Surface-modified bioresorbable electrospun scaffolds for improving hemocompatibility of vascular grafts

The replacement of small-diameter vessels is one of the main challenges in tissue engineering. Moreover, the surface modification of small-diameter vascular grafts (SDVG) is a key factor in the success of the therapy due to their increased thrombogenicity and infection susceptibility caused by the lack of a functional endothelium. In this work, electrospun scaffolds were prepared from blends of poly(L-lactic acid) (PLLA) and segmented polyurethane (PHD) with a composition designed to perform as SDVG inner layer. The scaffolds were then successfully surface-modified with heparin following two different strategies that rely on grafting of heparin to either PLLA or PHD functional groups. Both strategies afforded high heparin density, being higher for urethane methodology. The functionalized scaffolds did not cause hemolysis and inhibited platelet adhesion to a large extent. However, lysozyme/heparin-functionalized scaffolds obtained through urethane methodology achieved the highest platelet attachment inhibition. The increase in hydrophilicity and water absorption of the surface-functionalized nanostructures favored adhesion and proliferation of human adipose-derived stem cells. Heparinized surfaces conjugated with lysozyme presented microbial hydrolysis activity dependent on heparin content. Overall, a better performance obtained for urethane-modified scaffold, added to the fact that no chain scission is involved in urethane methodology, makes the latter the best choice for surface modification of PLLA/PHD 50/50 electrospun scaffolds. Scaffolds functionalized by this route may perform as advanced components of SDVG suitable for vascular tissue engineering, exhibiting biomimetic behavior, avoiding thrombi formation and providing antimicrobial features.