Biomedical Engineering Reference
In-Depth Information
211
002
~82 nm
~60 nm
Domain A
~85 nm
~145 nm
~67 nm
A
200 nm
( a )
( b )
Surface minerals
Collagen fibril
HA crystals
Mineralized collagen fibers
( c )
Figure 2.5 AFM and TEM micrographs of mineralized collagen fi bril from
zebrafi sh skeleton revealing the existence of mineralization both in the hole zone
and on the surface of collagen. Reprinted with permission from [48].
has reported that the mineralized collagen fi brils became thicker and more
ordered, with increased degree of mineralization and crosslinking from
the outermost layer toward the center of the vertebra bone wall according
to the AFM and TEM investigations. In association with the thicker and
ordered fi brils, the nanomechanical properties as measured by nanoin-
dentation signifi cantly improve [66]. In addition, the AFM and TEM
observations provide some new evidence for surface deposition of HA in
the mineralized collagen fi brils. As shown in Figure 2.5, TEM observations
of unstained zebrafi sh skeleton bone without decalcifi cation treatments
provide direct evidence for the deposition of the HA crystals on the sur-
face of the fi brils making the mineralized fi brils compactly aligned, with
the diameter increasing to more than 150 nm. Further supportive evidence
was also supplied by the AFM observations, which indicated that the min-
eralized fi brils become thicker and more compactly aligned as the age of
bone increases [48]. As a consequence of these processes, it is conjectured
that as the mineralization becomes heavier, more minerals deposit on the
surface, and therefore the fi brils become thicker.
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