Measuring Cell Dynamics at the Substrate-Interface with Surface Plasmon Resonance Miscroscopy

Abstract

In neuroelectronics the cell-electrode distance is one of the most critical parameters during cell recordings. Cardiomyocytes such as HL-1 are among the most popular model systems used for cell recordings because they periodically generate an action potential.This feature also leads to a cell contraction which affects the cell-electrode distance.Therefore a quantitative characterization of the membrane dynamics directly at the interface is crucial.Imaging said dynamics in vitro and label free is a great challenge.To achieve this we built a surface plasmon resonance microscope (SPRM).With gold coated sapphire chips as the substrate for the cell culture it is possible to excite plasmons (collective electron oscillations) in the gold layer by illuminating it under a specific angle.The resonance frequency of the plasmons depends strongly upon the dielectric constant of the gold's environment.In turn the angle spectrum of the reflected light depends upon said resonance frequencies.Due to these dependencies it is possible to deduce the cell-substrate distance. Our microscope is capable of imaging the interface in two different modes.The field of view in the live imaging mode is around 65 um x 65 um. Here we can observe cell dynamics qualitatively.The scanning mode uses localized surface plasmons to measure the cell-substrate distance.The resolution in z-direction lies in the nanometer range.This allows us to measure the movement of the cell membrane caused by the cell contraction.By scanning the region of interest we can characterize the cell dynamics at each scanning point with a time resolution of 150 ms