Xiaodan Sun

Preparation of nanocrystalline metal oxide powders with the surfactant-mediated method

Abstract Nanocrystalline metal oxides (ZnO, NiO, and SnO2) powders with an average particle diameter of 18–55 nm have been successfully prepared with the surfactant-mediated method. The cationic surfactant (cetyltrimethylammonium bromide, CTAB) and the hydrous metal chlorides (ZnCl2·2H2O, NiCl2·6H2O, and SnCl4·5H2O) appear to be the good candidates for obtaining a high yield of nanoparticles. The resultant products have been characterized by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and transmission electron microscopy (TEM). The resulting powders are highly crystalline and largely monodisperse oxide particles. The surfactant-mediated method turned out to be suited for the preparation of the nanocrystalline oxide powders. Through this method, it is possible to obtain nanocrystalline metal oxide powders.

Preparation and characterization of SnO2 nanoparticles with a surfactant-mediated method

Using a surfactant-mediated method, tin dioxide nanoparticles with a high surface area were generated within the template of the cationic surfactant (cetyltrimethylammonium bromide) micelle assembly from the hydrous metal chloride (SnCl4 ? 5H2O). The as-synthesized product was amorphous and transformed into crystalline calcined at 500?C for 2 h, and exhibited a higher Brunauer?Emmet?Teller surface area of 69.2 m2 g?1. The resulting particles were highly crystalline and largely monodisperse oxide particles in the nanometre range (15?25 nm). Thermogravimetric analysis, x-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy were used to characterize the final products.

Hyaluronic acid hydrogel modified with nogo-66 receptor antibody and poly-L-lysine to promote axon regrowth after spinal cord injury.

The biomaterials used for central nervous system injury require not only interacting with specific cell adhesion but also specific growth factor receptors to promote nerve regeneration. In this study, hyaluronic acid (HA)-based hydrogels modified with poly-L-lysine (PLL) and nogo-66 receptor antibody (antiNgR) (HA-PLL/antiNgR) were administered to rats after lateral hemisection of the spinal cord. Anti-neurofilament positive axons were found to extend into the HA-PLL/antiNgR hydrogel at 8 weeks after implantation, which shows significant difference compared with HA-PLL or blank control group. Electron micrographs of implanted hydrogels showed that there were more cells and normal axons with myelin in the HA-PLL/antiNgR implant than that of HA-PLL hydrogel. The antiNgR grafted on HA hydrogels could be detected for 8 weeks after transplantation in vivo. All of these properties may facilitate HA-PLL/antiNgR hydrogels to become a promising scaffold for repairing spinal cord injury. Nevertheless, both two kinds of modified hydrogels (HA-PLL/antiNgR and HA-PLL) showed remarkable advantages in supporting angiogenesis, and simultaneously inhibiting the formation of glial scar.

Preparation and characterization of MnOOH and β-MnO 2 whiskers

Abstract MnOOH and β-MnO 2 whiskers are obtained for the first time in our work. MnOOH whiskers are chemically synthesized in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The product is obtained under extremely low surfactant concentrations under basic conditions, using MnSO 4 ·H 2 O as the manganese source and ethylamine as the alkali source. After the subsequent heat treatment of MnOOH at 300 °C for 1 h, β-MnO 2 whiskers retaining the similar morphologies are obtained. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetry analysis (TGA) are used to characterize the products.

Synthesis of mesoporous structured material based on tin oxide

Abstract Mesoporous structured tin oxide with high specific surface area was synthesized under acidic conditions at ambient temperature in this study. The synthesis of this material was accomplished using a cationic surfactant (cetyltrimethylammonium bromide: CH 3 (CH 2 ) 15 N + (CH 3 ) 3 Br − ) as the organic supramolecular template and the hydrous tin chloride (SnCl 4 ·5H 2 O) and NH 4 OH as the inorganic precursor and counterion source. X-ray diffraction, thermogravimetric analysis and transmission electron microscopy have been used to characterize the mesostructures formed at room temperature as well as calcined at different temperature. The synthesis procedure strongly influenced the formation of the mesophase. The pore diameters and the surface areas of materials, evaluated from the N 2 -sorption isotherms, indicate average pore diameters of about 22 and 24 A and surface areas about 368 and 343 m 2 /g for calcination at 300 and 350 °C respectively. The formation of the tin oxide mesostructured material was proposed due to the presence of the hydrogen-bonding interactions between supramolecular template and inorganic precursors Sn 4+ and OH − , which were supposed to self-assemble around the cationic surfactant molecules.

