Extraction of keratin particles as intact protein sequences from chicken feathers and their characterization

Keratins are ubiquitously occurring proteins, which are the structural basis of e.g. hairs, nails, and even skin. In detail, the Stratum corneum (SC) barrier function depends on the keratin-filled corneocytes and the surrounding lipid matrix. Our focus was on keratins as artificial substituents and model substances for/on damaged or irritated SC with limited barrier properties. We were able to extract full-sequenced, intact fibrous proteins from chicken feathers using a urea and L-cysteine-based extraction method, with the intention to avoid the application of irritating sodium dodecyl sulfate and final keratin precipitation. Keratin particles with a high degree of water-solubility were received. Typical characteristics of feather keratins were further verified: FT-IR technique revealed the presence of α-helical structures and β-sheets. Applying gel electrophoresis techniques, a main fraction was observed with a molecular mass of 10 kDa. Finally, mass spectrometry identified feather keratins with 10.1 kDa and 98 amino acids, indicating the complete protein sequences. In aqueous dispersion, a DLS study revealed that keratin particles were in a colloidal state with an average particle size of about 300 nm and a zeta potential of –40 mV. Cell proliferation and cell vitality tests on juvenile native human dermal fibroblasts and native human epidermal keratinocytes cells presented the physiological effect of the keratin particles. A final ex vivo study on hen´s eggs revealed no irritative potential of the keratin, which was crucial for the intended usage on damaged or irritated SC.