Biomedical Engineering Reference
In-Depth Information
nanotubes were formed on Ti-Hf alloys by etching in 1M H 3 PO 4 +
0.5 wt% NaF electrolyte followed by crystallization in the Ar
atmosphere (1 h at 550°C). Uniform nanotubes were formed for
Hf contents up to 20 wt%, and for higher Hf content the irregular
nanotubes were found [36]. Increasing the Hf content in the
Ti alloy led to the formation of nanotubes with more narrow size.
The nanotubes diameter ranging from 80-120 nm and a length of
approximately 1.7 μm was obtained. The nanotube morphology of
the Ti-Hf alloys can be controlled by varying the amount of Hf. The
anatase is observed predominantly with increasing Hf content [36].
The biomedical application possibilities of the nanotubes were
presented by Schmuki's group [54, 71] (Fig. 9.58). The cell adhesion,
proliferation, and migration are signiicantly affected by the nanotube
size [71]. Geometries with a spacing of 15 nm were most stimulating
for cell growth and differentiation, whereas diameters of approx.
100 nm led to a drastically increased cell apoptosis (Fig. 9.58).
Figure 9.58 Proliferation and apoptosis (after 2 days) of cells dispersed on
different diameter TiO 2 nanotube layers (a); optical images of
the cell population on nanotubular TiO 2 surfaces indicating
the cell-stimulating effect of a 15 nm diameter nanotube layer
compared to a 100 nm diameter (b) [54, 71].
 
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