Sphere-like Clusters Research Articles

Knockdown of G Protein-coupled Estrogen Receptor 1 (GPER1) Enhances Tumor-supportive Properties in Cervical Carcinoma Cells.

A wide variety of answers can be found regarding the question of whether G-protein-coupled estrogen receptor 1 (GPER1) is tumor supportive or tumor suppressive. In cervical carcinoma (CC), the function of GPER1 is poorly understood. In this work, we aimed to clarify what role GPER1 plays in CC, tumor promoting of tumor suppressive. Transient GPER1 silencing was conducted using RNAi and approved by RT-qPCR. Clonogenic potential was tested by colony and sphere formation. Expression of SERPINE1/PAI-1 was quantified by RT-qPCR and Western blot. Morphological changes were analyzed using Phalloidin staining. Localization of GPER1 in tumor spheres was examined by immunofluorescence. After GPER1 knockdown, more colonies formed in HeLa and SiHa, and larger colonies formed in C33-A and SiHa CC cells. Size of HeLa and SiHa tumor spheres was also increased. In addition, number of HeLa tumor spheres was elevated, and larger secondary colonies were present. C33-A only formed tumor sphere-like clusters showing no differences in number and size. Phalloidin staining revealed greater cellular length-to-width ratio and increased average filopodia length. Expression of SERPINE1/PAI-1 was increased in HeLa and decreased in C33-A. In SiHa cells, SERPINE1 was slightly decreased, whereas the protein PAI-1 was increased. Strong expression of GPER1 was detectable in peripheral areas and in sprouts of tumor spheres. GPER1 appears to be tumor suppressive in CC, as GPER1 knockdown provoked increased stem cell properties and increased migration/invasion. EMT also appears to be enhanced. Of interest is the increase in SERPINE1/PAI-1 expression after GPER1 knockdown.

Stem Cells from Human Exfoliated Deciduous Teeth: A Concise Review.

Stem Cells from Human Exfoliated Deciduous Teeth (SHED) originate from the embryonic neural crest as ectodermal mesenchymal stem cells and are isolated from human deciduous teeth. SHED expresses the same cell markers as Embryonic Stem Cells (ESCs), such as OCT4 and NANOG, which make SHED to have a significant impact on clinical applications. SHED possess higher rates of proliferation, higher telomerase activity, increased cell population doubling, form sphere-like clusters, and possess immature and multi-differentiation capacity; such high plasticity makes SHED one of the most popular sources of stem cells for biomedical engineering. In this review, we describe the isolation and banking method, the current development of SHED in regenerative medicine and tissue engineering in vitro and in vivo.

Large-scale high-density culture of hepatocytes in a liver microsystem with mimicked sinusoid blood flow.

In vitro engineering of liver tissue is a rapidly developing field for various biomedical applications. However, liver tissue culture is currently performed on only a small scale with a low density of hepatocytes. In this study, a simple design was introduced in a liver microsystem to enhance the transport of nutrients (e.g., oxygen and glucose) for the three-dimensional large-scale, high-density culture of hepatocytes. In this design, convection across the cell culture zone was generated to mimic sinusoid blood flow (SBF) based on the pressure difference between two fluids flowing in a countercurrent manner on either side of the cell culture zone. First, the distributions of living and dead cells in different culture subzones under various perfusion flow rates were observed, analysed, and compared. Then, the enhanced transport of nutrients was experimentally validated in relation to the viability of cells and theoretically explained by comparing the fluid velocity and oxygen concentration distribution in the cell culture zone in counterflow and coflow modes. Finally, the functions of the SBF-mimicked liver microsystem were assessed on the basis of specific metabolites, synthesized proteins, and bilirubin detoxification of hepatocytes, with collagen and alginate as extracellular matrices. Under this design, the density of hepatocytes cultured at the 3-mm-thickness scale reached ~7×107 cells/ml on Day 7, and the metabolism and detoxification functions of the cells worked well. In addition, a liver rope-like structure and sphere-like clusters of cells were observed. This work provides insight for the design of a bionic liver microsystem.

