Studying Cell–Surface Interactions In Vitro: A Survey of Experimental Approaches and Techniques - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 52

Fig. 10 Monitoring attachment and spreading of suspended cells by ECIS recordings. a Time
course of the electrode capacitance at 40 kHz during attachment and spreading of initially
suspended MDCK cells seeded at time point zero on ECIS electrodes pre-coated with different
ECM proteins (FN = fibronectin, VN = vitronectin, LAM = laminin, BSA = bovine serum
albumin). b Half-times t 1/2 and spreading rates s as determined from the data in a
spreading rate. The spreading rate is deduced from the slope of the curve at t=t 1/2
(Fig. 10 a). It is directly proportional to the adhesion energy of the cells with a
given surface composition [ 47 ]. t 1/2 values for the different protein coatings clearly
mirror the time courses of the electrode capacitance, identifying BSA as the least
adhesive protein with the highest t 1/2 value. However, the spreading rate s for BSA
is close to the values for LAM and VN, indicating a similar adhesion energy for
BSA compared to these two proteins (Fig. 10 b).
This apparent discrepancy is readily explained by the onset of ECM production
in the cells that were seeded on BSA-coated electrodes. The absence of adhesion
sites on the surface triggers ECM production and secretion.
4.3.2 Monitoring Micromotion within Confluent Monolayers
Besides the kinetics of cell attachment and spreading, ECIS is also capable of
recording metabolically driven cell shape fluctuations that have been referred to as
micromotion [ 48 ]. Micromotion recordings integrate over transient and minute
changes in cell-cell contacts, cell-substrate contacts, cell volume and cell
membrane invaginations. The scale of these cell shape fluctuations can be in the
sub-nanometer range and still be visible in ECIS measurements. Micromotion has
been electrically recorded as small and rapid fluctuations of the impedance of
cell-covered ECIS electrodes, when the impedance is tracked as a function of time
at a single frequency sensitive for these movements. According to the rule of
thumb described in the preceding paragraph, micromotion recordings are typically
performed at intermediate frequencies, most often at 4 kHz. The higher the time
resolution of the measurement the more of the inherent dynamics of the cell layer
is revealed. Thus, micromotion recordings provide direct and indirect information