A mechanically interlocked bilayered small-diameter vascular graft with SilMA-PVA hydrogel and biaxially expanded polytetrafluoroethylene for promoting cytocompatibility

Conventional PTFE tubes only expand axially and exhibit low radial strength and poor elasticity, which limits their clinical translation in small-diameter vascular grafts. In this study, biaxial stretching was employed to endow the ePTFE tubes with node-fibril microstructure, thereby enhancing both flexibility and circumferential strength. A novel bilayer small-diameter vascular graft, consisting of an outer ePTFE layer and an inner functional SilMA-PVA hydrogel layer, was successfully fabricated. The outer PTFE material exhibited better flexibility and a higher porosity through biaxial expansion. The inner SilMA-PVA hydrogel was prepared by mixing methacrylated silk fibroin (SilMA) with PVA solution, followed by UV-induced photocrosslinking. This design leveraged biaxially expanded PTFE to deliver superior mechanical support, while the SilMA-PVA hydrogel endowed the luminal surface with excellent biocompatibility and promoted the adhesion and proliferation of endothelial cells. Scanning electron microscopy (SEM) confirmed a tightly integrated interface arising from the physical interlocking of hydrogel with the porous ePTFE structure. Additionally, the incorporation of PVA into the SilMA hydrogel was found to form a dense, interconnected porous network that supports cellular adhesion and growth while preserving a biocompatible surface. This composite structure enhanced bonding with the outer ePTFE layer, and mechanical testing verified that the biaxial expansion process substantially improved the mechanical properties of the ePTFE graft. In summary, this synergistic combination makes it a promising candidate for small-diameter vascular substitution.