Measuring the nanomechanical properties of cancer cells by digital pulsed force modeimaging

Abstract

In this paper, we demonstrate that the digital pulsed force mode data can distinguish twocancer cell lines (HeLa, Panc) by their mechanical properties. The live cells were imaged inbuffer solution. The digital pulsed force mode measured 175 force–distance curves persecond which, due to the speed of the measurement, were distorted by the viscous dragin the buffer. We show that this drag force causes a sinusoidal addition to theforce–distance curves. By subtracting the viscous drag effect one obtains standardforce–distance curves. The force–distance curves are then evaluated to extractkey data on the curves, such as adhesion energies, local stiffness or the width ofthe hysteresis loop. These data are then correlated to classify the force–distancecurves. We show examples based on the width of the hysteresis loop and theadhesion energies. Outliers in this classification scheme are points where, potentially,interesting new physics or different physics might happen. Based on classificationschemes adapted to experimental settings, we propose that the digital pulsed forcemode is a tool to evaluate the time evolution of the mechanical response of cells.