Papers by Keyword: Nanospheres

Abstract: A facile method to selectively synthesize nano-scaled Gd₂O₃ with different morphology such as nanosheres and nanorods has been developed in our report. The precursors GdOHCO₃ can be prepared by a two-step hydrothermal process via homogeneous generation of hydroxide ions through the hydrolysis of urea, and the formation of different morphology structures were obtained under different reaction temperatures. After further heating treatment, a transformation from GdOHCO₃ to cubic Gd₂O₃ takes place. The morphology and size of nano Gd₂O₃ strongly depend on that of the precursors GdOHCO₃. The X-ray diffraction, transmission electron microscopy and scanning electron microscopy were employed to characterize the as-obtained low-dimensional nanostructures. And the effects of hydrothermal temperature, solvent and urea concentration on the morphologies of the products were also studied.

Abstract: Regenerated Antheraea Pernyi silk fibroin (ASF) solution was prepared by dissolving Antheraea Pernyi (A. pernyi) silk fiber in lithium thiocyanate solution. Atomic force microscopy (AFM) examination showed that there were many short nanofibers in regenerated ASF solution, which were made up of 10-20 nm nanospheres. In this paper, we discussed the formation mechanism of these nanofibers. The results of the surface tension showed that ASF had surface active and can significantly decline the surface tension of water from 73 mN/m to 51 mN/m. The hydrophobic side chains of ASF molecular would try to break away from water environment and thereby undergo self-assembly into nanospheres. And then, these nanospheres arrange into a short nanofiber. Then, the ASF nanofiber film was prepared by casting regenerated ASF solution blended with glycol. The structure of ASF was β-sheet and the film was water-insoluble. This blend film not only had excellent mechanical properties, but also can be biodegradated by enzyme in vitro. All of this indicated that this new regenerated ASF nanofiber film not only provided excellent biocompatibility, but also had large surface as extracellular matrix (ECM) to cell adhesion. The film made of nanofiber was similar to ECM on the nanoscale, which promoted cell migration and proliferation. In summary, it provided a great potential as a biological material.

Abstract: Ultraviolet(UV) irradiated polymerization is a new way to synthesis of the polymeric nanoparticles due to its security, environmental protection, and low investment, as compared to the thermal-initiated polymerization. In this paper, polystyrene-g- poly(N-isopropylacrylamide) (P(St-g-NIPAAM)) nanospheres were prepared by photo-initiated dispersion copolymerization of St and macromonomers, PNIPAAM with a vinyl end group, in a mixture of ethanol and water using 2,2-dimethoxy-2-phenylacetophenone (BDK) as the photo-initiator. The obtained nanospheres were characterized by scanning electron microscopy (SEM) and laser light scattering (LLS). The results showed that the P(St-g-NIPAAM) particles were highly spherical and monodisperse. The size of the nanospheres could be controlled by changing the concentration of the macromonomers, polymerization temperature, and irradiation time and energy.

Abstract: Highly uniform and monodisperse KY₃F₁₀ nanospheres, with an average diameter of 300 nm, have successfully prepared through a simple solution method employing the reaction of Ln(NO₃)₃ and KBF₄ under ambient conditions, without any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The SEM images illustrate that these spheres were actually composed of randomly aggregated nanoparticles.

Abstract: Betamethasone acetate (BA) is a glucocorticoid steroid with anti-inflammatory and immunosuppressive properties which can be used in treatment of asthma and itching. In this research, polyvinyl alcohol nanospheres loaded by betamethasone acetate were prepared by oil in water emulsion method after which they were exposed to 1, 2 and 4 cycles of freeze-thawing (F-T) process including 24 hours freezing cycle at -25 °C and 24 hours thawing at ambient temperature. Nanospheres fabrication was confirmed by transmission electron microscopy and betamethasone release was analyzed by UV spectrophotometer at 245 nm. The results revealed that by increasing the number of F-T cycles the rate of drug release decreased. The effect of BA concentration was also investigated on human chondrosarcoma (sw 1353). The MTT assay was utilized to assess the cell proliferation. The results showed that these biocompatible nanospheres can be used for sustained release of such drugs for more than four months and drug release rate can be effectively controlled by implementing F-T cycles.

Abstract: Copolymer poly(D,L-lactide-co-glycolide) is used for obtaining the systems for controlled delivery of medicaments. Its specific characteristics make it suitable for various researches where its synthesis is performed in different ways. Using the system for controlled delivery of medicaments, an equal concentration of the medicament is achieved in the body throughout an extended period of time and it has advantages over the conventional methods. In this paper we present a new solvent/non-solvent chemical method for obtaining DLPLG nanospheres. In the experiment various stabilizers were used in order to examine their influence on morphological characteristics of DLPLG particles. The samples were characterized by Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Stereological analysis.

Abstract: Nanocubes, monodispersed nanocrystals and nanospheres of Au have been prepared by a simple reaction between HAuCl4·4H2O, NaOH and NH2OH·HCl in the presence of gelatin. The role of gelatin and the affection of pH in producing the nanoparticles of Au were discussed. The products were characterized by X-ray powder diffraction, transmission electron microscopy, and UV-visible absorption spectroscopy. The sizes of the monodispersed nanocrystals of Au were estimated by Debye-Scherrer formula according to XRD spectrum.

Abstract: Previously, we have developed a novel method for suspension culture of anchoragedependent animal cells using biodegradable polymer nanospheres. In this study, we compared the polymer nanosphere culture method to dextran microcarrier culture method, which is a conventional suspension culture method. Most of human dermal fibroblasts (91 ± 5 %) cultured with polymer nanospheres formed aggregates on day 2. Most of cells (92 ± 7 %) attached onto microcarriers by 4 h. Microcarrier culture method had a lower apoptotic activity (3.4 folds on day 4), compared to the nanosphere culture. The microcarrier culture method had a higher cell growth (2.4-fold versus 1.7- fold growth on day 4) than the nanosphere culture. Although the polymer nanosphere culture method did not yield better outcomes than the microcarrier culture, the polymer nanosphere culture method may offer advantages over the microcarrier culture method with respect to cell protection from the shear stress during agitation at high speed and cell transplantation without enzyme digestion process to harvest cultured cells.

Abstract: The physicochemical characteristics (SEM, N2 adsorption, FT-IR, MASNMR) of samples from kinetics (10 min, 20 min, 30 min, 1 h and 3h) of hydrolysis of tetraethyl orthosilicate (TEOS) gives new insight into the synthesis of nanosphere. The particle sizes are increased with time, however, the surface areas decreased. FT-IR investigation reveals the presence of high intensed silanol groups of 960 cm-1 at 10 min, which reduced on progress of the reaction time. This suggests the partial hydrolysis and condensation of alkoxy groups in TEOS. 29Si MASNMR analysis shows the presence three different silica species(Q4, Q3 and Q2) in 10 and 20 min samples. The intensity of Q2 species decreases with time and other species concentration were increased.

Abstract: Crucumin (diferuloylmethane) is a major active component of turmeric, but its bioavailability of oral administration is very low. In order to improve its pharmaceutical efficiency in oral use, poly (d,l-lactide) (PDLLA) nanospheres containing curcumin are successfully fabricated using a modified spontaneous emulsification solvent diffusion (SESD) method. The morphology, size and distribution of the resulting nanospheres are characterized by TEM and laser light scattering method. Drug contents in the nanospheres are calculated through UV spectrophotometer method. As a result, regular spherical PDLLA nanospheres containing curcumin are obtained and their effective diameters are 289 nm with narrow distribution (Pd=0.118)