EX-VIVO BLOOD COMPATIBILITY OF SILICONE-CONTAINING BIOMATERIALS

The acute blood-contacting properties of five silicone-containing elas tomers and a poly(vinyl alcohol) coated silicone elastomer were assess ed using a canine ex vivo shunt model. The silicone-containing elastom ers studied included two thermoset amorphous silica reinforced dimethy l methylvinyl siloxane-based polymers which were extruded as Silastic( R) RX-50 Medical Grade Tubing (RX-50) and Silastic(R) Medical Grade Tu bing H.P. (HP). They also included three experimental thermoplastic si licone-urea urethane copolymers received as X7-4074 (SP-1), X7-4037 (S P-2), and X7-4943 (SP-3). The RX-50 tubing material showed less thromb us deposition compared to the silicone-urea urethane copolymers. This suggests that the blood-contacting response of a silicone elastomer is strongly affected by the incorporation of the urea urethane segments. Among the silicone-urea urethane copolymers, the SP-3 material showed higher levels of platelet and fibrinogen deposition than the SP-1 and SP-2 materials, whereas the SP-1 and SP-2 samples had similar levels of deposition. These results indicate that the blood-contacting proper ties of the silicone-urea urethane copolymers were influenced more by the molecular weight of the polydimethylsiloxane than by the type of d iol used in the urea urethane segments. The maximal platelet depositio n on the poly(vinyl alcohol)-coated silicone was approximately an orde r of magnitude greater than those on the silicone-containing elastomer s indicating that the PVA coating was more thrombogenic.