Nm In Dimension Research Articles

A transient ischemic environment induces reversible compaction of chromatin.

BackgroundCells detect and adapt to hypoxic and nutritional stress through immediate transcriptional, translational and metabolic responses. The environmental effects of ischemia on chromatin nanostructure were investigated using single molecule localization microscopy of DNA binding dyes and of acetylated histones, by the sensitivity of chromatin to digestion with DNAseI, and by fluorescence recovery after photobleaching (FRAP) of core and linker histones.ResultsShort-term oxygen and nutrient deprivation of the cardiomyocyte cell line HL-1 induces a previously undescribed chromatin architecture, consisting of large, chromatin-sparse voids interspersed between DNA-dense hollow helicoid structures 40–700 nm in dimension. The chromatin compaction is reversible, and upon restitution of normoxia and nutrients, chromatin transiently adopts a more open structure than in untreated cells. The compacted state of chromatin reduces transcription, while the open chromatin structure induced upon recovery provokes a transitory increase in transcription. Digestion of chromatin with DNAseI confirms that oxygen and nutrient deprivation induces compaction of chromatin. Chromatin compaction is associated with depletion of ATP and redistribution of the polyamine pool into the nucleus. FRAP demonstrates that core histones are not displaced from compacted chromatin; however, the mobility of linker histone H1 is considerably reduced, to an extent that far exceeds the difference in histone H1 mobility between heterochromatin and euchromatin.ConclusionsThese studies exemplify the dynamic capacity of chromatin architecture to physically respond to environmental conditions, directly link cellular energy status to chromatin compaction and provide insight into the effect ischemia has on the nuclear architecture of cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-015-0802-2) contains supplementary material, which is available to authorized users.

Mg(OH)2 nanoparticles produced at room temperature by an innovative, facile, and scalable synthesis route

Nanoparticles form the fundamental building blocks for many exciting applications in various scientific disciplines. However, the problem of the large-scale synthesis of nanoparticles remains challenging. An original, eco-friendly, single step, and scalable method to produce magnesium hydroxide nanoparticles in aqueous suspensions is here presented. The method, based on an exchange ion process, is extremely simple and rapid (few minutes). It employs cheap or renewable reactants, operates at room temperature and does not require intermediate steps (washings/purifications) to eliminate undesired compounds. Moreover, it is possible to regenerate the exchange material and to reuse it for new operation of synthesis, according to a cyclic procedure, providing potential aptitudes of scalability of nanoparticles production. Some of the synthesis parameters are varied, and structural and morphological features of the produced nanoparticles, after few seconds from the beginning of the synthesis up to the ending time, are investigated by means of several techniques, such as X-ray diffraction (profile fitting and Rietveld refinement), transmission electron microscopy, infrared spectroscopy, thermal analyses, and surface area measurements. In any case, pure and stable suspensions are produced, characterized by crystalline and mesoporous Mg(OH)2 nanoparticles, with lamellar morphology. In particular, the nanolamellas appeared constituted by a superimposition of hexagonally plated and crystalline nanosized precursors (2–3 nm in dimensions), crystallographically oriented.

Structural and photoluminescent properties of nanowires formed by the metal-assisted chemical etching of monocrystalline silicon with different doping level

Silicon-nanowire layers grown by the metal-assisted chemical etching of (100)-oriented p-type monocrystalline silicon substrates with a resistivity of 10 and 0.001 Ω · cm are studied by electron microscopy, Raman scattering, and photoluminescence measurements. It is established that nanowires grown on lightly doped substrates are structurally nonporous and formed as crystalline cores covered by nanocrystals 3–5 nm in dimensions. Nanowires grown on heavily doped substrates are structurally porous and contain both small nanocrystals and coarser crystallites with equilibrium charge carriers that influence interband radiative recombination. It is found that the photoluminescence intensity of nanowires in the spectral range 1.3–2.0 eV depends on the presence of molecular oxygen.

