Fabrication and Degradation of Electrospun Scaffolds from L-Tyrosine Based Polyurethane Blends for Tissue Engineering Applications

Tissue engineering scaffolds (or matrices) with a controllable degradation profile were fabricated from multiple blends of two L-tyrosine polyurethanes (denoted as PCL₁₂₅₀-HDI-DTH and PEG₁₀₀₀-HDI-DTH ) by means of the electrospinning process. By adjusting the ratios (2:1, 1:1, 1:2, and pure solutions) of the two polymers in the blends, relative control over the scaffolds' degradation properties was achieved without detriment to other scaffold properties. The ability to control the degradation rate allows for scaffold residence time to be design variable when fabricating a medical device intended on mimicking the body. The matrices produced were characterized chemically, morphologically, and mechanically and then subjected to hydrolytic degradation.

As theorized, the scaffolds degraded in a predictable and controllable manner. The scaffolds containing the higher proportion of the more resilient PCL₁₂₅₀-HDI-DTH polymer degraded more slowly and to a lesser extent (by mass) than those principally composed of the more hydrophilic PEG₁₀₀₀-HDI-DTH polymer. Specifically, after 60 days of exposure, mass losses (from highest to lowest concentration of PEG₁₀₀₀-HDI-DTH) were approximately 35%, 26%, 21%, 16%, and 9%. Note that decreasing concentration of PEG₁₀₀₀-HDI-DTH correlates to increased resistance to hydrolytic degradation. The mass lost per electrospun scaffold was between 76% and 108% greater than the identical blend in thin film configuration, demonstrating the enhanced degradation characteristics of the structure. Specifically, after 35 days of exposure, mass losses from the electrospun membranes were (from highest to lowest concentration of PEG₁₀₀₀-HDI-DTH) approximately 76%, 85%, 108%, 103%, and 98% greater than those of each blend’s thin film counterpart.

Morphologically, despite differing polymeric compositions, the scaffolds were fabricated under almost identical conditions and produced similar, acceptable fiber diameters, distributions, and pore sizes with minor variation across the blends. Specifically, the average fiber diameters in order of highest to lowest concentration of PEG₁₀₀₀-HDI-DTH were approximately 4.9 µm, 10.4 µm, 8.2 µm, 9.7 µm, and 9.8µm. The morphological and mechanical properties, pore sizes between 5 and 10 µm and Young’s moduli localized around ~12 MPa, combined with a controllable degradation profile, would suggest that the scaffolds produced would serve as a suitable mimic for soft tissue engineering.