L. Pocivavsek1, J. Pugar3, N. N. Nath2, K. Salem2, W. Wagner2, S. Ye2, E. Tzeng2, S. Velankar3 1The University Of Chicago,Vascular/Surgery,Chicago, IL, USA 2University Of Pittsburgh,Vascular/Surgery,Pittsburgh, PA, USA 3University Of Pittsburgh,Chemical Engineering,Pittsburgh, PA, USA
Introduction: The inner surfaces of arteries and veins are naturally anti-thrombogenic, whereas synthetic materials placed in blood contact commonly experience thrombotic deposition that can lead to device failure or clinical complications. We present a bioinspired strategy for self-cleaning anti-thrombotic surfaces using actuating surface topography motivated by our biomechanical study of arterial topography.
Methods: Utilizing finite element simulations, we studied the evolution of arterial topography as a function of pressure. Arterial luminal and wall geometries were segmented from histology slides of un-fixed human and mouse muscular arteries. The reconstructed arteries were imported into the finite element software ABAQUS, and simulations at physiologic conditions were conducted. Experimental counterparts were constructed utilizing silicone composites cylinders, 3 mm in diameter, and with varying luminal wrinkle wavelengths between 50 and 1000 microns. The cylinders were actuated at 1 Hz between diastolic and systolic pressures while filled with whole blood. At the end of 3 hours of actuation, the adhered surface platelet density was measured.
Results: The luminal surface at zero pressure is highly wrinkled with a large local curvature that is proportional to the inverse of the wrinkle wavelength. Computationally, we found that upon inflation, the arterial luminal topography changes from this highly wrinkled state to a nearly flat surface upon reaching systolic pressures (see figure 1I). Experimentally, we found that topographic surface actuation dramatically decreased surface platelet adhesion: 90%, 95%, and 98% decrease in platelet deposition relative to unactuated surfaces for 1000, 250, and 80 micron wavelength surfaces, respectively (see figure 1 II A-C). Furthermore, we found a strong correlation between the degree of surface self-cleaning and wavelength; shorter wavelengths proved to be far more efficient at preventing un-wanted platelet adhesion than longer wavelengths.
Conclusion: We show that arterial topography in native vessels can actuate as a function of physiologic pulse pressure. Furthermore, such active surface topography is shown in an experimental system to prevent platelet adhesion, with smaller wavelengths being more effective than longer ones at surface renewal. This work presents a novel bio-mimetic strategy geared towards creating durable small caliber vascular grafts with long term patency by preventing unwanted platelet surface fouling.
