Blood compatibility of surfaces modified by plasma polymerization

Abstract

Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in the baboon with respect to their capacity to induce both acute and chronic arterial thrombosis. Polymer surface composition was determined by electron spectroscopy for chemical analysis. Steady-state arterial thromboembolism was initiated by introducing tubular segments into chronic arteriovenous shunts. Rates of platelet destruction induced by the test materials were calculated from ¹¹¹In-platelet survival measurements. Nine plasma polymers based on tetrafluoroethylene, hexafluoroethane, hexafluoroethane/H₂, and methane, when deposited on silicone rubber, consumed platelets at rates ranging from 1.1–5.6 × 10⁸ platelets/cm²-day. Since these values were near the lower detection limit for this test system, the plasma polymers were considered relatively nonthrombogenic. Acute thrombus formation was initiated by inserting expanded Teflon (Gore-Tex PTFE) vascular grafts into the shunt system. ¹¹¹In-platelet deposition was measured by scintillation camera imaging over a 1-h exposure period. Standard PTFE grafts (10 cm × 4 mm i. d.) accumulated approximately 1 × 10¹⁰ platelets over this interval. While modification of PTFE grafts with a plasma polymer based on hexafluoroethane/H₂ did not alter graft surface morphology, platelet deposition was reduced by 87% as compared to the controls (p < 0.001). We conclude that both the surface chemistry and texture of prosthetic materials influence thrombogenesis. The method of plasma polymerization may be useful for assessing the importance of these variables independently and, perhaps, for minimizing certain adverse blood–material interactions.