Biomedical Engineering Reference
In-Depth Information
nano-HA/collagen/osteonectin composites for bone graft applica-
tions. The results demonstrated that ostonectin played a role in
allowing crystal growth to proceed in an orderly way in bone. All
these showed that noncollagenous proteins in natural bone also
played a role in regulating mineralization of HA crystals in bone,
whichcanhelpustobetterunderstandthebiomineralizationmech-
anismof HA crystals.
In summary, preliminary studies have shown that collagen is
an important structural agent to direct HA mineralization by pro-
teinsorpolymerswithbonelikeorganization.Forthesereasons,the
form of bone can be an “organic matrix-mediated” mineralization
process.
37.3.2
Assembly of the Nano-Fibril of Mineralized Collagen
Scientists have attempted to mimic the collagen-mineralization
process
in vitro
in order to achieve a better understanding of the
organizational structure in naturally occurring tissues in which the
major organic matrix is collagen. Numerous studies about miner-
alized collagen have been reported, as described in the following
paragraphs.
22
Rhee
40
investigated the nucleation of Ca-P crystals through
chemical interaction with collagen by soaking a collagen membrane
in asupersaturated simulated body fluid solution.By combiningthe
collagen fibril assembly and the calcium phosphate formation in a
one-process step, Bradt
et al
.
41
obtained a homogeneously mineral-
ized collagen gel consisting of a three-dimensional network of col-
lagenfibrilscoveredwithcalciumphosphate.Theinitialprecipitate,
along with the fibril assembly, was amorphous calcium phosphate.
This was then transformed into a crystalline apatite-like phase.
The addition of polyaspartate to the reaction mixture was found to
improvetheattachmentbetweenthecollagenfibrilsandthecalcium
phosphate crystals. Goissis
et al
.
42
reported both
in vitro
and
in vivo
studies of biomimetic mineralization of charged collagen matrices.
Their results showed that the calcium phosphate deposited in close
resemblance to assembly of collagen fibrils
in vivo
. Additionally, the
in vitro
resultssuggestedthatamidehydrolysismayhaveintroduced
into the matrix signs for the controlled mineralization of collagen
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