Biomedical Engineering Reference
In-Depth Information
DNA carriers because PEG reduces particle sizes of complexes and PVP prevents albumin
from interaction with complexes [203-205]. The quaternized galactosylated chitosan also
has cellular recognition ability and the possibility of gene delivery [206,207]. Such selective
targeting of the substrate delivery to hepatocyte cells is feasible because hepatocytes are
the only cells that possess large numbers of high-affinity cell-surface asialoglycoprotein
receptors that can bind to asialoglycoproteins.
Sialic acid is the most prevalent sugar of the glycolipids and glycoproteins on the mam-
malian cell surface and is the key epitope recognized as essential for a number of patho-
genic infections. Moreover, sialic acid-containing polymers have been shown to be potent
inhibitors of hemagglutination of human erythrocytes by influenza viruses. Sashiwa et al.
[209] prepared sialic acid-bound chitosan as a new family of sialic acid-containing poly-
mers using
p
-formylphenyl-
a
-sialoside [208] by reductive N-alkylation. Since sialic acid-
bound chitosan was insoluble in water, successive N-succinylations were carried out to
obtain the water-soluble derivative
N
-succinyl-sialic acid-bound chitosan (Figure 2.22).
Specific binding of wheat germ agglutinin with lectin was shown in the presence of
OH
OH
O
O
O
O
HO
HO
0.96
NHAc
NH
2
0.04
COOH
OH
OH
NaCHBH
3
,
AcOH/H
2
O/MeOH,
rt, 1 day
HO
O
O
AcHN
CHO
HO
OH
OH
OH
O
O
O
O
O
HO
O
HO
HO
NHAc
NH
x
0.96-
x
0.04
NH
2
COONa
HO
OH
HO
(Water insoluble)
OO
AcHN
HO
O
i AcOH/H
2
O/MeOH, rt, 1 day
ii 0.5 M NaOH, rt, 2 h
O
O
OH
OH
OH
O
O
O
O
O
O
HO
HO
HO
NH
NHAc
H
0.96-
x
0.04
COONa
HO
OH
O
O
O
NaOOC
HO
AcHN
HO
(Water soluble)
Figure 2.22
Synthesis of sialic acid-chitosan and its
N
-succinylation.
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