Because of its low profile and biologically inert behavior, thin film
nitinol (TFN) is ideally suited for use in construction of endovascular devices. We have developed a surface treatment for TFN designed to minimize platelet adhesion by creating a superhydrophilic surface. The hemocompatibility of expanded polytetrafluorethylene (ePTFE), untreated thin film
nitinol (UTFN), and a surface treated superhydrophilic thin film
nitinol (STFN) was compared using an in vitro circulation model with whole blood under flow conditions simulating a moderate arterial
stenosis. Scanning electron microscopy analysis showed increased
thrombus on ePTFE as compared to UTFN or STFN. Total blood product deposition was 6.3 ± 0.8 mg/cm(2) for ePTFE, 4.5 ± 2.3 mg/cm(2) for UTFN, and 2.9 ± 0.4 mg/cm(2) for STFN (n = 12, p < 0.01). ELISA assay for
fibrin showed 326 ± 42 μg/cm(2) for ePTFE, 45.6 ± 7.4 μg/cm(2) for UTFN, and 194 ± 25 μg/cm(2) for STFN (n = 12, p < 0.01). Platelet deposition measured by fluorescent intensity was 79,000 20,000 AU/mm(2) for ePTFE, 810 ± 190 AU/mm(2) for UTFN, and 1600 ± 25 AU/mm(2) for STFN (n = 10, p < 0.01). Mass spectrometry demonstrated a larger number of
proteins on ePTFE as compared to either thin film. UTFN and STFN appear to attract significantly less
thrombus than ePTFE. Given TFN's low profile and our previously demonstrated ability to place TFN covered
stents in vivo, it is an excellent candidate for use in next-generation endovascular
stents grafts.