Detection of cell forces by measuring deformation of polymer films via interference reflection microscopy

Abstract

Interference reflection microscopy is used for measuring changes in the resulting interference image of the measurement system. The measurement system consists of several parallel layers. The set-up includes metal layers evaporated on a glass slide and elastic polymer film with another metal layer serving as a substrate on which cells can be cultured in media. Total reflectance that depends on the thickness of the polymer layer of the system can he calculated. Cell moves on a gold layer and exert forces leading to a deformation of a polymer underneath.Deformation of a polymer and change of its thickness results in a change in the measured intensity of the light reflected from the whole system. Then the detected intensity can be compared with the calculated reflectance after the calibration according to measured values of the systems of known reflected intensities. The important parameters of the set-up are properties of the polymer layer -its elasticity modulus, refractive index and thickness. The method could enable the measurement of the component of a cell force perpendicular to the surface at which a cell moves. A cell can be viewed as an indentor deforming a polymer film at a certain area.