Episode 3: 3D-printed implant designed to repair spinal injuries

A silicon chip with 4 million microscopic mirrors is used to shine UV light in a 3D pattern based on a digital MRI image of the spinal cord wound in rats. The light falls onto a mixture of poly(ethylene) glycol and gelatin methacrylate, which solidifies into the shape of the wound.

Transcript
PRACHI PATEL: Welcome to MRS Bulletin’s Materials News Podcast, providing breakthrough news & interviews with researchers on the hot topics of 3D bioprinting, artificial intelligence and machine learning, bioelectronics, perovskites, quantum materials, robotics, and synthetic biology. My name is Prachi Patel.

Over 250,000 people around the world suffer a spinal cord injury every year. 

SHAOCHEN CHEN: Spinal cord damage turns out to be a very devastating disease. You know people cannot walk, they feel nothing below the hip and other parts of the body. 

PATEL: Shaochen Chen, a nanoengineer at the University of California in San Diego, worked with neuroscientists to 3D-print implants that can repair spinal cord injuries in rats. The implants are customized to fit the injury. The printer uses a silicon chip with four million microscopic mirrors to shine UV light in a three-dimensional pattern based on a digital MRI image of the wound. The light falls onto a mixture of poly(ethylene) glycol and gelatin methacrylate, which solidifies into the shape of the wound. The method is thousands of times faster than conventional 3D-printing techniques, which makes structures one drop or one layer at a time.

CHEN: So you can imagine we have about 4 million of these traditional printers doing the same work. And the speed is totally different. We can print the similar sized part in a matter of seconds versus 3 or 4 or 6 hours.

PATEL: Chen says the material and the structure of the implant make it unique. Neurons will usually grow around or turn away from foreign materials. But the hydrogel-gelatin combination attracts the cells. The implants have a solid supportive center surrounded by microchannels that are 200 micrometers in diameter. The researchers fill these channels with neural stem cells that urge neurons to grow.

CHEN: So if you put this implant in the gap of the damaged site of the spinal cord you hope, you know, that neurons can grow from both ends, they’d reconnect with the help of this kind of implant just like a bridge.

PATEL: That’s indeed what happened in rats with spinal cord injuries. The animals had no feeling or movement in their legs, but 11 weeks after getting the implants, they could feel their toes and move their knees. When the researchers removed the implants they saw that neurons had grown through the channels. The team is now moving on to test on monkeys. And Chen is doing a lot more with the 3D-printing method. 

CHEN: We have been using this technique to print heart tissues, liver tissues, and brain tissue, and also cancer tissue models.

PATEL: Pharmaceutical companies could use those printed human tissues for drug testing, which could drastically cut the time and cost of drug development.

CHEN: They don’t need to wait until, you know, 10 years to see if this compound or this drug is toxic to the heart or liver in a human setting. And, of course, the long-term goal is to have therapeutical uses of this 3D-printed tissue because they can repair, regenerate damaged tissue, for instance heart wall, for instance piece of liver due to cancer you can cut it out and put this 3D-printed liver piece to fix it.

PATEL: The research was published recently in the journal Nature Medicine. My name is Prachi Patel from the Materials Research Society.

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