Organs. They are a complex collection of cells all bound together, working in concert to keep us alive and well. When someone loses an organ either through disease or accident, they need a replacement and they need it fast. The sad fact is that in the UK alone, on average, three people die every day waiting for a donated organ. While more people signing up to donate could reduce this number, there simply aren’t enough organs to go around.
Enter 3D printing.
3D printing is already being used in a medical context to print custom-designed synthetic stents, hip joints and other replacement bones for patients. Printed body parts raised 537 million USD last year, a growth of around 30 per cent on the previous year. However, 3D printing is not limited to non-living physical products that serve structural and mechanical purposes. Many researchers have begun working on 3D bioprinting, which is the printing of living cells to form functional tissues (layers of cells).
This technology has numerous applications. It can be used to test new drugs and vaccines and to replace injured or diseased tissue. The grand daddy of them all would be to print entire organs that can be used to replace damaged ones in patients, but alas we are not quite there yet.
The key feature that sets 3D bioprinting apart from other 3D printing methods is that it uses living cells as the ink. As you would expect, this comes with a set of challenges as traditional inks and plastics are more tolerant to being squeezed, heated and generally pushed around compared to living cells. One gentle method of printing cells involves the use of sound waves, which push tiny cell-containing droplets out of the printer head.
Another challenge that bioprinting faces is how to get the cells to stick together once printed. One method involves allowing the cells to grow and multiply in to small clumps of cells prior to loading them up in the printer. These clumps are naturally stickier than individual cells and so can be printed directly on to one another.
The strength of 3D bioprinting is the precision by which the cells can be printed into complex three-dimensional structures that mimic their natural biological counterparts. This feature allows the custom printing of biological tissues of specific size and shape required by the patient. Another advantage is that a patient doesn’t have to wait for a compatible donor organ, which isn’t even always successful.
3D bioprinting has already had a number of success stories. In a laboratory mouse model, it was successfully used to repair a skin wound by printing stem cells suspended in a gel directly on to the injury. Other tissues that have been printed include aortic valves, branching blood vessels and even an early prototype kidney. While we still need more people to sign up to donate their organs, 3D bioprinting is helping the future look ever brighter for those in need of a transplant.
Skardal A, Mack D, Kapetanovic E, Atala A, Jackson JD, Yoo J, Soker S. Bioprinted amniotic fluid-derived stem cells accelerate healing of large skin wounds. Stem Cells Transl Med. 2012 Nov;1(11):792-802