Studying Cell–Surface Interactions In Vitro: A Survey of Experimental Approaches and Techniques - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 53

Fig. 11 Cellular
micromotion as revealed in
time-resolved measurements
of the normalized resistance
of an ECIS electrode covered
with a confluent monolayer of
MDCK (blue) or NRK cells
(red) before (thick lines) and
after fixation (thin lines) with
formaldehyde. The resistance
was measured at 4 kHz each
time
about the cytocompatibility of a given surface—via direct contributions from the
cell-surface junction to the observed impedance fluctuations, and indirectly since
micromotion is a general indicator of cell viability [ 49 ].
Figure 11 compares the micromotion of two different cell lines before (thick
lines) and after (thin lines) the cells were fixed with formaldehyde. Different cell
lines show individual and characteristic ''fingerprints'' of their motility whereas
dead cells no longer induce any significant resistance fluctuations anymore.
Analysis of micromotion for different electrode coatings may provide valuable
insights into the interactions between cells and a given surface.
4.3.3 Monitoring Cell Migration
Cell-surface interactions play an important role in the ability of a cell to migrate,
as, for instance, during wound healing or embryonic development. The easiest
assay for assessing cell migration on a given ECM in vitro is called the wound
healing scratch assay: a confluent cell monolayer grown on the surface under
study is mechanically wounded by scratching the tip of a pipette or a needle
through the cell layer. The size of the lesions depends on the size of the needle.
Cells from the periphery of the scratch migrate into the center of the wound
and this process can be documented and analyzed microscopically over time.
A weakness of this assay is the time-consuming analysis of the micrographs and
the fact that the applied mechanical wounds are often hard to reproduce. The assay
becomes significantly more reproducible and more convenient when the cell layer
is established on ECIS electrodes such that the electrodes can be used to apply a
lethal electric field and thereby wound those cells residing on the electrode surface.
When the conditions of the electric wounding pulse are properly selected, all the
cells on the electrode surface die but not those in the periphery of the electrode
(Fig. 12 ). Migration of viable cells from the electrode periphery to the center of the
electrode (wound healing) can be followed quantitatively by time-resolved ECIS