**3.1.1.2 Platelet adhesion**

The platelet adhesion experiments were carried out using platelet-rich plasma (PRP). Healthy human fresh blood was collected using vacuum tubes (7 ml, Venoject II, Terumo, Co.), containing citrate/phosphate/dextrose/adenine-1 mixture solution (CPDA-1) as an anticoagulant (anticoagulant to blood ratio, 1:7). The blood was centrifuged at 1000 rpm for 10 min to obtain platelet-rich plasma (PRP) or at 2800 rpm for 15 min to obtain platelet-poor plasma (PPP). The fresh PRP sample was used for the platelet adsorption experiments.

The PES membranes (11 cm2 each piece, always flat-sheet membranes) were immersed in PBS solution and equilibrated at 37 C for 1 h. The PBS solution was removed and then 1ml of fresh PRP was introduced. The membranes were incubated with PRP at 37 C for 2 h. PRP was decanted off and the membranes were rinsed 3 times with PBS solution. Finally, the membranes were treated with 2.5 wt% glutaraldehyde in saline for 2 days at 4 C. The samples were washed with PBS solution, subjected to a drying process by passing them through a series of graded alcohol-saline solutions (0%, 25%, 50%, 75% and 100%) and then dried at room temperature. The dried membranes after gold coating were examined using a S-2500C scanning electron microscope (SEM, Hitachi, Japan). The number of adhering platelets on the membranes was calculated from four SEM pictures at a 500 magnification from different places on the same membranes. These procedures were performed on each membrane using four independent membranes (totally n=16), and the number was finally averaged to obtain reliable data.
