Biomedical Engineering Reference
In-Depth Information
OH
OH
OH
NH
2
NH
2
NH
2
O
HO
O
HO
O
O
O
O
O
HO
HO
O
O
O
NH
2
NH
2
NH
2
OH
OH
OH
HO
HO
HO
NH
2
NH
2
NH
2
OH
O
OH
O
OH
O
HO
O
O
O
O
O
O
OH
OH
OH
O
NH
2
NH
2
NH
2
HO
HO
OH
OH
OH
NH
2
NH
2
NH
2
HO
O
HO
O
O
O
O
O
O
HO
HO
O
O
O
N
N
N
OH
OH
OH
HO
HO
HO
N
N
N
O
OH
OH
O
OH
O
HO
O
O
O
O
O
O
OH
OH
OH
O
NH
2
NH
2
NH
2
HO
HO
+
OH
OH
OH
N
N
N
HO
O
HO
O
O
O
O
O
O
HO
HO
O
O
O
N
N
N
OH
OH
OH
HO
HO
HO
N
N
N
OH
O
OH
O
O
OH
HO
O
O
O
O
O
O
OH
OH
OH
O
N
N
N
HO
HO
Figure 4.6
Sketch map of chitosan cross-linked by GA. (From Webster, A., Halling, M. D., and Grant, D. M. 2007.
Carbohydr
Res
342: 1189-1201. With permission.)
involves the replacement of the ester group on the G molecule by a secondary amide link-
age. The reaction is complicated by the oxygen radical-induced polymerization of genipin
that occurs once the heterocyclic compound has formed. The environmental pH condition
plays an important role in influencing the cross-linking reactions for the preparation of
genipin-cross-linked chitosan.
Figure 4.8
shows the conformation of the network segments
of the genipin-cross-linked chitosan network consisting of short cross-linking units of
cyclic bridges and long cross-linking units of polymerized genipin [104].
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