Biomedical Engineering Reference
In-Depth Information
4.2.3.4 Diepoxide-Cross-Linked Chitosan
A diepoxide-based bifunctional linker is used to cross-link the chitosan chains via the
reactive amino groups on the chitosan backbone. The schematic representation of the
cross-linking method is shown in Figure 4.9. The cross-linking chitosan network film with
1,4-butanediol diglycidyl ether increases the hydrophilicity of the surface and shows excel-
lent cytocompatibility for chondrocyte cells [90].
Inoue and coworkers [109] prepared the chitosan network using the diepoxy-PEG as a
cross-linker (
cf.
Figure 4.10).
The swelling behavior of the diepoxy-PEG-cross-linked chito-
san is found to rely greatly on the
M
W
of PEG in diepoxy-PEGs and weight percentage of
the diepoxy-PEGs. The higher the diepoxy-PEG weight percentage, the lower the equilib-
rium swelling ratio for certain diepoxy-PEG. And the higher the
M
W
of PEG in diepoxy-
PEG, the higher the equilibrium swelling ratio for the same weight percentage of the
diepoxy-PEGs. Kulkarni et al. [110] have reported that cross-linking chitosan by PEG is
accomplished by a novel yet simple method using formaldehyde. The free amino groups
of chitosan, when treated with formaldehyde form intermediates of Schiff's bases
(-N=CH
2
), readily undergo addition with the hydroxyl groups of PEGs [111]. Moreover,
these cross-linking networks show a significant swelling ratio in both the simulated
OH
O
O
O
O
O
O
HO
+
O
NH
2
1.4-Butanediol diglycidyl ether
(excess)
Chitosan
OH
O
OH
O
O
HO
O
O
O
NH
HO
NH
OH
O
OH
O
And
O
O
O
HO
Structure 2
Chitosan units with reactive
epoxide moiety
NH
HO
O
O
O
OH
Structure 1
Cross-linked chitosan units
Figure 4.9
Schematic represenation of the strategy for cross-linking with bifunctional epoxides. (From Subramanian, A.
and Lin, H. Y. 2005.
J Biomed Mater Res
75A: 742-753. With permission.)
Search WWH ::
Custom Search