1. Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura, Nishikyo‐ku Kyoto 615‐8510 Japan
2. Japan Science and Technology Agency (JST) The Exploratory Research for Advanced Technology (ERATO) Bio‐Nanotransporter Project Katsura Int'tech Center Katsura, Nishikyo‐ku Kyoto 615‐8530 Japan
3. Department of Material‐based Medical Engineering Institute of Biomaterials and Bioengineering Tokyo Medical and Dental University 2‐3‐10 Kanda‐Surugadai Chiyoda‐ku Tokyo 101‐0062 Japan