"We have developed a novel approach that blocks the spread of injury to spinal cord after an accident by using nanosized copolymer micelles 60 nm in diameter that repair damaged neuronal membranes," team member Yunzhou Shi told nanotechweb.org. "We are very excited about the results we obtained."

Spinal cord injury ruptures neuronal membranes. Widespread secondary neurodegenerative processes can then kill nerve cells, ultimately leading to permanent damage and paralysis.

The best way to treat the injury is to seal the damaged membranes as early as possible. Today, doctors do this by administering a high-dose infusion of methylprednisolone that begins within eight hours after the accident. However, this treatment can lead to serious complications.

Copolymer micelles
The micelles used by Shi and colleagues are made of copolymers – non-toxic, according to the researchers – that have hydrophilic and hydrophobic ends. The copolymers (PEG-PDLLA) can circulate in the bloodstream for several hours and reach the injured site in spinal cord by travelling through leaky blood vessels.

Although they are not entirely sure how the micelles help repair damaged spinal cord tissue, the researchers believe that the hydrophobic end of the polymer inserts into the cell membrane and increases its fluidity. This could help membrane breaches to reseal.

The Purdue team tested its technique on injured spinal cord strips taken from adult guinea pigs, a tissue model widely used in neuronal membrane repair studies.

The method might even be extended to other areas of the body, such as injured brain tissue, cardiac muscle and other muscle cells, says Shi.

"Our ultimate goal is to use our micelles in hospital emergency rooms," she added. "Before we can do this, we need to study a larger pool of animals to determine how dosage, administration frequency and timing of micelle treatment affect clinical outcome. We will work hard to push this study to clinical trials, but this may take a few years."

The work was reported in Nature Nanotechnology.