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HomeScienceBlood vessels made with 3D-printed ice could improve lab-grown organs

Blood vessels made with 3D-printed ice could improve lab-grown organs

A 3D printed blood vessel ice template

A 3D printed blood vessel ice template

Philip LeDuc et al./Carnegie Mellon University

Complex artificial organs could be created by 3D printing a mold of veins, arteries and capillaries in ice, melting it in organic material and then allowing the ice to melt, resulting in a delicate, hollow network. This leaves room for the intricate artificial blood vessels required to grow lab-grown internal organs.

Researchers have been working on artificial organs for decades to help meet the high global demand for heart, kidney and liver transplants. But creating the networks of blood vessels needed to keep them alive remains a challenge.

Existing techniques can grow artificial skin or ears, but any flesh or organ material dies if it is more than 200 micrometers from a blood vessel, says Philip LeDuc of Carnegie Mellon University in Pennsylvania.

“It’s like twice the width of a hair; Once that is overcome, if there is no access to nutrients, the cells begin to die,” she says. Therefore, internal organs require new processes to make them cheap and fast.

LeDuc and his colleagues had experimented with printing blood vessels with meltable wax, but this requires reasonably high temperatures and can leave residue. “Suddenly one day, my student says ‘why don’t we just use water, the most biologically compatible material in the world?'” LeDuc says. “And I’m like ‘oh yeah.’ It still makes me laugh. It is very simple”.

They developed a technique that uses 3D printers to create a mold of the inside of an organ’s blood vessels on ice. In tests, these were embedded in a gelatin material that hardened when exposed to ultraviolet light, before the ice melted.

The team used a platform cooled to -35°C and a printer nozzle that dispensed hundreds of water droplets per second, allowing structures as small as 50 micrometers wide to be printed.

LeDuc says the process is conceptually simple but needs to be fine-tuned: You dispense droplets too quickly and they don’t freeze fast enough and fail to create the desired shape, but you print them too slowly and they just clump up.

The system is also affected by weather and humidity, so researchers are investigating using artificial intelligence to keep the printer tuned to different conditions.

They also used a version of water in which all the hydrogen is replaced by deuterium, a stable isotope of the element. This so-called heavy water has a higher freezing point and helps create a soft structure by preventing unwanted crystallization. Tests have shown that it will be safe when creating artificial organs, since deuterium is not radioactive, unlike some isotopes, LeDuc says.

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