Effects of membrane undulations on contact time and area in cell adhesion

A micropipette-aspirated, ligand-coated red blood cell is commonly used as a picoforce transducer for measuring its adhesion to a receptor-expressing cell mediated by as low as a single bond. Despite the fact that the two cells are put into contact by a precisely-controlled piezoelectric translator, the effective contact time is limited by the thermally excited membrane undulations. Using analytical solutions and numerical simulations, we showed that the undulation amplitude follows a normal distribution, with a variance equal to the ratio of the thermal energy k_BT (where k_B is the Boltzmann constant and T is the absolute temperature) and the spring constant of the force transducer.