Tiny drug capsules shine

German and Russian researchers have made a microcapsule that is able to communicate its progress in delivering drugs to biological tissue.

The microcapsule communicates via light waves. The key was finding nontoxic materials that emit infrared light at wavelengths that can easily be measured because they are not absorbed by water and biological tissue.

The researchers' prototype microcapsules include some that emit a single wavelength, or color, and others that emit several in the 750- to 1200-nanometer range. These could eventually be used to monitor combinations of drugs. Visible light ranges from 400-nanometer blue to 700-nanometer red.

They made the microcapsules by causing oppositely-charged layers of material to form a shell around carbonate particles 3.7 microns in diameter, which is a little smaller than red blood cell. The researchers added negatively charged light-emitting nanocrystals, which, attracted by positively-charged portions of the microcapsule, embedded in the shell. They dissolved the carbonate particles to leave hollow microcapsules.

The microcapsules could be ready for use in five years, according to the researchers, who are from the University of Hamburg and Max Planck Institute in Germany, and the Russian National Research Center for Antibiotics. The work appeared in the March 12, 2003 issue of Nano Letters.