Deliver Treatment for Spinal Cord Injuries

Richard Borgen’s group of the School of Veterinary Medicine's Center for Paralysis Research and Welden School of Biomedical Engineering had previously shown benefits of the polymer polyethylene glycol, or PEG, to treat rats with brain injuries and dogs with spinal cord injuries. PEG specifically targets damaged cells and seals the injured area, reducing further damage. It also helps restore cell function, Borgens said.

In previous studies, PEG was mixed with saline and injected. "Composition and concentration limited how much PEG we could get to the injury," he said. "If you change the composition to make the PEG more potent, it produces ethylene glycol, the poison in antifreeze. If you change the concentration of PEG in another way, the solution becomes syrupy and difficult to inject."

So the team turned to silica nanoparticles. "These particles are so tiny they can't be seen with a regular microscope. They are about the size of a large virus. So you can inject as many as you need. And they are safe inside bodies," Borgens said.

In the first study, the researchers coated the nanoparticles with PEG to treat guinea pig spinal cord injuries. The treated spinal cord cells showed improved physiological functioning. In the second study, the researchers added both PEG and hydralazine, an antihypertension drug, to mesoporous silica nanoparticles. These nanoparticles have pores that can hold the drug, which is later delivered to the damaged cells. The hydralazine was added to fight off secondary damage to cells that occurs after the initial injury.

"When cells are injured, they produce natural toxins," Borgens said. "Acrolein is the most poisonous of these toxins. It's an industrial hazard for which hydralazine is an antidote." Borgens and his team introduced acrolein into cells and then treated the cells with different combinations of hydralazine and/or PEG delivered by the mesoporous silica nanoparticles. They found that the treatment restored disrupted cell function caused by acrolein.

The team concluded that the use of nanoparticles to deliver both PEG and hydralazine increased the effectiveness of earlier PEG-only treatment by controlling and concentrating release of the drug and the polymer, producing a dual treatment and prolonging the treatment's duration. The goal of Borgens' research is to improve the quality of life of those who have suffered head or spinal cord injuries.; Source: Purdue University