Creating Quasi Two-Dimensional Cluster-Assembled Materials through Self-Assembly of a Janus Polyoxometalate-Silsesquioxane Co-Cluster.

Clusters are an important class of nanoscale molecules or superatoms that exhibit an amazing diversity in structure, chemical composition, shape, and functionality. Assembling two types of clusters is creating emerging cluster-assembled materials (CAMs). In this paper, we report an effective approach to produce quasi two-dimensional (2D) CAMs of two types of spherelike clusters, polyhedral oligomeric silsesquioxanes (POSS), and polyoxometalates (POM). To avoid macrophase separation between the two clusters, they are covalently linked to form a POM-POSS cocluster with Janus characteristics and a dumbbell shape. This Janus characteristics enables the cocluster to self-assemble into diverse nanoaggregates, as conventional amphiphilic molecules and macromolecules do, in selective solvents. In our study, we obtained micelles, vesicles, nanosheets, and nanoribbons by tuning the n-hexane content in mixed solvents of acetone and n-hexane. Ordered packing of clusters in the nanosheets and nanoribbons were directly visualized using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) technique. We infer that the increase of packing order results in the vesicle-to-sheet transition and the change in packing mode causes the sheet-to-ribbon transitions. Our findings have verified the effectivity of creating quasi 2D cluster-assembled materials though the cocluster self-assembly as a new approach to produce novel CAMs.

Fabrication of Novel CuO Films with Nanoparticles-Aggregated Sphere-Like Clusters on ITO and Their Nonenzymatic Glucose Sensing Applications

In this work, novel nanoparticles-aggregated CuO sphere-like clusters were successfully synthesized on indium tin oxide (ITO) glass through a facile two-step procedure consisting of the fabrication of Cu2O films directly grown on ITO surface by electrodeposition, and subsequent calcinations of Cu2O films leading to the formation of CuO films. The morphology and structure of as-synthesized samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the size of nanoparticles constituting sphere-like clusters structure obtained at 200[Formula: see text]C is much smaller than that of obtained at other temperature, which can provide large surface area for catalytic reaction. The CuO/ITO electrode was applied to detect glucose by cyclic voltammetry (CV) and amperometric detection ([Formula: see text]). It was found that the obtained CuO films modified ITO electrode exhibited a much higher electrocatalytic activity for the oxidation of glucose in an alkaline medium through heat treatment of 200[Formula: see text]C. A favorable performance with a high sensitivity of 1841.5544[Formula: see text][Formula: see text]A mM[Formula: see text] cm[Formula: see text] to glucose ranging from 1.0[Formula: see text][Formula: see text][Formula: see text]10[Formula: see text][Formula: see text]M to 5.0[Formula: see text][Formula: see text][Formula: see text]10[Formula: see text][Formula: see text]M, a low operating potential of 0.35 Vversus Ag/AgCl and a fast amperometric response (within 3[Formula: see text]s) were achieved on such CuO/ITO electrode. It also showed outstanding long-term stability and good reproducibility. Notably, poisoning by chloride ions and interference from ascorbic acid, uric acid and acetaminophen were negligible. Therefore, the nanoparticles-aggregated CuO sphere-like clusters would be a promising candidate electrode material for the development of nonenzymatic glucose sensors.

Visible light photocatalytic activity of rutile TiO2 fiber clusters in the degradation of terephthalic acid

Rutile TiO2 nanoparticles, in different structural and morphological properties, were produced by the hydrolysis of titanium tetrachloride in a highly acidic reaction media at moderate temperatures without calcination. Their photocatalytic activities were investigated in the liquid-phase degradation of terephthalic acid under visible light illumination. The parameters, which are the concentration of the titanium tetrachloride solution (0.1–1 M) and reaction temperature (60–95 °C), effective on the properties of the particles, and their photocatalytic performances, were investigated. The XRD patterns indicated a pure rutile crystal structure at moderate temperatures without need of calcination. The FEGSEM images showed the formation of flower-, pinecone-, and sphere-like clusters consisting of interconnected nanofibers. The N2 adsorption–desorption isotherms pointed out the microporous structure of the clusters. Band gap energies were found to be varying between 3.02 and 3.08 eV due to the well-developed rutile crystallite structure. Systematic studies elucidated that the optimum reactant concentration and reaction temperature are 0.5 M TiCl4 and 95 °C, respectively. The rutile clusters synthesized at the optimum reaction conditions exhibited 99 % of the photocatalytic degradation of TPA under visible light illumination at shorter irradiation times compared with commercial P25 TiO2.

