# In Vitro Degradation Studies of 3D-Printed Thermoplastic Polyurethane for the Design of Vascular Implant

## TL;DR

This study examines how 3D-printed thermoplastic polyurethane stent-grafts degrade over time under simulated physiological conditions, showing they remain durable and safe for vascular use.

## Contribution

The study provides novel insights into the long-term stability of 3D-printed TPU under accelerated aging conditions relevant to vascular implants.

## Key findings

- Hydrolytic aging reduced crystallisation and melting enthalpy by 41% and 29%, respectively.
- Mechanical performance remained within clinically acceptable ranges despite minor chemical changes.
- Additive migration was observed, but chain scission was minimal.

## Abstract

Three-dimensional printing has emerged as a promising technology in endovascular surgery for the production of patient-specific stent-grafts. Thermoplastic polyurethane (TPU) is widely used for this purpose due to its favourable biocompatibility, hemocompatibility, and mechanical properties. However, its long-term stability under physiological conditions remains uncertain. This study evaluates the ageing behaviour of 3D-printed TPU stent-grafts under accelerated oxidative conditions (20% H2O2–0.1 M CoCl2) over three months, corresponding to approximately 45 months in vivo, and during three months in hydrolytic (0.1 M NaOH) conditions. Mechanical, physicochemical, thermal, and surface properties were periodically analysed. Differential scanning calorimetry revealed a decrease in crystallisation enthalpy of 41% and a reduction in melting enthalpy of 29% after hydrolytic ageing, whereas no decrease was observed after oxidative ageing. Despite these chemical changes, size exclusion chromatography indicated minimal chain scission. However, spectroscopy and microscopy showed minor chain scission and additive migration (antioxidant and lubricant). Nevertheless, tensile testing highlighted that mechanical performance remained within clinically acceptable ranges. These findings demonstrate that 3D-printed TPU vascular implants retain essential properties under prolonged simulated ageing, supporting their safety and durability for vascular applications.