguish them from other regular metal nanoparticles with core diameter >2 nm. These nanoclusters are typically identified by their actual molecular formulas; prominent among these are Au25(SR)18, Au38(SR)24, and Au102(SR)44, where SR is organothiolate. A number of single crystal structures of these nanoclusters have been disclosed. Researchers have effectively utilized density functional theory (DFT) calculations to predict their atomic and electronic structures, as well as their physicochemical properties. The atomically precise metal nanoclusters have been the focus of recent studies owing to their novel size-specific electrochemical, optical, and catalytic properties. In this Account, we highlight recent advances in electrochemistry of atomically precise metal nanoclusters and their applications in electrocatalysis and electrochemical sensing. Compared with gold nanoclusters, much less progress has been made in the electrochemical studies of other metal nanoclusters, and thus, we mainly focus on the electrochemistry and electrochemical applications of gold-based nanoclusters. Voltammetry has been extremely powerful in investigating the electronic structure of metal nanoclusters, especially near HOMO and LUMO levels. A sizable opening of HOMO-LUMO gap observed for Au25(SR)18 gradually decreases with increasing nanocluster size, which is in line with the change in the optical gap. Heteroatom-doping has been a powerful strategy to modify the optical and electrochemical properties of metal nanoclusters at the atomic level. While the superatom theory predicts 8-electron configuration for [Au25(SR)18]- and many doped nanoclusters thereof, Pt- and Pd-doped [PtAu24(SR)18]0 and [PdAu24(SR)18]0 nanoclusters show dramatically different electronic structures, as manifested in their optical spectra and voltammograms, suggesting the occurrence of the Jahn-Teller distortion in these doped nanoclusters. Furthermore, metal-doping may alter their surface binding properties, as well as redox potentials. Metal nanoclusters offer great potential for attaining high activity and selectivity in their electrocatalytic applications. The well-defined core-shell structure of a metal nanocluster is of special advantage because the core and shell can be independently engineered to exhibit suitable binding properties and redox potentials. We discuss recent progress made in electrocatalysis based upon metal nanoclusters tailored for water splitting, CO2 conversion, and electrochemical sensing. A well-defined model nanocatalyst is absolutely necessary to reveal the detailed mechanism of electrocatalysis and thereby to lead to the development of a new efficient electrocatalyst. We envision that atomically controlled metal nanoclusters will enable us to systematically optimize the electrochemical and surface properties suitable for electrocatalysis, thus providing a powerful platform for the discovery of finely tuned nanocatalysts.

12.
J Am Chem Soc ; 139(28): 9728-9736, 2017 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-28640611

RESUMO

Copper electrocatalysts can reduce CO2 to hydrocarbons at high overpotentials. However, a mechanistic understanding of CO2 reduction on nanostructured Cu catalysts has been lacking. Herein we show that the structurally precise ligand-protected Cu-hydride nanoclusters, such as Cu32H20L12 (L is a dithiophosphate ligand), offer unique selectivity for electrocatalytic CO2 reduction at low overpotentials. Our density functional theory (DFT) calculations predict that the presence of the negatively charged hydrides in the copper cluster plays a critical role in determining the selectivity of the reduction product, yielding HCOOH over CO with a lower overpotential. The HCOOH formation proceeds via the lattice-hydride mechanism: first, surface hydrides reduce CO2 to HCOOH product, and then the hydride vacancies are readily regenerated by the electrochemical proton reduction. DFT calculations further predict that hydrogen evolution is less competitive than HCOOH formation at the low overpotential. Confirming the predictions, electrochemical tests of CO2 reduction on the Cu32H20L12 cluster demonstrate that HCOOH is indeed the main product at low overpotential, while H2 production dominates at higher overpotential. The unique selectivity afforded by the lattice-hydride mechanism opens the door for further fundamental and applied studies of electrocatalytic CO2 reduction by copper-hydride nanoclusters and other metal nanoclusters that contain hydrides.

