Polyurethane Vascular Grafts with Thorough Porosity: Does an Internal or an External Membrane Wrapping Improve their In Vivo Blood Compatibility and Biofunctionality?

Abstract

Using a freeze-drying multiple-step technique, porous polyurethane vascular grafts 1.5 mm in diameter with different internal and external surface characteristics were fabricated: Type A: with thorough porosity, Type B: with internal membrane wrapping and Type C: with external membrane wrapping. One centimeter long tubes of each three types of grafts were implanted into the infra-renal abdominal aorta of rats for periods of 2, 4, 8 weeks. All the grafts were patent at harvesting. At the end of 2 weeks postimplantation, the endothelial cells layer developed inside the grafts about 1.2 mm apart from either the distal anastomosis side or both the distal and proximal anastomoses. They spreaded to the middle part of the one cm-long graft at 4 weeks. The luminal surfaces were entirely covered by a layer of endothelial cells at 8 weeks. Smooth muscle cells also migrated underneath the endothelial cell layer through the inner surface from the anastomosis and grew into the porous wall to generate a biocomposite blood conduit. Type B grafts with an internal membrane wrapping, developed a thicker, easy to lift intima after all the durations of implantation because the internal capsule was poorly anchored to the device. It is therefore of paramount importance that a porous structure is exposed to the blood flow to permit an adequate healing together with a good anchorage of the internal capsule.

Interactions of coronary artery smooth muscle cells with 3D porous polyurethane scaffolds

“…The need for high porosity and pore interconnectivity for in vivo tissue engineering is even greater to facilitate graft healing by recruiting vascular cells from the anastomosis or transmural tissue thus providing tis- sue in-growth area. 31,32 For vascular tissue engineering, the optimum scaffold porosity required is from 80-90% with pore sizes ranging from 150 to 300 lm. 13,21 In the current study, porous and interconnected scaffolds were fabricated by tightly packing the porogen using a pressure differential.…”

Precision control of polyurethane filament drafting and winding based on machine vision

“…Figure 3 showed the preparation process, visual inspection, and target quantity to be controlled of the whole tube. The motion of the drafting mechanism was an important parameter that affected the diameter of PU filament (Wang Z. X et al, 2004;Zhao, 2019), while the motion parameters of the motion platform mainly affect the winding quality. The filament diameter and winding angle could be controlled only by controlling the speed of the drafting roller and the moving speed of the moving platform, to ensure the Frontiers in Bioengineering and Biotechnology frontiersin.org overall quality of the tube prepared.…”