PCL-b-PLLA diblock copolymers with high performance to replace polyoxymethylene for tissue ligation clips

Current biodegradable polymers for absorbable tissue ligation clips suffer from not possessing rigidity and toughness simultaneously compared with polyoxymethylene (POM) clips. To overcome the limitations, two series of biodegradable copolymers of poly(ε-caprolactone) and poly(L-lactide) with random and block architectures were designed and synthesized. Compared with random copolymer P(CL-r-LLA), diblock copolymer PCL-b-PLLA exhibited higher crystallinity and superior mechanical strength. The copolymers with 15 mol% CL composition were selected for further study, denoted as RP15 (random) and BP15 (block). The BP15 clips achieved a closure force of 27.9 ± 1.4 N, comparable to commercial POM clips (29.0 ± 2.4 N), while also offering biodegradability. The degradation studies showed that BP15 clips degraded slowly, maintaining structural integrity and sustained closure functionality for up to two weeks, which was essential for safe tissue ligation. Subcutaneous implantation in rats further confirmed that BP15 clips exhibited favorable performances, demonstrating their potential as a promising biodegradable alternative to POM for use as an absorbable tissue ligation clip.