Eliminating Evolved Oxygen through an Electro-flocculation Efficiently Prompts Stability and Catalytic Kinetics of an IrOx·nH2O Colloidal Nanostructured Electrode for Water Oxidation

A facile approach which harnesses dual-potential pulsed amperometric technique to expedite the water oxidation and oxygen reduction reactions intermittently through an electro-flocculation is reported. The new strategy yields discriminated physical morphology and chemical composition of as-prepared IrOx·nH2O, compared with the previous approach, which lead to an alteration of kinetic mechanism and enhancement of stability in alkaline solution (pH 12). By the virtue of the catalyst architecture efficiently producing electroactive Ir sites (Γea=∼4 × 10−8molmol/cm2), η for water oxidation was measured to be 0.22V (at current density of 1.2mA/cm2). The tafel slope was estimated to be 29±1mV per decade, suggesting the recombination of S−Oads as the rate determining step. Contrast to the considerably flocculated structure reported previously, the IrOx·nH2O construction herein was well-defined sphere-like clusters (5-10nm) and resides separately. Furthermore a XPS examination revealed that the oxygen-containing constituents of the prepared IrOx, regardless of preparation techniques, were hydroxides (dominate) and hydrated water, instead of the lattice oxide ions. IrOx·nH2O formed using the present strategy yielded O-to-Ir ratio to be 2.9, which was substantially lower than 6.4 of a hydroxide-abundant constituent prepared without intermittent elimination of oxygen.

Isolation and Characterization of Adult Spinal Disc Stem Cells from Healthy Human Spinal Disc Tissues

This report details the isolation, culture, and characterization of spinal disc stem cells derived from human adult spinal disc tissue specimens. Using stem cell suspension culture methods and biology, human adult spinal disc stem cells were isolated and monoclonally cultured into multicellular sphere-like clusters (discospheres). Discospheres from the first culture series were collected, processed, and replated as single stem cells for serial expansion studies using suspension culture, demonstrating linear expansion was possible. Discospheres and adult spinal disc stem cells were plated on matrix coated culture surfaces in stem cell media for several hours to allow fixation, and assayed for the stem cell biomarkers. Discospheres and adult spinal disc stem cells were plated on laminin-coated culture surfaces in chondrogenic media and culture conditions for 14 days to differentiate them into NP cells. NP cells cultured from these experiments demonstrated NP morphology and phenotype; NP biomarker expression, secretion of extracellular matrix, and the ability to be serially passaged with large volume expansion possible. Tissue engineering studies using the “burst kinetic assay”, demonstrated that discospheres have remarkable intrinsic developmental and tissue engineering biology that is robust and organized. In summary, adult disc stem cells and NP cells have been isolated, cultured, and characterized, from healthy spinal disc tissues. These findings demonstrate the important potential to be explored for using stem cell based tissue engineering for the treatment of degenerative disc disease (DDD).

Synthesis of Ce3+ doped ZnFe2O4 self- assembled clusters and adsorption of chromium(VI)

A solvothermal synthetic route was used to prepare Ce3+ doped Zn ferrites, where sphere-like clusters aggregated by nanosized particles were fabricated. The size of the cluster and the saturation magnetization of the sample are decreasing with the increase of Ce3+. These samples can be easily separated from aqueous solutions by applying a magnetic field and have a high loading capacity of Cr(VI). The Cr(VI) adsorption experiments indicated that the adsorption was divided into two processes, in which the first one took place about 6h, the second one took place between 6 and 96h. The maximum adsorption capacity for Cr(VI) was determined to be 57.24mg/g. Langmuir model was employed to fit the adsorption isotherm, which implied the single layer adsorption. The data of SBET, external area and porous area of the samples can be used to explain these adsorption processes. And the Ce3+ ions doped in the sample induced the increasing adsorption capacity of Cr(VI). The adsorption process can be described by the pseudo-second-order kinetic model.

