Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods

Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin which is widely used as an anticoagulant drug, was loaded by blending in gelatin solution and emulsion electrospinning of PCL fibers. Adding heparin resulted in better endothelial cell attachment and proliferation while fewer platelets attached to the scaffold. This indicates that that probability of graft failure as a result of thrombosis can be reduced. The outer layer was fabricated using freeze-drying of gelatin hydrogel. With average pore diameter size of >200 μm, large smooth muscle cells (SMC) could proliferate easily along this layer. Mechanical tests demonstrated the more appropriate mechanical properties of the bilayer scaffold in comparison with the freeze dried or electrospun layer individually.