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Expanding the Melt-Electro Fibrillation Polymer Library for Advanced Biofabrication Applications
Tamaki Kumauchi1, Kristina Andelovic1 and Jürgen Groll1
1Department of Functional Materials in Medicine and Dentistry, Institute of Functional Materials and Biofabrication (IFB), and Bavarian Polymer Institute (BPI), University of Würzburg, 97070 Würzburg, Germany
Introduction: Melt-Electro Fibrillation (MEF) is an emerging technology derived from Melt Electrowriting (MEW), in which a polymer melt is accelerated by an electric field to achieve a precise micrometer fiber deposition. When two immiscible polymers are co-processed and one selectively removed, highly anisotropic nanofibrillar structures remained1. This collagen-mimetic, topographical guidance can then promote / facilitate the anisotropic distribution and alignment of cells, with the potential to mimic native tissue architectures such as tendon or muscle. However, since each tissue exhibits distinct mechanical properties, such as stiffness or elasticity, as well as different biological requirements, there is a growing need to explore a broader range of polymer combinations to tailor scaffold characteristics for the specific applications. Herein we introduce polymers outside of the original MEF framework and attempt to expand the MEF applicable polymers.
Methods: The polymers were selected based on their melt immiscibility and processing characteristics. In MEF, Poly-ε-Caprolactone (PCL) is blended with Polyvinyl acetate (PVAc) and heated past their melting points. When the PVAc is selectively dissolved via ethanol treatment, the resultant PCL remains. Polyethylene glycol (PEG) was then evaluated as the matrix material, showing capability of the PEG to replace PVAc in select situations. Polypropylene (PP) was also attempted as the fibrillating polymer, as its inert properties has seen its use in the medical industry. PP has low to no miscibility in PVAc or PEG and is possible to MEF. Additionally, polylactic acid (PLA) was also tested for its fibrillation potential. To verify the prints, fibril diameters and morphology were quantified, as well as the initial printing conditions.
Results: This study successfully demonstrates various new polymer combinations outside of the traditional MEF scope and explores potential applications. Furthermore, we measured the parameters that are vital in successful fibrillation of polymers such as their melting points and viscosities at the printing temperatures. While inert materials like PP were immiscible with all tested matrix polymers, other materials like PLA or PCL demonstrated sufficient compatibility to allow an effective fibrillation. The fibrils formed exhibit dimensions on a cellular scale, suggesting strong potential for guiding cellular alignment and the formation of defined, highly anisotropic scaffolds in tissue-specific constructs.
Discussion: Herein we were able to expand the MEF-compatible library and demonstrate the feasibility of generating nanofibrillar scaffolds with both biologically active or inert polymers, The morphological similarities with the traditional PCL/PVAc blend support the versatility of MEF in biomedical applications such as tendon or muscle regeneration.
References: [1] Ryma, M.; Tylek, T.; Liebscher, J.; Blum, C.; Fernandez, R.; Böhm, C.; Kastenmüller, W.; Gasteiger, G.; Groll, J. Translation of collagen ultrastructure to biomaterial fabrication for Material‐Independent but highly efficient topographic immunomodulation. Advanced Materials 2021, 33 (33).
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