Immobilisation of CXCL8 gradients in microfluidic devices for migration experiments

The release of inflammatory chemokines leads to the formation of chemokine gradients that result in the directed migration of immune cells to the site of injury. In this process, cells respond to soluble gradients (chemotaxis) as well as to immobilised gradients (haptotaxis). Surface-bound chemokine gradients are mostly presented by endothelial cells and supported by glycosaminoglycans (GAGs), such as heparan sulfate, involving the GAG binding site of chemokines. Microfluidic devices have been used to analyse cell migration along soluble chemokine gradients, as these devices allow the generation of stable gradients with resolutions in the range of microns. To immobilise well-controlled soluble gradients of interleukin-8 (CXCL8), an inflammatory chemokine, we developed a simple procedure using a heparin-coated PDMS-microfluidic device. We used these immobilised gradients for migration experiments with CXCL8-responsive THP-1 cells and confirmed directed cell migration. This setup might be useful for the examination of factors that may alter chemotaxis and haptotaxis as well as synergistic and antagonistic effects of other soluble and immobilised chemokines.