Modification of the interior surfaces of small-diameter expanded PTFE vascular grafts by radio frequency plasma techniques

To improve the performance of long-term arterial replacement, the interior surfaces of expanded PTFE vascular grafts were modified by radio frequency plasma techniques. Modification of grafts by immobilization of polyethylene oxide (PEO) was also investigated.; Plasma-induced graft copolymerization was used to graft polymer chains with different functional groups (such as {dollar}rm-NHsb2,-COOH{dollar}) on the substrate surfaces. These grafted surfaces can be used directly as biological and biomedical surfaces, or the grafted functional groups can be used as spacers (or reactive sites) for further immobilization of biomolecules, such as PEO or heparin.; For plasma polymer deposition, a thin layer ({dollar}<{dollar}50 nm) of a plasma polymer (methane, hexafluoroethane/{dollar}rm Hsb2{dollar} mixture, or organosilicones) was deposited on the interior surface of a PTFE graft without changing its surface morphology.; PEO was functionalized with the aldehyde group at its tail end, and then was immobilized onto the aminated surfaces by using the aldehyde-amino coupling reaction. In order to achieve a high percentage of PEO grafting, maximum amination of surfaces was required and was investigated by different amination methods.; In addition to XPS (X-ray Photoelectron Spectroscopy) and SEM (Scanning Electron Microscopy) surface characterization, the charging behavior and dynamic chain stability of plasma polymers were investigated by the surface forces measurement and the Wilhelmy plate method, respectively. A model based on the concept of "equilibration of surface states" is used to explain the contact angle hysteresis of plasma polymers.; After 3 months aorta-iliac implant in baboons, expended PTFE grafts coated with a thin layer of plasma polymer have somewhat smaller neointimal thicknesses than the untreated grafts. Plasma polymers of tetramethyldisiloxane show the highest reduction (31%). The neointimal thickness of PEO immobilized graft is 10 to 25% higher than that of the control graft. The interior surface of the graft after a thin layer of silicone rubber coating, followed by hexafluoroethane/{dollar}rm Hsb2{dollar} mixture plasma deposition shows an extremely small neointimal thickness after 1 month implantation.