Biomedical Engineering Reference
In-Depth Information
2. Synthesis of Poly(aspartamide)s
For the rational design of synthetic poly(aspartamide)s, as drug carriers, the
feasibility of their synthesis, subsequent conjugation with therapeutic
compounds, and enzymatic degradability should be considered. The synthetic
method of poly(aspartamide)s, by polymerization of NCA monomers can not
only produce high molecular weight polymers but also control molecular weight,
while it is very difficult due to several complicated reaction and purification
steps for the synthesis.[16, 17] Another synthetic approach is by aminolysis of
PSI, where PSI is prepared by acid-catalyzed polycondensation of L-aspartic acid
and used as an intermediate material for the preparation of synthetic
poly(aspartamide)s. Though high molecular weight PSI was conventionally
prepared by polycondensation of L-aspartic acid in a large amount of phosphoric
acid as the catalyst and solvent under reduced pressure, it is too difficult to
remove considerable amount of phosphoric acid.[18] In 1997, a new synthesis
was developed by polycondensation of L-aspartic acid using a catalytic amount
of phosphoric acid in a mixed solvent of mesitylene and sulforane, where the
O
O
NH
2
C
acid cata
lyst
CH
C
HO
N
n
OH
O
O
L-aspartic acid
Poly(succinimide)
ethanolamine
NH
4
OH
NaOH
O
O
O
NH
NH
NH
ONa
NH
O
n
n
n
NH
CH
2
CH
2
OH
O
O
Poly(aspartic acid)
Poly(asparagine)
Poly[(2-hydroxyethyl)aspartamide]
Fig.
2.
Synthetic
scheme
of
poly(aspartic
acid),
poly(asparagines),
and
poly[(2-
mydroxyethyl)aspartamide] from L-aspartic acid.
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