A sutureless aortic stent-graft based on a nitinol scaffold bonded to a compliant nanocomposite polymer is durable for 10 years in a simulated in vitro model.
OBJECTIVE
To physiologically test the durability of a sutureless aortic stent-graft based on nitinol bonded to polyhedral oligomeric silsesquioxane (POSS) and poly(carbonate-urea) urethane (PCU) for 10 years according to Food and Drug Administration guidelines.


METHODS
Aortic stent-grafts (n = 4) were tested in 37°C distilled water using simulated in vivo hydrodynamic pulse loading. After 400 million cycles, surface topography was assessed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Dynamic compliance was measured using a pulsatile flow phantom. Mechanical and elastic properties were determined by stress-strain studies and elastic deformation tests. Dynamic scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to assess thermal resistance. Comparison was made with a zero-cycled control.


RESULTS
All stent-grafts successfully completed accelerated pulsatile fatigue at 94±14-mmHg pulse pressure. SEM images confirmed uniform surface topography without any fractures. FTIR showed increased intensity of -NHCO- bonds, but there was no significant sign of biodegradation. Tensile stress of fatigue-tested polymer compared favorably with the zero-cycled control at 50% to 500% strain (p = 0.69). At a mean pressure range of 60 to 120 mmHg, overall compliance of the fatigue-tested grafts was 3.48±1.27%mmHg(-1)×10(-2) with no significant difference compared to control (3.26±0.65%mmHg(-1)×10(-2); p = 0.47). DSC and TMA showed comparable thermotropic transition.


CONCLUSIONS
Simulated physiological in vivo hydrodynamic loading has no significant degradative effect on an innovative sutureless stent-graft made from POSS-PCU nanocomposite polymer. Sutureless technology incorporating nitinol stents proved to be robust, with no separation over an accelerated 10-year cycle, which may allow development of durable stent-grafts with better compliance.
Department of Vascular Surgery, Royal Free London NHS Foundation Trust, London, UK.
Mital
M
Desai
Raheleh
R
Bakhshi
Xiang
X
Zhou
Marianne
M
Odlyha
Zhong
Z
You
Alexander M
AM
Seifalian
George
G
Hamilton
D000497:Alloys / Q000737:chemistry*; D001014:Aortic Aneurysm / Q000601:surgery*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation*; D002151:Calorimetry; D003187:Compliance; D057446:Hydrodynamics; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D017646:Organosilicon Compounds / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011140:Polyurethanes / Q000737:chemistry; D011475:Prosthesis Failure; D011673:Pulsatile Flow; D017550:Spectroscopy, Fourier Transform Infrared; D015607:Stents; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors
D000497:Alloys; D017646:Organosilicon Compounds; D011108:Polymers; D011140:Polyurethanes; C110029:poly(carbonate urea) urethane; C521417:polyhedraloligosilsesquioxane; C013616:nitinol