COLLAGEN-BASED SCAFFOLD FOR BONE TISSUE REGENERATION - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 765

layerofHAnanocrystalsgrownonthesurfaceofthecollagenfibrils.
Each mineralized bundle of collagen fibrils is 5.5-6.9 nm in diame-
ter, which is thicker than the self-assembled collagen fibrils, imply-
ing that the self-assembled collagen nanofibrils act as the template
for HA precipitation. The thickness of the HA crystal layer on the
surface of the collagen fibrils was calculated to be 0.75-1.45 nm.
Additionally, in order to discern the relative orientation of the HA
crystalswithrespecttocollagenfibrils,themineralizedcollagenfib-
rilswereanalyzedbyelectrondiffraction.Theresultsfinallydemon-
strate the preferential alignment of the HA crystallographic c-axis
with the collagen fibril longitudinal axis. The HRTEM analysis of the
parallel-aligned mineralized collagen fibrils revealed that a crystal
lattice is seen not only on the side area of the collagen fibrils but
also in the middle area and that the electron density on the surface
of the collagen fibrils is higher than in the interior area (Fig. 37.2b).
These findings indicate that HA crystals grown on the surface of the
collagen surround the fibrils. Scanning electron microscopy (SEM)
analysis showed that the mineralized collagen is a three-
dimensionalnetworkofcollagenfibrilsonwhichcrystalsofcalcium
phosphate have settled. The mineralized collagen fibrils are aligned
paralleltotheirlongitudinalaxes.Thecalciumphosphatenanocrys-
tals can be seen to aggregate on the surface of collagen fibrils. This
observation isin agreement with the TEMresults (Fig. 37.3).
Figure 37.3. Scanning electron micrograph of mineralized collagen
fibrils. 44