Biomedical Engineering Reference
In-Depth Information
encounter in a physical environment does not need a strong cytoskeleton, however upon
osteogenic differentiation, in which differentiation of MSCs become part of a larger bone
structure that functions to provide both form and strength, the supporting structure of the
cells are enhanced to enable function and withstand load bearing wear that bones endure.
Understanding the physical characteristics of MSCs during differentiation may aid in the
development of new biomaterials, which can potentiate the necessary mechanics of the cells
for the advancement of tissue engineering.
In terms of the dimensions of the nanotubes in the osteoblast (bone cell) and mesenchymal
stem cell (osteo-progenitor cell) studies, it was reported that a unique variation in cell
behaviour even within a narrow range of nanotube diameters (Brammer et al. 2009; Oh
2009).The results of the previous research can be simply summarized: osteogenic
functionality, both biochemical activity in osteoblasts and internal gene regulation of osteo-
progenitor cells, were altered by the size/diameter of TiO
2
nanotubes, as the nanotube
diameter increased, the osteogenic function also increased. Such a trend can be utilized for
improvement and control of the bone forming functionality for advanced orthopaedic
implant technologies.
In these studies however, TiO
2
nanotubes having a 1: 3 diameter: height aspect ratio was
used, which was determined by the electrochemical anodization conditions including
electrolyte solution, voltage, time, etc. While this current-state-of-the-art self assembly
process of TiO
2
anodization does not easily allow fabrication of TiO
2
nanotubes with the
diameter larger than ~100nm with the electrolyte used in this study, it would be interesting
to study the effect of even larger diameter TiO
2
nanotubes, possibly using a modified
chemical process, on osteogenic cells.
Fig. 11. Large diameter nanotubes prepared in 0.25 w/v% NH
4
F with various applied
voltages. (A) SEM micrographs showing nanotube morphology by top view (a, c, e) and
cross-sectional view (b, d, f). (B) Chart describing the effect of applied voltage on the
physical nature of the nanotube dimensions.
Other methods for making large diameter (>100nm) TiO
2
nanotubes using aqueous organic
electrolytes with a future potential use as orthopaedic implant surfaces have been explored.
Previously the anodization electrolyte method included aqueous dilute hydrofluoric acid. In
