Degradation-induced changes of mechanical properties of an electro-spun polyester-urethane scaffold for soft tissue...

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.