Figure 4.

Global cell adhesion studies in shear flow. (A) REF52 cells were exposed to a stepwise shear gradient, with the adhesion strength being analyzed at a shear stress of 22 dyn cm^–2 (2.2 Pa). (i) Cells are able to adapt to the shear stress at longer exposure times (>9 min), with the cell adhesion strength being higher than at shorter exposure times. At low exposure times, cell adhesion is not affected by shear. (B) A tapered channel microfluidic device for comprehensive cell adhesion analysis allows the measurement of detachment kinetics and shear-induced motion. The detachment efficiencies of MDA-MB-231 and D. discoideum (i) were calculated from the detachment kinetics measured (ii). The critical shear level at which 50% of the cells are detached was assessed for four data sets: D. discoideum on a glass substrate in highly conditioned medium (green ▼) and in fresh medium (blue, ▲) and in fresh medium on APTES-coated substrate (red +), as well as MDA-MB-231 on a collagen-coated substrate (black, ●). (C) Biomechanics of cell rolling: shear flow, cell surface adhesion, and cell deformability were examined by monitoring cells via an installed mirror (i). The cell substrate contact length, L_c, as well as the cell height, H_c, were measured for different shear levels (ii) using finite element analysis. (D) Substrate-dependent adhesion of cells in channels having different hydrodynamic resistances (i). At high shear, appropriate fibronectin coating leads to enhanced cell adhesion (ii). At a shear of 2000 dyn cm^–2 (200 Pa) applied for 12 min, only 10% of the cells detached, but at twice that shear stress, more than 90% of the cells came off the surface in the same time period (iii). (A) Adapted with permission from ref (77). Copyright 2010 the Royal Society of Chemistry. (B) Adapted with permission from ref (78). Copyright 2012 the American Institute of Physics. (C) Adapted with permission from ref (79). Copyright 2000 Elsevier. (D) Adapted from ref (80). Copyright 2004 the American Chemical Society.