Fabrication of microfluidic device on temperature-responsive cell culture surface for studying the shear stress-dependent cell detachment

We proposed a novel approach to quantitatively estimate the strength of cell-material interaction by using microfluidic system. The microfluidic device was made of poly (dimethylsiloxane) chip bonding on the temperature-responsive cell culture surface consisted of poly(N-isopropylacrylamide) (PIPAAm) grafted tissue culture polystyrene (TCPS) (PIPAAm-TCPS), containing five parallel test channels for cell culture. This construction allows concurrent generating five different shear forces applied to cells in each microchannel by varying the resistance of each channel, as well as obtaining identical cell incubation in each test channel. Bovine aortic endothelial cells were well adhered and spread on PIPAAm-TCPS in each channel at cell culture temperature of 37°C. Reducing temperature below the lower critical solution temperature of PIPAAm and starting flow, cells were peeled off from the hydrophilic PIPAAm-TCPS by the shear forces generated by flow. Shear stress dependent cell detachment process was evaluated with the different shear stress. Critical shear stress for cell detachment was achieved through studying the effect of shear stress on cell detachment times. As a result, the bonding strength between cells and hydrated PIPAAm-TCPS was weaker than that in other cell bonding biomaterials.