Radiopaque bioabsorbable metal composite wires for intravascular devices - Project Summary The long-term goal of this research program is to provide the endovascular, minimally invasive practitioner with an entirely novel biomaterial platform technology for metallic implants that optimize the key primary attributes of mechanical strength, radiopacity, and bioabsorbability. Specifically, while the past 15 years of vascular material development research has focused on bioabsorbable biomaterial development for balloon expandable stents, no formal longstanding investigations have focused on engineering fully absorbable, radiopaque, wire-based braided stents, which offer numerous advantages over balloon-expandable devices. These advantages include low delivery profile, outstanding softness and trackability, and high mesh density for closure of arterial defects such as aneurysms. A significant motivation for developing absorbable braided stents is the potential for reduction in imaging artifacts, chronic thrombosis and inflammation, and obstacles during reintervention. Motivated by these clinically relevant issues, our team previously engineered and tested novel bioabsorbable iron (Fe)-based alloy (Iron-Manganese-Nitrogen, or FeMnN) flow diverters and have demonstrated their efficacy in vitro and in vivo. While promising, our previous research demonstrates some shortcomings. The FeMnN material degrades quickly and non-uniformly, leading to fractures that reduced long term aneurysm healing rates, and did not possess stent metrics similar to industry standards. Additionally, no previous implant, bioabsorbable or not, has overcome the need for permanent radiopaque portions of the implant for X-ray guided surgical implantation, which counteracts the bioabsorbable benefit. Radiopacity is a critical issue in all bioabsorbable materials, as most are not radiopaque and rely on permanent metal materials to generate radiopacity. Our recent biomaterial-based investigation has resulted in the discovery and engineering of a new metal composite, galvanically coupled bioabsorbable metal biomaterial system, which utilizes FeMnN alloy filaments filled with radiopaque and bioabsorbable Mo in their cores. Furthermore, we hypothesize that stents made with FeMnN-Mo composites (by drawn filled tubing, or DFT) will be able to perform as well as industry standards, with the added benefit of homogenous absorption over time, a benefit of the DFT core and multi staged material degradation. We will improve the corrosion performance, mechanical properties, radiopacity, and biological behavior of this new biomaterial composite system in Aim 1 by engineering new alloys/composites for in vitro and in vivo mouse aorta testing. We will further assess whether FeMnN-DFT-Mo flow diverting stents can be applied successfully in the treatment of saccular aneurysms in rabbits in Aim 2. The expertise of our multidisciplinary team, which includes metallurgists, vascular biologists, clinical endovascular therapists, and biomedical engineers, is well suited to execute this research program. Our cross-disciplinary utilizes novel elemental imaging, leading preclinical animal models, and state of the art manufacturing is poised to uncover new discoveries in advanced bioabsorbable metal biomaterials.
