Mixed-braided stent: An effective way to improve comprehensive mechanical properties of poly (L-lactic acid) self-expandable braided stent.

For its unique flexibility, self-expandable braided stent has been wildly used in the treatment of peripheral vascular diseases, such as the superficial femoral artery stenosis. With the application of bioabsorbable polymer materials, stent braided by polymer filaments is explored, and expected to minimize the complications caused by long-term retention of commercial metallic stents in the human body. Poly (L-lactic acid) (PLLA) is the representative of degradable polymer materials, and has been broadly applied in stent for its good mechanical properties and biocompatibility. This study aimed to propose a new preparation method for PLLA self-expandable braided stent by mixed-braided technology, and evaluate its mechanical properties especially in radial supporting performance and flexibility. For this purpose, a series of stent samples were prepared by mixed braiding PLLA monofilament with different diameters. In addition, the pitch angle and monofilament diameter are also considered as two critical design parameters affecting stent mechanical performance. Then, the radial strength and flexibility of different samples were evaluated respectively. The results show that the mixed-braided stent keep the excellent flexibility of thin monofilament braided stent, meanwhile it possesses the good radial supporting performance of the thick monofilament braided stent. This paper provides an idea to improve the comprehensive mechanical properties of PLLA self-expandable braided stent.