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As we have mentioned in previous articles on additive manufacturing, or 3D printing, will go on to impact just about every major industry across the world, and healthcare is no exception. We have already seen how 3D printing can benefit the healthcare industry with the recent coronavirus pandemic, when engineers and novice printers developed ways to rapidly manufacture PPE, medical equipment, and even temporary structures for people self-isolating. 

Leading 3D printing companies like Carbon, Prusa Research, and Formlabs are printing face shields, masks, and crucial hospital tools for healthcare professionals. The overall 3D printing community has been hard at work to ease the pressure on supply chains and governments.

3D printing holds the promise of changing the healthcare industry for the better by offering products such as smarter drugs and hyper-customized prosthetics. However, like something out of the 1990 film Dark Man, in the near future, it might become commonplace for doctors to treat patients with printed organs. In fact, this is already happening. Researchers from various leading universities have 3D-printed functioning human organs. This could help to address the shortages of donor organs around the world, and especially in the United States.

3D Printed Organs could save people’s lives

Source: The Scientist

Due to the tremendous demand for donor organs, it has been estimated that 900,000 deaths each year could be prevented using engineered organs. Currently, in the United States, there are 113,000 men, women, and children on the national transplant waiting list as of July 2019. Sadly, on average, 20 people die each day while waiting for a transplant, while a new person is added to the waiting list every 10 minutes. 3D printed organs could be a viable solution to this problem. In addition, these engineered organs are very cost-effective. 

For example, according to the National Foundation for Transplants, a standard kidney transplant, on average, costs upwards of $300,000, whereas a 3D bioprinter, the printer used to create 3D printed organs, can cost as little as $10,000 and costs are expected to drop further as the technology evolves over the coming years. This is one of the many reasons why medical professionals and researchers are excited about the coming age of 3D printed organs.

Today we are going to further explore the implications of 3D bioprinting, the challenges, benefits, and potential issues of this revolutionary new procedure. Over the next couple of years, the demand for bioprinting is only expected to increase. 

The basics: What is 3D bioprinting?

The Science Fiction World of 3D Printed Organs
A 3D printed heart created by Rice University. Source: Rice University

You may hear the process of 3D-printed organs described as 3D bioprinting, and the final products (organs) called engineered organs. In short, the process of bioprinting is similar to many of the additive manufacturing processes you are familiar with. However, in this case, the process involves the use of cells and growth factors to create tissue-like structures and eventually organs. Think of your standard fused filament fabrication (FDM) printer. Chances are, you have seen one in action or maybe even have one on your desktop right now. The process is very similar.

The Science Fiction World of 3D Printed Organs
The process of 3D printing a heart. Source: Wiley Online Library

When you want to 3D print something, the first thing you have to do is create a digital model, which is then printed as a physical product, layer by layer, using thermoplastic. Bioprinting works in a similar way, with researchers first creating a digital model of the tissue they want to create, followed by the process of printing the organ layer by layer. However, because bioprinters are using sterile cells, the resolution of the print (layer height) and matrix structure need to be prepared differently than when using thermoplastics.

Breaking it down further, closely resembling the pre and post-production of stereolithography apparatus printing (SLA) researchers first create the digital model for their print using technologies like computed tomography scans and magnetic resonance imaging scans. Printers are then prepared and sterilized.

Next, the digital model is sent to the printer. Researchers use bioink, a suspension of living cells, to print their structures. Just like a filament, the bioink is placed in a printer cartridge and is used to create the physical 3D model. Finally, during the post-production phase, after the print is completed, researchers mechanically and chemically stimulate the organ to ensure that it will function. 

Bioink is the “filament” used in bioprinters

The Science Fiction World of 3D Printed Organs
Source: All3DP

To print an organ, scientists need to deposit cells specific to the organ they are building. For example, to create a liver, they would start with hepatocytes — the primary liver cells — as well as other supporting cells. As the cells are printed and accumulate on the platform, they are embedded in a microgel support matrix (or scaffold) and assume the shape of the organ. Scientists could also start with a bioink consisting of stem cells, which can differentiate into the desired target cells.

