A novel gradient and multilayered sheet with a silk fibroin/polyvinyl alcohol core-shell structure for bioabsorbable arterial grafts

Bioabsorbable arterial grafts can potentially improve patency and neovessel formation; however, their application in clinical settings has not been realized. In this study, we developed bioabsorbable gradient sheets based on silk fibroin (SF) and polyvinyl alcohol (PVA) with a core-shell nanofibrous structure. This gradient sheet was expected to promote vascular remodeling while we maintained its physical properties and a gradual degrading process from the luminal surface. ESP was conducted at various flow rates for SF and PVA to achieve the multilayer gradient structure. Furthermore, the elasticity of the gradient sheet could be increased by increasing the PVA flow rate; however, this reduced the tensile strength of the core-shell fibers. Notably, the physical properties of the gradient sheet did not degrade even after 7 days of immersion in a phosphate buffer saline solution, which indicates that the structure could maintain its structural integrity while resisting arterial pressure. In vitro experiments revealed that the number of endothelial cells attached to the SF/PVA sheet was notably higher than that on the cell-culture dish. The gradient sheets were implanted in rat abdominal aortas and explanted after 14 days to confirm acute-phase patency and vascular remodeling. The gradient sheets constructed with SF composed of polyurethane and PVA improved the ease of handling of the material, and these sheets resulted in a favorable vascular remodeling outcome. Our results strongly suggest that the SF/PVA-based gradient sheets described in this study can serve as a novel design for bioabsorbable arterial grafts upon further modifications.