Buckyballs made safer for humans * NewScientist.com news service * Katharine Davis   Carbon molecules called “buckyballs” - which hold great promise for nanotechnology - but have been shown to harm fish have been made safer by scientists. The soccer-ball-shaped carbon nanoparticles were shown to cause brain damage in fish and kill water fleas in a study in March 2004. But now a team at Rice University in Houston, Texas, US, has come close to understanding how buckyballs – more formally known as fullerenes - kill cells and how their toxicity can be lowered in human cells. Although the toxic nature of the carbon-60 nanoparticles may be useful in medicine, for example in fighting cancer, there are concerns that their potentially widespread use in fuel cells, drug delivery and cosmetics could mean they find their way into the environment, and so into animals and humans. “There are a couple of different manufacturers that will, and are, mass producing fullerenes,” says Christie Sayes, one of the team. “They could make it into consumer based products: fuel cells and batteries or make-up,” she says. Ruptured cells The team, led by Vicki Colvin, looked at the effects of buckyballs on human cells. They found that even at quite low concentrations in water the buckyballs killed human skin cells. However, when they attached chemical groups such as hydroxyl groups to the buckyballs, their toxicity was greatly reduced. The higher the number of groups that were attached, the less toxic the fullerenes became, so that a buckyball with 24 hydroxyl groups attached showed a toxicity seven orders of magnitude lower than the original buckyball. The researchers believe the buckyball is toxic because in water it leads to the formation of an oxygen free radical which reacts with lipid molecules forming the cell membrane surrounding a cell. This causes the lipid molecules in turn to become free radicals – and when these try to interact with the water outside the cell, the membrane ruptures leading to cell death. Health threat The team were able to show the hole in the membrane using dyes that only fluoresce when in the cell. Dyes that are usually too big to enter a cell fluoresced after the buckyballs had been added, showing the permeability of the cell had increased to such an extent that even large molecules could move freely through the membrane. More research is needed to determine whether the same result would be seen in the body, says Sayes. “Cells in culture act differently to those in the body,” she says. The research could eventually be use to make buckyballs safer, so that they do not cause an environmental or health threat as they become more commonly used. Or even to make them more toxic for certain medical treatments. Eva Oberdõrster at Southern Methodist University in Dallas, Texas, who led the buckyball study in fish, called the new work “an excellent first step” in reducing the toxicity of buckyballs. Journal reference: Nano Letters (in press)

Uploaded: 12-14-05