Standardized methods to quantify thrombogenicity of blood-contacting materials via thromboelastography

Blood coagulation is the most significant complication of vascular biomaterials. A straightforward, sensitive, and standard measure of the compatibility of these materials with whole blood (hemocompatibility) is necessary to avoid coagulation. Current techniques used quantify only individual clotting components and are poor predictors of coagulation. The thromboelastograph (TEG) provides a measure of overall clot formation from whole blood. Although TEG is very common in clinical settings, its application to biomaterials is limited partly due to difficulty in sample preparation. In this protocol, whole blood samples are incubated with (1) biomaterials (tube with clamped ends) and (2) endothelial cells cultured on biomaterial surfaces (12-well plate) under controlled shearing conditions (10 rpm on rocker, at 37°C), and then the blood is transferred to the TEG to measure clot formation. TEG clearly discriminates among the R-times (time until initial clot formation) of expanded poly(tetrafluoroethylene), poly(urethane), and Tygon tubing. Marked differences in R-time are also seen when endothelial cells are cultured on various extracellular matrix proteins and proteoglycans. Thus, R-time provides a robust metric of overall thrombogenicity of biomaterials, and these procedures provide a standardized method for TEG to facilitate direct comparison among candidate biomaterials undergoing in-vitro testing.