Attachment of blood erythrocytes on zirconium oxide under laminar flow

The adhesion of human erythrocytes settled for different times (15, 30 and 45 min) onto opaque zirconia surfaces of different surface roughness (R _a 0.08, 0.8 and 1.0 urn) was investigated with detachment experiments. The parallel plate/laminar flow experimental set up was employed, whereby the cells were subjected to increasing shear stress, applied via controlled flow of phosphate buffer solution (PBS), and gradually detached. The experimental results showed that the critical shear stress, T_sc, corresponding to 50% detachment, was about 15dyn/cm2. The distribution curves of attachment suggested that smoother surfaces and longer settling times favoured strengthening of cells adherence, but the influence of settling time was sounder in smoother than in rougher surfaces. Assuming that the cells' shape relaxes over prolonged settling time, a geometric model, providing satisfactory interpretation of the experimental results, is consistent with the prediction that the surface morphology precisely determines the maximum extent of erythrocyte/surface contacting area and consequently the adhesion strength.