Controlled Degradation of Poly(L‐Lactic Acid)/Trimethylene Carbonate/Magnesium Hydroxide Composite Bioresorbable Stent: Synergistic Effects on Long‐Term Resorption and Mechanical Support

Bioresorbable vascular scaffolds (BVS) are promising alternatives to metallic stents, yet poly(L‐lactic acid) (PLLA) scaffolds suffer from slow degradation and inflammatory acidic byproducts. Here, we developed a PLLA‐based composite stent incorporating poly(L‐lactide‐co‐trimethylene carbonate) (PLLA‐co‐TMC) and magnesium hydroxide (MH) to achieve controlled degradation. A comprehensive 24‐month in vitro study evaluated long‐term physicochemical and mechanical evolution. While pure PLLA exhibited negligible mass loss (<4%) over 24 months, the PLLA‐TMC‐MH scaffold demonstrated biphasic behavior: maintaining mechanical integrity during the initial 6‐month remodeling phase with a 34% increase in radial force (reaching 37.64 N), followed by accelerated decomposition (>20% mass loss) by 24 months. The weight‐average molecular weight of PLLA‐TMC‐MH decreased from ∼342,000 to ∼8,000 g/mol, compared to ∼24,000 g/mol retained by pure PLLA. Differential scanning calorimetry (DSC) confirmed that TMC disrupted crystallinity to expand amorphous regions, while MH accelerated bulk erosion via water wicking and mitigated local acidification. DSC further revealed a marked increase in crystallinity through 12 months, followed by a substantial decline at 24 months, confirming the biphasic degradation mechanism. Biocompatibility evaluations confirmed noncytotoxicity despite accelerated hydrolysis. These findings demonstrate that TMC and MH coincorporation provides a viable strategy for balancing early mechanical support with timely resorption in next‐generation BVS.