ARLINGTON, Va., Sept. 11, 2002 -- A biomedical engineer and a biologist have teamed up to create nanomachines that zero in on breast cancer tissue in live mice.

The nanomachines, a combination of organic and inorganic materials, demonstrate how it might be possible to build simple robots that could travel through the bloodstream in search of disease at its earliest stages.

The researchers, whose work is being published this week in the Proceedings of the National Academy of Sciences, programmed tiny semiconductor crystals called quantum dots and wrapped them with protein fragments that zero in on specific targets in living tissue.

The experiments showed that these devices could be used inside the body without causing blood clotting and could be successfully directed to a specific type of cancer, in this case breast cancer.

"We are enthusiastic about these results," said Whitaker investigator Sangeeta Bhatia, M.D., Ph.D., associate professor of bioengineering at the University of California, San Diego.

Her laboratory developed the quantum dots while the protein fragments (peptides) were developed in the laboratory of Erkki Rouslahti, M.D., Ph.D., a biologist at the Burnham Institute in San Diego.

These nanomachines travel through the bloodstream, seeking out and attaching to cancer cells. Their accumulation at a site indicates the presence of disease. Since the quantum dots emit bright light of different colors, it is easy to track their location.

Quantum dots, which are about 10 nanometers in diameter, can be programmed to produce different colors. They are relatively stable and make a good platform for building more complex devices.

In the current study, quantum dots programmed to emit red or green light were coated with different peptides that targeted either normal lung tissue, blood vessels that feed tumors, or lymph modes that drain the malignancies. These three types of nanomachines were injected intravenously in live mice and successfully made their way to the desired targets.

Researchers have been working for years to take advantage of the properties of quantum dots for biological or therapeutic purposes. Gradually obstacles to their use are falling away.

The homing peptides developed by Ruoslahti are as small as nine amino acids, many times smaller than proteins such as antibodies, which have been widely investigated for targeting specific tissues but are too large to travel freely through a tumor.

The research was supported by the National Institutes of Health and other sources. Bhatia has also received support from The Whitaker Foundation for other research in biomedical engineering.

Contact:
Frank Blanchard