Design And Performance Of Degradable Metal/Polymer Mixed Vascular Stent With Mechanical Enhanced Characteristics

Lower arteriosclerosis obliterans(LASO)is one of the most common forms of arteriosclerosis,and interventional therapy is the main treatment for lower arteriosclerosis at present.Since the BVS(Absorb)stent was completely stopped,the reliability of degradable vascular stents has attracted widespread attention.The ideal degradable vascular stent should be biodegradable and the radial support force should match the autologous vascular.With the gradual degradation of the stent,the endometrium is uniformly reconstructed,which effectively avoids the complications caused by the long-term retention of the stent in the body.At the same time,the vascular stent should also have axial smoothness to reduce the damage to autologous blood vessels after implantation.Braided vascular stents have good compression rebound and axial smoothness,but braided stents prepared from degradable polymer materials face insufficient radial support,which may lead to stenosis after implantation.Moreover,the vascular stent is prepared from a single polymer material.The centralized degradation of the stent will lead to structural failure and vascular restenosis during the degradation process.In order to solve the problem of insufficient mechanical properties of vascular stents and structural failure during degradation,degradable metal/polymer mixed vascular stents with mechanical enhancement were designed and prepared by adjusting the yarn ratio,braided structure and thermal adhesive fixed interweaving point of braidable vascular stents.Degradable polymer polyp-p-cyclohexanone(PPDO),metal filament zinc and iron were selected as the main materials for mixed vascular stents,and polycaprolactone(PCL)was used to coat metal filament to prepare braided yarns.The melting of PCL in the treatment process of the mixed vascular stents consolidates part of the interleaving points to improve the radial support of the stent.By introducing the third group of shaft yarns that do not participate in the braiding structure,the slippage and rotation of the knitting point are reduced,thus improving the radial support of the mixed vascular stent.In order to explore the effectiveness of these methods on the improvement of radial support,the mixed vascular stents were prepared for the experiments in vitro accelerated.The main research contents are as follows:(1)Degradable polymer PPDO monofilament,degradable metal filament iron and zinc are materials to deeply explore the structure-effect relationship between structure and performance.Two structures to improve the radial support force of degradable metal/polymer mixed vascular stents were designed and prepared.(the third group of shaft yarns,melt/polymer braided yarn).(2)The radial support force of mixed vascular stent FPS is 299.66cN.After the introduction of the melt/polymer braided yarn,the radial support force of the h FPS group is increased to 516.11cN,about 1.73 times.the radial support force of three-way braided vascular stent t FPS is 544.40cN.It is about 1.83 times higher than the FPS group.Mixed vascular stent ZPS radial support force is 297.66 cN,h ZPS stent is 509.43 cN.It is about 1.71 times after the introduction of thermal bonding point.The bending modulus of PS,FPS,t FPS,h FPS,ZPS and h ZPS stents are 22.49cN/mm~2,33.43 cN/mm~2,41.85 cN/mm~2,58.99 cN/mm~2,38.65 cN/mm~2,50.60 cN/mm~2.All stents not only improve the radial support force,but also have good axial flexibility.(3)The accelerated degradation test in vitro shows that the method of introducing melt/polymer braided yarn to improve radial support has better structural stability.After50 days of degradation,h FPS and h ZPS stents were intact and the radial support remained at 38.95cN and 71.43cN.Other groups of vascular stents have failed and disintegrated.In summary,the degradable metal/polymer mixed vascular stent with mechanical reinforcement characteristics has been prepared in this study.The optimized mixed vascular stent has mechanical reinforcement characteristics,maintains a stable structure and shows obvious gradient degradation during the degradation process.It lays a theoretical and experimental foundation for subsequent research on the optimization of mechanical properties of degradable metal/polymer mixed vascular stents.