Biomedical Engineering Reference
In-Depth Information
the metal (e.g. Ni
21
and Mn
21
) which were not present in control samples.
Although the precise mechanism of the corrosion remains obscure the authors
specified that it must have an 'electrochemical' basis. From the medical point of
view it is interesting that the steel-cell system resulted in the generation of
cytokines, which are pre-inflammatory species.
Another recent study dealt with an effort to prevent the adhesion and
proliferation of cells on medical grade steel by coating the metal with polymer
films.
29
Again the culturing of murine fibroblasts and human umbilical vein
endothelial cells on the metal was successful and polymer fibrils were capable of
reducing the numbers of such cells. The authors pointed out such coatings
could have advantages in terms of anti-thrombotic behavior compared with
other methods for biologically passivating steel, (see the last section of this
chapter).
A final example that pertains to bare surfaces is some of our own research on
the behavior of various cells on gold. The particular interest in this case is the
label-free detection of the behavior at a surface of aortic smooth muscle cells
(ASMC)
30
and neurons
31
by acoustic wave physics which involves the use of a
gold electrode. (The physics and its relevance to neuron behavior in particular
is the subject of a later discussion in the text.) The ASMCs were harvested from
embryonic rat aorta and cultured by standard methods. The cells were
introduced to the on-line detection system via a flow-injection configuration.
The response of the acoustic sensor showed clearly that AMSCs attach to bare
gold successfully and are not removed by washing (Figure 2.8). Quite
surprisingly the bare metal surface yielded the best conditions with respect to
both surface capacity and fastest kinetics of attachment compared with laminin
and fibronectin coated electrodes (on-line). This observation allowed the study
of cell detachment by trypsin and in situ destruction by various reagents.
For experiments with neurons, hypothalamii were harvested and dissected
from mouse embryo and grown in primary culture. The cultures were infected
with a replication-deficient retrovirus. The minced hypothalamic cultures were
then subcloned to yield useable clones for experimental work. Immortalized
neurons were cultured directly onto the gold electrode surface to a confluence
of 80-100% (Figure 2.9). Using this configuration the behavior of the cells was
examined in terms of various parameters and effects. These included cell
adhesion and proliferation, depolarization and the response to stimulants such
d
n
4
t
3
n
g
|
0
n
3
.
Figure 2.8
Images of thickness shear mode (TSM)-surface attached cells under SEM.
(a) Structure of cells before interacting with hydrogen peroxide; (b) and (c)
Morphology of cells after the addition of hydrogen peroxide.
