Characterizing Deformability and Electrical Impedance of Cancer Cells in a Microfluidic Device.

Mechanical properties of cells, reflective of various biochemical characteristics such as gene expression and cytoskeleton, are promising label-free biomarkers for studying and characterizing cells. Electrical properties of cells, dependent on the cellular structure and content, are also label-free indicators of cell states and phenotypes. In this work, we have developed a microfluidic device that is able to simultaneously characterize the mechanical and electrical properties of individual biological cells in a high-throughput manner (>1000 cells/min). The deformability of MCF-7 breast cancer cells was characterized based on the passage time required for an individual cell to pass through a constriction smaller than the cell size. The total passage time can be divided into two components: the entry time required for a cell to deform and enter a constriction, which is dominated by the deformability of cells, and the transit time required for the fully deformed cell to travel inside the constriction, which mainly relies on the surface friction between cells and the channel wall. The two time durations for individual cells to pass through the entry region and transit region have both been investigated. In addition, undeformed cells and fully deformed cells were simultaneously characterized via electrical impedance spectroscopy technique. The combination of mechanical and electrical properties serves as a unique set of intrinsic cellular biomarkers for single-cell analysis, providing better differentiation of cellular phenotypes, which are not easily discernible via single-marker analysis.