Hardware

3D 'bioprinting': 10 things you should know about how it works

Using living cells to 3D print organs may sound far-fetched, but it's happening. Bioprinting is quickly gaining traction. Here's how it works.

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Using Organovo's NovoGen MMX bioprinter, cells are layered between water-based layers until the tissue is built.
Image: Organovo

The healthcare industry is trying to capitalize on 3D printing, and fast. From prosthetic limbs and various surgical devices made with plastics and metals, to using cells to print human organs, experiments in this industry are progressing quickly.

The world of bioprinting is still very new and ambiguous. Many of the innovations have been driven by either companies like Organovo that focus on bioprinting or specific researchers at universities, like Dr. Anthony Atala at Wake Forest.

Confusion has swirled around 3D bioprinting. It can be a difficult concept to get your head around, and it has been misconstrued at times. Atala, for instance, was misrepresented in articles about a TED Talk he gave. The articles said he printed a functioning human kidney, when in reality, it was only a prototype.

To help clear things up, we've compiled a list of 10 things to get you up to speed — or to at least help you figure out — how bioprinting works and where it is headed in the near future.

SEE: How 3D bioprinting is changing the world: Photos of 10 great projects

1. CT scans can function like a CAD design

Instead of trying to create an organ or tissue model from the ground up, researchers and engineers can use a CT scan or MRI to create a 3D model to print. For example, the University of Louisville, when creating a 3D printed model of a young boy's heart so doctors could use it for his surgery, the researchers used the CT scan from his doctor to make the 3D design model. Websites like Instructables even have tutorials to describe how to turn a CT scan into a 3D printable model to print.

2. There are multiple types of printers

Bioprinters: Organovo made the first commercially used bioprinter, called NovoGen MMX, which is the world's first production 3D bioprinter. The printer has two robotic print heads. One places human cells and the other places a hydrogel, scaffold, or other type of support.

"Inkjet" inspired printers: Experiments with bioprinting at Wake Forest University were inspired by traditional inkjet printers. The printer allows multiple cell types and components to be used for printing. In early forms of the technology, cells were placed in the actual walls of ink cartridges and the printers were programmed to place the cells in a particular order. Today, the university has adapted that technology so that skin cells can be placed in an ink cartridge and printed directly on a wound.

Six-axis printer: At the University of Louisville's Cardiovascular Innovation Institute, Dr. Stuart Williams is using a robot/printer that, instead of building the tissue from the ground up, as traditional 3D printers do, can build multiple parts of the heart tissue he is making at the same time and move them around accordingly.

"We've built a six-axis printer that can print layers but come back and start printing a new layer on the outside [of the heart]," Williams said. "The valves are in one spot, and we use robot to bring the valves in and puts them in parts of the heart."

3. Cells are used like "ink"

Organovo thoroughly explains the 3D bioprinting process in this video. Basically, once a tissue design is selected, the company makes "bio-ink" from the cells. Using a NovoGen MMX bioprinter, the cells are layered between water-based layers until the tissue is built. That hydrogel in between layers is sometimes used to fill spaces in the tissue or as supports to the 3D printed tissue. Collagen is another material used to fuse the cells together. This layer-by-layer approach is very similar to the normal 3D printing process, where products are built from the ground up.

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Cells are fused together with hydrogel to create tissue.
Image: Organovo

4. Stem cells are also used in bioprinting

Stem cells can adapt easily to tissues, so they are an attractive option for bioprinting different organs and bones. Researchers at the University of Nottingham in the UK experimented with building bone replacements coated with stem cells that develop into tissues over time. The researchers said development of stem cell repair for complex tissues, like those that make up the heart or the liver. It's difficult to use stem cells to build these organs, but it may be possible with 3D bioprinting.

5. Bioprinting is more complicated than other 3D printing

Let's explain this process in a bit more detail. In the case of Organovo, a bioprinter is used to create liver tissue, which is one of the original experiments in bioprinting by the company. Spheroids of parenchymal (or fundamental) liver cells are loaded into a syringe. In another syringe, nonparenchymal liver cells and the hydrogel, which fuses together to create a bio-ink, is loaded. The bio-ink makes a mold in the cell dish, and the liver cells fill up the rest of the dish. When the cells are put in an incubator, they fuse together even more to form the full liver tissue.

6. There are many other materials to use in bioprinting

Cells don't have to be the end all, be all of bioprinting. Many people still consider biodegradable or biocompatible materials that can be used to build body parts or repair damaged ones as an aspect of bioprinting. Printing materials that can improve bones, cartilage, and skin is just as important for the future of this technology. Some of the materials include certain types of flexible plastic, like the absorbable one used to make 3D printed windpipe splints for a baby who had a condition that caused his trachea to collapse; and titanium powder, which was used to create a jaw implant for a woman who had an infection.

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Titanium implants were used to reshape a man's face in the UK.
Image: Abertawe Bro Morgannwg University Health Board

7. 3D printed tissues for pharmaceutical testing

Since the technology is not advanced enough yet to create a full organ, the tissue samples are perfect to test drugs and other medical advancements. Instead of having to use human beings or animals as guinea pigs for pharmaceutical testing, bioprinting may provide a much more cost-effective and ethical option, while still being accurate because it the tissue samples are made from human cells.

8. Reproducing cells is nothing new

For years, scientists have been growing cells in laboratories, including skin tissue, blood vessels, and other cell cultures from various organs. Replicating and growing cells in petri dishes is nothing really new, and the science surrounding this is constantly advancing. However, 3D printing offers an opportunity to print an entire organ, not just pieces of one. It also may drastically reduce the cost of these processes because of the cells and other materials used.

9. Printing the networks of veins is a large obstacle

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A 3D printer is used to accurately layer cells to make tissue.
Image: Organovo

Vascularization is a big obstacle in the way of 3D printing organs, because they need to have a system of arteries, capillaries, and veins that support the system. They must be present to deliver nutrients and remove waste created by the cells. One option is to leave the space in the 3D printed tissue for veins to be added later on in the process, but researchers are now trying to figure out a way to print blood vessels as well.

One experiment at the University of Pennsylvania used a RepRap printer to make templates of blood vessel networks out of sugar. When they dissolve, the sugar was washed out without harming the cells and the space for the blood vessels is there. Researchers at Harvard have also started working on this issue, but they are trying to 3D print the blood vessels themselves by integrating them with skin cells.

10. The body can reject the 3D printed cells

In any transplant or surgery, there is always the risk of the body rejecting the organ or cells. This can even occur when tissue from one area of the body is put into another area of the body. The organ (or piece of tissue) also has to have time to integrate into the body after the implant. Since the technology for 3D bioprinting is so new, doctors and engineers have not even gotten to this point yet, but it's important to recognize these risks well in advance.

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About

Lyndsey Gilpin is a former Staff Writer for TechRepublic, covering sustainability and entrepreneurship. She's co-author of the book Follow the Geeks.

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