Biomedical Engineering Reference
In-Depth Information
by activating of ultrafine apatite growth into the matrix. This may
lead to enhance the mechanical properties and osteointegration
with improved biological and biochemical affinity to the host bone.
Besides, the porosity was found to have a positive influence on the
ingrowth of the surrounding tissues into the pores of collagen/HA
biocomposites [771, 772].
Bovine collagen might be mixed with calcium orthophosphates
and such biocomposites are marketed commercially as bone-graft
substitutes (Table 4.2). Those further can be combined with bone
marrow aspirated from the iliac crest of the site of the fracture.
Collagraft
®
®
®
are several examples of the
commercially available grafts for clinical use [36]. Application of
these materials was compared with autografts for the management of
acute fractures of long bones with defects, which had been stabilized
by internal or external fixation [773, 774]. These biocomposites are
osteogenic, osteoinductive, and osteoconductive; however, they lack
the structural strength and require a harvest of the patient's bone
marrow. Although no transmission of diseases has been recorded
yet, the use of bovine collagen might be a source of concern [2].
Collagen sponges with an open porosity (30-100 μm) were
prepared by a freeze-drying technique and then their surface
was coated by a 10 μm layer of biomimetic apatite precipitated
from simulated body fluid [775]. The researchers found a good
, BioOss
, and Healos
in
vitro
performance with fibroblast cell culture. Other preparation
techniques are also possible [776]. Collagen/HA microspheres or
gel beads have been prepared in the intention of making injectable
bone fillers [777, 778]. Liao et al
succeeded in mimicking the
bone structure by blending carbonateapatite with collagen [779].
A similar material (mineralized collagen) was implanted into
femur of rats and excellent clinical results were observed after 12
weeks [780]. Collagen/HA biocomposites were prepared and their
mechanical performance was increased by cross-linking the collagen
fibers with glutaraldehyde [598, 600, 601]. These biocomposites
were tested in rabbits and showed a good biological performance,
osteoconductivity, and biodegradation. A similar approach was
selected to prepare HA/collagen microspheres (diameter ~5 μm) by
a water-oil emulsion technique in which the surface was also cross-
linked by glutaraldehyde [778]. That material showed a good
.
in
vitro
performance with osteoblast cell culture. A porous bone graft
substitute was formed from a nano-sized HA/collagen biocomposite
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