Coconut Oil as Lipid-Based 3D-Printable Sacrificial Material for the Facile Biofabrication of Precise Perfusable Microchannels and Freeform Hydrogel Structures.

Sacrificial materials provide temporary support in the biofabrication of 3D hydrogel constructs featuring cavities and overhangs or having slow polymerization preventing printability. Currently used sacrificial hydrogel inks take up water from the surrounding matrix hindering the shape fidelity of the final construct, for example microchannels with a flattened/irregular cross-section. Furthermore, some inks require removal by chemical dissolution or mechanical forces with potential cytotoxic effects and damage of the main construct. Here, we propose lipid-based sacrificial materials to address these limitations and introduce coconut oil as proof-of-concept hydrophobic, temperature-responsive, cytocompatible, and printable sacrificial material that enables a cell-friendly removal process. We demonstrate its suitability in the fabrication of microchannels with circular cross-section and dimensional accuracy, which support functional endothelial layer formation, as demonstrated with dextran diffusion. Furthermore, we show the versatility of coconut oil by applying it as support material for the additive manufacturing of 3D macroscale hydrogel structures with overhangs and bridging elements as well as support bath for the fabrication of complex vascular structures in freeform embedded printing. The applicability with various hydrogels with different gelation mechanisms and the ease of use and the large availability at a low cost make the lipid-based ink a promising material in biofabrication.