Page 266 - Advances in Textile Biotechnology

Developments in recombinant silk and other elastic protein fi bers 247

sudden slope changes, indicative of major structural transitions of the mate-
rial that are known as ‘yield points’ (Hu et al., 2006).

When post-translational modifications are essential for protein function,
such as protein activity, stability, localization, turn-over, and protein interac-
tions, the study of phosphorylation, glycosylation and sulfation as well as
32

many other modifications is extremely important. Two-dimensional gels, P
labeling, western-blot, immunological methods, protein chips and other

generic strategies based mainly on affinity methods, depending on the event
that it is studied, can be applied for this purpose (Pandey and Mann, 2000).

10.7 Examples and applications of recombinant

protein fibers (silk, elastin, collagen, resilin)

Elastomeric proteins have been identified in a range of biological systems.
The mechanical and biochemical properties of some have been extensively

studied, especially elastin, abductin and flagelliform spider silks and their
potential as biomaterials for industrial and biomedical applications are well
documented (Lyons et al., 2007). From all the biopolymers that commonly
occur as structural elements of biological systems some protein-based bio-
polymers have been employed to mimic and/or improve the structural and
mechanical properties found in their natural sources, in order to be useful

in the textile industry. Biotechnological production of fibers could allow the
preparation of a new generation of high-performance fibers having even

more built-in properties for a variety of textiles-related applications.
With traditional fibers in the textile industry, it is known that only when

continuous single nanofibers or uniaxial fiber bundles are obtained, can
they be employed in numerous applications. Thus, one of the main targets
in obtaining recombinant protein-based polymers for applications in textile
industry is to achieve aligned nanofibers. Several fabrication techniques

such as electrospinning (Huang et al., 2003, Li and Xia, 2004), phase separa-
tion (Yang et al., 2004) and self-assembly (Hartgerink et al., 2001) amongst
others have been employed to produce polymer nanofi bers for different
applications. Most of these techniques are time-consuming or have prereq-
uisites regarding the viscoelasticity or the cohesivity of the material
employed. Therefore, the most popular technique used is electrospinning,
which provides a convenient method for many materials and produces

continuous nanofibers that can be developed for large-scale production
(Nagapudi et al., 2005).
Electrospinning utilizes a high-voltage source to inject charge of a certain
polarity into a polymer solution, which then dries to leave a polymer nano-

fiber mesh. The fibers produced by this process usually have diameters on
the order of a few micrometers down to less than a hundred nanometers
and their structural properties depend on processing parameters such as

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