(Bio)degradable Urethane-Elastomers for Electrospun Vascular Grafts
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1235-RR03-30
(Bio)degradable Urethane Elastomers for Electrospun Vascular Grafts. Stefan Baudis,1 Maria Schwarz,1 Christian Grasl,2 Helga Bergmeister,3,4 Guenter Weigel,3 Heinrich Schima,2 Robert Liska;1 1 Institute of Applied Synthetic Chemistry, Division Macromolecular Chemistry, Vienna University of Technology, Getreidemarkt 9/163MC, 1060 Vienna, Austria 2 Center for Biomedical Engineering and Physics, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria 3 Ludwig-Boltzmann Cluster for Cardiovascular Research, 4 Divison for Biomedical Research, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria ABSTRACT Electrospinning is a very powerful method to create cellular scaffolds for regenerative medicine – especially for artificial vascular grafts. Commercially available thermoplastic polyurethane elastomers (TPUs), like Pellethane™ are FDA approved and have already shown excellent biomechanical properties as electrospun vascular grafts. In order to induce the growth of a neo-artery and hence increase the long-term patency of the graft, the use of biodegradable TPUs is beneficial. Therefore we aim for the development of degradable TPUs. In preliminary studies the mechanical properties of segmented TPUs were examined. The tendencies of the properties of the compression-molded bulk materials were also found for the electrospun materials. It could also be shown that the substitution of the aromatic 4,4'-methylene diphenyl diisocyanate building blocks in Pellethane™ with the aliphatic hexamethylene diisocyanate – to avoid toxic aromatic amines as degradation products - only causes minor loss of strength. To obtain degradable TPUs, our concept is to incorporate cleavable ester bonds into the polymer chain. For this purpose, lactic- and terephthalic ester-based cleavable chain extenders were used. The expected degradation products showed no cytotoxicity in-vitro. Degradation tests of polymer samples in phosphate buffered saline at elevated temperatures confirmed the degradability of the new polymers. INTRODUCTION Diseases of the cardiovascular system are one of the main causes of morbidity and mortality in the western hemisphere. Surgical therapy of cardiovascular disorders frequently requires the replacement of the diseased tissue with prosthetic grafts. Autologous vessels are the preferred replacement grafts, but many patients have no suitable vessels for harvest due to coexisting diseases or reoperation. The search for vascular substitute materials was thus directed at bioinert materials that minimally interact with blood and tissue. Elastic polymers, like expanded polytetrafluorethylene (ePTFE) or polyethylene terephthalate (PET) are currently the standard prosthetic materials which are used in vascular surgery. However, these synthetic materials have proved to be inferior to autologous conduits, especially when used for small caliber vessels or in low-flow applications. The main reasons for the poor performance are anastomotic intimal hyperplasia and innate surface throm
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