Optical and structural properties of ensembles of colloidal Ag2S quantum dots in gelatin

The size dependences of the absorption and luminescence spectra of ensembles of hydrophilic colloidal Ag2S quantum dots produced by the sol-gel method and dispersed in gelatin are analyzed. By X-ray diffraction analysis and transmission electron microscopy, the formation of core/shell nanoparticles is detected. The characteristic feature of the nanoparticles is the formation of crystalline cores, 1.5–2.0 nm in dimensions, and shells of gelatin and its complexes with the components of synthesis. The observed slight size dependence of the position of infrared photoluminescence bands (in the range 1000–1400 nm) in the ensembles of hydrophilic colloidal Ag2S quantum dots is explained within the context of the model of the radiative recombination of electrons localized at structural and impurity defects with free holes.

Synthesis of Surface-Enhanced Raman Scattering-Active Gold Nanoflowers by 5-Hydroxytryptophan in Acidic Solution.

We demonstrated a one-step synthesis of gold nanoflowers by 5-hydroxytryptophan (5-HTP) in acidic solutions at room temperature. The synthesized nanoflowers are 400 nm in dimension consisting of a solid core and many small petal-like nanoparticles (30-50 nm) in various directions. The shape, size and surface morphology of the gold nanostructure could be tuned by controlling the molar ratio of 5-HTP to HAuCl4 and HCl concentration. Examination of the nanoparticles at different reaction stages with transmission electron microscopy (TEM) reveals the shape evolutionary process of the nanoflowers to get a better understanding on their possible formation mechanism. Additionally, these gold nanoflowers exhibit a high SERS performance because of textured surface which is expected to provide many active sites.

Enhancing electrochromic contrast and redox stability of nanostructure polypyrrole film doped by heparin as polyanion in different solvents

ABSTRACTHeparin‐doped polypyrrole (PPy‐Hep) and ‐doped polypyrrole (PPy‐ClO4) films are synthesized onto FTO‐coated glass electrode in a potentiostatic electrochemical process with the aim of producing uniform, transparent, and adherent coating. The resultant polymers are characterized via cyclic voltammetry, scanning electron microscopy (SEM), and UV–vis absorption spectroscopy. SEM study indicates that the PPy‐Hep film to be composed of a continuous interlinked network of quasi spherical grains (50–80 nm in dimensions). The electrochromic properties of PPy‐Hep and PPy‐ClO4 polymer films are compared to spectroelectrochemistry and switching studies. The effect of different solvents (water, propylene carbonate, and acetonitrile) on the electrochromic features of electropolymerized polymers has been investigated, and we find a very significant solvent effect. PPy‐Hep film exhibits switching time of 1 s and the maximum transmittance contrast (ΔT%) is 48% at 800 nm in water. In addition, presence of Hep causes drastic enhancement of electro‐optical stability of PPy. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3365–3371

Synthesis of Highly Stable Cobalt Nanomaterial Using Gallic Acid and Its Application in Catalysis

We report the room temperature (25–30°C) green synthesis of cobalt nanomaterial (CoNM) in an aqueous medium using gallic acid as a reducing and stabilizing agent. pH 9.5 was found to favour the formation of well dispersed flower shaped CoNM. The optimization of various parameters in preparation of nanoscale was studied. The AFM, SEM, EDX, and XRD characterization studies provide detailed information about synthesized CoNM which were of 4–9 nm in dimensions. The highly stable CoNM were used to study their catalytic activity for removal of azo dyes by selecting methyl orange as a model compound. The results revealed that 0.4 mg of CoNM has shown 100% removal of dye from 50 μM aqueous solution of methyl orange. The synthesized CoNM can be easily recovered and recycled several times without decrease in their efficiency.

Extended-Nanofluidics: Fundamental Technologies, Unique Liquid Properties, and Application in Chemical and Bio Analysis Methods and Devices

Engineering using liquids confined in channels 10-1000 nm in dimension, or "extended-nanofluidics," is the next target of microfluidic science. Liquid properties at this scale were unrevealed until recently because of the lack of fundamental technologies for investigating these ultrasmall spaces. In this article, the fundamental technologies are reviewed, and the emerging science and technology in the extended-nanospace are discussed.

