Biomedical Engineering Reference
In-Depth Information
Fig. 9 Schematic of the ECIS principle, indicating AC current flow between the small working
electrode and the larger counter electrode via the culture medium. The arrows, which indicate AC
current flow, are drawn unidirectional only for the sake of clarity. The size of the electrodes is not
drawn to scale with respect to cell size
its electrochemical properties and the well-established concepts for surface
modifications. However, the method has been successfully transferred to other
electrode materials such as platinum or indium tin oxide (ITO). The latter cases
will not be covered in the following paragraphs, which will deal only with ECIS
using gold film electrodes. The gold electrodes can be coated with individual
components of the ECM or reconstituted preparations of native matrices without
losing any sensitivity. Due to their inertness they can be modified by simple
adsorption with almost any compound that has to be tested for its impact on
cell-substrate adhesion. Moreover, there is an enormous tool box available for
modifying the gold surfaces covalently by self-assembly reactions with com-
pounds that carry thiol moieties as functional groups. ECIS is, however, of no
use for polymeric or ceramic coatings as these are non conducting and they
cannot be coated on the electrodes without losing the ability to perform ECIS
readings.
Moreover, ECIS is very well suited to study cell-surface interactions on
topographically structured substrates with specific topographical features. For this,
inert substrates that carry the topography of interest have to be coated with a thin
gold film in a well-defined electrode layout such that impedance readings can be
performed with sufficient sensitivity. Characterizing the kinetics of cell attachment
and spreading upon topographically structured in vitro surfaces might be of
interest before these materials can be used as biomaterials in biosensors or
implants.
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