PLATELET ADHESION AND ACTIVATION ON POLYURETHANE TEXTURED WITH SUBMICRON PILLARS:

We are developing a new class of blood-contacting surfaces having anti-adhesive sub-cellular textures. Unlike supra-cellular textures that encourage a neointima, ours are designed to remain free of formed elements and fibrin. We have shown that our sub-micron surface topography can reduce platelet adhesion, a key initiator of surface-induced thrombosis. Here, we report the activity of platelets on textured surfaces and present measures of platelet adhesion under time-varying flow. Polyether(urethane urea) (PUU) was textured with submicron pillars by replication molding or prepared as a smooth control. Pillars were 650nm high with 700 or 400 nm width and separation. Samples were mounted on a rotating disk (RD) in bovine platelet-rich plasma, exposing platelets to 0–10dyn/cm2 wall shear. Platelet adhesion was reduced on textured compared to smooth PUU at shear <5dyn/cm>2. Physical and chemical measures of platelet procoagulant state were comparable (area and circularity by microscopy, FXa and meizothrombin by chromogenic assay, respectively). Platelet adhesion to 700nm and smooth PUU under time-varying flow was assessed by superimposing ∼100μm lateral wobble to the RD. We observed significant reduction in adhesion to 700nm pillars at 0–50dyn/cm2. Results indicate that (1) reduced platelet adhesion on sub-micron textures is not at the expense of increased activation, and (2) greater reductions in platelet adhesion may occur in time-varying flows found in practical devices. Sub-micron patterning remains a promising approach to improving hemocompatibility of blood-contacting devices.