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Biomedical subjects

Xiaoming Sun

Publications and source records attributed to Xiaoming Sun.

15 recordsLinked to original sources
PubMed2006

FeCo/graphitic-shell nanocrystals as advanced magnetic-resonance-imaging and near-infrared agents.

Nanocrystals with advanced magnetic or optical properties have been actively pursued for potential biological applications, including integrated imaging, diagnosis and therapy. Among various magnetic nanocrystals, FeCo has superior magnetic properties, but it has yet to be explored owing to the problems of easy oxidation and potential toxicity. Previously, FeCo nanocrystals with multilayered graphitic carbon, pyrolytic carbon or inert metals have been obtained, but not in the single-shelled, discrete, chemically functionalized and water-soluble forms desired for biological applications. Here, we present a scalable chemical vapour deposition method to synthesize FeCo/single-graphitic-shell nanocrystals that are soluble and stable in water solutions. We explore the multiple functionalities of these core-shell materials by characterizing the magnetic properties of the FeCo core and near-infrared optical absorbance of the single-layered graphitic shell. The nanocrystals exhibit ultra-high saturation magnetization, r1 and r2 relaxivities and high optical absorbance in the near-infrared region. Mesenchymal stem cells are able to internalize these nanoparticles, showing high negative-contrast enhancement in magnetic-resonance imaging (MRI). Preliminary in vivo experiments achieve long-lasting positive-contrast enhancement for vascular MRI in rabbits. These results point to the potential of using these nanocrystals for integrated diagnosis and therapeutic (photothermal-ablation) applications.

Animals↗
PubMed2006

Use of carbonaceous polysaccharide microspheres as templates for fabricating metal oxide hollow spheres.

A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.

Crystallography, X-Ray↗
PubMed2006

Microstructure-hardened silver nanowires.

To exploit the novel size-dependent mechanical properties of nanowires, it is necessary for one to develop strategies to control the strength and toughness of these materials. Here, we report on the mechanical properties of silver nanowires with a unique fivefold twin structure using a lateral force atomic force microscopy (AFM) method in which wires are held in a double-clamped beam configuration. Force-displacement curves exhibit super elastic behavior followed by unexpected brittle failure without significant plastic deformation. Thermal annealing resulted in a gradual transition to weaker, more ductile materials associated with the elimination of the twinned boundary structure. These results point to the critical roles of microstructure and confinement in engineering the mechanical properties of nanoscale materials.

Journal Article↗
PubMed2005

Hollow carbonaceous capsules from glucose solution.

An easy hydrothermal method was developed for preparing hollow carbonaceous capsules with reactive surface layer and tunable void size, and shell thickness through a hydrothermal method at 180 degrees C, using only the anionic surfactant sodium dodecyl sulfate (SDS) and glucose as starting material. Ag nanoparticles of less than 10 nm were loaded onto the surface of capsules under ambient condition. Products were characterized with TEM, SEM, and FT-IR spectra. The process is green, cheap, and easy. Since no toxic materials were used in preparation and as-prepared capsules a shared reactive surface layer and a stable carbonaceous framework, the capsules might find application in fields such as biochemistry, pharmaceutics, and clinical diagnostics.

Journal Article↗
PubMed2005

Surface enhanced Raman scattering effects of silver colloids with different shapes.

By solution-based method, three kinds of silver colloids, self-assembled nanowires, triangular nanoplates and quasispherical nanoparticles, have been synthesized. TEM studies revealed that they exposed different crystal planes, such as {111} crystal planes to triangular nanoplates, mainly {100} and {111} planes to self-assembly nanowires. Hereby, do the distinct shapes and crystal planes have an impact on the surface enhanced Raman scattering (SERS)? The great differences of the SERS spectra of rhodamine B at these Ag colloids confirmed that the shapes and crystal planes of silver have great effect on Raman enhancement, especially the crystal planes.

Colloids↗
PubMed2005

Ag@C core/shell structured nanoparticles: controlled synthesis, characterization, and assembly.

Silver nanoparticles with tunable sizes were encapsulated in a carbonaceous shell through a green wet chemical route-the catalyzed dehydration of glucose under hydrothermal condition. In this one-pot synthesis, glucose was used as the reducing agent to react with Ag+ or Ag(NH3)2+, and it also served as the source of carbonaceous shells. The effects of hydrothermal temperature, time, and the concentrations of reagents on formation of the final nanostructures were systematically studied. The presence of competitive molecules poly(vinyl pyrrolidone) was found to be able to relieve the carbonization process, to incorporate themselves into carbonaceous shell, and to make the carbonaceous shell colorless. All these approaches provided diverse means to tailor the Ag@C nanostructures. By evaporation of the solvents gradually in a moist atmosphere, the monodispersed nanoparticles could self-assemble into arrays. Transmission electron microscopy, scanning electron microscopy, and UV-vis extinction spectra and surface-enhanced Raman spectra were used to characterize the core/shell nanostructures. These Ag@C core/shell nanoparticles have hydrophilic, organic-group-loaded surfaces and characteristic optical properties, which indicated their promising applications in optical nanodevices and biochemistry.

Journal Article↗
PubMed2005

Crystal structures, anisotropic growth, and optical properties: controlled synthesis of lanthanide orthophosphate one-dimensional nanomaterials.

