Injectable nanorobots fused with stem cells have shown early promise in treating mice with spinal cord damage.
The tiny devices respond to electromagnetic signals and were designed to help nerve cells reconnect after severe spinal injury.
Researchers said the technology is still at an early stage and will need further testing before similar devices could be trialled in humans.
A team at ETH Zurich in Switzerland engineered microscopic machines that combine living neural progenitor cells with customised nanoparticles.
Neural progenitor cells are specialised stem cells developed for the spine.
The nanoparticles have two layers, with one responding to magnetic fields and the other converting those signals into electrical stimulation.
The aim is to support regeneration, the process by which damaged nerve cells or fibres regrow or reconnect.
Spinal cord damage is difficult to treat because scar tissue can block nerve fibre regrowth, while nerve cells often cannot repair themselves effectively.
Salvador Pané i Vidal, study co-author and roboticist at ETH Zurich, said: “We place a reservoir in the centre where we trap the cells.
“Then we inject the nanoparticles and wait for the two components to bind.”
Each nanorobot is around six micrometres wide, making it smaller than a red blood cell.
However, the researchers said millions of the devices were needed in animal trials.
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 showed improvements in movement, gait, coordination and exploratory behaviour.
The findings suggest the approach could eventually support spinal cord repair, but researchers said key questions still need to be answered.
They still need to determine the most effective magnetic fields and how long stimulation should be applied before similar devices could be tested in humans.
The team said the same design could also have potential in other areas of regenerative medicine, including organ and wound repair.
Pané i Vidal added: “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.”
