3D Method Uses Ice for Building Artificial Blood Vessels

Researchers hope a new 3D printing method that involves ice could eventually be used in artificial organ development, narrowing the gap between the availability of organs and the demand for transplants.

Tissue engineering aims to assemble functional constructs to restore or improve damaged tissues or whole organs. The U.S. Food and Drug Administration (FDA) has approved artificial skin and cartilage, although they have limited use in human patients.

Creating blood vessel networks in artificial organs that work like natural ones — from tiny capillaries to larger arteries — remains a major challenge in tissue engineering.

This is because traditional artificial blood vessel designs often don't mimic the natural design, preventing them from functioning properly in the body.

The new research that will be presented at the 68th Biophysical Society Annual Meeting suggests that 3D ice printing may be used to create structures that resemble blood vessels in the body.

3D printing is a process of making three-dimensional objects from a digital file, the application of which ranges from medicine to manufacturing and design. Meanwhile, 3D ice printing generally involves adding a stream of water to a very cold surface.

"What makes our method different from other kinds of 3D printing is that instead of letting the water completely freeze while we're printing, we let it maintain a liquid phase on top. This continuous process, which is what we call freeform, helps us to get a very smooth structure. We don't have a layering effect typical with many 3D printing," said Feimo Yang, a graduate student in the labs of Philip LeDuc and Burak Ozdoganlar at Carnegie Mellon University.

The research team also used heavy water, a form of water where the hydrogen atoms were replaced by deuterium. This gives the water a higher freezing point and helps create a smooth structure.

The 3D-printed ice templates were embedded in a gelatin material, GelMA. Exposure to UV light makes the gelatin harden, and the ice melts away, leaving behind realistic blood vessel channels.

The researchers say the study has successfully demonstrated they could introduce endothelial cells, like those in blood vessels, into the fabricated blood vessels. The cells survived on the gelatin for up to two weeks, and the researchers intend to culture those cells for a longer duration in future research.

Yang says 3D-printed blood vessels could be utilized to test the effects of drugs on blood vessels. Moreover, they could also be coated with a patient's own cells to see how the cells respond to a drug treatment before giving it to the patient.

A dire need for transplants

More than 100,000 individuals in the United States are currently in need of organ transplants, and about 6,000 Americans die while waiting each year.

Although the new 3D ice printing method shows promise in improving tissue engineering, it is a long way from being routinely used in patient treatment.

Thus far, supplemental bladders, small arteries, skin grafts, cartilage, and a full trachea have been implanted in patients, but the procedures remain experimental and very costly.

While scientists have managed to successfully recreate complex organs like the heart and lungs in the lab, they are unlikely to be implanted into patients in the near future.

At the same time, artificially created tissues can be used to speed up drug development and improve personalized medicine while cutting costs and reducing the number of animals used for research.

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