In-vivo anti-tumor activity of a novel poloxamer-based thermosensitive in situ gel for sustained delivery of norcantharidin.

In order to develop a novel norcantharidin (NCTD) delivery system with slow drug release and specific targeting characteristics, we have developed a Poloxamer-based NCTD thermosensitive in situ gel. The evaluation of the characteristics of this system using both in vitro and in vivo methods was previously reported. However, its anti-tumor activity in vivo is still not confirmed. Thus, the potential anti-tumor activity and relative mechanism were investigated in a murine H22 hepatoma model. Tumor-bearing mice were treated with different dose of NCTD thermosensitive in situ gel (3.3 mg/kg, 6.6 mg/kg, and 9.9 mg/kg, respectively by intra-tumor injection once every three days, totaling 5 injections per group. Control groups included untreated or NCTD injection (2.2 mg/kg, qd) or blank in situ gel. The expression of vascular endothelial growth factor (VEGF) and CD44 in tumor tissue was examined by immunohistochemistry (IHC) staining. Treatment with middle or high dose of NCTD thermosensitive in situ gel significantly induced tumor regression, inhibited VEGF and CD44 expression and improved survival of tumor-bearing mice. The efficacy of NCTD thermosensitive in situ gel is higher than that of free NCTD injection. Therefore, NCTD thermosensitive in situ gel is a novel NCTD delivery approach for chemotherapeutic treatment of cancer.

Atomistic nucleation and growth mechanism for single-wall carbon nanotubes on catalytic nanoparticle surfaces.

We demonstrate an atomistic nucleation and growth mechanism for single-wall carbon nanotubes (SWNTs) on catalytic nanoparticle surfaces based on a core-shell model. We show by ab initio calculations that strain relief between the metal core and carbon shell plays a crucial role in facilitating the hexagonal tubular growth. The incipient nucleation begins with the formation of a hemispherical fullerene cap by a size-selected core-shell bonding process which is followed by a repeated phase-separating growth mode with increasing energetic stability via periodic pulsatile strain relief along the tubular growth pathway. These results provide an excellent account for experimental observations and shed new light on the origin and underlying dynamics of SWNT growth.

A synthetic method for transition-metal chalcogenide nanocrystals.

In this paper, we prepared a series of chalcogenide semiconductor nanocrystals in controllable shape and size via a facile wet route using metal nitrates and sulfur or selenium powder as precursors and octadecylamine (ODA) as solvent. The as-obtained chalcogenides included CdS, MnS, Ag(2)S, PbS, Cu(1.8)S, Bi(2)S(3), ZnS, Zn(x)Cd(1-x)S, as well as Ag(2)Se, Cu(2-x)Se, CdSe, MnSe. Furthermore, these cyclohexane-soluble monodisperse nanocrystals were assembled to water-soluble colloidal spheres and the adjustment of assembly orderliness has been achieved by controlling the experimental parameters. The general synthesis and assembly of chalcogenide semiconductors provide ideal building blocks for various potential applications.

Direct thermal decomposition of metal nitrates in octadecylamine to metal oxide nanocrystals.

We have developed a method for the synthesis of metal oxide nanocrystals with controllable shape and size, which is based on the direct thermal decomposition of metal nitrates in octadecylamine. Mn3O4 nanoparticles and nanorods with different lengths were synthesized by using manganese nitrate as the decomposition material. Other metal oxide nanocrystals such as NiO, ZnO, CeO2, CoO, and Co3O4 were also prepared by this method. These nanocrystals were then assembled into 3D colloidal spheres by a surfactant-assisted self-assembly process. Subsequently, calcination was carried out to remove the surfactants to obtain mesoporous metal oxides, which show large pores, good crystallization, thermally stable pore mesostructures, and potential applications in various fields, especially in catalysis and lithium-ion batteries.

Two-stage rotation mechanism for group-V precursor dissociation on Si(001).

We report ab initio identification of initial dissociation pathways for Sb4 and Bi4 tetramer precursors on Si(001). We reveal a two-stage double piecewise rotation mechanism for the tetramer to ad-dimer conversion involving two distinct pathways: one along the surface dimer row via a rhombus intermediate state and the other across the surface dimer row via a rotated rhombus intermediate state. These two-stage double piecewise rotation processes play a key role in lowering the kinetic barrier by establishing and maintaining energetically favorable bonding between adatoms and substrate atoms. These results provide an excellent account for experimental observations and elucidate their underlying atomistic origin that may offer useful insights for other surface reaction processes.

Carrier-induced magnetic ordering control in a digital (Ga,Mn)as structure.

With the full potential linearized augmented plane method, we theoretically investigated the carrier-induced magnetization reversal in digital (Ga,Mn)As heterostructures with varying distance between the two Mn layers along with the distribution and concentration of external carriers. The presence of external holes induces switching from the antiferromagnetic to ferromagnetic state when d(Mn-Mn)=16.96 A, whereas the addition of electrons produces no significant effect. We demonstrate a possibility to separately control T(c) and magnetic reversal in digital (Ga,MN)As alloys.

First principles calculation of anomalous Hall conductivity in ferromagnetic bcc Fe.

We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. This dc conductivity has the same origin as the well-known magneto-optical effect, and our result accounts for experimental measurement on Fe crystals with no adjustable parameters.