Radiopaque FeMnN-Mo composite drawn filled tubing wires for braided absorbable neurovascular devices

• Published in: Bioactive materials Vol. 40; pp. 74 - 87
• Main Authors: Griebel, Adam J., Maier, Petra, Summers, Henry, Clausius, Benjamin, Kanasty, Isabella, He, Weilue, Peterson, Nicholas, Czerniak, Carolyn, Oliver, Alexander A., Kallmes, David F., Kadirvel, Ramanathan, Schaffer, Jeremy E., Guillory, Roger J.
• Format: Journal Article
• Language: English
• Published: China Elsevier B.V 01.10.2024; KeAi Publishing; KeAi Communications Co., Ltd
• ISSN: 2452-199X; 2452-199X
• DOI: 10.1016/j.bioactmat.2024.06.002

Flow diverter devices are small stents used to divert blood flow away from aneurysms in the brain, stagnating flow and inducing intra-aneurysmal thrombosis which in time will prevent aneurysm rupture. Current devices are formed from thin (∼25 μm) wires which will remain in place long after the aneurysm has been mitigated. As their continued presence could lead to secondary complications, an absorbable flow diverter which dissolves into the body after aneurysm occlusion is desirable. The absorbable metals investigated to date struggle to achieve the necessary combination of strength, elasticity, corrosion rate, fragmentation resistance, radiopacity, and biocompatibility. This work proposes and investigates a new composite wire concept combining absorbable iron alloy (FeMnN) shells with one or more pure molybdenum (Mo) cores. Various wire configurations are produced and drawn to 25–250 μm wires. Tensile testing revealed high and tunable mechanical properties on par with existing flow diverter materials. In vitro degradation testing of 100 μm wire in DMEM to 7 days indicated progressive corrosion and cracking of the FeMnN shell but not of the Mo, confirming the cathodic protection of the Mo by the FeMnN and thus mitigation of premature fragmentation risk. In vivo implantation and subsequent μCT of the same wires in mouse aortas to 6 months showed meaningful corrosion had begun in the FeMnN shell but not yet in the Mo filament cores. In total, these results indicate that these composites may offer an ideal combination of properties for absorbable flow diverters. [Display omitted] •The DFT composite approach with Mo as a core material can be used to increase radiopacity of FeMnN wires as fine as 25 μm.•Mo core(s) can provide a mechanical tuning effect to FeMnN wires, where the relatively high modulus results in higher crush resistance of FeMnN-DFT-Mo stents.•FeMnN-DFT-Mo composites demonstrate sensitivity in vitro to corrosion progression when corrosion fluid parameters such as protein content are changed.•FeMnN-DFT-Mo composites demonstrate absorbability out to six months in mouse aortas, with FeMnN acting as the sacrificial anode.•In the FeMnN-DFT-Mo system, Mo corrosion has not been observed up to 6 months in vivo, demonstrating the sacrificial anode effect of the galvanic pairing as a guard against premature wire fracture.