Plasma recalcification as a measure of contact phase activation and heparinization efficacy after contact with biomaterials.

The rate of plasma clotting was measured in order to investigate two different processes. In both cases normal, pooled platelet-poor plasma was used as a substrate for measurement of clotting. The intrinsic coagulation pathway was studied by bringing a variety of biomaterials into contact with a plasma aliquot and observing the rate of clotting diminish by virtue of factor XII activation. The efficacy of heparinization was investigated by measuring the increase in clotting time of a plasma aliquot during biomaterial contact. In both cases, clotting time was measured turbidometrically. Marked differences in intrinsic pathway activation were observed between a variety of materials. There were clear differences between the materials and the negative and positive controls. The assay showed that heparinized materials could be distinguished from non-heparinized materials and a non-activated plasma control.