Additive manufacturing of fibrous sub-micron poly(ε-caprolactone) scaffolds for tissue engineering

摘要

Introduction: The field of additive manufacturing (AM) has attracted increasing interest over the last decade, in part for tissue engineering (TE) approaches. In our study we use an emerging type of AM technology, termed Melt Electrospinning Writing (MEW), a process that combines the characteristic benefits of 3D printing and electrospinning. When using an electrohydrodynamic drawing process, thermoplastic melts can be deposited to well defined scaffold structures, even with sub-micron sized fiber diameters (817 ± 165 nm) as we recently observed. Materials and Methods: A custom-built device was used to manufacture scaffolds made of poly(ε-caprolactone) (PCL), a biodegradable polymer with a history of clinical use. In order to investigate the influence of the instrumental parameters, the feeding pressure (0.5-4.0 bar), heating temperature (80-120°C), acceleration voltage (2.0-10.0 kV), spinneret diameter (21 G; 23 G; 25 G; 27 G; 30 G; 33 G), collector distance (1-10 mm) and collector speed (1000-9000 mmmin~(-1)) was systematically varied and optimized. To confirm cell adhesion to the scaffolds, we printed scaffolds directly onto hydrophilized (NCO-sP(EO-stat-PO)coated) glass slides and seeded primary human mesenchymal stromal cells (hMSC) to them afterwards. Results and Discussion: Through the adjustment of instrumental parameters, PCL fibers with diameters ranging from 50 μm to the sub-micron level (817 ± 165 nm) can be deposited to highly uniform scaffolds (figure 1 A, B, C). Thus, MEW can be used to tailor scaffold architecture and to define its specific surface, which is of high interest for degradation or cell-interaction processes. Figure 1: A, B & C: MEW PCL scaffolds with a box structure consisting of 2×50 layers of sub-micron fliaments. D: HMSCs adhered to a scaffold after 4 days in vitro. We observed excellent scaffold adhesion to the microscope slide that could withstand media changes and up to 2 weeks in vitro. The MSCs adhered well on the scaffolds, forming circular structures, even when the box spacing is only 90um (figure 1 D). Further, the hydrophilic coatings of the glass slides not only prevented cell adhesion to the underlying surface, so that specific scaffold cell interactions could be observed. Conclusion: While common AM methods, such as fused deposition modeling, allow a fabrication of fibers in a range of 100 μm microns and more, MEW can print sub-micron fibers with medical grade polymers. In contrast to solution electrospinning, drawing fibers from melts enables manufacturing without the use of often toxic solvents highly interesting for TE or medical approaches.