Quantification of Apparent Membrane Tension and Membrane-to-Cortex Attachment in Animal Cells Using Atomic Force Microscopy-Based Force Spectroscopy.

Reliable quantification of a cell's biophysical properties is key for understanding the role of mechanics in cell biology. Plasma membrane tension, the energetic cost of increasing the surface area of the plasma membrane, has been shown to regulate a plethora of cellular processes, ranging from leading edge formation to phagocytosis and membrane trafficking. Here, we describe the measurement of this key mechanical property of the cell surface using atomic force microscopy (AFM)-based force spectroscopy. Depending on the nature of the force curve acquisition, AFM measurements can quantify various membrane tension components, such as apparent membrane tension and membrane-to-cortex attachment (MCA). We discuss the biophysical background (1), required materials (2), sample preparation (3.1), AFM-probe calibration and functionalization (3.2), force curve acquisition (3.3) and data analysis and representation (3.4).