Influence of nanoporesize on platelet adhesion and activation

In this study we have evaluated the influence of biomaterial nano-topography on platelet adhesion and activation. Nano-porous alumina membranes with pore diameters of 20 and 200 nm were incubated with whole blood and platelet rich plasma. Platelet number, adhesion and activation were determined by using a coulter hematology analyzer, scanning electron microscopy, immunocytochemical staining in combination with light microscopy and by enzyme immunoassay. Special attention was paid to cell morphology, microparticle generation, P-selectin expression and beta-TG production. Very few platelets were found on the 200 nm alumina as compared to the 20 nm membrane. The platelets found on the 20 nm membrane showed signs of activation such as spread morphology and protruding filipodia as well as P-selectin expression. However no microparticles were detected on this surface. Despite the fact that very few platelets were found on the 200 nm alumina in contrast to the 20 nm membrane many microparticles were detected on this surface. Interestingly, all microparticles were found inside circular shaped areas of approximately 3 mu m in diameter. Since this is the approximate size of a platelet we speculate that this is evidence of transient, non-adherent platelet contact with the surface, which has triggered platelet microparticle generation. To the authors knowledge, this is the first study that demonstrates how nanotexture can influence platelet microparticle generation. The study highlights the importance of understanding molecular and cellular events on nano-level when designing new biomaterials.