Xiulan He

Polymeric micelle-templated synthesis of hydroxyapatite hollow nanoparticles for a drug delivery system

Hydroxyapatite (HA) hollow nanoparticles (HNPs) have great potential in nanoscaled delivery devices due to their small size, excellent biocompatibility and expected high capacity. However, the preparation of HA HNPs for their application in a drug delivery system has rarely been reported because HA has a complicated crystal structure and it is difficult to obtain stable HA HNPs with hollows that are only nanoscaled in size. In the present study, HA HNPs were successfully produced through a novel polymeric micelle-templating method. The micelles were structured with completely insoluble Pluronic P123 molecules at cloud point as the core and Tween-60 molecules as the shell by the hydrophobic interaction of the alkyl chains with the insoluble P123 core. The morphology of the HA HNPs could be transformed from nanospheres to nanotubes by adding citric acid as a cosurfactant. The prepared HA HNPs had a much higher drug payload than traditional nanoparticles, using vancomycin as the model drug. Most importantly, the HA nanotubes were coupled with a layer of citrate molecules on the HA surfaces, which could further improve the drug load efficiency and could form an excellent pH-controlled open/closed gate for drug release with the addition of cationic polyelectrolytes.

New Mn+1AXn compounds by thermal explosion in the Al-Cr-Si-C system

Ternary Cr2AlC and Cr3SiC2 compounds—belonging to the family of Mn+1AXn phases (n=1, 2, 3; M is a transition metal, A is an A group element, and X = C or N)—were prepared by thermal explosion in the Cr-Al-Si-C system in air. After mixing, drying, and compaction, the green powders taken in stoichiometric ratios of Cr: Si: C=3: 1: 2 plus 20 wt % Al were thermally exploded at 1100°C in an SHS reactor. The combustion products, Cr2AlC and Cr5-xSi3-zCx+z, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Chromium-aluminum intermetallics and Al4C3 were identified as intermediate products in the synthesis of Cr2AlC. A Cr5-xSi3-zCx+z compound in the system under study was found to exist as Cr3SiC2.