Application of Chitosan-Based Biomaterials in Tissue Engineering - Chitosan Based Hydrogels: Functions and Applications - page 435

Figure 9.28
Representative micrographs of chondrocytes and chitosan scaffold interactions: (a) the large arrow indicates the
junctional complex between the chitosan scaffold and the cell. TEM micrograph (×20,000); and (b) the thin
arrows indicate the cell membrane in interaction with the chitosan scaffold. TEM micrograph (×12,000).
chitosan scaffolds can enhance the diffusion of cells and nutrients into the center of scaf-
folds. And chitosan allowed cell surfaces to gain resistance and attach to neighboring struc-
tures tightly. Chondrocyte membranes were strongly attached on the chitosan surface.
Chondrocytes have junctional complexes that consist of plaques and filaments ( cf. Figure
9.28) [134]. Moreover, when a concentration of 12-25 million cells/cm 2 is seeded in chitosan
porous scaffolds, a lot of cartilage-specific ECMs can form and the mechanical strength of
this scaffold-chondrocytes increased over time from 9.6 kPa at 14 days of 3D culture to
14.6 kPa at 28 days [135]. However, chondrocytes-laden porous chitosan scaffolds used to
repair articular cartilage defects may proceed slower than the rate of cartilage regeneration
[136]. And the ability of chitosan to maintain a round cellular morphology has been previ-
ously demonstrated for short periods of cell culture times (e.g., from 48 h to 2 weeks), but
not for the prolonged cell culture time [137]. Therefore, pure chitosan scaffolds are not
appropriate for producing artificial cartilage. Collagen, CAGs, polysaccharide, and syn-
thetic polymer are introduced into the chitosan network to modulate the physicochemical
properties, degradation behavior and mechanical properties, and bioactivities.
9.5.3.2.1 Chitosan-Collagen Scaffolds
In order to further produce the biomimetic environment for chondrocytes, chitosan scaf-
folds blended with collagen (or gelatin) or other GAGs were synthesized. The 3D porous
chitosan-type II collagen scaffold can mimic the cartilage-specific ECM. It can improve
the proliferation and differentiation of chondrocytes and synthesize type II collagen [138].
Recently, collagen is replaced by gelatin to prepare the 3D porous scaffold. The degraded
products of chitosan-gelatin are involved in the synthesis of articular cartilage, such as
chondroitin sulfate, dermatan sulfate, HA, keratin sulfate, and type II collagen [139]. The
chitosan-gelatin scaffolds gradually experienced degradation, and cartilage tissues were
developed, matured, and formed relatively homogenous cartilage [140].
9.5.3.2.2 Chitosan-CAG Scaffolds
GAGs are the main components of cartilage-specific ECM, and chitosan has a protective
effect against GAG hydrolysis by their specific enzymes. Therefore, chitosan-GAG