Good biocompatibility and elastomeric mechanical properties contribute to the success of thermoplastic polyurethanes (TPU) in a range of medical applications such as dialysis tubing and pace maker casings. Increasingly TPUs are being studied for use in vascular grafts as a replacement for other currently used plastics (ePTFE, PET). While avoiding biodegradation was considered for many years optimal for implants, it has more recently been used in a controllable fashion to stimulate tissue regeneration. Ester linkages undergo slow hydrolysis with a rate highly dependent on conditions and the structure of adjacent moieties.

We have focused on aliphatic isocyanates and ester based chain extenders to give TPUs with mechanical performance (modulus, tensile strength, percent elongation) comparable to that of native blood vessels. [1] Materials with promising performance were electrospun and collected as thin-wall narrow tubes. Electrospun prostheses were implanted into rats to replace the infrarenal aorta. After six months, the grafts were explanted and found to be compliant in all cases. Growth of new endothelial tissue was found to be greater in the degradable grafts.[2-4] To tune the mechanical properties and the degadation behaviour different isocyanate building blocks and chain extenders were investigated. [4,5]

[1] S. Baudis, S. Ligon, K. Seidler, G. Weigel, C. Grasl, H. Bergmeister, H. Schima, R. Liska: "Hard-Block Degradable Thermoplastic Urethane-Elastomers for Electrospun Vascular Prostheses"; Journal of Polymer Science Part A: Polymer Chemistry, 50 (2012), 7; S. 1272 - 1280.

[2] H. Bergmeister, S. Baudis, C. Grasl, M. Stoiber, C. Schreiber, I. Walter, R. Plasenzotti, R. Liska, H. Schima: "In vivo evaluation of electrospun, biodegradable and non-degradable elastomeric vascular grafts"; International Journal of Artificial Organs, 34 (2011), 8; S. 641.

[3] H. Bergmeister, N. Seyidova, C. Schreiber, M. Strobl, C. Grasl, I. Walter, B. Messner, S. Baudis, S. Fröhlich, M. Marchetti-Deschmann, M. Griesser, M. di Franco, M. Krssak, R. Liska, H. Schima: "Biodegradable, thermoplastic polyurethane grafts for small diameter vascular replacements"; Acta Biomaterialia, 11 (2015), S. 104 - 113.

[4] M. Enayati, S. Puchhammer, J. Iturri, C. Grasl, C. Kaun, S. Baudis, I. Walter, H. Schima, R. Liska, J. Wojta, J. Toca-Herrera, B. Podesser, H. Bergmeister: "Assessment of a long-term in vitro model to characterize the mechanical behavior and macrophage-mediated degradation of a novel, degradable, electrospun poly-urethane vascular graft"; Journal of the Mechanical Behavior of Biomedical Materials, 112 (2020), 12; S. 735 - 749.[4] K. Seidler, K. Ehrmann, P. Steinbauer, A. Rohatschek, O.G. Andriotis, C. Dworak, T. Koch, H. Bergmeister, C. Grasl, H. Schima, P.J. Thurner, R. Liska, S. Baudis: "A structural reconsideration: Linear aliphatic or alicyclic hard segments for biodegradable thermoplastic polyurethanes?"; Journal of Polymer Science Part A: Polymer Chemistry, 56 (2018), 19; S. 2214 - 2224.

[5] K. Ehrmann, P. Potzmann, C. Dworak, H. Bergmeister, M. Eilenberg, C. Grasl, T. Koch, H. Schima, R. Liska, S. Baudis: "Hard Block Degradable Polycarbonate Urethanes: Promising Biomaterials for Electrospun Vascular Prostheses"; Biomacromolecules, 21 (2020), 1; S. 376 - 387.