The fundamental understanding of the relationship between crystal structure and the dynamic processes of anisotropic growth on the nanoscale, and exploration of the key factors governing the evolution of physical properties in functional nanomaterials, have become two of the most urgent and challenging issues in the fabrication and exploitation of functional nanomaterials with designed properties and the development of nanoscale devices. Herein, we show how structural and kinetic factors govern the tendency for anisotropic growth of such materials under hydrothermal conditions, and how the crystal structure and morphology influence the optical properties of Ln3+-doped nanocrystals. The synthesis of phase-pure and single-crystalline monoclinic, hexagonal, and tetragonal one-dimensional LnPO4 nanostructures of different aspect ratios by means of kinetically controlled hydrothermal growth processes is demonstrated. It is shown that the tendency for anisotropic growth under hydrothermal conditions can be enhanced simply by modifying the chemical potentials of species in the reaction solution through the use of carefully selected chelating ligands. A systematic study of the photoluminescence of various Eu3+-doped lanthanide phosphates has revealed that the optical properties of these nanophosphors are strongly dependent on their crystal structures and morphologies.

Journal Article↗
PubMed2004

The successive development of acute myeloblastic leukemia, secondary non-Hodgkin's lymphoma and secondary myeloid/natural killer cell acute leukemia in a single patient.

We report a very rare case of a female patient who was initially diagnosed with acute myeloid leukemia (AML) M2 who achieved complete remission (CR) after chemotherapy. Six years later she was still in continuous complete remission from leukemia, but developed a right nasal obstruction and based on the nasal and nasopharynx biopsies, a secondary B cell non-Hodgkin's lymphoma was diagnosed and treated with chemotherapy and involved field radiotherapy. One year and seven months after the completion of therapy she presented with fever, dyspnea and leukocytosis. The blasts were now negative for myeloperoxidase and immunophenotyping showed that they were positive for CD13 and CD56. Now the diagnosis of a secondary myeloid/NK cell acute leukemia was made. The patient died of multiorgan failure 1 month after the onset of leukemia. As far as we know, no other such patient has been described in the English literature until now.

Adult↗
PubMed2003

Synthesis and characterization of ion-exchangeable titanate nanotubes.

Titanate nanotubes were synthesized under hydrothermal conditions. The optimized synthesis (100-180 degrees C, longer than 48 h), thermal and hydrothermal stability, ion exchangeability and consequent magnetic and optical properties of the titanate nanotubes were systematically studied in this paper. First, nanotubes with monodisperse pore-size distribution were prepared. The formation mechanism of the titanate nanotubes was also studied. Second, the thermal and hydrothermal stability were characterized with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR), and Raman spectroscopy. Results showed that sodium ions played a significant role in the stability of the frameworks. Third, the selective ion exchangeability was demonstrated with a series of ions. The ion substitution also enlarged the BET surface area of the titanate nanotubes to 240 m(2) x g(-1). Combination of these two features implied that these nanotubes might be functionalized by substitution of different transitional-metal ions and consequently used for selective catalysis. Magnetism, photoluminescence, and UV/Vis spectra of the substituted titanate nanotubes revealed that the magnetic and optical properties of the nanotubes were modifiable.

Journal Article↗
PubMed2002

Large-scale synthesis of sodium and potassium titanate nanobelts.

A low-temperature solution-based synthetic method was developed for the large-scale synthesis of one-dimensional nanostructures of alkali titanates. Two kinds of highly pure ribbonlike titanates were synthesized successfully in gram quantities without introducing any templates or catalysts. The structure and composition of the titanates were characterized by XRD, HRTEM, and EDX. The chemical and physical properties were preliminarily characterized, and some distinctive properties were observed.

Journal Article↗
PubMed2002

Self-assembling vanadium oxide nanotubes by organic molecular templates.

Vanadium oxide nanotubes were synthesized as the main product by hydrothermal self-assembling from ammonium metavanadate (NH(4)VO(3)) and organic molecules as structure-directing templates. Several kinds of templates including primary amines (C(n)H(2n+1)NH(2)), alpha,omega-diamines (H(2)N[CH(2)](n)NH(2)), and quaternary ammonium salt (CTAB) were demonstrated to be appropriate for the formation of nanotubes. The morphologies and structures of the nanotubes were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and thermal gravimetric analysis (TGA). The nanotubes were found forming together with the layered structures and the sheetlike structures. On the basis of the growth mechanism of WS(2) nanotubes proposed by our group, a possible rolling mechanism was proposed, which might be a suitable general formation mechanism for types of nanotubes from lamellar structures.

Journal Article↗
PubMedDate not supplied

The Shanghai case: A qualitative evaluation of community health reform in response to the challenge of population ageing.

Shanghai's health care system is facing a serious challenge of an ageing population, as 14% of its 17 million residents are 65 or older. In 2000, a community health reform was implemented to provide comprehensive and continuous primary care to community residents with a focus on seniors. The study employed the theoretical framework of examining primary care in terms of the constellation of its four unique elements (first contact, comprehensiveness, longitudinality and coordination) and three healthcare components (structure, process and outcome). The study aimed to evaluate the extent to which the reform has achieved its process goals and how the organizational context influenced the level of implementation. In-depth interviews with 25 health providers, 15 seniors and four community leaders were carried out. The study found that the Shanghai community health reform has improved the structure and process of primary care regarding first contact, comprehensiveness and longitunality. However, the reform is constrained by structural barriers on seniors' financial access to resources and the capacity of primary care providers. The previous organization system also constrains the reform in CHCs financing and administration. The Shanghai case illustrates that a broad societal view has to be taken when analysing health reforms, which requires the involvement of multiple sectors including the government, health providers and health consumers.

Aged↗