Biomedical Engineering Reference
In-Depth Information
engineered tissue consists of three basic elements, which are struc-
tural scaffolds, a source of cells, and a culture condition, including
a cell signal. A three-dimensional scaffold takes roles of an extracel-
lular matrix (ECM) analog, which functions as a necessary template
for host infiltration and a physical support to guide the differentia-
tion and proliferation of cells into the targeted functional tissue or
organ.
2
,
3
The scaffolds require biocompatibility and biodegradabil-
ity for being used in the body, an open-pore structure connected to
pores, a surface for attachment, proliferation, and differentiation of
cells, and also su
cient mechanical properties for support of cells
and treatment.
4
The materials of the scaffolds are natural polymers
such as collagen, hyaluronic acid, chitosan, alginate, etc., and these
polymers can be su
cient for the above-mentioned scaffold condi-
tions. Natural polymers as materials of scaffolds have been studied
bymanyresearchers becauseoftheirrichexistenceinnature.Some
have been used in clinicaltrials.
5
In recent years, considerable attention has been given to
chitosan-based materials and their applications in the field of tissue
engineering.
2
,
6
-
8
It is well known that chitosan is the second-most
abundant polysaccharide on earth, after cellulose. Chitosan can be
obtained by deacetylation of chitin, which is isolated from exoskele-
tons of crustaceans and also from cell walls of fungi or insects.
9
Chitosan has great potential as a biomolecule by the presence
of reactive functional groups, gel-forming ability, high adsorption
capacity, biodegradability, intrinsic antibacterial nature, minimal
foreign body reaction, and nontoxicity.
10
Chitosan is also able to be
molded in various geometries and forms, such as porous structures,
suitablefor cell ingrowths andphenotype.
In this chapter, the application and fabrication of porous chi-
tosan sponges, beads, and thermo-gelling hydrogel scaffolds are
introduced.
23.2 Chitin and Chitosan
Chitosan (poly[
4)-2-amino-2-deoxy-D-glucose]) is formed
through the
N
-deacetylation of chitin (poly[
β
-(1
→
β
-(1
→
4)-2-acetamido-
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