Controlled clusters could be key to safer nanoparticles

Controlled clusters could be key to safer nanoparticles

A team of researchers at the National Institute of Standards and Technology (www.nist.gov
) has introduced a breakthrough method for controlling the size of engineered nanoparticle clusters. The team discovered that nanoparticles have a tendency to clump when placed in a cell culture medium. Using this technique, the researchers found a way to pause cluster growth and that the nanoparticles will remain stable long enough to study the toxicity effects of the nanoparticles on human cells [1], addressing the concern that nanoparticles will have a long-term impact on environmental health and safety (EHS) when used in medical and biological research.

Transmission electron micrograph of gold nanoparticles clustering in solution. The distance between the two red arrows is approximately 280 nanometers, some 200 times smaller than the diameter of a human hair. The individual nanoparticles are approximately 15 nm in diameter, about the distance across 40 side-by-side sodium atoms. (Courtesy: A. Keene, U.S. Food and Drug Administration.)

The NIST team tested nanoparticle samples made of gold, silver, cerium oxide, and positively-charged polystyrene by suspending them, separately, in the cell culture medium until clumping occurred in each. The clumping was ceased with the addition of a protein in this case, bovine serum albium (BSA). The researchers found that the longer the nanoparticles were allowed to clump together, the larger the size of the resulting cluster. They also found that ceasing cluster growth at the same time in all samples yielded consistent sizes in all four types. The BSA-controlled dispersions remained stable for up to three days, which is ample time for toxicity studies.

The NIST team plans to continue testing on different cluster sizes and apply the results to study the impact on cytotoxicity of coatings (such as polymers) on nanoparticles. For more information, visit www.nist.gov,
call Michael E. Newman at 301-975-3025, or e-mail michael.newman@nist.gov.

Christina D’Airo

1. J.M. Zook, R.I. MacCuspie, L.E. Locascio, M.D. Halter, and J.T. Elliott, “Stable nanoparticle aggregates/agglomerates of different sizes and the effect of their size on hemolytic cytotoxicity,: Nanotoxicology , published online Dec. 13, 2010 (DOI:10.3109/17435390.2010.536615).