Biomedical Engineering Reference
In-Depth Information
3.7.2
Nanodimensional and Nanocrystalline Calcium
Orthophosphates and Bone-related Cells
It is well accepted that bone-related cells (especially, osteoblasts
and osteoclasts) play the key roles in the physiological formation
of calcified tissues. Bone-related cells not only are speculated to
take part in the formation of biominerals and macrostructure
constructions of bones, but they also continuously modulate
the density, regeneration, and degradation of bones. Therefore,
understanding the relationship between the bone-related cells and
nano-sized calcium orthophosphates has been paid much attention in
order to elucidate the formation mechanism of bones, to prevent and
cure bone-related diseases, and to design novel biomaterials. Better
structural biomimicity and osteoconductivity can be achieved using
nanodimensional and nanocrystalline calcium orthophosphates
[152, 153, 159, 160, 574-576]. Biocompatibility of such biomaterials
is the key question for their application possibility for clinical use. For
example, adhesion, proliferation, and differentiation of mesenchymal
stem cells were studied on nano-sized HA/polyamide biocomposite
scaffolds. The results indicated that such biocomposites exhibited a
good biocompatibility and an extensive osteoconductivity with host
bone
and proved that nano-sized HA/polyamide
scaffolds had a potential to be used in orthopedic, reconstructive,
and maxillofacial surgery [577-579].
Most results demonstrate that nanostructured HA can improve
cell attachment and mineralization
in vitro
and
in vivo
, which suggests that
nano-sized HA may be a better candidate for clinical use in
terms of bioactivity [159, 160, 164, 580-582]. The size effects of
nanodimensional HA on bone-related cells, as well as the influence
of crystallinity of nano-sized HA were studied [432, 583]. Different
nano-sized particles of HA, typically of 20 ± 5, 40 ± 10, and 80 ± 12
nm in diameter, were prepared and their effects on the proliferation
of two types of bone-related cells, bone marrow mesenchymal stem
cells (MSCs) and osteosarcoma cells (U2OS and MG63) were studied.
The cell culture experiments showed an improved cytophilicity of
the nanophase HA if compared to the submicron-sized HA. A greater
cell viability and proliferation of MSCs were measured for nano-sized
HA, remarkably for 20 nm-sized particles. However, the opposite
phenomenon occurred for bone tumour cells when nano-sized HA
were co-cultured with cells. Nano-sized HA can inhibit proliferation
in vivo
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