Biomedical Engineering Reference
In-Depth Information
porous scaffolds were coated by a PCL/HA composite coating [54].
In this system, PCL, as a coating component, was able to improve
the brittleness and low strength of the HA scaffolds, while the
particles in the coating were to improve the osteoconductivity and
bioactivity of the coating layer. More complex formulations, such as
PDLLA/PCL/HA [439], PLLA/PCL/HA [440], and supramolecular
PCL/functionalized HA [441] biocomposites, have been prepared
as well. Further details on both the PCL/HA biocomposites and the
processing methodologies thereof might be found elsewhere [328].
A spread of attached human osteoblasts onto PLA and PCL films
reinforced with CDHA and sintered HA was shown to be higher than
that for the polymers alone [184]. Moreover, biochemical assays
relating cell activity to DNA content allowed concluding that cell
activity was more intense for the composite films [184]. Kim et al
.
coated porous HA blocks with PCL from dichloromethane solution
and performed drug release studies. The antibiotic tetracycline
hydrochloride was added into this layer, yielding a bioactive implant
with drug release for longer than a week [54].
Yoon et al. investigated the highest mechanical and chemical
stability of FA by preparing FA/collagen biocomposites and studied
their effect in osteoblast-like cell culture [442]. The researchers
found an increased cellular activity in FA composites compared to HA
composites. This finding was confirmed in another study by means
of variations in the fluoride content for FA-HA/PCL composites
[443]. An interesting phenomenon of fractal growth of FA/gelatin
composite crystals (Fig. 1.8) was achieved by diffusion of calcium-
and orthophosphate + fluoride-solutions from the opposite sides
into a tube filled with a gelatin gel [444-453]. The reasons of this
phenomenon are not quite clear yet; besides, up to now nothing has
yet been reported on a possible biomedical application of such very
unusual structural composites.
6.4.1.2
TCP-based biocomposites
Both α-TCP and β-TCP have a higher solubility than HA (Table 1.1).
Besides, they are faster resorbed
[454]. Therefore, these
calcium orthophosphates were widely used instead of apatites to
prepare completely biodegradable biocomposites [456-479]. For
example, a biodegradable and osteoconductive biocomposite made
of β-TCP particles and gelatin was proposed [466]. This material was
tested
in vivo
in vivo
with good results. It was found to be biocompatible,
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