Spinal-cord injuries are “notoriously difficult to treat,” said Rhys Blakely, science editor of The Times. But Zurich-based researchers think a solution may be in sight: injectable microrobots.
When the spinal-cord is damaged, recovery is often limited: nerve-fibre regrowth can be hampered by scarring, and the nerve cells usually cannot regenerate on their own. But studies by a team at the Multi-Scale Robotics Lab at ETH Zurich suggest that microrobots, made from stem cells with magnetic nano-particles, could “coax” these nerve cells to repair and regenerate.
The studies were carried out in a lab on zebrafish and mice, so there is “still a long way to go” before the microrobots can be tested on humans. But the results are promising, and scientists the world over are intrigued by the idea of “microscopic repair crews, guided by magnets”.
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‘Near-complete recovery’
The decision to build this “fleet of living machines” came after other experimental treatments had fallen short, said Blakely. Attempts to inject immature nerve cells into the injured area, then implant electrodes to stimulate them to develop, had failed.
So the Zurich robotics team engineered microscopic machines about six micrometers wide – smaller than a red blood cell. Each one combines a neural progenitor cell (a spinal stem cell) with a cluster of customised nanoparticles. These nanoparticles have two layers: one is sensitive to magnetic fields, so the microrobot can be guided by a magnet; the other turns magnetic signals into electrical pulses. This “lets scientists steer the cells and then coax them, electrically, into maturing into new nerve tissue”.
Millions of these microrobots were needed during the animal trials. First, they were injected into injured zebrafish larvae and, in three days, the larvae were exhibiting “near-complete recovery of swimming and exploratory behaviours”, according to the study published in Nature Materials. Then, when tested on mice with severed spinal cords, the microrobots “promoted neural differentiation, and resulted in substantial improvements in motor function within four weeks”.
‘Reproducible and scalable’
Further research is needed before these microrobots can be tested on humans but the Zurich team is already thinking about ways they can be used in other medical settings. “The reproducible and scalable production of microrobots using our lab-on-a-chip system demonstrates” that there is a great deal of “application potential”, said study leader Salvador Pané i Vidal. With adaptations, the microrobots could be used in wound healing, and to make cardiology and oncology treatments “safer, more controllable and more effective”.
Different microrobots have already been shown to be successful in other areas of medicine, said Healthcare in Europe. Formed in droplets, they are effective at “precision-targeted drug delivery”, outperforming IV-delivery on the amount of drug than reaches the target tissue.
