Injecting tiny polymer spheres into rats right after a spinal cord injury helped the animals recover movement and prevented secondary nerve damage that often follows such injuries, U.S. researchers said on Sunday.

The experimental treatment uses spheres called copolymer micelles that fuse with injured nerve fibers and prevent inflammation from doing more damage to surrounding nerves.

What we did here was we invented a method to treat the spinal injury at the early stage, said Ji-Xin Cheng of Purdue University in Indiana, whose study appears in the journal Nature Nanomedicine.

Copolymer micelles, roughly 100 times smaller than the diameter of a red blood cell, have been used in research for three decades as a drug-delivery vehicle.

In our case, it's a very new use of these structures. We are not using them as a drug carrier. We use them as a membrane repair agent, Cheng said.

The treatment takes advantage of the chemical properties of the micelles themselves to help seal damaged membranes and prevent more damage. Micelles are made of two different polymers, a hydrophobic polymer core that resists being dissolved and a hydrophilic outer layer that loves being wet.

When the spheres are injected into the bloodstream, they make their way to the injury site and the wet-loving polymer embeds itself into the damaged membrane, patching up the injury site. The core keeps the patch stable.

We believe they can penetrate the membrane and fuse the membrane, Cheng said.

Studies in rats using dyed micelles showed the nanoparticles successfully migrated to the injury sites.

Animals treated with the spheres shortly after spine injuries regained control of all four limbs, while other animals did not. Toxicity tests suggested the treatment is safe.

Cheng said future studies will try to establish how soon after injury the treatment needs to be given to do the most good. We want to decide if we treat the animals three hours after the injury what the result will be, he said.

Eventually, the team hopes to give the spheres to people in the emergency room to see if it will protect surrounding nerves from additional damage.

Medicine