November 16, 2016

Printing New Bone Tissue at Your Desk

One question currently looms large in Kara Spiller‘s mind: How do broken bones manage to mend themselves perfectly, without leftover scars? Inside a Drexel University laboratory, Spiller is inching her way toward an answer with the help of the BioBot, a novel 3D bioprinter developed by two local entrepreneurs.

The BioBot is the invention of two University of Pennsylvania alumni, Danny Cabrera and Ricardo Solorzano. It’s similar in multiple ways to the MakerBot, the desktop printer that creates 3D objects by a successive layering of plastics on a fixed platform over time, with one difference: the BioBot is capable of printing living cell tissue. Typically bioprinters in use by universities and hospitals are large machines that cost hundreds of thousands of dollars, but the BioBot is the size of a desktop 3D printer, simple enough to learn how to use in an afternoon, and costs $5,000. Cabrera, Solorzano, and a small team currently manufacture BioBots and operate the business out of a second-floor office inside the NextFab makerspace on Washington Avenue. This weekend, the small startup that graduated from Philadelphia’s DreamIt Health incubator class last fall and has already sold more than 40 BioBots worldwide celebrates one year in business.

“As soon as you get a BioBot, you can print something,” Cabrera told me earlier this spring for an article I wrote for Fortune. “What we’re doing is we’re saying anybody can do this. [It’s] this MakerBot of biology idea.”

When I first encountered the BioBot in April, the 23-year-old Cabrera mentioned that Spiller, an assistant professor in the School of Biomedical Engineering, Science and Health Systems at Drexel, was making use of a BioBot. So I stopped by Drexel’sBiomaterials and Regenerative Medicine Laboratory to see how Spiller was putting her own BioBot to use.

“What we’ll be doing with the BioBots printer is printing bone, and then using that to study why bone heals itself perfectly,” Spiller says. “Is it the structure of the bone? There’s no way to test if it’s the structure without a 3D printer.”

Bone tissue is a complex and mysterious material, according to Spiller. We don’t quite know exactly why bone is able to heal itself perfectly. It could have something to do with the number and size of pores inside the bone, the small holes that make bone tissue resemble a sponge. (The fewer pores in a bone, the stiffer the bone is.) It could have something to do with the proteins, like collagen, secreted during the regeneration of bone tissue. It could have something to do with the fact that immune cells reside inside bone marrow. Discovering more about why bone operates in the manner it does requires testing each of these guesses, but doing so requires changing the structure of bone tissue, and that’s where the BioBot comes in.

To print viable, living cells with the BioBot, one must mix together actual cells, water, and biocompatible material, which is inserted into and then pushed out of a syringe with the help of an air compressor — this is the “printing” part — and cooled using blue LED lights. So far Spiller has used her BioBot to print gelatin, a derivative of collagen, without any cells encapsulated, just to ensure that a certain level of control can be exerted over whatever structure is printed. (If you can print gelatin that’s very soft as well as gelatin that’s very stiff, it’s likely you’ll be able to achieve the same effect when you finally do mix in living cells.) Over the next six months, Spiller says she and a group of students will begin using the BioBot to print mesenchymal stem cells (MSCs), adult stem cells found in bone marrow, that later differentiate into bone tissue. But Spiller and her team will look to affect the mechanical properties of these MSCs — the pore size, the stiffness — either by changing up the mixture inserted into the syringe or introducing certain proteins into the MSCs after they’ve been printed.

“Things like that, you absolutely need a printer to be able to control,” says Spiller. “In order to do these experiments, you need to be able to isolate variables one at a time.”

With the help of the BioBot, Spiller’s team might be able to start explaining the biology of bone tissue and why it’s able to regenerate flawlessly. And if that works out, the next step might be 3D printing an implantable biomaterial that could use the body’s own mechanisms to regrow bone.