1. Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
2. Regenerative Medicine Technology Dept. Healthcare R&D Center, Asahi Kasei Corporation, 2-1 Samejima, Fuji-shi, Shizuoka 416-8501, Japan