Abstract

A vascular graft should mimic the structure and properties of the native artery which has a layered structure. The media layer of native arteries contributes the main mechanical support to the vessel and the intima layer, lined with endothelial cells, provides a smooth antithrombogenic surface for circulating blood. To mimic this arterial structure and property, this study focused on fabricating a layered vascular graft with hydrogel and fibre layers to match the compliance properties of native arteries, which is a critical property to smooth the pulsatile blood flow in circulation. Firstly, the feasibility of preparing polyvinyl alcohol (PVA) based hydrogels with controllable mechanical property was investigated. Three PVA based hydrogels were prepared by blending PVA with chitosan, gelatin or starch and by treatment with freeze-thaw cycles and coagulation. The synergistic crosslinking with the freeze-thaw technique and coagulation was found as a versatile method to control the structure and mechanical properties of PVA-based hydrogels. A further study was focused on the microstructure formation of PVA/Gelatin hydrogel. The results showed that the freeze-thaw cycles increased the strength of hydrogels by growing the crystal domains in the PVA matrix. The coagulation treatment strengthened the mechanical properties of the hydrogels by increasing the overall polymer fraction of the hydrogels. Polyvinyl alcohol with styrylpyridinium pendent groups (PVA-SbQ) is a photosensitive polymer. PVA-SbQ fibres were fabricated by electrospinning and photocrosslinking techniques. The photocrosslinked PVA-SbQ fibre presented water-insoluble properties. Preliminary endothelial cell culture result showed evidence that the PVA-SbQ fibres could potentially act as a cell lining substrate. Finally, a duo-layer vascular graft was constructed with one outer layer composed of a PVA based hydrogel and one inner layer of composed of PVA-SbQ fibres. The mechanical properties, especially the compliance, of the as-prepared duo-layer graft were shown to closely match with that of selected native arteries.