A tapered channel microfluidic device for comprehensive cell adhesion analysis, using measurements of detachment kinetics and shear stress-dependent motion

Abstract

We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500-1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions' cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening.

Microfluidic Platforms for the Interrogation of Intravascular Cellular Trafficking Mechanisms Influenced by Hemodynamic Forces

“…Many devices used in the study of cell-vessel wall interactions employ a parallel-plate fl ow chamber, with recent microfabrication advancements allowing for minimization of material consumption in such devices. For example, a device developed by Rupprecht et al used variable cross-sectional area along the length of a channel to study a range of shear stresses (1-50 dyn/cm 2 ) in a single device at a single fl ow rate [ 108 ]. In order to visualize cell adhesion at a range of shear stresses within one fi eld of view, Gutierrez et al designed a microfl uidic platform that features eight parallel channels [ 109 ].…”

“…An approximation of wall shear stress can be determined via Poiseuille's law and can be controlled by altering fl uid viscosity, fl uid fl ow rate, or channel dimensions [ 108 ]. For the study of shear stress regulated cell adhesion, microfl uidic channel design enables the manipulation of shear stress based on these three parameters.…”

Modulating wall shear stress gradient via equilateral triangular channel for in situ cellular adhesion assay

“…We used a critical adhesion strength to quantify the cell adhesion strength, a WSS level where 50% of the cells were detached after exposure to the flow as an adhesion indicator, which was generally suggested in previous studies. 11,13,17 Fig. 4(b) shows that the critical adhesion strength of the NIH-3T3 cells on the glass substrate is approximately 104.41 6 12.10 and 125.01 6 23.00 dyn/cm 2 (standard error was calculated from the linear fitting) after 2 h and 6 h of adhesion, respectively.…”

“…21 Although there remains whether the normal adhesion force or shear adhesion strength is a suitable parameter for quantification of the cell adhesion, the cell adhesion strength with the shear stress term has been widely reported with the various cell types on the different substrates. [6][7][8][9][10][11][12][13][14]22,23 Besides, there have been attempts to demonstrate the mechanical model to estimate the magnitude of the normal force when the WSS is applied to the adhered cells to evaluate the binding force of the integrin receptors to extracellular ligands. 12,[24][25][26] Hammer et al suggested a simple mechanical model to estimate the normal adhesion force from the cell adhesion strength measured by the shear stress term.…”

“…Various methods to generate WSS have been suggested to measure cell adhesion strength; these methods include the use of a parallelplate chamber, 6-10 a spinning disk, 11,12 and a tapered microfluidic channel. 13,14 A parallel-plate chamber is a simple system used to generate a single WSS level between two plates with a controllable gap at a given flow rate. Because of its simple system setup and for the optical advantage, it is widely used for the cell adhesion measurement including time-dependent behaviors.…”