Biomedical Engineering Reference
In-Depth Information
12.4.2
Analysis of Enzymatic PLA Depolymerization
The experimental and analytical study of endogenous depolymerization is contin-
ued to cover degradation of PLA [17, 18]. PLA used for the experiment was poly(l -
lactide). Figure 12.10 shows the GPC patterns of PLA given in terms of retention
time versus voltage. The fi gure also shows the baselines of the GPC patterns. Figure
12.11 shows standards of molecular weight versus retention time. The fi gure also
shows the least-squares approximation that fi ts the standards. Figure 12.12 shows
the weight distribution of PLA before and after enzymatic degradation for 5 and
67 h based on the shift according to the baselines shown in Figure 12.10, the
transformation according to the least-squares approximation shown in Figure 12.11,
and scaling according to the residual amounts. An inverse problem was formulated
to determine the degradation rate for which the solution of the initial value problem
also satisfi es the weight distribution after incubation for 5 h. PLA was solved in
chloroform and emulsifi ed by sonication for enzymatic degradation. As the time
elapsed, chloroform was lost by evaporation, resulting in reduced degradation rates.
In previous studies [18], the temporal change of degradability was considered, and
a temporally dependent degradation rate was incorporated into the endogenous
depolymerization model. The endogenous depolymerization is studied in this
chapter. A mathematical model of endogenous depolymerization, which covers the
previously proposed models as special cases, is introduced.
It is shown that a general model can be transformed to a form to which previ-
ously developed techniques are applicable. Techniques to solve an inverse problem
*10
88
Before degradation
87
Baseline before degradation
After 5 h degradation
86
Baseline after 5 h degradation
After 67 h degradation
85
Baseline after 67 h degradation
84
83
82
81
80
79
78
0 1 2 3 4 5 6 7 8 91011
min
12 13 14 15 16 17 18 19 20
Figure 12.10
GPC patterns of PLA given in terms of retention time versus voltage [16, 17].
The baselines are also shown.
