Biomedical Engineering Reference
In-Depth Information
a tissue replica, this may be the best method to obtain optimised
mechanical properties.
9.4.3 Other Processing Routes
After the first investigations on highly porous 3D scaffolds made
of bioactive-glass-filled PDLLA and PLGA, published in 2002 (see
Ref. [3] for a review), an increasing amount of research has emerged
on this subject and alternative methods are being proposed to fabri-
cate composite scaffolds. For example, 3D composites of bioactive glass
and degradable polymers have been produced by sintering composite
PLGA-Bioglass microspheres. Sintering of the microspheres (heating
the spheres until they fuse at point of contact with each other) resulted
in scaffolds with interconnected porous structure. Average porosity was
40%, with pore diameters of 90
m, and the scaffolds exhibit mechan-
ical properties close to those of cancellous bone. The scaffolds were
shown to support the adhesion, growth and mineralisation of human
osteoblast-like cells
in vitro
[11].
μ
9.5 CASE STUDY: THE PDLLA-BIOGLASS COMPOSITE
SCAFFOLD SYSTEM
There has been extensive research on the PDLLA-Bioglass composite
system, which will be described here in more detail as a typical case
of a bioactive-glass-containing composite scaffold. The TIPS method
was used to prepare PDLLA foams with different concentrations of
Bioglass particles (
40 wt%) as filler [10]. Figure 9.6 shows the typical
microstructure of a PDLLA-Bioglass foam (containing 10 wt% Bioglass)
[10]. A porosity greater than 90% was obtained and the density of
the composite foams was found to increase on addition of Bioglass;
for example, the pore volume has been shown to decrease from 9.5 to
5.7 cm
3
/g with addition of 40 wt% Bioglass, with little change observed
in the overall pore morphology.
In vitro
studies in phosphate-buffered
saline (PBS) at 37
◦
C showed that addition of Bioglass increased water
absorption and weight loss in comparison to pure polymer foams.
The molecular weight of the polymer was found to decrease at a
lower rate in the composite foams, possibly as a result of the disso-
lution of cations (Na
+
and Ca
2
+
) from the Bioglass providing a pH
buffering effect. As expected, it has been shown that PDLLA-Bioglass
<
