Biomedical Engineering Reference
In-Depth Information
(A) Nanostructured titanium
(B) Nanosized CaP crystals
FIGURE 16.2
Scanning electron micrographs and energy dispersive analysis for X-ray of (A) nanostructured titanium
surface obtained by anodization and (B) nanosized thin CaP coating on titanium produced by electrochemical
deposition. Note the regular array of TiO
2
nanopores of approximately 100 nm in diameter and the nanosized
CaP crystals on titanium surfaces.
for a specific biological response. Following in vitro screening, nanostructured surfaces may then
be tested in animal models to validate hypothesis in a complex in vitro environment.
New coating technologies have also been developed for applying hydroxyapatite (HA) and
related calcium phosphates (CaP), the mineral of bone, onto the surface of implants (
Figure 16.2
).
Many studies have demonstrated that these CaP coatings provided titanium implants with an osteo-
conductive surface
[5,6]
. Following implantation, the dissolution of CaP coatings in the periimplant
region increased ionic strength and saturation of blood leading to the precipitation of biological
apatite nanocrystals onto the surface of implants. This biological apatite layer incorporates proteins
and promotes the adhesion of osteoprogenitor cells that would produce the extracellular matrix of
bone tissue. Furthermore, it has been also shown that osteoclasts, the bone resorbing cells, are able
to degrade the CaP coatings through enzymatic ways and can create resorption pits on the coated
surface
[6]
. Finally, the presence of CaP coatings on metals promotes an early osseointegration of
implants with a direct bone bonding as compared to noncoated surfaces. The challenge is to pro-
duce CaP coatings that would dissolve at a similar rate than bone apposition in order to get a direct
bone contact on implant surfaces.