13.
Pacing Clin Electrophysiol ; 40(2): 162-174, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28000227

RESUMO

BACKGROUND: The role of J-waves in the pathogenesis of ventricular fibrillation (VF) occurring in structurally normal hearts is important. METHODS: We evaluated 127 patients who received an implantable cardioverter-defibrillator (ICD) for Brugada syndrome (BS, n = 53), early repolarization syndrome (ERS, n = 24), and patients with unknown or deferred diagnosis (n = 50). Electrocardiography (ECG), clinical characteristics, and ICD data were analyzed. RESULTS: J-waves were found in 27/50 patients with VF of unknown/deferred diagnosis. The J-waves were reminiscent of those seen in BS or ERS, and this subgroup of patients was termed variants of ERS and BS (VEB). In 12 VEB patients, the J/ST/T-wave morphology was coved, although amplitudes were <0.2 mV. In 15 patients, noncoved-type J/ST/T-waves were present in the right precordial leads. In the remaining 23 patients, no J-waves were identified. VEB patients exhibited clinical characteristics similar to those of BS and ERS patients. Phenotypic transition and overlap were observed among patients with BS, ERS, and VEB. Twelve patients with BS had background inferolateral ER, while five ERS patients showed prominent right precordial J-waves. Patients with this transient phenotype overlap showed a significantly lower shock-free survival than the rest of the study patients. CONCLUSIONS: VEB patients demonstrate ECG phenotype similar to but distinct from those of BS and ERS. The spectral nature of J-wave morphology/distribution and phenotypic transition/overlap suggest a common pathophysiologic background in patients with VEB, BS, and ERS. Prognostic implication of these ECG variations requires further investigation.


Assuntos
Síndrome de Brugada/classificação , Síndrome de Brugada/diagnóstico , Eletrocardiografia/métodos , Infarto do Miocárdio com Supradesnível do Segmento ST/classificação , Infarto do Miocárdio com Supradesnível do Segmento ST/diagnóstico , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
14.
Nano Lett ; 16(3): 1840-7, 2016 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-26885948

RESUMO

A vertically integrated junctionless field-effect transistor (VJ-FET), which is composed of vertically stacked multiple silicon nanowires (SiNWs) with a gate-all-around (GAA) structure, is demonstrated on a bulk silicon wafer for the first time. The proposed VJ-FET mitigates the issues of variability and fabrication complexity that are encountered in the vertically integrated multi-NW FET (VM-FET) based on an identical structure in which the VM-FET, as recently reported, harnesses a source and drain (S/D) junction for its operation and is thus based on the inversion mode. Variability is alleviated by bulk conduction in a junctionless FET (JL-FET), where current flows through the core of the SiNW, whereas it is not mitigated by surface conduction in an inversion mode FET (IM-FET), where current flows via the surface of the SiNW. The fabrication complexity is reduced by the inherent JL structure of the JL-FET because S/D formation is not required. In contrast, it is very difficult to dope the S/D when it is positioned at each floor of a tall SiNW with greater uniformity and with less damage to the crystalline structure of the SiNW in a VM-FET. Moreover, when the proposed VJ-FET is used as nonvolatile flash memory, the endurance and retention characteristics are improved due to the above-mentioned bulk conduction.

15.
Nano Lett ; 15(12): 8056-61, 2015 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-26544156

RESUMO

A vertically integrated multiple channel-based field-effect transistor (FET) with the highest number of nanowires reported ever is demonstrated on a bulk silicon substrate without use of wet etching. The driving current is increased by 5-fold due to the inherent vertically stacked five-level nanowires, thus showing good feasibility of three-dimensional integration-based high performance transistor. The developed fabrication process, which is simple and reproducible, is used to create multiple stiction-free and uniformly sized nanowires with the aid of the one-route all-dry etching process (ORADEP). Furthermore, the proposed FET is revamped to create nonvolatile memory with the adoption of a charge trapping layer for enhanced practicality. Thus, this research suggests an ultimate design for the end-of-the-roadmap devices to overcome the limits of scaling.

