| Abstract
| - The suitability of the quartz crystal microbalance technique (QCM) to monitor the formation andmodulation of cell−substrate contacts in real time has recently been established. A more detailed analysisof the QCM response when living cells attach and spread on the resonator surfaces is, however, hamperedby the chemical and mechanical complexity of cellular systems and the experimental difficulties to controlone single parameter of cell−substrate contacts in a predictable way. In this study, we made use of liposomesas simple cell models and studied the interactions of these liposomes with the resonator surface. To mimicthe specific interactions between cell and protein-coated substrate as given in cell culture experiments,we incorporated biotin-labeled lipids as “receptors” in the liposome shell and preadsorbed avidin on theresonator surface. The dissipational QCM (D-QCM) technology was applied to monitor the shifts in resonancefrequency and energy dissipation during the adsorption of liposomes prepared with increasing amountsof biotin-labeled lipids. We also studied the adsorption kinetics of liposomes doped with biotin moietiesthat were attached to the lipid core by an alkyl spacer in order to increase the distance between liposomeshell and resonator surface. A comparison of these data with the adhesion kinetics of mammalian cellsas monitored by D-QCM is presented and discussed. Although the shifts in resonance frequency are verysimilar for intact liposomes and mammalian cells, the viscous energy dissipation is significantly higherwhen cells attach and spread on the resonator surface.
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