Characterization and preparation of bioinspired resorbable conduits for vascular reconstruction

Abstract

Soft tissues such as blood vessels possess mechanical behavior characterized by a 'J-shaped' stress-strain curve with a low-stiffness and a highly elastic zone. These biomechanical characteristics result in rapid endothelialization, smooth muscle cell regeneration, and aneurysm inhibition. The objective of this study was to fabricate biodegradable vascular grafts mimicking the mechanical properties of native arteries. Vascular grafts (inner diameter = 5.0 mm, length = 2.0 cm) were fabricated by dip coating poly(L-lactide-co-epsilon-caprolactone) (PLCL) copolymers on polydioxanone (PDO) fibers. We used PDO fibers of different diameters to yield vascular grafts with a range of mechanical properties. Biomechanical properties, microstructure, and biocompatibility of the grafts were assessed using circumferential tensile testing, burst pressure measurement, scanning electron microscopy, and subcutaneous implantation, respectively. Vascular grafts possessed circumferential tensile strength and strain in the range of 4.07 to 5.98 MPa and 2.83 to 3.47 MPa, respectively, and were circumferentially stronger than expanded polytetrafluoroethylene (ePTFE) grafts. Burst pressure was physiologically relevant in the range of 1323.0 to 1736 kPa and water entry pressure was between 102.66 to 257.33 kPa. Mechanical properties of the grafts were also assessed in vivo after subcutaneous implantation in Sprague-Dawley rats for up to 8 weeks. Examination of the retrieved grafts indicated that the 'J-shaped' strain/stress curve was maintained for up to 3 week in PDO/PLCL vascular grafts. In contrast, ePTFE grafts did not maintain 'J-shaped' stress-strain behavior after in vivo implantation. Histological analysis demonstrated cellularization within PDO/PLCL grafts, whereas, PTFE grafts showed cellularization and neotissues mainly at the outer side. Our results suggest a new methodology for the fabrication of biodegradable vascular grafts with mechanical behaviour comparable to the native arteries that might avoid failure due to mechanical mismatch between the graft and native arteries.