Nowadays, biopolymers such as keratins are widely used in biomedicine due to their low toxicity, biocompatibility, and biodegradability. At the molecular level, keratins differ from other structural proteins by a high content of disulfide bonds, which provide the formation of a compact three-dimensional structure resistant to biological and chemical degradation. Native keratins are highly ordered, whereas, recovered keratins are characterized by a flexible structure with more accessible functional groups. A characteristic feature of solubilized keratins is their ability to polymerize; therefore, they are widely used to create biomaterials. The extraction of keratins from natural fibers is an important step to the development of functional biomaterials. However, this process is complicated by the presence of a large number of intramolecular and intermolecular disulfide bonds in keratins. That is why keratin extraction by breaking the intermolecular disulfide bonds while preserving the covalent bonds of the polypeptide chain is necessary. The goal of our study was to estimate the different methods of solubilized keratin obtaining. In the experiments, samples of different types of wool and human hair were used. Various methods of keratin extraction were applied. The yield of solubilized keratin (%) was calculated from the ratio of the weight of the lyophilized keratin extract and the initial weight of fibers. The molecular mass of recovered keratins was evaluated by SDS-PAAG electrophoresis in the Laemmli buffer system. An analysis of the efficiency of keratin extraction has shown that solubilized keratin yield ranged from 32% to 51% and depended on the composition of the extraction mixture. Electrophoretic analysis of all keratin extracts obtained by various methods confirmed the presence of two bands, which according to the molecular weight corresponding to I and II types of proteins of intermediate filaments. The presence of these proteins provides self-assembly into complex structures.

Background. Keratins are natural biopolymers with a wide range of applications in the field of biotechnology. Materials and Methods. Extraction of keratins was performed by a modified Nakamura method using 250 mM DTT. The protein concentration in the supernatant was determined by Bradford method. The protein composition was studied by their electro­phoretic separation in a polyacrylamide gel in the presence of sodium dodecyl sulfate. The films were made by casting. The surface characteristics of the films were determined using a scanning electron microscope REMMA-102. The elemental composition of the films was determined using an X-ray microanalyzer. Results. The protein concentration in the supernatant was 3.75 mg/mL. After using dithiothreitol in the extraction mixture, we obtained proteins of intermediate filaments with a molecular weight of 40–60 kDa and a low Sulfur content. In the low molecular weight region, we obtained keratin-associated proteins with a molecular weight of 10–30 kDa and a high content of Sulfur. These proteins belong to fibrillar proteins, which can be used as a matrix for the creation of new keratin-containing biocomposites with a wide range of applications in reparative medicine and tissue engineering. Based on the obtained keratin extract, polymer films with and without the addition of glycerol were made. Scanning electron microscopy revealed that glycerol provided the film structure with homogeneity and plasticity due to the accumulation of moisture after the fixation by water vapor. The X-ray microanalysis of films revealed such elements as Sodium, Silicon, Sulfur, Potassium. Among the detected elements, Sulfur has the largest share that is due to the large number of disulfide bonds in the keratin molecule. Conclusions. The polymer keratin films with the addition of glycerol demonstrated better mechanical properties and can be used in biomedicine.

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Determination of the characteristics of regenerated keratin obtained from human hair, development of keratin-based films, and studing their surface morphology and adsorption capacity. Methods. Keratins were extracted by sulfitolysis. The structure of regenerated kera tin was studied by IR spectroscopy, thermogravimetry, and electrophoresis. Keratin-based films were made by casting. Their biocompatibility was analyzed in the adsorption test by incubation in human serum. Scanning electron microscopy was used to evaluate the surface morphology of the films. Results. The regenerated keratin is represented mainly by proteins of intermedi ate filaments and is characterized by better thermal properties than the native one. The keratinbased films had a pronounced relief structure. The adsorption test shows the ability of the films to adsorb albumin from human serum on their surface. Conclusions. The mild extraction of keratins by sulfitolysis ensures the preservation of their native properties and the ability of keratin-based films to form bonds with blood proteins.