Poly(3,4-ethylenedioxythiophene) Sheath Over a SnO2 Hollow Spheres/Graphene Oxide Hybrid for a Durable Anode in Li-Ion Batteries

SnO2 hollow spheres (HSs) were synthesized by a hydrothermal route by use of an organic additive (2-mercaptopropionic acid or MPA) and a cationic surfactant (cetyltrimethyl ammonium bromide or CTAB). The progressive transformation of SnO2 solid spheres to SnO2 HSs 140–150 nm in dimensions wherein a thin shell of densely packed SnO2 crystallites with a tetragonal crystal structure surrounds an empty core was followed by scanning- and transmission-electron microscopy. The roles of MPA as the HS structure-directing agent, CTAB as the moiety which prevents HS aggregation, and water as the solvent crucial for hollow core formation were independently determined by elaborate morphological analyses. With the goal of realizing superior electrochemical performance, hybrids of optimized SnO2 HSs embedded in graphene oxide (GO) nanosheets and enveloped by a sheath of a conducting polymer, poly(3,4-ethylenedioxythiophene) or PEDOT, were also synthesized; the continuity of the amorphous PEDOT coating on SnO2 HS/GO was confirmed by elemental mapping and X-ray photoelectron spectroscopy. Galvanostatic charge–discharge studies revealed an initial reversible capacity of 990 mA h g–1 for SnO2 HSs at a current density of 100 mA g–1, and a capacity of 400 mA h g–1 was retained after 30 cycles. A significant improvement in cycling performance was achieved in the SnO2 HS/GO/PEDOT hybrid, as the synergy between the moderately high intrinsic electronic conductivity of GO nanosheets and the ability of PEDOT to buffer the volume change during repetitive Li+ charge–discharge more efficiently compared to pristine SnO2 HS impart a capacity of 608 mA h g–1 at a current density of 100 mA g–1 to the hybrid, retained at the end of 150 cycles, and the latter value was ∼1248 mA h g–1 when the mass of only the SnO2 HS in the hybrid was considered. The SnO2 HS/GO/PEDOT hybrid also showed an excellent rate capability as a capacity of 381 mA h g–1 was attained even at a high current density of 2000 mA g–1. We demonstrate the viability of the SnO2 HS/GO/PEDOT hybrid as a durable high performance anode for Li-ion batteries.

Characterization of Sulfonated Diels-Alder Poly(phenylene) Membranes for Electrolyte Separators in Vanadium Redox Flow Batteries

Sulfonated Diels-Alder poly(phenylene) (SDAPP) membranes were synthesized and characterized as potential electrolyte separators for vanadium redox flow batteries. The SDAPP membranes studied had ion exchange capacities of 1.4, 1.8 and 2.3 meq/g. Transmission electron microscopy imaging shows that the ionic domains in SDAPP are roughly 0.5 nm in dimension, while Nafion has a hydrophilic phase width of around 5 nm. The sulfuric acid uptake by SDAPP was higher than that for Nafion, but the materials had similar water uptake from solutions of various sulfuric acid concentrations. In equilibration with sulfuric acid concentrations ranging from 0–17.4 mol·kg−1, SDAPP with a IEC of 2.3 meq/g had the highest conductivity, ranging from 0.21 to 0.05 S·cm−1, while SDAPP with a IEC of 1.8 had conductivity close to Nafion 117, ranging from 0.11 to 0.02 S·cm−1. With varying sulfuric acid concentration and temperature, vanadium permeability in SDAPP is positively correlated to the membrane's IEC. The vanadium permeability of SDAPP 2.3 is similar to that of Nafion, but permeability values for SDAPP 1.8 and SDAPP 1.4 are substantially lower. The vanadium permeation decreases with increasing electrolyte sulfuric acid concentration. Vanadium diffusion activation energy is about 20 kJ·mol−1 in both SDAPP and Nafion.

