WASHINGTON, May 2 (Xinhua) -- American bioengineers found a way to create exquisitely entangled vascular networks that can mimic the body's natural passageways for blood, air, lymph and other vital fluids.
The findings, reported on Thursday in the journal Science, could help clear a hurdle for 3D printing replacement organs.
One of the biggest obstacles to generating functional tissue replacements was that surgeons cannot print the complex vasculature that can supply nutrients to densely populated tissues, said the paper's co-author Jordan Miller, assistant professor of bioengineering at Rice University.
Also, the airways, blood vessels in the lung or bile ducts in the liver are physically and biochemically entangled, making an artificial constructs more challenging, according to Miller.
The researchers created a bio-printing technology that can make soft hydrogels one layer at a time. Their pixel sizes range only from 10 to 50 microns. Layers are printed from a liquid solution that becomes a solid when exposed to blue light.
They managed to confine the solidification to a very fine layer in order to produce soft, water-based, biocompatible gels with intricate internal architecture in a matter of minutes, according to the study.
The researchers made a hydrogel model of a lung-mimicking air sac, which is sturdy enough to avoid bursting during blood flow and "breathing," a rhythmic intake and outflow of air that simulated the pressures and frequencies of human breathing.
The findings showed that red blood cells could take up oxygen as they flowed through a network of blood vessels surrounding the "breathing" air sac.
They also 3D-printed tissues loaded with primary liver cells before implanting them into mice with chronic liver injury. Then the liver cells survived the implantation.
"The liver's complexity means there is currently no machine or therapy that can replace all its functions when it fails. Bio-printed human organs might someday supply that therapy," said the paper's co-author Kelly Stevens with the University of Washington.
Miller said his lab is already using the new design and bio-printing techniques to explore even more complex structures.
"We envision bio-printing becoming a major component of medicine within the next two decades," said Miller.