Development and investigation of polymeric vascular graft materials

Vascular disease leading to stenotic or occluded arteries and subsequent ischemia is often treated using bypass grafts. Although autologous material, the preferred source for constructing a bypass graft, often provides a graft with satisfactory patency rates, it is not always available and suitable for use. In these cases synthetic material is often utilised but these rarely produce the patency of autologous material. The causes of their failure are compliance mismatch and thrombus formation. For this reason, polyurethane was studied as a suitable graft material due to its compliant nature and excellent thromboresistance. Investigations into the effect of the material stiffness and potential to allow adsorption of blood-borne proteins were conducted, showing that an optimum combination of the two existed for the migration of vascular tissue onto the graft. As this migration can lead to restenosis and reocclusion of a graft, the ability to control the migration rate could limit the failure of the graft through these processes. The electrospinning technique was utilised to develop a polyurethane processing method for producing fibrous materials which better replicate the geometry of the native vessel than do other materials commonly used. The effect of this fibrous structure was to maintain the differentiated state of the vascular cells resident upon it. This contractile state is consistent with that in which cells are found in a healthy vessel and is the opposite state to that of the synthetic phenotype in which cells are found when on planar surfaces in vitro and in diseased vessels. It therefore follows that the control of the phenotypic state can prevent the dedifferentiation of the cells into the synthetic state, whereupon they form a thickening of the vessel wall which, again, ultimately results in restenosis. Mechanical deformation of these electrospun materials was conducted in a dynamic system, replicating the motion in the vascular system in vivo. The effect of this dynamic system was to further develop the degree to which the cells demonstrated a contractile phenotype. This highlights that the electrospun polyurethane graft material represents a promising alternative to those commonly used, perhaps due to it somewhat recapitulating the topographical and mechanical nature of the native vessel.

Name dc:type.qualificationname

engd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2012

Author dc:creator

• Whitton, Andrew

DOI

10.48730/5nya-mx71

Identifier

T13132

OAI identifier oai:identifier

oai:strathclyde:6108vb24b