Biomedical Engineering Reference
In-Depth Information
H
O
O
O
OH
HO
HO
HO
a
b
1
(
α
-CD)
2
3
c
OH
OH
OH
OH
O
O
O
O
O
d
O
HO
O
O
HO
NH
HO
N
HO
n
n
NH
2
NH
2
m
m
O
O
HO
HO
5
4
Figure 6.6
Preparation of chitosan-g-cyclodextrin via the reductive amination strategy. Reagent and conditions: (a) LiH-
LiI, DMSO, and then allyl bromide; (b) O3 in 50% aqueous MeOH; (c) chitosan in acetate buffer (pH 4.4); and (d)
NaBH
3
CN in acetate buffer (pH 4.4). (From Tojima, T. et al. 1998.
J Polym Sci A Polym Chem
36: 1965-1968. With
permission.)
6.2.3 graft Copolymer of Chitosan
Another way of improving chitosan performance and enlarging its potential applications
is chemical modification of chitosan by grafting vinyl monomer(s) [41] and initiating the
monomer's free radical polymerization.
One of the more intensively investigated monomers is
N
-isopropylacrylamide (NIPAM),
whose polymer is well known to have a thermally reversible property. It has a lower
critical solution temperature (LCST) of around 32°C in aqueous solution, that is, it dis-
solves in water below the LCST and precipitates from aqueous solution above the LCST [35].
CH
3
CH
3
CH
CH
2
O
CH
CH
2
OH
CH
2
O
CH
2
OH
O
OH
O
OH
HOOCCH
2
OH
2
C
OH
EDC
O
OH
+
n
O
OH
NH
CCH
2
OH
2
C
NH
2
n
OH
CM
β
-CD
O
HPCH
HPCH-
g
-CM
β
-CD
Figure 6.7
Preparation of chitosan-g-cyclodextrin by using EDC coupling reaction. (From Mani, P. 2008.
J Biomater Appl
23:
5-35. With permission.)
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