Materials used in vascular grafts can be plasma surface modified to promote endothelialization, while retaining non-fouling characteristics

Expanded polytetrafluoroethylene (ePTFE) is a commonly used material for prosthetic implant applications. It’s mechanical strength, impermeability to blood and inertness to bio fouling make ePTFE ideal for such in vivo applications. Its flexibility aids in healing, and catheter tubing doesn’t kink very easily and generally has good compression resistance. For biomedical applications the ability to modify PTFE surfaces is important to promote interfacial biocompatibility. For example, the adhesion of anti-thrombogenic enzymes such as thrombomodulin, urokinase and heparin requires the PTFE surface to be first modified with chemical “anchors” such as carboxylic groups that provide covalent immobilization of these enzymes. Grafting of carboxylic groups to PTFE has also been used for the covalent immobilization of chitosan, for example, a membrane forming compound useful for the purification of biomaterials.

We determined that the surface energy can be controlled by limiting the degree of functionalization. This is simply controlled by the amount of time the substrates are exposed to the plasma. For example, after 30 seconds plasma we obtain a surface –OH concentration of 2% while the surface energy remains less than that of polyetheretherketone (PEEK), circa 41 dynes/cm.

PTFE can be surface modified with amino functionality as a first step in the eventual covalent conjugation of peptides that promote in vivo endothelialization. This has particular relevance to arterial prosthesis.