16.
J Am Chem Soc ; 137(33): 10833-40, 2015 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-26222199

RESUMO

The exceptional stability of thiolate-protected Au25 clusters, [Au25(SR)18](-), arises from the closure of superatomic electron shells, leading to a noble-gas-like 8-electron configuration (1S(2)1P(6)). Here we present that replacing the core Au atom with Pd or Pt results in stable [MAu24(SR)18](0) clusters (M = Pd, Pt) having a superatomic 6-electron configuration (1S(2)1P(4)). Voltammetric studies of [PdAu24(SR)18](0) and [PtAu24(SR)18](0) reveal that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of these clusters are 0.32 and 0.29 eV, respectively, indicating their electronic structures are drastically altered upon doping of the foreign metal. Density functional investigations confirm that the HOMO-LUMO gaps of these clusters are indeed smaller, respectively 0.33 and 0.32 eV, than that of [Au25(SR)18](-) (1.35 eV). Analysis of the optimized geometries for the 6-electron [MAu24(SR)18](0) clusters shows that the MAu12 core is slightly flattened to yield an oblate ellipsoid. The drastically decreased HOMO-LUMO gaps observed are therefore the result of Jahn-Teller-like distortion of the 6-electron [MAu24(SR)18](0) clusters, accompanying splitting of the 1P orbitals. These clusters become 8-electron [MAu24(SR)18](2-) clusters upon electronic charging, demonstrating reversible interconversion between the 6-electron and 8-electron configurations of MAu24(SR)18.

17.
J Am Chem Soc ; 137(25): 8244-50, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-26061198

RESUMO

Luminescent nanomaterials have captured the imagination of scientists for a long time and offer great promise for applications in organic/inorganic light-emitting displays, optoelectronics, optical sensors, biomedical imaging, and diagnostics. Atomically precise gold clusters with well-defined core-shell structures present bright prospects to achieve high photoluminescence efficiencies. In this study, gold clusters with a luminescence quantum yield greater than 60% were synthesized based on the Au22(SG)18 cluster, where SG is glutathione, by rigidifying its gold shell with tetraoctylammonium (TOA) cations. Time-resolved and temperature-dependent optical measurements on Au22(SG)18 have shown the presence of high quantum yield visible luminescence below freezing, indicating that shell rigidity enhances the luminescence quantum efficiency. To achieve high rigidity of the gold shell, Au22(SG)18 was bound to bulky TOA that resulted in greater than 60% quantum yield luminescence at room temperature. Optical measurements have confirmed that the rigidity of gold shell was responsible for the luminescence enhancement. This work presents an effective strategy to enhance the photoluminescence efficiencies of gold clusters by rigidifying the Au(I)-thiolate shell.


Assuntos
Ouro/química , Substâncias Luminescentes/química , Nanopartículas Metálicas/química , Compostos de Sulfidrila/química , Cátions/química , Glutationa/química , Luminescência , Modelos Moleculares , Compostos de Amônio Quaternário/química
18.
Phytother Res ; 29(6): 870-6, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25808759

RESUMO

This study examined the inhibitory effect of forsythiaside-A, a natural substance derived from Forsythia suspensa (F. suspensa), on entry into catagen induced by dihydrotestosterone (DHT) in an androgenic alopecia mouse model. In vitro experiment comparing finasteride with forsythiaside-A showed that forsythiaside-A treatment resulted in a 30% greater inhibition of DHT-induced apoptosis in human hair dermal papilla cell (HHDPCs) and human keratinocytes (HaCaTs). In vivo experiment showed that mouse hair density and thickness were increased by 50% and 30%, respectively, in the forsythiaside-A-treated group when compared to a DHT group. Tissue histological results revealed that the forsythiaside-A-treated group had an increase in size and shape of the hair follicles and a 1.5 times increase in the follicle anagen/telogen ratio when compared to the finasteride group. Western blot examination of TGF-ß2 expression related to apoptosis signaling in mouse skin verified that forsythiaside-A reduced the expression of TGF-ß2 by 75% and suppressed apoptosis by reducing the expression of caspase-9 by 40%, and caspase-3 by 53%, which play an roles up-regulator in the apoptosis signal. The forsythiaside-A group also showed a 60% increase in the Bcl-2/Bax ratio, which is a factor related to mitochondrial apoptosis. Our results indicated that forsythiaside-A prevents apoptosis by similar mechanism with finasteride, but forsythiaside-A is more effective than finasteride. In summary, forsythiaside-A controlled the apoptosis of hair cells and retarded the entry into the catagen phase and therefore represents a natural product with much potential for use as a treatment for androgenic alopecia.


