Preparation And Properties Study On External Vascular Stent Of Venous Graft

Nowadays,the incidence rate of vascular disease is increasingly high.The autogenous vein is widely used as a conduit in grafting surgical operation,however, restenosis resulted from the reconstruction of the autogenous vein effects the patency rate seriously.Lots of research has indicated that the external vascular stent can relieve the intimal hyperplasia of vein from grafting,avoid atherosclerosis,and improve the patency rate.To this day,the research of external vascular stent is focused on the braiding stent which is made by metal filament at home and abroad. But the metal as a foreign body will be harmful to vessel if it stays in the body permanently.In addition,it is not good for the suturing,for the braiding stent is easy to ravel.Hence,it is urgent to develop a novel external vascular with new material and structure.In this paper,polydioxanone has been used as raw material,and the external vascular stents have been made on the circular warp knitted machine.Then we test their tension property,compression property,torsion property,porosity and raveling property.Weft stents and braiding stents have been made of the same material,and their properties have been tested as well.These stents of three different structures have been compared in order to decide which one is the best.Then,the stents of best structure have been heat-set,and their compression property has been tested by orthogonal test method to select the best parameters.Finally,the stents have been coated,and the compression test has been made to find the best concentration of coating solution.The degradation experiment in vitro has been made to see the appearance change,mass loss and compression property of the stents in different periods.After these experiments,the results showed that warp knitted structure is the most suitable structure to meet the requirements of the external vascular stent.And the best preparation process is to adopt PDS single filament of diameter 0.20mm as raw material,use the cylinder with 10 needles to make cord stitch samples on circular warp knitted machine,then put the sample into oven for ten minutes to heat-set,and coat the sample with 3.5%chitosan solution,and at last dry it in natural environment.The results of the degradation tests showed that the stents made of PDS can keep good compression recovery,maintain compression force and quantity in a relative long period,but mass loss and compression force changed obviously when coating went degrading.Comparing the degradation of weft knitted stent with that of warp knitted one,we find that there is almost no effect on degradation property with the change of the stent structure.In a word,warp knitted stents which are made of PDS single filament can meet the requirements of the external vascular stents,and the further research of animal test and clinical study can be taken.