Nanosuspensions of 10-hydroxycamptothecin that can maintain high and extended supersaturation to enhance oral absorption: preparation, characterization and in vitro/in vivo evaluation

The purpose of the study was to prepare and characterize nanosuspensions that can maintain high and extended supersaturation to improve the dissolution and absorption of poorly soluble 10-hydroxycamptothecin (10-HCPT). 10-HCPT oral nanosuspensions (HCPT-Nanosuspensions) were produced on a laboratory-scale by microprecipitation- high pressure homogenization method. The particle morphology and the physical state were studied using transmission electron microscopy, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). Supersaturated dissolution tests were carried out with the paddle method. Caco-2 cell experiments were performed to imitate the oral absorption. The in vivo pharmacokinetics studies were undertaken in rats following oral administration. The 10-HCPT nanoparticles were 135 nm in dimension before lyophilization and were claviform or lump in shape. XRPD and DSC both confirmed that a portion of 10-HCPT was present in a crystalline state in nanosuspension. Supersaturated dissolution tests showed HCPT-Nanosuspensions could maintain high supersaturated level for an extended period time. The cell experiment on HCPT-Nanosuspensions showed a significantly higher uptake and greater membrane permeability compared with the other formulations. The pharmacokinetic test exhibited HCPT-Nanosuspensions had a similar pharmacokinetic performance with 10-HCPT solution. In conclusion, highly and extendedly supersaturated HCPT-Nanosuspensions have been prepared which could result in high peak concentration (Cmax) and great exposure (AUC) after oral administration.

Lipid-based nanoparticles in cancer diagnosis and therapy.

Today, researchers are constantly developing new nanomaterials, nanodevices, and nanoparticles to meet unmet needs in the delivery of therapeutic agents and imaging agents for cancer therapy and diagnosis, respectively. Of particular interest here are lipid-based nanoparticles (LNPs) that are genuine particles (approximately 100 nm in dimension) assembled from varieties of lipid and other chemical components that act collectively to overcome biological barriers (biobarriers), in order for LNPs to preferentially accumulate in or around disease-target cells for the functional delivery of therapeutic agents for treatment or of imaging agents for diagnosis. The capabilities of these LNPs will clearly vary depending on functional requirements, but the nanoscale allows for an impressive level of diversity in capabilities to enable corresponding LNPs to address an equally diverse range of functional requirements. Accordingly, LNPs should be considered appropriate vehicles to provide an integrated, personalized approach to cancer diagnosis and therapy in future cancer disease management.

Biosynthesis of gold and silver nanoparticles using a novel marine strain of Stenotrophomonas

The present study aims at exploiting marine microbial diversity for biosynthesis of metal nanoparticles and also investigates role of microbial proteins in the process of bio-mineralization of gold and silver. This is the first report for concurrent production of gold and silver nanoparticles (AuNPs and AgNPs) by extracellular secretion of a novel strain of Stenotrophomonas, isolated from Indian marine origin. This novel strain has faster rate kinetics for AgNPs synthesis than any other organism reported earlier. The nanoparticles were further characterized using UV-vis spectrophotometer, TEM, DLS and EDAX confirming their size ranging from 10-50 nm and 40-60 nm in dimensions for AuNPs and AgNPs, respectively. TEM analysis indicated formation of multi-shaped nanoparticles with heterogeneous size distribution in both the cases. Finally, the SDS-PAGE analysis of extracellular media supernatant suggested a potential involvement of certain low molecular weight secretory proteins in AuNPs and AgNPs biosynthesis.

Silicate anion-stabilized layered magnesium–aluminium hydrotalcite

Layered magnesium–aluminum hydrotalcite (HT) were completely intercalated and stabilized with silicate anions. The silicate anion-stabilized HT retained the layered structure and possessed a high surface area of 530–540 m2 g−1 with needle-like particles 60 nm × 4 nm in dimension. The findings of FT-IR, powder XRD, TGA, DSC and 29Si MAS-NMR revealed that silicate anions were intercalated and coated on the surface of layered HTs with the formation of a solid solution of magnesium silicate and HT. The resultant silicate-anion-intercalated materials are found to be promising catalysts for the synthesis of 1-phenoxy-2-propanol using phenol with propylene oxide.

