Biomimetic Polysaccharides and Derivatives for Cartilage Tissue Regeneration - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 8

direct cell function. Thus the following sections focus on several potential
natural polysaccharides-based scaffolds for cartilage tissue engineering
applications.

1.4 Natural Polysaccharides for Cartilage Tissue

Engineering

Polysaccharides are a class of materials which are of rapidly growing
interest to researchers in the fi eld of biomaterial science. There are several
factors which have specifi cally contributed to the importance of polysac-
charide-based biomaterials such as: (i) Understanding of the critical role
of saccharide moieties in cell signaling schemes and immune recognition.
(ii) New and effective synthetic techniques to functionalize biologically
active oligosaccharides, thereby allowing improvement in the properties
of polysaccharide for functional performance. (iii) The signifi cant increase
of tissue engineering research pointing to the need for new materials with
specifi c, controllable biological activity and biodegradability. Additionally,
one of the most important properties of polysaccharides, in general, is
their ability to form hydrogels either by hydrogen bonding or ionic inter-
actions. Hydrogel formation can occur by a number of mechanisms and is
strongly infl uenced by the types of monosaccharide involved, as well as
the presence and nature of substituent groups. Hydrogels have potential
application in tissue engineering, particularly in cartilage tissue regenera-
tion. The following sections are focused on four different types of polysac-
charides-based materials, namely chitin and chitosan, HA, alginate, starch
and cellulose-based materials for potential cartilage tissue engineering
applications.

1.4.1 Chitin and Chitosan (CS)-based Materials

CS is a partially de-acetylated derivative of chitin found in arthropod
exoskeletons. Structurally, CS is a linear polysaccharide consisting of
b (1, 4) linked D-glucosamine residues with a variable number of randomly
located N -acetyl-glucosamine groups. It thus shares some characteristics
with various glycosaminoglycans (GAGs) and hyaluronic acid present in
articular cartilage. GAG analogy as components of a cartilage tissue scaf-
fold appears to be a logical approach for enhancing chondrogenesis, and
cartilage regeneration. Depending on the source and preparation proce-
dure, the average molecular weight may vary in the range from 50 to 1000
kDa. The degree of deacetylation of commercially available CS varies from
50% to 90%. This is a semicrystalline polymer and the degree of crystallin-
ity is a function of the degree of deacetylation. Minimum crystallinity is
achieved at intermediate degrees of deacetylation. CS is normally insoluble