Biodegradable Vascular Patches for Arterial Reconstruction: In Vitro Study and Long-Term Implantation in a Sheep Model

Background/Objectives: The development of biodegradable materials for cardiovascular surgery that promote gradual replacement with native tissue is a key scientific challenge. Silk fibroin (SF) is a naturally derived biodegradable material with low immunogenicity and good biocompatibility. This study compared the in vitro and in vivo properties of SF patches with bovine pericardium (BP). Methods: SF and BP patches were characterized for ultrastructure, physico-mechanical properties, hydrolytic degradation, protein adsorption, hemocompatibility, and in vitro biocompatibility. SF and BP patches were implanted into sheep carotid arteries for 2, 6, and 12 months, with intravital ultrasound and optical coherence tomography (OCT) monitoring, followed by morphological examination. Results: The SF patch exhibited a porous-fibrous structure, uniaxial tensile properties similar to those of native arteries, and resistance to in vitro hydrolytic degradation for 12 months. It caused no hemolysis, minimal platelet aggregation, and in vitro biocompatibility comparable to BP. At 2 months of implantation, both types of patches showed no stenosis, aneurysms, or calcification, with endothelial-like cell coverage. At 6 months, SF patches displayed minimal degradation, no calcification, and no neointimal hyperplasia (NH), whereas BP patches showed delamination and NH. At 12 months, NH was observed in both groups; the degrading SF patch was partially replaced by host tissue, maintaining a three-component tissue organization comprising neointima, residual patch material, and neoadventitia, whereas the BP patches exhibited focal calcification. Conclusions: The SF patch showed promising in vitro and in vivo performance, artery-like tensile properties, and partial hemocompatibility. However, elastin absence and 12-month NH warrant further optimization of the material.