O o d h e a d p u b L i s h I n g L i m I t e d

14.5
Advanced applications of wool keratins
If wool is considered as a source of a durable biopolymer material for which
application development to parallel synthetic polymers is possible, at least in
principle, then the possibilities for advanced applications of wool are boundless.
Although the practical reality has thus far fallen short of the enormous
potential of the material, a wide range of historic and current advanced uses
of wool keratin have been developed.
Early applications included reconstituted fibres, developed in the 1940s
(Wormell and Happey, 1949), in which fibrous keratin proteins were isolated
from a wool source and spun into smooth, fine fibres for textile applications.
This utilised emerging expertise in wet spinning gained in the rayon industry;
however, the reconstituted fibres fell short of meeting the physical requirements
of the target textile applications, and presumably failed to develop for this
reason. While ambitious in its intentions, this work involved first creating a
soluble form of the wool keratin prior to reforming it into a solid of the
desired shape. Repeating that first step, of making the tough insoluble wool
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fibre into a soluble keratin protein (or in most cases a peptide mixture) as a
result of hydrolysis, has proved an essential first, and in many cases only,
step in the development of other industrial and consumer uses of wool keratin.
Keratin peptides, made soluble through the harsh processes of hydrolysis,
have formed a core part of many familiar products including fire fighting
foams, as protein foam concentrates, as moisture retardants in building plaster,
and most significantly as hair and skin care products. While there is some
variation in preferences in different regions of the world, the use of keratins
for enhancing the cosmetic properties of the hair and skin is extensive.
Japan, South America and parts of Europe have particularly favoured the use
of keratins in these applications. Given that the substrate to be enhanced, be
it hair or skin, is either almost entirely keratin or at least keratin-rich, the
natural affinity and active characteristics of the keratin protein, to strengthen
hair, to smooth and moisturise skin, far outperform the plant-derived proteins
often used to achieve the same effects. Familiar brands on supermarket and
pharmacy shelves contain keratin for this purpose, with at least a portion of
this derived from wool. Some market analysts project that keratin protein
use in cosmetic applications will be as high as US$69 million by 2011
(Freedonia, 2000).
Beyond cosmetic enhancement of skin and hair is biological enhancement
of skin and other tissues. The use of keratin materials for medical applications,
to enhance the repair of tissue both within and on the surface of the body, has
been the subject of both research and commercial endeavour. Applications
examined have included hard tissue repair, in which the robust character of
the keratins is used to integrate with damaged bone to provide a better
healing outcome (Peplow et al., 2003; Dias et al., 2006; Tachibana et al.,
2006). Although keratin is not intrinsic to bone, its use for this purpose is
well suited. If bone is considered as a fibrous protein–mineral composite
(largely collagen and the calcium mineral hydroxyapatite), then use of a
fibrous protein–mineral composite, in which the fibrous protein is derived
from an alternative source, for bone augmentation, is understandable. Further,
bone tissue is remodelled in the body on a relatively short time frame.
Consequently a temporary construct familiar in structure and composition to
the body that fills a temporary role to facilitate the remodelling process is
highly desirable. The ability to prepare controlled porosity constructs using
keratin protein and calcium minerals has been documented (Peplow et al.,
2003). The importance of composition and structure for biomimetic
stimuluation of bone growth response has also been detailed (Ripamonti,
2004) and a powerful combination of structure and biology is possible as a
result of using versatile keratin biopolymers in bone augmentation.
In addition, the repair and enhancement of soft tissue has provided a
substantial focus of research and development. Keratin has been considered
as the biological material to replace areas of soft tissue, such as intervertebrate
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discs in the spine, or to fill spaces for tissue enhancement, such as breast or
other soft tissue augmentation (Smith et al., 2001). Further to tissue repair is
the use of keratin as a construct in the area of regenerative medicine. There
is rapidly expanding interest in cell therapies, including stem cells, for the
development of tissue constructs, and this is driving a need for biologically
acceptable matrices to provide a framework on which to grow regenerated
tissue. Keratin has been explored for this purpose and found to possess
suitable characteristics (Furth et al., 2007). In addition to using the material
as a flexible and versatile biocompatible biopolymer to create the appropriate
shaped constructs, the favourable biological environment would appear to
assist in the growth of tissue, and potential in nerve regeneration has been
identified (Sierpinski et al., 2008).
Yet another field of medical development where advanced applications of
wool keratin have been developed is wound care. Wound dressings derived
from wool keratin have been created and applied successfully to a range of
wound types (Van Dyke et al., 2000), from acute to chronic, with positive
healing outcomes reported (Kelly et al., 2007). Keratin protein is a fundamental