Albumin Adsorption and Retention on C₁₈‐Alkyl‐Derivatized Polyurethane Vascular Grafts

Abstract: The short‐term albumin affinity and thrombo‐resistance of a polyether polyurethane vascular graft have been improved. The method is based on the C₁₈ alkylation of the polymer. Thrombus formation by a planimetric technique and albumin retention on wire‐reinforced polyurethane tubes, both C₁₈ alkylated and untreated, were measured in short‐term (4‐h) exposure at femoral arterial sites in the dog. ¹²⁵I‐Albumin was preadsorbed on tubes and then exposed to blood for successive 2‐h periods. Albumin uptake on alkylated tubes prior to blood exposure and retention following 2 h of blood exposure were significantly greater than on controls. Following a fast desorption phase in blood, the remaining albumin was more slowly desorbed from alkylated than from control tubes. Reincubation with albumin and blood reexposure produced a similar tendency, suggesting blood conditioning does not reduce the albumin affinity‐enhancing property of C₁₈ alkylation in the short term. Blood‐preconditioning experiments suggested endogenous albumin has a high affinity for the C₁₈‐alkylated surface. Scanning electron microscopic examination showed thrombus and platelet densities were higher on control than on alkylated surfaces. These results suggest in vivo albumin affinity is increased for C₁₈‐alkylated polyurethane, which may be linked to decreased thrombus formation on these surfaces.