The aim of this study was the in vitro investigation of the change in mechanical properties of a fast-degrading electro-spun polymeric scaffold for the use in soft tissue regenerative implants. Tubular scaffolds were electro-spun from a DegraPol® D30 polyesther-urethane solution (target outer diameter: 5.0 mm; scaffold wall thickness: 0.99 ± 0.18 mm). Scaffold samples were subjected to hydrolytic in vitro degradation for up to 34 days. The fiber network structure and fiber surfaces were inspected on scanning electron micrographs. Following vacuum drying and determination of mass, flat samples (9.69 ± 0.21 × 18.47 ± 2.62 mm, n = 5) underwent uni-axial tensile testing (5 load cycles, strain ε = 0 to 20%; final extension to failure) in circumferential scaffold direction after 5, 10, 14, 18, 22, 26, 30, and 34 days of degradation. Scaffold mass did not change with degradation. Maximum elastic modulus, maximum stress and associated strain were E(max) = 1.14 ± 0.23 MPa, σ(max) = 0.52 ± 0.12 MPa and ε(max) = 176.8 ± 21.9% before degradation and E(max) = 0.43 ± 0.26 MPa, σ(max) = 0.033 ± 0.028 MPa and ε(max) = 24.6 ± 3.0% after 34 days of degradation. The deterioration of mechanical properties was not reflected in the ultrastructural surface morphology of the fibers. The current exploratory study provides a basis for the development of constitutive computational models of biodegradable scaffolds with future extension of the investigation most importantly to capture mechanical effects of regenerating tissue. Future studies will include degradation in biological fluids and assessment of molecular weight for an advanced understanding of the material changes during degradation.

Although coronary and infrainguinal bypass surgery uses saphenous veins as conduits, they undergo significantly different remodeling processes in these two anatomic positions.

Inexpensive, noncommercial bibs are effective and improve tracheal climate and benefit patients with laryngectomies. © 2015 Wiley Periodicals, Inc. Head Neck 38: E480-E487, 2016.

Electro-spun biodegradable polymer fibrous structures exhibit anisotropic mechanical properties dependent on the degree of fibre alignment. Degradation and mechanical anisotropy need to be captured in a constitutive formulation when computational modelling is used in the development and design optimisation of such scaffolds. Biodegradable polyester-urethane scaffolds were electro-spun and underwent uniaxial tensile testing in and transverse to the direction of predominant fibre alignment before and after in vitro degradation of up to 28 days. A microstructurally-based transversely isotropic hyperelastic continuum constitutive formulation was developed and its parameters were identified from the experimental stress-strain data of the scaffolds at various stages of degradation. During scaffold degradation, maximum stress and strain in circumferential direction decreased from 1.02±0.23 MPa to 0.38±0.004 MPa and from 46±11% to 12±2%, respectively. In longitudinal direction, maximum stress and strain decreased from 0.071±0.016 MPa to 0.010±0.007 MPa and from 69±24% to 8±2%, respectively. The constitutive parameters were identified for both directions of the non-degraded and degraded scaffold for strain range varying between 0% and 16% with coefficients of determination r 2 > 0.871. The six-parameter constitutive formulation proved versatile enough to capture the varying non-linear transversely isotropic behaviour of the fibrous scaffold throughout various stages of degradation.

Purpose: The lack of long-term patency of synthetic vascular grafts currently available on the market has directed research towards improving the performance of small diameter grafts. Improved radial compliance matching and tissue ingrowth into the graft scaffold are amongst the main goals for an ideal vascular graft.Methods: Biostable polyurethane scaffolds were manufactured by electrospinning and implanted in subcutaneous and circulatory positions in the rat for 7, 14 and 28 days. Scaffold morphology, tissue ingrowth, and mechanical properties of the scaffolds were assessed before implantation and after retrieval.Results: Tissue ingrowth after 24 days was 96.5 ± 2.3% in the subcutaneous implants and 77.8 ± 5.4% in the circulatory implants. Over the 24 days implantation, the elastic modulus at 12% strain decreased by 59% in direction of the fibre alignment whereas it increased by 1379% transverse to the fibre alignment of the highly aligned scaffold of the subcutaneous implants. The lesser aligned scaffold of the circulatory graft implants exhibited an increase of the elastic modulus at 12% strain by 77% in circumferential direction.Conclusion: The mechanism underlying the softening of the highly aligned scaffold in the predominant fibre direction is thought to be associated with scaffold compaction and local displacement of fibres by the newly formed tissue. The stiffening of the scaffold, observed transverse to highly aligned fibres or for more a random fibre distribution, represents the actual mechanical contribution of the tissue.