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Bioprinting Technique: Makes It Easier to Study Human Tissues and Organs

With this bio-printing technique, we are one step closer to organ printing!

Researchers at the University of Washington and Rice University have developed a new bio-printing technique that removes one of the major hurdles in the 3D printing path of alternative organs. The invention allows for the construction of sophisticated vascular networks that act like natural passages of blood, air, lymph, and other vital fluids to the human body.

While designing this technique, the research team has also developed a concept proof model. The hydrogel model of the airway emulsion of the lung, whose airways deliver oxygen to the blood vessels around it. A more interesting experiment is the implantation of bio-printed structures containing liver cells in the mouse body.

Jordan Miller is an assistant professor of biological engineering at Rice University and a member of the research team. The scientist says about the importance of such techniques in the field of bio-printing:

"One of the biggest barriers to the production of alternative functional tissues is our inability to print complex vessels that deliver nutrients to dense tissues. In addition, our organs contain independent vascular networks, such as the airways and blood vessels of the lungs or bile ducts and blood vessels in the liver. These composite networks are physically and biochemically intertwined and their structure goes directly back to the application of the tissue. "Our technique is the first bio-printing technique to provide a simple and comprehensive answer to the challenge of multiple vascularizations."

This problem dates back to a generation in the field of tissue engineering. But now with this new technique, not only this challenge has been resolved, but new questions and openings have opened up along the way. Now we can ask if we can print tissues like healthy tissues in our body, would the practical behavior of these printed tissues be similar to body tissues? This is an important question because the quality of the biopsy tissue determines its success rate as a treatment.

Printed organs

The goal of the researchers to print healthy and efficient organs is to help humans transplant organs. In the United States alone, more than 6,000 people are on organ transplant waiting lists and those who eventually receive them have to consume immunosuppressive drugs all their lives in order for their bodies to donate.

In recent decades, biotransformation has attracted much attention because it theoretically allows doctors to print alternate organs from their cells, thereby resolving both problems. Imagine a day when a ready source of efficient organs would save the lives of millions of people around the world. Professor Miller expects suppression to become one of the key components of medicine in the next two decades.

Scale model of lung emulator airbag prepared for testing

Of all the organs that can be printed with this technique, the liver is the most interesting because it functions at the same time as infertility, and only the brain is superior to it. The complexity of the liver means that there is currently no device or treatment that can replace the problem. Perhaps someday human organs will provide this treatment.

To address this challenge, the research team has developed an open-source biotechnology technology called "Stereolithography for tissue engineering" or SLATE. The system uses incremental production to fabricate soft hydrogels in layers.

Layers are printed with pre-hydrogel fluid which hardens when exposed to blue light. A digital light-processing projector illuminates the hydrogel form below and displays high-resolution, 2-dimensional sequences of high-resolution, 2 to 5-micron pixels.

When the layers are hardened, a three-dimensional gel aerial arm rises high enough to expose the liquid to the next image of the projector. One key to the success of this technique is to add food coloring that absorbs blue light. These optical absorbers limit hardening to a very delicate layer. This allows the system to produce highly soft, water-based biological gels within a minute with a sophisticated internal structure.

Breathing lungs!

Experimentation of the lung imaging structures produced by this biopsy technique showed that the tissues were strong enough not to explode during blood flow and pulmonary respiration. Breathing is the entry and exit of rhythmic air that simulates the pressure and frequency of human breathing.

Experiments have shown that red blood cells can absorb oxygen as they pass through the blood vessel networks around the breathing air sac. This movement of oxygen is similar to the gas exchange that occurs in the pore-filled air sacs.

Production of living tissues by means of bio-printing

The research team added liver stem cells to the tissues and implanted them into the body of mice to test the therapeutic implants of liver disease (tissues printed by themselves). The tissue had separate compartments for blood vessels and liver cells, and the researchers placed it in a rat's body with chronic liver disease. The results showed that the liver cells survived after implantation.

This new bio-printing system can also produce intramuscular features, such as bicuspid valves that allow one-way barrier flow. Intramuscular valves are present in the heart, arteries and complementary networks of the human body, such as the lymphatic system, which has no pump to direct flow.

By combining the intramuscular and multi-vascular structure, this new system has dramatically enhanced the viability of live tissue engineering. Now researchers have the freedom of action needed to build many of the complex structures of the human body.

Open-source data for the bio-printing system

The research team is developing the commercialization of this technique and its achievements through a startup company called Volumetric in Boston. This startup is working to design and produce bio-printers and bio-inks.

All source data used in the experiments are published for free. This data also includes all the 3D printing files required for stereolithographic printing and all the hydrogels used in the experiment.

The research team is still working to produce more sophisticated textures and structures with this bio-printing technique. This is a breakthrough that will not only fulfill the dream of transplantation, but it will transform our understanding of the architecture and structure of the human body.

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