Biomedical Engineering Reference
In-Depth Information
12.3.3
Adhesion of Osteoblast-Like Cells on
Nanostructured Hydroxyapatite
In the ield of biomaterials for substitution and reorganization of
hard tissue, calcium phosphate ceramics are quite important because
natural hard tissues are primarily composed of hydroxyapatite (HA)
[15, 18, 32, 99, 135]. In consequence, the nanoscale topography of
calcium phosphate ceramics determines the cellular performance of
mesenchymal stem cells and osteoblast cells. Osteoblast proliferation
was reported to be enhanced on nanophase HA in comparison with
borosilicate glass, nanophase alumina, and nanophase titania [135].
Recently, the response of osteoblast-like cells seeded on
hydroxyapatite substrates consisting of nano-sized crystals
was investigated [99]. Various types of HA nanocrystals, such
as nanoibers, nanoneedles, and nanosheets were selectively
prepared as substrate through the hydrolysis of a solid precursor
crystal of CaHPO
4
in alkaline solutions by varying the pH and ion
con-centrations. Although all the substrates were macroscopically
lat and smooth, the nanoscale topography inluenced cell activity
including the adhesion, proliferation, elongation, and formation of
actin stress ibers. The presence of ine nanoneedles and nanoibers
on the surface restricted the cellular activities, while the cells steadily
proliferated on a nanoscopically smooth surface of large grains and
on a substrate consisting of wide nanosheets. These results suggest
that the adhesion and subsequent responses of osteoblast-like cells
were affected by the contact domain size between the cell and the
substrate. Isolated small domains of the nanostructured HA limited
focal adhesion formation in the cells associated with the formation
of stress ibers. Stable adhesion with contact domains larger than
100 nm in width was suggested to be required for cell survival. On
the other hand, insuficient adhesion on the ine nanoneedles was
found to lead to apoptosis.
Recently, research has been directed toward the development of
electrostatic spray deposition technique, allowing the fabrication
of dense, porous or nanostructured CaP coatings [4, 46, 47, 75, 79].
Figure 12.6 shows a typical osteoblast response to nanoscale
hydroxyapatite particles deposited on to a glass surface using
electrohydrodynamic atomization. Reports in the literature
suggest that the special properties of these coatings are likely to
inluence protein interactions and subsequently, control
in vitro
cell
