Chitosan-based scaffolds possess some special properties for use in tissue engineering. First, Chitosan can be formed as interconnected-porous structures by freezing and lyophilizing of chitosan solution or by processes such as an “internal bubbling process (IBP)”where CaCO3 is added to chitosan solutions to generate chitosan–CaCO3 gels in specific shapes by using suitable molds (Chow and Khor, 2000). The interconnectedporous
structure is very important, so that numerous cells can be seeded, migrate into the inside, increase the cell number and should be supplied by sufficient amounts of nutrient. The porous structure of chitosan is a promising characteristic for the development and optimization of a variety of tissue scaffolds and regeneration aids. Regulation of porosity and pore morphology of chitosan-based scaffolds is critical for controlling cellular colonization rates and organization within an engineered tissue. In addition, angiogenesis required for some scaffold application scenarios can be affected by scaffold porosity and pore morphology (Madihally and Matthew, 1999).
Second, the cationic nature of chitosan also allows for
pH-dependent electrostatic interactions with anionic
glycosaminoglycans (GAG) and proteoglycans distributed
widely throughout the body and other negatively
charged species. This property is one of the important
elements for tissue engineering applications because
numbers of cytokines/growth factors are known to be
bound and modulated by GAG including heparin and
heparan sulfate. A scaffold incorporating a chitosan–
GAG complex may serve means of retaining and concentrating
desirable factors secreted by colonizing cells.
Moreover, Nishikawa et al. (2000) reported that chitosan,
structurally resembling with GAG consisting of longchain,
unbranched, repeating disaccharide units, regarded
to play a key role in modulating cell morphology, differentiation,
and function.
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