a b s t r a c tA degradation study investigating the hydrolysis of different scaffolds of polycaprolactone suspended in phosphate buffer solution at 37 C was performed over a three month period. Structures included electrospun fibres, held as 2D mats and 3D bundles, and solvent cast films. These structures and their surrounding solutions were physiochemically characterised using a range of techniques. Changes in scaffold physicochemical properties were observed over the course of the study, including significant loss in molecular mass, increases in thermal properties and crystallinity, and increases in tensile properties. The presence of degradation products, such as capronic acid containing compounds was also identified in the surrounding solution. 3D electrospun bundles -as a consequence of being the least crystalline scaffold and hence most susceptible to hydrolysis e demonstrated greatest reduction in molecular mass over the three months, followed by 2D electrospun mats, and the lowest mass loss was observed for solvent cast films.

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Two-dimensional (2D) electrospun fibre mats have been investigated as fibrous sheets intended as biomaterials scaffolds for tissue repair. It is recognised that tissues are three-dimensional (3D) structures and that optimisation of the fabrication process should include both 2D and 3D scaffolds. Understanding the relative merits of the architecture of 2D and 3D scaffolds for tendon repair is required. This study investigated three different electrospun scaffolds based on poly(ε-caprolactone) fibres intended for repair of injured tendons, referred to as; 2D random sheet, 2D aligned sheet and 3D bundles. 2D aligned fibres and 3D bundles mimicked the parallel arrangement of collagen fibres in natural tendon and 3D bundles further replicated the tertiary layer of a tendon's hierarchical configuration. 3D bundles demonstrated greatest tensile properties, being significantly stronger and stiffer than 2D aligned and 2D random fibres. All scaffolds supported adhesion and proliferation of tendon fibroblasts. Furthermore, 2D aligned sheets and 3D bundles allowed guidance of the cells into a parallel, longitudinal arrangement, which is similar to tendon cells in the native tissue. With their superior physical properties and ability to better replicate tendon tissue, the 3D electrospun scaffolds warrant greater investigation as synthetic grafts in tendon repair.

Fabrication of electrospun fibrous scaffolds as future medical devices is being widely researched, with particular emphasis given to their material properties and effect on cell response and differentiation. However, the vast majority of these scaffolds are sterilized via nonmedically approved methods, including submersion in ethanol and exposure to UV light. Although these techniques are adequate for laboratory-based research, they are not sufficient for human implantation. In this case, regulatory approved, medical grade sterilization is required. In this study, we report the effects of gamma irradiation, a regulatory approved technique, on electrospun poly(ecaprolactone) fibers. Fabricated fibers were separately subjected to different dosages of irradiation ranging from 0 to 45 kGy and then assessed for their physicochemical properties. Gamma irradiation affected fiber properties irrespective of dosage. A dose-dependent decrease in polymer molecular weight was observed and an increase in melting point and crystallinity reported. Similarly, irradiation had a significant effect on mechanical properties with greatest decrease in tensile strength (68%) for fibers exposed to 40 kGy. The method of sterilization had no effect on cell response. Seeded tenocytes attached to all fibers and elongated parallel to the underlying fiber direction. The results demonstrate the importance of incorporating medical grade sterilization procedures early in the research projects time line to assist translation from bench to clinic.

Alternative strategies are required when autograft tissue is not sufficient or available to reconstruct damaged tendons. Electrospun fibre yarns could provide such an alternative. This study investigates the seeding of human mesenchymal stem cells (hMSC) on electrospun yarns and their response when subjected to dynamic tensile loading. Cell seeded yarns sustained 3600 cycles per day for 21 days. Loaded yarns demonstrated a thickened cell layer around the scaffold׳s exterior compared to statically cultured yarns, which would suggest an increased rate of cell proliferation and/or matrix deposition, whilst maintaining a predominant uniaxial cell orientation. Tensile properties of cell-seeded yarns increased with time compared to acellular yarns. Loaded scaffolds demonstrated an up-regulation in several key tendon genes, including collagen Type I. This study demonstrates the support of hMSCs on electrospun yarns and their differentiation towards a tendon lineage when mechanically stimulated.