Mechanical behavior of polyurethane-based small-diameter vascular grafts

F. MONTINI BALLARÍN; G.A. ABRAHAM; P.C. CARACCIOLO

Advances in Polyurethane Biomaterials

Woodhead Publishing

Lugar: Chennai; Año: 2016; p. 451 - 477

Recently, bioactive PU tubular scaffolds havebeen developed. Strategies such as the incorporation of single or multiplegrowth factors, with different delivery profiles, surface modification of thegraft lumen with antithrombogenic molecules like heparin, and even thesynthesis and utilization of novel non-thrombogenic polymers have been employed.In some studies, the influence of these modifications on mechanical properties wasalso examined, along with the grafts biological properties. Besides advances in the synthesis and processingof biodegradable PUs conducted in recent years, their utilization insmall-diameter vascular grafts is still very sparse. In addition, there are fewstudies where a complete characterization of the mechanical behavior under physiological conditions was performed. There is a dilemma about which PU type is more appropriatefor vascular grafts long term implantation. The use of biostable SPEUs has shownoxidative degradation and also an increase in graft stiffness afterimplantation due to the load supported by the polymer and new host tissue aswell. However, the use of biodegradable PUs may also have a weakness. If thetissue that replaces the degrading graft does not have the biomechanicalproperties to support the internal load, the development of weak spots afterimplantation and subsequently aneurism formation can occur. The synchronizationbetween the degradation rate and the time to regenerate new vascular tissuewith adequate mechanical behavior is crucial for the grafts success whenbiodegradable polymers are used. Therefore, it is important to evaluate thevascular graft?s mechanical behavior over implantation time. Very few workshave performed such studies with biostable PUs and even less with biodegradable PUs. The development of an off-the-shelfsmall-diameter vascular graft for bypass surgery with proper mechanicalproperties and biologic response is still an ongoing issue of current researchin the field of vascular tissue engineering.