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One of the best ways to appreciate the beautiful complexity of something is to try to reproduce it yourself. This is especially true in the quest for human organ biopsies for the hundreds of thousands of people on a waiting list for a life-saving transplant. Today, bioengineers have taken a valuable step forward with a "revolutionary technique" for printing vascular tissues.
Vascular networks are essential pbadages for the transport of blood, air, lymph and other nutrients. The architecture of such a system is vast and complex, with independent networks "such as the airways and blood vessels of the lung or the bile ducts and the blood vessels of the liver," physically and biochemically entangled.
"The liver is particularly interesting because it performs 500 breathtaking functions, probably second only to the brain," said co-lead author Kelly Stevens of the University of Washington School of Medicine and UW College of Medicine. Engineering, in a statement. . "Because of the complexity of the liver, there is currently no machine or therapy that can replace all of its functions in the event of a failure of the organ, and human-print organs could someday provide this therapy."
To achieve this goal, the team has developed a new bio-printing technology called "stereolithography apparatus for tissue engineering" (SLATE), which allows to produce flexible hydrogels layer by layer. Once the gel layers are printed, they solidify under a blue light. A food coloring widely available in the food industry is used to absorb blue light and refine the place where fine and delicate layers are formed. This process allows the team to produce a complex, biocompatible, water-based gel in minutes.
The team worked with Nervous System to design and test the technology by shaping a structure that mimicked the lungs and tested for stress with blood and air blown through its tissues – the bio-printed pattern withstood. They discovered that red blood cells could even absorb oxygen when the air bag "breathed".
"When we founded Nervous System, our goal was to adapt nature's algorithms to new product design methods," said co-author Jessica Rosenkrantz. "We never imagined that we would have the opportunity to revisit this case and design living tissues."
The 3D printing system can even make bicuspid valves – those that only allow blood to flow in one direction. These one-way valves are found in the human heart, leg veins and lymphatic system.
"With the addition of the multivascular and intravascular structure, we are introducing a vast set of design freedoms for live tissue engineering," said Jordan Miller, co-lead author of Rice University. "We now have the freedom to build many of the complex structures found in the body."
Replicating such an evolutionary feat would be beneficial for transplant patients by providing them with replacement organs from their own cells. At present, transplant recipients must take a lifetime of immunosuppressive drugs to prevent rejection of the organ from a foreign donor.
Bio-printed organs for transplant patients are not on the table for the moment and their development will probably take much longer. To help accelerate progress in this area if needed, the team said their creation was open and freely available. The study is published in the journal Science.
"Making the hydrogel design files available will allow other people to explore our efforts here, even if they use a future 3D printing technology that does not exist today. Hui, "added Miller.
"We are only at the beginning of our exploration of the architectures present in the human body, we still have a lot to learn."
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