Methods of keratin extraction from wool and hair and prospects of their application in biomedicine and bioengineering

The present article gives the overview of scientific information on the hair structure, the structural and functional properties of keratins, and methods of their extracting from the natural fibers. The article substantiates an importance of keratin extraction by breaking the disulfide bonds and converting the keratin into a soluble form while maintaining covalent bonds. Such extraction preserves the native properties of these proteins, that ensures their further use as functional biomaterials. The examples of such properties are: resistance of keratin to the effects of chemical and biological factors (due to high frequency of disulfide bonds that make a large number of chemical modifications of proteins possible) and high biocompatibility and low cytotoxicity of keratin-based preparations (due to a similarity of keratin to the extracellular matrix of biological tissues). The keratin-based materials, obtained by this way and then lyophilized, can form fibrillar structures when a particular solvent is selected. The methods of keratins extraction, as well as the efficiency and electrophoretic profiles of obtained extracts, were also analyzed. The purposeful extraction is carried out by the methods based on oxidation, reduction, and sulfitolysis reactions. The oxidation reactions of keratin are irreversible and cause the oxidation of cysteine residues to cysteic acid with the formation of keratosis. At the same time, keratin is obtained due to a reduction reactions. As a result of the reversible process of sulfitolysis, the S-sulfonate anion is formed. The paper also considers promising applications of extracted keratin in biomedicine and bioengineering. The biomedical technologies are related to the effective treatment of hair pathologies. The second area is the creation of keratin-based biomaterials with a wide range of applications, such as tissue engineering, reparative medicine, textile industry, agriculture, cosmetology, and production of cleaning equipment. The third area of keratins application is the identification of a person. Such application makes an important contribution to the anthropological research and forensic science. High resistance of hair proteins to adverse environmental conditions makes this area very promising.