Biomedical Engineering Reference
In-Depth Information
combined with PLA by a freeze-drying method; the resulting material
was found to mimic natural bones at several hierarchical levels
[609]. Subsequent
experiments confirmed a good adhesion,
proliferation, and migration of osteoblasts into this composite [608].
A further increase in biocompatibility might be achieved by addition
of various dopants. For example, to enhance bone substitution, Si-
substituted HA/collagen composites have been developed with
silicon located preferentially in the collagen phase [599]. Porous
(porosity level ~95% with interconnected pores of 50-100 μm)
biocomposites of collagen (cross-linked with glutaraldehyde) and
β-TCP have been prepared by a freeze-drying technique, followed
by sublimation of the solvent; the biocomposites showed a good
biocompatibility upon implantation in the rabbit jaw [781].
Biocomposites of calcium orthophosphates with collagen were
found to be useful for drug delivery purposes [618, 721, 764, 782-
784]. Namely, an HA/collagen—alginate (20 µl) with the rh-BMP2
(100 µg/ml, 15 µl) showed bone formation throughout the implant
5 weeks after implantation without obvious deformation of the
material [618]. Gotterbarm et al
in vitro
developed a two-layered collagen/
β-TCP implant augmented with chondral inductive growth factors for
repair of osteochondral defects in the trochlear groove of minipigs.
This approach might be a new promising option for the treatment of
deep osteochondral defects in joint surgery [783].
To conclude this part, one should note that biocomposites of
apatites with collagen are a very hot topic of the research and up
to now, just a few papers are devoted to biocomposites of other
calcium orthophosphates with collagen [742-744, 783, 785-788].
These biomaterials mimic natural bones to some extent, while their
subsequent biological evaluation suggests that they are readily
incorporated into the bone metabolism in a way similar to bone
remodeling, instead of acting as permanent implant [609, 731].
However, the performance of these biocomposites depends on the
source of collagen from which it was processed. Several attempts
have been made to simulate the collagen-HA interfacial behavior in
real bone by means of cross-linking agents such as glutaraldehyde
[598, 600, 601, 736, 778, 781] with the purpose to improve the
mechanical properties of these biocomposites. Unfortunately, a
further progress in this direction is restricted by a high cost, difficulty
to control cross-infection, a poor definition of commercial sources
of collagens, as well as by a lack of an appropriate technology to
.
Search WWH ::
Custom Search