Submitted to: Textile Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2012
Publication Date: 1/1/2013
Citation: Cardamone, J.M., Tunick, M.H., Onwulata, C.I. 2013. Keratin sponge/hydrogel part 1. fabrication and characterization. Textile Research Journal. 83(7):661-670.
Interpretive Summary: There is a pressing need to open new markets for wool to position it in fields related to new product development of biomaterials to replace petroleum-based materials. New products in the form of sponge materials with the potential to absorb, retain, and deliver moisture and active agents, were produced from U.S. domestic fine- and coarse-grade wool. Oxidation and reduction methods were applied to form distinct sponge materials having the appearances of rough mat-like and smooth gel-like absorbent materials with different mechanical behaviors. Mechanical testing showed that these keratin sponge materials remained strong with intact structure under applied strain to imply a high degree of keratin molecular association. The ability to give up moisture with applied heat without degradation proved them suitable for exposure to a broad temperature range. They were characterized in mechanical testing as having characteristics of a liquid and a solid to make them suitable for a broad range of end-uses. In their production from wool fibers to keratin sponge state, these materials maintained the chemical composition of intact wool to suggest that they possess wool’s high potential for chemical modification. With their high potential for moisture uptake and release, the potential to react as solids or liquids, and the high capacity for water-borne retention of substances, there is high potential for keratin sponge as stand-alone products and new uses in topical applications for the biotechnological, biomedical, pharmaceutical and related fields.
Technical Abstract: Keratin sponge/hydrogel products formed by either the oxidation or reduction of U.S. domestic fine- or coarse-grade wool exhibited distinctively different topologies and molecular weights of 6- 8 kDa and 40-60 kDa, each with unique macro-porous structure and microstructural behaviors. The sponge/ hydrogels retained the amino acid character, peptide content, and protein homologues of intact keratin. The ability of the sponge/hydrogels to react with anionic or cationic species was confirmed by differential dyeing with anionic and cationic dyes. Differential scanning calorimetry provided evidence of molecular organization and association and the adherent presence of occluded moisture from measurements of thermal parameters: glass transition; peak temperature and enthalpy of water removal; thermal degradation temperature and enthalpy of degradation (Tg, Tw, delta Hw, Tt, and delta Ht). High delta Hw and Tg and the absence of denaturation peaks proved evidence of stable, highly crosslinked molecular association. Low delta Hw indicated high plasticity with inferred greater capacity to absorb and retain moisture. SAOSA rheology applied to stretch internal bonds to evaluate the relationship between the solid part (storage modulus, G’) and the viscous part (loss modulus G”) as a function of applied strain, characterized the sponge/ hydrogels as covalently crosslinked (not entangled) networks, with viscoelastic properties typical of both liquids and solids, which maintain their structural integrity under strain without loss of microstructure. These keratin sponge/ hydrogels proved suitable for selection as construction materials for biotechnological and biomedical applications in medical, pharmaceutical and related fields.