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Description
Self-assembling scaffolds enable enhanced adaptation to the human body environment thanks to a dynamic response to external stimuli. To produce such scaffolds, advanced biofabrication methods are required. Melt electrowriting (MEW) is a high-precision additive manufacturing technique, which enables the creation of fine fibers of molten polymer under the influence of an electrical field. Dual-head MEW approach allows deposition of diverse materials in one printing process, which in turn can increase the complexity of fabricated structures and broaden the applications. In this research, we employ this approach to produce multimaterial self-assembling scaffolds for application in vascular tissue engineering.
Square and triangular structures, with a fiber-to-fiber distance of 300 μm, were designed using FullControl GCode Designer software. The scaffolds consisted of two parts with different swelling properties, where the fiber orientation and layer thickness varied. Polycaprolactone (PCL) or poly(ethylene oxide terephthalate)/poly(butylene terephthalate) with molecular weight of the poly(ethylene oxide) equal to 300 (PEOT-PBT 300) were used as more hydrophobic layer, while PEOT-PBT 1000 was used as more hydrophilic layer. The scaffolds were printed using a dual-head MEW tool (BioScaffolder 3.3, GeSiM). The optimization of fabrication parameters, including material temperature, printing speed, pressure, and voltage, was performed. The printed scaffolds were processed with oven treatment to enhance the connections between fibers. The time and temperature of the process were optimized. The microstructure of scaffolds was characterized by optical and scanning electron microscopy (SEM). The self-assembling properties were investigated by observing the rolling behavior after placing the scaffolds in phosphate-buffered saline (PBS). The tensile strength of dry and wet scaffolds was measured. To assess cell adhesion and distribution inside the tubular scaffolds, preliminary cell study with tenocytes was performed.
The difference in swelling properties between the printed materials enabled self-assembly of the construct. The self-rolling behavior of the obtained scaffold depended on the material combination, the orientation of hydrophobic fibers, as well as on the way of placing scaffolds in PBS. Oven treatment post-processing was crucial to obtain self-rolled scaffolds based on combination of PEOT-PBT 300 and PEOT-PBT 1000. The scaffolds formed tubes with lumen inside. The diameter of the tube, as well as the lumen size, were easily controlled via adjusting number of layers and scaffold dimensions. In the following studies different shapes of tubes were obtained, including gradient (diagonal, spiral) and branched structures. Preliminary test with seeded tenocytes proved scaffolds biocompatibility, however cell studies with endothelial cells will be further investigated.
The conducted research shows successful integration of two different materials into one MEW process. The self-assembling scaffolds is one of the numerous examples how this approach can enhance biofabrication possibilities. The fabricated self-rolling scaffolds are promising solution for vascular tissue engineering applications.
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