To prevent organ rejection, medical professionals have to match highly compatible people, there are many factors that go into compatibility. However we can circumvent this problem by using the recipient’s own cells to create the bioink.

For simple organs, researchers first print a 3D scaffold made of biodegradable polymers or collagen. They use CAD software to design an exact digital model of the organ. They then print out the scaffold, which will provide a temporary surface for the cells to cling to.

The cells are harvested by taking a biopsy of the patient’s organ. These cells are then grown in a culture, until there are enough cells to cover the scaffold. The scaffold is “seeded” with the cells by hand. Once the cells have grown and organized themselves, turning into a working organ, the organ is implanted into the patient and the scaffold disappears.

More complex organs may be printed without a scaffold. To do this, doctors again use CT and MRI scans and combine these with the patient’s medical data to build a slice-by-slice model of the patient’s organ. This model is then printed, using bioink and a polymer gel to create the tissue. Once complete, the organ is placed in an incubator, to allow the cells to organize and fuse together to form a working organ. 

It is this last step that is proving challenging. Another issue is the blood supply to the organ. although scientists have printed larger blood vessels, bioprinting doesn’t yet offer sufficient resolution to create the tiny, single-cell-thick capillaries needed by a healthy organ.

Have people 3D printed organs yet? 

The Science Fiction World of 3D Printed Organs
Source: Tel Aviv University

The short answer is yes. Back in 2017, a team of researchers from the Pohang University of Science and Technology developed and 3D printed what they dubbed “bio-blood-vessels,” by utilizing materials from the human body as a template for the process. The blood vessel functioned very well. While researchers from Harvard University, just a year earlier, developed a new type of bioink specifically for building kidneys, allowing the team of researchers to recreate vital parts of the kidney. 

A team from the bioprinting startup Organovo in San Diego has already gone on to demonstrate that it can print human liver patches and implant them into mice.

The Science Fiction World of 3D Printed Organs
The University of Minnesota’s 3D printed prostate Source: University of Minnesota

Human trials for liver transplants could start as early as next year. The idea of bioprinting human organs is clearly no longer some far off science fiction idea. Researchers from private companies and leading universities have printed ears, lungs, and even a heart. 

Researchers from Carnegie Mellon University have recently created the first full-size 3D bioprinted human heart digital model using their Freeform Reversible Embedding of Suspended Hydrogels (FRESH) technique. This novel additive manufacturing method utilizes a needle to inject bioink into a bath of soft hydrogel to support the print. The technique allows for the creation of complex organ features and characteristics.

The Science Fiction World of 3D Printed Organs
Carnegie Mellon 3D printed heart. Source: Carnegie Mellon Univerity

The heart printed by the team feels and looks like the heart pumping in your body right now. Organ prints like these can be used to educate both surgeons and patients on the structure of a heart. 

Bioprinting technology is far from perfect

The Science Fiction World of 3D Printed Organs
A 3D printed bionic eye. Source: University of Minnesota

Yes, there have been multiple successful efforts in creating engineered tissues and organs. However, the technology still has a ways to go before it is fully adapted in hospitals near you. There are some obvious hurdles we need to overcome.

First, bioprinting needs to become faster as well as be able to produce tissues at a higher resolution. Being able to 3D print an organ in a matter of hours or minutes could make 3D bioprinting far more commercially appealing. At the same time, the higher resolution would allow for better interaction and control in the 3D microenvironment, and would allow the creation of the fine structures needed to develop a healthy and working organ.

Secondly, we need a more diverse biomaterial catalog to work with. At the moment, it is like printing with only a few filaments. Just like with an FDM or even SLA printer, you use different printing materials to tackle different jobs.

The same goes for the world of bioink and the complex and various types of medical tissue treatments that humans may need. Nevertheless, the technology is exciting and as mentioned above, could save millions of lives one day. Growing competition in the private sector could help spawn the quick innovation needed to make 3D printing viable.

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