A red, walnut-sized 3D prostate sits in a gloved hand

The New Shape of Medicine: how 3D printing may save lives

Michael McAlpine and his colleagues are building organ models to help surgeons prepare for surgery. They also have made a device to treat spinal cord injuries and taken a first step toward a bionic eye.

Photo: A 3-D printed prostate model

If you went in for an operation, you would want your surgeon to know exactly what to expect from the organ being operated on. But while individuals’ organs have many features in common, their anatomical and mechanical properties differ in ways that often can’t be foreseen.

Practice with stand-ins for upcoming patients’ organs could reduce surgical errors and potentially save lives. That’s why Michael McAlpine and his colleagues in the University of Minnesota’s College of Science and Engineering have invented a way to print 3D replicas of organs, starting with the prostate gland.

Working with data from MRI scans and tissue samples from three patients, the researchers used a mix of customized silicone-based inks—which they developed—and “tuned” them to match the anatomy, mechanical properties, and tactile feel of the real prostates. They also equipped the replicas with 3D printed sensors to help surgeons determine the organs’ limits and obtain feedback.

For example, “Electrical sensors give quantifiable feedback, so surgeons can see a number that represents the pressure they’re applying,” says McAlpine. “They can tell how much is too much and ease back before getting there.”

Just the beginning

This technology is staring into a bright future.

The researchers hope to print 3D models of more complicated organs. For instance, when an organ has a tumor or a deformity, a patient-based model would allow a surgeon to experiment with different approaches to removing the growth or correcting the condition.

Also, “If we could replicate the function of these tissues and organs, we might someday even be able to create bionic organs for transplants,” McAlpine says.  

Speaking of which, his group has recently achieved the 3D printing of light receptors on a domed surface, a step toward fashioning a bionic eye for the seeing-impaired.

A gloved hand holds a model eye, with a blue iris and light sensors radiating like black spokes from the pupil.

U of M researchers have 3-D printed a light-sensing array on a hemisphere.

A 3D array of light-sensing devices is printed on a glass hemisphere.

Replacing neurons in damaged spines

Spinal cord injuries can be devastating, but in most cases the cord is bruised rather than cut. McAlpine and his colleagues are developing a 3D printed “bridge” that would allow neurons to reconnect across the site of injury. This could bring relief to patients suffering pain or loss of function.

Along with Ann Parr, assistant professor in the Department of Neurosurgery and the Stem Cell Institute, and James Dutton, research assistant professor in the Stem Cell Institute, McAlpine has printed a potent 3D mix of silicone fibers and stem cells programmed to develop into neurons.

The silicone fibers form a scaffold structure. When surgically implanted, the “silicone alleys” between the fibers would become conduits that guide the developing neurons around the wound and lead to connections between neurons on either side of it.

“We want to tailor the shape of the scaffold to encourage both ends of damaged neurons to reconnect properly,” says McAlpine.

A tiny white, translucent, right-angled section of a silicone bridge sits on a fingertip.

A prototype scaffold of silicone fibers to connect neurons across a spinal cord injury. 

A scaffold and neuronal stem cells are 3-D printed.

The team also adds cells that generate the coating that insulates neuronal fibers—which conduct electrical impulses—and speeds those impulses along.

“We’ve found that relaying signals across the injury could improve functions for the patients,” says Parr. “There’s a perception that people with spinal cord injuries will only be happy if they can walk again. In reality, most want simple things like bladder control or to be able to stop uncontrollable movements of their legs. These simple improvements in function could greatly improve their lives.”

Meet the researcher

Michael McAlpine

Michael McAlpine

Associate Professor, Mechanical Engineering

https://twin-cities.umn.edu/node/276786
University of Minnesota, Twin Cities
09/27/2018