Preparation Of Small Diameter Vascular Grafts And Their Properties In Vitro Biomimetic Environment

Nowadays,the comprehensive mechanical properties of small diameter vascular graft has not yet reached the standard of natural vascular.Its compliance is not matched with natural vessels in the medium and long term transplant process.That could cause thrombosis and intimal hyperplasia and futher lead to failure of transplantation.Therefore,it is important to prepare a small diameter vascular graft which comprehensive mechanical properties could match with the natural vascular and as well as long-term compliance after implantation.On the other hand,so as to avoid its failure to transplant in vivo,the mechanical properties changes of small diameter vascular grafts in a period of time should be evaluated in simulated biological environment before they are implanted into the body.Therefore,it is necessary to construct an environment that can simulate the mechanical and physiological conditions of the body in order to study the long-term performance of small diameter vascular graft.In this study,we contructed a biomimetic environment device(BED)which can simulate body temperature,liquid environment out of the vessel and the pulsatile pressure induced by continuous blood flow,to be used as "pre-test" of animal experiment to explore the change of long-term mechanical properties of small diameter vascular graft.We also prepared poly(L-lactic acid)caprolactone(PLCL)/ silk fibroin(SF)bilayer small diameter vascular graft with different proportions,and its radial tensile properties,suture retention strength and compliance were studied.In order to further improve its comprehensive mechanical properties,we used a braided tube as its enhanced layer.At the same time,the changes of tensile properties,compliance and degradation behavior of small diameter vascular graft in a period of time in the BED were also studied.The results showed that the comprehensive mechanical properties(tensile strength,suture retention strength and compliance)of three different proportions bilayer small diameter vascular graft were comparable with natural vessels.The radial tensile strength and suture retention strength of the braided tube reinforced-bilayer small diameter vascular graft were greatly improved.After the in vitro test,its mechanical properties have changed in different degrees,and there is no obvious degradation behavior in the short term.To sum up,the bilayer small diameter vascular graft made by electrospinning method with PLCL and SF has excellent comprehensive mechanical properties,and its mechanical properties are significantly improved by silk braid tube.In addition,the BED can make long-term testing in vitro for small diameter vascular graft.In a period of time in BED,the mechanical properties of PLCL/SF bilayer small diameter vascular graft has changed,but its degradation behavior is not obvious.This research has great significance for improving the evaluation system and method for long-term mechanical performance of small diameter vascular graft,especially for compliance and speeding up the development and application of small diameter vascular graft with independent intellectual property rights in China.