New haemocompatible polymers assessed by thrombelastography.

Mimicry of the nonthrombogenic surface of the erythrocyte has been advocated as the starting point for the development of nonthrombogenic biomaterials. Phosphorylcholine forms 88% of the outer surface of the erythrocyte, and so materials containing it should be nonthrombogenic. We have evaluated the thrombogenicity of such materials and compared them with Dacron and PTFE. Three materials containing phosphorylcholine were used: a naturally occurring phospholipid (dipalmitoylphosphatidylcholine, DPPC), a polymerized phospholipid (diacetylenic phosphatidylcholine, DAPC) and a polyester polyurethane (Polyester G). The thrombogenic potential of these materials was assessed by material thrombelastography (MTEG). This technique uses human whole blood at 37 degrees C, without an air interface, and records the elasticity of the blood clot produced. Since each material is evaluated with a control surface, extraneous differences due to factors other than the test material are eliminated. Analysis, and examples of the MTEG traces are shown and discussed. The phosphorylcholine containing materials were found to have a reduced amount of clotting factor activation, but only DPPC was better than Dacron and PTFE. MTEG demonstrated the known thrombogenicity of Dacron towards platelets. A striking reduction in platelet activation was shown for the three phosphorylcholine containing materials. These three materials show only 25% of the platelet activation of PTFE. These materials warrant further investigation as potentially very useful biomaterials.