Assuntos
Alopecia/tratamento farmacológico , Forsythia/química , Glicosídeos/farmacologia , Folículo Piloso/efeitos dos fármacos , Queratinócitos/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Caspase 3/metabolismo , Caspase 9/metabolismo , Células Cultivadas , Modelos Animais de Doenças , Folículo Piloso/citologia , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fator de Crescimento Transformador beta2/metabolismo
19.
Small ; 10(19): 3887-94, 2014 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-24912667

RESUMO

Triboelectric nanogenerators with nature-replicated interface structures are presented. Effective contact areas of the triboelectric surfaces are largely enhanced because of the densely packed nano-in-micro hierarchical structures in nature. The enlarged contact area causes stronger triboelectric charge density, which results in output power increment. The interface engineering also allows the improved humidity resistance, which is an important parameter for the stable energy harvesting.


Assuntos
Materiais Biomiméticos , Fontes de Energia Elétrica , Nanotecnologia , Animais , Dimetilpolisiloxanos/química , Eletroquímica , Eletrodos , Desenho de Equipamento , Hemípteros , Humanos , Umidade , Microscopia Eletrônica de Varredura , Oscilometria , Folhas de Planta/metabolismo , Polímeros/química , Propriedades de Superfície , Temperatura , Asas de Animais/patologia
20.
Biol Pharm Bull ; 37(5): 755-63, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24789999

RESUMO

This study was conducted to test whether ginsenoside F2 can reduce hair loss by influencing sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP) and the transforming growth factor beta (TGF-ß) pathway of apoptosis in dihydrotestosterone (DHT)-treated hair cells and in a DHT-induced hair loss model in mice. Results for ginsenoside F2 were compared with finasteride. DHT inhibits proliferation of hair cells and induces androgenetic alopecia and was shown to activate an apoptosis signal pathway both in vitro and in vivo. The cell-based 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that the proliferation rates of DHT-treated human hair dermal papilla cells (HHDPCs) and HaCaTs increased by 48% in the ginsenoside F2-treated group and by 12% in the finasteride-treated group. Western blot analysis showed that ginsenoside F2 decreased expression of TGF-ß2 related factors involved in hair loss. The present study suggested a hair loss related pathway by changing SCAP related apoptosis pathway, which has been known to control cholesterol metabolism. SCAP, sterol regulatory element-binding protein (SREBP) and caspase-12 expression in the ginsenoside F2-treated group were decreased compared to the DHT and finasteride-treated group. C57BL/6 mice were also prepared by injection with DHT and then treated with ginsenoside F2 or finasteride. Hair growth rate, density, thickness measurements and tissue histotological analysis in these groups suggested that ginsenoside F2 suppressed hair cell apoptosis and premature entry to catagen more effectively than finasteride. Our results indicated that ginsenoside F2 decreased the expression of TGF-ß2 and SCAP proteins, which have been suggested to be involved in apoptosis and entry into catagen. This study provides evidence those factors in the SCAP pathway could be targets for hair loss prevention drugs.


Assuntos
Alopecia/induzido quimicamente , Alopecia/tratamento farmacológico , Apoptose/efeitos dos fármacos , Di-Hidrotestosterona , Ginsenosídeos/farmacologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Fator de Crescimento Transformador beta/efeitos dos fármacos , Animais , Caspase 12/metabolismo , Proliferação de Células/efeitos dos fármacos , Modelos Animais de Doenças , Finasterida/farmacologia , Finasterida/uso terapêutico , Ginsenosídeos/uso terapêutico , Folículo Piloso/efeitos dos fármacos , Folículo Piloso/crescimento & desenvolvimento , Humanos , Camundongos , Transdução de Sinais/efeitos dos fármacos , Proteínas de Ligação a Elemento Regulador de Esterol/efeitos dos fármacos , Proteínas de Ligação a Elemento Regulador de Esterol/metabolismo , Fator de Crescimento Transformador beta/metabolismo
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