53. Regenerated Fibers from Bovine Serum Albumin (BSA)

Bovine serum albumin was dissolved in water using dithiothreitol as a reducing agent at a pH of 4.7, and the solution obtained was poured onto glass plates. Proteins were dehydrated at 30 °C, and 30 % humidity and fibers were formed by pulling air over the solution at a constant flow rate leading to fibrillation [13Wu]. Fibers obtained were cross-linked with formaldehyde dissolved in methanol and additionally cross-linked again with 0.1 % glutaraldehyde or with EDC. Average length of the fibers obtained was 35 cm, and the diameter of the fibers was between 10 and 20 μm. Figure 53.1 shows the image of the fibers obtained. It was found that the fibers consisted of ordered β-sheets at the ends and with globular regions at the center as seen from the SEM image in Fig. 53.2. However, the structure and properties of the fibers were dependent on protein concentration, pH, degree of cross-linking, and other fiber-forming conditions. Fibers without cross-linking dissolved in water or 50 % methanol but reassembled into original fibers when the solvent was removed. Table 53.1 provides a comparison of the tensile properties of the albumin fibers with Bombyx mori silk. As can be inferred from the table, the albumin fibers have strength similar to that of silk, higher modulus, and similar elongation. Higher amounts of tightly packed β-sheets were suggested to provide good tensile properties to the fibers after cross-linking. Fibers were also dyed using acid dyes and spun into yarns. Pictures of the dyed fibers and yarns spun from the fibers are shown in Fig. 53.3.