Biomedical Engineering Reference
In-Depth Information
been recently developed to carry hemoglobin. These copolymers are able to form nanoparticles in
water with a ciliated surface of heparin and are able to maintain the antithrombogenic properties
of heparin and thus inhibit complement activation. Hence, these drug delivery systems are suitable
tools in the treatment of thrombosis oxygen-deprived pathologies. 65 However, as stated above, many
questions remain concerning the intracellular fate of nanoparticles, probably because the answers
differ from one cell line to another and from one cyanoacrylic polymer to another. Whatever the
answer, there is an urgent need to design nanoparticles which will be able to specifi cally deliver
these molecules, either to the cytoplasm or to the nucleus, depending on the target. 66
15.2.7 P OLYURETHANES
Polyurethanes (PUs) consist of urethane linkages and the main backbone is produced by the reaction
between a diisocyanate (aromatic or aliphatic) and polyol, typically polyethylene glycol or polyes-
ter glycol in presence of catalysts, as shown in Figure 15.8. Polyurethanes have extensive struc-
ture property diversity and are extremely favored for biomedical applications, especially for blood
contacting devices. The properties of polyurethanes can be designed and are mainly governed by
the choice of the polyol; however, the diisocyanate exerts some infl uence. Their popularity has been
sustained as a direct result of their segmented block copolymeric character, which endows them
Ethylene glycol
Phthalic acid
HO
OH
HO
OH
HO
OH
C
C
HOOC
COOH
C
C
HOOC
COOH
C
C
H 2
H 2
H 2
H 2
H 2
H 2
(1)
n H 2 O
O
O
O
O
HO
C
H 2
C H 2
O
C
C
O
C H 2
C H 2
O
C
C
O
C H 2
C H 2
OH
n
Polyhydroxyester
O
O
HO
C
H 2
C H 2
O
C
C
O
C H 2
C H 2
OH
+
OCN
C
H 2
N
C
O
D iisocyanate
Component B
n
(2)
Component A
Urethane functional group
O
O
N
N
C
H 2
O
C
C
O
C
H 2
C
H 2
O
C
O
C
H 2
C
O
O
n
m
Polyurethane
FIGURE 15.8
The formation of polyurethanes.
 
 
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