Evaluation of mechanical properties and biocompatibility of three-layer PCL/PLLA small-diameter vascular graft with pore diameter gradient

A three-layer small-diameter vascular graft (SDVG) of polycaprolactone (PCL) and L-polylactic acid (PLLA) with pore diameter gradient was prepared through combining variable-extrusion speed iterative electrospinning and ultrasonic reaming. The SEM results showed that the three-layer PCL/PLLA SDVG has distinct pore diameter gradient. The Young's modulus, ultimate tensile strength (UTS), burst pressure (BP) and compliance of the vascular graft were high as 20.116 +/- 0.465 MPa, 2.259 +/- 0.141 MPa, 2050 +/- 249 mmHg and 4.203 +/- 0.330 %/100 mmHg, respectively. The UTS of the graft is similar to human coronary arteries. The BP meets the basic requirements to prevent aneurysmal dilation, and the compliance is higher than that of sheep carotid artery. The fluid-solid coupling simulation results showed that the graft had high mechanical properties to withstand the same blood flow velocity as human coronary arteries, and there was no stress concentration in the wall. Besides, it had good biocompatibility, promoting the adhesion and proliferation of rat vascular endothelial cells (ECs). The successful preparation of the small-diameter vascular graft with high mechanical properties for preventing itself from rupturing and ensuring the overall function, provides more possibilities for the clinical transplantation of small-diameter vascular grafts.