title: Tunable Keratin Hydrogels for Controlled Erosion and Growth Factor Delivery.
abstract: Tunable erosion of polymeric materials is an important aspect of tissue engineering for reasons that include cell infiltration, controlled release of therapeutic agents, and ultimately to tissue healing. In general, the biological response to proteinaceous polymeric hydrogels is favorable (e.g., minimal inflammatory response). However, unlike synthetic polymers, achieving tunable erosion with natural materials is a challenge. Keratins are a class of intermediate filament proteins that can be obtained from several sources, including human hair, and have gained increasing levels of use in tissue engineering applications. An important characteristic of keratin proteins is the presence of a large number of cysteine residues. Two classes of keratins with different chemical properties can be obtained by varying the extraction techniques: (1) keratose by oxidative extraction and (2) kerateine by reductive extraction. Cysteine residues of keratose are "capped" by sulfonic acid and are unable to form covalent cross-links upon hydration, whereas cysteine residues of kerateine remain as sulfhydryl groups and spontaneously form covalent disulfide cross-links. Here, we describe a straightforward approach to fabricate keratin hydrogels with tunable rates of erosion by mixing keratose and kerateine. SEM imaging and mechanical testing of freeze-dried materials showed similar pore diameters and compressive moduli, respectively, for each keratose-kerateine mixture formulation (∼1200 kPa for freeze-dried materials and ∼1.5 kPa for hydrogels). However, the elastic modulus (G') determined by rheology varied in proportion with the keratose-kerateine ratios, as did the rate of hydrogel erosion and the release rate of thiol from the hydrogels. The variation in keratose-kerateine ratios also led to tunable control over release rates of recombinant human insulin-like growth factor 1.
authors.affiliation: Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.|Department of Biomedical Engineering, University of Akron , Auburn Science and Engineering Center 275, West Tower, Akron, Ohio 44325, United States.
authors.forename: Trevor R
authors.initials: TR
authors.lastname: Ham
authors.affiliation: Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Lee
authors.affiliation: Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.
authors.forename: Sangheon
authors.initials: S
authors.lastname: Han
authors.affiliation: Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.
authors.forename: Salma
authors.initials: S
authors.lastname: Haque
authors.affiliation: Department of Food Science and Technology, The Ohio State University , 2015 Fyffe Court, Columbus, Ohio 43210, United States.
authors.forename: Yael
authors.initials: Y
authors.lastname: Vodovotz
authors.affiliation: Department of Food Science and Technology, The Ohio State University , 2015 Fyffe Court, Columbus, Ohio 43210, United States.
authors.forename: Junnan
authors.initials: J
authors.lastname: Gu
authors.affiliation: KeraNetics, LLC , 200 East First Street, Box 4, Suite 102, Winston-Salem, North Carolina 27101, United States.
authors.forename: Luke R
authors.initials: LR
authors.lastname: Burnett
authors.affiliation: KeraNetics, LLC , 200 East First Street, Box 4, Suite 102, Winston-Salem, North Carolina 27101, United States.
authors.forename: Seth
authors.initials: S
authors.lastname: Tomblyn
authors.affiliation: Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Saul
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D055119:Elastic Modulus; D006197:Hair / Q000737:chemistry; D006801:Humans; D020100:Hydrogels / Q000737:chemistry*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007633:Keratins / Q000737:chemistry*; D008422:Materials Testing; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; C583557:IGF1 protein, human; D007334:Insulin-Like Growth Factor I; D007633:Keratins