2.7. In Vitro Platelets Adhesion Test

Platelet-rich plasma (PRP) was obtained by centrifuging fresh human whole blood containing 3.8 wt.% citrate acid at 1500 rpm for 15 min. Then, the SS, Ti–O, P50, P50R5, P50R20, and P50R42 samples were immersed in 0.5 mL PRP individually, and incubated at 37 °C for 45 min. Next, the samples were rinsed with PBS three times to remove the weakly adherent platelets, and the adherent platelets were fixed in 2.5% glutaraldehyde solution for 12 h. After the treatment of dehydrating, dealcoholizing, and critical point drying, the samples were sputter-coated with gold and imaged by scanning electron microscopy (SEM, Quanta200, Philips, Amsterdam, Netherlands).