Injected after accidents, nanoparticles could prevent paralysis

When a spinal cord injury occurs, sometimes it's the body's own immune system that causes the subsequent paralysis. In the not-too-distant future, however, it's possible that an injection of nanoparticles at the injury site may be able to rein in the well-meaning but destructive immune cells.

Ordinarily, when they travel to the location of an injury, immune cells help with the healing by clearing up debris and beginning the regenerative process. The delicate neural tissues of the central nervous system, however, can be damaged by the robust activity of these cells. Normally, those tissues are protected from the cells by a membrane known as the blood-brain barrier. In the event of a spinal cord injury, though, the barrier is breached and the immune cells get in.

When this happens, the resulting inflammation kills neurons, it destroys nerve cells' insulating myeline sheath that allows them to communicate effectively, and it produces scars that keep nerve cells from regenerating. In some cases, one or more of these factors produce paralysis below the injury site. That's where the new nanoparticles come in.

Being developed at the University of Michigan, they're made from a biodegradable polymer known as poly(lactide-coglycolide), and they contain no actual medication that could potentially cause side effects.

Instead, they bind with immune cells that are on their way to the injury, reprogramming them. This causes most of the cells to travel away from the injury, while those that continue on to it produce less inflammation than they would otherwise, plus their regenerative qualities are boosted.