Data from: A method for time-resolved measurements of the mechanics of phagocytic cups

The internalization of matter by phagocytosis is of key importance in the
defense against bacterial pathogens and in the control of cancerous tumor
growth. Despite the fact that phagocytosis is an inherently mechanical
process, little is known about the forces and energies that a cell
requires for internalization. Here we use functionalized magnetic
particles as phagocytic targets and track their motion while actuating
them in an oscillating magnetic field, in order to measure the
translational and rotational stiffnesses of the phagocytic cup as a
function of time. The measured evolution of stiffness reveals a
characteristic pattern with a pronounced peak preceding the finalization
of uptake. The measured stiffness values and their time-dependence can be
interpreted with a model that describes the phagocytic cup as a
prestressed membrane connected to an elastically deformable actin cortex.
In the context of this model, the stiffness peak is a direct manifestation
of a previously described mechanical bottleneck and a comparison of model
and data suggests that the membrane advances around the particle at a
speed of about 20 nm/s. This approach is a novel way of measuring the
progression of emerging phagocytic cups and their mechanical properties in
situ and in real-time.