Tracing nucleation pathways in protein aggregation by using small angle scattering methods

Heat and alcohol-induced nucleation pathways of the whey protein β-lactoglobulin were investigated using small angle neutron and X-ray scattering for structural characterization. Protein solutions at various concentrations were either heated stepwise to 80 °C or mixed with ethanol to 50% (v/v). Heating induces dissociation of the β-lactoglobulin dimer in neutral pH aqueous medium, leading to nucleation at about 75 °C of tetrameric, cylindrical clusters, as indicated by three dimensional rigid body and bead modelling performed to fit scattering curves. In contrast to heating, ethanol addition induces the formation of fairly compact, internally disordered sphere-like clusters composed of rod-like submolecular structural units. At higher concentrations these clusters show typical colloidal behaviour, exhibiting long-range repulsive interactions, as also confirmed by dynamic light scattering measurements. The results contrast the effect of different unfolding scenarios on preferred nucleation pathways in subsequent protein assembly processes in various solution environments.

Self-Contained Induction of Neurons from Human Embryonic Stem Cells

BackgroundNeurons and glial cells can be efficiently induced from mouse embryonic stem (ES) cells in a conditioned medium collected from rat primary-cultured astrocytes (P-ACM). However, the use of rodent primary cells for clinical applications may be hampered by limited supply and risk of contamination with xeno-proteins.Methodology/Principal FindingsWe have developed an alternative method for unimpeded production of human neurons under xeno-free conditions. Initially, neural stem cells in sphere-like clusters were induced from human ES (hES) cells after being cultured in P-ACM under free-floating conditions. The resultant neural stem cells could circumferentially proliferate under subsequent adhesive culture, and selectively differentiate into neurons or astrocytes by changing the medium to P-ACM or G5, respectively. These hES cell-derived neurons and astrocytes could procure functions similar to those of primary cells. Interestingly, a conditioned medium obtained from the hES cell-derived astrocytes (ES-ACM) could successfully be used to substitute P-ACM for induction of neurons. Neurons made by this method could survive in mice brain after xeno-transplantation.Conclusion/SignificanceBy inducing astrocytes from hES cells in a chemically defined medium, we could produce human neurons without the use of P-ACM. This self-serving method provides an unlimited source of human neural cells and may facilitate clinical applications of hES cells for neurological diseases.

Aggregation Kinetics of Coalescing Polymer Colloids

The aggregation behavior of a soft, rubbery colloidal system with a relatively low glass transition temperature, T(g) approximately -20 degrees C, has been investigated. It is found that the average gyration and hydrodynamic radii, R(g) and R(h), measured by light scattering techniques, evolve in time in parallel, without exhibiting the crossover typical of rigid particle aggregation. Cryogenic scanning electron microscopy (cryo-SEM) images reveal sphere-like clusters, indicating that complete coalescence between particles occurs during aggregation. Since coalescence leads to a reduction in the total colloidal surface area, the surfactant adsorption equilibrium, and thus the colloidal stability, change in the course of aggregation. It is found that to simulate the observed kinetic behavior based on the population balance equations, it is necessary to assume that all the clusters are spherical and to account for variations in the colloidal stability of each aggregating particle pair with time. This indicates that, for the given system, the coalescence is very fast, i.e., its time scale is much smaller than that of the aggregation.

Magic number 32 and 90 of metal clusters: A shell jellium model study

Motivated by the recent discovery of cage-like metal clusters, a shell jellium model is proposed to study the stability of cage-like clusters, using the density functional theory (DFT) with local density approximation (LDA). Based on the shell jellium model, it is found that certain metal clusters of a special number of electrons are even more stable than the sphere-like clusters described by the conventional spherical jellium model. The result shows two new magic numbers 32 and 90. These results provide us with a straightforward explanation for the stability of 32-electron clusters.

