Despite significant medical advances, spinal cord damage remains one of the most difficult physical injuries to treat. Scarring frequently gets in the way of nerve fiber regrowth, while nerve cells usually cannot regenerate on their own. A possible solution? A fleet of stem cell-infused, injectable nanorobots that can help nerve cells regenerate. The tiny bots are detailed in a study recently published in the journal Nature Materials.

To build their new tools, a team at ETH Zurich in Switzerland engineered microscopic machines that combine living neural progenitor cells (NPCs)—specialized stem cells developed for the spine—with customized nanoparticles. These customized nanoparticles feature two layers—one that is sensitive to magnetic fields and another that translates them into electrical signals.

“We place a reservoir in the center where we trap the cells. Then we inject the nanoparticles and wait for the two components to bind,” Salvador Pané i Vidal, a study co-author and ETH Zurich roboticist, said in a statement.

Each nanorobot is about six micrometers wide, making them smaller than a red blood cell. However, the number of robots required to pull off a procedure is immense. Millions of nanobots are needed during animal trials. Even with such a high number, the initial experimental results are promising. In tests involving mice with severed spinal cords, nerve cells stimulated by the microrobots began reconnecting at the injury site within 28 days. By the end of the trial, the mice displayed major improvements in movement, gait, coordination, and exploratory behavior. 

Significantly more research is required before these nanobots are ready for primetime, but the team hopes to one day begin testing similar devices in humans. Before that, they need to determine the most effective magnetic fields and how long to apply them to patients. In the meantime, the overall design could also be applied to help treat regenerative issues in organs and wounds.

“The reproducible and scalable production of microrobots using our lab-on-a-chip system demonstrates that the platform’s application potential extends beyond basic research,” added Pané i Vidal.

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