Silver (Ag)-doped hydroxyapatite (HAp) agglomerates containing 0.15%, 1.5% and 4.3% mole % of silver among total cations, respectively, were evaluated in vitro and in vivo to explore their potential application as a bone filler with antibacterial properties. The 0.15% Ag-doped HAp was mildly cytotoxic, whereas the 1.5% and 4.3% Ag-doped HAps were moderately cytotoxic in the standard agar overlay cytotoxicity assay. The in vivo test was carried out by implanting Ag-HAps in artificial bone defects at the periapical area of both mandibular 1 st molar of rats and no remarkable cytotoxicity was found unlike what was observed in the in vitro data. All of the implanted Ag-doped HAp particles, regardless of their Ag contents, allowed appropriated cellular proliferation and favorable bone repair without remarkable inflammatory reaction through 3 week healing periods, in spite of the mild delay in organization of fibrin and inflammatory reaction with the 4.3% Ag-doped HAp at the early healing phase. They supported well new bone formation with osteointegrative and osteoconductive properties. The results suggest that HAps doped with Ag up to 4.3 % of total cations can be applied for repair of infection-associated bony defects.
We present a synthesis of single-walled carbon nanotubes(SWNTs) for enhancement of parallel-alignment and density using chemical vapor deposition with methane feed gas. As-purchased ST-cut quartz substrates were heat-treated and line-patterned by electron-beam lithography in order to grow SWNTs with parallel alignment. We investigated the effects of various synthesis parameters such as catalyst oxidation, reduction, and synthesis conditions in order to enhance both tube density and degree of parallel alignment. The condition of 1 Å of Fe catalyst film, atmospheric oxidation at 750ºC for 10 min, reduction under 400 Torr for 5 min, and growth at 865ºC under 300 Torr yields 33 tubes/10µm, which is the highest tube density with parallel alignment. Based on the results of atomic force microscope and Raman spectroscopy, it was found that SWNTs have diameter range of 0.8-2.0 nm. We believe that the present work would contribute to the development of SWNTs-based flexible functional devices.
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