Analysis of the composite response of shear wave resonators to the attachment of mammalian cells

The suitability of the quartz crystal microbalance (QCM) technique for monitoring the attachment and spreading of mammalian cells has recently been established. Different cell species were shown to generate an individual response of the QCM when they make contact with the resonator surface. Little is known, however, about the underlying mechanisms that determine the QCM signal for a particular cell type. Here we describe our results for different experimental approaches designed to probe the particular contributions of various subcellular compartments to the overall QCM signal. Using AC impedance analysis in a frequency range that closely embraces the resonators' fundamental frequency, we have explored the signal contribution of the extracellular matrix, the actin cytoskeleton, the medium that overlays the cell layer, as well as the liquid compartment that is known to exist between the basal plasma membrane and the culture substrate. Results indicate that the QCM technique is only sensitive to those parts of the cellular body that are involved in cell substrate adhesion and are therefore close to the resonator surface. Because of its noninvasive nature, sensitivity, and time resolution, the QCM is a powerful means of quantitatively studying various aspects of cell-substrate interactions.