Biomimicry-inspired zwitterionic polyurethane used for vascular implants showing water-induced stiffening and preventing intimal hyperplasia in stent

Abstract

Polymeric vascular implants with ideal mechanical properties and biocompatibility are essential for dilating blood vessels and reducing the risk of secondary implant diseases. However, traditional polymer materials are still limited for vascular stents by diminished radial support post-expansion and inadequate surface modification techniques. Herein, we synthesized zwitterionic polyurethanes (ZPUs) featuring hydrophilic side chains derived from betaine sulfonate and full-hard main chains. These ZPUs demonstrate a remarkable increase in modulus during shape recovery in 37 °C warm water, ensuring that the stent remains soft during implantation for easy delivery, but becomes stiff once positioned at the lesion site to provide adequate radial support. The distinctive architecture promotes the migration of hydrophilic side chains to the surface upon hydration, establishing a "core-shell structure" with a hard interior and a highly hydrophilic surface that enhances antithrombotic properties, mitigates inflammation, and curbs intimal hyperplasia. Consequently, ZPUE20 stent showed significantly better blood flow patency than traditional PLA stent in carotid artery implantation for at least 3 months, ensuring the long-term biological safety of implantation. Compared to surface modification of bare stents, ZPU stents avoid the complex and unstable surface modifications. All in all, ZPUs represent a promising material for vascular implants, markedly improving both mechanical performance and biocompatibility.