Making Buckminster Fuller proud (or at least his namesake less deadly)
Rice finds 'on-off switch' for buckyball toxicity
While buckyballs show great promise in applications as diverse as fuel cells, batteries, pharmaceuticals and coatings, some scientists and activists have raised concerns about their potential toxicity to humans and animals.
CBEN's study is the first cytotoxicity study of human cells exposed to buckyballs. Cytotoxicity refers to toxic effects on individual cells. The study found that even minor alterations to the surface of the buckyballs can dramatically affect how toxic they are to individual cells, and the researchers identified specific alterations that render them much less toxic.
"There are many cases where toxicity is desirable," said Vicki Colvin, CBEN director, professor of chemistry and chemical engineering, and the principal investigator for the research. "For example, we might want particles that kill cancer cells or harmful bacteria. In other cases -- like applications where particles may make their way into the environment -- toxicity is undesirable."
In the study, the researchers exposed two types of human cells to various solutions containing different concentrations of buckyballs. Four types of solutions were tested. One contained tiny clusters of smooth-surfaced buckyballs. In the other three, researcher s modified the buckyballs by attaching other molecules to their sides. Researchers measured how many cells died within 48 hours of exposure to each solution, and they repeated the tests until they found the exposure level for each that resulted in a 50 percent mortality rate.
In general, the greater the degree of surface modification, the lower the toxicity. For example, the undecorated buckyballs showed the highest toxicity -- about 20 parts per billion-- while the least toxic proved to be buckyballs decorated with the largest number of hydroxyl side-groups. To achieve the equivalent level of toxicity as that of bare buckyballs, the researchers had to increase the concentration of these modified buckyballs by 10 million times to more than 5 million parts per billion.