Microfluidic Iterative Mechanical Characteristics (iMECH) Analyzer for Single-Cell Metastatic Identification

Abstract

This study describes the development of a microfluidic biosensor called the iterative mechanical characteristics (iMECH) analyzer which enables label-free biomechanical profiling of individual cells for distinction between metastatic and non-metastatic human mammary cell lines. Previous results have demonstrated that pulsed mechanical nanoindentation can modulate the biomechanics of cells resulting in distinctly different biomechanical responses in metastatic and non-metastatic cell lines. The iMECH analyzer aims to move this concept into a microfluidic, clinically more relevant platform. The iMECH analyzer directs a cyclic deformation regimen by pulling cells through a test channel comprised of narrow deformation channels and interspersed with wider relaxation regions which together simulate a dynamic microenvironment. The results of the iMECH analysis of human breast cell lines revealed that cyclic deformations produce a resistance in non-metastatic 184A1 and MCF10A cells as determined by a drop in their average velocity in the iterative deformation channels after each relaxation. In contrast, metastatic MDA-MB-231 and MDA-MB-468 cells exhibit a loss of resistance as measured by a velocity raise after each relaxation. These distinctive modulatory mechanical responses of normal-like non-metastatic and metastatic cancer breast cells to the pulsed indentations paradigm provide a unique bio-signature. The iMECH analyzer represents a diagnostic microchip advance for discriminating metastatic cancer at the single-cell level.

Keywords: breast cancer; cell mechanics; microfluidics chip; single-cell analysis.

Figure 1

A) Illustration of design, B) fabrication process flow, and C) schematic image of setup and operation principle of the iMECH analyzer.

Figure 2

A) The plot of pressure gradient in the microfluidic channels. B) The plot of the location versus time for a single cell traveling through a deformation channel. The average transient velocity and equilibrium velocity in the iterative deformation channels for a typical (C) non-metastatic cell (MCF10A) and (D) metastatic cancer cell (MDA-MB-231) cell.

Figure 3

A) Depiction of changes in the average transient (u_i,1) and equilibrium (u_i,2) velocities in the iterative deformation channels (i=1, 2, 3) for the four breast cell lines. B) Column bars of the calculated relative percentage change of velocities between each two successive deformation channels (α_u1,2 and α_u2,3) for the selected breast cell lines. The results are shown as mean ± standard error of mean (SEM) for at least n=100 cells of each cell line.

Figure 4

A) Scatter plot of the first deformation channel’s absolute transient (u_1,1) and equilibrium (u_1,2) velocities of breast cell lines. B) Scatter plot of the relative percentage change of velocity (α_u1,2) vs. the first deformation channel’s absolute transient velocity (u_1,1) provides a new bio-signature for single-cell level identification.