Exploring morphological effects on bulk material properties of co-extruded nanofiber blends
Date
2021
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Nanofibers and hydrogels have demonstrated promising capabilities as tissue engineered scaffolds and matching the properties of biological tissues is essential to designing a successful scaffold. Besides biocompatibility, mechanical properties and degradation rate have been highlighted as the primary features to address during fabrication. In an effort to meet the needs of a variety of biological tissues, a high through-put melt-based fabrication process, multilayer coextrusion, was utilized to manufacture biocompatible composite tapes. The fibrous component of the composites was formed by exploring different blended compositions of poly(lactic acid) (PLA)/poly(ɛ-caprolactone) (PCL), and the matrix was a poly(ethylene oxide) PEO blend. ☐ In the initial investigations described in this dissertation, fibers were isolated from the matrix, and the morphological effects on mechanical properties were investigated as a function of blend composition. Both components of the blend experienced a depression in the amount of crystallinity. However, the average size of the PLA crystallites increased as the PCL component increased. This indicated that PCL served as a nucleation site for PLA. Additionally, this heterogeneous nucleation led to fractionated crystallization occurring in the PLA component in select blends. The changes in the crystalline domain and the spatial confinement caused by the phase separated morphologies lead to a decrease in strength compared to the unblended fibers. ☐ The blending process also manipulates the degradation rate of PLA and PCL. Both the composition of the blend as well as the morphology of the blended fibers were found to play a significant role in the degradation profile during an in vitro degradation study. While PLA undergoes hydrolytic degradation much more rapidly than PCL, the degradation rates of extruded PCL/PLA fibers heavily influenced by the size of the crystalline regions. The rate of erosion of the crystalline phase was also correlated to the change in the mechanical properties of the fibers throughout the investigation. ☐ Finally, fibers can be utilized to reinforce hydrogel systems, which are typically considered a weak material. A straightforward process for the fabrication of PCL/PLA fiber-reinforced hydrogel systems from extruded composite tapes was utilized. The bulk mechanical properties of the blended fiber-reinforced systems were found to be dependent upon the fiber composition; as the PLA content increased, higher mechanical properties were achieved. Additionally, these biocompatible fiber-reinforced hydrogels were explored for tissue engineering applications in terms of mechanosensitivity. Healthy fibroblast cells were found to cultivate on the surface of the PCL/PLA fiber-reinforced hydrogels. The higher PLA blended fibers encouraged more rapid adhesion in the reinforced hydrogels.
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Keywords
Melt-based fabrication process, Degradation rates, Hydrogel systems