Some properties of keratin biomaterials: Kerateines

Keratins are a family of structural proteins that can be isolated from a variety of tissues. “Soft” keratins are cytoskeletal elements found in epithelial tissues while protective tissues such as nails, hooves, and hair are composed of “hard” keratins. Hard keratins have been the subject of biomaterials investigations for more than three decades. Numerous methods exist for denaturing these proteins which are characterized by a high sulfur content and extensive disulfide bonding, under either oxidative or reductive conditions, extracting them from tissue and processing them into various physical states such as gels, films, coatings, and fibers. Kerateines or keratoses (oxidatively or reductively derived, respectively), alone or in combination with other biomaterials, have been tested in a small number of systems to demonstrate feasibility for medical applications such as wound healing, bone regeneration, hemostasis, and peripheral nerve repair. These investigations have shown generally good compatibility with cells and tissues, but the focus of prior investigations has been fairly narrow, and as a result there is relatively little published data on the general behavior of keratin biomaterials in biological systems beyond cell culture assays. The goal of this study was to produce a reduced form of keratin biomaterial, kerateine, using a typical and well-published technique, and characterize several aspects of its behavior that may have implications to its general use as a biomaterial. Kerateines were extracted from human hair, fabricated into gels and porous scaffolds, characterized, and placed into biological systems to determine their interactions with cells and tissue. Initially, the proteins were analyzed for molecular weight and amino acid content, as well as their ability to facilitate cell adhesion and proliferation. Crosslinked hydrogels were investigated for their hydrolytic stability in vitro; the micro-architecture and in vivo tissue response of lyophilized gels was also studied. These experiments both confirmed and expanded earlier findings that kerateines demonstrate excellent compatibility in biological systems.