Keratin films for ocular surface reconstruction

Human amniotic membrane (AM) is frequently used as a substrate for ocular surface reconstruction. Its disadvantages (e.g., reduced transparency and biomechanical strength, heterogeneity depending on donor) create the need for standardized alternatives. Keratin from hair or wool has been proposed as an appropriate material for producing films or cell cultivation scaffolds. The current study was performed to develop transparent, stable and transferable films based on human hair keratin that support cellular adhesion and proliferation. The films were engineered by a multi-step procedure including keratin extraction, neutral and alkaline dialysis, drying and a curing process. Keratin films were investigated by SDS-PAGE, SEM and X-ray analyses. Furthermore, swelling and water absorption of the films were studied, as were tensile strength and light transmission (UV/VIS). Finally, the growth behavior of corneal epithelial cells on the keratin films and AM was estimated in proliferation studies. In addition, we assessed the seeding efficiency and cell detachment behavior during trypsinization. The film-forming process resulted in transparent films composed of nanoparticulate keratin structures. The film characteristics could be varied by changing the protein composition, adding softening agents or varying the curing temperature and duration. Based on these findings, an optimized protocol was developed. The films showed improved light transmission and biomechanical strength in comparison to AM. Furthermore, cell behavior on the films was similar to that found on AM. We conclude that keratin films may represent a new, promising alternative for ocular surface reconstruction.