Effects of microfluidic channel geometry on leukocyte rolling assays

Abstract

Microfluidic cell adhesion assays have emerged as a means to increase throughput as well as reduce the amount of costly reagents. However as dimensions of the flow chamber are reduced and approach the diameter of a cell (D(c)), theoretical models have predicted that mechanical stress, force, and torque on a cell will be amplified. We fabricated a series of microfluidic devices that have a constant width:height ratio (10:1) but with varying heights. The smallest microfluidic device (200 μm ×20 μm) requires perfusion rates as low as 40 nL/min to generate wall shear stresses of 0.5 dynes/cm(2). When neutrophils were perfused through P-selectin coated chambers at equivalent wall shear stress, rolling velocities decreased by approximately 70 % as the ratio of cell diameter to chamber height (D(c)/H) increased from 0.08 (H = 100 μm) to 0.40 (H = 20 μm). Three-dimensional numerical simulations of neutrophil rolling in channels of different heights showed a similar trend. Complementary studies with PSGL-1 coated microspheres and paraformaldehyde-fixed neutrophils suggested that changes in rolling velocity were related to cell deformability. Using interference reflection microscopy, we observed increases in neutrophil contact area with increasing chamber height (9-33 %) and increasing wall shear stress (28-56 %). Our results suggest that rolling velocity is dependent not only on wall shear stress but also on the shear stress gradient experienced by the rolling cell. These results point to the D(c)/H ratio as an important design parameter of leukocyte microfluidic assays, and should be applicable to rolling assays that involve other cell types such as platelets or cancer cells.

Microfluidics-based side view flow chamber reveals tether-to-sling transition in rolling neutrophils

“…The volume of cell suspension required can be further reduced in a device with a smaller number of perfusion channels. The PDMS walls can be readily coated with proteins thus making the side view flow chamber useful for studies of neutrophil arrest and interaction of other types of leukocytes 33 34 or platelets 35 36 .…”

Nanostructured substrates for isolation of circulating tumor cells

“…The cells are finally stopped by higher adhesive forces that can withstand higher shear stress. It is important to highlight here that cell rolling velocity also depends on the cell shape and elastic properties [105–107]. Third, pseudopodia formation might also be related to cell capture yield (Fig.…”

The role of myosin II in glioma invasion: A mathematical model

“…Furthermore, mechanical stress and stiffness play a key role in regulation of overall tumor growth [ 20 ], cell migration [ 21 ], and metastatic potential in many cancer cell lines [ 22 ] including glioma [ 15 , 16 ] and breast cancer [ 23 ]. Mechanical cell deformation was investigated in the studies of effects of microfluidic channel geometry and cell deformation on leukocyte rolling system [ 24 , 25 ], amoeboid cell migration [ 26 ], dynamics of tumor cells in circulation [ 27 ], effect of matrix geometry on optimal cancer cell migration and interventions [ 28 ], and capsules and biological cells [ 29 ]. Cell migration through a confined ECM was also studied in [ 21 ].…”