Hydrophilic surface modification of polymer vascular prostheses and metal endoluminal stents.

摘要

Large diameter vascular replacements of GORE-TEX{dollar}spcircler{dollar} or Dacron{dollar}spcircler{dollar} are frequently used to replace damaged arteries. Poor long term patency of small diameter grafts, 6 millimeters or less, is attributed to platelet adhesion and the inability to regenerate a blood contacting surface of vascular endothelium. Metal endoluminal stents are vascular prostheses used to keep arterial lumens open following angioplasty. Complications for these implants include short term thrombogenicity and long term restenosis.; This study was directed to the synthesis and characterization of more biocompatible surfaces for these devices. Gamma radiation induced-graft polymerization and radio frequency plasma activation was investigated to surface modify polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), expanded polytetrafluoroethylene (ePTFE), and 316 stainless steel. To mimic natural biocompatible tissue surfacesl a series of hydrophilic polymers were grafted onto PMMA, PET, and ePTFE. Hydrophilic graft polymers were derived from N-vinyl pyrrolidone (NVP), potassium sulfopropylacrylate (KSPA), and dimethylacrylamide, and were grafted copolymerized with several bioactive compounds in a two step modification process. Complex graft surfaces containing fibronectin (Fn), laminin (Lm), type IV collagen (IV), heparin sulfate (Hp), albumin (Alb), and a synthetic fibronectin like protein polymer (RGD) were prepared.; For surface modification of endoluminal stents of 316 stainless and tantalum, a combination of RF plasma activation combined with gamma radiation induced grafting was studied. Plasma deposition of hydrophobic poly(hexane) primer layers with water plasma oxidation were examined for initial metal surface activation.; Surfaces were characterized by gravimetric analysis, contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Auger depth proGling, optical microscopy (OM), and low voltage scanning electron microscopy (SEM). Blood compatibility was evaluated by in-vitro, ex-vivo, and in-vivo radiolabelled platelet and endoluminal cell adhesion assays.; Surfaces of gamma grafted PVP provided a nonadherent surface to endothelial cells and platelets. The incorporation of albumin and RGD protein polymer in the graft polymer increased in-vitro endothelial cell adhesion to PVP surfaces.; The design and construction of instrumentation to characterize the adhesion between tissue surfaces and biomaterials was also accomplished (Chapter 7). Key design features include the ability to characterize the adhesion force under a variety of load and environmental conditions. The importance of this novel instrumentation to tissue-biomaterials interactions of ocular and vascular tissues is discussed.