To get around this problem, Penn researchers turned the printing process inside out.
Rather than trying to print a large volume of tissue and leave hollow channels for vasculature in a layer-by-layer approach, Chen and colleagues focused on the vasculature first and designed free-standing 3D filament networks in the shape of a vascular system that sat inside a mold. As in lost-wax casting, a technique that has been used to make sculptures for thousands of years, the team's approach allowed for the mold and vascular template to be removed once the cells were added and formed a solid tissue enveloping the filaments.
"Sometimes the simplest solutions come from going back to basics," Miller said. "I got the first hint at this solution when I visited a Body Worlds exhibit, where you can see plastic casts of free-standing, whole organ vasculature."
This rapid casting technique hinged on the researchers developing a material that is rigid enough to exist as a 3D network of cylindrical filaments but which can also easily dissolve in water without toxic effects on cells. They also needed to make the material compatible with a 3D printer so they could make reproducible vascular networks orders of magnitude faster, and at larger scale and higher complexity, than possible in a layer-by-layer bioprinting approach.
After much testing, the team found the perfect mix of material properties in a humble material: sugar. Sugars are mechanically strong and make up the majority of organic biomass on the planet in the form of cellulose, but their buil
|Contact: Evan Lerner|
University of Pennsylvania