Abstract: We examined the safety of silk fibroin in the subcutaneous tissues. In addition, we macroscopically and histopathologically evaluated its healing effect on the full-thickness wounds in hairless dogs. We prepared 3 types of matrices including amorphous silk fibroin films, and á-and â-type silk fibroin powder. No toxicity was found in the sites injected with silk fibroin solutions. Macroscopically, silk fibroin films had accelerating effects on wound repair, as compared with occlusive dressings (dried porcine skin and hydrocolloid dressings). Histopathological examinations revealed that silk fibroin films facilitate reepithelialization and the formation of granulation tissues, collagens and elastic fibers. The sites treated with the á-type silk fibroin powder were faster in wound repair than those treated with the â-type silk fibroin powder. The á-type silk fibroin powder absorbed excessive exudate. Microscopically, there are epidermal and dermal regeneration in the sites treated with the á-type silk fibroin powder. These results show that silk fibroin is inert in biological tissues, indicating excellent biocompatibility. Silk fibroin films facilitate reepithelialization, remodeling of connective tissues and collagenization. The á-type fibroin powder is a wound dressing that regulates excessive exudate from the wound and provides a proper moist environment. These results suggest that silk fibroin is a useful dressing material in veterinary clinical medicine
