Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik
Coronary heart disease is generally treated by the implantation of metal stents. However, treatment with metal stents can have undesirable side effects such as degradation of blood components or restenosis. In order to minimize these effects, absorbable polymer stents have been developed which dissolve after successful treatment of the stenosis. In this work, bioabsorbable stents were produced from biopolymers and compounds such as polylactic acid (PLA) and polycaprolactone (PCL) using an additive manufacturing process. First, the absorbable polymers were examined for their thermal behavior and their suitability for the additive manufacturing of stent structures via differential scanning calorimetry. Test structures were then manufactured from the selected polymers using a pellet printer. Various methods were applied to determine the mechanical and surface properties of the test structures, including tensile tests and microscopic analyses. The absorbable polymers were printed directly onto a cylindrical shaft in a specialized FDM printer with a custom-made nozzle to manufacture stents with a layer thickness b ≤ 130 µm and a corresponding process time t < 250 s. A variety of stent geometries were evaluated to enhance the ability of the polymer stent to undergo crimping. Subsequent tests involved the coating of stent structures with active substances, such as sirolimus or paclitaxel, in order to develop a cytostatic drug coating.
Abstract
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