Additive Manufacturing via Rotational-Axis Fused Filament Fabrication of Poly L-Lactic Acid-Based Bioabsorbable Stent: Morphology, Mechanical, Degradation and Biocompatibility Properties.

Abstract

Bioabsorbable stents offer a significant advantage over metallic stents by providing temporary mechanical support to blood vessels and gradually degrading, thereby reducing the risk of long-term complications and restenosis. Polymeric stents, particularly those made from poly(l-lactic acid), have attracted attention for below-the-knee artery interventions because of their biocompatibility and potential for customized geometries and mechanical properties. However, challenges remain in the development of efficient and scalable fabrication techniques for such devices. This study aimed to develop and evaluate a rotational-axis fused filament fabrication method for the fabrication of bioabsorbable polymeric stents with improved mechanical and biological performance. A rotating-mandrel-based multiaxis system was used to print stents with a conventional closed-cell design while exploring variations in seam line overlaps and ring joint formations. Box-Behnken method was employed to systematically study the influence of key printing parameters─extrusion temperature, printing speed, and extrusion flow rate─on critical stent performance metrics: strut width, radial force, and flexural force. Microscopic analysis, radial compression, and three-point bending tests were performed for performance evaluation. Regression models and analysis of variance (ANOVA) revealed that the extrusion temperature and flow rate significantly influenced the mechanical properties. A multiobjective optimization approach was used to minimize the strut width while maximizing the radial and flexural strengths, resulting in a strut width of 205 μm and radial and flexural forces of 2.5 and 0.19 N, respectively, with an extrusion temperature, speed, and value of 200 °C, 90 mm/min, and 120%, respectively. Further characterization using microtomography and surface profilometry confirmed the structural integrity, consistent strut morphology, and surface quality. Accelerated degradation tests and in vitro biocompatibility assessments demonstrated favorable degradation profiles and cytotoxicity. A 95% mass change was observed in the printed stent after 10 d of accelerated degradation. This study presents a robust rotational-axis FFF method for scalable, bioabsorbable, and patient-specific stent fabrication.