Oxide-based electrocatalysts were investigated as non-platinum cathodes for the oxygen reduction reaction (ORR). Recently, we found that titanium oxide-based compounds produced from oxy-titanium tetra-pyrazino-porphyrazine via oxidation under low oxygen partial pressure exhibited high ORR activity [T. Hayashi et al., ECS Trans., 64(3), 247 (2014)]. However, the mechanism by which the ORR proceeds in the presence of titanium oxide-based catalysts has not yet been analyzed in detail. In this study, the ORR mechanism was investigated based on the Damjanovic model by using a rotating ring disk electrode. The titanium oxide-based catalysts showed high reactivity in the four electron reduction of O 2 .
We investigated the influences on the smooth muscle cells of temporally heated arterial walls in both ex vivo and in vitro study to determine the optimum heat parameter of novel short-term thermal angioplasty, Photo-thermo Dynamic Balloon Angioplasty (PTDBA). Arterial heating dilatation was performed by the prototype PTDBA balloon ex vivo. We found that the smooth muscle cells in the vessel wall were stretch-fixed after the heating dilatation ex vivo. The stretch-fixing rate of these cells was increased with the temperature rise in the balloon of PTDBA from 60 °C to 70 °C. We measured the proliferation rate of the stretch-fixed smooth muscle cells, which were extracted from porcine arteries, on specially designed culture equipment in vitro. It was observed that the proliferation rate was inhibited at 20 % stretching compared to 10 % stretching. We think the stretch-fixing of the smooth muscle cells might not be harmful for PTDBA performances.
We proposed a novel laser-driven short-term heating angioplasty to realize restenosis-suppressive angioplasty for peripheral artery disease. In this study, we investigated the chronic intimal hyperplasia formation after the short-term heating dilatation in vivo, as well as the thermal damage calculation on arterial smooth muscle cells (SMCs). The prototype short-term heating balloon catheter with 5.0, 5.5, 6.0 mm φ in balloon diameter and 25 mm in balloon length were employed. The short-term heating dilatation was performed in porcine iliac arteries with dilatation conditions of 75°C (N=4) and 65°C (N=5) as peak balloon temperature, 18 ± 4s as heating duration, 3.5 atm as balloon dilatation pressure. Four weeks after the balloon dilatation, the balloon-dilated artery segments were extracted and were stained with HE and picrosirius red for histological observation. In the case of 75°C as the peak balloon temperature, neointimal hyperplasia formation was significantly reduced. In this case, the SMCs density in the artery media measured from the HE-stained specimen was 20% lower than that in the reference artery. According to the thermal damage calculation, it was estimated that the SMCs lethality in artery media after the short-term heating angioplasty was 20% in the case of 75°C as the peak balloon temperature. We demonstrated that the short-term heating dilatation reduced the number of SMCs in artery media. We think this SMCs reduction might contribute to the suppression of chronic neointimal hyperplasia.
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