molecules and pores between the sides of parallel molecules, which are called hole
zones (Fig. 1). The collagen fibers provide the framework and architecture of bone,
while the HAp crystals are located in the fibers and between the fibers.
2.2 Inorganic Phase of Bone
The mineral phase is mainly formed by calcium and phosphorous, which form
spindle- or plate-shaped crystals of HAp [3Ca 3 (PO 4 ) 2 .(OH) 2 ]. HAp nanocrystals of
bone locate at hole zones within the collagen fibrils. This restricts the possible
primary growth of the crystals and forces them to be discrete and discontinuous.
The mineral crystals grow with a specific crystalline orientation. The c-axes of the
Fig. 1 Assembly of collagen
fibers and bone mineral
crystals. Reprinted from [24]
with permission
Hydroxyapatite-Packed Chitosan-PMMA Nanocomposite: A Promising Material for. . .
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