Surface of gold nanorods designed to deliver drugs

Ways to change the surface of gold nanorods to enable drug delivery and other functions are being studied by scientists at the Massachusetts Institute of Technology, Cambridge. Gold nanorods are tiny cylinders of gold, about 10 nm wide and 40 nm long. They differ from spherical gold nanoparticles in that they can absorb infrared light. That means they can theoretically be activated to deliver drugs or other materials by infrared lasers without damaging surrounding cells, which do not absorb infrared light.

However, scientists must first figure out how to deal with an organic molecule known as CTAB that coats the outer surface of gold nanorods and tends to detach from and reattach itself to the surface. The molecule, a byproduct of the synthesis reaction that produces the nanorods, makes it difficult to attach other molecules such as drugs or DNA.

Researchers found that a low concentration of the CTAB in the surrounding surface accelerates heat dissipation after the nanorod is hit with infrared light. When the concentration of CTAB is high, heat is dissipated more slowly. That information could help scientists design

nanorods that fight cancer agents by burning away tumor cells when activated with infrared light. “The surface chemistry is really key to everything,” says Prof. Kimberly Hamad-Schifferli.

For more information: Kimberly Hamad-Schifferli, Massachusetts Institute of Technology,

Cambridge, MA 02139; tel: 617/452-2385; schiffer@mit.edu; www.mit.edu.