Fabrication of continuous iron wire reinforced poly-L-lactic acid (PLLA) filaments for producing biodegradable stents via a braiding process

• Novel fabrication of continuous iron wire reinforced PLLA (CIWR-PLLA) filaments was achieved using custom crosshead extrusion. • Mechanical performance of CIWR-PLLA stents nearly doubled in radial compression force compared to pure PLLA stents. • Biocompatibility confirmed through Caco-2 and THP-1 assays, showing minimal cytotoxicity and low inflammatory response. • Controlled degradation observed in CIWR-PLLA, with structural integrity maintained up to 6 weeks (≈6 months physiological time). • Application potential demonstrated for next-generation biodegradable stents combining strength, safety, and bioresorption. Poly-L-lactic acid (PLLA) is widely used in medical applications due to its excellent biodegradability and biocompatibility. However, its limited mechanical strength poses challenges for applications like biodegradable stents, which require both strength and flexibility. In this study, continuous iron wire reinforced PLLA (CIWR-PLLA) filaments were fabricated using crosshead extrusion to enhance the mechanical properties of PLLA. The tensile strength and Young's modulus of CIWR-PLLA filaments were significantly improved to 69.3 ± 1.12 MPa and 3.4 ± 0.17 GPa, respectively, compared to 36.7 ± 1.21 MPa and 2.6 ± 0.03 GPa for pure PLLA. Stents braided from CIWR-PLLA filaments exhibited nearly double the radial compression force compared to those made from pure PLLA, demonstrating superior mechanical performance. Cytotoxicity assessments using Caco-2 cells confirmed that both PLLA and CIWR-PLLA are non-toxic and biocompatible. The immunological study demonstrates that CIWR-PLLA exhibits excellent biocompatibility, eliciting minimal macrophage activation and only mild epithelial cytokine response, confirming its suitability for implantable medical applications. Accelerated degradation studies conducted at 50°C revealed that CIWR-PLLA maintained structural integrity longer than PLLA due to the reinforcing effect of the iron wire. Significant morphological changes and mass reduction were observed from week 6 onward, indicating this as a critical degradation point, equivalent to approximately six months at 37°C. These results suggest that CIWR-PLLA filaments offer improved mechanical performance, biocompatibility, and controlled degradation, making them promising candidates for next-generation biodegradable stent application.