Plasma protein adsorption and platelet adhesion on poly[bis(trifluoroethoxy)phosphazene]

Poly[bis(trifluoroethoxy)phosphazene] (PTFEP) with a high purity and high molar mass is a biocompatible material [1] used as bulk material in medical implants. We developed a process to coat surfaces with PTFEP films and performed ELISA experiments designed to understand their blood compatibility. We observed that PTFEP adsorbs preferentially albumin from plasma, and only small amounts of coagulation or inflammation stimulating proteins. In general, there is a good correlation between increasing content of albumin in the adsorbed, protein film and reduced platelet adhesion. Another important prerequisite of blood compatibility is the stabilization of the native state of adsorbed proteins, since denaturated proteins stimulate platelet adhesion. The elutability of adsorbed proteins by sodiumdodecylsulfate solution was used to quantify the amount of irreversible attached and presumably denaturated proteins. PTFEP showed a low amount of irreversibly adsorbed proteins of the coagulation cascade. Circular dichroism measurements of adsorbed fibrinogen and albumin showed only weak distortions of the secondary structure of these proteins on the surface of PTFEP. We conclude that PTFEP has a unique blood compatibility because of the favorable composition and the stabilization of the protein layer against denaturation.