The researchers also tested the NPCbots on mice with completely severed spinal cords. Here, too, the results were very promising: after 28 days, the animals’ nerve cells had reconnected at the site of the injury. During this period, the treated mice exhibited increasingly normal movement patterns – their gait, stride length, coordination and exploratory behaviour improved significantly.
This result is particularly significant because, unlike in zebrafish, the mouse spinal cord does not normally regenerate. The treatment was well tolerated by the animals, with no evidence of any adverse effects or immune reactions.
Success through minimally invasive stimulation
These successes were made possible through electrical stimulation of stem cells, greatly enhancing their differentiation after transplantation. In this process, nanoparticles convert magnetic signals directly into electrical impulses that stimulate specific stem cells. When employing NPCbots, researchers need only apply external magnetic fields around the injury site, eliminating the need for implanted electrodes or cables in previous approaches. This is crucial because the spinal cord is extremely sensitive. “Microrobotic guidance makes the treatment more precise and minimally invasive,” Hao explains.
Magnetic fields are particularly well-suited for stimulating stem cells because they can penetrate tissue easily, and their frequency and field strength can be flexibly adjusted to the specific application. Once the progenitor cells have been stimulated and differentiated into nerve cells, the NPCbots essentially dissolve within the tissue. The researchers expect the nanoparticles to be stable and minimally reactive due to their barium titanate coating. Further studies will determine whether and how the particles are degraded or excreted over the long term.
The idea can be expanded as required
The results from animal experiments are extremely promising, but further research will be needed before NPCbots can be tested in humans. “In addition to many clinical aspects, we first need to test which magnetic fields work best in humans and determine the optimal stimulation duration,” Hao explains. Nevertheless, the researchers are already considering further applications: “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,” explains Professor Pané i Vidal. It could also be adapted for other biomedical applications – for example, in cardiology, oncology, wound healing and other targeted regenerative therapies. This could make these treatments safer, more controllable and more effective.