Degradation‐induced changes of mechanical properties of an electro‐spun polyester‐urethane scaffold for soft tissue regeneration

Abstract

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.

The anisotropic mechanical behaviour of electro-spun biodegradable polymer scaffolds: Experimental characterisation and constitutive formulation

“…Consistent with earlier results (Krynauw et al, 2011), fibre fracture and pitting were not apparent during degradation period of up to 28 days. The SEM images showed an increase in the surface roughness of the fibres during degradation.…”

“…The goodness of fit between the theoretical and experimental stress is assessed using the correlation coefficient. In an earlier study it was found that degradation did not affect electrospun fibre orientation (Krynauw et al, 2011). Consequently, the parameter ߩ controlling the degree of anisotropy which was determined for the non-degraded sample was fixed (ߩ = 1.27013) for the other identification procedures (time = 4 to 28 days).…”

“…In the first stage, constitutive parameters for the non-degraded scaffold material (T = 0 day) were determined. The anisotropy coefficient ߩ was subsequently kept constant for the identification at different degradation times based on the observation that anisotropy of electro-spun fibre scaffolds is not affected by waterinduced degradation (Krynauw et al, 2011).…”

“…The degradation of the scaffold material introduces a transient process that affects the structural properties of the scaffold (Dargaville et al, 2013;Krynauw et al, 2011) and consequently engineering tissue (Roh et al, 2008). It is important to ensure that the degradation of the scaffold does not lead to premature failure of the tissue construct e.g.…”

Ureter Regeneration–The Proper Scaffold Has to Be Defined

“…Polyesters are created de novo , no animal material has to be used to synthesize them. They can be combined with other compounds and it is possible to control their shape, size, porosity, cell attachment, or biodegradability [19]–[21]. Disadvantages are possibility of inflammation inducted by a too long degradation time for PLCL [22], [23].…”