Mechanical Properties, Morphological Characteristics and Microstructural Changes of Poly(glycolide-co-ε-caprolactone-co-l-lactide) Suture during In Vitro Degradation

In this study, as a first step toward the development of novel candidate for absorbable suture materials based on poly(glycolide-co-ɛ-caprolactone), we synthesized a poly(glycolide-co-ɛ-caprolactone-co-l-lactide) block copolymer with ABA block structure via a two-step polymerization process and prepared the final PGCLA suture using a pilot-scale melt spinning machine. Then, to understand the mechanism on the early degradation stage of the PGCLA suture, we systematically investigated the mechanical, morphological properties and microstructural changes of the PGCLA suture through in vitro degradation. As a result, it was observed that, during the in vitro degradation process, the mechanical properties of PGCLA sutures exhibited an overall linear decrease and retained only 32% of its initial strength at 2 weeks of degradation. In addition, it was confirmed that, from FE-SEM analysis, internal degradation and structural changes, including longitudinal cracks on the suture surface, were noticeably appeared at 2 weeks of degradation. Interestingly, the results obtained from ¹H-NMR and WAXS analyses exhibited clearly that PGCLA sutures undergo simultaneous degradation of glycolide units and l-lactide units present in the amorphous region during in vitro degradation. Therefore, based on these findings, we concluded that in the early stage of in vitro degradation of PGCLA suture, simultaneous degradation of glycolide units and l-lactide units in the amorphous region occurs, leading to chemical and structural changes such as erosion and cracking of the suture, as well as a decrease in its mechanical properties.