Bioinspired Strain-Induced Crystallization and Orientation in Ultrathin Polycaprolactone Fibers: Enhanced Strength and Toughness for Surgical Sutures.

Fine fibers constitute significant applications in advanced materials engineering. However, the development of absorbable ultrathin fibers as sutures (<0.05 mm diameter, USP 10-0 gauge) has been hindered by the inherent limitations of biodegradable polymers, particularly their insufficient mechanical strength and thromboresistance. To overcome these challenges, we developed a novel heparin-conjugated polycaprolactone-based ultrathin fiber through a bioinspired two-step stretching process employed by spiders. This approach enabled a diameter adjustment while inducing strain-induced crystallization and molecular orientation, resulting in exceptional mechanical properties, tensile strength of 916.89 ± 81.24 MPa and toughness reaching 203.97 ± 22.17 MJ/m, all exceeding biodegradable ultrathin surgical suture requirements, and concurrently provided outstanding thromboresistance without compromising biocompatibility or biodegradability. This study advances absorbable ultrathin suture technology at the polymer physics-biomaterials interface, which demonstrates its significant potential for cardiovascular microsurgery and other delicate reconstructive procedures.