Multi-layered electrospun grafts for surgical repair: Biomimicking physiological ascending aortic compliance

Commercially available Dacron (woven polyester) grafts are used for routine open surgical repair of thoracic aortic aneurysms. Despite durable and biocompatible, these grafts do not reproduce the natural mechanical properties of the aorta. Therefore, the aim of this project was to develop an innovative graft that additionally exhibits physiological aortic compliance. To achieve this result, multi-layered tubular aortic grafts were created by electrospinning of a thermoplastic polyurethane. To reduce permeability, a gelatin-coating was added. Three groups (G_1-3; n = 5) with varying layer designs were evaluated regarding the main mechanical properties of vascular grafts such as suture retention strength, permeability and static and dynamic compliance. G₃, which combined electrospinning with a stable silicone-coated inlay was chosen for the fabrication of medical grade thermoplastic polyurethane grafts (G_m; n = 6). Dynamic compliance values of 19.68 ± 11.5%/100 mmHg (50-90 mmHg), 15.18 ± 8.7%/100 mmHg (80-120 mmHg) and 14.56 ± 7.4%/100 mmHg (110-150 mmHg) were achieved. The compliance was higher than for Dacron and ePTFE grafts and comparable to the normal sized ascending aorta of around 16%/100 mmHg in a healthy human and porcine aortic compliance of 14.3%/100 mmHg. Static compliance was successfully tested up to 350 mmHg. No significant changes in graft diameter or delaminations of the graft layers were detected after compliance testing. Therefore, by combining electrospinning with a durable inlay, both elasticity and recoverability are obtained, resulting in a promising alternative to the gold-standard in open-surgical treatment of thoracic aortic pathologies.