The Quartz Crystal Microbalance in Cell Biology: Basics and Applications

Abstract

This chapter describes recent studies in which the quartz crystal microbalance (QCM) technology has been applied as a monitoring tool for animal cells in vitro. With shear wave resonators used as growth substrates it is possible to follow the de novo formation or the modulation of established cell-substrate contacts from readings of the resonance frequency with a time resolution in the order of seconds. From cell adhesion studies it became clear that different cell types induce an individual shift of the resonance frequency but it has been a matter of debate, which subcellular structures determine the individual impact of a given cell type on the QCM response. This question has been addressed by our group in recent years and a summary of our current understanding of this problem will be given here. Different approaches have been applied to challenge the cells in a well-defined way and to monitor the associated changes of the QCM readout. Taken together, these studies have led us to the following conclusions: (i) The cellular bodies primarily lead to an increased energy dissipation that does not correspond to a simple viscous behavior. (ii) The adhesive proteins underneath the cells provide a measurable contribution to the overall QCM response of adherent cells. (iii) The average distance between lower cell membrane and substrate surface does not have a significant impact on the acoustic load situation. (iv) The QCM is sensitive to cell stiffness and reports in a similar way on changes in cell stiffness, as accessible from scanning force microscopy measurements. (v) The cortical actin cytoskeleton is a dominant contributor to the cells’ acoustic response.