3D printed skin holds promise for burn victims and others

The 3D printer is about the size of a microwave oven

printalive bioprinter edited 3

About the size of a standard microwave oven, the PrintAlive Bioprinter places a patient's own grown cells along with other biomaterials into a micro-device, which then pushes them out through several channels.

Credit: University of Toronto

A 3D printer that can use a patient's own cells to print skin grafts, including hair follicles and sweat glands, has won a scientific design competition.

While still in pilot mode, the PrintAlive Bioprinter is in the process of being commercialized by MaRS Innovations in collaboration with the Innovations and Partnerships Office (IPO) of the University of Toronto, whose labs have filed two patents on the device.

Four University of Toronto engineers created the printer, which is about the size of a standard microwave oven. Last week, the machine won the James Dyson Award for student design, setting the stage for the group to compete for a $60,000 international prize.

diagram explaining how printalive bioprinter works University of Toronto

The PrintAlive Bioprinter 3D skin printer works by placing the victim's grown cells along with other biomaterials into a micro-device, which then pushes them out through several channels.  The biomaterials are then mixed, causing a chemical reaction that forms a "mosaic hydrogel," a sheet-like substance compatible with the growth of cells into living tissues. The hydrogel is rolled out in thin sheets that can create many layers of tissue.

The PrintAlive Bioprinter has been able to create uniform, large-scale engineering of tissue, which could be used to treat burn patients and other injuries.

The engineers who designed the printer include associate professor Axel Guenther, associate professor Milica Radisic, and graduate students Lian Leng, Boyang Zhang, and Arianna McAllister.

"There's a lot of interest in soft materials, particularly biomaterials," Guenther said in a university news release. "But until now no one has demonstrated a simple and scalable one-step process to go from microns to centimeters."

Along with producing skin cells, the machine can also produce hair follicles, sweat glands and other human skin complexities, "providing an on-demand skin graft for burn victims," the university stated.

Because the machine uses the patient's own cells, which are grown in a petri dish and then printed to form a bandage, it "would completely eliminate immunologic rejection, and the need for painful auto-grafting and tissue donation," McAllister said in a statement.

3D bioprinting an up and coming market

The University of Toronto is not alone in using 3D printing technology to create human tissue. Other university researchers and private companies are developing printing technology that could someday be used to replace organs and other body parts.

San Diego-based bio-printing company Organovo expects to unveil the world's first printed organ -- a human liver -- this year.

"We remain on track to launch our human liver tissue for use in drug discovery and medical research applications later in 2014," Michael Renard, Organovo's executive vice present of commercial operations, wrote in an email to Computerworld.

Like other forms of 3D printing, bio-printing lays down layer after layer of material -- in this case, live cells -- to form a solid physical entity (tissue). A major stumbling block in creating tissue continues to be manufacturing the vascular system needed to provide it with life-sustaining oxygen and nutrients.

The Wyss Institute for Biologically Inspired Engineering at Harvard University has created a 3D printer that can lay down four different types of cells at the same time. The breakthrough in that research has been the ability to create blood vessels that can feed living tissue.

"You can simultaneously print cells, vasculature as well as extra-cellular matrix. Each one of those are extremely important components within human tissue," said David Kolesky, a graduate student at the Wyss Institute.

"You can also print cells on top of and around it. As you can imagine, human tissue is inherently complex and composite and you have multiple cell types right next to each other - on top of and around vasculature. In fact every cell is within a few microns of a blood vessel in your body."

3D printing also allows enough tissue and supportive vasculature to be constructed quickly so that enough living cells can survive to create functional tissue.

Organovo said it has also overcome the vascular issue to a degree. "We have achieved thicknesses of greater than 500 microns, and have maintained liver tissue in a fully functional state with native phenotypic behavior for at least 40 days," said Michael Renard, Organovo's executive vice president of commercial operations.

How it works

The University of Toronto's PrintAlive Bioprinter 3D skin printer works by placing the patient's cells along with other biomaterials into a micro-device, which then pushes them out through several channels. The biomaterials are then mixed, causing a chemical reaction that forms a "mosaic hydrogel", a sheet-like substance compatible with the growth of cells into living tissues. The hydrogel allows the various dermis cells to be seeded in precise and controlled patterns.

3d skin printer channels University of Toronto

The 3D printer's micro-device pushing cells out through several channels to create a thin film of tissue.

3d skin printer printing skin University of Toronto

A layer of skin is printed and then rolled up into layers of tissue.

The printing technique is different from others, the scientists said, because it doesn't require an artificial, but biodegradable, scaffolding to hold the cells together. Typically, 3D bio printing requires cells to be placed onto an artificial structure capable of supporting three-dimensional tissue formation.

The placement of the cells by the printer is so precise that the researchers were able to spell words, such as Toronto, demonstrating how they could mimic the natural placement of cells in living tissues.

The mosaic hydrogel sheets are collected around a drum, which allows the formation of layers as it turns, creating, in essence, three-dimensional, functional tissues.

"In this case, when we put the cells in the right places, we create cellular organization quite naturally," Leng said.

So what's the next step?

Along with treating burn victims, the 3D-printed tissue could be used for testing therapeutic drugs, potentially eliminating the need for arduous and highly regulated animal and human trials.

The university researchers are working with a burn unit at Toronto's Sunnybrook Hospital.

"At some point [the machine] could allow dermal [skin] grafts to be prepared that perhaps will be less expensive and more efficient," Guenther said.

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