Biomedical Engineering Reference
In-Depth Information
1-2 μm [9]. This microstructure favors mechanical anchorage to bone
tissue. The third level of roughness, at the nanometer scale, plays an
important role in the adsorption of proteins, adhesion of osteoblastic
cells and thus the osseointegration rate. All the interactions between
proteins and focal adhesion points of cells occur at the nanometer
scale, activating intracellular molecular signaling pathways, and
controlling cell fate [35].
Recent literature reports several methods for preparing surfaces
structured at the nanometer scale and studying the behavior of cells
on these surfaces. On metal surfaces, enhanced cell metabolic activity
has been observed, such as the upregulation of bone sialoprotein
and osteopontin [31], as well as a threefold increase in osteoblastic
cell adhesion as compared with the surfaces without nanostructure.
Furthermore, enhancement of calcium and phosphorus deposition
has been observed on nanostructured titanium alloys and on CoCrMo
surfaces but it was not observed on pure titanium [84, 131].
Recently, the behavior of osteoblastic cells was studied on
mirror-polished (Smooth-SS) and nanostructured (Nano-SS)
stainless steel surfaces [77]. Nanometer-scale features on stainless
steel were prepared by anodization. The aim of this study was to
compare osteoblastic cell behavior on smooth, plastic cultures, and
these nanostructured stainless steel surfaces were made from an
ordered array of pores. The Nano-SS exhibited a smooth surface
with a regular array of nanometer-sized cavities visible at high
magniication under SEM. The pores were organized in a hexagonal
array like a honey-comb structure. The diameter and depth of the
pores averaged 182 and 25 nm, respectively. Table 12.2 reports the
surface roughness parameters of Smooth- and Nano-SS. Both the
Table 12.2
Surface roughness, contact angle and surface energy of
mirror-polished (Smooth-SS) and nanostructured (Nano-
SS) stainless steel discs compared with plastic culture [77]
Parameter Plastic culture Smooth-SS Nano-SS
Roughness average Sa/Ra (nm) 0.65 ± 0.25 1.4 ± 0.3 6.2 ± 0.5
Roughness mean square Sq/Rq
or Rms (nm)
0.86 ± 0.30 2.0 ± 0.3 7.6 ± 0.5
Peak-to-valley height Rt (nm) 3.2 ± 0.9
31 ± 3
41 ± 4
Skewness Rsk/Ssk (nm)
—
1.88
0.06
Dynamic contact angle (°)
61 ± 1.0
64.0 ± 0.5 89.5 ± 0.5 7
Surface energy (mJ/m
2
)
48.7
43.5
34.1
