New methods for in vivo degradation testing of future stent materials

Selection of a degradable material for cardiovascular stent application is a difficult task. Beside various alloys, different processing routes, annealing and surface treatment options, and coatings are available. Unfortunately, the in vivo properties of materials cannot be reliably predicted in vitro. In order to narrow down the selection there is a great need for an easy and fast in vivo pre-selection method for possible stent materials. In this study we tested an approach presented by another group. It was compared to our new approach, the Carrier Stent. Here, several material samples are sewn on an inert, polymeric stent. It can be implanted in virtually every vessel of an animal model. It enables testing of different materials at the same location. Mg10Gd was chosen as an example for a degradable alloy for future stent applications. Wires were produced by drawing, annealed, etched, and analyzed. Due to the short wire lengths, a new clamping method for tensile tests was developed. Different heat treatments and etching processes were evaluated prior to the implantations. Both direct wire implantation and carrier stent implantation were performed and compared.