Biomedical Engineering Reference
In-Depth Information
9.3
Formation of Electrochemically Grown
Ca-P Layer
Titanium is a metallic bioinert material, and from that point of
view, it is desirable to ind possible methods to improve the
bioactivity as well as corrosion resistance of the porous titanium
and its alloys. To improve the bioactivity of the porous titanium
alloy implants, a bioactive layer of hydroxyapatite (HA) can be
formed on the implant surface. Hydroxyapatite can easily bond to
living tissues. The HA layer improve the biocompatibility, while
the metallic background provide good mechanical properties.
Hydroxyapatite can be deposited using processes of mineralization
in SBF, sputtering, sol-gel, laser deposition, thermal spraying,
electrochemical deposition, or biomimetic [14, 21, 23, 102].
Vertically aligned titanium oxide nanotubes grown on the
surface of titanium substrate by anodization in HF electrolyte show
promising properties for implant applications [66]. The array of
TiO
2
nanotubes adherent to Ti implant surface can be useful for
accelerated bone growth in orthopedic/dental applications [66].
The additional chemical treatment with NaOH makes them more
bioactive, which results in signiicantly accelerated kinetics of the
hydroxyapatite growth by a factor as much as 7. Figure 9.65. shows
SEM image (a) of the nanotubes after soaking the SBF for 1 day.
The EDX spectrum (b) shows presence of Ca, P, and O in the formed
layer, indicating the hydroxyapatite formation. The nanostructured
HA has feature dimension of about 25 nm (Fig. 9.65a) and taking
into account results of Webster
et al
. [96, 98], the nanostructured
ceramics signiicantly improves osteoblast adhesion. So the Oh and
Jin [66] obtained comparable results to Webster
et al
. [96, 98]. The
adhesion/growth of osteoblast cells is also signiicantly accelerated
by the topography of the TiO
2
nanotubes, with the ilopodia of the
growing cells going into the nanotube pores, producing a locked-
in cell structure [66]. The number of the adhered cells to the TiO
2
nanotubes increases by 400% in comparison with microcrystalline
Ti.
In vitro
cell culture using MC3T3-E1 osteoblast cells on pure
Ti (with native oxides) and vertically aligned anatase TiO
2
is
shown on Fig. 9.66. The growth of cells and the propagation of
ilopodia are much faster in the TiO
2
nanotubes (b) (2 h incubation)
compared with the Ti sample (a) (12 h incubation) [66].
