First in vivo evaluation of biomimetic fluorosurfactant polymer-coated expanded polytetrafluoroethylene vascular grafts in a porcine carotid artery bypass model Jennifer M. Bastijanic, BS,a Roger E. Marchant, PhD,a Faina Kligman, PhD,b Matthew T. Allemang, MD,c Ryan O. Lakin, MD,c Daniel Kendrick, MD,c Vikram S. Kashyap, MD,c and Kandice Kottke-Marchant, MD, PhD,a,b Cleveland, Ohio Objective: The objective of this study was to evaluate the potential for biomimetic self-assembling fluorosurfactant polymer (FSP) coatings incorporating heptamaltose (M7-FSP) to block nonspecific protein adsorption, the cell adhesive RGD peptide (RGD-FSP), or the endothelial cell-selective CRRETAWAC peptide (cRRE-FSP) to improve patency and endothelialization in small-diameter expanded polytetrafluoroethylene (ePTFE) vascular graft implants. Methods: ePTFE vascular grafts (4 mm in diameter, 5 cm in length) were coated with M7-FSP, RGD-FSP, or cRRE-FSP by dissolving FSPs in distilled water and flowing solution through the graft lumen for 24 hours. Coatings were confirmed by receding water contact angle measurements on the lumen surface. RGD-FSP and cRRE-FSP grafts were presodded in vitro with porcine pulmonary artery endothelial cells (PPAECs) using a custom-designed flow system. PPAEC coverage on the lumen surface was visualized with epifluorescent microscopy and quantified. Grafts were implanted as carotid artery interposition bypass grafts in seven pigs for 33 6 2 days (ePTFE, n [ 3; M7-FSP, n [ 4; RGD-FSP, n [ 3; cRRE-FSP, n [ 4). Patency was confirmed immediately after implantation with duplex color flow ultrasound and at explantation with contrast-enhanced angiography. Grafts were sectioned for histology and stained: Movat pentachrome stain to outline vascular layers, immunofluorescent staining to identify endothelial cells (anti-von Willebrand factor antibody), and immunohistochemical staining to identify smooth muscle cells (anti-smooth muscle a-actin antibody). Neointima to lumen area ratio was determined to evaluate neointimal hyperplasia. Results: Receding water contact angle measurements on graft luminal surfaces were significantly lower (P < .05) on FSP-coated ePTFE surfaces (M7-FSP, 40 6 16 degrees; RGD-FSP, 25 6 10 degrees; cRRE-FSP, 33 6 16 degrees) compared with uncoated ePTFE (126 6 2 degrees), confirming presence of the FSP layer. In vitro sodding of PPAECs on RGD-FSP and cRRE-FSP grafts resulted in a confluent monolayer of PPAECs on the luminal surface, with a similar cell population on RGD-FSP (1200 6 187 cells/mm2) and cRRE-FSP (1134 6 153 cells/mm2) grafts. All grafts were patent immediately after implantation, and one of three uncoated, two of three RGD-FSP, two of four M7-FSP, and two of four cRRE-FSP grafts remained patent after 1 month. PPAEC coverage of the lumen surface was seen in all patent grafts. RGD-FSP grafts had a slightly higher neointima to lumen area ratio (0.53 6 0.06) compared with uncoated (0.29 6 0.15), M7-FSP (0.20 6 0.15), or cRRE-FSP (0.17 6 0.09) grafts. Conclusions: Biomimetic FSP-coated ePTFE grafts can be used successfully in vivo and have potential to support endothelialization. Grafts modified with the M7-FSP and cRRE-FSP showed lower intimal hyperplasia compared with RGD-FSP grafts. (J Vasc Surg 2015;-:1-11.) Clinical Relevance: The development of small-diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts with improved cellular integration and blood compatibility remains a significant clinical challenge, yet it would benefit many patients lacking suitable autologous vessels for small-diameter bypass procedures. We have developed biomimetic, fluorosurfactant polymers that self-assemble on ePTFE grafts and can promote selective endothelial cell attachment while reducing platelet adhesion. The long-term goal with this technology is to produce an easy-to-manufacture, off-the-shelf ePTFE graft with improved endothelialization without altering the underlying ePTFE structure or handling characteristics. Here, we demonstrate that fluorosurfactant polymer-coated grafts can be successfully synthesized and used in vivo.

From the Department of Biomedical Engineering, Case Western Reserve Universitya; the Robert J. Tomsich Pathology and Laboratory Medicine Institute, Cleveland Clinicb; and the Division of Vascular Surgery and Endovascular Therapy, University Hospitals.c This project was supported by Grant No. 5R01HL087843 from the National Heart, Lung, and Blood Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Author conflict of interest: none. Additional material for this article may be found online at www.jvascsurg.org.

Reprint requests: Jennifer M. Bastijanic, Department of Biomedical Engineering, Case Western Reserve University, Wickenden Bldg Rm 208, 10900 Euclid Ave, Cleveland, OH 44106 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2015.01.060

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JOURNAL OF VASCULAR SURGERY --- 2015

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More than 23.5 million people suffer from coronary heart and peripheral vascular disease in the United States alone, resulting in >440,000 bypass procedures performed annually.1 Whereas the use of autologous vessels such as the saphenous vein or mammary artery as the bypass conduit remains the standard of care, 30% to 40% of patients lack a suitable autologous vessel.2-4 Expanded polytetrafluoroethylene (ePTFE) grafts are a common alternative to autologous vessel grafts and are used successfully in large-diameter applications, such as aortobifemoral bypasses.5 However, ePTFE grafts suffer from reductions in patency rate as vessel diameter decreases below 6 mm. In fact, only 38% of ePTFE grafts remain patent after 5 years in femoropopliteal bypasses,6 and