Traction Force Microscopy

Introduction

Traction force microscopy (TFM) is used to measure the mechanical forces imposed by a cell on a thin linear elastic material (e.g. polyacrylamide) that is opsonized with a substrate of interest. For example, the polyacrylamide substrate can be opsonized by complement proteins, which are recognized by complement receptors on phagocytes to induce frustrated phagocytosis. The polyacrylamide substrate is embedded with fluorescent beads which serve as fiducial markers. TFM requires images of the "unstrained" state (the original position of the beads) and the "strained state" (the final position of the beads). 3rd party algorithms are used to measure the displacement of each fluorescent bead. Finally, algorithms are used to predict the force vectors (both magnitude and direction) required to cause these displacements.

Protocol

References

Jaumouillé, V., Cartagena-Rivera, A. X. & Waterman, C. M. Coupling of β2 integrins to actin by a mechanosensitive molecular clutch drives complement receptor-mediated phagocytosis. Nat Cell Biol 21, 1357–1369 (2019).