Biomedical Engineering Reference
In-Depth Information
Fig. 13
In vitro hemocompatibility of solution-cast P3HB, P3HB-18%4HB, and P4HB
films. Activation of
a
cellular coagulation (release of platelet factor 4),
b
plasmatic co-
agulation (release of prothrombin fragment F1+2), and
c
complement system (release of
C3a-desArg) [265]
more potently than aspirin. Similarly, the thrombin-triggered aggregation is
reduced and the thromboxan production is decreased [266].
4.3
Biodegradability
In Vitro Degradation
An accelerated degradation rate of P4HB and P3HB-4HB, in comparison to
P3HB, can be expected due to the lower degree of crystallinity. This was con-
firmed by studying molecular weight decrease and mass loss of polymer films
incubated in buffer solution (Fig. 14) [51]. Other studies demonstrated a mo-
lecular weight decrease of about one third within 10 weeks of incubation in
buffer solution (37
◦
C, pH 7.4) [56]. Even small amounts of 4HB in P3HB-
4HB copolymers lead to a significantly faster hydrolysis compared to that of
P3HB. Increasing the amount of 4HB in the copolymers resulted in an acceler-
