3D-printed microchannels deliver oxygen, nutrients from artery to tissue implant

An innovative structure containing an intricate microchannel network of simulated blood vessels solves one of the biggest challenges in regenerative medicine: How to deliver oxygen and nutrients to all cells in an artificial organ or tissue implant that takes days or weeks to grow in the lab.
 
The new study was performed by a research team led by Jordan Miller, assistant professor of bioengineering at Rice, and Pavan Atluri, assistant professor of surgery at Penn.
 
Miller explained that one of the hurdles of engineering large artificial tissues, such as livers or kidneys, is keeping the cells inside them alive. Tissue engineers have typically relied on the body’s own ability to grow blood vessels, for example, by implanting engineered tissue scaffolds inside the body and waiting for blood vessels from nearby tissues to spread via arbolizaton to the engineered constructs.
 
But that process can take weeks, and cells deep inside the constructs often starve or die from lack of oxygen before they’re reached by the slow-approaching blood vessels. “What a surgeon needs in order to do transplant surgery isn’t just a mass of cells; the surgeon needs a vessel inlet and an outlet that can be directly connected to arteries and veins,” he said.
 
3D-printing pastry-inspired sugar glass to form an intricate microchannel capillary lattice. “We wondered if there were a way to implant a 3-D printed construct where we could connect host arteries directly to the construct and get perfusion [blood flow] immediately. In this study, we are taking the first step toward applying an analogy from transplant surgery to 3-D printed constructs we make in the lab.”
 
Miller turned to a method inspired by the intricate sugar glass cages crafted by pastry chefs to garnish desserts and that he had pioneered in 2012. Using an open-source 3-D printer to lay down individual filaments of sugar glass one layer at a time, the researchers printed a lattice of would-be blood vessels. Once the sugar hardened, they placed it in a mold and poured in silicone gel. After the gel cured, Miller’s team dissolved the sugar, leaving behind a network of small channels in the silicone.
 
“They don’t yet look like the blood vessels found in organs, but they have some of the key features relevant for a transplant surgeon,” Miller said. “We created a construct that has one inlet and one outlet, which are about 1 millimeter in diameter, and these main vessels branch into multiple smaller vessels, which are about 600 to 800 microns.