Application of Chitosan-Based Biomaterials in Tissue Engineering - Chitosan Based Hydrogels: Functions and Applications - page 410

factors. In general, molecular chain structure of chitosan, chemical composition and stiff-
ness of chitosan-based biomaterials, and spatial architecture of scaffolds will influence
these interactions. Moreover, different kinds of cells exhibit different cell responses to
chitosan-based biomaterials.
9.3.1 effect of Chitosan Chain Structure
Interactions between chitosan and cells have been attributed to nonspecific electrostatic
interactions between protonated amine groups and negatively charged carboxylate and
sulfate groups found in cell surface proteoglycans [34]. Therefore, structure parameters,
especially the DD of chitosan, take very important roles when cells contact with chitosan-
based biomaterials. Most cell behaviors, such as attachment, proliferation, migration, mor-
phology, and differentiation, exhibit different characters due to different chain structures
of chitosan.
9.3.1.1 Attachment
Cell adhesion is an important previous process for sequent cell growth, cell migration, and
cell differentiation. When DD increases, the charge density of chitosan is enhanced, thus
reinforcing adhesion [35]. Moreover, as little as 10% differences in the extent of DD of
chitosan samples have a significant influence on the adhesion to chitosan substrates by
cells in culture [36]. Chitosan with high DD has more glucosamine units and more amino
groups, which results in cells getting attracted to it via electrostatic interactions. In addi-
tion, higher-DD chitosan films may also localize more growth factors in the serum near
cells, therefore increasing the chances of the growth factor binding to its receptor on the
cell surface [37].
9.3.1.2 Proliferation
Cell proliferation behaviors are influenced by the DD, depending on cell type. Whatever
the DD of chitosan is, fibroblasts show low cell proliferation [35] owing to the extremely
high adhesion of fibroblasts to chitosan-based biomaterials [38]. However, all chitosans
with different DDs can support the proliferation of osteoblasts. No relationship was found
between normal human bone cell proliferation and chitosan molecule structure [37].
Keratinocytes and hamster kidney cells are both reported to grow more on chitosan films
than on fibroblasts and the proliferation increases considerably with increasing DD [39,40].
Buffalo embryonic stem-like cells attached and proliferated better on 88% DD and 95% DD
scaffolds than on 70% DD scaffolds and there are no significant differences between 88%
and 95% DD chitosan scaffolds [6,41]. The discrepancies in these results could be attributed
to either the different cell types used in the experiments or the mechanism of cell adhe-
sion to chitosan surfaces. Different DDs result in different amounts of amine groups
present at the surface. Cell-specific differences in the amounts and types of negatively
charged surface molecules could result in cell-specific affinities for chitosan with differ-
ent DDs [42].
9.3.1.3 Migration
For fibroblasts, d-glucosamine (GlcN) is found to reduce migratory activity, while N- acetyl-
d-glucosamine (GlcNAc) is not found to influence the migratory activity [43] and the con-