Accelerated in vitro degradation and structural integrity of additively manufactured poly (L-lactic acid) esophageal stents

This study examines the hydrolytic degradation behavior and chemo‑mechanical stability of additively manufactured poly (L‑lactic acid) (PLLA) esophageal stents with two representative strut thicknesses (0.8 and 1.6 mm). Accelerated in vitro degradation was conducted in phosphate‑buffered saline at 50 °C for up to 90 days. The evolution of molecular weight, crystallinity, thermal transitions, and mechanical performance was systematically characterized using gel permeation chromatography, differential scanning calorimetry, and three-point bending and radial compression tests. The results demonstrate that degradation is governed by bulk‑dominated hydrolysis with autocatalytic characteristics, leading to a pronounced reduction in molecular weight that is largely independent of strut thickness. In contrast, crystallinity evolution and mechanical integrity exhibit a strong thickness dependence. While thinner stents provide greater initial flexibility, they undergo a rapid loss of load‑bearing capacity during degradation, whereas thicker stents retain mechanical stability for a longer period despite reduced initial compliance. Correlation analysis reveals that the degradation‑induced decline in load‑bearing capacity is primarily controlled by molecular weight reduction, whereas radial stiffness is more strongly associated with crystallinity changes. Overall, this work provides quantitative insight into the coupled chemical and mechanical degradation of semi‑crystalline PLLA structures and highlights strut thickness as a critical design parameter governing the balance between flexibility and durability in biodegradable polymeric stents.​