Synthesis and characterization of amorphous TiO2 with wormhole-like framework mesostructure

Abstract Using neutral amine surfactant (dodecylamine) as an organic template and neutral inorganic material (tetrabutyl titanate) as a precursor, amorphous TiO2 with wormhole-like framework mesostructure was synthesized with the variation of surfactant-to-Ti alkoxide ratios. Powder X-ray diffraction (XRD), thermogravimetric analysis, Fourier transformed infrared spectra, transmission electron microscopy (TEM), nitrogen adsorption–desorption, and X-ray photoelectron spectroscopy (XPS) have been used to characterize the TiO2 mesostructure. The interaction between surfactant and titanium dioxide was displayed by XPS. The samples exhibit a wormhole-like framework from XRD patterns and TEM images, and high surface area (221 m2/g) for the sample calcined at 450 °C for 2 h. The formation of the titanium oxide mesostructure is proposed to be due to the presence of the interactions between surfactant head group and inorganic precursors prior to hydrolysis, and the condensation under condition favorable for liquid crystal formation.

Non-viral endostatin plasmid transfection of mesenchymal stem cells via collagen scaffolds.

Angiogenesis is critical in the early stage of reparative processes and tissue regeneration, but the persistence of a vascular network may interfere with later transformation/maturation in naturally avascular tissues such as articular cartilage. Our supposition is that the timed delivery of an anti-angiogenic factor in cartilage tissue engineering may facilitate the formation of hyaline cartilage by inducing the regression of vascularization. To this end our overall goal is to prepare an off-the-shelf scaffold containing the gene for a potent anti-angiogenic factor. The objective of this study was to investigate the use of a type I/III collagen scaffold for the non-viral transfection of marrow stromal cells (MSCs, also referred to as mesenchymal stem cells) with the plasmid encoding endostatin. Caprine MSCs were transfected by the naked plasmid alone and plasmid incorporated into a cationic lipid complex in three experiments: 1) cells were transfected in monolayer; 2) monolayer-transfected cells were grown in a collagen sponge-like scaffold; and 3) non-transfected cells were grown in a collagen scaffold containing the naked plasmid and endostatin lipoplex. Independent variables were the passage number of the cells and the plasmid loading. The amount of endostatin released by the cells into the medium was measured using an ELISA. The results demonstrated the overexpression of endostatin by MSCs growing in the endostatin lipoplex-supplemented collagen scaffolds. Endostatin released by the cell-seeded scaffolds reached a peak of 13ng/ml for scaffolds incorporating as little as 20mug of plasmid, at the 3-day collection period ending 5 days post-seeding. The accumulated endostatin synthesis over a 2-week period began to achieve what may be a therapeutic level. MSCs transfected with the endostatin gene in monolayer continued to express the gene when grown in the collagen scaffolds. The results demonstrate the promise of the non-viral delivery of the gene for this potent anti-angiogenic protein to MSCs via a collagen scaffold.

Neutral templating route to mesoporous structured TiO2

A neutral templating route for preparing mesoporous structured TiO2 with high surface area is demonstrated based on self-assembly between a neutral amine surfactant (dodecylamine) and neutral inorganic precursor (tetrabutyl titanate). X-ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron micrographs (TEM) have been used to characterize the mesostructure that forms at room temperature as well as the calcined materials. The pore diameters and the surface areas of materials, evaluated from the N2-sorption isotherms, indicate average pore diameter of about 29.8 A and surface areas about 246 m2/g for calcination at 300 °C.

Preparation and Characterization of Antheraea pernyi Silk Fibroin Based Nanohydroxyapatite Composites

In the present study, Antheraea pernyi silk fibroin (Ap-SF) is employed to regulate the mineralization of hydroxyapatite (HAp) nanocrystals. Calcium phosphate crystals precipitate in the aqueous solution of regenerated Ap-SF at pH 7.4 and room temperature. The samples are charaterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Based on the XRD results, the inorganic phase in the mineralized Ap-SF composites is HAp as small particles with low crystallinity. The FTIR analysis reveals that the HAp crystals are carbonate-substituted HAp and compounded with Ap-SF. The TEM images show mineralized nanofibrils in the composites as rod-like shapes 4—5 nm in diameter. Electron diffraction (SAED) patterns of selected areas of the composites exhibit polycrystalline rings that are ascribed to HAp. SEM images show mineralized Ap-SF composites with several mineralized rods 49—74 nm in diameter.

Synthesis of mesostructured SnO2 with CTAB and hydrous tin chloride

Abstract Mesostructured SnO 2 was synthesized using a cationic surfactant (cetyltrimethylammonium bromide, CTAB) as the organic supramolecular template and the hydrous tin chloride (SnCl 4 ·5H 2 O) and NH 4 OH as the inorganic precursor and counterion source under acidic conditions and room temperature. The resultant products have been examined with X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The formation of the tin oxide mesostructured material was proposed due to the presence of the hydrogen bonding interactions between supramolecular template and inorganic precursors Sn 4+ and OH − , which was supposed to self-assemble around the cationic surfactant molecules.