Kilian Arthur Maria Mueller (Garching, DE), Andreas Unterrainer (Garching, DE), Diana Marcela Rojas-González (Garching, DE), Marian Willer (Garching, DE), Professor Julia Herzen (Garching, DE), Prof. Dr. Petra Mela (Garching, DE)
Abstract text (incl. figure legends and references)
Introduction Melt electrowriting (MEW) is an electric field-assisted fiber-forming technology for the fabrication of complex scaffold architectures. However, to date MEW scaffolds are mostly macroporous, as fiber-bridging prevents defect-free printing at low interfiber distances. Therefore, MEW scaffolds need to be combined with a second biomaterial to provide a microporosity that is adequate for cellular infiltration following the in situ tissue engineering (TE) paradigm.
Objectives We aim at introducing a design strategy that enables microporous scaffolds by MEW only, while avoiding fiber bridging.
Methods A MATLAB algorithm creates Gcodes for polycaprolactone scaffolds via a MEW through a 23 G needle at 4.5 – 5 kV both on flat and tubular collectors. Samples were assessed via scanning electron microscopy (SEM), microcomputed tomography (µCT), and tensile testing. Ingrowth of human umbilical artery smooth muscle cells (HUASMCs) was verified via SEM and immunohistochemistry at day 3, 7, 14, and 28 after seeding.
Results The design strategy is based on the superposition of angularly shifted fiber arrays with elements of controlled randomization. Modulating interfiber distance and angular shifting resulted in a large range of pore morphologies that were tunable in size and shape. Restricting angular directions of fibers introduced mechanical anisotropy, which was exemplarily tuned to match cardiovascular tissues. In contrast to electrospinning, the design strategy decoupled pore size from fiber diameter, as verified by µCT analysis for scaffolds with fiber diameters ranging from 5.1 ± 0.7 µm to 21.8 ± 1.7 µm, all with 45 µm pores. At day 3, single HUASMCs had bridged the 45 µm pores with progressing infiltration at day 7 and 14. After 28 days, scaffolds were mostly filled with neotissue.
Conclusion This work enables microporous scaffolds by MEW only, which can be customized to meet the architectural and mechanical requirements of the target tissue for in situ TE.