Measuring Cell Adhesion Forces: Theory and Principles

Abstract

Cell adhesion is an essential prerequisite for survival, communication, and navigation of cells in organisms. It is maintained by the organized binding of molecules from the cell membrane to the extracellular space. This chapter focuses on direct measurements of cellular binding strength at the level of single adhesion molecules. Using atomic force microscopy-based force measurements, adhesion strength can be monitored as a function of adhesion time and environmental conditions. In this way, cellular adhesion strategies like changes in affinity and avidity of adhesion molecules (e.g., integrins) are characterized as well as the molecular arrangement of adhesion molecules in the cell membrane (e.g., molecular clusters, focal adhesion spots, and linkage to the cytoskeleton or tether). Some prominent values for the data evaluation are presented as well as constraints and preparative techniques for successful cell adhesion force experiments.

Rapid Reversible Photoswitching of Integrin‐Mediated Adhesion at the Single‐Cell Level

“…[ 12 ] They can be toggled between two isomerization states, i.e., a cis Next we employed SCFS to measure cell adhesion forces [ 22 ] in response to reversible photoswitching of the mixed c(RGDfK)-azobenzene/PEG2000 monolayer. SCFS facilitates qualitative and quantitative verifi cation of true reversibility of photoswitching in situ on the single-cell level on the same surface spot with one and the same cell ( Figure 3 A), as a cell is attached to a cantilever and repeatedly brought into contact with the surface.…”

“…[ 22,29,30 ] For cell capture a small number of freshly trypsinized cells was injected into the sample chamber. Immediately, the cantilever was approached to a cell up to a contact force of a few nN and held at constant height for about 8 s, followed by careful lift-off from the surface and 12 min resting to ensure stable attachment at the cantilever.…”

“…Immediately, the cantilever was approached to a cell up to a contact force of a few nN and held at constant height for about 8 s, followed by careful lift-off from the surface and 12 min resting to ensure stable attachment at the cantilever. [ 22,29,30 ] Force-distance curves were recorded using an approach/retract speed of 30 µm s −1 . Contact between cell and surface was held at a constant force of 500 pN for 1 s. For each azobenzene confi guration, 20 force curves were recorded on each of four different positions on the surface as defi ned by the vertices of a 10 µm × 10 µm square.…”

Bioactive compounds immobilized on Ti and TiNbHf: AFM-based investigations of biofunctionalization efficiency and cell adhesion

“…For cell adhesion force measurements, one Ti and one Ti alloy sample, both coated with the same peptide or protein, were glued into the same Petri dish using biocompatible epoxy coated area of the Petri dish, a cantilever was made to approach a floating, middle-sized cell and held in contact for a few seconds [50]. After a cell was successfully attached to the cantilever, the cantilever was lifted upwards and the cell was allowed to relax for a couple of minutes before cell adhesion force experiments were started.…”

Nano-biomechanical investigation of living endothelial cells

“…Regardless of its origin, real time probe-sample adhesion can be monitored with high accuracy (Benoit and Selhuber-Unkel 2011). As biochemical and biophysical signaling of living cells relies on protein-protein interactions, protein functionalized probe -cell surface adhesion is an in vitro technique to test receptor-binding forces with AFM.…”