Electrospun polyester-urethane scaffold preserves mechanical properties and exhibits strain stiffening during in situ ti
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Electrospun polyester‑urethane scaffold preserves mechanical properties and exhibits strain stiffening during in situ tissue ingrowth and degradation Hugo Krynauw1,2 · Rodaina Omar2 · Josepha Koehne2 · Georges Limbert1,3 · Neil H. Davies2 · Deon Bezuidenhout2 · Thomas Franz1,3 Received: 6 December 2019 / Accepted: 15 April 2020 / Published online: 24 April 2020 © Springer Nature Switzerland AG 2020
Abstract Consistent mechanical performance from implantation through healing and scaffold degradation is highly desired for tissue-regenerative scaffolds, e.g. when used for vascular grafts. The aim of this study was the paired in vivo mechanical assessment of biostable and fast degrading electrospun polyester-urethane scaffolds to isolate the effects of material degradation and tissue formation after implantation. Biostable and degradable polyester-urethane scaffolds with substantial fibre alignment were manufactured by electrospinning. Scaffold samples were implanted paired in subcutaneous position in rats for 7, 14 and 28 days. Morphology, mechanical properties and tissue ingrowth of the scaffolds were assessed before implantation and after retrieval. Tissue ingrowth after 28 days was 83 ± 10% in the biostable scaffold and 77 ± 4% in the degradable scaffold. For the biostable scaffold, the elastic modulus at 12% strain increased significantly between 7 and 14 days and decreased significantly thereafter in fibre but not in cross-fibre direction. The degradable scaffold exhibited a significant increase in the elastic modulus at 12% strain from 7 to 14 days after which it did not decrease but remained at the same magnitude, both in fibre and in cross-fibre direction. Considering that the degradable scaffold loses its material strength predominantly during the first 14 days of hydrolytic degradation (as observed in our previous in vitro study), the consistency of the elastic modulus of the degradable scaffold after 14 days is an indication that the regenerated tissue construct retains its mechanical properties. Keywords Electrospinning · Elastic modulus · Mechanical properties · Soft tissue regeneration · Degradation
1 Introduction Regenerative medicine has emerged as one of the most dynamic drivers in the development of advanced engineered biomaterial solutions for tissue engineering applications [1, 2]. One crucial element in regenerative medicine are scaffolds that facilitate and guide the regeneration of biological tissues according to the biophysical requirements of the specific application.
The ideal conduit for arterial replacement or bypass remains autologous grafts, i.e. the patient’s own artery or vein. Autologous grafts are, however, often unavailable due to either disease or previous use for bypass grafting [3–7]. Whereas currently available vascular prostheses made from polyethylene terephthalate (PET) such as Dacron®, and expanded polytetrafluoroethylene (ePTFE) perform well as large-calibre replacements, their longterm patency is discouraging in small to medium graft
* Thomas Franz, thomas.
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