Crimped elastomer scaffolds prepared through MEW with non-linear extension behaviour mimicking that of ligaments and tendons

Publication date: Available online 17 March 2018
Source:Acta Biomaterialia
Author(s): Gernot Hochleitner, Fei Chen, Carina Blum, Paul D. Dalton, Brian Amsden, Jürgen Groll
Ligaments and tendons are comprised of aligned, crimped collagen fibrils that provide tissue-specific mechanical properties with non-linear extension behaviour, exhibiting low stress at initial strain (toe region behaviour). To approximate this behaviour, we report fibrous scaffolds with sinusoidal patterns by melt electrowriting (MEW) below the critical translation speed (CTS) by exploitation of the natural flow behaviour of the polymer melt. More specifically, we synthesised photopolymerizable poly(L-lactide-co-ε-caprolactone-co-acryloyl carbonate) (p(LLA-co-ε-CL-co-AC)) and poly(ε-caprolactone-co-acryloyl carbonate) (p(ε-CL-co-AC)) by ring-opening polymerization (ROP). Single fibre (fØ=26.8±1.9µm) tensile testing revealed a customisable toe region with Young's Moduli ranging from E=29±17MPa for the most crimped structures to E=314±157MPa for straight fibres. This toe region extended to scaffolds containing multiple fibres, while the sinusoidal pattern could be influenced by printing speed. The synthesized polymers were cytocompatible and exhibited a tensile strength of σ=26±7MPa after 10⁴ cycles of preloading at 10% strain while retaining the distinct toe region commonly observed in native ligaments and tendon tissue.Statement of SignificanceDamaged tendons and ligaments are serious and frequently occurring injuries worldwide. Recent therapies, including autologous grafts, still have severe disadvantages leading to a demand for synthetic alternatives. Materials envisioned to induce tendon and ligament regeneration should be degradable, cytocompatible and mimic the ultrastructural and mechanical properties of the native tissue. Specifically, we utilised photo-cross-linkable polymers for additive manufacturing (AM) with Melt Electrowriting (MEW). In this way, we were able to direct-write cytocompatible fibres of a few micrometres thickness into crimp-structured elastomer scaffolds that mimic the non-linear biomechanical behaviour of tendon and ligament tissue.

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