Silk fibroin (SF), which offers the benefits of biosafety, biocompatibility, and mechanical strength, has potential for use as a good biomedical material, especially in the tissue engineering field. This study investigated the use of SF biomaterials as a wound dressing compared to commercially available collagen materials. After human fibroblasts (WI-38) were cultured on both films and sponges, their cell motilities and gene expressions related to wound repair and tissue reconstruction were evaluated. Compared to the collagen film (Col film), the SF film induced higher cell motility; higher expressions of genes were observed on the SF film. Extracellular matrix production-related genes were up-regulated in WI-38 fibroblasts cultured on the SF sponges. These results suggest that SF-based biomaterials can accelerate wound healing and tissue reconstruction. They can be useful biomaterials for functional wound dressings.

Background: Recently, silk fibroin-based biomaterials have received attention for application in tissue engineering and drug delivery systems. The usefulness of heat sterilization methods for silk fibroin-based biomaterials was investigated in this study as all biomaterials are required to undergo a sterilization process when they are used in medical devices. Methods: The influence of wet and dry heating on the properties of fibroin molecules in silk fibroin sponges was investigated by measurements of solid-state ¹³C cross-polarization/magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analyses, strength tests, and cell proliferation/migration assays. Results: ¹³C CP/MAS NMR spectra of wet-heated sponges revealed no changes in the molecular structure below 50 °C. However, above 60 °C, the crystalline structure of the silk proteins transitioned from silk I to silk II; the silk II:silk I ratio increased with temperature. In contrast, dry heating (below 190 °C for up to 180 min) induced no structural changes in the fibroin molecules. These results indicate that, although autoclave sterilization (121 °C for 20 min) induces structural changes in silk fibroin sponges, no such changes are observed with the dry-heat sterilization (180 °C for 30 min). Sterilized sponges with a silk I structure can be obtained using dry-heat method during sterilization. Moreover, the structural differences between the wet- and dry-heated silk fibroin sponges did not influence their interaction with fibroblasts. Discussion: This study indicates that both autoclaving and dry heating are acceptable sterilization methods for silk fibroin-based sponges as the scaffold. In particular, dry heating maintains the stability of the secondary structure of the sterilized silk fibroin-based biomaterials.