Preparation And Performance Evaluations Of PCL/PLLA Pore Gradient Small-diameter Vascular Graft

Vascular tissue engineering is an effective method for the treatment of cardiovascular diseases and vascular defects.Small-diameter vascular grafts(<6mm)are one of the important elements of vascular tissue engineering.Small-diameter vascular grafts can simulate the extracellular matrix well and is one of the excellent methods for preparing biomimetic small blood vessel grafts.However,it is difficult to prepare large pore diameter vascular grafts that can adhere and proliferate cells by electrospinning simply.Small diameter vascular grafts with large pore and suitable mechanical strengths are highlight topics in vascular transplantation.In this paper,we through a series of experiments before,a Variable-rate iterative electrospinning and Ultrasonication reaming were combined to prepare a gradient PLLA/PCL small-diameter vascular graft.Its microstructure,Permeability,mechanical properties were evaluated and compared with natural blood vessels.The main contents of the study are:(1)Using L-polylactic acid(PLLA)and polycaprolactone(PCL)as materials to prepare a series of single-layer small vascular grafts with different flow rates by electrospinning,and a part of single-layer small diameter vascular grafts with different flow rates have been sonicated.Characterize the microscopic morphology of single-layer small vascular grafts with different flow rates and ultrasound conditions.The experimental results show that the flow rates can effectively increase the pore areas and porosities of small-diameter vascular grafts;ultrasonic treatment can effectively increase the pore diameter of small-diameter vascular grafts.According to these,this paper designs a pore diameter gradient small-diameter vascular grafts with trilayers(3LVG).(2)Using the collection device,electrostatic spinning parameters and ultrasonic conditions in(1),we construct a preliminary three-layer gradient structure by variable-rate iterative electrospinning: 1 mL/h of flow rate for the inner layer;2 mL/h of flow rate for the medium layer;3 mL/h of flow rate for the outer layer.and then,the three-layer vascular graft is integral ultrasonicated to prepare a three-layer gradient small-diameter vascular graft(Three-Layer vascular graft,3LVG).Characterize the pore area,fiber diameter,and porosity of each layer of the 3LVG.The results show that the 3LVG has built a clear pore diameter gradient,and the inner,middle and outer layers are all within the range of the pore size of the human small-diameter arterial blood vessels.The contact angle and permeability of the vascular graft are characterized for showing that it has a good permeability.Axial and radial tensile tests,suture retention force,and burst pressure tests are performed on 3LVG.The results show that the axially and radially tensile of 3LVG are similar to that of human coronary arteries.The compliance test results show that the compliance of 3LVG is similar to natural blood vessels under normal human blood pressure.