Micromotion of mammalian cells measured electrically.

TLDR

Motility is a fundamental property of mammalian cells, typically observed in tissue culture by time‑lapse microscopy limited by optical resolution, and the sub‑micron component of this movement is termed micromotion. This paper examines a powerful electrical technique by which cell motion is quantitatively measured at the nanometer level. The method uses cells cultured on small evaporated gold electrodes driven by weak AC currents, and tracks impedance fluctuations over time to directly measure cell motion. Large impedance changes occur when cells attach and spread, and the resulting fluctuations persist even in confluent layers, allowing inference of average cell‑layer motions on the order of 1 nm by comparison with a theoretical model.

Abstract

Motility is a fundamental property of mammalian cells that normally is observed in tissue culture by time lapse microscopy where resolution is limited by the wavelength of light. This paper examines a powerful electrical technique by which cell motion is quantitatively measured at the nanometer level. In this method, the cells are cultured on small evaporated gold electrodes carrying weak ac currents. A large change in the measured electrical impedance of the electrodes is observed when cells attach and spread on these electrodes. When the impedance is tracked as a function of time, fluctuations are observed that are a direct measure of cell motion. Surprisingly, these fluctuations continue even when the cell layer becomes confluent. By comparing the measured impedance with a theoretical model, it is clear that under these circumstances the average motions of the cell layer of 1 nm can be inferred from the measurements. We refer to this aspect of cell motility as micromotion.