Holding the Future

Two years ago, at one of Stanford’s programs for surgical and anatomical technologies, I recall fiddling with a small, gear-shaped object. It was created using a 3-D printer and composed of polycarbonate, according to the instructor who handed me the object. After toying with the gear for a minute or two, I returned it to him. Neat, I thought – but not much else. I knew what 3-D printing was at the time, but nothing of its vast potential.

Today, it seems as though the entire world is buzzing about 3-D printing technology. It has become apparent to me that the technology used to craft the gear I held two years ago is the very same technology capable of producing everything ranging from functional plastic firearms to detailed sculptures. What I find most exciting, however, is news that 3-D printing could be used to print human organs and tissues in the future – a new field known as bio-printing.

So, What Is 3-D Printing?

3-D printing, simply put, is the process of building a three-dimensional structure from ground up, applying layer after layer on top of another. Think of a wafer cookie – a single, three-dimensional dessert composed of several stacked layers. In order to carry out the building process, the printer first requires a set of blueprints for the object it is printing. This comes in the form of a digital file – which contains information about the object’s dimensions and shape. There are several methods of constructing the layers. The first method uses a print head to spray material in sequential layers, allowing the material to solidify before applying another layer. The second method uses a laser to solidify a liquid or powdered substance layer, after which another layer of material is added on top for subsequent lasering. This technique is also known as laser sintering.

Modern Issues

As healthcare continues to improve, people keep on living longer. Unfortunately, as we age, our organs also become more prone to failure – thus, we see an accompanying increase in number of requests for organ transplants. Surgeon Anthony Atala – who delivered a 2011 TED talk on printing human kidneys – says: “In the last ten years, the number of patients requiring an organ has doubled, while in the same time, the actual number of transplants has barely gone up.”

To combat this issue, scientists have turned to regenerative medicine  – a field that focuses on replacing damaged or nonfunctional cells, tissues, and organs in the human body. Current techniques include using biomaterials – materials that can be implanted inside the patient to encourage regeneration – and cells, which can directly replace lost tissue. An example of using both biomaterials and cells would be the scaffolding technique – a technique in which degradable biomaterials are used to provide a temporary structure for cells to grow on, allowing them to form a tissue or organ-like structure.Another technique is the mold method – where a discarded organ is purged of all cells, leaving behind an extracellular matrix replica of the discarded organ that scientists can use as a mold to inject the patient’s own cells into.

However, neither technique is perfect. The scaffolding technique requires biomaterial structures similar in complexity to actual organs, and scientists have yet to figure out how to induce vascularization – or, the creation of a blood supply network – in scaffold-grown tissues. The mold method retains the original organ’s vascularity, but requires discarded organs – which, similar to organ transplants, are not readily available.

Where Bio-Printing Currently Stands

As technology continues to develop, 3-D printing becomes increasingly effective at solving these problems.

Using CT scans to create three-dimension data, scientists can input this information into a 3-D printer to print a remarkably accurate model of the scanned organ using biomaterials. This makes the scaffolding technique much more viable, reducing the challenge of replicating complex organ structures.

Additionally, 3-D printing has the capability of printing live cells directly onto scaffolding. Some scientists are even exploring the possibility of skipping scaffolding altogether, printing cells directly onto each other and relying on their self-organization to create structural integrity. For example, San Diego company Organovo successfully printed a small liver that functioned for forty days using this technique. Bio-printing is making progress, but still has a long way to go before being capable of churning out entire organs. Although Stuart K Williams, the scientific director of the Cardiovascular Innovation Institute at the University of Louisville, says that his team has already successfully engineered and printed the smallest blood vessels of the heart, no team has successfully printed an organ with the vessels necessary to support itself. Scientists have also yet to master the control of pluripotent cell differentiation under 3-D printing conditions; not only that, but 3-D printing is so sluggish that cells begin dying from lack of nutrients and oxygen before the organ is even close to completion.Some scientists estimate that fully-functional printed organs will be possible within the next decade, whereas some remain more skeptical. Whichever the case, despite the hurdles ahead of the scientific community, 3-D printing continues to redefine technology with its increasingly widespread number of applications and ever-advancing nature.