ElectroDeformation-Relaxation of Cells in Suspension to Characterize Mechanical Properties

Mechanical properties of biological cells are closely linked with their physiological and pathological states. To characterize such properties, we have developed a technique based on on-chip electrodeformation-relaxation of cells in suspension. Using an indium-tin-oxide (ITO) coated glass slide, the experimental platform set up parallel electrodes along the edge which were lithographically defined by etching ITO. Cells were exposed to high frequency and amplitude electric pulses. Images of electrodeformation and the subsequent relaxation upon pulse cessation were analyzed to quantify shape evolution during the process. Two distinctive regimes were identified by data analysis. If cells were deformed for shorter than a threshold of approximately tens of milliseconds, the relaxation timescales are independent of the pulse duration, indicating invariant mechanical properties. When deformed for longer than the threshold, the relaxation time scales linearly with the pulse duration, which is typically seen in soft glassy materials. This behavior is found to be coherent across the various cell types examined, providing insights into understanding cellular response to mechanical cues.