Development of a Silk Fibroin-small Intestinal Submucosa Small-diameter Vascular Graft with Sequential VEGF and TGF-β1 Inhibitor Delivery for In Situ Tissue Engineering.

The in vivo performance of vascular grafts is often hindered by the occurrence of stenosis. To prevent this outcome, proper endothelialization and limited collagen deposition on the luminal surface play a crucial role. To achieve these conditions, a biodegradable vascular graft with adequate mechanical properties and the ability to sequentially delivery exogenous therapeutic agents was fabricated. In this study, we constructed a dual-release system through coaxial electrospinning by incorporating recombinant human vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) inhibitor into silk fibroin (SF) nanofibers with a core-shell structure to form a bioactive membrane. Plasmid DNA encoding short hairpin RNA, as a TGF-β1 inhibitor, was condensed and encapsulated into SF nanoparticles (NPs), which were distributed in the core of the nanofibers, while VEGF-containing SF formed the shell. The bioactivity of the two agents was protected using aqueous electrospinning. The functionalized SF membrane as the inner layer of the vascular graft was characterized by the release profile, in vitro cell proliferation, and related protein expression. We demonstrated that the plasmid was incorporated into the NPs and inhibited the expression of TGF-β1 via transfection. After coaxial electrospinning, the obtained SF membrane presented favorable biocompatibility and biodegradation, facilitating cell attachment, proliferation, and infiltration. The core-shell structure enabled rapid VEGF release within 10 days and sustained plasmid delivery for at least 21 days. This should lead to the sequential promotion of endothelialization and prevention of excessive collagen deposition. A 2.0-mm-diameter composite vascular graft was finally fabricated by integrating the SF membrane, serving as the inner layer, with decellularized porcine small intestinal submucosa (SIS), serving as the outer layer. The SIS reinforced the graft by conferring mechanical properties, including tensile strength, suture retention, burst pressure, and biomimetic compliance, with the aim of facilitating the integration process under a stable extracellular matrix structure. The bioengineered graft was functionalized with the sequential administration of VEGF and TGF-β1, and with the reinforced and compatible mechanical properties, thereby offers an orchestrated solution for stenosis with potential for in situ vascular tissue engineering applications. This article is protected by copyright. All rights reserved.