F 4 . 3 Bioprinting of encapsulated pancreatic islets

Aim: We optimized the process parameters of Melt Electrospinning Writing (MEW) to produce highly ordered structures composed of sub-micron filaments for Tissue Engineering (TE) purposes. [1] Methods: MEW has recently been introduced as a novel electrohydrodynamically assisted additive manufacturing (AM) process that allows a controlled deposition of electrically non-conductive fibers of particular biocompatible and biodegradable thermoplastic polymers [2 3]. To direct write thin and homogeneous filaments from poly(epsilon-caprolactone) (PCL) with our custom-made device we investigated and adjusted the process parameters including: spinning temperature ≤ 120 °C feeding pressure ≤ 4 bar nozzle diameter ≤ 22 G acceleration voltage ≤ 7 kV and nozzle/collector distance ≤ 7 mm. During processing a grounded collector plate was moved in planar directions under the nozzle by a computer-aided system in order to collect straight filaments. [1 3] Results: While PCL is often used for AM in TE direct writing molten filaments with sub-micron dimensions has not yet been demonstrated. We found that MEW could break through this micron diameter barrier and allow the deposition of accurately stacked sub-micron filaments (817 ± 165 nm) to highly regular structures (100.6 ± 5.1 μm). Thus PCL fibers can be deposited with a diameter range of 800 nm to 40 μm. This adjustment of the specific surface allows a tailoring of the degradation time in combination with a highly porous and well defined structure which provides cell migration into the scaffold. First experiments for cell adhesion have been conducted and initial data will be included in the presentation. [1] Conclusion: While other 3D printing methods such as fused deposition modeling allow a fabrication of fibers in a range of 100 μm microns and more MEW can be used to print even sub-micron filaments. In contrast to solution electrospinning drawing fibers from melts enables the processing more amenable to direct writing and stacking without often toxic solvents for TE approaches.