These latest findings are part of ongoing work at Rice on nanoparticles and the environment. Describing this work at a recent conference, Vicki Colvin, Director of the Center for Biological and Environmental Nanotechnology (CBEN) at Rice and one of the authors of the study, says that finding ways to "modify and control biological effects by changing the particles" will help chemists to design safer nanotechnologies.

An earlier study at the center dealt with large carbon molecules, fullerenes (also called "buckyballs") that are known to damage cell membranes. By "stealing" electrons, unmodified fullerenes create free radicals that can cause a chain reaction, destroying molecules. The study found that modifying the surface of the buckyballs made them much less toxic.

Modifying buckyballs and nanotubes will not work for all applications, though. Altering the surface of a buckyball to make it safe also makes it less attractive for use in, for example, photovoltaics, where its ability to grab electrons is essential. On the other hand, the modified structures maintain other useful traits, perhaps including the ability to encapsulate a drug.

Likewise, modified carbon nanotubes may also lose functions, such as the ability to fluoresce, while retaining other possible uses, such as delivering imaging agents.

CBEN's goal, says chemist Kevin Ausman, Executive Director of the center and a co-author of the study, is to develop a "predictive feeling for which nanomaterials in which contexts are going to be dangerous and which ones are not."

To this end, researchers from several institutions organized by the D.C.-based Risk Science Institute last month published guidelines for screening nanomaterials, rules that should help to standardize experiments and allow researchers to incorporate data from different sites.

"This is a very exciting area," Ausman says, "But it's too big a problem for any one group to handle, so we welcome everybody to get into it."