The ability of surface characteristics of materials to trigger leukocyte tissue factor expression

Biomaterial-induced thrombosis is usually attributed to blood coagulation initiated by contact phase and platelet-related reactions. Considering the major role of extrinsic initiation in blood coagulation in vivo, we studied the material related-induction of this pathway by investigating the relevance of surface properties for the expression of Tissue Factor (TF), a critical initiator of the extrinsic pathway of coagulation. We incubated materials with self-assembled monolayers of alkylthiols (SAMs) displaying various ratios of –CH3, –OH, and –COOH terminations with fresh heparinized whole human blood in vitro. The transcription of TF-mRNA in leukocytes showed clear differences in relation to surface properties and increased over time. In addition, a positive correlation between TF transcription and its presence on leukocytes, granulocyte activation, and complement activation was found. Cells displaying the highest TF expression after material contact had significantly lower intracellular TF, pointing to previous TF release. Yet under the conditions of our whole blood incubation set-up within the limited time frame the observed initiation of the extrinsic pathway did not trigger blood coagulation.