Chitosan Composites for Biomedical Applications: An Overview - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 15

Chapter 2
Chitosan Composites for Biomedical applications:
an overview
R. Ramya, Z. Ansar Ali, and P.N. Sudha
iNtroduCtioN
Natural polymers received great attention in the biomaterials field; their structural
similarities with biological macromolecules make them easily recognized by the bio-
environment and therefore easily metabolized into noncytotoxic residues and naturally
eliminated. Chitin is one of the most abundant polysaccharides and can be found in
the exoskeleton of crustaceans which can be obtained from the shell waste of the
crab, shrimp, crawfish processing industries, various invertebrates, and lower plants.
Chitosan is one of chitin's derivatives, achieved by N-deacetylation of chitin. It is one
of the major components used in vascular surgery, tissue culture, and tissue regenera-
tion as a hemostatic agent (Muzzarelli et al., 1986). Improving the fragile nature of
films and membrane permeability are the key challenges that need to be addressed for
improving chitosan as a biomaterial. In addition, chitosan is expected to be useful in
the development of composite materials such as blends or alloys with other polymers,
since chitosan has many functional properties (Japanese Chitin and Chitosan Society,
1995). Chitosan is a biopolymer which has many interesting properties that have been
utilized in many pharmaceutical applications (Patel and Amiji, 1996). There have been
many studies on the blends of chitosan with various kinds of polymers (Guan et al.,
1998; Hasegawa et al., 1992; Kim et al., 1992; Xiao et al., 2000; Yao et al., 1996) in
order to obtain some improved properties.
Natural silk fiber is a fiber obtained from silkworms. Silk has been used as a high
quality fiber material, because it has characteristics such as high tensile strength, pe-
culiar luster, and excellent dyability. Silk fibroin (SF) is a fibrous protein that is com-
posed of 17 amino acids and its main components are nonpolar ones such as glycine,
alanine, and serine. A silk fiber has a structure with two strands of fibroin surrounded
by a sericin wall. By preparing in various forms such as a membrane, powder, gel, and
aqueous solution, the SF is used in various fields such as food, cosmetics, and medical
goods because it has excellent biocompatibility and does not give any adverse effect
to surrounding tissues. Silks have been investigated as biomaterials due to the success-
ful use of silk fibers from Bombyx mori as suture material for centuries (Moy et al.,
1991). Functional differences among silks of different species and within a species are
a result of structural differences due to differences in primary amino acid sequence,
processing, and the impact of environmental factors (Vollrath and Knight, 2001). Silks
represent a unique family of structural proteins that are biocompatible, degradable,
and mechanically superior, offer a wide range of properties, are amenable to aqueous