Surface Porosity\nand Core Interconnectivity in Small\nDiameter PCL/PLA Vascular Scaffolds Prepared by Ultrasonic Irradiation\nEnhanced Foaming

Highly interconnected porous structure and bionic mechanical\nperformance\nare important challenges to the successful fabrication of small-diameter\nvascular scaffolds. This article describes an effective approach to\nprepare the outer and inner tubular porous poly(ε-caprolactone)\n(PCL)/polylactic acid (PLA) scaffolds by ultrasonic irradiation (UI)-assisted\nsupercritical CO<sub>2</sub> (scCO<sub>2</sub>) microcellular foaming\ntechnology. The pore structures, mechanical properties, and cytocompatibility\nare investigated with respect to the introduction of UI at various\nfoaming moments. As expected, a tubular porous scaffold with an inner\ndiameter of 4 mm, a nonuniform pore gradient distribution in the core,\nand a smooth surface is fabricated based on a 280 μm foaming\ngap. By introducing UI at the end of the saturation process, the resultant\nfoams exhibit a significant increase in surface porosity: pore density\nincreases near 2 orders of magnitude, compared to samples without\nUI. A denser inner pore structure is obtained, and the corresponding\nopen-pore content increases from 68% to 78%. The Pre-UI scaffolds\npossess radial tension strength of 2.5 MPa, longitudinal tension strength\nof 3 MPa, sufficient tensile elastic, high compressive recovery performance,\nand burst pressure of 250 kPa to maintain human blood flow. Furthermore,\nsuture strength of 2.5 N for Pre-UI scaffolds exceeds the strength\nof some human veins, which fulfill transplantation requirements. Human\nendothelial cell culture and proliferation tests for Pre-UI scaffolds\nreveal good biocompatibility and high capacity for intramural to extramural\ncell growth. The results gathered in this study may provide a theoretical\nbasis and data to support research into small-diameter vascular tissue\nengineering of porous scaffolds.