Mykhaliuk V. The biochemical characteristics of keratins and keratin-based models of biomaterial.

The aim of the study was to compare various methods for the extraction of keratins from wool and human hair, their analysis, and creation of biomaterials of functional purpose on the basis of extracted proteins. We found that the optimal conditions for the extraction of keratins from wool fibers of different types are the following: the temperature in the range of 50–60 °C, pH 8.5, and the duration of solubilization of proteins in the range of 48–72 hours. The use of 2-mercaptoethanol and dithiothreitol as reducing agents significantly increased the efficiency of keratin extraction from wool fibers, with the content of soluble protein in the extracts under conditions of using dithiothreitol was twice as high as when using 2-mercaptoethanol. As a result of the extraction of human hair proteins, it was found that the most effective reducing agent is sodium metabisulfite. The results of the electrophoretic separation of keratins demonstrated that proteins of intermediate filaments (IF) of types I and II and low molecular weight keratin-associated proteins (CAP) can be extracted from wool fibers under the effect of different reducing agents. Similar bands of keratin were found in extracts from human hair under the use of dithiothreitol. We obtained a slightly different electrophoregram of the protein extract using sodium metabisulfite. In this case, we found only IF proteins. Such results may indicate either that this type of a reducing agent is not suitable for the extraction of CAP of human hair or that it is needed to choose another type of electrophoretic separation. The structure of the extracted keratins was confirmed by IR spectroscopy. We found that the use of 3% aqueous solution of reduced keratin for the treatment of wool fibers increases the strength of wool fibers. No changes in the fiber tone were discovered. The treatment with 3 and 5% protein solutions was accompanied by the redistribution of keratoses in wool fibers towards an increase in the alpha fraction and a decrease in the proportion of matrix proteins. The use of 3 and 5% aqueous solution of reduced keratin for the treatment of wool fibers did not significantly affect the solubility of wool in 0.1 n NaOH solution and 4 n HCl, but the strength increased as compared to the control. We found that the treatment of wool fibers, modified with hydrogen peroxide, contributed to the improvement of the specific electrical conductivity of the fibers. The results of the study of the adsorption properties of keratins indicate that the maximum efficiency of heavy metals elimination by the biosorbent based on wool fibers was observed at pH 6.0 for both Cadmium ions and Lead ions. The best sorption properties for Cadmium and Lead ions were discovered for wool fibers treated with sodium bisulfite. It was found that under the same conditions of model experiments, the efficiency of adsorption of Lead ions by biosorbents based on wool fibers is significantly higher than for Cadmium ions. When studying polymer films based on human hair keratin, we found that the combination of a protein solution with glycerol improves their mechanical properties and promotes surface homogeneity. Films made only from an aqueous solution of keratin were brittle, and the structure of their surface was characterized by a pronounced relief, which was confirmed by scanning electron microscopy. Serum protein adsorption test confirmed the biocompatibility of keratin films, so they can be successfully used in tissue engineering. Thus, the studies made it possible to determine the optimal parameters for the extraction of keratins from wool fibers and human hair, which provide maximum production of regenerated protein.