Abstract
The mechanical properties and responses of cells to external stimuli (including drugs) are closely connected to important phenomena such as cell spreading, motility, activity, and potentially even differentiation. Here, reversible changes in the viscoelastic properties of surface-attached fibroblasts were induced by the cytoskeleton-perturbing agent cytochalasin D, and studied in real-time by the quartz crystal microbalance with dissipation (QCM-D) technique. QCM-D is a surface sensitive technique that measures changes in (dynamically coupled) mass and viscoelastic properties close to the sensor surface, within a distance into the cell that is usually only a fraction of its size. In this work, QCM-D was combined with light microscopy to study in situ cell attachment and spreading. Overtone-dependent changes of the QCM-D responses (frequency and dissipation shifts) were first recorded, as fibroblast cells attached to protein-coated sensors in a window equipped flow module. Then, as the cell layer had stabilised, morphological changes were induced in the cells by injecting cytochalasin D. This caused changes in the QCM-D signals that were reversible in the sense that they disappeared upon removal of cytochalasin D. These results are compared to other cell QCM-D studies. Our results stress the combination of QCM-D and light microscopy to help interpret QCM-D results obtained in cell assays and thus suggests a direction to develop the QCM-D technique as an even more useful tool for real-time cell studies.
Highlights
The mechanical properties and responses of cells, often termed mechanosensing or mechanotransduction, are tightly linked to cell fate processes [1]
Reversible changes in the viscoelastic properties of surface-attached fibroblasts were induced by the cytoskeleton-perturbing agent cytochalasin D, and studied in realtime by the quartz crystal microbalance with dissipation (QCM-D) technique
In another study cytoskeletal remodelling induced by epidermal growth factor receptor signaling was monitored [36], and recently extended to include atomic force microscopy measurements of changes in individual cells [37]. It is notable when comparing the results reported in the growing number of QCM and QCM-D studies involving cells, that there is still no clear picture of what kind of signals in f and D that should be expected from cells on surfaces, neither with respect to the magnitude nor the sign of those f and/or D shifts
Summary
The mechanical properties and responses of cells, often termed mechanosensing or mechanotransduction, are tightly linked to cell fate processes [1]. QCM-D is an acoustic surface sensitive method monitoring (1) changes in mass near the sensor surface as a shift in the resonance frequency (Df) of the sensor crystal and (2) changes in viscoelastic (e.g., stiffness) properties of the adlayer via changes in the damping, or equivalently, the energy dissipation (DD) of the shear oscillation of the sensor. Based on such results, the viscoelastic properties of layers formed onto the sensor can be modeled [8,9,10,11,12,13,14]. In the cell study area, QCM-D has mostly been used for the development of organic surface modifications, often called functionalised surfaces, intended for biological applications like
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