Polyoxometalate macroion induced phase and morphology instability of lipid membrane

The interaction of multivalent macroions with cell membrane can have a profound and significant impact on the functionality and viability of the cell membrane, and this is also critically related to drug and gene delivery as well as nanomaterial cytotoxicity. Using AFM, calorimetry, and light scattering techniques, we have investigated the effect of an anionic polyoxometalate (POM) nanocluster as a model macroion on the phase and structural stability of a lipid bilayer. A POM is distinct from commonly used nanoparticles, in this case comprising a stoichiometric and ordered crystalline nanocluster of typically <5 nm in dimension with uniformly distributed high surface charge density. We have found that the anionic POM nanocluster can strongly adsorb onto a zwitterionic lipid bilayer, which is usually considered as neutral and uncharged, due to the strong electrostatic attraction in a similar fashion to the interaction of a POM with a cationic lipid bilayer. More interestingly, the adsorption of POM also results in the gelation of the lipid bilayer that is otherwise in the fluid phase in the absence of the POM macroion. By examining lipid bilayers with varied lipid headgroup chemistry and phase state, we have revealed that the energy released upon the POM adsorption on the lipid bilayer is contributed not only from the enthalpy associated with gelation, but also from the entropy associated with local surface reconstruction of the lipid bilayer. A POM-induced entropic penalty on the lipid bilayer is confirmed by both liposome shrinkage and bilayer morphological disruption, including the formation of pores, buds, and multilayer stacks on a POM-adsorbed lipid membrane. Hence, the accompanied phase and morphological instability induced by the POM is unique and surprising, in contrast to the fact that only one, but not both, of the phenomena has been reported previously with hydrophilic or hydrophobic nanoparticles. Our results offer an unprecedented new insight into nanomaterial design and selection for controlled molecular transport through cell membranes.

The effect of PEG encapsulated silver nanoparticles on the thermal and electrical property of sonochemically synthesized polyaniline/silver nanocomposite

An investigation of microstructure of polyaniline nanocomposite is presented. The highly stable, semiconducting polyaniline/silver nanocomposites are prepared in-situ, employing the acoustic cavitation mechanism to obtain the composite in nanophase. The materials are characterized by UV-visible spectroscopy (UV–vis), transmission electron microscopy (TEM), thermogravimetric analyzer (TGA) and fourier transform infrared spectroscopy (FTIR). The polyaniline nanocomposites have an extended conformation in N-methyl-2-pyrrolidinone (NMP), as seen from UV–vis spectra. The plasmon resonances for silver nanoplates are also seen. A high thermal stability is observed for the polyaniline/silver nanocomposites which increased with increasing silver content. The TEM studies show that the polyaniline is formed as nanofibers, with plate-like metallic silver nanoparticles (50 nm × 35 nm in dimension) embedded into them. From the electrical conductivity measurements of pure polyaniline and its nanocomposites it was found that incorporation of polyethylene glycol stabilized silver nanoparticles leads to increased intermolecular charge hopping that results in enhanced electrical conductivity of the nanocomposites. TGA and DSC results indicated greater thermal stability for the nanocomposites along with higher crystallinity. A study of spreading resistance of the materials, done using scanning spreading resistance microscope, revealed localized sites of high and low conductivity within the polyaniline. The low conducting sites were fewer in the case of nanocomposites.

Nanostructures of designed geometry and functionality enable regulation of cellular signaling processes.

Extracellular matrices (ECM) triggered cellular signaling processes often begin with the clustering of the cellular receptors such as integrin and FcεRI. The sizes of these initial protein complexes or clusters are tens to 100 nm in dimension; therefore, engineered nanostructures could provide effective mimics of ECM for investigation and control of the initial and downstream specific signaling processes. This current topic discusses recent advances in nanotechnology in the context of design and production of matching chemical functionality and geometry for control of specific cellular signaling processes. Two investigations are reported to demonstrate this concept: (a) how the presentation of antigen at the nanometer scale would influence the aggregation of FcεRI, which would impact the formation of activation complexes, leading to the rearrangement of actin in cytoskeleton and degranulation or activation of mast cells; (b) how the engineered nanostructure could guide the initial integrin clustering, which would impact the formation of focal adhesion and downstream cell signaling cascades, leading to polarization, migration, and morphological changes. Complementary to engineered ECMs using synthetic ligands or peptides, or topographic control at the micrometer scale, nanostructures of designed geometry and chemical functionality provide new and effective biochemical cues for regulation of cellular signaling processes and downstream behaviors.

