Endothelial and smooth muscle cell interactions with a PCL-PU composite vascular scaffold with potential for bioactive release

INTRODUCTION: We have developed a polycaprolactone (PCL) - polyurethane (PU) composite scaffold material (Figure 1) which is a promising alternative for small diameter vascular grafts. This scaffold could provide increased compliance and thus reduce mismatch with native blood vessels. The scaffold also provides a favourable luminal surface for endothelial cell (EC) attachment, as well as a porous anti-luminal surface for smooth muscle cell (SMC) attachment and migration. In this study, we examined how human umbilical venous endothelial cells (HUVECs) adhered to the luminal surface of the prosthesis and, for an improved functional vascular graft, SMCs were seeded to the anti-luminal surface of the prosthesis. METHODS: The morphology and phenotype of HUVECs and SMCs was assessed on the scaffolds using environmental scanning electron and immunofluorescence microscopy. Endothelial functional behavior assays were used to assess the release of nitric oxide and von Willebrand factor (vWF) under stimulation. The demonstration that sustained release of therapeutic proteins is possible has stimulated the development of new implantable polymers and devices which controlled delivery of growth factors (3). The scaffolds were loaded with 0.67% and 0.5% (w/w) lyophilised trypsin (25kDa) (a "model" growth factor) to assess protein release and activity in vitro over a period of 4 days.