Biomedical Engineering Reference
In-Depth Information
Table 4
Mechanical properties of P3HB-3HH [274]
Polymer
Elastic
Tensile
Elongation
modulus
strength
at break
[MPa]
[MPa]
[%]
P3HB-2.5%3HH
630
25.7
7
P3HB-7.0%3HH
290
17.3
24
P3HB-9.5%3HH
155
8.8
43
and PLLA/P3HB-13%HH blends showed favorable mechanical properties up
to a P3HB-3HH content of 20% [278].
5.2
Biocompatibility
Cell Culture Studies
The cell compatibility of P3HB-3HH and its blends with P3HB have been tested
in a number of in vitro studies using fibroblasts [89, 94, 115-117], bone mar-
row cells [49, 94, 124, 279], and chondrocytes [48, 89, 90, 129-131]. However,
neither in vivo testing nor hemocompatibility testing have yet been reported.
Published results with mouse fibroblasts seeded on polymer films are
partially controversial. While a high cell viability on P3HB-3HH films and
virtually no viability on P3HB films have been reported from earlier stud-
ies [89, 115, 116], comparable fibroblast viabilities on both materials have been
described more recently [94]. Methods studied for surface modification to im-
prove the wettability of the hydrophobic films include ion implantation [110],
treatment with lipases [89, 115, 116], and alkaline hydrolysis [115, 116]. Surface
hydrolysis using lipases or alkaline medium led to strongly improved cell via-
bility on P3HB and P3HB/P3HB-3HH films while P3HB-3HH films remained
essentially unaffected. Surfaces having higher hydrophilicity and smoothness
were found to increase fibroblast viability in these studies [89, 115, 116]. The ef-
fect of the comonomer composition on the cell compatibility showed preferable
growth on PHB-20%3HH in comparison to P3HB-5%3HH and P3HB-12%3HH
surfaces, which was attributed to the surface smoothness. As already men-
tioned, no significant differences between P3HB and P3HB-3HH were found
in this study. PLLA showed less cell compatibility than the PHB-based materi-
als [94]. Comparable fibroblast viabilities have also been found after seeding on
P3HB and P3HB-3HH porous matrices, made by solution-casting/salt-leaching
and treated with lipase. Coating with hyaluronic acid had a negative effect
on the cell growth in these experiments despite providing a smoother and
more hydrophilic surface. It was concluded that surface properties have to be
appropriate for protein adhesion and cell attachment [117].