Laser-induced birefringence of methyl red in a polymeric nanocomposite prepared by sol–gel method

Non-linear optical (NLO) dyes used as guests in polymeric films have recently attracted interests in optical applications. In this regard, dye-grafted polymeric systems can outperform conventional guest–host dye-containing films because they have lower loading limitations and aggregation problems. These give rise to enhanced molecular orientation. The work presented here is an attempt to study the laser-induced birefringence for a novel sol–gel based polymeric nanocomposite prepared by reacting an NLO dye (methyl red) and an epoxy silane coupling agent at different concentrations of dye. 3-Glycidoxy propyltrimethoxysilane was hydrolyzed and condensed to prepare a siloxane structure from which a dye-containing hybrid was obtained. The structural and morphological properties of the resulting nanocomposites were studied by FTIR spectroscopy, differential scanning calorimetry and transmission electron microscopy. Results showed that the dye was chemically attached to the siloxane structure built through sol–gel processing. This chemical modification leads to nanostructured morphology in which inorganic phase was entangled to the organic phase. The size of clusters formed was 60–80 nm in dimension. The optical responses of nanocomposites were investigated at different process parameters, including dye concentration, film thickness and curing regimes. These were then discussed based on the photochemical and photothermal properties of the dye molecules, the rotation dynamic of which was shown to strongly depend on the physical and chemical properties of the host. The samples with 8 wt% of dye revealed the maximum birefringence, while the sample with 10 wt% showed the best memory effect. The best condition for curing was found to be 24 h. By increasing the film thickness, there was an increase in the amount of induced birefringence.

Crystallization in Aggregates of Calcium Phosphate Nanocrystals: A Logistic Model for Kinetics of Fractal Structure Development

Calcium phosphate crystallization is of importance in medicine and materials science, and aggregation frequently happens at its early stage. Herein, we report a kinetic study of crystallization in particles of aggregated nanocrystals of calcium phosphate by in situ synchrotron small-angle X-ray scattering. The particles were random fractal aggregates, having diameters of 20-60 nm and comprising structural units of 2.5 nm in dimension. With the application of a logistic model, the structural changes of the particles were characterized by the successive developments of mass and surface fractal dimensions. The rate constant of mass fractal development was found to be 0.052 h(-1), corresponding to the generation of crystallites on the pre-existing seeds inside an aggregate. These newly formed nanocrystals then detached from their seeds and fell into the voids. Afterward, the surface fractal structure developed at a rate of 0.11 h(-1), making the particle surface less rough. During this period, a transition layer of 1.2-nm thickness emerged between a particle and the surrounding solution. Our findings present an advance toward understanding the crystallization in particles of aggregated nanocrystals and would be beneficial for preparing nanocrystals and recognizing the roles of other substances (such as proteins and metals) in both biological and synthetic systems.

Photo-to-current response of Bi2Fe4O9 nanocrystals synthesized through a chemical co-precipitation process

Pure-phase Bi2Fe4O9 nanocrystals of mullite-type structure were synthesized through a facile chemical co-precipitation process. The nanocrystals consist of nanorods with transverse size of 100–200 nm and nanoparticles of 80–150 nm in dimension. The nanorods are preferentially grown along [001] and show flat side facets (110) and (10). The nanocrystals exhibit two narrow bandgaps of 2.05 eV and 1.53 eV. A steady photocurrent of 37 μA cm−2 was observed in the Bi2Fe4O9 nanocrystals under visible-light irradiation. The photo-to-current response of Bi2Fe4O9 has not been reported before. Such a high photo-to-current conversion efficiency is ascribed to the synergistic effect of energy band structure and the high reactivity of exposed (110) and (10) facets.