Safety of Silk-elastin Sponges in Patients with Chronic Skin Ulcers: A Phase I/II, Single-center, Open-label, Single-arm Clinical Trial oleh Kazuo Noda, MD, PhD, Katsuya Kawai, MD, PhD, Yoshitaka Matsuura, MD, Toshiko Ito-Ihara, MD, PhD, Yoko Amino, PharmD, Mika Ushimaru, PhD, Akemi Kinoshita, Harue Tada, PhD, Hiroyasu Abe, PhD, Satoshi Morita, PhD, Akira Shimizu, MD, PhD, Itaru Tsuge, MD, PhD, Michiharu Sakamoto, MD, PhD, Naoki Morimoto, MD, PhD