Simultaneous removal of perchlorate and arsenate by ion-exchange media modified with nanostructured iron (hydr)oxide

Hybrid ion-exchange (HIX) media for simultaneous removal of arsenate and perchlorate were prepared by impregnation of non-crystalline iron (hydr)oxide nanoparticles onto strong base ion-exchange (IX) resins using two different chemical treatment techniques. In situ precipitation of Fe(III) (M treatment) resulted in the formation of sphere-like clusters of nanomaterials with diameters of ∼5 nm, while KMnO 4/Fe(II) treatments yielded rod-like nanomaterials with diameters of 10–50 nm inside the pores of the media. The iron content of most HIX media was >10% of dry weight. The HIX media prepared via the M treatment method consistently exhibited greater arsenate adsorption capacity. The fitted Freundlich adsorption intensity parameters ( q = K × C E 1 / n ) for arsenate (1/ n < 0.6) indicated favorable adsorption trends. The K values ranged between 2.5 and 34.7 mgAs/g dry resin and were generally higher for the M treated media in comparison to the permanganate treated media. The separation factors for perchlorate over chloride ( α C l − Cl O 4 − ) for the HIX media were lower than its untreated counterparts. The HIX prepared via the M treatment, had higher α C l − Cl O 4 − than the HIX obtained by the KMnO 4/Fe(II) treatments suggesting that permanganate may adversely impact the ion-exchange base media. Short bed adsorber (SBA) tests demonstrated that the mass transport kinetics for both ions are adequately rapid to permit simultaneous removal using HIX media in a fixed bed reactor.

Magnetic neutron diffraction from the magnetic clusters in single crystalBaCuO2+x

Magnetic-neutron-diffraction studies of a single crystal of ${\mathrm{BaCuO}}_{2+x}$ confirm the antiferromagnetic structure of the ringlike ${\mathrm{Cu}}_{6}$ clusters with ground-state spin $S=3$ proposed by Wang et al. [Science 264, 402 (1994)]. No indication of a spontaneous ferromagnetic (or simple antiferromagnetic) ordering of the spherelike ${\mathrm{Cu}}_{18}$ $S=9$ clusters were observed down to a temperature of 50 mK, in disagreement with the suggestion based on magnetic-susceptibility measurements performed down to 2 K. However, diffraction scans under applied magnetic fields up to 3 T, at temperatures of 0.05 and 4.2 K align the sphere clusters ferromagnetically. The magnetic-field-induced ferromagnetic-diffraction pattern is consistent with the form factor of the ${\mathrm{Cu}}_{18}$ spherelike cluster. Frustration in the coupling with nearest neighbors leads to a paramagnetic behavior or a complex magnetic structure (noncollinear and/or incommensurate) of the spherelike clusters, consistent with our findings.

Morphogenesis of Calcification in Porcine Bioprosthesis: Insight from High Resolution Electron Microscopic Investigation at Molecular and Atomic Resolution

High resolution electron microscopy (HREM) coupled with energy dispersive X-ray microanalysis were used to investigate the morphogenesis of calcification in 28 explanted porcine bioprosthetic heart valves. Different morphology and compositions of calcific deposits were consistently observed in various valvular structures of all explanted porcine bioprostheses. The most common forms of calcific deposits were present as spherical particles and needle-shaped structures. HREM investigation of spherical particles of calcium phosphate revealed very fine electron-dense dots about 0.3-1.0 nm in diameter which were packed to form sphere-like clusters of about 2.0-3.5 nm in diameter in the particles. HREM observations of the microneedle-shaped structures even as small as 1.9 nm in thickness could identify the lattice fringes with center-to-center spacings of about 0.8-0.9 nm. Energy dispersive X-ray microanalysis defined the components of needle-shaped calcification as calcium and phosphorus in a ratio typical of hydroxyapatite crystals. The calcific deposits in the collagen tissue have been shown to be at discrete sites on or in the collagen fibrils as the spherical particles or homogeneous electron-dense masses. Based on HREM observations of different types of morphogenesis of calcification it is suggested that chemical processes of calcification accompanying the deposition of calcium in the implanted bioprosthetic heart valves are specific to each substrate system. The formation of amorphous calcium phosphate precursors and direct deposition of microcrystalline hydroxyapatites are considered to be the primary mechanisms of calcification occurring in implanted porcine bioprostheses.