Coaxially electrospun heparin-eluting scaffolds for vascular graft application

Abstract

The use of electrospun scaffolds for small diameter vascular grafts ( 0.9 MPa, maximum strain > 100 %, suture retention > 2.4 N) or within groups between the longitudinal and circumferential tensile properties. After 6 weeks of in vitro degradation, all groups exhibited similar mechanical losses of approximately 40 % in ultimate tensile stress and 80 % in maximum elongation in circumferential and longitudinal directions. The smaller vascular grafts had burst pressures superior to native vasculature and compliances approximating those of healthy arteries. Thermal analyses (DSC) of the different groups showed similar thermograms with little intergroup variation and indicated that the electrospinning process did not unduly affect the thermal properties or crystallinity, of DP30. There was also no major variations in thermograms of degraded samples. Blend electrospun scaffolds showed the expected initial burst release of HepTBA (47.7 %, 3 days) followed by a sustained release (56.1 %, 6 weeks). Coaxially incorporated HepNa+ also exhibited initial burst release (67.5-69.7 %, 3 days) for both the low and high heparin content groups followed by improved sustained release (81.9 - 97.7%, 6 weeks). Coaxial incorporation had a 2× higher heparin encapsulation efficiency than blend incorporation (approaching 100 %). Heparin, post-TBA-modification, did not fully retain its antithrombotic properties (54.9 % reduction), which was further reduced after incorporation and release (24.2 % reduction). HepNa+ , however, retained its full antithrombotic activity post coaxial incorporation and elution. Coaxial electrospinning of heparin in DP30 shows potential for producing small diameter vascular grafts with mechanical properties comparable to small blood vessels. Although some initial burst release occurred, the sustained release over 6 weeks, incorporation of heparin without the need for modification at improved efficiency, and the retained activity of the heparin after electrospinning incorporation and elution; holds promise for vascular graft applications. Future work should aim for the production of continuous cores within fibre morphology and evaluating graft performance in an in vivo model to determine whether an appropriate and sufficient amount of heparin has been included to affect the desired response