Biomedical Engineering Reference
In-Depth Information
CH
2
OH
CH
2
OH
CH
2
OH
CH
2
OH
OH
O
O
O
O
OH
OH
L
-tryptophan NCA
273.15 K
OH
O
O
O
O
NHAc
NHAc
NH
2
n
m
m
n
O
NHCHC
NH
Graft copolymer
CH
2
Chitooligosaccharide
NH
p
Figure 2.34
Preparation scheme of chitosan-poly-l-tryptophan.
methyl trifluoromethanesulfonate). Living poly(2-methyl-2-oxazoline) and poly(isobutyl-
vinyl ether) cation was successfully terminated by surface amino groups on chitosan pow-
der to give the corresponding polymer-grafted chitosan [302].
Cationic chitosan-graft-polycaprolactone (CS-g-PCL) copolymers were synthesized
using the facile one-pot method via ring-opening polymerization of ε-CL onto the hydroxyl
groups of chitosan by using MSA as solvent and catalyst. These graft copolymers could
form spherical nanomicelles with controllable sizes and positive zeta potentials. The water-
insoluble antitumor drug 7-ethyl-10-hydroxy-camptothecin (SN-38) was successfully
encapsulated into these nanomicelles [303]. Their entrapment efficiency, DL, and accumu-
lative drug release could also be controlled by adjusting the grafting PCL content in CS-g-
PCL. In comparison with free SN-38, the SN-38-loaded CS-g-PCL nanomicelles showed
prolonged drug release profiles, improved drug stability against hydrolysis under physi-
ological conditions, and decreased cytotoxicity against the L929 cell line. These results
indicated that nanomicelles based on cationic CS-g-PCL might be a candidate as drug car-
rier for SN-38 and other hydrophobic drugs.
2.11.7 Copolymerization of Preformed Polymer by the grafting onto Method
Telechelic polymers have been defined as those containing one or more functional end
groups that have the capacity for selective reaction to form bonds with another molecule.
Unlike the classic grafting techniques where the grafted chain is grown from the trunk
polymer by the continual addition of monomer to the growing chain end, grafting onto
OH
O
OH
R
O
O
O
N
O
HO
n
O
O
HN
HO
MeOSO
2
CF
3
, MeCN
N
CH
3
NH
2
n
O
R
R= -CH
3
, -CH
2
CH
3
Poly(2-alkyl-2-oxazoline) grafted chitosan
Chitosan
Figure 2.35
Synthesis of chitosan-polypeptide bioconjugate via grafting of living poly(2-alkyl-2-oxazoline) onto chitosan.
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