Could nanomachines be tomorrow's doctors?

HELEN R. PILCHER

DNA strands can sense abnormal RNA that can indicate some types of cancer. Source: Nature

Scientists have built a tiny biological computer that might be able to diagnose and treat certain types of cancer. The device, which only works in a test-tube, is years from clinical application. But researchers hope it will be the precursor of future 'smart drugs' that roam the body, fixing disease on the spot.

Instead of silicon chips and electrical circuits, the miniscule machine is made of DNA. And rather than being controlled by electrical signals, it senses changes in its environment and responds by releasing biological molecules.

The biocomputer senses messenger RNA, the DNA-like molecule that helps create proteins from the information in genes. In particular, it can detect the abnormal messenger RNAs produced by genes involved in certain types of lung and prostate cancer.

When the computer senses one of these RNAs it releases an anticancer drug, also made of DNA, which damps expression of the tumour-related gene, researchers report in Nature¹.

Billions of the computers can be packed into a single drop of water, so they could easily fit inside a human cell. "It is decades off, but future generations of DNA computers could function as doctors inside cells," says Ehud Shapiro from the Weizmann Institute of Science, Israel, who led the research. The idea is they could diagnose disease from within cells and dispense drugs as necessary.

Fantastic voyage

"It is a little early to start thinking about applications," cautions DNA computer expert Lloyd Smith from the University of Wisconsin, Madison. "But it is an important conceptual leap." DNA computers are not new but this is the first in which both input and output are biological, which means it can be hooked up to living systems.

So far, the computer only works in the confines of a finely balanced salt solution, and there are many hurdles to overcome before it can be applied to real disease. It is necessary to ensure that the computers will survive inside a biological setting, will not provoke an immune response and will be safe to use, says Shapiro.

They would also need to be far more complex than the prototype, which recognizes only messenger RNAs related to cancer. And they would need to deliver a wide variety of drugs, not just DNA therapies. They would need to be tested in cell suspensions, tissue cultures, simple organisms, mammals and finally humans.

But if such hurdles could be overcome, then "it could be the killer application for DNA computing", says Smith. The idea is not a million miles from the 1966 film Fantastic Voyage, where a surgical team is miniaturized and inserted into a dying man.

Research like this is the interface between real science and "off the wall" science fiction, says Smith. "It is where science fiction is driving technology."

1. Benenson, Y., Gil, B., Ben-Dor, U., Adar, R. & Shapiro, E. Nature, published online, doi:10.1038/nature02551 (2004). |Article|

© Nature News Service / Macmillan Magazines Ltd 2004