Alteration of PTFE Surface to Increase Its Blood Compatibility

Abstract

The aim of this study is to increase the blood compatibility of polytetrafluoroethylene (PTFE), one of the preferred materials for soft-tissue application, by a two-step procedure: first, the surface was activated by hydrogen plasma followed by acrylamide attachment and, secondly, hirudin, a potent antithrombogenic protein from leeches, was immobilized to the surface. Plasma treatment conditions were optimized and different surfaces were characterized by water contact angle measurements, ATR–FT-IR and X-ray photoelectron spectroscopy (XPS). It was seen that the contact angle of the PTFE decreased from 126° to 55° in optimum conditions. Acrylamide (25% (w/v) in ethanol/acetone (50%, v/v)) was grafted to the surface by the help of argon plasma treatment (1 min, 50 W, 13 Pa). The water contact angle was further decreased to 33° with acrylamide grafting and amide groups, which were subsequently used in protein immobilization, and could be detected both by ATR–FT-IR and XPS analysis. In the second part, hirudin was attached to these amide groups on PTFE surface by an optimized EDC/NHS activation procedure. Then a thrombogenicity test was done to detect hirudin activity. The results showed that there is a significant decrease in the clot formation compared with the untreated PTFE samples and ca. 0.3–0.4 ATU/cm2 (22–29 ng/cm2) of hirudin was enough to prevent the clot formation. A preliminary study showed that the hirudin immobilized membranes keep their antithrombogenic activity for at least 40 days in 37°C in PBS (0.1 M, pH 7.4). As a result, the blood compatibility of PTFE surfaces was ameliorated by plasma-induced monomer grafting and hirudin immobilization, and an alternative material was obtained to be used in medical applications such as vascular grafts, catheters, etc.