Biomedical Engineering Reference
In-Depth Information
phus
[244],
Pseudomonas acidovorans
[245],
Comamonas acidovorans
[246],
or
Hydrogenophaga pseudoflava
[241]. Biotechnologically produced P4HB
and P3HB-4HB have high molecular weights and properties suitable for med-
ical applications, including tissue engineering (congenital heart defects, heart
valves, vascular grafts), suture materials, and surgical textiles [47].
4.1
Mechanical Properties
P4HB has improved mechanical properties over P3HB, such as low stiffness
andbrittleness,andhighelongationatbreak.Furthermore,improvedprop-
erties can already be found in P3HB-4HB copolymers having small amounts
of 4HB [62]. With increasing amounts of 4HB, to approximately 20-50%,
these copolymers exhibit elastomeric properties (Martin DP, personal com-
munication). Thermal and mechanical properties of P4HB and P3HB-4HB
solution-cast films are compared with those made of P3HB in Table 2 [51, 247].
Slightly different mechanical data for P4HB are reported from another
study, comparing dense and porous films for cardiovascular tissue engin-
eering made by melt-processing without or with salt-leaching. The mechan-
ical strength of porous scaffolds is low compared to dense polymer films
(Table 3) [56].
Table 2
Thermal and mechanical properties of P3HB, P3HB-4HB, and P4HB [51, 247]
Polymer
T
g
T
m
Elastic
Tensile
Elongation
modulus
strength
at break
[
◦
C]
[
◦
C]
[MPa]
[MPa]
[%]
P3HB
10
178
2730
36
2
P3HB-18%4HB
- 22
137
320
12
1120
P4HB
- 47
61
230
36
1140
Table 3
Mechanical properties of dense P4HB films (made by melt-processing) and porous
P4HB films (made by melt-processing/salt-leaching) [56]
P4HB morphology
Elastic
Tensile
Elongation
modulus
strength
at break
[MPa]
[MPa]
[%]
Dense film
64.8
51.7
1000
Porous film (50% porosity)
14.9
6.2
164
Porous film (80% porosity)
1.8
1.2
100
