The Development of a Magnesium Biodegradable Stent: Design, Analysis, Fabrication, and In-vivo Test

Abstract

Stents are widely used as scaffolding to open up blood vessel stenosis. A stent can provide early stage scaffolding, increase blood flow, and optimize hemodynamics. Stainless steel is the most popular material for conventional stents, and it has excellent mechanical behavior during deformation. On the downside, stents made of stainless steel remain in the body permanently and may cause complications or lead to occlusion of the vessel. Biodegradable stents that eventually dissolve and disappear in the body are being developed to overcome these shortcomings. However, biodegradable materials such as magnesium alloys are relatively brittle and cannot deform as much as stainless steel. A proper geometry for the stent that allows large displacement and plastic deformation is necessary and required. In this paper, a balloon-expandable design of magnesium AZ31 alloy venous stent is proposed and evaluated. Computational analysis using finite element analysis (FEA) tools simulated the expansion and recoiling process. The stent was expanded from 6.0 mm to 10.0 mm in the radial direction with the expansion ratio of 1.67. Strain and stress distributions, structural stiffness, and radial strength were studied. The maximum stress did not exceed the ultimate tensile strength (in the plastic region) of the stent material, and the maximum strain was 64% of the elongation. The stent design was then fabricated with methods of electro-discharge machining (EDM), laser machining, and electro-polishing. Lastly, these prototyped stents were prepared for future in-vivo experiment in animal models.