Polymer, buckyballs combat nerve damage.

By marrying materials science and medicine, researchers have found two possible ways of combating nerve damage caused by injury, stroke, and neurodegenerative diseases. Two new reports suggest that a polymer that conducts electricity could help damaged nerves grow back and that chemically modified buckyballs--60-carbon spherical molecules--could prevent the nerves from degenerating.

Scientists at the Massachusetts Institute of Technology and at Harvard University's Children's Hospital in Boston have demonstrated that nerve cells will grow on oxidized polypyrrole films made to carry a negative charge. Neurons adhere well to this polymer, says study coauthor Venkatram R. Shastri of MIT, perhaps in part because the negative surface charge attracts positively charged proteins on the nerve cells.

The researchers spread rat neurons onto polymer films and bathed the samples in nerve growth factor, a protein that helps maintain the cells. "When we apply an electrical stimulus, we can double the length of the [nerve fibers] and increase their number," Shastri says.

Scientists don't know why electricity helps neurons to elongate, says Robert F. Valentini of Brown University in Providence, R.I., although it appears to play a role in the growth of many tissues, including bone and muscle. The conductive polymer provides an opportunity to test "a whole variety of charge patterns." Growth may differ with higher and lower currents and different stimulation frequencies, he notes.

The researchers envision using the polypyrrole to form an "interactive conduit" that would both stimulate regeneration of a cut nerve and guide its growth, thus reestablishing a connection, Shastri says (SN: 7/27/96, p. 52).

Meanwhile, a group of researchers from Washington University in St. Louis and National Taiwan University in Taipei has focused on preventing injured nerves from degenerating. Their study shows that modified buckyballs can protect nerves from damaging molecules called free radicals. Both studies appear in the Aug. 19 Proceedings of the National Academy of Sciences.

After trauma or stroke, free radicals seem to attack nerves and trigger their death, says study coauthor Laura L. Dugan of Washington University. Previous work has shown that a single buckyball can mop up more than 30 free radicals, whereas one molecule of a typical antioxidant such as vitamin C neutralizes just one free radical.

To make buckyballs soluble in water, and thus suitable for biological uses, the researchers added carboxylic acid groups to the outside of the molecules. In the test tube, Dugan says, these compounds seem to protect cells from various types of induced damage.

In mice that carry a gene for human amyotrophic lateral sclerosis, the neurodegenerative condition commonly known as Lou Gehrig's disease, the modified buckyballs delayed the onset of paralysis for 10 days--a 15 percent increase in symptom-free life. The buckyballs also extended the life of the mice by about 8 days, a better outcome than another research team obtained with the antioxidant vitamin E in a similar study last year, Dugan says.

One form of the compound, with the acid groups concentrated on one hemisphere of the buckyball, worked better than a version with the groups attached along the equator. The improvement may arise from an enhancement of the buckyballs' ability to slip through cell membranes, the researchers suspect.

Both groups are continuing their tests in hopes of turning these preliminary successes into real-life treatments.