Biomedical Engineering Reference
In-Depth Information
aluminium porous substrates with a pore-size gradient can be readily obtained within a range
of few nanometers to few microns [35, 49]. However, controlling the topographic features
across wide-ranged feature sizes and the stability of the Si gradient formats during culture
remain challenges to overcome. Recently, Wang
et al.
fabricated relatively stable porous Si
gradients using n type Si wafer (n-pSi) [46]. This new surface allow stem cells to grow at least
1-2 months. The results showed that cell adhesion is extremely sensitive to the nanoroughness
of the interpore space. Cell adhesion and spreading was inhibited at high nanoroughness end
(small pore size), whilst cells were well attached at low nanoroughness end (large pore size,
Figure 11.2). Differentiation of rBMSCs into osteogenic and adipogenic lineages showed
that osteogenesis was dependent on both topography and local cell density whilst adipogen-
esis was dependent on topography only [46].
Responses of Stem Cells to Nanogrooved Surfaces
Surfaces with nanogrooves (or nanograting, nanostripes) are frequently used to study cell-
topography interactions. The methods for the fabrication of nanogrooved topographies include
e-beam lithography, nanoimprint lithography, mechanical polishing, grinding, and laser abla-
tion, which have been summarized in the literature [50, 51]. The general feature of cell responses
to such a topographic feature is cellular alignment and elongation along the groove direction
(Figure 11.3), a phenomenon called contact guidance. Cells have anisotropic morphology on
the grooved surface, whereas cells are spread out isotropically on the flat control (Figure 11.3).
(A)
(B)
(C)
Rat cardiomyocte on
nanogrooves (450/350)
900 nm width/100 nm depth
rBMSCs on nanogrooves (900/100)
400 nm
2
4
(D)
6
µm
8
Flat control
25 µm
25 µm
2 µm
Figure 11.3
Typical cell morphology on a grooved surface. (A) A typical atomic force
microscopy image of a nanogrooved surface. The feature size is 450 nm in width and 100 nm in depth
(ridge-to-groove ratio 1:1). (B) Rat bone-marrow-derived mesenchymal stem cells (rBMSCs) and
(C) rat cardiomyocyte are aligned with the direction of the nanogrooves. (D) The rBMSCs are
spread out isotropically on the flat control. In (C) the cells on the grooved polyurethane surface
could pull and deform the substrate, but still align with the direction of the grooves. In (B) vinculin
staining shows that focal adhesions are mainly located at the two ends of the cells on the
nanogrooves, whereas in (D) they are located around the cell periphery on the flat surface.
(See
insert for color representation of the figure.)
